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.
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.
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.
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.
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.
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.
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.
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.
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 downhole 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.
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.
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
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.
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.
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.
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
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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.
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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.
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/388,508 filed Jul. 12, 2022 entitled, “Improved External Recirculation for Gas Lock Relief,” the disclosure of which is herein incorporated by reference.
Number | Date | Country | |
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63388508 | Jul 2022 | US |