Patent ID: 12247463

DETAILED DESCRIPTION

Certain embodiments commensurate in scope with the present disclosure are summarized below. These embodiments are not intended to limit the scope of the disclosure, but rather these embodiments are intended only to provide a brief summary of certain disclosed embodiments. Indeed, the present disclosure may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

As used herein, the term “coupled” or “coupled to” may indicate establishing either a direct or indirect connection (e.g., where the connection may not include or include intermediate or intervening components between those coupled), and is not limited to either unless expressly referenced as such. The term “set” may refer to one or more items. Wherever possible, like or identical reference numerals are used in the figures to identify common or the same elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale for purposes of clarification.

Furthermore, when introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” 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. Additionally, it should be understood that references to “one embodiment,” “an embodiment,” or “some embodiments” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, the phrase A “based on” B is intended to mean that A is at least partially based on B. Moreover, unless expressly stated otherwise, the term “or” is intended to be inclusive (e.g., logical OR) and not exclusive (e.g., logical XOR). In other words, the phrase A “or” B is intended to mean A, B, or both A and B.

Hydrocarbon fluids, such as oil and natural gas, may be obtained from subterranean or subsea geologic formations, referred to as reservoirs, by drilling one or more wells that penetrates the hydrocarbon-bearing geologic formation. In subsea applications, various types of infrastructure may be positioned along a sea floor to aid in retrieving the hydrocarbon fluids. In some embodiments, hydrocarbon recovery may be enhanced by fluid injection systems that pump fluid (e.g., water) into the reservoir to maintain and/or increase pressure within the reservoir, thereby maintaining or increasing the hydrocarbon fluid pressure at production wells. As such, by maintaining or increasing the pressure within the reservoir, a rate of extraction of the hydrocarbon fluids may be maintained or increased.

In some embodiments, and particularly in subsea applications, an abundance of seawater may provide easy and convenient access to fluid for injection. However, prior to injecting seawater or another fluid into the reservoir, the fluid may be treated (e.g., filtered or otherwise processed) prior to being pumped into the reservoir. For example, it may be desirable to remove sulfates or other contaminates from the fluid prior to injection into the reservoir to, among other reasons, reduce a risk of crystallization of sulfates in the reservoir, which may affect hydrocarbon production.

In some embodiments, separate pumps may be utilized for facilitating filtering the fluid (i.e., a filter pump) and injecting the fluid (i.e., injection pump) into the reservoir. The pumps may be driven by one or more motors (e.g., electric motors) to pump the fluid through one or more filters (e.g., for treatment) and facilitate injection of the fluid into the reservoir. However, additional motors may increase cost of manufacture, implementation (e.g., installation), and utilization (e.g., electricity usage) of the subsea injection system. As such, in some disclosed embodiments, a single motor may drive both the filter pump and the injection pump.

Furthermore, in some scenarios, a barrier fluid may be used to protect and/or cool the motor and act as a lubricant in internal components, such as bearings and mechanical seals (e.g., seals between the motor and one or more pumps). The barrier fluid may be pressurized to a higher level than the pumped/process fluid such that the barrier fluid serves to form a “barrier” between the process fluid and other areas of the pump, such as the motor. Due to the higher pressure, there may be a consumption, or “leakage,” of barrier fluid into the process fluid across mechanical seals of the pump/motor assembly.

In some scenarios, it may be desired to reduce or eliminate barrier fluid in the process fluid. For example, as the fluid (e.g., seawater) is treated via the filters, barrier fluid may negatively affect the effectiveness of the filters (e.g., by clogging or damaging filter membranes). Additionally, wastewater from the treatment process may be expelled to the environment, and it may be desirable to minimize or eliminate the expulsion of barrier fluid to the environment. As such, in some embodiments, the filter pump may be driven via an indirect (e.g., electromagnetic) coupling to the motor, such that there is no barrier fluid crossover to the process fluid and, therefore, no barrier fluid expelled to the environment. For example, the filter pump may be mechanically and/or fluidly isolated from the motor, but still driven via an electromagnetic coupling. Moreover, in some embodiments, a single electric motor may directly or indirectly drive the injection pump while also indirectly (e.g., via an electromagnetic coupling) driving the filter pump to allow for a simplified, cost- and energy-efficient filter and injection system that reduces or eliminates barrier fluid in the wastewater to the seawater environment.

With the foregoing in mind,FIG.1is a schematic view of a subsea injection system10including an injection well12, a wellhead14, and a subsea station16, according to embodiments of the present disclosure. The subsea station16and wellhead14are generally disposed on the seafloor18, and the injection well12may penetrate the seafloor18and extend into a reservoir20. The subsea station16may include one or more pumps, motors (e.g., electric motors), and/or a controller22to pressurize seawater24for injection into the reservoir20. By injecting the seawater24or other fluid into the reservoir20, the pressure within the reservoir20may be maintained or increased to facilitate extraction of hydrocarbons from the reservoir20at a production well (not shown). In some embodiments, the subsea station16may be connected to an umbilical26, which may supply fluids (e.g., barrier fluids, injection fluids, etc.), power, control signals, etc., to the subsea station16. In some embodiments, the umbilical26may connect the subsea station16to a platform28on the surface of the seawater24. As should be appreciated, the umbilical26may connect the subsea station16to other facilities such as a floating production, storage and offloading unit (FPSO), a shore-based facility, or other subsea systems. Furthermore, the subsea station16may be coupled to the wellhead14via pipes30(e.g., high pressure pipes) for injecting pressurized fluid (e.g., seawater24) into the reservoir20. Moreover, in some embodiments, the pumps and motors of the subsea injection system10may be implemented on the platform28or otherwise on the surface, and the pipes may bring the pressurized seawater24to the wellhead14from the surface.

Although a single injection well12and subsea station16are shown inFIG.1, as should be appreciated, the subsea injection system10may include multiple subsea stations16and/or injection wells12. For example, in some embodiments, a subsea station16may pressurize seawater24for injection into multiple (e.g., two, three, four, and so on) different injection wells12. In such embodiments, the controller22may regulate valves of the subsea station16to direct pressurized injection fluid into the multiple injection wells12individually or simultaneously.

As stated above, by injecting fluid into the reservoir20, the pressure within the reservoir20may be maintained or increased to facilitate hydrocarbon extraction. For example, the removal of hydrocarbons from the reservoir20(e.g., via a production well) may decrease the pressure within the reservoir20, which, in turn, may reduce the rate of hydrocarbon extraction. As such, by pressurizing (e.g., increasing or maintaining the pressure of) the reservoir with other (e.g., non-reservoir) fluids (e.g., seawater24), the rate of hydrocarbon extraction may be maintained or increased.

As seawater24is readily available in the subsea environment, seawater24may be utilized as an injection fluid. However, seawater24may include impurities such as particles, algae, oxygen and/or sulfates. As such, treatment (e.g., filtration) of the seawater24may be performed prior to injection into the reservoir20.FIG.2is a schematic diagram of a portion32of the subsea injection system10, which may be included in the subsea station16, according to embodiments of the present disclosure. To treat the seawater24prior to injection, one or more filter stages34. For example, the filter stages34may include an inlet strainer36, a particle filter38, a micro-filter40, and/or a nano-filter42as described in U.S. Pat. No. 10,160,662, which is incorporated herein by reference.

In some embodiments, the inlet strainer36prevents large objects, such as fish, rocks, and/or waterborne debris, from proceeding to the particle filter38. The particle filter38may prevent small objects, such as mud and sand, from proceeding to the micro-filter40, and the micro-filter40may filter particles larger than 0.1 micron, 1 micron, 10 microns, and so on, from the seawater24, depending on implementation. In some embodiments, the nano-filter42may filter sulfates and/or dissolved salt from the seawater24. By removing sulfates, a likelihood of crystallization of the sulfates and/or scaling in the reservoir20(which may lead to decreased hydrocarbon production) may be reduced. As should be appreciated, the filter stages34described above are given as examples and, as such, are non-limiting. Fewer or additional filter stages34may be included depending on implementation.

To motivate the flow of seawater24through the filter stages34and into the reservoir20, a combined pump44may be utilized having at least one injection pump46and at least one filter pump48. The combined pump44may use a single motor50to drive both the injection pump46and the filter pump48. The motor50may be any suitable type of motor (e.g., electric motor) capable of adequately operating both the injection pump46and the filter pump48. For example, the motor50may be a permanent magnet motor, a canned stator motor, or a barrier fluid-less motor.

In some embodiments, the nano-filter42may output a permeation flow52and a rejection flow54. The permeation flow52may be a portion of seawater24that has been treated by the filter stages34and may proceed to the injection pump46for injection into the reservoir20. On the other hand, the rejection flow54may include the sulfates and/or salts filtered from the input seawater24that are to be returned to the environmental seawater24. As stated above, the filter stages34are given as examples, and the permeation flow52and rejection flow54of the nano-filter42are likewise given as examples of filtered flows and waste flows, respectively. The filter pump48may be driven by the motor50to facilitate the rejection flow54to the environmental. However, as stated above, motors directly coupled (e.g., physically coupled, such as by using physical components, including gears, shafts, couplings, and the like) to a pump may leak barrier fluid into the process flow. In some embodiments, to avoid barrier fluid in the rejection flow54returning to the sea24, the filter pump48may be mechanically and fluidly sealed (e.g., hermetically sealed) from the motor50. In the absence of a mechanical coupling between the filter pump48and the motor50, the filter pump48may be driven via an indirect coupling56(e.g., without physical coupling), such as an electromagnetic coupling.

In some embodiments, the same motor50that indirectly drives the filter pump48may also drive, directly or indirectly, the injection pump46. The injection pump46may pressurize the permeation flow52for injection into the reservoir20. In some embodiments, the permeation flow52may also include a recirculation flow58, for example, to facilitate flow regulation via one or more valves60and/or to prevent overpressurization or cavitation. For example, in some scenarios, the injection pump46may cavitate if the flowrate through the injection pump46is below a threshold rate. Using the recirculation flow58, the flowrate may through the injection pump46may be increased. Furthermore, in some embodiments, the flowrates of the filter pump48and the injection pump46may be about the same (e.g., within 10 percent, within 5 percent, within 1 percent, and so on) or based on a set ratio depending on the permeation flow52and rejection flow54characteristics of the nano-filter42and/or the backpressure of the reservoir20.

Additionally, in some embodiments, one or more of the filter stages34(e.g., the particle filter38, the micro-filter40, and/or the nano-filter42) may be coupled to a backwash flowline61to flush or otherwise clean the filter stages34of the filtered contaminants/debris. For example, the filter stages34may include one or more valves to direct the incoming seawater24in a reversed flow (relative to the flow of normal operation) through the filter stages34such that the previously filtered contaminants/debris is flushed though the backwash flowline61. In some embodiments, the filter pump48and/or one or more ejector pumps (not shown) may motivate the flow through the backwash flowline61. Additionally, the backwash operation, including valve regulation, may be monitored (e.g., via one or more sensors within or near the filter stages34) and/or controlled by the controller22.

In some embodiments, the controller22may include one or more processors and memory to facilitate operation of the subsea injection system10. For example, the controller22may receive information from one or more sensors62(e.g., pressure sensor(s)62A, temperature sensor(s)62B, flow sensor(s)62C, and/or other sensors) and regulate operation of the valve(s)60, filter pump48, injection pump46, and/or motor50. Moreover, while discussed above as being disposed at the subsea station16, the controller22may be implemented at the platform28or any other suitable location for controlling operations of the subsea injection system10. As should be appreciated, the processor(s) may be implemented with any combination of general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGAs), programmable logic devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entities that may perform calculations or other manipulations of information. Moreover, the processor may be implemented as one of multiple processors that work in conjunction with each other to perform the various functions described herein. Furthermore, the processor may be operably coupled with the memory to execute various algorithms stored in the memory to perform the functions described herein. The memory may include any suitable non-transitory medium for storing data and executable instructions, such as random-access memory, read-only memory, rewritable flash memory, hard drives, and optical discs.

Additionally, in some embodiments, desired chemicals may be injected into the subsea injection system10at any suitable point (e.g., downstream of one or more filtering stages34, upstream or downstream of the injection pump46, etc.) depending on the characteristics of the reservoir20and/or the desired water quality. Such chemicals may include, but are not limited, to organic biocide, bio dispersant/surfactant, scale inhibitors, calcium nitrate, oxygen scavenger, surfactant enhanced oil recovery (EOR), polymer inhibitor, and/or microbial EOR.

FIG.3is a schematic diagram of the combined pump44, according to embodiments of the present disclosure. As stated above, the combined pump44includes an injection pump46, which may be directly (e.g., mechanically coupled) to the motor50. As used herein, a pump directly coupled to the motor50includes a mechanical coupling of the motor shaft66and the impellers of the pump. The injection pump46may include a single or multistage pump (e.g., 2, 5, 10, or more stages) for pressurizing the permeation flow52. Additionally, the motor50may include a barrier fluid inlet64to receive/replenish barrier fluid that may have leaked into the permeation flow52. In some embodiments, the motor50may also drive the filter pump48via an indirect coupling56(e.g., electromagnetic coupling). For example, the shaft66of the motor50may have one or more coils68disposed thereon, and a rotor70of the filter pump48may have opposing coils72disposed thereon. As the shaft66spins, the coils68generate an electromagnetic field that induces the rotor70to spin, via the opposing coils72. Furthermore, a seal74(e.g., hermetic seal) may be made between the shaft66of the motor50and the rotor70of the filter pump48to reduce or eliminate leakage of barrier fluid into the rejection flow54. As such, the combined pump44may drive both the rejection flow54and the permeation flow52using a single motor50without leaking barrier fluid into the rejection flow54.

In some embodiments, the filter pump48, injection pump46, and motor50may be housed in a single housing with inlets and outlets for the respective seawater flows. Moreover, in some embodiments, the injection pump46and motor50may be housed together while the filter pump48is separately housed. For example, the seal74may formed by the housing of the injection pump46and motor50and/or by the housing of the filter pump48.

Although the filter pump48is shown inFIG.2as being disposed downstream or after the nano-filter42, as should be appreciated, different configurations and/or additional pumps (e.g., additional filter pumps and/or injection pumps) may also be used depending on implementation. For example,FIGS.4-7are schematic diagrams of different example configurations of the portion32of the subsea injection system10, according to embodiments of the present disclosure. For example, the filter pump48may be upstream or downstream of the nano-filter42. Moreover, the filter pump48and/or injection pump46may run in series or parallel with respective auxiliary pumps. As shown inFIG.4, an auxiliary injection pump76driven by an auxiliary motor78may be implemented to further increase the pressure of the permeation flow52prior to injection into the reservoir20. In some scenarios, increased pressure may be needed to counter pressure drops/deficiencies related to the water depth at the seafloor18, line loss of the pipes30, and/or other factors.

Moreover, in some embodiments, the rejection flow54may be utilized as part of a backwash process and/or to clean the particle filter38and/or micro-filter40before being expelled to the environmental seawater24. Additionally or alternatively, the particle filter38and/or the micro-filter40may be self-cleaning (e.g., backwashed using one or more ejector pumps80to expel wastewater back to the sea) to increase a lifespan of the particle filter38and/or the micro-filter40.

Further, as shown inFIG.5, the configuration of the filter pump48and the nano-filter42may be changed such that the filter pump48is upstream of the nano-filter42. As no barrier fluid is leaked into the process flow of the filter pump48, the seawater24entering the nano-filter downstream of the filter pump48is also free of barrier fluid, so as to not clog or damage the nano-filter42. In such an embodiment, the filter pump48may receive both filtered and rejected seawater (e.g., as the nano-filter42may serve to separate the two), and the indirect coupling56and/or filter pump48may be increased (e.g., in size) accordingly.

Additionally, as shown inFIG.6, the filter pump48may be disposed upstream of the nano-filter42and multiple (e.g., two) injection pumps46(including auxiliary injection pump76) (e.g., coupled in series) driven by multiple (e.g., two) respective motors (including auxiliary motor78) may be implemented to further increase the pressure of the permeation flow52prior to injection into the reservoir20. Furthermore, as shown inFIG.7, a second combined pump82may be implemented having an auxiliary injection pump76, an auxiliary motor78, and an auxiliary filter pump84. As illustrated, the second combined pump82may be couple in series with the first combined pump44. For example, a first injection pump46of the first combined pump44may be coupled to a second injection pump76of the second combined pump82, while a first filter pump48of the first combined pump44may be coupled to a second filter pump84of the second combined pump82. Moreover, in some embodiments, the filter pumps (e.g., filter pump48and auxiliary filter pump84) and/or injection pumps (e.g., injection pump46and auxiliary injection pump76) may be implemented in parallel. For example, flow path86may allow the filter pump48and the auxiliary filter pump84to operate in parallel, and the output of the auxiliary filter pump84may feed into or circumvent (e.g., via flow path88) the filter pump48, depending on implementation. The second combined pump82may be implemented to further increase the seawater pressures within the subsea injection system10and/or as backups to the combined pump44.

As should be appreciated, any suitable combination or arrangement of pumps and motors may be used depending on implementation. Furthermore, although discussed herein as being utilized with a motor50coupled to the injection pump46, the filter pump48may be indirectly coupled (e.g., electromagnetically coupled) to any suitable motor, which may or may not be coupled, directly or indirectly, to any another pump. Additionally or alternatively, the additional pumps (e.g., auxiliary filter pump76and/or auxiliary injection pump76) may be driven by the single motor50of the combined pump44, such as in a “back-to-back” arrangement, as described in U.S. Pat. No. 10,859,084, which is incorporated herein by reference. For example, the injection pump46and auxiliary injection pump76may be driven in the back-to-back arrangement, and a shaft (e.g., motor shaft66or a shaft of either injection pump driven by the motor shaft66) may extend beyond the impellers of one or both injection pumps to indirectly couple to one or more filter pumps48.

FIG.8is a flowchart of an example process90utilizing the subsea injection system10and combined pump44, according to embodiments of the present disclosure. Seawater24may be retrieved from the environment (process block92) and filtered via one or more filter stages34(process block94). Additionally, the seawater24may be filtered by an additional filter stage34, such as a nano-filter42, that outputs a permeation flow52and a rejection flow54(process block96). The flow of seawater may be motivated through the nano-filter42by a filter pump48that is indirectly coupled to and sealed from a motor50(process block98). Additionally, the permeation flow52may be pressurized by an injection pump coupled (e.g., directly coupled) to the motor50(process block100). The high-pressure permeation flow52may be injected into the reservoir20and the rejection flow54may be returned to the environment (process block102).

The technical effects of the systems and methods described herein include a subsea injection system10with a combined pump44that reduces costs and increases efficiencies associated with manufacturing, implementation, and/or maintenance while maintaining a seal (e.g., hermetic seal) between the motor50and the rejection flow54such that barrier fluid is not expelled to the environment. Furthermore, although the above referenced flowchart is shown in a given order, in certain embodiments, process blocks may be reordered, altered, deleted, and/or occur simultaneously. Additionally, the referenced flowchart is given as an illustrative tool and further decision and process blocks may also be added depending on implementation.

As used herein, the terms “inner” and “outer”; “up” and “down”; “upper” and “lower”; “upward” and “downward”; “above” and “below”; “inward” and “outward”; and other like terms as used herein refer to relative positions to one another and are not intended to denote a particular direction or spatial orientation. The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “in connection with,” and “connecting” refer to “in direct connection with” or “in connection with via one or more intermediate elements or members.”

The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. Moreover, the order in which the elements of the methods described herein are illustrated and described may be re-arranged, and/or two or more elements may occur simultaneously. The embodiments were chosen and described to best explain the principals of the disclosure and its practical applications, to thereby enable others skilled in the art to best utilize the disclosure and various embodiments with various modifications as are suited to the particular use contemplated.

Finally, the techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. § 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. § 112(f).