Gas well testing tubular column and testing method

Abstract

The invention belongs to the technical field of oil and gas field testing, and particularly discloses a gas well testing tubular column which comprises a screen pipe, a perforating gun set, a first oil pipe, a second oil pipe, a third oil pipe and a fourth oil pipe, an APR testing tool and a packer are arranged between the third oil pipe and the fourth oil pipe, the two ends of the APR testing tool are connected with the lower end of the third oil pipe and the upper end of the packer respectively, and the lower end of the packer is connected with the upper end of the fourth oil pipe. The lower end of the fourth oil pipe is connected with the upper end of the perforating gun group through the screen pipe; the lower end of the first oil pipe is connected with the upper end of the second oil pipe, and a telescopic connector is connected between the second oil pipe and the third oil pipe. The device can adapt to the severe environment of the ultra-deep high-temperature and high-pressure gas well, the testing accuracy and reliability are improved, the risk in the testing process is reduced, and meanwhile the efficiency and economical efficiency of oil and gas exploration and development are improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field testing technology, specifically to a gas well testing string and testing method. Background Technology

[0002] my country's discovered natural gas reservoirs are mainly unconventional, including low-permeability tight sandstone, carbonate, volcanic, and shale reservoirs. Most of these unconventional reservoirs are highly heterogeneous, with significant differences in well productivity. Effective evaluation of well productivity is crucial for rational well allocation. As exploration and development deepen, target formations extend into deeper and more complex strata, leading to an increasing number of ultra-deep, high-temperature, and high-pressure gas wells. Inappropriate selection of the productivity testing type can result in well test failures, with test data failing to meet interpretation requirements. This can either prevent well interpretation or result in mismatched interpreted productivity. Such situations mean wasted human, material, and financial resources on well productivity testing. Currently, the commonly used perforation-acidizing-testing combined process for oil and gas testing rapidly acquires formation temperature and pressure data, saving testing time and making it one of the primary methods for testing ultra-deep, high-temperature, and high-pressure gas wells.

[0003] In existing technologies, high-pressure gas wells typically employ specialized test strings. This involves running a pressure gauge into the well using tubing, measuring the pressure, and then retrieving the test string to remove the gauge before running the completion string for production. Running the test string in high-pressure gas wells necessitates well control, which results in significant fluid loss and fails to stabilize the well. This process only allows for a short working window, posing a substantial well control risk. Furthermore, separating the test and completion strings significantly increases operational costs and risks. Since the test string must be retrieved after testing, retrievable packers are required. However, under high temperature and pressure, retrievable packers are less reliable than permanent packers, greatly increasing the risk of test failure.

[0004] Existing test strings commonly suffer from problems during actual testing, such as casing blockage during acidizing, perforation gun jamming or falling off, screen pipe breakage, and short service life. This leads to complex and frequent oil and gas testing in ultra-deep wells, severely hindering the smooth progress of exploration and development. Therefore, developing a test string and testing method that can adapt to the ultra-deep, high-temperature, and high-pressure environment is of great significance for improving the efficiency and accuracy of gas well testing and reducing exploration and development costs.

[0005] In response to the above situation, scholars both domestically and internationally have conducted relevant research in this field and achieved some understanding, but all have certain limitations. Liu Hongtao, Li Lili, and others, in their 2016 study (Optimization and Application of High-Temperature and High-Pressure Test Strings in Kuqa Mountain Foreland), researched and explored high-temperature and high-pressure gas well testing processes. Their main approach was to eliminate the combined perforation-acidizing-testing method and instead perform a process of perforating first and then running the test string, in order to reduce the impact of the instantaneous impact load during perforation on the perforating gun and packer. While this method eliminates the impact of the perforation detonation effect, it adds an extra trip for drilling operations, reducing the efficiency of oil testing. Furthermore, running the test string after perforation carries certain well control risks.

[0006] Patent application number 201611183331.9 (A Deepwater High-Temperature and High-Pressure Oil and Gas Well Test String) provides a deepwater high-temperature and high-pressure oil and gas well test string that can reduce or even avoid the destructive additional thermal stress generated by the fluid in the confined space during the testing or production process of deepwater oil and gas wells, and protect the integrity of the casing and deepwater wellbore. However, in practical applications, the heat insulation part designed by this method to withstand high temperature and high pressure may face technical and material challenges, and also increase the complexity and cost of operation.

[0007] Patent application number 200920246761.X (A Completion String for Gas Production Wells) provides a completion string for use in oil and gas field gas production wells. This string lowers a pressure gauge holder carrying a well pressure gauge into the well before the upper and lower gas lift working cylinders and the downhole nozzle. This simultaneously meets the needs of gas lift fluid discharge and downhole throttling, and allows for real-time monitoring of bottomhole flowing pressure, temperature, and bottom pressure recovery. It does not affect normal oil and gas well production while obtaining accurate formation testing data. The string is reliable and has a low cost. However, this string has limitations in high-temperature, high-pressure downhole environments. Post-operation maintenance under these conditions is not only costly but may also affect well production efficiency.

[0008] Patent application number 201910056774.9 (Testing method and testing system for ultra-deep, ultra-high temperature and high pressure gas wells) provides a testing method and testing system for ultra-deep, ultra-high temperature and high pressure gas wells, which can significantly reduce the time of high-risk operations and improve the quality of test data; however, the testing method in this system involves multiple steps and multiple devices, making the operation highly complex and posing significant safety hazards.

[0009] Patent application number 201610511856.4 (Oil and Gas Well Formation Testing Equipment and Method Thereof) discloses an oil and gas well formation testing equipment and method. The oil and gas well formation testing equipment includes a first connecting tubing string, a second connecting tubing string, a self-controlled flow restrictor, testing instruments, a packer, a screen pipe, and a perforator. The self-controlled flow restrictor is used to balance the pressure difference at the bottom of the oil and gas well, which can improve the efficiency of balancing the pressure difference, improve the accuracy of oil and gas well formation testing, and save costs. However, the test pad in the equipment needs to occupy part of the space of the test tubing string, which restricts the flow rate of formation fluid, affects the accuracy of the testing method, and requires additional costs, increasing the cost of testing the formation.

[0010] Based on literature review, to avoid a series of complex problems caused by perforation detonation and other factors, deep well risk exploration wells have previously adopted a process of "first running tubing for perforation, then running tubing for well cleaning and mud treatment, and finally running tubing for acidizing and testing." Based on the application of currently used gas well testing methods, the following limitations of existing gas well testing methods are summarized:

[0011] (1) Well control risks will increase significantly: After the perforation string is run to open the producing layer and the reservoir is exposed, there will be certain well control risks in the subsequent running of the perforation string, running of the well passage string, and running of the test string. If well leakage occurs in the reservoir, the well control risks during running of the drill string will be even greater.

[0012] (2) Complex downhole outbursts induced by kill fluid: Because sufficient observation time is required after perforation, subsequent operations such as gun lifting and test string running can only continue after the well pressure has stabilized. Therefore, the kill fluid remains stationary at the bottom of the well for a long time, and its high-temperature stability deteriorates, making it prone to precipitation and causing complex issues such as obstruction when running the test string.

[0013] (3) Increased difficulty in oil testing process: High-density kill fluid causes a narrow annular pressure window, resulting in no safe pressure window to set the operating pressure of pressure-controlled downhole tools such as RDS valves and OMNI valves, further limiting the functions of test string such as fluid replacement and downhole shut-in.

[0014] (4) Increased difficulty of reservoir stimulation: The high-density kill fluid below the packer cannot be displaced from the wellbore and is difficult to squeeze into the formation during acidizing. If the kill fluid undergoes cementation, denaturation and precipitation, the reservoir stimulation becomes more difficult and may cause wellhead overpressure, requiring multiple oscillating acidizing processes.

[0015] (5) Increased reservoir contamination: After perforation, the wellbore needs to be filled with kill fluid to maintain formation pressure balance. As a result, the reservoir is in contact with high-density kill fluid for a long time, and the near-wellbore area is severely blocked. In addition, the pores are further filled with mud during reservoir stimulation, which causes greater damage to the reservoir and results in the test production of a single well not reaching the expected effect.

[0016] Therefore, it is necessary to propose important testing technologies and methods to address tubing problems caused by perforation detonation and other factors, and to cope with complex and objective oil and gas testing conditions such as diverse geological features and harsh engineering environments. Specifically, it is necessary to propose test tubing that meets the requirements of the combined perforation-acidizing-testing technology for ultra-deep, high-temperature, and high-pressure wells, ensuring the integrity of the lower tubing of the packer in deep and ultra-deep wells, and improving the success rate of oil testing in ultra-deep, high-temperature, and high-pressure exploration wells. Summary of the Invention

[0017] This invention provides a gas well testing string and testing method, aiming to improve the accuracy and reliability of testing, reduce the risks in the testing process, and improve the efficiency and economy of oil and gas exploration and development.

[0018] This invention is achieved through the following technical solution: a gas well test string, comprising a screen pipe, a perforation gun assembly, and a first tubing, a second tubing, a third tubing, and a fourth tubing connected coaxially in sequence;

[0019] An APR testing tool and a packer are provided between the third and fourth oil pipes. The two ends of the APR testing tool are connected to the lower end of the third oil pipe and the upper end of the packer, respectively. The lower end of the packer is connected to the upper end of the fourth oil pipe. The lower end of the fourth oil pipe is connected to the upper end of the perforation gun assembly through the screen pipe. The lower end of the first oil pipe is connected to the upper end of the second oil pipe. An expansion joint is connected between the second and third oil pipes.

[0020] Furthermore, the expansion joint is a full-bore structure, and the lower end of the expansion joint is connected to the third oil pipe or located in the second oil pipe.

[0021] In this design, the expansion joint is a full-bore structure that is inserted into the well in a stretched state. It can be used to compensate for the shortening of the test tubing during acidizing and to ensure that the suspended weight of the lower tubing can be effectively applied to the packer.

[0022] Furthermore, the upper and lower ends of the packer are respectively connected to a safety joint and a kill sleeve, and the upper and lower ends of the packer are respectively connected to the APR testing tool and the fourth tubing through the safety joint and the kill sleeve.

[0023] In this design, the upper and lower ends of the packer are connected to a safety joint and a kill sleeve, respectively. This ensures that the APR testing tool or packer can be successfully retrieved when the tubing gets stuck, thus ensuring successful downhole data acquisition. In addition, the kill sleeve is located at the lower end of the packer. After the test, the ball is dropped to open the circulation channel, which facilitates rapid well killing and effectively solves the risk that the gas in the annulus cannot be pushed back into the wellbore.

[0024] Furthermore, the first, second, and third oil pipes above the packer, as well as the APR testing tool, are all connected using a gas-tight coupling.

[0025] This setup ensures the sealing of the tubing string and meets the testing requirements of high-pressure gas wells.

[0026] Furthermore, the third oil pipe is a thick-walled oil pipe, the second oil pipe is a thin-walled oil pipe, the wall thickness of the first oil pipe is not less than the wall thickness of the second oil pipe, and the first oil pipe, the second oil pipe and the third oil pipe form a dumbbell-shaped structure.

[0027] The third tubing in this design uses thick-walled tubing, which has higher bending resistance and ensures that the weight of the tubing below the expansion joint is effectively applied to the packer, thereby ensuring effective packer setting during acidizing. The second tubing is thin-walled, which reduces the weight of the test string.

[0028] In addition, the first, second, and third tubings form a dumbbell-shaped structure, which can effectively transfer the suspended weight to the mechanical packer during testing and modification. Compared with the existing perforation-acidizing-testing tubing, this can effectively reduce the problem of oil-casing cross-flow caused by packer failure during acidizing.

[0029] Furthermore, the APR testing tool is a pressure-controlled downhole tool or a mechanical downhole tool.

[0030] APR testing tools can be configured according to testing requirements. They can be either pressure-controlled downhole tools or mechanical downhole tools. In actual installation, downhole shut-in tools should also be configured.

[0031] Furthermore, the fourth oil pipe is a thick-walled oil pipe, and the length of the fourth oil pipe is not less than 50m.

[0032] This design can reduce the problems of packer failure or tubing breakage caused by perforation detonation, while the lower end is close to the production layer.

[0033] Furthermore, the strength of the screen tube is not lower than the strength of the fourth oil tube. It is used to establish a gas flow channel.

[0034] A gas well testing method includes the following steps:

[0035] The wellbore is cleaned and tested to ensure it meets the requirements for testing operations.

[0036] The aforementioned gas well test string is lowered into clean water and, after reaching the perforation position, electrical depth calibration is performed to adjust the tubing string depth to meet the perforation requirements; the tubing hanger is connected, and the packer is set.

[0037] After setting the packer, continue to press down the tubing string, compress the expansion joint into place, set the tubing hanger, and tighten the top screw; disassemble the blowout preventer assembly, install the gas wellhead, connect the pipeline between the wellhead and the surface process, and test the pressure according to the regulations.

[0038] Annular pressure testing was performed on the packer to confirm that the packer was properly set.

[0039] The perforation gun assembly was detonated by pressurizing inside the oil pipe, and the perforation status was monitored.

[0040] Well opening is conducted for fluid drainage, testing, and acidizing to obtain information on formation fluid properties and production capacity.

[0041] After the test, the ball was dropped into the tubing to open the well-killing sleeve for squeezing and killing the well. The packer lower trap gas pressure was returned to the formation. The annulus was pressurized and the circulation valve in the APR test tool was opened to achieve downhole shut-in. At the same time, the oil-casing circulation channel was established for circulation well killing.

[0042] After dismantling the gas wellhead, installing the blowout preventer assembly, and unsealing the packer, the test string was pulled out.

[0043] Furthermore, the perforating gun assembly optimizes the perforation parameters based on the simulation results of the perforation detonation load verification, and the perforating gun assembly adopts segmented delayed perforation. This scheme can reduce the perforation detonation load.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] 1. The improved test string in this scheme can effectively avoid oil-casing cross-contamination caused by packer failure during acidizing, and reduce problems such as perforation gun and screen breakage caused by perforation detonation effect, which can greatly improve the success rate of well testing.

[0046] It can also adapt to the harsh environment of ultra-deep, high-temperature, and high-pressure gas wells, improve the accuracy and reliability of testing, reduce the risks in the testing process, and at the same time improve the efficiency and economy of oil and gas exploration and development.

[0047] 2. The third tubing uses thick-walled tubing, and its higher bending resistance ensures that the weight of the tubing below the expansion joint is effectively applied to the mechanical packer, thereby ensuring the effective setting of the mechanical packer during acidizing. The increased strength of the fourth tubing and screen pipe can resist the effects of higher perforation detonation, thereby reducing problems such as perforation gun and screen pipe breakage. Safety joints are connected to both the top and bottom of the packer, and the testing time is strictly controlled to ensure the smooth removal of the APR testing tools and the accurate acquisition of test data, thereby significantly and effectively reducing the complexity of oil testing accidents in ultra-deep, high-temperature and high-pressure gas wells.

[0048] 3. The test string provided in this invention patent embodiment, due to its dumbbell-shaped structure, effectively transfers the suspended weight to the mechanical packer during testing and modification. Compared to existing perforation-acidizing-test strings, this effectively reduces the problem of oil-casing cross-contamination caused by packer failure during acidizing. Simultaneously, the lower tubing and screen of the mechanical packer utilize high-strength, thick-walled tubing within the casing's allowable range, resisting higher perforation detonation effects, thereby reducing problems such as perforation gun and screen breakage and improving the success rate of oil testing. Attached Figure Description

[0049] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0050] Figure 1 This is a schematic diagram of the structure of a gas well test string according to the present invention;

[0051] Figure 2 This is a partial cross-sectional view of a kill sleeve in a gas well test string according to the present invention.

[0052] The attached diagram shows the markings and corresponding component names:

[0053] 1. First tubing 2. Second tubing 3. Expansion joint 4. Third tubing 5. APR testing tool 6. Safety joint 7. Packer 8. Kill sleeve 8. Upper connector 81. Claw 82. Soluble ball or steel ball 83. Shear pin 84. Sleeve 85. Claw sleeve 86. Lower connector 87. Rubber sealing ring 88. Fourth tubing 9. Screen pipe 10. Perforating gun assembly 11. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0055] Example

[0056] like Figure 1 As shown, this embodiment provides a gas well test string, including a screen pipe 10, a perforation gun assembly 11, and a first tubing 1, a second tubing 2, a third tubing 4, and a fourth tubing 9 connected coaxially in sequence.

[0057] An APR test tool 5 and a packer 7 are installed between the third oil pipe 4 and the fourth oil pipe 9. The two ends of the APR test tool 5 are connected to the lower end of the third oil pipe 4 and the upper end of the packer 7, respectively. The lower end of the packer 7 is connected to the upper end of the fourth oil pipe 9. The lower end of the fourth oil pipe 9 is connected to the upper end of the perforation gun assembly 11 through the screen pipe 10.

[0058] The lower end of the first oil pipe 1 is connected to the upper end of the second oil pipe 2, and an expansion joint 3 is connected between the lower end of the second oil pipe 2 and the upper end of the third oil pipe 4.

[0059] The upper and lower ends of the packer 7 are connected to a safety joint 6 and a kill sleeve 8, respectively. The upper and lower ends of the packer 7 are connected to the APR testing tool 5 and the fourth tubing 9 via the safety joint 6 and the kill sleeve 8, respectively. That is, the lower end of the third tubing 4 and the upper end of the mechanical packer 7 are connected via the APR testing tool 5 and the safety joint 6, and the lower end of the mechanical packer 7 and the upper end of the fourth tubing 9 are connected via the kill sleeve 8.

[0060] In this embodiment, the upper end of the packer 7 is connected to the safety joint 6 and the kill sleeve 8, which ensures that the APR testing tool 5 or the packer 7 can be smoothly retrieved when the tubing gets stuck, ensuring successful downhole data acquisition. At the same time, the kill sleeve 8 at the lower end of the packer 7 can establish a circulation channel, effectively avoiding the influence of trapped gas at the bottom of the packer 7.

[0061] like Figure 2 As shown, the pressure sleeve 8 includes an upper connector 81, a jaw 82, a lower connector 87, and a jaw sleeve 86. The upper connector 81 and the jaw 82, and the lower connector 87 and the jaw sleeve 86 of the pressure sleeve 8 are all connected by threads. At the same time, two rubber sealing rings 88 are provided between the upper connector 81 and the jaw 82, and between the lower connector 87 and the jaw sleeve 86.

[0062] The claw 82 has a split structure and a certain degree of elasticity. A sliding sleeve 85 is installed in the inner hole of the claw 82, and the sliding sleeve 85 is connected to the claw 82 by a shear pin 84. At the same time, the upper end of the sliding sleeve 85 is sealed with four rubber sealing rings, and the lower end is used to support the claw 82 to prevent the claw 82 from bending and retracting, which could lead to accidental loss of hand.

[0063] like Figure 2 The well-killing sleeve 8 shown is equipped with a claw mechanism. During assembly, the split claw 82 is inserted into the groove of the outer claw sleeve 86, and then supported by the inner sleeve 85 to prevent retraction. A soluble ball or steel ball 83 is dropped into the wellhead to seal the inner end face of the sleeve 85, pressurizing the tubing string. Under the pressure of the tubing, the sleeve 85 shears the shear pin 84 and descends to the support cone surface inside the slip hole, unlocking the overload protection release function. When encountering abnormal tension or pressure exceeding the set threshold, the claw 82 slides out of the claw sleeve 86, thereby achieving rapid separation of the sleeve 85 from the test tubing string.

[0064] In this embodiment, the expansion joint 3 is a full-bore structure. The expansion joint 3 can expand and contract, and when inserted into the well in a stretched state, it can be used to compensate for the shortening of the test tubing during acidizing, ensuring that the suspended weight of the lower tubing can be effectively applied to the packer 7. The expansion joint is a full-bore structure, and its lower end is connected to the third tubing 4, or it can be located in the second tubing 2.

[0065] In this embodiment, the first tubing 1, the second tubing 2, the third tubing 4 and the APR testing tool 5 above the packer 7 are all connected by a gas-tight coupling. This gas-tight coupling is existing technology and can be used in the existing tubing casing gas-tight coupling to meet the high-pressure gas well testing requirements.

[0066] The third oil pipe 4 is a thick-walled oil pipe, and its length should be determined according to the effective suspension weight required on the upper part of the mechanical packer 7. The second oil pipe 2 can be a thin-walled oil pipe according to the test conditions to reduce the weight of the test string. The wall thickness of the first oil pipe 1 is not less than the wall thickness of the second oil pipe 2, and the first oil pipe 1, the second oil pipe 2, and the third oil pipe 4 form a dumbbell-shaped structure, that is, the outer diameter of the second oil pipe 2 is smaller than the outer diameters of the first oil pipe 1 and the third oil pipe 4, thus forming a dumbbell-like structure. The expansion joint 3 is located in the middle of the dumbbell-shaped structure.

[0067] The APR testing tool 5 can be configured with different APR testing tools 5 according to testing requirements and downhole conditions, and has functions such as recording downhole temperature and pressure, circulation, and downhole shut-in. In one embodiment, the APR testing tool 5 can be configured according to testing requirements, and can be a pressure-controlled downhole tool or a mechanical downhole tool, and should also be equipped with a downhole shut-in tool.

[0068] In one embodiment, the fourth tubing 9 should be selected as a high-strength, thick-walled tubing as possible within the allowable range of the production casing, and the length of the fourth tubing 9 should not be less than 50m, in order to reduce the problem of packer 7 losing its seal or tubing breaking off due to perforation detonation, and at the same time, its lower end should be close to the production layer.

[0069] The strength of the screen tube 10 is not lower than that of the fourth oil tube 9, and it is used to establish a gas flow channel.

[0070] Another embodiment also discloses a gas well testing method, comprising the following steps:

[0071] 1) Clean and test the wellbore to ensure it meets the requirements for testing operations. Specifically: scrape the casing of the oil layer, clean the well, flush the well with clean water, perform a full wellbore pressure test, and conduct a drainage test to confirm that the wellbore is clean and meets the requirements for testing operations.

[0072] 2) Run one of the above-mentioned gas well test tubing strings into clean water. After reaching the perforation position, perform electrical depth calibration and adjust the tubing string depth to meet the perforation requirements. Connect the tubing hanger and drop the ball to set the packer.

[0073] After setting the packer, continue to press down the tubing string to compress the expansion joint into place and set the tubing hanger and tighten the set screw;

[0074] 3) Disassemble the blowout preventer assembly, install the gas wellhead, connect the pipeline between the wellhead and the surface process, and test the pressure according to the regulations.

[0075] 4) Pressurize the annular space to verify the packer's sealing performance and confirm that the packer is properly set.

[0076] 5) Optimize the perforation parameters based on the simulation results of the perforation detonation load verification, pressurize and detonate the perforation gun group in the oil pipe, and monitor the perforation situation; in this embodiment, the perforation parameters of the perforation gun group are optimized based on the simulation results of the perforation detonation load verification, and the perforation gun group adopts segmented delayed perforation. This scheme can reduce the perforation detonation load.

[0077] 6) Open the well for drainage, testing, and acidizing to obtain formation fluid properties and production capacity; during the stimulation process, the annular balance pressure control should take into account the pressure control of the oil layer casing and APR testing tools.

[0078] 7) After the test, the ball is dropped into the tubing to open the clamping sleeve for well control and to pressurize the lower packer gas back to the formation. Specifically: after the test, a certain amount of clean water is first injected into the tubing, then the ball is dropped to open the well control sleeve 8, and well control fluid is further injected to pressurize the annular gas (which may be high in sulfur) into the formation. The annular gas is pressurized and the circulation valve in the APR test tool 5 is opened to achieve downhole shut-in. At the same time, the tubing circulation channel is established for circulation well control.

[0079] 8) After dismantling the gas wellhead and installing the blowout preventer assembly, remove the test string after unsealing the packer. If the packer cannot be unsealed, release it from safety joint 6 and remove the upper test string; if the lower perforation gun assembly gets stuck, since the sliding sleeve 85 has already descended and opened, the split-type chuck 82 is no longer constrained by the sliding sleeve 85 and will radially shrink and deform along the bearing surface until it disengages from the chuck sleeve 86, thus allowing you to release it and remove the upper test string, ensuring successful downhole data acquisition.

[0080] This completes the entire operation. Mechanical packers should, in principle, not be used downhole for more than 15 days (from the start of setting) to avoid aging of the rubber components under prolonged high-temperature conditions, which could prevent the packer from being released.

[0081] In summary, the test string provided in the embodiments of this invention, due to its dumbbell-shaped structure, effectively transfers the suspended weight to the mechanical packer during testing and modification. Compared to existing perforation-acidizing-test strings, this significantly reduces the problem of oil-casing cross-contamination caused by packer failure during acidizing. Furthermore, the lower tubing and screen of the mechanical packer, within the allowable range of casing specifications, utilize high-strength, thick-walled tubing, which can resist higher perforation detonation effects, thereby reducing problems such as perforation gun and screen breakage and improving the success rate of oil testing.

[0082] It should be noted that the above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0083] In the description of this invention, it should be noted that the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0084] In the description of this document, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the attached drawings. They are only used to describe the relative positional relationship between the components or parts and do not specifically limit the specific installation orientation of each component or part.

[0085] In the description of this document, some terms may be used to indicate not only orientation or positional relationship, but also other meanings. For example, the term "above" may also be used in some cases to indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific circumstances.

[0086] In the description of this document, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0087] The structures, proportions, sizes, etc., drawn in the accompanying drawings in this application are only used to complement the content disclosed in this technical disclosure for those skilled in the art to understand and read, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modification of the structure, change of the proportion relationship, or adjustment of the size shall still fall within the scope of the technical content disclosed in this application, provided that it does not affect the effect and purpose that this application can produce.

[0088] The terminology used in this document is that which is currently widely used in the art in consideration of the functionality of this disclosure; however, these terms may vary depending on the intent, precedent, or new technology of those skilled in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of this disclosure. Therefore, the terminology used in this document should not be construed as simple names, but rather based on the meaning of the terms and the overall description of this disclosure.

[0089] This document uses flowcharts or text to illustrate the operational steps performed according to embodiments of this application. It should be understood that the operational steps in the embodiments of this application are not necessarily performed precisely in the order described. Instead, as needed, various steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more operations can be removed from these processes.

[0090] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A gas well test string, characterized in that, It includes a screen tube, a perforating gun assembly, and a first oil pipe, a second oil pipe, a third oil pipe, and a fourth oil pipe connected coaxially in sequence; An APR testing tool and a packer are provided between the third oil pipe and the fourth oil pipe. The two ends of the APR testing tool are connected to the lower end of the third oil pipe and the upper end of the packer, respectively. The lower end of the packer is connected to the upper end of the fourth oil pipe. The lower end of the fourth oil pipe is connected to the upper end of the perforation gun assembly through the screen pipe. The lower end of the first oil pipe is connected to the upper end of the second oil pipe, and a telescopic joint is connected between the second oil pipe and the third oil pipe.

2. The gas well test string according to claim 1, characterized in that, The expansion joint is a full-bore structure, and its lower end is connected to the third oil pipe or located in the second oil pipe.

3. The gas well test string according to claim 1, characterized in that, The packer is connected to a safety joint and a kill sleeve at its upper and lower ends, respectively. The packer is connected to the APR testing tool and the fourth tubing at its upper and lower ends, respectively, through the safety joint and the kill sleeve.

4. The gas well test string according to claim 1, characterized in that, The first, second, and third oil pipes above the packer, as well as the APR testing tool, are all connected using an airtight coupling.

5. A gas well test string according to claim 1, characterized in that, The third oil pipe is a thick-walled oil pipe, the second oil pipe is a thin-walled oil pipe, the wall thickness of the first oil pipe is not less than the wall thickness of the second oil pipe, and the first oil pipe, the second oil pipe and the third oil pipe form a dumbbell-shaped structure.

6. A gas well test string according to claim 1, characterized in that, The APR testing tool is a pressure-controlled downhole tool or a mechanical downhole tool.

7. A gas well test string according to claim 1, characterized in that, The fourth oil pipe is a thick-walled oil pipe, and the length of the fourth oil pipe is not less than 50m.

8. A gas well test string according to claim 1, characterized in that, The strength of the screen tube is not lower than that of the fourth oil tube.

9. A gas well testing method, characterized in that, Includes the following steps: The wellbore is cleaned and tested to ensure it meets the requirements for testing operations. A gas well test string as described in any one of claims 1 to 8 is lowered into clean water. After reaching the perforation position, electrical depth calibration is performed to adjust the tubing string depth to meet the perforation requirements. The tubing hanger is connected, and the packer is set with a ball. After setting the packer, continue to press down the tubing string, compress the expansion joint into place, set the tubing hanger, and tighten the top screw; disassemble the blowout preventer assembly, install the gas wellhead, connect the pipeline between the wellhead and the surface process, and test the pressure according to the regulations. Annular pressure testing was performed on the packer to confirm that the packer was properly set. The perforation gun assembly was detonated by pressurizing inside the oil pipe, and the perforation status was monitored. Well opening is conducted for fluid drainage, testing, and acidizing to obtain information on formation fluid properties and production capacity. After the test, the ball was dropped into the tubing to squeeze and kill the well. The packer's lower trap gas pressure was returned to the formation. The annulus was pressurized and the circulation valve in the APR test tool was opened to achieve downhole shut-in. At the same time, the oil casing circulation channel was established to perform circulation kill. After dismantling the gas wellhead, installing the blowout preventer assembly, and unsealing the packer, the test string was pulled out.

10. A gas well testing method according to claim 9, characterized in that, The perforating gun group optimizes the perforation parameters based on the simulation results of the perforation detonation load verification, and the perforating gun group adopts segmented time-delay perforation.

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