Systems and methods to operate hydraulic fracturing units using automatic flow rate and/or pressure control

Abstract

Systems and methods for operating hydraulic fracturing units to pump fracturing fluid into a wellhead may include receiving a target flow rate and/or a target pressure for fracturing fluid supplied to the wellhead. The systems and methods may increase a flow rate from the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the target flow rate and/or target pressure. When it has been determined the target flow rate and/or target pressure has been achieved, the systems and methods also may include operating the hydraulic fracturing units to maintain the target flow rate and/or target pressure. When the target flow rate has not been achieved, the systems and methods also may include generating notification signals, and/or when the target pressure has not been achieved, the systems and methods further may include operating the hydraulic fracturing units to maintain a maximum flow rate.

Description

TECHNICAL FIELD

The present disclosure relates to systems and methods for operating hydraulic fracturing units and, more particularly, to systems and methods for operating hydraulic fracturing units to pump fracturing fluid into a wellhead.

BACKGROUND

Hydraulic fracturing is an oilfield operation that stimulates production of hydrocarbons, such that the hydrocarbons may more easily or readily flow from a subsurface formation to a well. For example, a hydraulic fracturing system may be configured to fracture a formation by pumping a fracturing fluid into a well at high pressure and high flow rates. Some fracturing fluids may take the form of a slurry including water, proppants, and/or other additives, such as thickening agents and/or gels. The slurry may be forced via one or more pumps into the formation at rates faster than can be accepted by the existing pores, fractures, faults, or other spaces within the formation. As a result, pressure builds rapidly to the point where the formation may fail and may begin to fracture. By continuing to pump the fracturing fluid into the formation, existing fractures in the formation are caused to expand and extend in directions farther away from a well bore, thereby creating additional flow paths to the well bore. The proppants may serve to prevent the expanded fractures from closing or may reduce the extent to which the expanded fractures contract when pumping of the fracturing fluid is ceased. Once the formation is fractured, large quantities of the injected fracturing fluid are allowed to flow out of the well, and the production stream of hydrocarbons may be obtained from the formation.

Prime movers may be used to supply power to hydraulic fracturing pumps for pumping the fracturing fluid into the formation. For example, a plurality of gas turbine engines and/or reciprocating-piston engines may each be mechanically connected to a corresponding hydraulic fracturing pump via a transmission and operated to drive the hydraulic fracturing pump. The prime mover, hydraulic fracturing pump, transmission, and auxiliary components associated with the prime mover, hydraulic fracturing pump, and transmission may be connected to a common platform or trailer for transportation and set-up as a hydraulic fracturing unit at the site of a fracturing operation, which may include up to a dozen or more of such hydraulic fracturing units operating together to perform the fracturing operation.

Partly due to the large number of components of a hydraulic fracturing system, it may be difficult to efficiently and effectively control the output of the numerous hydraulic fracturing units and related components. For example, during a fracturing operation, it may be necessary to reduce the output of one or more of the hydraulic fracturing pumps in a coordinated manner, for example, when unexpected well screen out or over-pressure conditions occur while conducting the fracturing operation. During such occurrences, as well as others, it may be necessary to promptly adjust the outputs of the numerous hydraulic fracturing pumps to reduce the likelihood of equipment damage, which can lead to expensive repairs and excessive down time. In addition, during the start-up of a fracturing operation, as the hydraulic fracturing units increase the output of fracturing fluid, it may be desirable to control the rate at which the outputs of the respective hydraulic fracturing unit increases, for example, to prevent damage to the hydraulic fracturing pumps due to uncontrolled over-speed events. Due to the numerous hydraulic fracturing units, this may be difficult and complex. As a fracturing operation is completed, it may be desirable to control the rate at which the hydraulic fracturing units decrease their respective outputs. Due to the numerous hydraulic fracturing units, this may be difficult and complex to execute efficiently and effectively.

Accordingly, Applicant has recognized a need for systems and methods that provide improved operation of hydraulic fracturing units during hydraulic fracturing operations. The present disclosure may address one or more of the above-referenced drawbacks, as well as other possible drawbacks.

SUMMARY

As referenced above, due to the complexity of a hydraulic fracturing operation and the high number of machines involved, it may be difficult to efficiently and effectively control the output of the numerous hydraulic fracturing units and related components to perform the hydraulic fracturing operation. In addition, manual control of the hydraulic fracturing units by an operator may result in delayed or ineffective responses to problems that may occur during the hydraulic fracturing operation, such as well screen out and over-pressure events, and over speeding of the hydraulic fracturing pumps as the hydraulic fracturing units come up to operating speed. Insufficiently prompt responses to such events may lead to premature equipment wear or damage, which may reduce efficiency and lead to delays in completion of a hydraulic fracturing operation.

The present disclosure generally is directed to systems and methods for operating hydraulic fracturing units to pump fracturing fluid into a wellhead. For example, in some embodiments, the systems and methods may provide semi- or fully-autonomous operation of a plurality of hydraulic fracturing units, for example, during start-up, operation, and/or completion of operation of the plurality of hydraulic fracturing units following a hydraulic fracturing operation.

According to some embodiments, a method of operating a plurality of hydraulic fracturing units, each of the hydraulic fracturing units including a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump, may include receiving, via a supervisory controller, one or more operational parameters associated with pumping fracturing fluid into a wellhead. The one or more operational parameters may include one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead. The method also may include determining, via the supervisory controller, whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressure. The method further may include initiating operation of at least some of the plurality of hydraulic fracturing units, and increasing a flow rate from the at least some of the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the one or more of the target flow rate or the target pressure. The method further still may include determining whether the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure. When it has been determined that the one or more of the target flow rate or the target pressure has been achieved, the method also may include operating the at least some hydraulic fracturing units to maintain one or more of the target flow rate or the target pressure. When it has been determined that the target flow rate has not been achieved, the method also may include generating one or more signals indicative of a failure to achieve the target flow rate. When it has been determined that the target pressure has not been achieved, the method further may include operating the at least some hydraulic fracturing units to maintain a maximum flow rate.

According some embodiments, a hydraulic fracturing control assembly to operate a plurality of hydraulic fracturing units, each of the hydraulic fracturing units including a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump, may include an input device configured to facilitate communication of operational parameters to a supervisory controller. The one or more operational parameters may include one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead. The hydraulic fracturing assembly further may include one or more sensors configured to generate one or more sensor signals indicative of one or more of a flow rate of fracturing fluid or a pressure associated with fracturing fluid. The hydraulic fracturing control assembly may further still include a supervisory controller in communication with one or more of the plurality of hydraulic fracturing units, the input device, or the one or more sensors. The supervisory controller may be configured to receive one or more operational parameters associated with pumping fracturing fluid into a wellhead. The one or more operational parameters may include one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead. The supervisory controller also may be configured to determine whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressure. The supervisory controller further may be configured to increase a flow rate from at least some of the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the one or more of the target flow rate or the target pressure. The supervisory controller still further may be configured to determine, based at least in part on the one or more sensor signals indicative of one or more of the flow rate of fracturing fluid or the pressure associated with fracturing fluid, whether the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure. When it has been determined that the one or more of the target flow rate or the target pressure has been achieved, the supervisory controller may be configured to operate the at least some hydraulic fracturing units to maintain one or more of the target flow rate or the target pressure. When it has been determined that the target flow rate has not been achieved, the supervisory controller may be configured to generate one or more signals indicative of a failure to achieve the target flow rate. When it has been determined that the target pressure has not been achieved, the supervisory controller may be configured to operate the at least some hydraulic fracturing units to maintain a maximum flow rate.

According to some embodiments, a hydraulic fracturing system may include a plurality of hydraulic fracturing units. Each of the hydraulic fracturing units may include a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump. The hydraulic fracturing system also may include an input device configured to facilitate communication of operational parameters to a supervisory controller. The one or more operational parameters may include one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead. The hydraulic fracturing system further may include one or more sensors configured to generate one or more sensor signals indicative of one or more of a flow rate of fracturing fluid or a pressure associated with fracturing fluid. The hydraulic fracturing system still further may include a supervisory controller in communication with one or more of the plurality of hydraulic fracturing units, the input device, or the one or more sensors. The supervisory controller may be configured to receive one or more operational parameters associated with pumping fracturing fluid into a wellhead. The one or more operational parameters may include one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead. The supervisory controller also may be configured to determine whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressure. The supervisory controller further may be configured to increase a flow rate from at least some of the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the one or more of the target flow rate or the target pressure. The supervisory controller still further may be configured to determine, based at least in part on the one or more sensor signals indicative of one or more of the flow rate of fracturing fluid or the pressure associated with fracturing fluid, whether the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure. When it has been determined that the one or more of the target flow rate or the target pressure has been achieved, the supervisory controller may be configured to operate the at least some hydraulic fracturing units to maintain one or more of the target flow rate or the target pressure. When it has been determined that the target flow rate has not been achieved, the supervisory controller may be configured to generate one or more signals indicative of a failure to achieve the target flow rate. When it has been determined that the target pressure has not been achieved, the supervisory controller may be configured to operate the at least some hydraulic fracturing units to maintain a maximum flow rate.

Still other aspects and advantages of these exemplary embodiments and other embodiments, are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Accordingly, these and other objects, along with advantages and features of the present invention herein disclosed, will become apparent through reference to the following description and the accompanying drawings. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the embodiments of the present disclosure, are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure, and together with the detailed description, serve to explain principles of the embodiments discussed herein. No attempt is made to show structural details of this disclosure in more detail than can be necessary for a fundamental understanding of the embodiments discussed herein and the various ways in which they can be practiced. According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings can be expanded or reduced to more clearly illustrate embodiments of the disclosure.

FIG. 1 schematically illustrates an example hydraulic fracturing system including a plurality of hydraulic fracturing units, and including a block diagram of a hydraulic fracturing control assembly according to embodiments of the disclosure.

FIG. 2 is a block diagram of an example hydraulic fracturing control assembly according to an embodiment of the disclosure.

FIG. 3A is a block diagram of an example method of operating a plurality of hydraulic fracturing units according to an embodiment of the disclosure.

FIG. 3B is a continuation of the example method of operating a plurality of hydraulic fracturing units of the block diagram of FIG. 3A according to an embodiment of the disclosure.

FIG. 4A is a block diagram of another example method of operating a plurality of hydraulic fracturing units according to an embodiment of the disclosure.

FIG. 4B is a continuation of the example method of operating a plurality of hydraulic fracturing units of the block diagram of FIG. 4A according to an embodiment of the disclosure.

FIG. 4C is a continuation of the example method of operating a plurality of hydraulic fracturing units of the block diagram of FIGS. 4A and 4B according to an embodiment of the disclosure.

FIG. 5 is a schematic diagram of an example supervisory controller configured to operate a plurality of hydraulic fracturing units according to embodiments of the disclosure.

DETAILED DESCRIPTION

The drawings like numerals to indicate like parts throughout the several views, the following description is provided as an enabling teaching of exemplary embodiments, and those skilled in the relevant art will recognize that many changes may be made to the embodiments described. It also will be apparent that some of the desired benefits of the embodiments described can be obtained by selecting some of the features of the embodiments without utilizing other features. Accordingly, those skilled in the art will recognize that many modifications and adaptations to the embodiments described are possible and may even be desirable in certain circumstances. Thus, the following description is provided as illustrative of the principles of the embodiments and not in limitation thereof.

The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the term “plurality” refers to two or more items or components. The terms “comprising,” “including,” “carrying,” “having,” “containing,” and “involving,” whether in the written description or the claims and the like, are open-ended terms, i.e., to mean “including but not limited to,” unless otherwise stated. Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. The transitional phrases “consisting of” and “consisting essentially of,” are closed or semi-closed transitional phrases, respectively, with respect to any claims. Use of ordinal terms such as “first,” “second,” “third,” and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish claim elements.

FIG. 1 schematically illustrates a top view of an example hydraulic fracturing system 10 including a plurality of hydraulic fracturing units 12, and including a block diagram of a hydraulic fracturing control assembly 14 according to embodiments of the disclosure. In some embodiments, one or more of the hydraulic fracturing units 12 may include a hydraulic fracturing pump 16 driven by an internal combustion engine 18, such a gas turbine engine or a reciprocating-piston engine. For example, in some embodiments, each of the hydraulic fracturing units 12 may include a directly-driven turbine (DDT) hydraulic fracturing pump 16, in which the hydraulic fracturing pump 16 is connected to one or more GTEs that supply power to the respective hydraulic fracturing pump 16 for supplying fracturing fluid at high pressure and high flow rates to a formation. For example, the GTE may be connected to a respective hydraulic fracturing pump 16 via a transmission 20 (e.g., a reduction transmission) connected to a drive shaft, which, in turn, is connected to a driveshaft or input flange of a respective hydraulic fracturing pump 16, which may be a reciprocating hydraulic fracturing pump. Other types of engine-to-pump arrangements are contemplated.

In some embodiments, one or more of the GTEs may be a dual-fuel or bi-fuel GTE, for example, capable of being operated using of two or more different types of fuel, such as natural gas and diesel fuel, although other types of fuel are contemplated. For example, a dual-fuel or bi-fuel GTE may be capable of being operated using a first type of fuel, a second type of fuel, and/or a combination of the first type of fuel and the second type of fuel. For example, the fuel may include gaseous fuels, such as, for example, compressed natural gas (CNG), natural gas, field gas, pipeline gas, methane, propane, butane, and/or liquid fuels, such as, for example, diesel fuel (e.g., #2 diesel), bio-diesel fuel, bio-fuel, alcohol, gasoline, gasohol, aviation fuel, and other fuels as will be understood by those skilled in the art. Gaseous fuels may be supplied by CNG bulk vessels, a gas compressor, a liquid natural gas vaporizer, line gas, and/or well-gas produced natural gas. Other types and associated fuel supply sources are contemplated. The one or more internal combustion engines 18 may be operated to provide horsepower to drive the transmission 20 connected to one or more of the hydraulic fracturing pumps 16 to safely and successfully fracture a formation during a well stimulation project or fracturing operation.

In some embodiments, the fracturing fluid may include, for example, water, proppants, and/or other additives, such as thickening agents and/or gels. For example, proppants may include grains of sand, ceramic beads or spheres, shells, and/or other particulates, and may be added to the fracking fluid, along with gelling agents to create a slurry as will be understood by those skilled in the art. The slurry may be forced via the hydraulic fracturing pumps 16 into the formation at rates faster than can be accepted by the existing pores, fractures, faults, or other spaces within the formation. As a result, pressure builds rapidly to the point where the formation fails and begins to fracture. By continuing to pump the fracturing fluid into the formation, existing fractures in the formation are caused to expand and extend in directions farther away from a well bore, thereby creating additional flow paths to the well. The proppants may serve to prevent the expanded fractures from closing or may reduce the extent to which the expanded fractures contract when pumping of the fracturing fluid is ceased. Once the well is fractured, large quantities of the injected fracturing fluid may be allowed to flow out of the well, and the water and any proppants not remaining in the expanded fractures may be separated from hydrocarbons produced by the well to protect downstream equipment from damage and corrosion. In some instances, the production stream may be processed to neutralize corrosive agents in the production stream resulting from the fracturing process.

In the example shown in FIG. 1, the hydraulic fracturing system 10 may include one or more water tanks 22 for supplying water for fracturing fluid, one or more chemical additive units 24 for supplying gels or agents for adding to the fracturing fluid, and one or more proppant tanks 26 (e.g., sand tanks) for supplying proppants for the fracturing fluid. The example fracturing system 10 shown also includes a hydration unit 28 for mixing water from the water tanks 22 and gels and/or agents from the chemical additive units 24 to form a mixture, for example, gelled water. The example shown also includes a blender 30, which receives the mixture from the hydration unit 28 and proppants via conveyers 32 from the proppant tanks 26. The blender 30 may mix the mixture and the proppants into a slurry to serve as fracturing fluid for the hydraulic fracturing system 10. Once combined, the slurry may be discharged through low-pressure hoses 34, which convey the slurry into two or more low-pressure lines 36 in a frac manifold 38. In the example shown, the low-pressure lines 36 in the frac manifold 38 feed the slurry to the hydraulic fracturing pumps 16 through low-pressure suction hoses 40.

The hydraulic fracturing pumps 16, driven by the respective internal combustion engines 18, discharge the slurry (e.g., the fracking fluid including the water, agents, gels, and/or proppants) at high flow rates and/or high pressures through individual high-pressure discharge lines 42 into two or more high-pressure flow lines 44, sometimes referred to as “missiles,” on the frac manifold 38. The flow from the high-pressure flow lines 44 is combined at the frac manifold 38, and one or more of the high-pressure flow lines 44 provide fluid flow to a manifold assembly 46, sometimes referred to as a “goat head.” The manifold assembly 46 delivers the slurry into a wellhead manifold 48. The wellhead manifold 48 may be configured to selectively divert the slurry to, for example, one or more wellheads 50 via operation of one or more valves. Once the fracturing process is ceased or completed, flow returning from the fractured formation discharges into a flowback manifold, and the returned flow may be collected in one or more flowback tanks as will be understood by those skilled in the art.

As schematically depicted in FIG. 1, one or more of the components of the fracturing system 10 may be configured to be portable, so that the hydraulic fracturing system 10 may be transported to a well site, quickly assembled, operated for a relatively short period of time, at least partially disassembled, and transported to another location of another well site for use. For example, the components may be carried by trailers and/or incorporated into trucks, so that they may be easily transported between well sites.

As shown in FIG. 1, some embodiments of the hydraulic fracturing system 10 may include one or more electrical power sources 52 configured to supply electrical power for operation of electrically powered components of the hydraulic fracturing system 10. For example, one or more of the electrical power sources 52 may include an internal combustion engine 54 (e.g., a GTE or a reciprocating-piston engine) provided with a source of fuel (e.g., gaseous fuel and/or liquid fuel) and configured to drive a respective electrical power generation device 56 to supply electrical power to the hydraulic fracturing system 10. In some embodiments, one or more of the hydraulic fracturing units 12 may include electrical power generation capability, such as an auxiliary internal combustion engine and an auxiliary electrical power generation device driven by the auxiliary internal combustion engine. As shown is FIG. 1, some embodiments of the hydraulic fracturing system 10 may include electrical power lines 56 for supplying electrical power from the one or more electrical power sources 52 to one or more of the hydraulic fracturing units 12.

Some embodiments also may include a data center 60 configured to facilitate receipt and transmission of data communications related to operation of one or more of the components of the hydraulic fracturing system 10. Such data communications may be received and/or transmitted via hard-wired communications cables and/or wireless communications, for example, according to known communications protocols. For example, the data center 60 may contain at least some components of the hydraulic fracturing control assembly 14, such as a supervisory controller 62 configured to receive signals from components of the hydraulic fracturing system 10 and/or communicate control signals to components of the hydraulic fracturing system 10, for example, to at least partially control operation of one or more components of the hydraulic fracturing system 10, such as, for example, the internal combustion engines 18, the transmissions 20, and/or the hydraulic fracturing pumps 16 of the hydraulic fracturing units 12, the chemical additive units 24, the hydration units 28, the blender 30, the conveyers 32, the frac manifold 38, the manifold assembly 46, the wellhead manifold 48, and/or any associated valves, pumps, and/or other components of the hydraulic fracturing system 10.

FIGS. 1 and 2 also include block diagrams of example hydraulic fracturing control assemblies 14 according to embodiments of the disclosure. Although FIGS. 1 and 2 depict certain components as being part of the example hydraulic fracturing control assemblies 14, one or more of such components may be separate from the hydraulic fracturing control assemblies 14. In some embodiments, the hydraulic fracturing control assembly 14 may be configured to semi- or fully-autonomously monitor and/or control operation of one or more of the hydraulic fracturing units 12 and/or other components of the hydraulic fracturing system 10, for example, as described herein. For example, the hydraulic fracturing control assembly 14 may be configured to operate a plurality of the hydraulic fracturing units 12, each of which may include a hydraulic fracturing pump 16 to pump fracturing fluid into a wellhead 50 and an internal combustion engine 18 to drive the hydraulic fracturing pump 16 via the transmission 20.

As shown in FIGS. 1 and 2, some embodiments of the hydraulic fracturing control assembly 14 may include an input device 64 configured to facilitate communication of operational parameters 66 to a supervisory controller 62. In some embodiments, the input device 64 may include a computer configured to provide one or more operational parameters 66 to the supervisory controller 62, for example, from a location remote from the hydraulic fracturing system 10 and/or a user input device, such as a keyboard linked to a display associated with a computing device, a touchscreen of a smartphone, a tablet, a laptop, a handheld computing device, and/or other types of input devices. In some embodiments, the operational parameters 66 may include, but are not limited to, a target flow rate, a target pressure, a maximum flow rate, and/or a minimum flow rate associated with fracturing fluid supplied to the wellhead 50. In some examples, an operator associated with a hydraulic fracturing operation performed by the hydraulic fracturing system 10 may provide one more of the operational parameters 66 to the supervisory controller 62, and/or one or more of the operational parameters 66 may be stored in computer memory and provided to the supervisory controller 62 upon initiation of at least a portion of the hydraulic fracturing operation.

For example, an equipment profiler (e.g., a pump profiler) may calculate, record, store, and/or access data related each of the hydraulic fracturing units 12 including, but not limited to, pump data 68 including pump characteristics 70, maintenance data associated with the hydraulic fracturing units 12 (e.g., maintenance schedules and/or histories associated with the hydraulic fracturing pump 16, the internal combustion engine 18, and/or the transmission 20), operation data associated with the hydraulic fracturing units 12 (e.g., historical data associated with horsepower, fluid pressures, fluid flow rates, etc., associated with operation of the hydraulic fracturing units 12), data related to the transmissions 20 (e.g., hours of operation, efficiency, and/or installation age), data related to the internal combustion engines 18 (e.g., hours of operation, available power, and/or installation age), information related to the hydraulic fracturing pumps 16 (e.g., hours of operation, plunger and/or stroke size, maximum speed, efficiency, health, and/or installation age), equipment health ratings (e.g., pump, engine, and/or transmission condition), and/or equipment alarm history (e.g., life reduction events, pump cavitation events, pump pulsation events, and/or emergency shutdown events). In some embodiments, the pump characteristics 70 may include, but are not limited to minimum flow rate, maximum flow rate, harmonization rate, and/or pump condition, collectively identified as 71 in FIG. 2.

In the embodiments shown in FIGS. 1 and 2, the hydraulic fracturing control assembly 14 may also include one or more sensors 72 configured to generate one or more sensor signals 74 indicative of a flow rate of fracturing fluid supplied by a respective one of the hydraulic fracturing pump 16 of a hydraulic fracturing unit 12 and/or supplied to the wellhead 50, a pressure associated with fracturing fluid provided by a respective hydraulic fracturing pump 16 of a hydraulic fracturing unit 12 and/or supplied to the wellhead 50, and/or an engine speed associated with operation of a respective internal combustion engine 18 of a hydraulic fracturing unit 12. For example, one or more sensors 72 may be connected to one or more of the hydraulic fracturing units 12 and may be configured to generate signals indicative of a fluid pressure supplied by an individual hydraulic fracturing pump 16 of a hydraulic fracturing unit, a flow rate associated with fracturing fluid supplied by a hydraulic fracturing pump 16 of a hydraulic fracturing unit, and/or an engine speed of an internal combustion engine 18 of a hydraulic fracturing unit 12. In some examples, one or more of the sensors 72 may be connected to the wellhead 50 and may be configured to generate signals indicative of fluid pressure of hydraulic fracturing fluid at the wellhead 50 and/or a flow rate associated with the fracturing fluid at the wellhead 50. Other sensors (e.g., other sensor types for providing similar or different information) at the same or other locations of the hydraulic fracturing system 10 are contemplated.

As shown in FIG. 2, in some embodiments, the hydraulic fracturing control assembly 14 also may include one or more blender sensors 76 associated with the blender 30 and configured to generate blender signals 78 indicative of an output of the blender 30, such as, for example, a flow rate and/or a pressure associated with fracturing fluid supplied to the hydraulic fracturing units 12 by the blender 30. Operation of one or more of the hydraulic fracturing units 12 may be controlled 78, for example, to prevent the hydraulic fracturing units 12 from supplying a greater flow rate of fracturing fluid to the wellhead 50 than the flow rate of fracturing fluid supplied by the blender 30, which may disrupt the fracturing operation and/or damage components of the hydraulic fracturing units 12 (e.g., the hydraulic fracturing pumps 16).

As shown in FIGS. 1 and 2, some embodiments of the hydraulic fracturing control assembly 14 may include a supervisory controller 62 in communication with the plurality of hydraulic fracturing units 12, the input device 64, and/or one or more of the sensors 72 and/or 76. For example, communications may be received and/or transmitted between the supervisory controller 62, the hydraulic fracturing units 12, and/or the sensors 72 and/or 76 via hard-wired communications cables and/or wireless communications, for example, according to known communications protocols.

In some embodiments, the supervisory controller 62 may be configured to receive one or more operational parameters 66 associated with pumping fracturing fluid into the wellhead 50. For example, the operational parameters 66 may include a target flow rate and/or a target pressure 80 for fracturing fluid supplied to the wellhead 50. The supervisory controller 62 also may be configured to receive one or more pump characteristics 70, for example, associated with each of the hydraulic fracturing pumps 16 of the respective hydraulic fracturing units 12. As described previously herein, in some embodiments, the pump characteristics 70 may include a minimum flow rate, a maximum flow rate, a harmonization rate, and/or a pump condition 82 (individually or collectively) provided by the corresponding hydraulic fracturing pump 16 of a respective hydraulic fracturing unit 12. The pump characteristics 70 may be provided by an operator, for example, via the input device 64 and/or via a pump profiler, as described previously herein.

In some embodiments, the supervisory controller 62 may be configured to determine whether the hydraulic fracturing units 12 have a capacity sufficient to achieve the target flow rate and/or the target pressure 80. For example, the supervisory controller 62 may be configured to make such determinations based at least partially on one or more of the pump characteristics 70, which the supervisory controller 62 may use to calculate (e.g., via addition) the collective capacity of the hydraulic fracturing units 12 to supply a sufficient flow rate and/or a sufficient pressure to achieve the target flow rate and/or the target pressure 80 at the wellhead 50. For example, the supervisory controller 62 may be configured to determine a total pump flow rate by combining at least one of the pump characteristics 70 for each of the plurality of hydraulic fracturing pumps 16, and comparing the total pump flow rate to the target flow rate. In some embodiments, determining the total pump flow rate may include adding the maximum flow rates of each of the hydraulic fracturing pumps 16.

In some embodiments, the supervisory controller 62 may be configured to receive one or more signals indicative of a pump condition of one or more hydraulic fracturing pumps 16 of the plurality of hydraulic fracturing units 16 and determine the maximum flow rate for each of the hydraulic fracturing pumps 16 based at least in part on the one or more signals indicative of pump condition. In some embodiments, the pump condition may include one or more of total pump strokes, maximum recorded pressure produced, maximum recorded flow produced, maximum recorded pump speed produced, total pump hours, pressure pump efficiency health, pump installation age, pump deration based on health, pump cavitation events, pump pulsation events, emergency shut-down events, and/or any other use-related characteristics of the hydraulic fracturing pumps 16.

In some embodiments, upon initiation of a fracturing operation, for example, by an operator associated with the hydraulic fracturing system 10, the supervisory controller 62 may be configured to increase a flow rate from at least some of the hydraulic fracturing units 12 according to a controlled increasing flow rate schedule 82 toward the target flow rate and/or the target pressure 80. For example, rather than allowing the hydraulic fracturing units 12 to increase respective flow rate outputs in an uncontrolled manner (e.g., at a rate provided by the output of the internal combustion engine 18), the supervisory controller 62 may ramp-up the flow rate at a lower rate of change than could be achieved without control. This may reduce the likelihood or prevent the hydraulic fracturing pumps 16 from over-speeding and/or being subjected to cavitation by the fracturing fluid when increasing the flow rate toward the target flow rate and/or target pressure 80. In some embodiments, the controlled flow rate increase provided by the controlled increasing flow rate schedule 82 may be substantially constant (e.g., the rate of change of the flow rate), may be increasing as the flow rate increases, may be decreasing as the flow rate increases, and/or may increase or decrease based at least partially on the flow rate. In some examples, flow rates provided by different hydraulic fracturing units 12 may change according to different schedules and/or strategies, for example, such that the hydraulic fracturing units 12 do not increase flow rate at the same rate or according to the same schedule.

In some embodiments, the supervisory controller 62 may be configured to increase the flow rate from at least some of the hydraulic fracturing units 12 by maintaining a rate of change of the flow rate provided by at least some of the hydraulic fracturing units 12 below a maximum rate of change of the flow rate until at least some of the hydraulic fracturing units 12 have achieved the target flow rate and/or the target pressure. For example, the supervisory controller 62 may be configured to determine the maximum rate of change of the flow rate by changing the maximum rate of change of the flow rate as the total flow rate increases to achieve the target flow rate and/or the target pressure. In some embodiments, the supervisory controller 62 may be configured to receive one or more signals indicative fracturing fluid pressure at the wellhead 50, and determine the maximum rate of change of the flow rate based at least in part on the one or more signals indicative of the fluid pressure at the wellhead 50.

Table 1 below provides an example controlled increasing flow rate schedule 82. According to the example in Table 1, the rate of change of the flow rate is reduced as the fracturing fluid pressure increases, from a maximum rate of change of 3 barrels per minute per second (BPM/sec), up until a fracturing fluid pressure of 500 pounds per square inch (psi). Above 500 psi fracturing fluid pressure, the rate of change of the flow rate decreases to 2 BPM/sec until the fracturing fluid pressure reaches 5,000 psi. From 5,000 psi to 10,000 psi fracturing fluid pressure, the rate of change of the flow rate is reduced to 1 BPM/sec. Above 10,000 psi, the rate of change of the flow rate is further reduced to 0.5 BPM/sec. In some embodiments, the supervisory controller 62 may be configured to generate one or more pump flow rate signals and/or pump pressure signals 84, which may be communicated to one or more of the hydraulic fracturing units 12 to control operation of the hydraulic fracturing pumps 16, the internal combustion engines 18, and/or the transmissions 20, such that the output of the hydraulic fracturing pumps 16 corresponds to the one or more control signals 84.

	TABLE 1
		Maximum Rate of Change
	Wellhead Pressure Range (psi)	of Flow Rate (BPM/sec)
0-500	psi	3	BPM/sec
500-5,000	psi	2	BPM/sec
5,000-10,000	psi	1	BPM/sec
10,000-15,000	psi	0.5	BPM/sec
	Slow Rate Adjustment	0.5	BPM/sec

As described in more detail below, during operation of the hydraulic fracturing system 10, the supervisory controller 62 may be configured to receive one or more signals indicative of a maximum fluid pressure at the wellhead 50. For example, an operator may use the input device 64 to provide a maximum fluid pressure at the wellhead 50, the maximum fluid pressure may be stored and/or accessed by the supervisory controller 62, and/or the maximum fluid pressure may be calculated by the supervisory controller 62 based at least in part on, for example, one or more of the operational parameters 66, one or more of the pump characteristics 70, and/or information relating to the well. In some embodiments, when the fluid pressure at the wellhead 50 increases to within an upper range of the maximum fluid pressure, the supervisory controller 62 may be configured to generate one or more notification signals 86 indicative of the fluid pressure being within the upper range of the maximum fluid pressure. The upper range may range from about 25% below the maximum pressure to about 5% below the maximum pressure (e.g., about 10% below the maximum pressure). In some embodiments, when the fracturing fluid pressure at the wellhead 50 increases to within the upper range of the maximum fluid pressure, the supervisory controller 62 may be configured to reduce a rate of change of the flow rate provided by the hydraulic fracturing units 12 and/or reduce the target flow rate, for example, according to a rate of flow rate change (e.g., 2.5% per second), and/or generate one or more notification signals 86 indicative of reducing the target rate, which may be received by one or more output devices 88 to notify an on-site operator and/or remotely located personnel, for example, as described herein.

In some embodiments, a maximum operating pressure set point may be established that may be less than a wellhead kick-out pressure, for example, a fracturing fluid pressure at the wellhead 50, above which the supervisory controller 62 will cause the hydraulic fracturing system 10 to reduce pumping output and/or cease pumping output. In such embodiments, if it is determined that the fracturing fluid pressure at the wellhead 50 approaches to within a specified upper range of the wellhead kick-out pressure, the supervisory controller 62 may be configured to generate one or more notification signals 86 to notify an on-site or remotely located operator or computing device communicating an indication (e.g., an alarm) of the fracturing fluid pressure approaching the wellhead kick-out pressure. In some embodiments, the notification signals 86 may be communicated to one or more output devices 88, which may be configured to provide a visual, audible, and/or tactile (e.g., vibration) alarm for an operator located on-site and/or personnel located remotely from the hydraulic fracturing operation, such as at a fracturing management facility. The output device(s) 88 may include a computer display device, a hand-held computing device, such as a smartphone, a tablet, and/or a dedicated held-held display device. In some embodiments, the output device(s) 88 may include a speaker, a siren, an alarm, and/or a hand-held computing device. In some embodiments, following reducing the target flow rate, when the fracturing fluid pressure at the wellhead 50 falls below a lower range of the maximum fluid pressure, the supervisory controller 62 may be configured to increase the flow rate provided by the hydraulic fracturing units 12, for example, until the fracturing fluid pressure at the wellhead 50 returns to within the upper range of the maximum fluid pressure.

In some embodiments, the supervisory controller 62 also may be configured to generate one or more control signals 84 causing one or more of the hydraulic fracturing units 12 to operate according to a slow rate adjustment mode, for example, to reduce the likelihood or prevent the fracturing fluid pressure from reaching or exceeding the wellhead kick-out pressure. For example, as shown in Table 1, the slow rate adjustment may be set to 0.5 BPM/sec. In some examples, the upper range (e.g., within twenty percent, fifteen percent, ten percent, or five percent of the wellhead kick-out pressure) may be set by the operator and/or may be predetermined and stored in memory accessible by the supervisory controller 62. Upon triggering of the slow rate adjustment mode, some embodiments of supervisory controller 62 may be configured communicate one or more control signals 84 to one or more of the hydraulic fracturing units 12, so that they can operate to provide the flow rate corresponding to the slow rate adjustment. In some examples the slow rate adjustment may be set by the operator and/or may be predetermined and stored in memory accessible by the supervisory controller 62.

In some embodiments, the supervisory controller 62 may be configured to determine, based at least in part on the one or more sensor signals 74 indicative of flow rate of fracturing fluid and/or the pressure associated with fracturing fluid at the wellhead 50, whether at least some of the hydraulic fracturing units 12 have achieved the target flow rate and/or the target pressure 80. In some embodiments, the supervisory controller 62 may receive sensor signals 74 from one or more wellhead sensors 90 configured to generate one or more signals indicative of the flow rate and or fracturing fluid pressure 84. In some embodiments, the supervisory controller 62 may receive sensor signals 74 indicative of flow rate of fracturing fluid and/or the pressure associated with fracturing fluid from the one or more sensors 72 associated with each of the hydraulic fracturing units 12. In some such embodiments, the supervisory controller 62 may be configured to combine (e.g., add together) the flow rates and/or pressures from the sensors 74 to determine a total flow rate and/or a total pressure. In some embodiments, the supervisory controller 62 may be configured to receive sensor signals 74 from the one or more hydraulic fracturing units 12 and the wellhead sensors 90 and determine whether the at least some of the hydraulic fracturing units 12 have achieved the target flow rate and/or the target pressure 80, for example, at the wellhead 50.

In some embodiments, the supervisory controller 62, based at least in part on determination of whether the hydraulic fracturing units 12 have achieved the target flow rate and/or the target pressure 80, may be configured to control operation of one or more of the hydraulic fracturing units 12. For example, when it has been determined (e.g., via the supervisory controller 62) that the one or more of the target flow rate or the target pressure 80 has been achieved, the supervisory controller 62 may be configured to cause one or more of the hydraulic fracturing units 12 to operate to substantially maintain the target flow rate and/or the target pressure 80. For example, the supervisory controller 62 may generate the pump flow rate control signals and/or the pump pressure control signals 84 (see FIG. 2), which may be received by an engine control unit and/or a pump control unit (e.g., at a remote terminal unit), which may control operation of the internal combustion engine 18 and/or the hydraulic fracturing pump 16 of one or more of the hydraulic fracturing units 12, so that the hydraulic fracturing units 12 supply fracturing fluid to the wellhead 50 according to the target flow rate and/or the target pressure 80.

In some examples, once the target flow rate and/or the target pressure 80 has been achieved, the supervisory controller 62 may be configured to receive one or more signals indicative of a total flow rate of fracturing fluid supplied by the hydraulic fracturing units 12 to the wellhead 50. Based at least in part on the one or more signals indicative of the total flow rate, the supervisory controller 62 may be configured to determine whether the total flow rate is decreasing relative to the target flow rate. Based at least in part on this determination, the supervisory controller 62 may be configured to increase the flow rate to substantially maintain the target flow rate, for example, when it has been determined (e.g., by the supervisory controller 62) that the total flow rate is decreasing relative to the target flow rate. In some embodiments, when it has been determined that the total flow rate is substantially equal to the target flow rate, the supervisory controller 62 may be configured to maintain the target flow rate.

In some embodiments, when it has been determined (e.g., via the supervisory controller 62) that the target flow rate has not been achieved, the supervisory controller 62 may be configured to generate one or more notification signals 86 indicative of a failure to achieve the target flow rate. For example, prior to initiation of the fracturing operation, an operator may use the input device 64 to select via, for example, a graphical user interface, that the hydraulic fracturing system 10 operate according to a first mode of operation, which may be configured to control operation of the one or more hydraulic fracturing units 12 according to a flow rate-based strategy, for example, as explained in more detail with respect to FIGS. 3A and 3B. In some such embodiments, when it has been determined that a target flow rate has not been achieved, the notification signals 86 may be received by one or more output devices 88, for example, as described previously herein, which may serve to notify an operator or other personnel of the failure to achieve the target flow rate.

In some embodiments, when it has been determined (e.g., via the supervisory controller 62) that the target pressure has not been achieved, the supervisory controller 62 may be configured to operate the hydraulic fracturing units 12 to substantially maintain a maximum flow rate. For example, prior to initiation of the fracturing operation, an operator may use the input device 64 to select via, for example, a graphical user interface, that the hydraulic fracturing system 10 operate according to a second mode of operation, which may be configured to control operation of the one or more hydraulic fracturing units 12 according to a fracturing fluid pressure-based strategy, for example, as explained in more detail with respect to FIGS. 4A, 4B, and 4C. In some such embodiments, when it has been determined that the target pressure has not been achieved, the supervisory controller 62 may be configured to cause one or more of the hydraulic fracturing units 12 to operate to substantially maintain a respective maximum flow rate, which may result in providing a highest available fracturing fluid pressure at the wellhead 50. For example, the supervisory controller 62 may generate the pump flow rate control signals 84 (see FIG. 2), which may be received by an engine control unit and/or a pump control unit (e.g., at a remote terminal unit), which may control operation of the internal combustion engine 18 and/or the hydraulic fracturing pump 16 of one or more of the hydraulic fracturing units 12, so that the hydraulic fracturing units 12 supply the maximum available flow rate to the wellhead 50.

In some embodiments, when hydraulic fracturing control assembly 14 is operating according to the second mode of operation (e.g., the target pressure-based mode), when the maximum total flow rate has not been achieved, the supervisory controller 62 may be configured to substantially maintain the fracturing fluid pressure at the wellhead 50 to within a pressure differential of the fracturing fluid pressure by (1) increasing the total flow rate to increase the fracturing fluid pressure at the wellhead 50 to be within the pressure differential, or (2) decreasing the total flow rate to decrease the fracturing fluid pressure at the wellhead 50 to be within the pressure differential. In some embodiments, the pressure differential may be included with the operational parameters 66, which may be provided by the operator prior to beginning pumping of fracturing fluid by the hydraulic fracturing units 12, for example, via the input device 64. The pressure differential may range from about 100 psi to about 800 psi, from about 200 psi to about 600 psi, or from about 300 psi to about 500 psi.

In some embodiments, when hydraulic fracturing control assembly 14 is operating according to the second mode of operation (e.g., the target pressure-based mode), the supervisory controller 62 may be configured to receive the one or more operational parameters associated with pumping fracturing fluid into a wellhead 50 including receiving a maximum flow rate, which may be provided by the operator. In such embodiments, the supervisory controller 62 may be configured to increase the flow rate from the hydraulic fracturing units 12 while substantially maintaining the flow rate from the hydraulic fracturing units 12 below the maximum flow rate.

Some embodiments of the supervisory controller 62 may be configured to substantially maintain the flow rate and/or fluid pressure provided by the hydraulic fracturing units 12, for example, if an operator causes generation of one or more signals indicative of switching out of the first mode of operation or the second mode of operation, for example, to a third, manual mode of operation. For example, if the supervisory controller 62 is controlling operation of the hydraulic fracturing units 12 according to the first or second modes of operation, the operator may cause the supervisory controller 62 to exit the mode of operation, such that the operator may manually control operation of the hydraulic fracturing units 12. For example, the operator may use the input device 64 to exit the first or second mode of operation. Under such circumstances, the supervisory controller 62 may be configured to cause the hydraulic fracturing units 12 to continue to operate at flow rates substantially the same as flow rates at the time of receipt of the one or more signals indicative of ceasing the first or second modes of operation. Thereafter, the operator may manually generate control signals for controlling operation and/or the output of the hydraulic fracturing units 12. In some embodiments, even when operation has been switched to a manual mode, safety systems to detect and control operation during events, such as well screen outs and/or over pressure conditions, may continue to be controlled by the supervisory controller 62.

In some embodiments, the supervisory controller 62 may also be configured to receive one more signals indicative of fluid pressure (e.g., at the wellhead 50) and determine whether a well screen out or an over pressure condition exists, collectively identified as 92 in FIG. 2, during the hydraulic fracturing operation. For example, the supervisory controller 62 may receive sensor signals 74 from the wellhead sensors 90 and/or the hydraulic fracturing unit sensors 72 and determine whether a screen out or overpressure condition is occurring. In some examples, the supervisory controller 62 may leverage artificial intelligence to predict and/or detect such occurrences at an early stage. For example, the supervisory controller 62 may execute an analytical model, such a machine learning-trained analytical model, to recognize an imminent occurrence and/or the initial stages of the occurrence of a screen out and/or over pressure condition. According to some embodiments, in some such situations, the supervisory controller 62 may be configured such that when a well screen out or an over pressure condition is imminent or exists, the supervisory controller 62 may generate one or more notification signals 86 indicative of the one or more of the well screen out or the over pressure condition. The supervisory controller 62 further may be configured to cease increasing the flow rate from one or more of the hydraulic fracturing units 12. For example, the supervisory controller 62 may be configured to generate one or more control signals to cause one or more of the hydraulic fracturing units 12 to reduce output according to a mode change and/or shutdown sequence, such as the slow rate adjustment mode described previously herein and/or cease operation of one or more of the hydraulic fracturing units 12, for example, according to an emergency stop protocol.

In some embodiments, at the completion of one or more stages of the fracturing operation, the supervisory controller 62 may be configured to decrease the flow rate from the hydraulic fracturing units 12 according to a controlled decreasing flow rate schedule 96 (see FIG. 2) toward no flow of the fracturing fluid from the hydraulic fracturing units 12. For example, the supervisory controller 62 may be configured to receive one or more signals indicative of completion of the one or more stages. In some examples, the one or more signals may be automatically generated, for example, via a computing device according to an analytical model, manually entered, for example, via the input device 64, and/or triggered based at least in part on elapsed time (e.g., an elapsed time of operation of the hydraulic fracturing units 12). Based at least in part on the one or more signals indicative of completion of the one or more stages, the supervisory controller 62 may be configured to generate one or more control signals to cause the hydraulic fracturing units 12 to reduce the flow rate of fracturing fluid according to the controlled decreasing flow rate schedule 96. In some examples, the controlled decreasing flow rate schedule 96 may be similar to an inverted version of the controlled increasing flow rate schedule shown in Table 1, with rate of decreasing change of the flow rate increasing as the pressure drops. Other controlled decreasing flow rate schedules are contemplated.

FIGS. 3A, 3B, 4A, 4B, and 4C are block diagrams of example methods 300 and 400 of operating a plurality of hydraulic fracturing units according to embodiments of the disclosure, illustrated as a collection of blocks in a logical flow graph, which represent a sequence of operations. In the context of software, the blocks represent computer-executable instructions stored on one or more computer-readable storage media that, when executed by one or more processors, perform the recited operations. Generally, computer-executable instructions include routines, programs, objects, components, data structures, and the like that perform particular functions or implement particular data types. The order in which the operations are described is not intended to be construed as a limitation, and any number of the described blocks can be combined in any order and/or in parallel to implement the methods.

FIGS. 3A and 3B depict a flow diagram of an embodiment of a method 300 of operating a plurality of hydraulic fracturing units, according to an embodiment of the disclosure. For example, the example method 300 may be configured to operate according to a first mode of operation, which controls operation of one or more hydraulic fracturing units according to a flow rate-based strategy, for example, as previously described herein.

The example method 300, at 302, may include receiving a target flow rate associated with pumping fracturing fluid into a wellhead. For example, an operator of the hydraulic fracturing system may use an input device to provide operational parameters associated with the fracturing operation. A supervisory controller may receive the operational parameters as a basis for controlling operation of the hydraulic fracturing units. In some examples of the method 300, the operator may specify operation of the hydraulic fracturing units according to a first mode of operation, which controls operation of one or more hydraulic fracturing units according to a flow rate-based strategy.

At 304, the example method 300 further may include determining whether the hydraulic fracturing units have a capacity sufficient to achieve the target flow rate. For example, the supervisory controller may be configured to calculate the capacity based at least in part on pump characteristics received from a pump profiler, for example, as previously described herein.

If, at 304, it is determined that the hydraulic fracturing units lack sufficient capacity to achieve the target flow rate, at 306, the example method 300 also may include stopping the hydraulic fracturing process and/or generating one of more notification signals indicative of the insufficient capacity, for example, as discussed herein.

If, at 304, it is determined that the hydraulic fracturing units have a capacity sufficient to achieve the target flow rate, at 308, the example method 300 also may include initiating operation of the hydraulic fracturing units. For example, the supervisory controller may generate control signals for commencing operation of the hydraulic fracturing units.

The example method 300, at 310, also may include increasing a flow rate from the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the target flow rate, for example, as previously described herein.

At 312, the example method 300 also may include determining whether a well screen out or an over pressure condition exists. In some embodiments of the method 300, this may be performed substantially continuously by the supervisory controller during the hydraulic fracturing operation, for example, as described previously herein.

If, at 312, it is determined that a well screen out or an over pressure condition exists, at 314, the example method 300 also may include stopping the hydraulic fracturing process and/or generating one of more notification signals indicative of the insufficient capacity. In some embodiments of the method 300, this may be performed by the supervisory controller during the hydraulic fracturing operation, for example, as described previously herein.

If, at 312, it is determined that a well screen out or an over pressure condition does not exist, at 316, the example method 300 further may include continuing to increase the flow rate from the hydraulic fracturing units according to the controlled increasing flow rate schedule toward the target flow rate. In some embodiments of the method 300, this may be performed by the supervisory controller, for example, as described previously herein.

Referring to FIG. 3B, the example method 300, at 318, further may include operating the hydraulic fracturing units to maintain the target flow rate and/or a target pressure. In some embodiments of the method 300, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

The example method 300, at 320, further may include receiving signals indicative of a total flow rate of the hydraulic fracturing units. For example, the supervisory controller may receive the signals, for example, as described previously herein

The example method 300, at 322, may include determining whether the total flow rate is decreasing relative to the target flow rate. In some embodiments of the method 300, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 322, it is determined that the total flow rate is not decreasing relative to the target flow rate, at 324, the example method 300 also may include maintaining the target flow rate. In some embodiments of the method 300, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 322, it is determined that the total flow rate is decreasing relative to the target flow rate, at 326, the example method 300 further may include increasing the flow rate to substantially maintain the target flow rate. In some embodiments of the method 300, this may be performed by the supervisory controller, for example, as described previously herein

The example method 300, at 328, further may include receiving signals indicative of a blender output upstream of the plurality of hydraulic fracturing units. In some embodiments of the method 300, this may be performed substantially continuously during the hydraulic fracturing operation by the supervisory controller.

The example method 300, at 330, also may include control operation of each of the hydraulic fracturing units based at least in part on the signals indicative of the blender output. For example, if the blender output is insufficient to supply the hydraulic fracturing units with fracturing fluid to maintain the target flow rate, the target flow rate may be reduced to a point at which the blender output is sufficient to supply fracturing fluid to the hydraulic fracturing units to achieve the lowered target flow rate.

At 332, the example method 300 also may include receiving one or more signals indicative of completion of one or more stages of a hydraulic fracturing operation. For example, when the fracturing operation is substantially complete, the operator may use an input device to indicate that the fracturing operation is complete. In some embodiments, the supervisory controller may be configured to automatically generate the one or more signals indicative of completion, for example, based at least partially on duration of operation, a total amount of fracturing fluid pumped by the hydraulic fracturing units, and/or pressure at the wellhead.

At 334, the example method 300 may further include decreasing the flow rate from the hydraulic fracturing units according to a controlled decreasing flow rate schedule toward no flow, for example, as previously described herein. After 334, the example method 300 may end.

FIGS. 4A, 4B, and 4C depict a flow diagram of an embodiment of a method 400 of operating a plurality of hydraulic fracturing units, according to an embodiment of the disclosure. For example, the example method 400 may be configured to operate according to a second mode of operation, which controls operation of one or more hydraulic fracturing units according to a pressure-based strategy, for example, as previously described herein.

The example method 400, at 402, may include receiving a maximum flow rate and a target pressure associated with pumping fracturing fluid into a wellhead. For example, an operator may use the input device to provide operational parameters, which may include the target pressure and a maximum flow rate. An operator of the hydraulic fracturing system may use an input device to provide operational parameters associated with the fracturing operation. A supervisory controller may receive the operational parameters as a basis for controlling operation of the hydraulic fracturing units. In some examples of the method 400, the operator may specify operation of the hydraulic fracturing units according to a second mode of operation, which controls operation of one or more hydraulic fracturing units according to a pressure-based strategy.

At 404, the example method 400 further may include receiving signals indicative of operation of the hydraulic fracturing units according to a constant pressure mode, for example, as compared to a target flow rate mode, for example, as described with respect to FIGS. 3A and 3B.

At 406, the example method 400 also may include determining hydraulic fracturing units able to achieve the target pressure. For example, the supervisory controller may receive pump characteristics for each of the hydraulic fracturing units and determine whether the hydraulic fracturing units have sufficient capacity to achieve the target pressure, for example, as described previously herein.

The example method 400, at 408, further may include initiating operation of the hydraulic fracturing units. For example, the supervisory controller may generate control signals for commencing operation of the hydraulic fracturing units.

The example method 400, at 410, also may include increasing a flow rate from the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the maximum flow rate or target pressure, for example as previously described herein with respect to FIG. 2.

At 412, the example method 400 also may include determining whether a well screen out or an over pressure condition exists. In some embodiments of the method 400, this may be performed by the supervisory controller substantially continuously during the hydraulic fracturing operation.

If, at 412, it is determined that a well screen out or an over pressure condition exists, at 414, the example method 400 also may include stopping the hydraulic fracturing process and/or generating one of more notification signals indicative of the insufficient capacity, for example, as discussed herein.

If, at 412, it is determined that a well screen out or an over pressure condition does not exist, at 416, the example method 400 further may include continuing to increase the flow rate from the hydraulic fracturing units according to the controlled increasing flow rate schedule toward the maximum pressure or the target pressure, for example, as previously described herein.

Referring to FIG. 4B, at 418, the example method 400 may further include determining whether the hydraulic fracturing units have achieved the target pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 418, it is determined that the hydraulic fracturing units have not achieved the target pressure, the example method 400 may skip to 434 (see FIG. 4C).

If, at 418, it is determined that the hydraulic fracturing units have achieved the target pressure, at 420, the example method 400 may include operating the hydraulic fracturing units at flow rates to maintain the target pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

The example method 400, at 422, further may include determining whether the pressure is decreasing relative to the target pressure. For example, the supervisory controller may receive signals indicative of the pressure at the wellhead and determine whether the pressure has decreased relative to the target pressure, for example, as previously described herein.

If, at 422, it is determined that the pressure is not decreasing relative to the target pressure, at 424, the example method 400 also may include maintaining the flow rates to maintain the target pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 422, it is determined that the pressure is decreasing relative to the target pressure, at 426, the example method 400 further may include determining whether the pressure has decreased to more than a threshold amount less than the target pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 426, it is determined that the pressure has decreased to more than the threshold amount less than the target pressure, the example method 400 may skip to 434 (see FIG. 4C).

If, at 426, it is determined that the pressure has decreased to more than the threshold amount less than the target pressure, at 428, the example method 400 further may include determining whether the pressure has decreased to more than a threshold amount less than the target pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

At 426, the example method 400 also may include determining whether the pressure has increased to more than a threshold amount more than the target pressure. For example, after it has been determined that the pressure has decreased to more than the threshold amount less than the target pressure, the method 400 may include increasing the flow rate to increase the pressure to a point greater than the threshold amount lower than the target pressure. Thereafter, at 426, the method 400, further may include determining whether the pressure has increased to more than a threshold amount more than the target pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 426, it is determined that the pressure has increased to more than a threshold amount more than the target pressure, the example method 400, at 430, may include decreasing the flow rates to reduce the pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

At 432, the example method 400 also may include returning to 418.

If, at 426, it is determined that the pressure has not increased to more than a threshold amount more than the target pressure, the example method 400 skip to 446 (see FIG. 4C).

Referring to FIG. 4C, the example method 400, at 434, further may include determining whether the maximum flow rate has been achieved. For example, 434 may be performed following 418 and 426, for example, when the pressure fails to achieve the target pressure. In some embodiments, the method 400 includes increasing the flow rate to the maximum flow rate achievable by the hydraulic fracturing units to achieve the highest pressure possible using the hydraulic fracturing units. At 434, the method 400 may include determining whether the maximum flow rate has been achieved. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 434, it is determined that the maximum flow rate has not been achieved, at 436, the method 400 also may include increasing flow rates to achieve the maximum flow rate. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 434, it is determined that the maximum flow rate has been achieved, at 438, the method 400 further may include operating the hydraulic fracturing units to maintain the maximum flow rate. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

At 440, the example method 400 may further include determining whether the pressure has increased to more than a threshold amount more than the target pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 440, it is determined that the pressure has increased to more than the threshold amount more than the target pressure, at 442, the method 400 also may include decreasing flow rates to reduce the pressure. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

At 444, the example method 400 further may include returning to 418 (see FIG. 4B), for example, to determine whether the target pressure has been achieved. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

If, at 440, it is determined that the pressure has increased to more than the threshold amount more than the target pressure, at 446, the method 400 further may include operating the hydraulic fracturing units to maintain the maximum flow rate. In some embodiments of the method 400, this may be performed during the fracturing operation by the supervisory controller, for example, as described previously herein.

The example method 400, at 448, further may include receiving one or more signals indicative of completion of one or more stages of a hydraulic fracturing operation. For example, when the fracturing operation is substantially complete, the operator may use an input device to indicate that the fracturing operation is complete. In some embodiments, the supervisory controller may be configured to automatically generate the one or more signals indicative of completion, for example, based at least partially on duration of operation, a total amount of fracturing fluid pumped by the hydraulic fracturing units, and/or pressure at the wellhead

The example method 400, at 450, may include decreasing the flow rate from the hydraulic fracturing units according to a controlled decreasing flow rate schedule toward no flow, for example, as previously described herein. After 450, the example method 400 may end.

It should be appreciated that subject matter presented herein may be implemented as a computer process, a computer-controlled apparatus, a computing system, or an article of manufacture, such as a computer-readable storage medium. While the subject matter described herein is presented in the general context of program modules that execute on one or more computing devices, those skilled in the art will recognize that other implementations may be performed in combination with other types of program modules. Generally, program modules include routines, programs, components, data structures, and other types of structures that perform particular tasks or implement particular abstract data types.

Those skilled in the art will also appreciate that aspects of the subject matter described herein may be practiced on or in conjunction with other computer system configurations beyond those described herein, including multiprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers, handheld computers, mobile telephone devices, tablet computing devices, special-purposed hardware devices, network appliances, and the like.

FIG. 5 illustrates an example supervisory controller 62 configured for implementing certain systems and methods for supplying fuel to a plurality GTEs (e.g., dual- or bi-fuel GTEs configured to operate using two different types of fuel) according to embodiments of the disclosure, for example, as described herein. The supervisory controller 62 may include one or more processor(s) 500 configured to execute certain operational aspects associated with implementing certain systems and methods described herein. The processor(s) 500 may communicate with a memory 502. The processor(s) 500 may be implemented and operated using appropriate hardware, software, firmware, or combinations thereof. Software or firmware implementations may include computer-executable or machine-executable instructions written in any suitable programming language to perform the various functions described. In some examples, instructions associated with a function block language may be stored in the memory 502 and executed by the processor(s) 500.

The memory 502 may be used to store program instructions that are loadable and executable by the processor(s) 500, as well as to store data generated during the execution of these programs. Depending on the configuration and type of the supervisory controller 62, the memory 502 may be volatile (such as random access memory (RAM)) and/or non-volatile (such as read-only memory (ROM), flash memory, etc.). In some examples, the memory devices may include additional removable storage 504 and/or non-removable storage 506 including, but not limited to, magnetic storage, optical disks, and/or tape storage. The disk drives and their associated computer-readable media may provide non-volatile storage of computer-readable instructions, data structures, program modules, and other data for the devices. In some implementations, the memory 502 may include multiple different types of memory, such as static random access memory (SRAM), dynamic random access memory (DRAM), or ROM.

The memory 502, the removable storage 504, and the non-removable storage 506 are all examples of computer-readable storage media. For example, computer-readable storage media may include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. Additional types of computer storage media that may be present may include, but are not limited to, programmable random access memory (PRAM), SRAM, DRAM, RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile discs (DVD) or other optical storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium which may be used to store the desired information and which may be accessed by the devices. Combinations of any of the above should also be included within the scope of computer-readable media.

The supervisory controller 62 may also include one or more communication connection(s) 508 that may facilitate a control device (not shown) to communicate with devices or equipment capable of communicating with the supervisory controller 62. The supervisory controller 62 may also include a computer system (not shown). Connections may also be established via various data communication channels or ports, such as USB or COM ports to receive cables connecting the supervisory controller 62 to various other devices on a network. In some examples, the supervisory controller 62 may include Ethernet drivers that enable the supervisory controller 62 to communicate with other devices on the network. According to various examples, communication connections 508 may be established via a wired and/or wireless connection on the network.

The supervisory controller 62 may also include one or more input devices 510, such as a keyboard, mouse, pen, voice input device, gesture input device, and/or touch input device. The one or more input device(s) 510 may correspond to the one or more input devices 64 described herein with respect to FIGS. 1 and 2. It may further include one or more output devices 512, such as a display, printer, and/or speakers. In some examples, computer-readable communication media may include computer-readable instructions, program modules, or other data transmitted within a data signal, such as a carrier wave or other transmission. As used herein, however, computer-readable storage media may not include computer-readable communication media.

Turning to the contents of the memory 502, the memory 502 may include, but is not limited to, an operating system (OS) 514 and one or more application programs or services for implementing the features and embodiments disclosed herein. Such applications or services may include remote terminal units 516 for executing certain systems and methods for controlling operation of the hydraulic fracturing units 12 (e.g., semi- or full-autonomously controlling operation of the hydraulic fracturing units 12), for example, upon receipt of one or more control signals generated by the supervisory controller 62. In some embodiments, each of the hydraulic fracturing units 12 may include a remote terminal unit 516. The remote terminal units 516 may reside in the memory 502 or may be independent of the supervisory controller 62. In some examples, the remote terminal unit 516 may be implemented by software that may be provided in configurable control block language and may be stored in non-volatile memory. When executed by the processor(s) 500, the remote terminal unit 516 may implement the various functionalities and features associated with the supervisory controller 62 described herein.

As desired, embodiments of the disclosure may include a supervisory controller 62 with more or fewer components than are illustrated in FIG. 5. Additionally, certain components of the example supervisory controller 62 shown in FIG. 5 may be combined in various embodiments of the disclosure. The supervisory controller 62 of FIG. 5 is provided by way of example only.

References are made to block diagrams of systems, methods, apparatuses, and computer program products according to example embodiments. It will be understood that at least some of the blocks of the block diagrams, and combinations of blocks in the block diagrams, may be implemented at least partially by computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, special purpose hardware-based computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functionality of at least some of the blocks of the block diagrams, or combinations of blocks in the block diagrams discussed.

These computer program instructions may also be stored in a non-transitory computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide task, acts, actions, or operations for implementing the functions specified in the block or blocks.

One or more components of the systems and one or more elements of the methods described herein may be implemented through an application program running on an operating system of a computer. They may also be practiced with other computer system configurations, including hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, mini-computers, mainframe computers, and the like.

Application programs that are components of the systems and methods described herein may include routines, programs, components, data structures, etc. that may implement certain abstract data types and perform certain tasks or actions. In a distributed computing environment, the application program (in whole or in part) may be located in local memory or in other storage. In addition, or alternatively, the application program (in whole or in part) may be located in remote memory or in storage to allow for circumstances where tasks can be performed by remote processing devices linked through a communications network.

This U.S. Non-Provisional patent application claims priority to and the benefit of, under 35 U.S.C. § 119(e), U.S. Provisional Application No. 62/705,328, filed Jun. 22, 2020, titled “SYSTEMS AND METHODS TO OPERATE HYDRAULIC FRACTURING UNITS USING AUTOMATIC FLOW RATE AND/OR PRESSURE CONTROL”, U.S. Provisional Application No. 62/705,369, filed Jun. 24, 2020, titled “SYSTEMS AND METHODS PROVIDING A CONFIGURABLE STAGED RATE INCREASE FUNCTION TO OPERATE HYDRAULIC FRACTURING UNITS”, and U.S. Provisional Application No. 62/705,649, filed Jul. 9, 2020, titled “SYSTEMS AND METHODS PROVIDING A CONFIGURABLE STAGED RATE INCREASE FUNCTION TO OPERATE HYDRAULIC FRACTURING UNITS”, the disclosures of all of which are incorporated herein by reference in their entirety.

Although only a few exemplary embodiments have been described in detail herein, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the embodiments of the present disclosure. Accordingly, all such modifications are intended to be included within the scope of the embodiments of the present disclosure as defined in the following claims.

Claims

1. A method of operating a plurality of hydraulic fracturing units, each of the hydraulic fracturing units including a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump, the method comprising: receiving, via a supervisory controller, one or more operational parameters associated with pumping fracturing fluid into a wellhead, the one or more operational parameters including one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead;determining, via the supervisory controller, whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressure;initiating operation of at least some of the plurality of hydraulic fracturing units;increasing a flow rate from the at least some of the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the one or more of the target flow rate or the target pressure, the controlled increasing flow rate schedule including two or more different rates of change of flow rate corresponding to two or more wellhead pressure ranges;receiving one or more signals indicative of a blender output upstream of the plurality of hydraulic fracturing units;controlling operation of each of the at least some hydraulic fracturing units based at least in part on the one or more signals indicative of the blender output;determining whether the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure;one or more of: when it has been determined that the one or more of the target flow rate or the target pressure has been achieved, operating the at least some hydraulic fracturing units to maintain one or more of the target flow rate or the target pressure;when it has been determined that the target flow rate has not been achieved, generating one or more signals indicative of a failure to achieve the target flow rate; orwhen it has been determined that the target pressure has not been achieved, operating the at least some hydraulic fracturing units to maintain a maximum flow rate;receiving, via the supervisory controller, one or more signals indicative of a maximum fluid pressure at the wellhead;monitoring fluid pressure at the wellhead; andwhen the fluid pressure at the wellhead increases to within an upper range of the maximum fluid pressure, causing one or more of: generating one or more signals indicative of the fluid pressure being within the upper range of the maximum fluid pressure;reducing a rate of change of the flow rate provided by the at least some of the hydraulic fracturing units; orreducing the target flow rate.

2. The method of claim 1, wherein: the hydraulic fracturing units comprise a plurality of hydraulic fracturing pumps, each of the plurality of hydraulic fracturing pumps being associated with one of the plurality of hydraulic fracturing units; anddetermining whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressure comprises: receiving pump characteristics for each of the plurality of hydraulic fracturing pumps;determining a total pump flow rate by combining at least one of the pump characteristics for each of the plurality of hydraulic fracturing pumps; andcomparing the total pump flow rate to the target flow rate;the plurality of pump characteristics comprises one or more of a minimum flow rate, a maximum flow rate, a harmonization range, and a pump condition for each of the plurality of hydraulic fracturing pumps; anddetermining the total pump flow rate comprises adding the maximum flow rates of each of the hydraulic fracturing pumps.

3. The method of claim 1, further comprising: receiving one or more signals indicative of a pump condition of one or more hydraulic fracturing pumps of the plurality of hydraulic fracturing units; anddetermining a maximum flow rate for each of the one or more hydraulic fracturing pumps based at least in part on the one or more signals indicative of a pump condition of the one or more hydraulic fracturing pumps.

4. The method of claim 1, wherein increasing a flow rate from the at least some of the hydraulic fracturing units according to the controlled increasing flow rate schedule comprises maintaining a rate of change of the flow rate provided by the at least some of the hydraulic fracturing units below a maximum rate of change of the flow rate until the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure.

5. The method of claim 1, wherein: determining the maximum rate of change of the flow rate comprises changing the maximum rate of change of the flow rate as the total flow rate increases to achieve the one or more of the target flow rate or the target pressure; andthe method further comprises:receiving one or more signals indicative fluid pressure at the wellhead; anddetermining the maximum rate of change of the flow rate based at least in part on the one or more signals indicative of the fluid pressure at the wellhead.

6. The method of claim 1, further comprising receiving one more signals indicative of fluid pressure and determining whether a well screen out or an over pressure condition exists, wherein one or more of: when one or more of a well screen out or an over pressure condition exists, the method further comprises generating one or more signals indicative of the one or more of the well screen out or the over pressure condition; orwhen one or more of a well screen out or an over pressure condition exists, the method further comprises ceasing increasing of the flow rate from the at least some of the hydraulic fracturing units.

7. The method of claim 1, further comprising: receiving one or more signals indicative of a total flow rate of the at least some of the hydraulic fracturing units;determining whether the total flow rate is decreasing relative to the target flow rate; andone of: when it has been determined that the total flow rate is decreasing relative to the target flow rate, increasing the flow rate to substantially maintain the target flow rate; orwhen it has been determined that the total flow rate is substantially equal to the target flow rate, maintaining the target flow rate.

8. The method of claim 1, wherein: receiving one or more operational parameters associated with pumping fracturing fluid into a wellhead comprises receiving a target pressure for fracturing fluid supplied to the wellhead; andwhen it has been determined that the target pressure has not been achieved, the method further comprises:determining whether a maximum total flow rate has been achieved; andone of: when the maximum total flow rate has been achieved, maintaining the maximum total flow rate; orwhen the maximum total flow rate has not been achieved, increasing flow rates of the at least some hydraulic fracturing units to achieve the maximum total flow rate.

9. The method of claim 8, wherein one or more of: when the maximum total flow rate has not been achieved, the method further comprises maintaining a fluid pressure at the wellhead within a pressure differential of the fluid pressure by one of increasing the total flow rate to increase the fluid pressure at the wellhead to be within the pressure differential or decreasing the total flow rate to decrease the fluid pressure at the wellhead to be within the pressure differential; orreceiving the one or more operational parameters associated with pumping fracturing fluid into a wellhead comprises receiving a maximum flow rate; andincreasing the flow rate from the at least some of the hydraulic fracturing units comprises maintaining the flow rate from the at least some of the hydraulic fracturing units below the maximum flow rate.

10. The method of claim 1, wherein following reducing the target flow rate, when the fluid pressure at the wellhead falls below a lower range of the maximum fluid pressure, the method further comprises increasing the flow rate provided by the at least some of the hydraulic fracturing units until the fluid pressure at the wellhead returns to within the upper range of the maximum fluid pressure.

11. The method of claim 1, wherein the method comprises a first mode of operation, and the method further comprises: receiving, via the supervisory controller, one or more signals indicative of ceasing the first mode of operation; andcausing the at least some hydraulic fracturing units to continue to operate at flow rates substantially the same as flow rates at a time of receipt of the one or more signals indicative of ceasing the first mode of operation.

12. The method of claim 1, further comprising: receiving one or more signals indicative of a pressure associated with an output of each of the hydraulic fracturing pumps of the at least some hydraulic fracturing units; andcontrolling operation of each of the at least some hydraulic fracturing units based at least in part on the one or more signals indicative of the pressure associated with the output of each of the hydraulic fracturing pumps.

13. The method of claim 1, further comprising: performing one or more stages of pumping fracturing fluid into the wellhead;receiving, via the supervisory controller, one or more signals indicative of completion of the one or more stages; andbased at least in part on the one or more signals indicative of completion of the one or more stages, decreasing the flow rate from the at least some of the hydraulic fracturing units according to a controlled decreasing flow rate schedule toward no flow of the fracturing fluid from the at least some of the hydraulic fracturing units.

14. The method of claim 1, wherein determining whether the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure comprises: receiving, via the supervisory controller, one or more sensor signals indicative of one or more of a flow rate achieved by each of the at least some hydraulic fracturing units or a pressure achieved by the at least some of the hydraulic fracturing units;one or more of combining the one or more of the flow rate achieved by each of the at least some hydraulic fracturing units to determine a total flow rate or combining the pressure achieved by each of the hydraulic fracturing units to determine a total pressure; andcomparing one or more of the total flow rate or the total pressure to the one or more of the target flow rate or the target pressure.

15. A hydraulic fracturing control assembly to operate a plurality of hydraulic fracturing units, each of the hydraulic fracturing units including a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump, the hydraulic fracturing control assembly comprising: an input device configured to facilitate communication of operational parameters to a supervisory controller, the one or more operational parameters including one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead;one or more sensors configured to generate one or more sensor signals indicative of one or more of a flow rate of fracturing fluid or a pressure associated with fracturing fluid; anda supervisory controller in communication with one or more of the plurality of hydraulic fracturing units, the input device, or the one or more sensors, the supervisory controller being configured to: receive one or more operational parameters associated with pumping fracturing fluid into a wellhead, the one or more operational parameters including one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead;receive one or more signals indicative of a blender output upstream of the plurality of hydraulic fracturing units;determine whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressure;increase a flow rate from at least some of the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the one or more of the target flow rate or the target pressure, the controlled increasing flow rate schedule including two or more different rates of change of flow rate corresponding to two or more wellhead pressure ranges;control operation of each of the at least some hydraulic fracturing units based at least in part on the one or more signals indicative of the blender output;determine, based at least in part on the one or more sensor signals indicative of one or more of the flow rate of fracturing fluid or the pressure associated with fracturing fluid, whether the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure; andone or more of: when it has been determined that the one or more of the target flow rate or the target pressure has been achieved, operate the at least some hydraulic fracturing units to maintain one or more of the target flow rate or the target pressure;when it has been determined that the target flow rate has not been achieved, generate one or more signals indicative of a failure to achieve the target flow rate; orwhen it has been determined that the target pressure has not been achieved, operate the at least some hydraulic fracturing units to maintain a maximum flow rate.

16. The hydraulic fracturing control assembly of claim 15, wherein: the hydraulic fracturing units comprise a plurality of hydraulic fracturing pumps, each of the plurality of hydraulic fracturing pumps being associated with one of the plurality of hydraulic fracturing units; andthe supervisory controller is configured to: receive pump characteristics for each of the plurality of hydraulic fracturing pumps;determine a total pump flow rate by combining at least one of the pump characteristics for each of the plurality of hydraulic fracturing pumps; andcompare the total pump flow rate to the target flow rate to determine whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressure;the plurality of pump characteristics comprises one or more of a minimum flow rate, a maximum flow rate, a harmonization range, and a pump condition for each of the plurality of hydraulic fracturing pumps; andthe supervisory controller is configured to add the maximum flow rates of each of the hydraulic fracturing pumps to determine the total pump flow rate.

17. The hydraulic fracturing control assembly of claim 15, wherein one or more of: the supervisory controller is further configured to: receive one or more signals indicative of a pump condition of one or more hydraulic fracturing pumps of the plurality of hydraulic fracturing units; anddetermine a maximum flow rate for each of the one or more hydraulic fracturing pumps based at least in part on the one or more signals indicative of a pump condition of the one or more hydraulic fracturing pumps; orthe supervisory controller is configured to maintain a rate of change of the flow rate provided by the at least some of the hydraulic fracturing units below a maximum rate of change of the flow rate until the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure.

18. The hydraulic fracturing control assembly of claim 17, wherein one or more of: the supervisory controller is configured to change the maximum rate of change of the flow rate as the total flow rate increases to achieve the one or more of the target flow rate or the target pressure to determine the maximum rate of change of the flow rate; orthe one or more sensors include one or more wellhead sensors configured to generate one or more signals indicative of one or more of fluid flow rate or fluid pressure at the wellhead; andthe supervisory controller is configured to: receive one or more signals indicative one or more of fluid flow rate or fluid pressure at the wellhead; anddetermine the maximum rate of change of the flow rate based at least in part on the one or more signals indicative of one or more of the fluid flow rate of fluid pressure at the wellhead.

19. The hydraulic fracturing control assembly of claim 15, wherein: the supervisory controller is further configured to determine whether a well screen out or an over pressure condition exists based at least in part on the receiving the one more signals indicative of one or more of the flow rate of fracturing fluid or the pressure associated with fracturing fluid; andone or more of: when one or more of a well screen out or an over pressure condition exists, the supervisory controller is configured to generate one or more signals indicative of the one or more of the well screen out or the over pressure condition; orwhen one or more of a well screen out or an over pressure condition exists, the supervisory controller is further configured cease increasing of the flow rate from the at least some of the hydraulic fracturing units.

20. The hydraulic fracturing control assembly of claim 15, wherein the supervisory controller is configured to: determine, based at least in part on the one more signals indicative of one or more of the flow rate of fracturing fluid or the pressure associated with fracturing fluid, whether the total flow rate is decreasing relative to the target flow rate; andone of: when it has been determined that the total flow rate is decreasing relative to the target flow rate, increase the flow rate to substantially maintain the target flow rate; orwhen it has been determined that the total flow rate is substantially equal to the target flow rate, maintain the target flow rate.

21. The hydraulic fracturing control assembly of claim 15, wherein: the one or more operational parameters associated with pumping fracturing fluid into a wellhead comprises a target pressure for fracturing fluid supplied to the wellhead; andwhen it has been determined that the target pressure has not been achieved, the supervisory controller is further configured to:determine whether a maximum total flow rate has been achieved; andone of: when the maximum total flow rate has been achieved, maintain the maximum total flow rate; orwhen the maximum total flow rate has not been achieved, increase flow rates of the at least some hydraulic fracturing units to achieve the maximum total flow rate.

22. The hydraulic fracturing control assembly of claim 21, wherein one or more of: when the maximum total flow rate has not been achieved, the supervisory controller is configured to maintain a fluid pressure at the wellhead within a pressure differential of the fluid pressure by one of increasing the total flow rate to increase the fluid pressure at the wellhead to be within the pressure differential or decreasing the total flow rate to decrease the fluid pressure at the wellhead to be within the pressure differential; orthe one or more operational parameters associated with pumping fracturing fluid into a wellhead comprises a maximum flow rate, and the supervisory controller is configured to maintain the flow rate from the at least some of the hydraulic fracturing units below the maximum flow rate to increase the flow rate from the at least some of the hydraulic fracturing units.

23. The hydraulic fracturing control assembly of claim 15, wherein: the operational parameters comprise a maximum fluid pressure at the wellhead;the supervisory controller is configured to monitor fluid pressure at the wellhead; andwhen the fluid pressure at the wellhead increases to within an upper range of the maximum fluid pressure, the supervisory controller is configured to one or more of: generate one or more signals indicative of the fluid pressure being within the upper range of the maximum fluid pressure;reduce a rate of change of the flow rate provided by the at least some of the hydraulic fracturing units; orreduce the target flow rate.

24. The hydraulic fracturing control assembly of claim 23, wherein following reducing the target flow rate, when the fluid pressure at the wellhead falls below a lower range of the maximum fluid pressure, the supervisory controller is configured to increase the flow rate provided by the at least some of the hydraulic fracturing units until the fluid pressure at the wellhead returns to within the upper range of the maximum fluid pressure.

25. The hydraulic fracturing control assembly of claim 15, wherein one or more of: the hydraulic fracturing control assembly is configured to operate according to a first mode of operation, and the supervisory controller is configured to: receive one or more signals indicative of ceasing the first mode of operation; andcause the at least some hydraulic fracturing units to continue to operate at flow rates substantially the same as flow rates at a time of receipt of the one or more signals indicative of ceasing the first mode of operation; orthe one or more signals indicative of one or more of a flow rate of fracturing fluid or a pressure associated with fracturing fluid comprise one or more signals indicative of a pressure associated with an output of each of the hydraulic fracturing pumps of the at least some hydraulic fracturing units; andthe supervisory controller is configured to control operation of each of the at least some hydraulic fracturing units based at least in part on the one or more signals indicative of the pressure associated with the output of each of the hydraulic fracturing pumps.

26. The hydraulic fracturing control assembly of claim 15, wherein the supervisory controller is configured to: control operation of the at least some of the hydraulic fracturing units through one or more stages of pumping fracturing fluid into the wellhead;receive one or more signals indicative of completion of the one or more stages; andbased at least in part on the one or more signals indicative of completion of the one or more stages, decrease the flow rate from the at least some of the hydraulic fracturing units according to a controlled decreasing flow rate schedule toward no flow of the fracturing fluid from the at least some of the hydraulic fracturing units.

27. The hydraulic fracturing control assembly of claim 15, wherein: the one or more sensors comprise a plurality of fracturing unit sensors, each of the plurality of sensors being associated with one of the at least some of the hydraulic fracturing units and being configured to generate one or more sensor signals indicative of one or more of a flow rate achieved by each of the at least some hydraulic fracturing units or a pressure achieved by each of the at least some of the hydraulic fracturing units; andthe supervisory controller is configured to: receive the one or more sensor signals indicative of one or more of a flow rate or a pressure achieved by each of the at least some of the hydraulic fracturing units;one or more of combine the one or more of the flow rate achieved by each of the at least some hydraulic fracturing units to determine a total flow rate or combine the pressure achieved by each of the hydraulic fracturing units to determine a total pressure; andcompare one or more of the total flow rate or the total pressure to the one or more of the target flow rate or the target pressure to determine whether the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure.

28. A hydraulic fracturing system comprising: a plurality of hydraulic fracturing units, each of the hydraulic fracturing units including a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump;an input device configured to facilitate communication of operational parameters to a supervisory controller, the one or more operational parameters including one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead;one or more sensors configured to generate one or more sensor signals indicative of one or more of a flow rate of fracturing fluid or a pressure associated with fracturing fluid; anda supervisory controller in communication with one or more of the plurality of hydraulic fracturing units, the input device, or the one or more sensors, the supervisory controller being configured to: receive one or more operational parameters associated with pumping fracturing fluid into a wellhead, the one or more operational parameters including one or more of a target flow rate or a target pressure for fracturing fluid supplied to the wellhead;receive one or more signals indicative of a blender output upstream of the plurality of hydraulic fracturing units;determine whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressure;increase a flow rate from at least some of the hydraulic fracturing units according to a controlled increasing flow rate schedule toward the one or more of the target flow rate or the target pressure, the controlled increasing flow rate schedule including two or more different rates of change of flow rate corresponding to two or more wellhead pressure ranges;control operation of each of the at least some hydraulic fracturing units based at least in part on the one or more signals indicative of the blender output;determine, based at least in part on the one or more sensor signals indicative of one or more of the flow rate of fracturing fluid or the pressure associated with fracturing fluid, whether the at least some of the hydraulic fracturing units have achieved the one or more of the target flow rate or the target pressure; andone or more of: when it has been determined that the one or more of the target flow rate or the target pressure has been achieved, operate the at least some hydraulic fracturing units to maintain one or more of the target flow rate or the target pressure;when it has been determined that the target flow rate has not been achieved, generate one or more signals indicative of a failure to achieve the target flow rate; orwhen it has been determined that the target pressure has not been achieved, operate the at least some hydraulic fracturing units to maintain a maximum flow rate.

29. The hydraulic fracturing system of claim 28, wherein: the hydraulic fracturing units comprise a plurality of hydraulic fracturing pumps, each of the plurality of hydraulic fracturing pumps being associated with one of the plurality of hydraulic fracturing units;the supervisory controller is configured to: receive pump characteristics for each of the plurality of hydraulic fracturing pumps;determine a total pump flow rate by combining at least one of the pump characteristics for each of the plurality of hydraulic fracturing pumps; andcompare the total pump flow rate to the target flow rate to determine whether the plurality of hydraulic fracturing units have a capacity sufficient to achieve the one or more of the target flow rate or the target pressurethe plurality of pump characteristics comprises one or more of a minimum flow rate, a maximum flow rate, a harmonization range, and a pump condition for each of the plurality of hydraulic fracturing pumps; andthe supervisory controller is configured to add the maximum flow rates of each of the hydraulic fracturing pumps to determine the total pump flow rate.