Method for remodeling complete wellbore in unconventional natural gas downhole return development

Abstract

The invention relates to the technical field of unconventional natural gas well remodeling, in particular to a method for remodeling a complete wellbore in unconventional natural gas well downward return development, and the method comprises the following steps: determining parameters of each part of an expansion pipe according to basic information of an original well and working conditions of the wellbore, and preprocessing the wellbore of the original well; an expansion pipe is tripped into the pretreated original well shaft to reach the position of the perforation section, expansion operation is carried out, and the perforation section is blocked; and a complete shaft is remodeled for unconventional natural gas downward returning development. The method can meet the requirement for the pressure bearing capacity of 50 MPa or above of follow-up downward-returning development, operation is safe and controllable, meanwhile, secondary development and utilization of old wells are achieved, the transformation cost is low, high investment and high risks caused by re-drilling are avoided, and economic benefits are maximized. The problem that in the prior art, due to the fact that plugging bearing pressure is low, a perforated wellbore is difficult to bear downward-returning development high pressure, and downward-returning development requirements cannot be met is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of unconventional natural gas well remodeling, and in particular to a method for realizing complete wellbore remodeling during underground redevelopment of unconventional natural gas wells. Background Art

[0002] Affected by geological factors such as the sedimentary environment, common oil and gas resources are often distributed in multiple layers in the same vertical direction. In the early stage of development, for the sake of full life cycle management and economic benefit value of oil and gas reservoir development, priority is given to developing the best-developed and largest-scale strata in the entire oil and gas reservoir. After the resources in the main strata are exhausted, further comprehensive consideration is given to utilizing the existing old well network or redeploying new wells to develop other overlying or underlying strata.

[0003] With the continuous innovation of reservoir transformation technology, unconventional natural gas resources or low-grade oil and gas resources such as shale gas and deep coalbed methane have been developed economically by utilizing large-scale factory-based fracturing methods with large liquid volume, large displacement, and large sand ratio. The maximum hydraulic fracturing pressure exceeds 50MPa, and in some areas it can reach over 70MPa.

[0004] Existing unconventional natural gas reservoirs such as shale gas and deep coalbed methane are mainly affected by factors such as abnormally dense reservoirs and coal seam adsorption. By increasing the scale of fracturing transformation, the fracturing wellhead pressure exceeds 50MPa, and a certain scale of artificial fractures are established in the formation, the single well production can be increased and the economic benefits can be maximized. For developed old wells, if the lower natural gas layer is to be developed, the existing development method is mainly to perform full-well hydraulic fracturing after new drilling and perforation. For the existing developed gas wells, the resources in their main production layers are exhausted and they are often shut in because they have drilled through multiple natural gas layers below. If they are to be developed downward, the conventional idea is: first seal the upper perforated layer section, and then perform lower fracturing. There are two main types of existing sealing technologies. One is to configure cement, resin and other fluids on the ground and inject them into the perforated well section, and then seal the perforated holes through chemical processes such as solidification; the other method is mechanical, that is, first perforate the lower part, and then run a fracturing drill with a mechanical packer, use the packer to isolate the upper perforated section, and then perform large-scale hydraulic fracturing on the lower formation to be developed through the oil pipe according to the designed hydraulic fracturing scale.

[0005] The two existing technologies can generally withstand pressures within 35 MPa, and cannot meet the 50 MPa to 70 MPa or even higher wellbore pressures required for unconventional natural gas downstream development, and cannot meet the requirements for downstream development. Summary of the invention

[0006] In view of the problem in the prior art that the perforated wellbore is unable to withstand the high pressure of downhole development due to low plugging bearing pressure and cannot meet the demand of downhole development, the present invention provides a method for reshaping a complete wellbore in downhole development of unconventional natural gas.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for reshaping a complete wellbore during unconventional natural gas well recovery development includes the following steps:

[0009] Obtain the original well basic information and wellbore conditions;

[0010] Determine the parameters of each component of the expansion pipe according to the original well basic information and wellbore working conditions;

[0011] Pull out the original well pipe string and pre-treat the original wellbore;

[0012] According to the parameters of each component of the expansion tube, the expansion tube is lowered into the pre-treated original wellbore to the perforation section, and the expansion operation is performed, and the perforation section is sealed;

[0013] After plugging is completed, the bottom plug of the expansion pipe is removed to form a new wellbore channel;

[0014] Verify the sealing and passability of the new wellbore channel to complete the reconstruction of the entire wellbore.

[0015] Preferably, the basic information of the original well includes the original casing inner diameter, perforation section length, perforation section position and pressure bearing information of the original well to be developed.

[0016] Furthermore, according to the original well basic information and wellbore working conditions, the method for determining the parameters of each component of the expansion tube assembly is as follows:

[0017] Obtain the pressure bearing information of the original well, and select the material and wall thickness of the expansion pipe according to the pressure bearing information of the original well, so that the pressure bearing strength of the expansion pipe is greater than the maximum pressure bearing in the pressure bearing information of the original well;

[0018] Obtain the perforation section length of the original well, and determine the length of the expansion tube according to the perforation section length, so that (expansion tube length - perforation section length) ≥ 2.6m;

[0019] The original casing inner diameter of the original well is obtained, and the outer diameter of the expansion tube and the tool parameters of the expansion tube are determined according to the original casing inner diameter, so that the diameter of the expansion tube tool is smaller than the casing inner diameter, so that after the expansion tube is expanded, the distance between the outer diameter of the expansion tube and the original casing inner diameter is 2.5mm to 4.5mm.

[0020] Furthermore, the method for pre-treating the original wellbore is:

[0021] Clean the debris on the inner wall of the original wellbore;

[0022] After the debris on the inner wall of the original wellbore is cleaned, the inside of the original wellbore is circulated and washed to wash out the residue inside the wellbore;

[0023] After washing out the residue inside the original wellbore, the original casing in the original wellbore is tested for leaks;

[0024] After the leak test is qualified, the supplementary section of the perforated section inside the original wellbore is milled to complete the pretreatment of the original wellbore.

[0025] Furthermore, the method for leak detection of the original casing in the original wellbore is:

[0026] Lower the tool tubing with the packer into the original wellbore, and fill the original wellbore with clean water;

[0027] The packer lowered into the original wellbore is seated on the perforated section, and the wellhead of the original well is connected to the pressure-injection equipment to pressurize the casing annulus. The pressure is stabilized according to the target time, and the pressure drop is recorded to verify the sealing of the original casing above the perforated section.

[0028] After the sealing verification of the original casing at the upper part of the perforation section is completed, the packer lowered into the wellbore of the original well is seated at the lower end of the perforation section, and the wellhead of the original well is connected to the pressure-injection equipment to pressurize the tubing, stabilize the pressure according to the target time, record the pressure drop, and verify the sealing of the original casing at the lower part of the perforation section.

[0029] Preferably, when the packer lowered into the original wellbore is seated at the upper end of the perforation section, the packer is 2m to 5m away from the upper end of the perforation section; when the packer lowered into the original wellbore is seated at the lower end of the perforation section, the packer is 2m to 5m away from the lower end of the perforation section.

[0030] Furthermore, the expansion pipe is lowered into the pre-treated original wellbore to the perforation section, and the expansion operation is performed to seal the perforation section as follows:

[0031] Connect the tool oil pipe to the simulated wellbore pipe; the outer diameter of the simulated wellbore pipe is greater than or equal to the outer diameter of the expansion pipe, and the length of the simulated wellbore pipe is greater than or equal to the length of the expansion pipe;

[0032] The connected simulated well-draining pipe is lowered into the wellbore to the bottom of the perforation section to simulate well-draining;

[0033] After the simulated well cleaning is completed, the tool tubing is connected to the expansion tube and lowered into the original wellbore. When lowering into the original wellbore, the tool tubing is filled with clean water every 30 to 50 sections of the tool tubing until the expansion tube is lowered to the vicinity of the perforation section.

[0034] After the expansion pipe is lowered to the vicinity of the perforation section, the depth of the expansion pipe is calibrated;

[0035] According to the depth calibration result, continue to run the tool tubing until the perforation section is located in the middle section of the expansion tube;

[0036] The expansion operation is carried out to make the expansion tube close to the inner wall of the original casing of the original wellbore to complete the plugging of the perforation section.

[0037] Furthermore, the method for calibrating the depth of the expansion tube is as follows:

[0038] A gamma logging instrument is lowered into the tool tubing, and the gamma logging instrument is used to test the formation gamma curve from the wellhead downward to the expansion pipe section to obtain a new test gamma curve;

[0039] Obtain the original well gamma curve, compare the new test gamma curve with the original well gamma curve, and correct the actual well depth at the positioning short joint;

[0040] According to the actual well depth at the calibration positioning nipple, the distance between the current well depth position of the expansion pipe and the target position is calculated to complete the depth calibration;

[0041] or

[0042] According to the depth of the perforated section in the original wellbore, a drillable bridge plug is placed at a position 10m to 15m below the perforated section, and the distance between the bridge plug surface and a certain point in the perforated section is accurately recorded;

[0043] Use the tool tubing to lower the expansion pipe into the original wellbore until the drillable bridge plug surface encounters resistance;

[0044] Lift the pipe string. The lifting distance shall be based on the recorded distance between the bridge plug surface and a certain point in the perforation section. Ensure that the final perforation section is located in the middle of the expansion pipe and complete the depth calibration.

[0045] Preferably, a plurality of high-temperature and high-pressure vulcanized sealing rubber rings are respectively provided at both ends of the expansion tube in the expansion tube assembly.

[0046] Preferably, when the expansion tube assembly is expanded, the high-temperature and high-pressure vulcanized sealing rubber rings are arranged at both ends of the perforation section, and the distance between the high-temperature and high-pressure vulcanized sealing rubber ring closest to the end of the perforation section and the end of the perforation section is greater than 1.3 m.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention provides a method for remodeling a complete wellbore in the underground return development of unconventional natural gas. The method determines the parameters of each component of the expansion tube according to the basic information of the original well and the wellbore working conditions, pre-treats the original wellbore, lowers the expansion tube into the pre-treated original wellbore to the perforation section, performs expansion operation, and seals the perforation section; after the sealing is completed, removes the bottom plug of the expansion tube to form a new wellbore channel; verifies the sealing and passability of the new wellbore channel, and verifies that it is qualified, thereby realizing the remodeling of the complete wellbore for the underground return development of unconventional natural gas. The method can meet the pressure bearing capacity of more than 50MPa for subsequent return development, and the operation is safe and controllable. At the same time, the secondary development and utilization of old wells is realized, and the transformation cost is low, avoiding the high investment and high risk brought by re-drilling, and maximizing the economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of a method for realizing complete wellbore remodeling during downhole recovery of unconventional natural gas according to the present invention.

[0050] Figure 2 The present invention is a schematic diagram of leak testing of the original casing in the original wellbore for reshaping a complete wellbore during the downhole development of unconventional natural gas.

[0051] Figure 3 The present invention provides an expansion pipe and tool tubing connection structure for realizing the reconstruction of a complete wellbore during the development of unconventional natural gas downhole.

[0052] Figure 4 The present invention is a schematic diagram of an expansion process of an expansion tube for reshaping a complete wellbore during downhole recovery of unconventional natural gas.

[0053] Figure 5 The present invention is a schematic diagram of positioning a drillable bridge plug during expansion of an expandable tube for reshaping a complete wellbore during downhole recovery of unconventional natural gas.

[0054] Among them, 1-tool tubing, 2-packer, 3-positioning short joint, 4-expansion tube, 5-high temperature and high pressure vulcanized sealing rubber ring, 6-drillable bridge plug. DETAILED DESCRIPTION

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0062] See also Figure 1 The present invention discloses a method for reshaping a complete wellbore during the development of unconventional natural gas underground, comprising the following steps:

[0063] S1: Obtaining basic information of the original well and wellbore conditions; the basic information of the original well includes the original casing inner diameter, perforation section length and perforation section position of the original well to be developed, and the wellbore conditions include pressure information of the development.

[0064] S2: According to the original well basic information and wellbore working conditions, the parameters of each component of the expansion tube 4 are determined, specifically:

[0065] Obtain the downhole development pressure information of the original well, and select the material and wall thickness of the expansion pipe 4 according to the downhole development pressure information, so that the pressure strength of the expansion pipe 4 is greater than the maximum pressure in the downhole development pressure information; the wall thickness of the expansion pipe 4 is preferably 4mm to 8mm;

[0066] Obtain the length of the perforation section of the original well, and determine the length of the expansion tube 4 based on the perforation section length, so that (length of the expansion tube 4 - length of the perforation section) ≥ 2.6 m; generally, the maximum length of a single expansion tube 4 is 11 m. If the supplementary section of the perforation section is longer, multiple expansion tubes 4 can be connected by threading.

[0067] The original casing inner diameter of the original well is obtained, and the outer diameter of the expansion tube 4 and the tool parameters of the expansion tube 4 are determined according to the original casing inner diameter, so that the diameter of the tool of the expansion tube 4 is smaller than the casing inner diameter, so that after the expansion tube 4 is expanded, the distance between the outer diameter of the expansion tube 4 and the original casing inner diameter is 2.5 mm to 4.5 mm; after the expansion tube 4 is expanded, the expansion ratio of the expansion tube 4 is 7% to 20%; the tool parameters of the expansion tube 4 include the outer diameter of the expansion cone and the inner diameter of the expansion cavity;

[0068] Taking the original well casing with an outer diameter * wall thickness of 139.7mm * 7.72mm as an example, the inner diameter of the original casing is 124.26mm. In order to ensure the pressure bearing strength, the expansion tube with the size before expansion of: outer diameter * wall thickness of 108mm * 6mm can be selected. According to the aforementioned expansion ratio and the gap range between the two layers of casing after expansion, an expansion cone with an outer diameter of 106mm is used, the outer diameter after expansion is 118mm, the expansion ratio is 10.4%, the gap between the expansion tube 4 and the casing is 3.13mm, the high temperature and high pressure vulcanized sealing rubber ring 5 outside the expansion tube 4 is 4.0mm thick, and the compression ratio after expansion is 21.7%;

[0069] S3: Pull out the original well pipe string and pre-treat the original wellbore, specifically:

[0070] Clean the debris on the inner wall of the original wellbore; put a scraper into the original wellbore, scrape the original wellbore and circulate the well to clean the adhesion and scale on the well wall;

[0071] After the debris on the inner wall of the original wellbore is cleaned, the inside of the original wellbore is circulated and washed to wash out the residues inside the wellbore; a tool oil pipe 201 is used to run the well to the bottom of the artificial well and circulate and wash the well to wash out the sand and other residues in the well; the tool oil pipe 201 can be optionally of various sizes, which are selectively determined by the inner diameter of the casing, and can also be replaced by other common operating tools in the oil and gas industry such as drill pipes.

[0072] After washing out the residue inside the original wellbore, the original casing in the original wellbore is tested for leaks;

[0073] See also Figure 2 Before checking the original casing in the original wellbore for leaks, the tool tubing 201 can be pressure tested first. The connected tool tubings 201 are lowered into the original wellbore. The bottom of the tool tubing 201 string is equipped with a ball seat. The original wellbore is filled with clean water. After the ball seat is sealed, the tool tubing 201 at the wellhead of the original well is connected to the pressure-testing equipment. Pressure is applied to the tool tubing 201. The pressure is stabilized for a certain period of time, and the pressure drop is recorded to verify the pressure bearing capacity and sealing of the tool tubing 201. The pressure-testing equipment can be cement trucks, electric pressure-testing pumps, and other equipment that can generate water power and maintain stable pressure.

[0074] After the tool tubing 201 is pressure tested, the tool tubing 201 with the packer is lowered into the original wellbore, and the original wellbore is filled with clean water;

[0075] The packer 2 lowered into the original wellbore is set at 2m to 5m above the upper end of the perforation section, and the wellhead of the original well is connected to the pressure-injection equipment to pressurize the casing annulus. The pressure is stabilized according to the target time, and the pressure drop is recorded to verify the sealing of the original casing above the perforation section.

[0076] After the sealing verification of the original casing at the upper part of the perforation section is completed, the packer 2 lowered into the wellbore of the original well is set at 2m to 5m below the lower end of the perforation section, and the wellhead of the original well is connected to the pressure-injection equipment to pressurize the oil pipe, and the pressure is stabilized according to the target time, and the pressure drop is recorded to verify the sealing of the original casing at the lower part of the perforation section;

[0077] During the above-mentioned sealing verification process, according to the casing pressure bearing capacity and the downward return development pressure level, the pressure range is preferably 25MPa to 60MPa; and the pressure stabilization time is preferably 10min to 30min.

[0078] After the leak test is qualified, the supplementary section of the perforation section inside the original wellbore is milled to complete the pretreatment of the original wellbore; a milling cone can be used for milling, and the outer diameter of the milling cone is 3mm to 5mm smaller than the inner diameter of the original casing in the original wellbore; the milling cone is connected to a straight screw, and the straight screw is connected to the tool tubing 1, the tool tubing 1 is filled with clean water, and the wellhead is connected to a pressure device. After starting, the screw is caused to rotate, driving the end face of the milling cone connected to the lower part to mill the casing wall; the milling cone milling section is within 15m of the upper and lower ends of the perforation section.

[0079] S4: According to the parameters of the expansion tube 4, the expansion tube 4 is lowered into the pre-treated original wellbore to the perforation section, and the expansion operation is performed, and the perforation section is sealed. Figure 3, suspend the tool tubing 1 at the wellhead, connect a positioning nipple 3, then connect the remaining tool tubing 1, and finally connect the expansion pipe 4. Among them, a number of high-temperature and high-pressure vulcanized sealing rubber rings 5 are respectively arranged at both ends of the expansion pipe 4. Preferably, there are three groups of high-temperature and high-pressure vulcanized sealing rubber rings 5 at each end, two high-temperature and high-pressure vulcanized sealing rubber rings 5 in each group, and the width of each high-temperature and high-pressure vulcanized sealing rubber ring 5 is 10 mm - 15 mm, and the compression ratio is 20% - 25%. When performing the expansion operation on the expansion pipe 4 assembly, the high-temperature and high-pressure vulcanized sealing rubber rings 5 are respectively arranged at both ends of the perforation section, and the distance between the high-temperature and high-pressure vulcanized sealing rubber ring 5 closest to the end of the perforation section and the end of the perforation section > 1.3 m. Specifically:

[0080] Connect the tool tubing 1 to the simulated wellbore cleaning pipe; the outer diameter of the simulated wellbore cleaning pipe ≥ the outer diameter of the expansion pipe 4, and the length of the simulated wellbore cleaning pipe ≥ the length of the expansion pipe 4;

[0081] Lower the connected simulated wellbore cleaning pipe into the wellbore to the lowest well section position of the perforation section for simulated wellbore cleaning;

[0082] After the simulated wellbore cleaning is completed, connect the tool tubing 1 to the expansion pipe 4 and lower it into the original wellbore; when lowering it into the original wellbore, every 30 - 50 joints of the tool tubing 1 are filled with clear water until the expansion pipe 4 is lowered near the perforation section;

[0083] See Figure 4 and Figure 5 , after the expansion pipe 4 is lowered near the perforation section, depth correction is performed on the expansion pipe 4; preferably, the depth correction method can be: lower a gamma logging tool from the tool tubing 1, and use the gamma logging tool to test the formation gamma curve downward from the wellhead to the section of the expansion pipe 4 to obtain a new tested gamma curve; obtain the original well gamma curve, compare the new tested gamma curve with the original well gamma curve, and correct the actual well depth at the positioning nipple; calculate the distance between the current well depth position of the expansion pipe 4 and the target position according to the corrected actual well depth at the positioning nipple to complete the depth correction; or according to the depth of the perforation section in the original wellbore, set a drillable bridge plug 6 at a position 10 m - 15 m below the perforation section, and accurately record the distance between the bridge plug surface and a certain point of the perforation section; use the tool tubing 1 to lower the expansion pipe 4 into the original wellbore until it encounters resistance at the bridge plug 6 surface; lift the pipe string, and the lifting distance is based on the recorded distance between the bridge plug surface and a certain point of the perforation section to ensure that the final perforation section is located in the middle of the expansion pipe 4 to complete the depth correction.

[0084] According to the depth correction result, continue to lower the tool tubing 1 until the perforation section is located in the middle section of the expansion pipe 4;

[0085] The expansion operation is performed to make the expansion tube 4 close to the inner wall of the original casing of the original wellbore, and the perforation section is sealed. Specifically, the original wellhead tool tubing 1 is connected to the pressure device, and the pressure is continuously and steadily increased to the expansion starting pressure. The expansion cone moves upward and passes through the upper bell mouth. The expansion cone is released, and the expansion is completed. The expansion cone is pulled out, and a fishing spear is lowered to 1m above the bottom plug of the expansion tube 4. The original wellhead tubing is connected to the pressure device, and the bottom plug is circulated and flushed for 30min to 60min; the fishing spear is re-lowered until it enters the bottom plug. After judging that the salvage is successful according to the change in the hanging weight of the tubing, the bottom plug is pulled out, and the drillable bridge plug 6 is used for positioning as described above. After the expansion of the expansion tube 4 is completed, the bottom plug is salvaged, and then a milling tool is lowered to mill the drillable bridge plug 6.

[0086] S5: After the plugging is completed, the bottom plug of the expansion tube 4 is removed to form a new wellbore channel;

[0087] S6: Verify the sealing and passability of the new wellbore channel to complete the reconstruction of the complete wellbore, specifically: fill the new wellbore with clean water, connect the wellhead to the pressure equipment, and conduct a full wellbore pressure test according to the needs of the return development. Stabilize the pressure for a certain period of time, record the pressure drop, and verify the sealing of the reshaped wellbore. The pressure test range is preferably 25MPa~60MPa, and the pressure stabilization time is preferably 10min~30min. Finally, use the tool oil pipe 1 to lower the wellbore gauge so that the wellbore gauge completely passes through the expansion pipe 4 well section to complete the passability verification and complete the reconstruction of the complete wellbore of the measure well. The outer diameter of the wellbore gauge is 4mm~6mm smaller than the inner diameter of the expansion pipe 4 after expansion.

[0088] In summary, the present invention provides a method for reshaping a complete wellbore during the downhole development of unconventional natural gas. The method creatively achieves the plugging of the perforation section in the wellbore of the original well to be developed by controlling the expansion tube 4. The method is simple and easy to operate, has strong safety, can withstand a pressure of more than 50 MPa, provides a basis for subsequent downhole development, and has low transformation cost and good economic benefits.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A method for reshaping a complete wellbore during the development of unconventional natural gas wells. It is characterized in that The following steps are involved: Obtain the original well basic information and wellbore conditions; Determine the parameters of each component of the expansion pipe according to the original well basic information and wellbore working conditions; Pull out the original well pipe string and pre-treat the original wellbore; According to the parameters of each component of the expansion tube, the expansion tube is lowered into the pre-treated original wellbore to the perforation section, and the expansion operation is performed, and the perforation section is sealed; After plugging is completed, the bottom plug of the expansion pipe is removed to form a new wellbore channel; Verify the sealing and passability of the new wellbore channel to complete the reconstruction of the entire wellbore.

2. The method for realizing complete wellbore reconstruction during unconventional natural gas downhole recovery according to claim 1, It is characterized in that The basic information of the original well includes the original casing inner diameter, perforation section length, perforation section position and pressure bearing information of the original well to be developed.

3. The method for realizing the complete wellbore reconstruction during the downhole recovery of unconventional natural gas according to claim 1, It is characterized in that According to the original well basic information and wellbore working conditions, the method for determining the parameters of each component of the expansion tube assembly is as follows: Obtain the pressure bearing information of the original well, and select the material and wall thickness of the expansion pipe according to the pressure bearing information of the original well, so that the pressure bearing strength of the expansion pipe is greater than the maximum pressure bearing in the pressure bearing information of the original well; Obtain the perforation section length of the original well, and determine the length of the expansion tube according to the perforation section length, so that (expansion tube length - perforation section length) ≥ 2.6m; The original casing inner diameter of the original well is obtained, and the outer diameter of the expansion tube and the tool parameters of the expansion tube are determined according to the original casing inner diameter, so that the diameter of the expansion tube tool is smaller than the casing inner diameter, so that after the expansion tube is expanded, the distance between the outer diameter of the expansion tube and the original casing inner diameter is 2.5mm to 4.5mm.

4. The method for realizing the complete wellbore reconstruction during the downhole recovery of unconventional natural gas according to claim 1, It is characterized in that The method for pre-treating the original wellbore is: Clean the debris on the inner wall of the original wellbore; After the debris on the inner wall of the original wellbore is cleaned, the inside of the original wellbore is circulated and washed to wash out the residue inside the wellbore; After washing out the residue inside the original wellbore, the original casing in the original wellbore is tested for leaks; After the leak test is qualified, the supplementary section of the perforated section inside the original wellbore is milled to complete the pretreatment of the original wellbore.

5. The method for realizing complete wellbore reconstruction during downhole recovery of unconventional natural gas according to claim 4, It is characterized in that The method for leak detection of the original casing in the original wellbore is: Lower the tool tubing with the packer into the original wellbore, and fill the original wellbore with clean water; The packer lowered into the original wellbore is seated on the perforated section, and the wellhead of the original well is connected to the pressure-injection equipment to pressurize the casing annulus. The pressure is stabilized according to the target time, and the pressure drop is recorded to verify the sealing of the original casing above the perforated section. After the sealing verification of the original casing at the upper part of the perforation section is completed, the packer lowered into the wellbore of the original well is seated at the lower end of the perforation section, and the wellhead of the original well is connected to the pressure-injection equipment to pressurize the tubing, stabilize the pressure according to the target time, record the pressure drop, and verify the sealing of the original casing at the lower part of the perforation section.

6. The method for realizing complete wellbore reconstruction during downhole recovery of unconventional natural gas according to claim 5, It is characterized in that When the packer lowered into the original wellbore is seated at the upper end of the perforation section, the packer is 2m to 5m away from the upper end of the perforation section; when the packer lowered into the original wellbore is seated at the lower end of the perforation section, the packer is 2m to 5m away from the lower end of the perforation section.

7. The method for realizing complete wellbore reconstruction during downhole recovery of unconventional natural gas according to claim 1, It is characterized in that The expansion pipe is lowered into the pre-treated original wellbore to the perforation section, and the expansion operation is performed. The method for plugging the perforation position is as follows: Connect the tool oil pipe to the simulated wellbore pipe; the outer diameter of the simulated wellbore pipe is greater than or equal to the outer diameter of the expansion pipe, and the length of the simulated wellbore pipe is greater than or equal to the length of the expansion pipe; The connected simulated well-draining pipe is lowered into the wellbore to the bottom of the perforation section to simulate well-draining; After the simulated well cleaning is completed, the tool tubing is connected to the expansion tube and lowered into the original wellbore; When lowering into the original wellbore, fill the tool tubing with clean water every 30 to 50 sections of tool tubing until the expansion tube is lowered to the vicinity of the perforation section; After the expansion pipe is lowered to the vicinity of the perforation section, the depth of the expansion pipe is calibrated; According to the depth calibration result, continue to run the tool tubing until the perforation section is located in the middle section of the expansion tube; The expansion operation is carried out to make the expansion tube close to the inner wall of the original casing of the original wellbore to complete the plugging of the perforation section.

8. The method for realizing complete wellbore reconstruction during downhole recovery of unconventional natural gas according to claim 7, It is characterized in that The method for calibrating the depth of the expansion tube is: A gamma logging instrument is lowered into the tool tubing, and the gamma logging instrument is used to test the formation gamma curve from the wellhead downward to the expansion pipe section to obtain a new test gamma curve; Obtain the original well gamma curve, compare the new test gamma curve with the original well gamma curve, and correct the actual well depth at the positioning short joint; According to the actual well depth at the calibration positioning nipple, the distance between the current well depth position of the expansion pipe and the target position is calculated to complete the depth calibration; or According to the depth of the perforated section in the original wellbore, a drillable bridge plug is placed at a position 10m to 15m below the perforated section, and the distance between the bridge plug surface and a certain point in the perforated section is accurately recorded; Use the tool tubing to lower the expansion pipe into the original wellbore until the drillable bridge plug surface encounters resistance; Lift the pipe string. The lifting distance shall be based on the recorded distance between the bridge plug surface and a certain point in the perforation section. Ensure that the final perforation section is located in the middle of the expansion pipe and complete the depth calibration.

9. The method for realizing complete wellbore reconstruction during downhole recovery of unconventional natural gas according to any one of claims 1 to 8, It is characterized in that A plurality of high-temperature and high-pressure vulcanized sealing rubber rings are respectively arranged at both ends of the expansion tube in the expansion tube assembly.

10. The method for realizing complete wellbore reconstruction during downhole redevelopment of unconventional natural gas according to claim 9, It is characterized in that When the expansion tube assembly is expanded, the high-temperature and high-pressure vulcanized sealing rubber rings are arranged at both ends of the perforation section, and the distance between the high-temperature and high-pressure vulcanized sealing rubber ring closest to the end of the perforation section and the end of the perforation section is greater than 1.3m.

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