Patent Application
20190331117
The present invention relates generally to power systems for pumping assemblies used for well servicing applications, most particularly powering pumping assemblies used for well fracturing operations with an electric motor and a variable frequency drive (VFD).
Oil and gas wells require services such as fracturing, acidizing, cementing, sand control, well control and circulation operations. All of these services require pumps for pumping fluid down the well. The type of pump that has customarily been used in the industry for many years is a gear driven plunger type, which may be referred to as a “frac pump.” The pump is often powered by a diesel engine, typically 2,000 bhp or larger, that transfers its power to a large automatic transmission. The automatic transmission then transfers the power through a large driveline, into a gear reduction box mounted on the frac pump. The frac pump has a crankshaft mounted in a housing. A plunger has a crosshead that is reciprocally carried in a cylinder perpendicular to the crankshaft. A connecting rod connects each eccentric portion or journal of the crankshaft to the plunger. The driveline enters the frac pump at a right angle to the connecting rods, plungers and pump discharge. A typical pump might be, for example, a triplex type having three cylinders, three connecting rods, and three journals on the crankshaft. An example of a common type of a well service pump (e.g., plunger pump) is disclosed in U.S. Pat. No. 2,766,701 to Giraudeau. These pumps will typically be mounted on a trailer or skid back-to-back.
Some frac pumps use an electric motor to supply power to the frac pump instead of a diesel engine. While an electric motor is more efficient in supplying power to the frac pump and does not need to be refueled, the electric motor requires a plurality of variable frequency drive (VFD) to vary the motor speed for different power applications, specifically supplying power to each of the hydraulic pumps of the frac pump. Each VFD can control the amount of current and/or voltage supplied to the electric motor to ensure that maximum current is not always applied to the motor, thereby increasing the life of the motor. Supplying the maximum horsepower of the motor is not needed for all power applications, especially when starting up a hydraulic pump from a resting position to a threshold operating speed. In current electric motor frac pumps, each hydraulic pump requires its own VFD. However, using multiple VFDs increases the cost and complexity of the frac pump.
For these and other reasons, a need continues to exist for improvements in oil and gas well servicing pumps of the type under consideration.
The present disclosure includes embodiments of pump systems and methods.
In some embodiments of the present disclosure, a system for powering a pump includes a plurality of hydraulic pumps; an electric motor configured to power the plurality of pumps; a variable frequency drive (VFD) configured to be coupled to the electric motor to control an amplitude of power provided by the electric motor to the plurality of pumps; and a control system configured to control, for each of the plurality of pumps, the VFD between: a first state, wherein the pump is powered by the electric motor and the amplitude of power provided by the electric motor to the pump is controlled by the VFD; and a second state, wherein the pump is powered by the electric motor and the amplitude of power provided by the electric motor to the pump is not controlled by the VFD. In some embodiments, the electric motor is a fixed speed electric motor. In some embodiments, the system further includes at least one electric generator coupled to the electric motor.
In some embodiments, the control system includes, for each of the plurality of pumps, an electric circuit having: a VFD flow path that, in the first state, allows the VFD to control the amplitude of power provided by the electric motor to the pump; and a bypass flow path that, in the second state, allows the electric motor to provide power to the pump directly. In some embodiments, the electric circuit includes a plurality of switches actuatable to selectively permit electricity to flow through the VFD flow path and the bypass flow path. In some embodiments, the control system is configured to control, for each of the plurality of pumps, the plurality of switches. In some embodiments, at least one of the plurality of switches is operated between: an ON state that permits electricity to flow between the VFD and the pump; and an OFF state that blocks electricity flow between the VFD and the pump. In some embodiments, the hydraulic pumps are variable flow rate pumps.
In some embodiments, the pumps are fixed displacement pumps. In some embodiments, the hydraulic pumps are coupled to a pump drive and a plurality of ram cylinders. In some embodiments, each of the hydraulic ram cylinders is coupled to a respective one of the plurality of pumps. In some embodiments, each of the hydraulic ram cylinders and the electric motor are disposed on a first vehicle. In some embodiments, the VFD is disposed on a second vehicle.
In some embodiments, the system further includes: at least one working fluid end cylinder having an end cylinder housing, a plunger rod configured to reciprocate in the end cylinder housing; at least one inlet check valve coupled to the end cylinder housing and at least one outlet check valve coupled to the end cylinder housing; a suction manifold having at least one fluid inlet coupled to the at least one inlet check valve; and a discharge manifold having at least one fluid outlet coupled to the at least one outlet check valve. In some embodiments, each of the hydraulic ram cylinders has a ram cylinder housing, a ram piston configured to reciprocate in the ram cylinder housing, and a piston rod coupled to the ram piston and the plunger rod of the at least one working fluid end cylinder such that the piston is actuated to move the plunger rod: in a first direction to expel working fluid from the end cylinder housing during a forward stroke of the plunger rod, and in a second direction to draw working fluid into the end cylinder housing during a return stroke of the plunger rod.
In some embodiments of the present disclosure, a method of powering a pump system includes: operating an electric motor configured to power the plurality of pumps; and operating, by a control system coupled to a variable frequency drive (VFD) and configured to control, for each of the plurality of pumps, the VFD, where the VFD is coupled to the electric motor to control an amplitude of power provided by the electric motor to the plurality of pumps. In some embodiments, the operating the VFD includes: coupling, by the control system, the VFD to one of the pumps while decoupling the VFD from the other pumps; actuating a first state, wherein the pump is powered by the electric motor and the amplitude of power provided by the electric motor to the pump is controlled by the VFD, on the one of the pumps coupled to the VFD; decoupling the VFD from the one of the pumps; actuating a second state, wherein the pump is powered by the electric motor and the amplitude of power provided by the electric motor to the pump is not controlled by the VFD; coupling the VFD to one of the other pumps; actuating the first state on the one of the other pumps coupled to the VFD; decoupling the VFD from the one of the other pumps; and actuating the second state on the one of the other pumps.
In some embodiments, actuating the first state includes actuating a VFD flow path that, in the first state, permits electricity to flow through the VFD flow path and allows the VFD to control the amplitude of power provided by the electric motor to the pump. In some embodiments, actuating the VFD flow path includes: transmitting, by the control system coupled to a plurality of switches, an ON signal to one of the switches, where each switch couples one of the pumps to the VFD; switching the one of the switches to an ON state, where the ON state connects the one of the variable flow rate pumps to the VFD; and transmitting, by the control system when the one of the switches is ON, an OFF signal to each of the other switches.
In some embodiments, actuating the second state includes actuating a bypass flow path that, in the second state, permits electricity to flow through the bypass flow path allows the electric motor to provide power to the pump directly. In some embodiments, actuating the bypass flow path includes: transmitting, by the control system, an OFF signal to the one of the switches; switching the one of the switches to an OFF state, where the OFF state disconnects the one of the pumps from the VFD; transmitting, by the control system, an ON signal to a bypass switch coupled in series between the electric motor and the one of the pumps and in parallel with the VFD; and switching the bypass switch to an ON state, where the ON state connects the one of the pumps to the electric motor.
The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically; two items that are “coupled” may be unitary with each other. The terms “a” and “an” are defined as one or more unless this disclosure explicitly requires otherwise. The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the terms “substantially,” “approximately,” and “about” may be substituted with “within [a percentage] of” what is specified, where the percentage includes 0.1, 1, 5, and 10 percent.
Further, a device or system that is configured in a certain way is configured in at least that way, but it can also be configured in other ways than those specifically described.
The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”), and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, an apparatus that “comprises,” “has,” “includes,” or “contains” one or more elements possesses those one or more elements, but is not limited to possessing only those elements. Likewise, a method that “comprises,” “has,” “includes,” or “contains” one or more steps possesses those one or more steps, but is not limited to possessing only those one or more steps.
Any embodiment of any of the apparatuses, systems, and methods can consist of or consist essentially of—rather than comprise/include/contain/have—any of the described steps, elements, and/or features. Thus, in any of the claims, the term “consisting of” or “consisting essentially of” can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb.
The feature or features of one embodiment may be applied to other embodiments, even though not described or illustrated, unless expressly prohibited by this disclosure or the nature of the embodiments.
Some details associated with the embodiments described above and others are described below.
The following drawings illustrate by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. Identical reference numbers do not necessarily indicate an identical structure. Rather, the same reference number may be used to indicate a similar feature or a feature with similar functionality, as may non-identical reference numbers. The figures are drawn to scale (unless otherwise noted), meaning the sizes of the depicted elements are accurate relative to each other for at least the embodiment depicted in the figures.
In the embodiment shown, system 200 includes a cooler 204 coupled to a hydraulic fluid reservoir 208. In the embodiment shown, cooler 204 includes a fan and a fan motor for cooling the hydraulic fluid used in operating the pump system 200. For example, cooler 204 can remove 600 HP at 270 GPM, maintain a 125° F. inlet temperature, and have a weight of 3,991 pounds. In some embodiments, the fan motor specifications are 20 HP, 480 V, 3 φ, 22.7 A, TEFC, and 1800 RPM but other suitable fan motors can be used. Hydraulic fluid reservoir 208 stores the hydraulic fluid used to operate the pump system 200 and can be any suitable size and type. For example, hydraulic fluid reservoir 208 can be a sealed, stainless steel tank having an internal bladder that can store 400 gallons of fluid volume.
In the embodiment shown, an electric motor 212 is provided to create and supply drive power to the pump assemblies of system 200.
Electric motor 212 is coupled to a single variable frequency drive (VFD) 216 and a pump drive 220.
In the embodiment shown, pump drive 220 supplies power from electric motor 212 to drive hydraulic pumps 224 of system 200. Pump drive 220 is coupled to hydraulic pumps 224 via a plurality of pump pads. In the embodiment shown, pump drive 220 has eight pump pads with four pads on each face of pump drive 220. The power capacity of each pump pad can be over 1200 HP although pads with other suitable power capacities can be used. Pump drive 220 supplies power to hydraulic pumps 224 at a drive speed ratio 1:1 with electric motor 212. In the embodiment shown, hydraulic pumps 224 have specifications of 750 cc, 6200 psi, 350 GPM, and 1800 RPM, although other suitable hydraulic pumps 224 can be used. In the embodiment shown, hydraulic pumps 224 are mounted directly onto pump drive 220. Hydraulic fluid can be pumped from hydraulic pumps 224 to the main well pumping assembly via hydraulic fluid outlets 256. In the embodiment shown, hydraulic pumps 224 are variable flow rate pumps enabled to permit adjustment of the rate at which hydraulic fluid is delivered to hydraulic ram cylinders 228, and thus, the rate at which the hydraulic ram cylinders are actuated. In the embodiment shown, the well pump assembly of system 200 includes hydraulic ram cylinders 228, connection cylinders 232, working fluid end cylinders 236, suction manifold 240, and discharge manifold 244.
In the embodiment shown, each hydraulic ram cylinder 228 is connected to a working fluid pump end cylinder 236. In this embodiment, working fluid pump end cylinders 236 include an end cylinder housing and a plunger rod configured to reciprocate in the end cylinder housing. In this embodiment, hydraulic ram cylinder 228 includes a ram cylinder housing and a ram piston configured to reciprocate in the ram cylinder housing. In some embodiments, each pump assembly is supported on the trailer by a plurality of vibration-dampening mounts. The piston rod is coupled to the ram piston and the plunger rod such that ram piston can be actuated to move the plunger rod in a first direction to expel working fluid from the end cylinder housing during a forward stroke of the plunger rod, and in a second direction to draw working fluid into the end cylinder housing during a return stroke of the plunger rod.
In the embodiment shown, each working fluid pump end cylinder 236 includes an inlet check valve coupled to an end cylinder housing and configured to permit working fluid to be drawn into the end cylinder housing but prevent working fluid from exiting the end cylinder housing through the inlet check valve. In operation of the system, the inlet check valve prevents working fluid from exiting through the fluid inlet thereby enabling working fluid to be pressurized in the cylinder and directed solely to the well. In this embodiment, each working fluid end cylinder 236 further includes an outlet check valve coupled to the end cylinder housing and configured to permit working fluid to exit the end cylinder housing while preventing working fluid from being drawn into the end cylinder housing. In operation of the system, the outlet check valve prevents working fluid pressurized downstream of the outlet check (e.g., in the outlet manifold described below) valve from entering the cylinder housing during the return stroke of plunger rod (e.g., during the forward stroke of other working fluid pump assemblies). The outlet check valve and inlet check valve may, in some embodiments, be at least partially in the end cylinder housing.
In the embodiment shown, system 200 further includes a suction manifold 240 coupled to the inlet check valves and inlet passages of each working fluid pump end cylinder 236; and a discharge manifold 244 coupled to the outlet check valves and outlet passages of the working fluid pump end cylinder 236. In this embodiment, suction manifold 240 includes a plurality of inlet flow channels each coupled to a different one of the working fluid pump end cylinders 236 via the corresponding inlet check valve and inlet flow channel. In this embodiment, each inlet flow channel has a cross-sectional area at least as large as the cross-sectional area of the interior of the working fluid end cylinder to which the inlet flow channel is coupled.
In the embodiment shown, system 200 also comprises a valve system coupled to the reservoir 208 via hydraulic pumps 224 and to each hydraulic ram cylinder 228 of each of the working fluid pump assemblies to direct pressurized working fluid to and from the hydraulic ram cylinders. In this embodiment, system 200 also comprises a control system 132 coupled to the valve system and configured to sequentially actuate the hydraulic ram cylinders 228 to deliver (e.g., continuous and substantially pulseless) output flow of the working fluid from the pump system to the well.
In the embodiment shown, control system 132 comprises one or more processors and/or a programmable logic controllers (PLCs) configured to sequentially actuate working fluid pump end cylinders 236 (i.e., via hydraulic ram cylinders 228). In most embodiments, the present systems are configured to actuate the pump assemblies such that at least one of the pump assemblies is performing a forward stroke at any given point in time (e.g., such that the hydraulic ram cylinder of a first one of the working fluid pump assemblies is beginning its forward stroke as the hydraulic ram cylinder of a second one of the working fluid pump assemblies is ending its forward stroke). For example, in an embodiment with only two pump assemblies, the first pump assembly would perform its forward stroke as the second pump assembly performs its return stroke of the same duration. In an embodiment with pump assemblies included in a multiple of three (e.g., six) the pump assemblies are controlled as two groups of three.
As mentioned above, a valve system can be operably associated with each hydraulic ram cylinder 228 for delivering driving fluid to each hydraulic ram cylinder at a driving pressure. Control system 132 is provided for operating the valve system to alternately pressurize each hydraulic ram cylinder on a forward stroke thereof and to depressurize the hydraulic ram cylinder on a return stroke thereof to thereby deliver a continuous and pulseless output flow of the working fluid from the working fluid end cylinders to the well.
In some embodiments, the system includes a directional control valve connected to the source of driving fluid and movable between a pressurizing position which admits driving fluid for pressurizing a respective ram cylinder at the beginning of its forward stroke and for exhausting the respective ram cylinder during its return stroke. In addition to the use of directional control valves, the present systems may also include one or more proportional control valves (sometimes called proportional throttle valves). The directional control valve controls the direction of the flow of the hydraulic fluid. In one position, it allows a hydraulic ram cylinder to charge and in the other position it allows the ram piston to return. A proportional control valve component of the system can be computer controlled to provide real time, exact control of the position of the respective ram piston rod. In some embodiments, for example, this can allow the system to have one ram piston accelerating one ram half way thru its travel while another ram decelerates, to closely approximate the timing of a current crankshaft design.
Hydraulic ram cylinder 228 has an internal diameter and internal cylindrical sidewalls, a piston (not shown in
Control system 132 is also coupled to pump drive 220. In the embodiment shown, pump drive 220 is directly coupled to each of hydraulic pumps 224 and is configured to selectively supply power to each hydraulic pump 224. Pump drive 220 includes a plurality of switches that can be toggled between an “ON” and “OFF” state to permit and block a hydraulic pump 224 from receiving power from motor 212 via VFD 216. In the embodiment shown, VFD 216 is a single VFD that regulates power for all the hydraulic pumps via pump drive 220. This single VFD configuration saves costs by eliminating the need for each hydraulic pump to be regulated by its own VFD. When performing a slow start process on hydraulic pumps 224, control system 132 toggles the plurality of switches in such a way as to connect a single hydraulic pump 224 to pump drive 220 and VFD 216 at a time while leaving the other hydraulic pumps connected to the pump drive unaffected. Control system 132 can toggle the switches in a sequential fashion such that the VFD 216 ramps up the speed of a first hydraulic pump 224, and, after the connected hydraulic pump 224 reaches operating speed, the VFD is operably disconnected from the first pump and the VFD is operably connected to a second hydraulic pump 224 and the ramp-up/disconnect procedure is repeated for the second pump. The ramp-up/disconnect procedure can be repeated any number of times for any suitable number of pumps 224. The sequential fashion can constitute connecting the hydraulic pumps in a sequential order from right to left or left to right as disposed on the trailer. The sequential fashion can also constitute connecting the hydraulic pumps in a random order. Once the hydraulic pump is up to operating speed and disconnected from VFD 216, it is directly connected to electric motor 212 via pump drive 220 to receive power at a constant rate sufficient to maintain the threshold operating speed.
In the embodiment shown, system 200 includes one or more sensors that monitor the speed of the hydraulic pumps 224. The sensor(s) of the present systems (e.g., 200) can comprise any suitable sensor, such as, for example, a pump speed sensor, current sensor, voltage sensor, and/or the like that is capable of sensing a power state and/or a speed of the hydraulic pumps 224. By way of example, in the embodiment shown, the sensor(s) may be configured to capture data indicative of parameters such as pressure, flow rate, temperature, and/or the like of hydraulic fluid within the hydraulic pumps 224. The sensor(s) may also be configured to capture data indicative of parameters such as the amount of current, voltage, and/or the like supplied to the electric motor. Data captured by the sensor(s) may be transmitted to control system 132. In some embodiments, a system (e.g., 200) may include a memory configured to store data captured by the sensor(s).
In the embodiment shown, control system 132 includes at least one processor configured to control VFD 216 and pump drive 220. For example, in the depicted embodiment, the processor(s) may transmit commands to VFD 216 to regulate electric motor 212 to supply power to pump drive 220 and a particular hydraulic pump 224 at levels to efficiently and safely perform a soft start process on hydraulic pump 224. Similarly, the processor(s) may transmit commands to the switching components of pump drive 220 to couple and decouple the hydraulic pumps 224 from the electric motor 212 and VFD 216. In the depicted embodiment, control of the switching components of pump drive 220 by the processor(s) may be facilitated by data captured by the sensor(s).
Each hydraulic pump 224 will have its own switch 264 and bypass switch 268. During a soft start operation, switch 264 is turned ON to enable hydraulic pump 224 to receive an amplitude of power gradually in a ramp up manner from VFD 212. As hydraulic pump 224 moves from a cold state to an operating speed, VFD 216 ramps up the power supplied to hydraulic pump 224 until it reaches an operating speed. At this point, switch 264 is turned OFF to disconnect hydraulic pump 224 from VFD 212 and bypass switch 268 is turned ON to enable hydraulic pump 224 to receive an amplitude of power directly from electric motor 212. Electric motor 212 operates at a constant speed that supplied sufficient horsepower to maintain hydraulic pump 224 at operating speed. Once the hydraulic pump 224 is at operating speed it is connected to electric motor 212 via bypass switch 268 and the motor continues to power the pump, without the help of the VFD, from that time onward or until the pump is turned off. Control system 132 actuates the switching components in the same manner for the next hydraulic pump. In this way, control system 132 sequentially actuates a soft start process in each of the hydraulic pumps by connecting one hydraulic pump at a time to VFD 216. In this manner, a single VFD 416 can actuate each hydraulic pump instead of providing a separate VFD for each hydraulic pump.
The above specification and examples provide a complete description of the structure and use of illustrative embodiments. Although certain embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. As such, the various illustrative embodiments of the methods and systems are not intended to be limited to the particular forms disclosed. Rather, they include all modifications and alternatives falling within the scope of the claims, and embodiments other than the one shown may include some or all of the features of the depicted embodiment. For example, elements may be omitted or combined as a unitary structure, and/or connections may be substituted. Further, where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and/or functions, and addressing the same or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. For example, embodiments of the present methods and systems may be practiced and/or implemented using different structural configurations, materials, ionically conductive media, monitoring methods, and/or control methods.
The claims are not intended to include, and should not be interpreted to include, means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively.
This application claims priority to U.S. Provisional Application No. 62/664,078, filed Apr. 27, 2018, the entire contents of which application are specifically incorporated by reference herein without disclaimer.
| Number | Date | Country | |
|---|---|---|---|
| 62664078 | Apr 2018 | US |
