This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting oil, natural gas, and other subterranean resources. Particularly, once a desired subterranean resource is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly through which the resource is extracted. These wellhead assemblies may include a wide variety of components, such as various casings, valves, fluid conduits, and the like, that control drilling or extraction operations.
Additionally, such wellhead assemblies may use a fracturing tree and other components to facilitate a fracturing process and stimulate production from a well. As will be appreciated, resources such as oil and natural gas are generally extracted from fissures or other cavities formed in various subterranean rock formations or strata. To facilitate extraction of such resources, a well may be subjected to a fracturing process that creates one or more man-made fractures in a rock formation. This facilitates, for example, coupling of pre-existing fissures and cavities, allowing oil, gas, or the like to flow into the wellbore. Such fracturing processes typically include injecting a fracturing fluid—often a mixture or slurry including sand and water—into the well to increase the well's pressure and form the man-made fractures.
Certain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
Embodiments of the present disclosure generally relate to simultaneous fracturing of multiple wells. In at least some instances, pumping fluid into two or more wells simultaneously to fracture those wells reduces total pumping time for fracturing wells at a pad site. In one embodiment, a fracturing system includes a manifold having valves to independently control flow rates of fracturing fluid to multiple wells. Fracturing fluid can be pumped through the manifold and into the multiple wells simultaneously, and the valves can be operated to balance the volume of fluid pumped into each well. A controller can also be used with the system to remotely actuate the manifold valves and control flow rates based on measured parameters and stored data.
Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter.
These and other features, aspects, and advantages of certain embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, any use of “top,” “bottom,” “above,” “below,” other directional terms, and variations of these terms is made for convenience, but does not require any particular orientation of the components.
Turning now to the present figures, an example of a fracturing system 10 is provided in
The fracturing fluid may, for example, include water (or another liquid) mixed with sand or some other proppants. The fracturing fluid is pumped into the formation 16 to extend fractures and fill them with the proppants, which operate to hold open the fractures after pumping has stopped to allow formation fluids to be more easily produced via the wells 12 and 14. In at least some embodiments, fracturing fluids used in the wells 12 and 14 also include other additives. For example, the fracturing fluid can include polymers or other agents to increase the viscosity of the fracturing fluid (which aids in carrying the proppants down the wells). And in some instances, the fracturing fluid includes acid (e.g., hydrochloric acid) that initiates fissures in the formation 16.
Although generally depicted as horizontal wells extending through the formation 16, the wells 12 and 14 could take other forms (e.g., vertical wells). In the presently illustrated embodiment, the wells 12 and 14 are surface wells formed at a common pad 20 and accessed through wellhead assemblies 18 installed at the wells. It will, of course, be appreciated that natural resources can be extracted from other types of wells, such as platform or subsea wells.
The fracturing system 10 also includes a fracturing supply system 22 coupled to the wellhead assemblies 18 by conduits 24 and 26 so as to provide fracturing fluid to the wells 12 and 14 via the conduits. In one embodiment, the fracturing supply system 22 includes various components depicted in block diagram 30 of
In at least some embodiments, such as that depicted in
The various sliding sleeves 38 of each well can be constructed for actuation by differently sized packer balls 42 and generally have seats with apertures that allow smaller balls 42 to pass through without actuating the sleeve. More specifically, the sliding sleeves 38 can be arranged in the wells in sequence by the size of the balls 42 used to actuate the sleeves, with the sleeves operated by the smallest balls provided furthest from the surface and the sleeves operated by the largest balls provided closest to the surface. In this arrangement, the smallest ball can dropped into a well and pass through the apertures in other sleeves before reaching (and actuating) the sleeve furthest from the surface. Balls of increasing size can then be sequentially dropped to actuate additional sleeves in the well, with the largest ball being the last dropped in order to actuate the sleeve closest to the surface. The sliding sleeves 38 can be placed between adjacent fracturing zones in the wells so that, as each ball 42 engages the seat of a corresponding sliding sleeve 38, the ball inhibits flow through the seat and isolates the fracturing zone associated with that actuated sleeve from other fracturing zones further down the well. To facilitate the sequential actuation of the sleeves 38, the conduits (e.g., conduits 24 and 26) connecting the ball launchers 40 to the wells 12 and 14 can be provided as single high-pressure lines (one to each well) having bores of sufficient size to allow the largest packer balls 42 to pass from the ball launchers 40 to the wells.
The system depicted in
Various components, collectively denoted with reference numeral 46 in
One or more blenders 54 are used to mix additives 58 into the fracturing fluid. While some other embodiments include a single blender 54, the system depicted in
In those embodiments having multiple blenders 54, and as illustrated in
Although any or all of the ball launchers 40, the output manifold valves 48, and the input manifold valves 56 could be actuated manually, in at least some embodiments these components are operated remotely by a controller. In
To reduce the amount of time needed to fracture wells on a shared pad, at least some embodiments of the present technique enable multiple wells to be fractured simultaneously. That is, fracturing fluid may be pumped into two or more wells at the same time to fracture rock surrounding the wells and stimulate well productivity. This is in contrast to other techniques, such as sequential fracturing of each well or other fracturing processes (e.g., zipper fracturing) in which two wells alternate between being prepared for fracturing and actually being fractured. The simultaneous fracturing techniques disclosed herein can be used to reduce, in some instances significantly, the amount of pumping time and associated costs for injecting fluid to fracture multiple wells compared to some previous approaches.
With this in mind, two processes for fracturing multiple wells (e.g., wells 12 and 14) are generally represented by flow charts 70 and 90 in
In the embodiment generally represented in
Fracturing multiple wells simultaneously reduces the amount of pumping time (and expense) needed to complete fracturing of wells at a pad. In at least some instances, operation of the fracturing system can be improved by controlling the individual flows of fracturing fluid to each well from the fracturing manifold 44. By way of example, the process generally represented in
The operating of the valves and dropping of balls represented by blocks 96 and 98 may be better understood with reference to
In at least some embodiments, including the process represented in
in which Vout is the volume of fracturing fluid output from the fracturing manifold 44, n is the number of wells being simultaneously fractured (two in the presently described embodiment, although a different number of wells may be simultaneously fractured in other embodiments), and V is the volume of fracturing fluid pumped into an individual well i. Given the relationship of flow volume to flow rate, the fluid distribution from the manifold 44 is also described by:
wherein Qi is the volumetric flow rate for well i.
In a simple case in which the wells 12 and 14 are identical in length, number of fracturing zones, and wellbore length of the fracturing zones, and also in which each fracturing zone is to receive the same amount of fracturing fluid, the fracturing fluid in the manifold 44 could be divided evenly by the output valves 48 so that each well 12 and 14 receives fracturing fluid at the same rate, such as twenty-five barrels (approximately 2980 liters) per minute, for an identical amount of time. More specifically, a desired amount of fracturing spear fluid (e.g., fifty barrels) can be provided to each well 12 and 14 simultaneously, such as by opening an input valve 56 to allow the spear fluid to enter the manifold 44 and opening output valves 48 such that equal amounts of the spear fluid enters each well. The input valves 56 can then be operated to stop flow of the spear fluid into the manifold and to permit flow of a proppant-laden fracturing fluid into the wells 12 and 14 in equal amounts. Once a given zone has been fractured, the next fracturing zone can be selected by dropping balls 42 into each of the wells to activate sliding sleeves 38 and the spear fluid and the proppant-laden fluid can be routed in the same way to the next fracturing zone. This may be repeated until all of the fracturing zones have been fractured.
But in practice there will typically be variation in one or more well or fracturing parameters (e.g., wells of different lengths or differences in fracturing zones). In such instances, fluid flow to the individual wells from the fracturing manifold 44 can be controlled through operation of the output valves 48. For example, if the well 12 were longer than the well 14, pumping fracturing fluid at the same rate into each well to fracture the lowest zones in each well (i.e., zones 104 and 114) and then dropping balls 42 into each well at the same time to select the next fracturing zones (i.e., zones 106 and 116) for each well would cause a greater volume of fracturing fluid to be pumped into the fracturing zone 104 than into the fracturing zone 114 (due to the increased volume of fracturing fluid in the well 12 compared to that in well 14 when the balls 42 are dropped).
In some embodiments, however, the volumes of fracturing fluid pumped into zones 104 and 114 are balanced by operating the output valves 48 to independently control flow to the wells and change the comparative flow rates of fracturing fluid into the wells 12 and 14. As noted above, the volume of fracturing fluid pumped into each well is equal to the product of the volumetric flow rate and the amount of time the fluid flows at that rate. Thus, the volume of fracturing fluid pumped into each well can be controlled by adjusting either the flow rate or the amount of time that the fluid is pumped. The greater volume of the well 12 (due to its increased length) can be accounted for as an offset to the amount of fluid that is to be pumped into well 12 from the manifold 44 to fracture zone 104 before dropping a ball 42 to select the next fracturing zone. For instance, if a casing string of the well 12 receiving the fracturing fluid has a volume that is greater than that of a similar casing string of well 14, the manifold output valves 48 can be operated to slow the flow (and reduce the volume) to the well 12 from the manifold 44 compared to the flow (and volume) to the well 14. Further, full flow (e.g., twenty-five barrels per minute) can be provided to the well 14 and a desired fracturing time for a given zone can be calculated based on:
V
frac
=Qt+V
p,
where Vfrac the volume of fracturing fluid to pump into the fracturing zone, Q is the volumetric flow rate at which fluid is pumped into the well 14 from the fracturing manifold 44, t is the desired fracturing time for the zone, and Vp is the volume of the passageway (i.e., fluid conduit) from the ball launcher 40 (of the well 14) to the far end of the zone being fractured.
Accordingly, in one embodiment a manifold valve 48 is opened to allow full flow of fracturing fluid, and the volumetric flow rate is measured via a sensor 62 (e.g., a flow meter) and input to the controller 60. The desired fracturing volume is provided to the controller 60 as initial data, and the volume of the passageway can also be provided as (or calculated from) initial data to the controller 60. Once the desired fracturing time is determined for zone 114, that time can be input into the same formula to calculate the appropriate flow rate (the only remaining variable) from the manifold 44 to the well 12 while fracturing the zone 104. (It is noted that the fracturing and passageway volumes for zone 104 can also be determined from initial data provided to the controller 60, but may differ from those for zone 114.) The manifold valve 48 that controls flow to the well 12 can then be adjusted to set the flow rate (which can be measured by a sensor 62) to the calculated amount. Once the desired fracturing time has elapsed, the ball launchers 40 may be activated to drop balls 42 into the wells 12 and 14 to isolate the next fracturing stages for stimulation. Each fracturing stage of corresponding pairs of stages (e.g., zones 106 and 116, zones 108 and 118, and zones 110 and 120) can be fractured at the same rate and for the same duration if desired, although the rates and durations could also be varied (e.g., if it is intended that the zones are to receive different volumes of fracturing fluid).
Although the above example describes balancing fluid distribution by slowing the flow rate into one well compared to another, in other embodiments the flow rates of both wells may be kept the same while the fracturing time is varied. For example, rather than slowing the flow rate of fluid from the manifold 44 to the well 12 for fracturing zone 104, the fracturing time could be reduced. That is, a valve 48 of the manifold could be closed once a desired volume of fracturing fluid has been pumped into the well 12 while additional fracturing fluid is pumped into well 14.
Various functionality described above (including, for example, determining desired flow rates and times for multiple wells and fracturing zones, operating the valves of the manifold to supply desired fluids at desired rates, and dropping balls into the wells to isolate fracturing zones) can be implemented with the controller 60 or with any other suitable controller. In at least some embodiments, such a controller is provided in the form of a processor-based system, an example of which is provided in
The system 130 also includes an interface 142 that enables communication between the processor 132 and various input or output devices 144. The interface 142 can include any suitable device that enables such communication, such as a modem or a serial port. The input and output devices 144 can include any number of suitable devices. For example, in one embodiment the devices 144 include the sensors 62 (
As previously noted, the fracturing manifold 44 facilitates control of fracturing fluid to multiple wells simultaneously. The fracturing manifold 44 can be provided in any suitable form, and examples of forms the manifold 44 could take are generally depicted in
Activation of a ball launcher (whether provided as, or connected to, the ball drop device 160) to drop balls 42 is also controlled by the controller 60 in some embodiments. To drop balls simultaneously into multiple wells, the valves 164 and 166 can be initially closed. A first ball can be dropped into the manifold 150 and one of the valves 164 and 166 can be briefly opened to advance the first ball a short distance downstream from the opened valve. Once that valve is closed, a second ball can be dropped into the manifold 150 and the other valve can be opened to advance the second ball downstream from that valve. Both valves 164 and 166 can then be opened to flow the balls into their respective wells (via conduits 154 and 156).
The manifolds of
In
While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.