Related Applications

[001] The present application claims the benefit of United States Provisional Patent Application Serial No. 63/388,508 filed July 12, 2022 entitled, “Improved External Recirculation for Gas Lock Relief,” the disclosure of which is herein incorporated by reference.

Field of the Invention

[002] This invention relates generally to the field of downhole pumping systems, and more particularly to systems and methods for alleviating gas lock in submersible pumping systems.

Background

[003] Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, a submersible pumping system includes a number of components, including an electric motor coupled to one or more pump assemblies. Production tubing is connected to the pump assemblies to deliver the wellbore fluids from the subterranean reservoir to a storage facility on the surface. In many cases, the pump assemblies are multistage centrifugal pumps that include a plurality of stages, with each stage including a stationary diffuser and a rotary impeller that is connected to a shaft driven by the electric motor.

[004] Wellbore fluids often contain a combination of liquids and gases. Because most downhole pumping equipment is primarily designed to recover liquids, excess amounts of gas in the wellbore fluid can present problems for downhole equipment. For the centrifugal pump to operate, the pump must maintain its “prime,” in which fluid is located in and around the “eye,” or central intake portion, of the first impeller of the pump or gas separator. If, for example, a gas slug moves through the well to the pump intake, the pump may lose its prime and will thereafter be unable to pump liquids while gas remains around the eye of the impeller.

LOO5J The pump can be re-primed by moving fluids to the intake for the first impeller. Once the impeller is provided with a sufficient volume of liquid to displace the trapped gas, the pump will begin pumping against to clear the gas slug through the pump. While it is known in the art to provide self-priming centrifugal pumps, many of these rely on a fluid storage chamber or reservoir to provide fluid for re-priming. Other self-priming pumps rely on recirculation valves within the pump or production tubing to divert fluids to the pump intake in the event the pump loses prime. Although generally successful, the incorporation of recirculation valves within the pump or production tubing may increase pressure losses through the valve. Additionally, the placement of recirculation valves in the discharge flow of submersible pumping systems may cause the accelerated erosion of the recirculation valve from sand and other solid particles present in the high-pressure fluid discharge.

[006] There is, therefore, a continued need for an improved system for re-priming a submersible centrifugal pump. It is to these and other deficiencies in the prior art that the disclosed embodiments are directed.

Summary of the Invention

[007] In one aspect, the present disclosure is directed to a submersible pumping system for producing a fluid from a wellbore through production tubing to a wellhead. The pumping system includes a pump assembly that has least one pump, a motor that drives the at least one pump, and a recirculation module configured to deliver a volume of priming fluid from the production tubing to the pump assembly. The recirculation module includes a recirculation mandrel positioned within the production tubing, a recirculation valve offset from the recirculation mandrel, and a recirculation line extending from the recirculation valve to the pump assembly.

[008] In another aspect, the present disclosure is directed to a submersible pumping system for producing a fluid from a wellbore through production tubing to a wellhead. The submersible pumping system includes a pump assembly that has at least one pump, a motor that drives the at least one pump, and a recirculation module. The recirculation module includes a recirculation mandrel positioned within the production tubing and a first recirculation line extending to the pump assembly. The recirculation module is configured to deliver a volume of priming fluid from the production tubing to the pump assembly.

[009] In yet another aspect, the present disclosure provides for a submersible pumping system for producing a fluid from a wellbore through production tubing to a wellhead. The pumping system includes a pump assembly that has at least one pump, a motor that drives the at least one pump, and a recirculation module. The recirculation module includes a recirculation mandrel positioned within the production tubing, a first recirculation line, and a second recirculation line. The recirculation module delivers a volume of priming fluid from the production tubing to the pump assembly through the first and second recirculation lines.

Brief Description of the Drawings

[010] FIG. 1 is an elevational view of an electric submersible pumping system disposed in a wellbore constructed in accordance with an embodiment of the present disclosure.

[Oi l] FIG. 2 provides a cross-sectional depiction of a first embodiment of the recirculation assembly connected to a submersible pump assembly. [012] FIG. 3 provides a cross-sectional depiction of a second embodiment of the recirculation assembly connected to a submersible pump assembly.

[013] FIG. 4 provides a cross-sectional depiction of a third embodiment of the recirculation assembly connected to a submersible pump assembly.

[014] FIG. 5 provides a cross-sectional depiction of a fourth embodiment of the recirculation assembly connected to a submersible pump assembly.

[015] FIG. 6 provides a cross-sectional depiction of a fifth embodiment of the recirculation assembly connected to a submersible pump assembly.

[016] FIG. 7A-7C provide depictions of additional configurations of the recirculation assembly connected to a submersible pumping system.

Written Description

[017] As used herein, the term "petroleum" refers broadly to all mineral hydrocarbons, such as crude oil, gas and combinations of oil and gas. The term “two- phase” refers to a fluid that includes a mixture of gases and liquids. It will be appreciated by those of skill in the art that, in the dow nhole environment, a two-phase fluid may also carry solids and suspensions. Accordingly, as used herein, the term “two-phase” not exclusive of fluids that contain liquids, gases, solids, or other intermediary forms of matter.

[018] FIG. 1 shows an elevational view of a pumping system 100 attached to production tubing 102. The pumping system 100 and production tubing 102 are disposed in a wellbore 104, which is drilled for the production of a fluid such as water or petroleum. The production tubing 102 connects the pumping system 100 to a wellhead 106 located on the surface. Although the pumping system 100 is primarily designed to pump petroleum products, it will be understood that the present invention can also be used to move other fluids. It will also be understood that, although each of the components of the pumping system are primarily disclosed in a submersible application, some or all of these components can also be used in surface pumping operations.

[019] For the purposes of the disclosure herein, the terms “upstream” and “downstream” shall be used to refer to the relative positions of components or portions of components with respect to the general flow of fluids produced from the wellbore. “Upstream” refers to a position or component that is passed earlier than a “downstream” position or component as fluid is produced from the wellbore 104. The terms “upstream” and “downstream” are not necessarily dependent on the relative vertical orientation of a component or position. It will be appreciated that many of the components in the pumping system 100 are substantially cylindrical and have a common longitudinal axis that extends through the center of the elongated cylinder and a radius extending from the longitudinal axis to an outer circumference. Objects and motion may be described in terms of radial positions within discrete components in the pumping system 100.

[020] The pumping system 100 includes some combination of a pump assembly 108, a motor 110, and a seal section 112. The seal section 112 shields the motor 110 from mechanical thrust produced by the pump assembly 108 and provides for the expansion of motor lubricants during operation. As illustrated in FIG. 1, the pump assembly 108 may include two or more separate pumps 114 that are each connected to one another. In the embodiment depicted in FIG. 1, the pump assembly 108 includes a plurality of multistage centrifugal pumps 114a, 114b connected together in a serial (end-to-end) relationship.

[021] The pump assembly 108 optionally includes a gas separator 116 positioned upstream from the pumps 114. The gas separator 116 can be connected between the seal section 112 and the first (upstream) pump 114. During use, two-phase wellbore fluids are drawn into the gas separator 116, which encourages the separation of gaseous components from the liquid components. The gaseous components are ejected into the annulus of the wellbore 104, while the liquid components are carried to the first pump 114 in the pump assembly 108. It will be understood that the components of the gas separator 116 may be integrated into one of the pumps 114 rather than presented as a separate component. It will be further understood that in certain embodiments, the pump assembly 108 may include multiple gas separators 116, which may be connected together in a tandem configuration.

[022] The pumping system 100 also includes a recirculation module 118 between the discharge of the downstream pump 114 and the production tubing 102. In some embodiments, the recirculation module 118 includes a recirculation mandrel 120, a recirculation valve 122, a recirculation valve inlet 124 and a recirculation line 126. Generally, the recirculation valve 122 is configured to automatically open when a gas lock condition occurs (e.g., in the pump assembly 108) to provide a volume of liquid to re-prime the affected component of the pump assembly 108. The recirculation valve 122 can be configured as a standard check valve that includes a moveable valve member 122a that is biased in a closed position against a valve seat 122b by a spring or other biasing element 122c. When the pressure supplied by the pump assembly 108 drops below a threshold established by the biasing element 122c, the recirculation valve opens 122, permitting liquid from the production tubing 102 to pass through the recirculation valve 122 to the recirculation line 126, which delivers the liquid necessary to re-prime the pump assembly 108.

[023] Importantly, the recirculation valve 122 is positioned adjacent to the primary flow path between the pump assembly 108 and the production tubing 102. Removing the recirculation valve 122 from the primary flow path for the produced fluids reduces the pressure drop that would otherwise be caused by the placement of a diverter valve in this location.

[024] As explained below, the recirculation module 118 can be configured in a variety of embodiments to better control the placement of fluid from the recirculation module 118 into the appropriate component within the pump assembly 108. Although the recirculation line 126 depicted in FIG. 1 shows a discharge of priming fluid from the recirculation module 118 to an intake of the gas separator 116, it will be appreciated that the depiction of the pumping system 100 in FIG. 1 is merely exemplary and should not be construed as a limiting embodiment. In some embodiments, multiple recirculation lines 126 are used to convey priming fluid to the same or different parts of the pump assembly 108. As used in this application, the term “priming fluid” refers to fluid directed by the recirculation module 118 from the production tubing to the pump assembly 108.

[025] Turning to FIG. 2, shown therein is a first embodiment in which the recirculation module 118 is connected within the pumping system 100. In this embodiment, the pump assembly 108 includes three pumps 114a, 114b, 114c that are connected together in a serial manner. Each pump 114 includes an intake 128 and a discharge 130. The intake 128 can be configured to receive fluid from the wellbore 104, or from the discharge 130 from an upstream pump 114.

[026] In the embodiment depicted in FIG. 2, the recirculation mandrel 120 is located between joints of the production tubing 102, above (or downstream) from the pump assembly 108. In this embodiment, the recirculation line 126 of the recirculation module 118 is configured to discharge fluid between the discharge 130a of the upstream pump 114a and the intake 128b of the intermediate pump 114b. In this way, when the recirculation valve 122 opens, produced fluids from the production tubing

102 are directed to the intake 128b of the intermediate pump 114b to re-prime the pump assembly 108.

[027] Turning to FIG. 3, shown therein is a second embodiment in which the recirculation module 118 is connected within the pumping system 100 such that the recirculation line 126 is connected to the pump assembly 108 a location downstream from the first pressure-inducing stage. For example, the recirculation line 126 can be connected to the outlet of the first (upstream) impeller of the upstream pump 114a. Alternatively, the recirculation line 126 can be connected to a downstream side of the gas separator 116 if the gas separator 116 is present in the pumping system 100.

[028] Turning to FIG. 4, shown therein is a third embodiment in which the recirculation module 118 is connected within the pumping system 100 such that the recirculation mandrel 120 is located within the production tubing 102 at a distance (D) downstream from the pump assembly 108 that is selected to minimize the adverse effects caused by abrasive particulates entrained in the produced, high-pressure fluid. In some embodiments, the distance (D) is greater than the length of the pump assembly 108. In other embodiments, the distance (D) is about the same as the length of the pump assembly 108, about half the length of the pump assembly, about one- quarter the length of the pump assembly 108, or less than one-quarter the length of the pump assembly 108.

[029] Turning to FIG. 5, shown therein is a fourth embodiment in which the recirculation module 118 includes a directional nozzle 132 that controls the flow of priming fluid into the pump assembly 108. In exemplary embodiments, the directional nozzle 132 can be a bent or angled tubing that injects the priming fluid from the recirculation module 118 into the pump assembly 108 in a manner that encourages the flow of fluid into, and along a common path with, fluid entering the pump assembly 108 from the wellbore 104.

L030J Turning to FIG. 6, shown therein is a fifth embodiment in which the recirculation module 118 includes an eductor assembly 134 for passing the pruning fluid into the pump assembly 108. The eductor assembly 134 includes an eductor housing 136 is connected to, or integral with, the 128a of the upstream pump 114a. The eductor housing 136 can include a tapered internal profile with a throat 136a that encourages the acceleration of fluid passing through the eductor housing 136. In other embodiments, the eductor housing 136 could be connected to, or made integral with, another component within the pump assembly 108. The eductor assembly 134 includes an eductor discharge 138 that is connected to the recirculation line 126. The eductor discharge 138 is coaxial with the eductor housing 136. In this way, the priming fluid injected into the eductor housing 136 creates a jet-induced low pressure region within the eductor housing 136 that encourages fluids from the wellbore 104 to be drawn into the pump assembly 108 according to the Venturi principle. The accelerated priming fluid better mixes with any gases in the wellbore fluid to mitigate large bubbles or pockets of gas that might otherwise contribute to a gas locked condition.

[031] Additionally, the discharge of priming fluid from the eductor assembly 134 is also directed into the center of the pump assembly 108, which aids in the cooling of the shaft bearings in the pump assembly 108. When the pump assembly 108 loses prime, the wellbore fluids that would ordinarily cool and lubricate tungsten carbide and other bearings in the pump assembly 108 are not present, which can lead to the accelerated wear and thermal shock of these bearing components. In this way, the eductor assembly 134 applies a Venturi pumping action that also provides a cooling and lubricating function to the tungsten carbide bearings within the pump assembly 108.

L032J Turning to FIGS. 7A-7C, shown therein are additional embodiments in which the recirculation module 118 is connected to the pump assembly 108. In FIG. 7A, the recirculation line 126 is connected between the optional recirculation valve 122 and the discharge portion of a middle gas separator 116b connected between upstream and downstream gas separators 116a, 116b connected in a tandem configuration. In FIG. 7B, the recirculation line 126 branches between the optional recirculation valve 122 and the discharge side of the middle and upstream gas separators 116b, 116a which again are connected in tandem. FIG. 7C depicts yet another embodiment in which two separate recirculation lines 126 are connected between the pump assembly 108 and corresponding recirculation valves 122, which are also optional in this embodiment. The first recirculation line 126 connects between an upstream pump 114a and a downstream pump 114b. The second recirculation line connects between the optional recirculation valve 122 and the discharge end of the middle gas separator 116b.

[033] It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, in some embodiments, it may be possible to omit the recirculation valve 122, or integrate it into the recirculation mandrel 120. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.