Integrated fracturing fluid drainage testing tubing and its construction method

Abstract

This invention relates to the field of oil and gas reservoir testing technology, and more particularly to an integrated fracturing and drainage testing string and its construction method, aiming to solve the technical problem that existing integrated fracturing and drainage testing strings cannot perform formation testing before and after fracturing. The circulation channel on the pump seat of this integrated fracturing and drainage testing string can be repeatedly opened and closed. When open, jet pump drainage testing can be performed; when closed, fracturing operations can be carried out. Formation testing before and after fracturing can be achieved without moving the string. By comparing the test data before and after fracturing, an objective evaluation of the fracturing effect can be made.

Description

Technical Field

[0001] This invention relates to the field of oil and gas reservoir testing technology, and in particular to an integrated fracturing and drainage testing string and its construction method. Background Technology

[0002] Currently, the main method for reservoir stimulation of oil and gas wells is sand fracturing, which aims to create fractures in the formation and fill them with sand particles for support, thereby improving the permeability of the reservoir and increasing oil and gas production.

[0003] Currently, commonly used integrated fracturing and fluid drainage strings include: tubing + fracturing packer, tubing + jet pump holder + fracturing packer, and tubing + jet pump holder + full-bore selective test valve + eccentric voltage support + fracturing packer. After fracturing, fluid is drained through coiled tubing or by deploying a jet pump. However, existing integrated fracturing and fluid drainage strings cannot perform formation testing before and after fracturing, thus making it impossible to provide an objective and timely evaluation of the fracturing effect. Summary of the Invention

[0004] The purpose of this invention is to provide an integrated fracturing fluid drainage testing string and its construction method, so as to solve the technical problem that existing integrated fracturing fluid drainage strings cannot perform formation testing before and after fracturing of reservoirs.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] In a first aspect, the present invention provides an integrated tubing string for fracturing fluid drainage testing, comprising: tubing, pump base, pump core, and pressure gauge;

[0007] The pump base is disposed at one end of the oil pipe and includes an outer sleeve, a central pipe, and a circulation control assembly;

[0008] The outer sleeve is fitted onto the central tube and threadedly connected to the central tube, and a flow channel is formed between the outer sleeve and the central tube;

[0009] The outer sleeve is provided with a first circulation hole penetrating its side wall, and the first circulation hole is connected to the flow channel;

[0010] The central tube is provided with a second circulation hole that penetrates its side wall, and the second circulation hole is also connected to the flow channel;

[0011] The circulation control component is disposed in the flow channel and is used to control the opening and closing of the flow channel between the second circulation hole and the first circulation hole;

[0012] The pump core is used to sit on the inner wall of the central tube and has a drain hole, which can communicate with the second circulation hole when it is in the sitting position.

[0013] The pressure gauge is connected to the pump core.

[0014] Furthermore, the circulation control component includes an upper shift fork, a float valve, and a lower shift fork, and the upper shift fork, the float valve, and the lower shift fork are distributed sequentially from the threaded connection between the outer sleeve and the central tube to the direction away from the threaded connection.

[0015] The upper fork is disposed on the inner wall of the outer sleeve, and both the upper fork and the float valve have a plurality of first short serrations extending in their respective circumferential directions on their opposite end faces.

[0016] The float valve can slide along the axial direction of the flow channel to block or open the flow channel between the second circulation hole and the first circulation hole. The float valve has two symmetrically distributed long serrations on the end face opposite to the lower fork.

[0017] The lower fork is disposed on the inner wall of the outer sleeve, and the end face opposite to the float valve is provided with two second short serrations and a plurality of third short serrations extending circumferentially and used to mesh with the long serrations. The two second short serrations are symmetrically distributed about the axis of the lower fork, and the plurality of third short serrations are flush with each other and higher than the second short serrations.

[0018] Furthermore, a first sealing ring and a second sealing ring are respectively embedded inside and outside the float valve;

[0019] The first sealing ring abuts between the float valve and the central tube;

[0020] The second sealing ring abuts between the float valve and the outer sleeve.

[0021] Furthermore, the pump core includes a nozzle, a diffuser, an outer cylinder, and a flow section;

[0022] The diffuser tube is provided with a main flow channel and a secondary flow channel spaced apart, and both the main flow channel and the secondary flow channel are connected to the nozzle.

[0023] The outer cylinder is sleeved on the diffuser tube, and a flow-through annular cavity communicating with the secondary flow channel is formed between the outer cylinder and the diffuser tube.

[0024] The flow section is threadedly connected to the outer cylinder and also threadedly connected to the diffuser tube. The flow section is provided with a main channel, one end of which is connected to the main channel and the other end is closed.

[0025] Along the axial direction of the flow section, the sidewall of the flow section is provided with side channels that are spaced apart from the main channel, and the side channels are in communication with the flow annular cavity;

[0026] The flow section is provided with a drain hole that penetrates its sidewall and is connected to the main channel.

[0027] Furthermore, the flow segment is also provided with a blind cavity, which is spaced apart from the main channel in the axial direction of the flow segment;

[0028] The side channel extends from the flow-through annular cavity to communicate with the blind cavity;

[0029] The pump core also includes a lower connector and a shut-off valve;

[0030] The lower connector is threadedly connected to the flow section and communicates with the blind cavity;

[0031] The shut-off valve is located in the blind cavity and within the space formed by the lower connector and the flow section. It is used to block or open the lower connector to block or establish communication between the lower connector and the side channel.

[0032] Furthermore, a third sealing ring and a fourth sealing ring are respectively embedded on the outside of the flow section and the outside of the lower connector;

[0033] Along the axial direction of the flow section, the third sealing ring and the fourth sealing ring are distributed on both sides of the drain hole and can abut against the inner wall of the central tube under the hanging condition.

[0034] Furthermore, the inner wall of the central tube is provided with a step, and the flow section abuts against the step surface.

[0035] Furthermore, the pump core also includes a piston cup shaft, a piston cup, a piston cup seat, a fishing head, and a filter screen;

[0036] The cup sleeve is fitted onto the nozzle and threadedly connected to the nozzle, and is also threadedly connected to the end of the outer cylinder away from the flow section;

[0037] The leather cup is fitted onto the leather cup shaft;

[0038] The leather cup seat is connected between the leather cup shaft and the fishing head, and abuts against the leather cup, and a one-way valve is provided inside the leather cup seat;

[0039] The fishing head is provided with a flow hole penetrating its side wall, and the filter screen is set on the side wall of the fishing head and blocks the flow hole.

[0040] Furthermore, the integrated fracturing and fluid drainage testing tubing string also includes a sand catcher, a spacer tubing, a fracturing packer, and a full-bore pressure gauge support, which are distributed sequentially along the axial direction of the tubing.

[0041] The sand lifter is connected to the pump base, the spacer tubing is connected between the sand lifter and the fracturing packer, and the full-bore pressure gauge support is connected to the fracturing packer.

[0042] Secondly, the present invention also provides a method for constructing an integrated fracturing and drainage testing tubing string. This method, based on the aforementioned integrated fracturing and drainage testing tubing string, includes the following steps:

[0043] S100: Pre-fracturing test:

[0044] S110: Run the integrated fracturing and fluid drainage test string to the predetermined position downhole, then set the fracturing packer, and install the tubing hanger, tubing tee or wellhead at the wellhead, while connecting the surface injection system.

[0045] S120: The circulation channel on the pump base is opened by hydraulic means, and then the pump core connected to the pressure gauge is put into the oil pipe and pumped to the pump base, and then the pump core is pumped with pressure.

[0046] S130: After multiple drainage operations, reverse circulation is performed to remove the pump core and pressure gauge;

[0047] S200: After removing the pump core, the circulation channel on the pump base is closed by a large-volume positive circulation method, and then the fracturing operation is carried out;

[0048] S300: After the fracturing operation is completed, the circulation channel on the pump base is opened by hydraulic means, and the pump core is put back in. After several drainage operations, the pump core and pressure gauge are taken out again.

[0049] In summary, the integrated fracturing fluid drainage and testing tubing provided by this invention achieves the following technical effects:

[0050] In this integrated fracturing and drainage test string, the circulation control component controls the connection or disconnection of the first and second circulation holes by controlling the opening and closing of the flow channel between the second and first circulation holes, thus opening or closing the circulation channel of the pump seat. When the pump core is mounted on the central tube, if the first and second circulation holes are connected, the liquid in the pump core will enter the circulation channel through the drain hole and then be discharged from the pump seat. If the first and second circulation holes are disconnected, the liquid in the pump core will be blocked when it flows to the second circulation hole and cannot be discharged from the pump seat.

[0051] In practical applications, the circulation channel of the pump seat is set to the open state. The designed integrated fracturing and fluid drainage test string is then lowered to the predetermined position downhole. After placement, the pump core is pumped into the pump seat and attached. Pressurization continues, drawing formation fluid into the pump core, which then flows along with the power fluid to the drainage hole and enters the annulus through the circulation channel before returning to the surface – this is the initial flow. After a period of drainage, the pump is stopped, and formation fluid is no longer drawn in – this is the initial shut-in. After a period of initial shut-in, the annulus is opened, and pumping is resumed for drainage – this is the secondary flow. After the secondary flow, the pump is stopped again for a secondary shut-in. This process is repeated multiple times, achieving multiple downhole well opening and closing operations. Throughout this entire process, the pressure gauge records the pressure and temperature changes at every moment during the operation – this is the pre-fracturing test. After the test, the pump core and pressure gauge are retrieved via reverse circulation, and the pressure gauge data is reviewed to interpret the pre-fracturing test results.

[0052] As described above, after the pre-fracturing test is completed, the circulation channel is closed via the circulation control component, and then fracturing operations are performed on the formation. After the fracturing operation is completed, the circulation channel is reopened via the circulation control component, and the pump core is re-engaged for multiple downhole well opening and closing operations. Then, the pump core and pressure gauge are retrieved via reverse circulation, and the pressure gauge data is retrieved to interpret the post-fracturing test results.

[0053] As can be seen, compared with the existing technology, the circulation channel on the pump seat of this integrated fracturing and drainage testing tubing can be repeatedly opened and closed. When opened, jet pump drainage testing can be carried out, and when closed, fracturing operations can be carried out. Formation testing before and after fracturing can be achieved without moving the tubing. By comparing the test data before and after fracturing, an objective evaluation of the fracturing effect can be made. Attached Figure Description

[0054] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0055] Figure 1 A cross-sectional view of the integrated fracturing fluid drainage testing tubing provided in an embodiment of the present invention;

[0056] Figure 2 A cross-sectional view of the pump base provided in an embodiment of the present invention;

[0057] Figure 3 A cross-sectional view of the loop control component provided in an embodiment of the present invention;

[0058] Figure 4 A cross-sectional view of the pump core provided in an embodiment of the present invention.

[0059] Icons: 1-oil pipe; 2-flange; 3-outer sleeve; 4-center pipe; 5-flow channel; 6-first circulation hole; 7-second circulation hole; 8-drain hole; 9-upper fork; 10-float valve; 11-lower fork; 12-first short serration; 13-long serration; 14-second short serration; 15-third short serration; 16-first sealing ring; 17-second sealing ring; 18-nozzle; 19-diffuser; 20-outer cylinder; 21-flow section; 22-main flow channel; 23-secondary flow channel; 24-flow annular cavity; 25-main channel; 26 27-Side passage; 28-Blind cavity; 29-Lower connector; 30-Shut-in valve; 31-Third sealing ring; 32-Fourth sealing ring; 33-Leather cup shaft; 34-Leather cup; 35-Leather cup seat; 36-Catching head; 37-Filter screen; 38-Sand catcher; 39-Separating tubing; 40-Fracturing packer; 41-Full-bore pressure gauge support; 42-Connector; 43-Plug; 44-Tubing tee; 45-Catcher; 46-Tubing hanger; 47-Casing; 48-Casing tee; 49-Fifth sealing ring; 50-Check valve. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0061] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0062] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0063] Currently, commonly used integrated fracturing and fluid drainage strings include: tubing + fracturing packer, tubing + jet pump holder + fracturing packer, and tubing + jet pump holder + full-bore selective test valve + eccentric voltage support + fracturing packer. After fracturing, fluid is drained through coiled tubing or by deploying a jet pump. However, existing integrated fracturing and fluid drainage strings cannot perform formation testing before and after fracturing, thus making it impossible to provide an objective and timely evaluation of the fracturing effect.

[0064] In view of this, the present invention provides an integrated fracturing fluid drainage test string, including tubing 1, pump base, pump core, and pressure gauge; the pump base is disposed at one end of tubing 1 and includes an outer sleeve 3, a central tube 4, and a circulation control assembly; the outer sleeve 3 is sleeved on the central tube 4 and threadedly connected to the central tube 4, and a flow channel 5 is formed between the outer sleeve 3 and the central tube 4; the outer sleeve 3 is provided with a first circulation hole 6 penetrating its side wall, and the first circulation hole 6 communicates with the flow channel 5; the central tube 4 is provided with a second circulation hole 7 penetrating its side wall, and the second circulation hole 7 also communicates with the flow channel 5; the circulation control assembly is disposed in the flow channel 5 and is used to control the opening and closing of the flow channel 5 between the second circulation hole 7 and the first circulation hole 6; the pump core is used to sit on the inner wall of the central tube 4 and has a drain hole 8, which can communicate with the second circulation hole 7 under the sitting condition; the pressure gauge is connected to the pump core.

[0065] In this integrated fracturing and drainage test string, the circulation control component controls the connection or disconnection of the first circulation hole 6 and the second circulation hole 7 by controlling the opening and closing of the flow channel 5 between the second circulation hole 7 and the first circulation hole 6, thus opening or closing the circulation channel of the pump seat. When the pump core is mounted on the central tube 4, if the first circulation hole 6 and the second circulation hole 7 are connected, the liquid in the pump core will enter the circulation channel through the drain hole 8 and then be discharged from the pump seat. If the first circulation hole 6 and the second circulation hole 7 are disconnected, the liquid in the pump core will be blocked when it flows to the second circulation hole 7 and cannot be discharged from the pump seat.

[0066] In practical application, the circulation channel of the pump seat is set to the open state. The designed integrated fracturing and fluid drainage test string is then lowered to the predetermined position downhole. After placement, the pump core is pumped into the pump seat and mounted there. Pressurization continues, drawing formation fluid into the pump core, which then flows along with the power fluid to the drain hole 8 and enters the annulus through the circulation channel before returning to the surface – this is the initial flow. After a period of assisted drainage, the pump is stopped, and formation fluid is no longer drawn in – this is the initial shut-in. After a period of initial shut-in, the annulus is opened, and pumping is resumed for drainage – this is the secondary flow. After the secondary flow, the pump is stopped again for a secondary shut-in. This process is repeated multiple times to achieve multiple downhole well opening and closing operations. Throughout this entire process, the pressure gauge records the pressure and temperature changes at every moment during the operation – this is the pre-fracturing test. After the test, the pump core and pressure gauge are retrieved via reverse circulation, and the pressure gauge data is reviewed to interpret the pre-fracturing test results.

[0067] As described above, after the pre-fracturing test is completed, the circulation channel is closed via the circulation control component, and then fracturing operations are performed on the formation. After the fracturing operation is completed, the circulation channel is reopened via the circulation control component, and the pump core is re-engaged for multiple downhole well opening and closing operations. Then, the pump core and pressure gauge are retrieved via reverse circulation, and the pressure gauge data is retrieved to interpret the post-fracturing test results.

[0068] As can be seen, compared with the existing technology, the circulation channel on the pump seat of this integrated fracturing and drainage testing tubing can be repeatedly opened and closed. When opened, jet pump drainage testing can be carried out, and when closed, fracturing operations can be carried out. Formation testing before and after fracturing can be achieved without moving the tubing. By comparing the test data before and after fracturing, an objective evaluation of the fracturing effect can be made.

[0069] The following combination Figures 1 to 4 The structure and shape of the integrated fracturing fluid drainage testing tubing provided in this embodiment are described in detail below:

[0070] refer to Figure 1 The integrated fracturing and fluid drainage testing tubing string also includes a sand lifter 38, a spacer tubing 39, a fracturing packer 40, and a full-bore pressure gauge support 41, which are distributed sequentially along the axial direction of the tubing 1; the lower end of the outer sleeve 3 is threaded with a connector 42, which is connected to the sand lifter 38; the spacer tubing 39 is connected between the sand lifter 38 and the fracturing packer 40, and the full-bore pressure gauge support 41 is connected to the fracturing packer 40.

[0071] Continue to refer to Figure 1 The upper end of tubing 1 is connected to a tubing tee 44, the upper opening of which is connected to a plug 43. A catcher 45, connected to the plug 43, is installed inside the tubing tee 44. The upper end of casing 47 is connected to casing tee 48 via flange 2. Tubing 1 is suspended on casing tee 48 via tubing hanger 46. In application, the designed integrated fracturing and fluid drainage test string is lowered to the predetermined position downhole. Then, the fracturing packer 40 is set to isolate the annulus from the target formation. The string is then suspended at the wellhead via tubing hanger 46. Tubing tee 44 or a Christmas tree is connected above tubing hanger 46. A pump core connected to a pressure gauge is then inserted into the tubing through the upper opening of tubing tee 44. The upper end of tubing tee 44 is then blocked with catcher 45 connected to plug 43. Finally, the surface injection system is connected, allowing the power fluid to be pumped into the tubing from the side of tubing tee 44, pumping the pump core into the pump seat. Additionally, it should be noted that the sand support 38 can prevent sand from depositing on top of the packer and burying it, and the full-bore pressure gauge support 41 can be equipped with 2 to 4 electronic pressure gauges to monitor the entire construction process.

[0072] Regarding the pump base, specifically:

[0073] refer to Figure 3The circulation control assembly includes an upper fork 9, a float valve 10, and a lower fork 11. These three components are arranged sequentially from the threaded connection between the outer sleeve 3 and the central tube 4 to the direction away from the threaded connection. Both the upper fork 9 and the lower fork 11 are splined to the outer sleeve 3 and cannot rotate. The opposing end faces of the upper fork 9 and the float valve 10 are each provided with multiple short first serrations 12 extending circumferentially. The float valve 10 can slide axially along the flow channel 5 to block... Alternatively, a flow passage 5 can be established between the second circulation hole 7 and the first circulation hole 6. Two symmetrically distributed long serrations 13 are provided on the end face of the float valve 10 opposite to the lower fork 11. Two second short serrations 14 and multiple third short serrations 15 extending circumferentially and engaging with the long serrations 13 are provided on the end face of the lower fork 11 opposite to the float valve 10. The two second short serrations 14 are symmetrically distributed about the axis of the lower fork 11, and the multiple third short serrations 15 are flush with each other and higher than the second short serrations 14. A first sealing ring 16 and a second sealing ring 17 are respectively embedded inside and outside the float valve 10. The first sealing ring 16 abuts between the float valve 10 and the central tube 4; the second sealing ring 17 abuts between the float valve 10 and the outer sleeve 3.

[0074] Specifically, such as Figure 3 As shown, the upper end face of the float valve 10 has 12 first short serrations 12, and the lower end face of the float valve 10 has two symmetrical long serrations 13; the lower end face of the upper shift fork 9 has 12 first short serrations 12; the upper end face of the lower shift fork 11 also has 12 serrations, but two of the symmetrical serrations (i.e., the second short serrations 14) are deeper than the other serrations (i.e., the third short serrations 15). It should be noted that the number of serrations is not limited to those described above.

[0075] Combination Figure 2 and Figure 3 As shown, when the external pressure of the outer sleeve 3 is greater than the internal pressure, the float valve 10 will move downwards. After contacting the relevant serrations on the lower fork 11, because the two long serrations 13 at the lower end of the float valve 10 differ from the serrations on the lower fork 11 by half a serration angle, the float valve 10 must rotate by half a serration angle to continue moving downwards. After rotation, the serrations at the upper end of the float valve 10 again differ from the serrations at the lower end of the upper fork 9 by half a serration angle. When the internal pressure of the outer sleeve 3 is greater than the external pressure, the float valve 10 will move upwards. After contacting the serrations under the upper fork 9, the float valve 10 will rotate by half a serration angle again. In this way, the float valve 10 will move up and down under the action of the positive and negative pressure difference inside and outside the sleeve, and will also rotate. When the float valve 10 rotates to the position shown... Figure 4When the position shown is reached, the float valve 10 will descend a greater distance, causing the first sealing ring 16 on the float valve 10 to move down below the second circulation hole 7. At this time, the second circulation hole 7 will be connected to the first circulation hole 6, and the circulation channel on the pump base will be opened. When you want to close it after it is opened, you can open the oil jacket annulus for large-displacement positive circulation. The second circulation hole 7 on the central pipe 4 will generate flow obstruction, thereby forming a pressure difference between the inside and outside of the pipe to push the float valve 10 up, which will close the circulation channel on the pump base.

[0076] In the above design, the circulation channel of the pump seat can be set to either open or closed when it is inserted into the well. When it is set to open, after the downhole tubing is set up, the pump core can be inserted to perform the fluid discharge test. When it is set to closed, the annulus (outside tubing 1) can be pressurized to about 5 MPa and maintained. Then, about 10 MPa is pressurized from inside tubing 1 and released. Then, 10 MPa is pressurized again and released. When the pressure of the annulus is released for the third time after pressurizing to 10 MPa, the pressure of the annulus will also be released at the same time, indicating that the circulation channel on the pump seat has been opened.

[0077] Regarding the pump core, specifically:

[0078] refer to Figure 4 The pump core includes a nozzle 18, a diffuser 19, an outer cylinder 20, and a flow section 21. The diffuser 19 has a main flow channel 22 and a secondary flow channel 23 spaced apart, both of which are connected to the nozzle 18. The outer cylinder 20 is fitted onto the diffuser 19, forming a flow annular cavity 24 with the diffuser 19 that is connected to the secondary flow channel 23. The flow section 21 is threaded to the outer cylinder 20 and also threaded to the diffuser 19. The flow section 21 has a main channel 25, one end of which is connected to the main flow channel 22, and the other end is closed. Along the axial direction of the flow section 21, the side wall of the flow section 21 has side channels 26 spaced apart from the main channel 25, which are connected to the flow annular cavity 24. The flow section 21 has a drain hole 8 penetrating its side wall, which is connected to the main channel 25.

[0079] The flow section 21 is also provided with a blind cavity 27. In the axial direction of the flow section 21, the blind cavity 27 is spaced apart from the main channel 25. The side channel 26 extends from the flow ring cavity 24 to communicate with the blind cavity 27. The pump core also includes a lower connector 28 and a shut-off valve 29. The lower connector 28 is threadedly connected to the flow section 21 and communicates with the blind cavity 27. The shut-off valve 29 is provided in the blind cavity 27 and is located in the space formed by the lower connector 28 and the flow section 21. It is used to block or open the lower connector 28 to block or establish the communication between the lower connector 28 and the side channel 26. Here, when the shut-off valve 29 abuts against the lower connector 28, the fifth sealing ring 49 embedded in the shut-off valve 29 abuts against the inner wall of the lower connector 28.

[0080] Above the second circulation hole 7, the inner wall of the central tube 4 is machined with a first smooth sealing surface and a step 32, and below the second circulation hole 7, a second smooth sealing surface is machined. After the pump core is inserted, it will sit on the step 32, and at the same time, the two sealing surfaces will form a sealing fit with the third sealing ring 30 and the fourth sealing ring 31 on the pump core, respectively. The positive circulation input of the power fluid can perform jet pump discharge.

[0081] The pump core also includes a cup shaft 33, a cup 34, a cup seat 35, a fishing head 36, and a filter screen 37; the cup shaft 33 is sleeved on the nozzle 18 and threadedly connected to the nozzle 18, and is also threadedly connected to the end of the outer cylinder 20 away from the flow section 21; the cup 34 is sleeved on the cup shaft 33; the cup seat 35 is connected between the cup shaft 33 and the fishing head 36 and abuts against the cup 34, and a one-way valve 50 is provided inside the cup seat 35; the fishing head 36 is provided with a flow hole penetrating its side wall, and the filter screen 37 is provided on the side wall of the fishing head 36 and blocks the flow hole.

[0082] refer to Figures 1 to 4 When the pump core is pumped downhole, after it is seated, the two sets of third sealing rings 30 and fourth sealing rings 31 on the pump core will exactly cross a set of circulation holes on the pump seat. At this time, the high-pressure power fluid will flow downward after being filtered by the filter screen 37, and after opening the one-way valve, it will enter the nozzle 18, thereby generating a high-speed jet. A negative pressure suction zone will be formed around the high-speed jet, thereby drawing the formation fluid from the side hole on the lower connector 28. After the formation fluid enters the lower connector 28, it will open the well valve 29 and enter the side channel 26, the flow annular cavity 24, and the secondary flow channel 23 in sequence through the blind cavity 27 into the periphery of the diffuser 19. Then, it will mix with the high-speed jet and enter the main channel 22 for expansion and pressure reduction. Finally, it will enter the circulation channel from the main channel 25 and the drain hole 8, and enter the oil casing annulus from the circulation channel, and then be discharged to the surface through the casing tee 48. When well shut-in is required, simply stop the pump and apply a balancing pressure to both inside and outside the pipe to keep the shut-in valve 29 in a reverse pressurized state. The operation is simple and reliable.

[0083] When the pump is started in reverse circulation, the check valve 50 is closed, blocking the pressure relief channel to the pipe. This allows the pump core to be easily removed from the pump seat. When backwashing to the wellhead, the catcher 45 catches the pump core. The plug 43 is removed to take out the pump core and pressure gauge. The pressure gauge data can be reviewed to understand the test results as soon as possible.

[0084] In this invention, the pump base is designed as a hydraulically operated multi-switch type pump base, and the pump core adopts a forward circulation discharge and reverse circulation pump start-up working mode. A shut-in valve 29 is installed at the formation fluid inlet of the pump core. This shut-in valve 29 opens during discharge and closes after reverse pressurization, and can reliably seal to realize downhole well opening and closing. A pressure gauge can be connected below the pump core to obtain formation pressure data during discharge flow and well shut-in recovery.

[0085] The repeated switching of the hydraulic multi-switch pump base is achieved by creating a positive and negative pressure difference inside and outside the cylinder, causing the float valve 10 to move up and down. Simultaneously, under the action of the upper fork 9 and the lower fork 11, it rotates by an angle. The lower fork 11 has open and closed positions. When the float valve 10 rotates to the open position, it can move downwards a significant distance, connecting the first circulation hole 6 with the second circulation hole 7. At this point, the circulation channel is open, allowing the pump core to be inserted for drainage testing. After the test, the pump core is removed via reverse circulation. When it is necessary to close the circulation channel on the pump base, a large-volume positive circulation from inside the pipe moves the float valve 10 upwards, closing the circulation channel. After the pump base is closed, fracturing operations can be performed. After fracturing operations are completed, the positive and negative pressure difference inside and outside the cylinder reopens the circulation channel on the pump base, allowing the pump core to be inserted again for post-fracturing drainage testing. This allows for a comparison of tests before and after fracturing, providing an objective evaluation of the fracturing effect.

[0086] This invention also provides a method for constructing an integrated fracturing and drainage testing tubing string. This method, based on the aforementioned integrated fracturing and drainage testing tubing string, includes the following steps:

[0087] S100: Pre-fracturing test:

[0088] S110: Lower the integrated fracturing and fluid discharge testing string to the predetermined position downhole, then set the fracturing packer 40, and install the tubing hanger 46, tubing tee 44, or Christmas tree at the wellhead, while connecting the surface injection system; S120: Open the circulation channel on the pump seat hydraulically, then insert the pump core connected to the pressure gauge into the tubing 1 and pump it to the pump seat, then pump pressure into the pump core; S130: After multiple fluid discharges, reverse the circulation to retrieve the pump core and pressure gauge; S200: After retrieving the pump core, close the circulation channel on the pump seat using a high-volume positive circulation method, and then perform fracturing operations; S300: After the fracturing operations are completed, open the circulation channel on the pump seat hydraulically again, and insert the pump core again. After multiple fluid discharges, retrieve the pump core and pressure gauge again.

[0089] Specifically, the integrated fracturing and fluid discharge testing string is designed from top to bottom as follows: tubing 1 + hydraulically operated multi-switch pump seat + sand catcher 38 + spacer tubing 39 + fracturing packer 40 + full-bore pressure gauge holder 41. During operation, the designed working string is lowered to the predetermined position downhole, then the fracturing packer 40 is seated, and tubing hangers 46, tubing tees 44, or Christmas trees are installed at the wellhead. The surface injection system is then connected, and the circulation channel on the pump seat is opened hydraulically. After the circulation channel is opened, the pump core connected to the pressure gauge is inserted into the working tubing 1 and pumped to the pump seat, forming a sealed fit with the pump seat. The pressure continues to increase, and a high-speed jet is generated by nozzle 18. Through cooperation with diffuser 19, the formation fluid is drawn into the annulus and returned to the surface along with the power fluid. This is the initial flow. After a period of assisted drainage, the pump is stopped. At this point, the formation pressure has decreased, and the shut-in valve 29 in the pump core will be in a reverse pressurization state, thus achieving downhole shut-in; this is the initial shut-in. To prevent the shut-in valve 29 from being opened due to the formation pressure exceeding the hydrostatic pressure on the valve during the later recovery phase, a balancing pressure should be applied to both inside and outside the pipe as soon as possible after the pump is stopped and maintained to ensure that the shut-in valve 29 remains in a reverse pressurization state. After a period of initial shut-in, the annulus should be opened first, and then the surface pump should be started to drain the fluid, which is the secondary flow. After the secondary flow is completed, the pump is stopped again, the balancing pressure is applied, and the well is shut in a second time. This allows for multiple downhole well opening and closing operations. The downhole pressure gauge will record the pressure and temperature changes at every moment during the operation; this is the pre-fracturing test. After the test, the pump core and pressure gauge are retrieved via reverse circulation, and the pressure gauge data can be reviewed to interpret the pre-fracturing test results.

[0090] Following the above, after the pre-fracturing tests are completed, the circulation channel on the pump base is closed using a high-volume positive circulation method. Once the pump base is closed, fracturing operations can be performed on the formation. After the fracturing operation is completed, the circulation channel on the pump base is reopened hydraulically, and the pump core is then inserted for post-fracturing fluid discharge testing. After the test, the pump core and pressure gauge are retrieved via reverse circulation, and the pressure gauge data is reviewed to interpret the post-fracturing test results. By comparing and analyzing the results of the two tests before and after fracturing, an objective evaluation of the fracturing operation effect can be made.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An integrated tubing string for fracturing fluid drainage testing, characterized in that, include: Oil pipe (1), pump base, pump core and pressure gauge; The pump base is located at one end of the oil pipe (1) and includes an outer sleeve (3), a central pipe (4) and a circulation control assembly; The outer sleeve (3) is fitted onto the central tube (4) and threadedly connected to the central tube (4), and a flow channel (5) is formed between the outer sleeve (3) and the central tube (4). The outer sleeve (3) is provided with a first circulation hole (6) penetrating its side wall, and the first circulation hole (6) is connected to the flow channel (5); The central tube (4) is provided with a second circulation hole (7) that penetrates its side wall, and the second circulation hole (7) is also connected to the flow channel (5); The circulation control component is disposed in the flow channel (5) and is used to control the opening and closing of the flow channel (5) between the second circulation hole (7) and the first circulation hole (6); The pump core is used to sit on the inner wall of the central tube (4) and has a drain hole (8). The drain hole (8) can communicate with the second circulation hole (7) under the sitting condition. The pressure gauge is connected to the pump core; The cycle control assembly includes an upper fork (9), a float valve (10), and a lower fork (11), and the upper fork (9), the float valve (10), and the lower fork (11) are distributed sequentially from the threaded connection between the outer sleeve (3) and the central tube (4) to the direction away from the threaded connection. The upper fork (9) is disposed on the inner wall of the outer sleeve (3), and both the upper fork (9) and the float valve (10) are provided with a plurality of first short serrations (12) extending in their respective circumferences on their opposite end faces. The float valve (10) can slide along the axial direction of the flow channel (5) to block or open the flow channel (5) between the second circulation hole (7) and the first circulation hole (6). The float valve (10) has two symmetrically distributed long serrations (13) on the end face opposite to the lower fork (11). The lower fork (11) is disposed on the inner wall of the outer sleeve (3), and on the end face opposite to the float valve (10) are provided two second short serrations (14) and a plurality of third short serrations (15) extending circumferentially and used to engage with the long serrations (13). The two second short serrations (14) are symmetrically distributed about the axis of the lower fork (11), and the plurality of third short serrations (15) are flush with each other and higher than the second short serrations (14).

2. The integrated fracturing and drainage testing tubing string according to claim 1, characterized in that, The float valve (10) is fitted with a first sealing ring (16) and a second sealing ring (17) inside and outside, respectively. The first sealing ring (16) abuts between the float valve (10) and the central tube (4); The second sealing ring (17) abuts between the float valve (10) and the outer sleeve (3).

3. The integrated fracturing fluid drainage and testing tubing string according to claim 1, characterized in that, The pump core includes a nozzle (18), a diffuser (19), an outer cylinder (20), and a flow section (21). The diffuser tube (19) is provided with a main flow channel (22) and a secondary flow channel (23) spaced apart, and both the main flow channel (22) and the secondary flow channel (23) are connected to the nozzle (18). The outer cylinder (20) is sleeved on the diffuser tube (19) and forms a flow-through annular cavity (24) with the diffuser tube (19) that communicates with the secondary flow channel (23). The flow section (21) is threadedly connected to the outer cylinder (20) and also threadedly connected to the diffuser (19). The flow section (21) is provided with a main channel (25). One end of the main channel (25) is connected to the main channel (22), and the other end is closed. Along the axial direction of the flow section (21), the side wall of the flow section (21) is provided with side channels (26) that are spaced apart from the main channel (25), and the side channels (26) are connected to the flow annular cavity (24); The flow section (21) is provided with a drain hole (8) that penetrates its side wall, and the drain hole (8) is connected to the main channel (25).

4. The integrated fracturing and drainage testing tubing string according to claim 3, characterized in that, The flow section (21) is also provided with a blind cavity (27), which is spaced apart from the main channel (25) in the axial direction of the flow section (21); The side channel (26) extends from the flow-through annular cavity (24) to communicate with the blind cavity (27); The pump core also includes a lower connector (28) and a shut-off valve (29). The lower connector (28) is threadedly connected to the flow section (21) and communicates with the blind cavity (27); The shut-off valve (29) is located in the blind cavity (27) and within the space formed by the lower connector (28) and the flow section (21). It is used to block or open the lower connector (28) to block or establish the connection between the lower connector (28) and the side channel (26).

5. The integrated fracturing and drainage testing tubing string according to claim 4, characterized in that, A third sealing ring (30) and a fourth sealing ring (31) are respectively embedded on the outside of the flow section (21) and the outside of the lower connector (28). In the axial direction of the flow section (21), the third sealing ring (30) and the fourth sealing ring (31) are distributed on both sides of the drain hole (8) and can abut against the inner wall of the central tube (4) under the hanging condition.

6. The integrated fracturing fluid drainage testing string according to claim 3, characterized in that, The inner wall of the central tube (4) is provided with a step (32), and the flow section (21) abuts against the step surface.

7. The integrated fracturing and drainage testing tubing string according to claim 3, characterized in that, The pump core also includes a cup shaft (33), a cup (34), a cup seat (35), a fishing head (36), and a filter screen (37). The cup shaft (33) is sleeved on the nozzle (18) and threadedly connected to the nozzle (18), and is also threadedly connected to the end of the outer cylinder (20) away from the flow section (21); The leather cup (34) is sleeved on the leather cup shaft (33); The leather cup seat (35) is connected between the leather cup shaft (33) and the fishing head (36), and abuts against the leather cup (34), and a one-way valve is provided inside the leather cup seat (35); The fishing head (36) is provided with a flow hole penetrating its side wall, and the filter screen (37) is provided on the side wall of the fishing head (36) and blocks the flow hole.

8. The integrated fracturing and drainage testing string according to any one of claims 1 to 7, characterized in that, The integrated fracturing and drainage test tubing also includes a sand catcher (38), a spacer tubing (39), a fracturing packer (40), and a full-bore pressure gauge holder (41) arranged sequentially along the axial direction of the tubing (1). The sand lifter (38) is connected to the pump base, the spacer tubing (39) is connected between the sand lifter (38) and the fracturing packer (40), and the full-bore pressure gauge support (41) is connected to the fracturing packer (40).

9. A method for constructing an integrated fracturing and drainage testing tubing string, characterized in that, Based on the integrated fracturing fluid drainage test string as described in any one of claims 1 to 8, the process includes the following steps: S100: Pre-fracturing test: S110: Run the integrated fracturing and fluid drainage test string down to the predetermined position in the well, then set the fracturing packer (40), and install the tubing (1) hanger, tubing (1) tee or production tree at the wellhead, and connect the surface injection system at the same time; S120: Open the circulation channel on the pump seat by hydraulic means, then put the pump core connected to the pressure gauge (2) into the oil pipe (1) and pump it to the pump seat, and then pump pressure into the pump core. S130: After multiple drainage operations, reverse circulation is performed to remove the pump core and pressure gauge (2). S200: After removing the pump core, the circulation channel on the pump base is closed by a large-volume positive circulation method, and then the fracturing operation is carried out; S300: After the fracturing operation is completed, the circulation channel on the pump base is opened by hydraulic means, and the pump core is put back in. After several drainage operations, the pump core and pressure gauge are taken out again (2).

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