Forward extrusion type check valve and complex working condition oil well electric submersible pump oil pipe forward extrusion well washing method

Abstract

The invention discloses a forward extrusion type check valve and a complex working condition oil well electric submersible pump oil pipe forward extrusion well washing method. A forward extrusion type check valve is mounted at the upper end of a pump outlet of the electric submersible pump; pressure is applied through an oil pipe, so that the forward extrusion type check valve is opened or closed in a well washing mode, and a forward extrusion channel is established; the flushing fluid is pumped into the well through a forward extrusion channel, so that the flushing fluid forcibly flows through an internal flow channel of the electric submersible pump to dissolve and wash scales, wax deposits and other sediments in the pump; a reverse circulation soaking channel is established, and blockages near a suction inlet are soaked and loosened; and forward extrusion cleaning is executed again or synchronously, and the loosened blockages are further scoured through forward liquid flow. According to the invention, all-around and three-dimensional cleaning of the electric submersible pump unit from the upper part to the lower part of the pump and from the internal flow channel to the suction inlet is realized, the device is particularly suitable for the plug removal operation of an electric submersible pump well with complex working conditions such as serious wax precipitation, scaling or sand production, the plug removal is thorough, and the construction is safe and efficient.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and in particular to a positive-squeeze single-flow valve and a method for positive-squeeze well cleaning of oil well tubing using an electric submersible pump under complex operating conditions. Background Technology

[0002] Electric submersible pumps (ESPs), as highly efficient artificial lift devices, are widely used in high-yield liquid wells and offshore platforms. However, during production, factors such as crude oil properties, formation water characteristics, and production regimes can easily lead to problems like wax buildup, inorganic scale deposition, and formation sand production in oil wells and ESP systems. These deposits and solid particles can clog the pump's flow channels, impellers, pump inlet, and screen pipe, resulting in increased ESP load, decreased operating efficiency, and abnormal operating current. In severe cases, this can even cause the pump to seize up or burn out, necessitating periodic or emergency well cleaning and unclogging maintenance.

[0003] Currently, the conventional circulation well-washing method is mainly used for the well-washing operation of electric submersible pump wells, but it has significant defects: (1) Reverse circulation well-washing method: The well-washing fluid is injected from the annular space between the tubing and the casing (the annulus) and returns from the tubing. The fatal flaw of this method is that the well-washing fluid flow is completely blocked by the electric submersible pump unit (especially the conventional check valve at the pump outlet), and cannot flow down through the pump body, resulting in the blockages in the tubing, suction port and near the bottom of the well being completely unable to be cleaned, and the well-washing effect is extremely incomplete. (2) Conventional forward circulation well-washing method: The well-washing fluid is injected from the tubing and returns from the annulus. Although this method can force the well-washing fluid to flow through the inside of the electric submersible pump, when dealing with complex conditions such as high viscosity crude oil, dense wax deposits or large amounts of sand, the return channel (annulus) is easily blocked by large pieces of wax or sand particles washed down, causing the annulus pressure to rise sharply. More importantly, in order to maintain circulation, the pressure of the fluid column inside the wellbore often far exceeds the formation pressure. This can easily force loose or dissolved harmful substances such as wax, scale, and sand in the wellbore into the deep pores and fractures of the oil and gas producing layer under high pressure differential, causing serious and irreversible reservoir damage (secondary pollution), making it difficult to restore production after well washing or even causing a permanent decline.

[0004] In summary, the existing technology lacks a well-washing method that can safely and thoroughly clean the electric submersible pump unit and the entire wellbore, while effectively avoiding damage to the oil and gas producing formation. This has become a technical bottleneck restricting the long-term, efficient and stable production of electric submersible pump wells under complex operating conditions. Summary of the Invention

[0005] This invention addresses the technical challenges of existing well-washing technologies, which, due to the internal structure of the electric submersible pump (ESP), especially the traditional check valve, cannot thoroughly clean the pump's internal flow channels and downhole, and also struggle to handle pump inlet blockage. It provides a forward-flow check valve and a forward-flow well-washing method for ESPs in complex operating conditions. The check valve in this invention integrates a forward circulation flushing channel while retaining a reliable one-way shut-off function. This allows for forward circulation well-washing operations when needed, effectively removing deposited impurities from the pump and resolving inlet blockage. Furthermore, it automatically and reliably seals after flushing, eliminating the need to disassemble the tubing string, making operation safe and simple. This invention offers significant advantages for unblocking ESP wells under complex conditions such as severe wax buildup, scaling, or sand production, providing thorough unblocking and ensuring safe and efficient operation.

[0006] In a first aspect, the present invention provides a positively extruded single-flow valve, which is achieved by the following technical solution.

[0007] A positive-squeeze type single-flow valve includes a housing, with a lower connector and an upper connector connected to both ends of the housing, respectively. A check valve seat is provided inside the housing, and a spring is provided between the check valve seat and the lower connector, the spring forming a seal between the check valve seat and the upper connector. A valve core is provided on the check valve seat, and a straightening rod is connected to the end of the valve core away from the check valve seat. A return spring is sleeved on the straightening rod, and the unused end of the straightening rod passes through a guide frame.

[0008] Furthermore, a liner is also provided inside the housing.

[0009] Furthermore, the lower connector is threaded to an external thread transport cap.

[0010] Furthermore, the upper connector is threaded to an internally threaded transport cap.

[0011] Furthermore, the flow guide is connected to the upper connector via a retaining ring through a hole.

[0012] Secondly, the present invention provides a method for positive squeezing and washing well tubing with an electric submersible pump under complex working conditions, which is achieved by the following technical solution.

[0013] A method for positive-force flushing of tubing in an ESP (Electric Submersible Pump) well under complex operating conditions includes the following steps: S1. Install a forward-applied check valve: Install the above-mentioned forward-applied check valve at the upper end of the pump outlet of the electric submersible pump; S2. Establish a positive cleaning channel: Apply pressure through the tubing to open or conduct the positive squeeze single-flow valve in well washing mode, and establish a positive squeezing channel from the tubing to the internal flow channel of the electric submersible pump, the downhole tubing, and the formation. S3. Forward extrusion cleaning: Through the forward extrusion channel, the cleaning fluid is pumped into the well, forcing the cleaning fluid to flow through the impeller, guide shell, and pump outlet valve of the electric submersible pump, dissolving and flushing the scale, wax and other deposits inside the pump. S4. Combined backwashing and forward washing to unblock: Establish a reverse circulation soaking channel from the annulus to the pump inlet, the screen pipe / formation below the pump, and the tubing. First, soak and loosen the blockages near the inlet. Then, perform forward squeezing cleaning in step S3 again or simultaneously, using the forward liquid flow to further flush away the loosened blockages.

[0014] By adopting the above technical solution, the valve has dual working modes: First production mode: During normal well production or pump shutdown, its function is exactly the same as a traditional check valve, effectively preventing liquid backflow and protecting the ESP unit; Second well-washing mode: When implementing well-washing methods, the valve can be opened forward or bypassed under certain control pressure, thus overcoming the absolute obstruction of well-washing fluid flow by traditional check valves. Based on this valve, this application adopts a strategy combining "tubing forward extrusion" and "annular backwashing": Tubing forward extrusion cleans foreign objects in the pump impeller, guide casing, and other flow channels; a controllable reverse circulation is established to address blockages near the pump inlet and screen pipe.

[0015] Furthermore, in step S2, the applied oil pipe pressure is greater than the force of the spring, and the check valve seat opens, forming a flow channel from top to bottom.

[0016] Furthermore, in step S3, the pressure of the well-washing fluid is greater than the force of the spring, keeping the check valve seat in the open state. The outer periphery of the check valve seat is provided with uniformly distributed flow holes, and the well-washing fluid enters the valve's internal flow channel through the flow holes to achieve continuous flushing of the pump and suction port.

[0017] Furthermore, in step S4, the reverse circulation soaking channel is established by injecting soaking liquid into the annulus while controlling the oil pipe pressure to be lower than the opening pressure of the forward squeeze check valve, so that the soaking liquid enters through the pump inlet and soaks the area below the pump; after soaking for a certain period of time, the oil pipe pressure is increased to reopen the forward squeeze check valve for forward squeeze cleaning, forming a synergistic unblocking process of soaking-loosening-forward flushing.

[0018] This application has the following beneficial effects: (1) High-efficiency sand and jam prevention: By regularly or as needed, positive circulation flushing can effectively remove sand and scale inside the pump and blockages in the suction port, prevent unit failures caused by valve not closing tightly, unit jamming and suction port blockage, and extend the pump inspection cycle.

[0019] (2) Safe and easy to operate: Forward circulation flushing does not affect motor cooling and is safer than reverse circulation. The flushing valve can be switched on and off by wireline operation or ground control, eliminating the need for expensive well workover operations and saving costs and time.

[0020] (3) Self-closing reliability: After flushing, the spring automatically resets and locks, and the valve core resets under the action of the reset spring, ensuring no backflow when the pump stops, and high reliability.

[0021] (4) Compact structure: The integrated design does not affect the original tubular structure and can directly replace the conventional single-flow valve, making it easy to promote and apply. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the positive-explosion single-flow valve of the present invention.

[0023] Among them, 1-external threaded transport cap, 2-lower connector, 3-shell, 4-liner, 5-spring, 6-check valve seat, 7-valve core, 8-reset spring, 9-upper connector, 10-guide frame, 11-hole elastic retaining ring, 12-internal threaded transport cap, 13-straightening rod. Detailed Implementation

[0024] The present patent application will be further described below with reference to the accompanying drawings and embodiments.

[0025] like Figure 1 As shown, a positive-explosion type single-flow valve includes an externally threaded transport cap 1, a lower connector 2, a housing 3, a liner 4, a spring 5, a check valve seat 6, a valve core 7, a return spring 8, an upper connector 9, a flow guide 10, an elastic retaining ring for the bore 11, an internally threaded transport cap 12, and a straightening rod 13.

[0026] The internal threaded transport cap 12 is threadedly connected to the upper connector 9. One end of the housing 3 is fixedly connected to the upper connector 9, and the other end of the housing 3 is fixedly connected to the lower connector 2. The lower connector 2 is threadedly connected to the external threaded transport cap 1. The spring 5, check valve seat 6, valve core 7, return spring 8, flow guide 10, and straightening rod 13 are arranged inside the housing 3, the upper connector 9, and the lower connector 2.

[0027] A check valve seat 6 is provided above the lower connector 2. A spring 5 is provided between the lower connector 2 and the check valve seat 6. The spring 5 causes the check valve seat 6 to abut against the lower end inclined surface of the upper connector 9, so that the check valve seat 6 and the upper connector 9 form a seal.

[0028] One end of the valve core 7 mates with the check valve seat 6, and the other end of the valve core 7 is fixedly connected to the centralizing rod 13 by a nut. A return spring 8 is mounted on the centralizing rod 13, and the other end of the centralizing rod 13 passes through the guide frame 10. The guide frame 10 is fixed to the upper connector 9 through a hole using an elastic retaining ring 11. Under the action of the return spring 8, the valve core 7 forms a seal with the check valve seat 6. When the submersible pump is running, the valve core 7 is pushed open by the pressure of the oil, and the oil reaches the wellhead through the tubing. When the submersible pump stops, the return spring 8 pushes the valve core 7 back to the check valve seat 6, thus preventing backflow.

[0029] This invention also provides a method for positive-squeeze well flushing of oil well tubing using an electric submersible pump under complex operating conditions, comprising the following steps: (1) Install a positive squeeze check valve: Install a positive squeeze check valve at the upper end of the pump outlet of the electric submersible pump; (2) Establish a positive cleaning channel: Apply pressure through the tubing to open or conduct the positive squeeze single-flow valve in the well washing mode, and establish a positive squeezing channel from the tubing to the internal flow channel of the electric submersible pump, the pump string, and the formation; at this time, the applied tubing pressure is greater than the force of the spring 5, and the check valve seat 6 opens to form a flow channel from top to bottom. (3) Positive squeezing cleaning: Through the positive squeezing channel, the cleaning fluid is pumped into the well, so that the cleaning fluid is forced to flow through the internal flow channels of the electric submersible pump impeller, guide shell, pump outlet valve, etc., to dissolve and flush the scale, wax and other deposits in the pump; at this time, the pressure of the cleaning fluid is greater than the force of the spring 5, keeping the check valve seat 6 in the open state. The outer periphery of the check valve seat 6 is provided with uniformly distributed flow holes, and the cleaning fluid can enter the valve flow channel through the flow holes to achieve continuous flushing of the pump and suction port.

[0030] (4) Combined backwashing and forward washing to unblock: Establish a reverse circulation soaking channel from the annulus to the pump inlet, the screen pipe / formation under the pump, and the tubing. First, soak and loosen the blockage near the inlet. Then, by switching or combining the control process, perform or simultaneously perform the forward squeezing cleaning of step (3) again. Use the forward liquid flow to further flush the loosened blockage and solve the problem of blockage at the inlet. The reverse circulation soaking channel is established by injecting soaking liquid into the annulus while controlling the oil pipe pressure to be lower than the opening pressure of the forward squeeze check valve, so that the soaking liquid enters through the pump inlet and soaks the area below the pump; after soaking for a certain period of time, the oil pipe pressure is increased to reopen the forward squeeze check valve for forward squeeze cleaning, forming a coordinated unblocking process of "soaking-loosening-forward flushing".

[0031] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A positive-explosion type single-flow valve, comprising a housing (3), wherein a lower connector (2) and an upper connector (9) are respectively connected to both ends of the housing (3), characterized in that: A check valve seat (6) is provided inside the housing (3). A spring (5) is provided between the check valve seat (6) and the lower connector (2). The spring (5) forms a seal between the check valve seat (6) and the upper connector (9). A valve core (7) is provided on the check valve seat (6). The end of the valve core (7) away from the check valve seat (6) is connected to a straightening rod (13). A reset spring (8) is sleeved on the straightening rod (13). The unused end of the straightening rod (13) passes through the guide frame (10).

2. The positive-explosion type single-flow valve according to claim 1, characterized in that: The housing (3) is also provided with a liner (4).

3. The positive-explosion type one-way valve according to claim 1, characterized in that: The lower connector (2) is threaded to the external thread transport cap (1).

4. The positive-explosion type single-flow valve according to claim 1, characterized in that: The upper connector (9) is threaded to the internal thread transport cap (12).

5. A positive-explosion type single-flow valve according to claim 1, characterized in that: The flow guide (10) is connected to the upper connector (9) through a hole using an elastic retaining ring (11).

6. A method for positive-force well flushing with an electric submersible pump tubing under complex operating conditions, characterized in that: Includes the following steps: S1. Install a positively extruded check valve: Install the positively extruded check valve as described in any one of claims 1-5 at the upper end of the pump outlet of the electric submersible pump; S2. Establish a positive cleaning channel: Apply pressure through the tubing to open or conduct the positive squeeze single-flow valve in well washing mode, and establish a positive squeezing channel from the tubing to the internal flow channel of the electric submersible pump, the downhole tubing, and the formation. S3. Forward extrusion cleaning: Through the forward extrusion channel, the cleaning fluid is pumped into the well, forcing the cleaning fluid to flow through the impeller, guide shell, and pump outlet valve of the electric submersible pump, dissolving and flushing the scale, wax and other deposits inside the pump. S4. Combined backwashing and forward washing to unblock: Establish a reverse circulation soaking channel from the annulus to the pump inlet, the screen pipe / formation below the pump, and the tubing. First, soak and loosen the blockages near the inlet. Then, perform forward squeezing cleaning in step S3 again or simultaneously, using the forward liquid flow to further flush away the loosened blockages.

7. The method for positive-squeeze well flushing with an electric submersible pump tubing under complex operating conditions according to claim 6, characterized in that: In step S2, the applied oil pipe pressure is greater than the force of the spring (5), and the check valve seat (6) opens, forming a flow channel from top to bottom.

8. A method for flushing oil wells under complex operating conditions using an electric submersible pump tubing, as described in claim 6, is characterized in that: In step S3, the pressure of the well washing fluid is greater than the force of the spring (5), keeping the check valve seat (6) in the open state. The outer periphery of the check valve seat (6) is provided with uniformly distributed flow holes. The well washing fluid enters the valve internal flow channel through the flow holes to achieve continuous flushing of the pump and suction port.

9. A method for positive-force well flushing with an electric submersible pump tubing under complex operating conditions, as described in claim 6, is characterized in that: In step S4, the reverse circulation soaking channel is established by injecting soaking liquid into the annulus while controlling the oil pipe pressure to be lower than the opening pressure of the forward squeeze check valve, so that the soaking liquid enters through the pump inlet and soaks the area below the pump; after soaking for a certain period of time, the oil pipe pressure is increased to reopen the forward squeeze check valve for forward squeeze cleaning, forming a synergistic unblocking process of soaking-loosening-forward flushing.

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