Double-packer well completion pipe string for deep high-temperature and high-pressure gas well

Abstract

The invention discloses a deep high-temperature and high-pressure gas well double-packer well completion pipe string which comprises a tubing hanger, an underground pipe string inner blowout prevention device and a first casing packer which are sequentially connected, the underground pipe string inner blowout prevention device is connected with the first casing packer through a first oil pipe, and the bottom of the first oil pipe is connected with a second oil pipe. A telescopic pipe, a fracturing sliding sleeve, a second casing packer, a full-bore fracturing sliding sleeve and a ball seat are sequentially connected to the second oil pipe, the telescopic pipe is arranged between the double packers, it is ensured that the telescopic pipe is in a closed state before fracturing operation by controlling the telescopic pipe, and during fracturing operation, a telescopic short joint is in an open state; and the ball seat extends to the upper part of an artificial well bottom, so that during well completion fluid replacement, it is ensured that fluid replacement in a well shaft is clean, original drilling mud is not left, and mud precipitation is not caused.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas well testing and completion technology, in particular to a deep-layer high-temperature and high-pressure gas well double-packer completion string. Background Art

[0002] Deep high-pressure natural gas has become one of the main resources for natural gas capacity construction. The capacity construction period of deep gas wells is long and the investment amount is large. Therefore, it is necessary to increase the single well production as much as possible, so as to improve the efficiency and economic benefits of capacity construction. However, the reservoirs of deep high-temperature and high-pressure natural gas burial formations generally have low porosity, high temperature and high pressure, so it is necessary to fracturing and transform the reservoir to increase the single well production. Temporary plugging stratification, bridge plug segmentation and multi-packer stratification are common process measures for reservoir fracturing transformation. However, limited by the steering effect and wellhead pressure, temporary plugging stratification fracturing and bridge plug segmentation fracturing are not suitable for deep high-temperature and high-pressure environments. Therefore, multi-packer stratification has become an inevitable choice for stratified fracturing transformation of high-temperature and high-pressure gas reservoirs.

[0003] However, affected by the wellbore temperature and pressure, temperature and pressure effects and the diameter of the packer, the multi-packer stratified fracturing process in high-temperature and high-pressure gas wells is prone to problems such as packer failure, insufficient return of steel balls and drilling fluid, blockage of the tubing and breakage of the packer core shaft, which seriously affects the subsequent production and data acquisition, causes secondary contamination of the reservoir and makes well repair difficult. Summary of the invention

[0004] The purpose of the present invention is to provide a double-packer completion string for deep, high-temperature and high-pressure gas wells, so as to overcome the problems in the prior art that packer failure, insufficient return of drilling fluid, plugging of the string and breaking of the packer core shaft easily occur in the well, which seriously affect the later production and data acquisition, cause secondary pollution of the reservoir and make it difficult to repair the well.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A double-packer completion string for a deep, high-temperature, and high-pressure gas well comprises a tubing hanger, a blowout preventer in a downhole tubing string, and a first casing packer connected in sequence, wherein the blowout preventer in the downhole tubing string and the first casing packer are connected via a first tubing, a second tubing is connected to the bottom of the first tubing, a telescopic pipe, a fracturing sleeve, a second casing packer, a full-bore fracturing sleeve, and a ball seat are connected to the second tubing in sequence, a first casing is also arranged outside the tubing hanger, the blowout preventer in the downhole tubing string, and the first casing packer, and a second casing is arranged outside the telescopic pipe, the fracturing sleeve, the second casing packer, the full-bore fracturing sleeve, and the ball seat.

[0007] Preferably, the blowout preventer in the downhole tubing string comprises a safety valve pipeline, an upper flow nipple, a downhole safety valve and a lower flow nipple, wherein one end of the upper flow nipple is connected to the oil pipe hanger and the other end is connected to the downhole safety valve, one end of the safety valve pipeline passes through the oil pipe and is hung on the ground, and the other end is connected to the downhole safety valve, and one end of the lower flow nipple is connected to the downhole safety valve, and the other end is connected to the first oil pipe.

[0008] Preferably, the buckle types of the first oil pipe and the second oil pipe are both airtight buckles.

[0009] Preferably, the first casing packer and the second casing packer are set by hydraulic setting and released by drilling and grinding.

[0010] Preferably, the first casing packer and the second casing packer are set with soluble balls.

[0011] Preferably, the first casing packer is a Y443 type packer, and the second casing packer is a Y441 type packer.

[0012] Preferably, the first casing packer has a size greater than that of the second casing packer.

[0013] Preferably, the fracturing sleeve comprises an outer sleeve and an inner sleeve, the outer sleeve is provided with radial holes, and the inner sleeve is provided with shear pins, and the shear pins are fixed to block the radial holes of the outer sleeve.

[0014] Preferably, the ball seat is connected to the second oil pipe via a pin.

[0015] Preferably, a first reservoir flow channel hole and a second reservoir flow channel hole are formed on the second casing, wherein the first reservoir flow channel hole is parallel to the position of the fracturing sleeve, and the second reservoir flow channel hole is parallel to the position of the full-bore fracturing sleeve.

[0016] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a deep-layer, high-temperature and high-pressure gas well double-packer completion string, wherein a telescopic tube is arranged between the double packers, and the telescopic tube is controlled to ensure that the telescopic tube is in a closed state before the fracturing operation. During the fracturing operation, the telescopic short joint is in an open state, thereby avoiding excessive axial force between the packers during fracturing, causing failure of the packers, and extending the ball seat to the upper part of the artificial well bottom. When replacing the fluid during completion, it is ensured that the replaced fluid in the wellbore is clean, without leaving the original drilling mud, and without causing mud precipitation.

[0017] Furthermore, the position of the fracturing sleeve was adjusted to correspond to the position of the first reservoir flow channel hole on the second casing, and the position of the fracturing sleeve was adjusted to correspond to the position of the second reservoir flow channel hole on the second casing, forming a large-plus-small layered fracturing completion string, and the diameter of the string became larger, providing a favorable channel for later construction.

[0018] Furthermore, the first casing packer is a Y443 type packer, and the second casing packer is a Y441 type packer. A large-size packer and a small-size packer are combined to improve the ability of the tubing to be lowered, avoid the phenomenon of multiple packers encountering resistance when being lowered into a small-size tail pipe, and avoid accidents.

[0019] Furthermore, the telescopic tube includes an outer tube and an inner tube, the inner tube is sleeved in the outer tube and fixed with a shear pin. When the axial force on the pipe column is greater than the shear value of the shear pin, the pin is sheared and the length of the telescopic tube changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the double packer completion string structure of a deep high-temperature and high-pressure gas well according to the present invention;

[0021] In the figure, 1-first casing, 2-second casing, 210-first reservoir flow channel hole; 211-second reservoir flow channel hole; 3-tubing hanger; 401-safety valve pipeline; 402-upper flow nipple; 4-downhole safety valve; 403-lower flow nipple; 5-first tubing; 6-first packer; 7-variable buckle; 8-second tubing; 9-telescopic tube; 10-fracturing sleeve; 11-second packer; 12-full-bore fracturing sleeve; 13-ball seat; 14-artificial well bottom. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0025] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0026] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0029] like Figure 1 The present invention provides a deep high-temperature and high-pressure gas well double packer completion string, comprising:

[0030] The first casing 1, the second casing 2, the first reservoir flow channel hole 210; the second reservoir flow channel hole 211; the tubing hanger 3; the safety valve pipeline 401; the upper flow nipple 402; the downhole safety valve 4; the lower flow nipple 403; the first tubing 5; the first packer 6; the buckle 7; the second tubing 8; the telescopic pipe 9; the fracturing sleeve 10; the second packer 11; the full-bore fracturing sleeve 12; the ball seat 13 and the artificial well bottom 14.

[0031] The specific structure of the embodiment of the present invention is:

[0032] A deep-layer high-temperature and high-pressure gas well double-packer completion string comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence, the blowout preventer in the downhole tubing string and the first casing packer 6 being connected via a first tubing 5, a second tubing 8 being connected to the bottom of the first tubing 5, a telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 being connected in sequence to the second tubing 8, a first casing 1 being also arranged outside the tubing hanger 3, the blowout preventer in the downhole tubing string and the first casing packer 6, and a second casing 2 being arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0033] Furthermore, in the embodiment of the present invention, one end of the buckle 7 is an upper large-sized airtight buckle, and the other end is a lower small-sized airtight buckle.

[0034] Furthermore, the tubing hanger is a device that supports the downhole tubing and seals the annular space between the tubing and the casing. It uses the tubing's gravity to sit inside the large four-way cone and seal it, making it easy to operate and fast and safe to change the wellhead.

[0035] In this embodiment, a telescopic tube is arranged between the double packers, and the telescopic tube is controlled to ensure that the telescopic tube is in a closed state before the fracturing operation. During the fracturing operation, the telescopic nipple is in an open state, thereby avoiding excessive axial force between the packers during fracturing, which may cause the packers to fail, and extending the ball seat to the upper part of the artificial well bottom. When replacing the fluid during completion, it is ensured that the replaced fluid in the wellbore is clean, without leaving the original drilling mud, and without causing mud precipitation.

[0036] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0037] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0038] The blowout prevention device in the downhole tubing string includes a safety valve pipeline 401, an upper flow nipple 402, a downhole safety valve 4 and a lower flow nipple 403. The safety valve pipeline 401 and the upper flow nipple 402 are connected between the oil pipe hanger 3 and the downhole safety valve 4, wherein the safety valve pipeline 401 passes through the oil pipe hanger 3 to the ground, and the lower flow nipple 403 is connected to the lower end of the downhole safety valve 4.

[0039] In this embodiment, the blowout preventer in the downhole tubing is arranged in such a way as to ensure that the downhole well can be shut down quickly. Its safety valve pipeline connects the downhole safety valve and the ground control device, so that the ground fluid pressure can be transmitted to the downhole safety valve to shut down and open the well. The main function of the upper and lower flow short sections is to reduce the impact of the fluid disturbance in the well on the safety valve and enhance the safety of the tubing.

[0040] Furthermore, the downhole safety valve 4 mainly includes a piston, a spring, a valve plate and a valve plate seat. When hydraulic pressure is applied from the ground, high-pressure liquid enters the piston cavity through the control pipeline, pushes the piston downward, compresses the spring, and pushes the valve plate to open it; maintains the ground control pressure, that is, maintains the open state; releases the ground control pressure, and the valve plate is reset under the action of the spring to close it. In abnormal situations, it can be closed urgently to prevent blowouts and ensure the safety of oil and gas well production.

[0041] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0042] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0043] Furthermore, the buckle types of the first oil pipe 5 and the second oil pipe 8 are both airtight buckles.

[0044] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0045] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0046] The first casing packer 6 and the second casing packer 11 are arranged with compression rubber sleeve sealing, double slip fixation, hydraulic setting and drilling and grinding release.

[0047] In this embodiment, the packer arranged in this way is stable, has a long service life, and is not easily damaged.

[0048] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0049] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0050] Furthermore, the first casing packer and the second casing packer are set by soluble balls.

[0051] As high-density steel balls are difficult to return after getting stuck, we developed soluble balls made of high-strength soluble aluminum alloy with a special protective film on the surface.

[0052] When the soluble ball protective film contacts with the solution, the dissolution speed is slow. After the protective film is completely dissolved, the main body contacts with the solution. The main body material dissolves faster than the protective film, which speeds up the dissolution speed. The soluble ball will not block the production channel and affect the later production and wellbore operations.

[0053] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0054] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0055] Furthermore, the first casing packer 6 is a Y443 type packer, and the second casing packer 11 is a Y441 type packer.

[0056] In this embodiment, a large-sized packer and a small-sized packer are combined to improve the running capability of the pipe string, avoid the phenomenon that multiple packers are blocked when running into a small-sized tail pipe, and avoid accidents.

[0057] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0058] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0059] Further, a size of the first casing packer is greater than a size of the second casing packer.

[0060] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0061] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0062] Furthermore, the fracturing sleeve 10 includes an outer sleeve and an inner sleeve. The outer sleeve is provided with radial holes, and the inner sleeve is provided with shear pins to fix and cover the radial holes of the outer sleeve.

[0063] In this embodiment, when the shear pin is cut off, the inner sleeve is displaced, so that the inner sleeve and the outer sleeve of the sliding sleeve are connected.

[0064] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0065] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0066] Furthermore, the ball seat 13 is connected to the second oil pipe 8 via a pin.

[0067] In this embodiment, after the ball is dropped into the seat, it is pressurized, and after the pin is cut off, the ball seat 13 and the ball fall into the bottom of the well together, and the ball seat 13 is extended to the upper part of the artificial well bottom. When the well is completed and the fluid is replaced, it is ensured that the replacement fluid in the wellbore is clean, and no original drilling mud is left, and mud precipitation will not be caused.

[0068] Another embodiment of the present invention provides a deep high-temperature and high-pressure gas well double packer completion string with a specific structure as follows:

[0069] It comprises a tubing hanger 3, a blowout preventer in a downhole tubing string and a first casing packer 6 which are connected in sequence. The blowout preventer in the downhole tubing string and the first casing packer 6 are connected via a first tubing 5. A second tubing 8 is connected to the bottom of the first tubing 5. A telescopic pipe 9, a fracturing sleeve 10, a second casing packer 11, a full-bore fracturing sleeve 12 and a ball seat 13 are connected to the second tubing 8 in sequence. A first casing 1 is also arranged outside the tubing hanger 3, the blowout preventer in a downhole tubing string and the first casing packer 6. A second casing 2 is arranged outside the telescopic pipe 9, the fracturing sleeve 10, the second casing packer 11, the full-bore fracturing sleeve 12 and the ball seat 13.

[0070] Furthermore, a first reservoir flow channel hole 210 and a second reservoir flow channel hole 211 are formed on the second casing 2 . The first reservoir flow channel hole 210 is parallel to the fracturing sleeve 10 , and the second reservoir flow channel hole is parallel to the full-bore fracturing sleeve 12 .

[0071] In this embodiment, a large-plus-small layered fracturing completion string is formed, and the diameter of the string becomes larger, providing a favorable channel for later construction.

[0072] The present invention improves the stress condition of the packer during the transformation process by taking into account several aspects, such as the completion string, the properties of the ball dropping and the structure of the full-bore fracturing valve, and increases the diameter of the string. This solves the problem of the string being blocked by the retained ball dropping, improves the fluid replacement efficiency of the wellbore, and achieves good application effects, thus providing technical support for the construction of deep-layer natural gas production capacity and efficient production.

[0073] Directions:

[0074] According to the wellbore conditions, adjust the length of the airtight oil pipe to ensure that the ball seat 13 in the pipe string is located about 15 meters above the artificial well bottom 14; ensure that the full-bore fracturing sleeve 12 and the second reservoir flow channel hole 211 are in the same position; ensure that the fracturing sleeve 10 and the first reservoir flow channel hole 210 are in the same position; the second packer 11 and the first packer 6 are set at a position away from the casing coupling position; the first packer 6 is set at the first oil pipe root diameter, and check the quality of the oil pipe airtight seal thread connection to ensure sealing.

[0075] When lowering the double packer stratified fracturing string for deep high-temperature and high-pressure gas wells of the present invention, attention should be paid to steady and uniform speed during the lowering process, and sudden lifting, sudden braking and sudden release are not allowed. The tonnage should not exceed 20KN when encountering resistance, and falling objects in the well should be strictly prevented to prevent the string from being stuck. When encountering resistance, it is strictly forbidden to force it through hard to damage the packer rubber cylinder or downhole tools.

[0076] When the downhole safety valve 4 is lowered, there is no well control measure for the lowered control pipeline 401 during the drilling process. The wellhead is prepared with a control pipeline shearing tool, a tubing buckle, an internal blowout prevention tool, a blowout prevention single root or a blowout prevention column. After the pipe string is lowered into place, the pipe string is adjusted to ensure that the first packer 6 and the second packer 11 are set away from the casing collar.

[0077] Close the downhole safety valve 4, pass the safety valve control pipeline 401 through the oil pipe hanger 3, lower the pipe string to sit and tighten the top screw; remove the blowout preventer group, complete the safety valve control pipeline 401 passing through the oil production spool, and switch the downhole safety valve 4 to verify whether the control pipeline is unobstructed; open the downhole safety valve 4, and use the well annulus protection fluid to displace the well pressure fluid in the well in a small amount.

[0078] After the replacement of fluid is completed, the ball is dropped into the ball seat 13, and the ball is seated, and the first packer 6 and the second packer 11 are sealed by graded positive pressure, and then the first packer 6 is tested by annular pressure. After the test is qualified, the ball seat is knocked down by positive pressure. The ball is dropped to open the full-bore fracturing sleeve 12. The second reservoir flow channel hole 211 is transformed by sand fracturing, and the fracturing fluid flows out from the side holes of the full-bore fracturing sleeve 12 and the ball seat 13, and enters the second reservoir flow channel hole 211, so as to communicate and activate the natural fracture system, expand the reservoir percolation volume, improve the conductivity of the near-well fracture, and reduce the production pressure difference.

[0079] After the transformation, different nozzles are used to release and spray to obtain the reservoir production. The upper reservoir is transformed. Because it is difficult for steel balls to return, soluble balls are put into the wellhead. When the soluble balls reach the fracturing sleeve 10, the side holes of the fracturing sleeve 10 are opened, and the inner diameter of the pipe string is blocked at the same time, so that the fracturing fluid flows out from the side holes of the fracturing sleeve 10 and enters the first reservoir flow channel hole 210, forming high-conductivity artificial fractures in the upper reservoir flow channel, connecting natural fractures as much as possible, increasing the reservoir leakage area, and improving the single well production.

[0080] Layered fracturing and combined production: The deep-layer high-temperature and high-pressure double-packer layered fracturing technology has been applied many times on site and has achieved significant results.

[0081] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields, and the above-mentioned specific embodiments are only illustrative and instructive, rather than restrictive. Under the guidance of the specification, a person skilled in the art can also make many forms without departing from the scope of protection of the claims of the present invention, all of which belong to the scope of protection of the present invention.

Claims

1. A double packer completion string for deep, high-temperature and high-pressure gas wells, characterized in that: The invention comprises a tubing hanger (3), a blowout prevention device in a downhole tubing column and a first casing packer (6) which are connected in sequence. The blowout prevention device in the downhole tubing column and the first casing packer (6) are connected via a first tubing (5). A second tubing (8) is connected to the bottom of the first tubing (5). A telescopic pipe (9), a fracturing sleeve (10), a second casing packer (11), a full-bore fracturing sleeve (12) and a ball seat (13) are connected to the second tubing (8) in sequence. A first casing (1) is also arranged outside the tubing hanger (3), the blowout prevention device in a downhole tubing column and the first casing packer (6). A second casing (2) is arranged outside the telescopic pipe (9), the fracturing sleeve (10), the second casing packer (11), the full-bore fracturing sleeve (12) and the ball seat (13).

2. The deep high-temperature and high-pressure gas well double packer completion string according to claim 1, characterized in that: The blowout prevention device in the downhole tubing string comprises a safety valve pipeline (401), an upper flow nipple (402), a downhole safety valve (4) and a lower flow nipple (403); one end of the upper flow nipple (402) is connected to the oil pipe hanger (3) and the other end is connected to the downhole safety valve (4); one end of the safety valve pipeline (401) passes through the oil pipe hanger (3) to the ground and the other end is connected to the downhole safety valve (4); one end of the lower flow nipple (403) is connected to the downhole safety valve (4) and the other end is connected to the first oil pipe (5).

3. The deep high-temperature and high-pressure gas well double packer completion string according to claim 1, characterized in that: The buckle types of the first oil pipe (5) and the second oil pipe (8) are both airtight buckles.

4. The deep high-temperature and high-pressure gas well double packer completion string according to claim 1, characterized in that: The first casing packer (6) and the second casing packer (11) are set by hydraulic setting and released by drilling and grinding.

5. The deep high-temperature and high-pressure gas well double packer completion string according to claim 4, characterized in that: The first casing packer (6) and the second casing packer (11) are set using soluble balls.

6. The deep-layer high-temperature and high-pressure gas well double packer completion string according to claim 1, characterized in that: The first casing packer (6) is a Y443 type packer, and the second casing packer (11) is a Y441 type packer.

7. The deep-layer high-temperature and high-pressure gas well double packer completion string according to claim 1, characterized in that: The size of the first casing packer (6) is greater than the size of the second casing packer (11).

8. The deep high-temperature and high-pressure gas well double packer completion string according to claim 1, characterized in that: The fracturing sleeve (10) comprises an outer sleeve and an inner sleeve, wherein the outer sleeve is provided with radial holes, and the inner sleeve is provided with shear pins, wherein the shear pins are fixed and cover the radial holes of the outer sleeve.

9. The deep-layer high-temperature and high-pressure gas well double packer completion string according to claim 1, characterized in that: The ball seat (13) is connected to the second oil pipe (8) via a pin.

10. The deep-layer high-temperature and high-pressure gas well double packer completion string according to claim 1, characterized in that: The second casing (2) is provided with a first reservoir flow channel hole (210) and a second reservoir flow channel hole (211); the first reservoir flow channel hole (210) is parallel to the position of the fracturing sleeve (10), and the second reservoir flow channel hole is parallel to the position of the full-bore fracturing sleeve (12).

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