Well wall packing device and shaft strengthening method

Abstract

The invention relates to the technical field of well drilling, and discloses a well wall packing device and a shaft strengthening method. The well wall packing device comprises a feeding pipe column (1) and an expansion pipe (2). A plurality of dangling keys (11) are arranged on the outer wall of the feeding pipe column (1); the expansion pipe (2) comprises a notch end and a threaded end, and a J-shaped groove (21) matched with the dangling key (11) is formed in the inner wall of the notch end; the feeding pipe column (1) and the expansion pipe (2) are connected in a hooked mode through the dangling key (11) and the J-shaped groove (21). According to the well wall packing device provided by the invention, the construction difficulty of connection and feeding of the expansion pipe can be reduced, and the construction reliability is improved. A well wall packing device and chemical plugging slurry plugging are combined, unmeasurable malignant fractured leakage can be converted into controllable permeability leakage of an expansion pipe, the leakage problem can be well solved, the well wall strength can be enhanced, and the collapse treatment efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling, and in particular to a well wall isolation device and a wellbore strengthening method. Background Art

[0002] During the drilling process, wellbore leakage and collapse are the main causes of complex downhole faults, long drilling cycles, and high drilling costs. Downhole fractured formations are characterized by large fracture scales, a wide range of fracture widths, and complex fracture morphology. Currently, there is no suitable measurement method to obtain real formation fracture data. Moreover, the cracks in downhole fractured formations are pressure-sensitive and stress-sensitive, and will undergo dynamic deformation as the wellbore fluid column pressure and construction conditions change. Therefore, it is extremely difficult to plug leaks in downhole fractured formations, and it is difficult for technicians to prepare a thick slurry plugging fluid that is specifically matched to the cracks. The effect of plugging with a thick slurry plugging fluid alone is not ideal.

[0003] Expandable tubular technology is a new technology in the field of drilling engineering. During the drilling process, the expandable tubular is lowered into a predetermined position underground, and the expansion cone is used to use mechanical force or hydraulic pressure to cause the expandable tubular entity to undergo permanent radial plastic deformation, thereby expanding the radial size of the tubular string. This technology can be used in drilling, completion, oil production and well repair operations.

[0004] This technology can fit the well wall and make up for the shortcomings of drilling fluid or chemical methods. However, this kind of expansion tube is generally made of metal, which has high requirements on the regularity of the wellbore and requires special auxiliary tools to be sent into the well. The docking and release operations of the expansion tube and the auxiliary tools are difficult, the construction period is long, and once the operation fails, the expansion tube is difficult to be drilled or milled in the well, which can easily cause the wellbore or footage to be scrapped. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art, such as unsatisfactory plugging effect of underground fractured formations and great difficulty in expansion pipe construction, and to provide a well wall isolation device and a wellbore strengthening method.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a well wall isolation device, wherein the well wall isolation device includes an entry pipe string 1 and an expansion pipe 2; wherein a plurality of hanging keys 11 are arranged on the outer wall of the entry pipe string 1; the expansion pipe 2 includes a notch end and a threaded end, and a J-shaped groove 21 matching the hanging key 11 is arranged on the inner wall of the notch end; the entry pipe string 1 and the expansion pipe 2 are hooked by the hanging key 11 and the J-shaped groove 21.

[0007] The second aspect of the present invention provides a wellbore strengthening method, wherein the method is performed using the wellbore isolation device according to the first aspect of the present invention, and comprises the following steps:

[0008] (1) hooking the expansion pipe 2 onto the delivery string 1, and lowering the expansion pipe 2 to a predetermined position in the wellbore using the delivery string 1; wherein the expansion pipe 2 is optionally connected to at least one extension pipe;

[0009] (2) Using a preset temperature to excite the expansion tube 2 and the optional extension tube to complete the expansion operation and the release operation;

[0010] (3) chemical plugging by injecting chemical plugging slurry into the delivery pipe string 1;

[0011] (4) The delivery pipe string (1) is lifted out of the wellbore.

[0012] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0013] 1) The well wall isolation device provided in the present invention has a delivery string and an expansion pipe connected by a hanging key and a J-shaped groove, which can reduce the construction difficulty of connection and delivery and improve the reliability of construction; the delivery process does not require special tools and ground pressure, and after the expansion pipe is stimulated to expand, it can naturally detach from the delivery string, which is convenient for recovering the delivery string, and the construction is simple and the reliability is high;

[0014] 2) The well wall isolation device provided in the present invention has low requirements on the regularity of the wellbore, does not require procedures such as wellbore logging, has a short construction period, and has a high degree of fit with the well wall after expansion, and has a good treatment effect;

[0015] 3) The well wall isolation device provided by the present invention has a pipe body that is easy to drill out, and even if the construction fails, the wellbore or footage will not be scrapped; the well diameter changes after construction, and the steps formed by the expansion pipe well section are easily destroyed, which will not cause complexity to the subsequent construction;

[0016] 4) The wellbore strengthening method provided in the present invention can transform unpredictable malignant fracture leakage into controllable permeability leakage of the expansion pipe by combining expansion pipe well wall isolation and chemical plugging slurry plugging, which can effectively solve the leakage problem, strengthen the well wall strength, improve the efficiency of collapse control, and significantly shorten the drilling cycle and reduce drilling investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a delivery column in a preferred embodiment of the present invention;

[0018] Figure 2 is a schematic structural diagram of an expansion tube in a preferred embodiment of the present invention;

[0019] Figure 3 It is a perspective schematic diagram of the hook connection between the delivery string and the expansion pipe in a preferred embodiment of the present invention;

[0020] Figure 4 It is a schematic cross-sectional structure diagram of a delivery string and an expansion tube in a preferred embodiment of the present invention.

[0021] Description of Reference Numerals

[0022] 1, delivery string 11, hanging key 2, expansion tube

[0023] 21. J-shaped slot DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] A first aspect of the present invention provides a well wall isolation device, wherein the well wall isolation device comprises a delivery string 1 and an expansion pipe 2; wherein a plurality of hanging keys 11 are arranged on the outer wall of the delivery string 1; the expansion pipe 2 comprises a notch end and a threaded end, and a J-shaped groove 21 matching the hanging key 11 is arranged on the inner wall of the notch end; the delivery string 1 and the expansion pipe 2 are hooked together by the hanging key 11 and the J-shaped groove 21, such as Figure 1-4 shown.

[0026] In one embodiment of the present invention, the delivery string 1 comprises an upper pipe end and a lower pipe end, and the hanging key 11 is arranged on the outer wall of the lower pipe end. In the present invention, the end of the delivery string hooked with the expansion pipe is the lower pipe end, and the end opposite to the lower end is the upper pipe end.

[0027] In one embodiment of the present invention, the hanging keys 11 are evenly distributed on the outer wall of the lower pipe end. In the present invention, the lower surfaces of the plurality of hanging keys are located on the same radial horizontal plane of the delivery column, and the plurality of hanging keys are evenly distributed along the circumferential direction.

[0028] In one embodiment of the present invention, the distance h between the suspension key 11 and the bottom of the lower tube end is 1-8 cm, preferably 2-4 cm.

[0029] In the present invention, the distance h between the hanging key and the bottom of the lower pipe end of the delivery string refers to the vertical distance from the lower surface of the hanging key to the bottom of the delivery string. The height of the hanging key can ensure the strength of the hanging key while facilitating the hooking between the delivery string and the expansion pipe.

[0030] In one embodiment of the present invention, the number of the suspension keys 11 is 2-8, preferably 3-4. In the present invention, the connection strength can be improved and the difficulty of hooking operation can be reduced by adjusting the number of suspension keys. When the number of suspension keys is 3-4, the installation and hooking effect is best.

[0031] In one embodiment of the present invention, the J-shaped groove 21 includes a first vertical groove, a transverse groove and a second vertical groove, wherein the first vertical groove and the second vertical groove are connected by the transverse groove.

[0032] The J-shaped groove enhances the reliability of the hook connection between the delivery string and the expansion tube. In the present invention, the hanging key can first enter the expansion tube along the first vertical groove, and then rotate toward the horizontal groove after reaching the bottom of the first vertical groove, and move along the horizontal groove until reaching the end of the horizontal groove, and then enter the second vertical groove, and the hanging key is stuck in the second vertical groove, so that the expansion tube is hung on the delivery string, and the delivery string and the expansion tube are hooked.

[0033] In one embodiment of the present invention, the thickness of the suspension key 11 is 50-90% of the depth of the J-shaped groove 21, preferably 60-80%.

[0034] Among them, in the present invention, in order to ensure that the suspension key can smoothly enter the J-shaped groove and reduce the installation difficulty during hook connection as much as possible, the thickness of the suspension key should be smaller than the depth of the J-shaped groove. In order to ensure the connection strength between the delivery pipe string and the expansion pipe, the suspension key should not be too thin. When the thickness of the suspension key is 60-80% of the depth of the J-shaped groove, the connection effect is best.

[0035] In one embodiment of the present invention, the material of the expansion tube 2 is selected from a porous shape memory material with temperature-sensitive properties, preferably a hard polyurethane foam material.

[0036] Among them, in the present invention, the expansion tube made of rigid polyurethane foam material is kept in a compressed state before being lowered into the well. After reaching the predetermined position in the well, the inner diameter and outer diameter can be expanded synchronously under the stimulation of the formation temperature or the injected stimulation fluid, and the inner diameter is restored to the size of the expansion tube before compression, and the outer wall is close to the well wall. The expansion of the expansion tube will cause the notch of the J-shaped groove to become larger, so that the hanging key on the delivery pipe string can be easily detached from the J-shaped groove, thereby completing the release.

[0037] In one embodiment of the present invention, the expansion temperature of the rigid polyurethane foam material is 40-90°C, preferably 60-80°C; the expansion amount is 50-350%, preferably 80-120%; the porosity after expansion is 30-50%, preferably 35-40%; the permeability is 150-300md, preferably 160-200md.

[0038] The rigid polyurethane foam material of the present invention can be a commercially available material or can be synthesized according to a public method. For example, a polymer synthesized by using ε-caprolactone as a monomer and at least one of glycerol, trimethylolpropane, ethylene glycol, diethylene glycol, butanediol, neopentyl glycol and hexanediol as an initiator is a polyol, and water and dichloromethane are used as foaming agents for synthesis. The foam material is obtained by changing the composition material system and content or optimizing the high-temperature foaming system and method, controlling the material glass transition temperature, recovery temperature and foaming hole diameter, and then the foam material is subjected to high-temperature heating to soften and compression to shape, so as to obtain the rigid polyurethane foam material that meets the definition of the present invention.

[0039] In one embodiment of the present invention, the inner wall of the threaded end of the expansion tube 2 is optionally provided with threads. In the present invention, the threaded end is only used for naming, and does not mean that the port must be provided with threads.

[0040] In one embodiment of the present invention, the well wall isolation device further comprises at least one extension pipe; wherein the extension pipe is a connecting pipe of the expansion pipe 2 and is used to extend the length of the expansion pipe 2 .

[0041] In the present invention, the length of the expansion pipe is limited by the preparation method and is unlikely to exceed 2 m. If the length of the well section to be reinforced is greater than 2 m, an extension pipe can be connected to the expansion pipe to extend the length of the expansion pipe.

[0042] In one embodiment of the present invention, the extension pipe is connected to the expansion pipe 2 via a trapezoidal thread, and the extension pipes are also connected to each other via a trapezoidal thread.

[0043] Among them, in the present invention, when the well wall isolation device also includes an extension pipe, the threaded end of the expansion pipe is provided with a trapezoidal threaded female buckle, and the extension pipe is correspondingly provided with a trapezoidal threaded male buckle. The expansion pipe and the extension pipe are connected by threads. When the well wall isolation device also includes more than two extension pipes, the extension pipes are also connected in series by the trapezoidal threaded female buckle and the trapezoidal threaded male buckle.

[0044] In one embodiment of the present invention, the pitch of the trapezoidal thread box is 6-8 mm. In the present invention, by controlling the pitch of the trapezoidal thread box, the strength of the threaded connection in the present invention can be improved and the probability of construction failure can be reduced as much as possible.

[0045] The second aspect of the present invention provides a wellbore strengthening method, wherein the method is performed using the wellbore isolation device according to the first aspect of the present invention, and comprises the following steps:

[0046] (1) hooking the expansion pipe 2 onto the delivery string 1, and lowering the expansion pipe 2 to a predetermined position in the wellbore using the delivery string 1; wherein the expansion pipe 2 is optionally connected to at least one extension pipe;

[0047] (2) Using a preset temperature to excite the expansion tube 2 and the optional extension tube to complete the expansion operation and the release operation;

[0048] (3) chemical plugging by injecting chemical plugging slurry into the delivery pipe string 1;

[0049] (4) The delivery pipe string 1 is lifted out of the wellbore.

[0050] Among them, in the present invention, since the specific size of the underground crack cannot be clearly determined, it is difficult to obtain an ideal plugging effect by using chemical plugging slurry alone to plug the well wall. Although the expansion tube made of shape memory material with temperature-sensitive characteristics is used alone to reinforce the wellbore, it can increase the strength of the well wall, prevent collapse, and solve the problem of well wall instability. However, since the shape memory material with temperature-sensitive characteristics is a porous material, the permeability increases after expansion, and it is difficult to obtain a good plugging effect for malignant leakage with a large leakage rate.

[0051] The inventors of the present invention have found through research that combining wellbore isolation with chemical plugging slurry plugging can better transform unpredictable malignant fracture leakage into controllable permeability leakage of expansion pipe, which can not only solve the leakage problem well, but also strengthen the wellbore strength, improve the efficiency of collapse control, significantly shorten the drilling cycle and reduce drilling investment.

[0052] In one embodiment of the present invention, the extension pipe is first connected to the expansion pipe 2 by threading, and then the expansion pipe 2 is hooked to the delivery string 1, and the expansion pipe 2 is lowered to a predetermined position in the wellbore by the delivery string 1. In the present invention, whether the extension pipe needs to be connected and the number of the extension pipes to be connected can be confirmed according to the actual well conditions.

[0053] In one embodiment of the present invention, the hooking method of the delivery string 1 and the expansion tube 2 is as follows: the hanging key on the delivery string 1 first enters the expansion tube 2 along the first vertical groove, and after reaching the bottom of the first vertical groove, it rotates toward the horizontal groove direction and enters the horizontal groove. After reaching the end of the horizontal groove, it enters the second vertical groove, and then the hanging key is stuck in the second vertical groove, so that the expansion tube 2 is hung on the delivery string 1, thereby realizing the hooking of the delivery string 1 and the expansion tube 2.

[0054] In one embodiment of the present invention, the expansion operation and the release operation include: after reaching the predetermined position, the inner diameter and the outer diameter of the expansion tube 2 and the optional extension tube are synchronously expanded under the stimulation of the formation temperature or the injected stimulation fluid, until the outer wall of the expansion tube 2 and the optional extension tube is close to the well wall, and the inner diameter is restored to the size before compression; after the expansion tube 2 and the optional extension tube complete the expansion, the hanging key is pulled out from the J-shaped groove, thereby completing the release operation.

[0055] In one embodiment of the present invention, the raw materials for preparing the chemical plugging slurry include: 100 parts by weight of base slurry, 2-10 parts by weight of well wall strengthener, 5-15 parts by weight of rigid plugging agent, 5-20 parts by weight of elastic plugging agent and 1-5 parts by weight of flexible plugging agent.

[0056] Among them, in the present invention, based on the seepage characteristic measurement results of the porosity and permeability after the expansion tube is expanded, the chemical plugging slurry can be accurately prepared, thereby converting the unpredictable malignant fracture leakage into the controllable permeability leakage of the expansion tube, solving the problem of poor plugging effect caused by the mismatch between the chemical plugging slurry and the underground fractures.

[0057] In one embodiment of the present invention, the raw materials for preparing the chemical plugging slurry include: 100 parts by weight of base slurry, 4-6 parts by weight of well wall strengthener, 8-12 parts by weight of rigid plugging agent, 10-15 parts by weight of elastic plugging agent and 2.5-3.5 parts by weight of flexible plugging agent.

[0058] In one embodiment of the present invention, the base slurry is an aqueous solution containing sodium bentonite and sodium carbonate. The present invention does not specifically limit the base slurry, and the base slurry can be selected according to conventional operations in the art.

[0059] In one embodiment of the present invention, the well wall strengthener is selected from asphalt well wall strengtheners and / or gel well wall strengtheners. The asphalt well wall strengthener can be asphalt copolymer HQ-1 and / or sulfonated asphalt powder, and the gel well wall strengthener can be PAM gel and / or PMN gel.

[0060] In one embodiment of the present invention, the rigid plugging agent is selected from one or more of calcium carbonate, mica flakes, calcite, and limestone.

[0061] In one embodiment of the present invention, the elastic plugging agent is selected from one or more of elastic rubber particles, elastic graphite, and elastic sponge particles.

[0062] In one embodiment of the present invention, the flexible plugging agent is selected from a fiber material, and the fiber material is selected from one or more of plant fibers, polymer fibers, and inorganic fibers.

[0063] Among them, the plant fiber is selected from one or more of sawdust, rice husk, wheat straw, buckwheat husk, and straw; the polymer fiber is selected from polypropylene fiber and / or polyester fiber; the inorganic fiber is selected from one or more of asbestos fiber, wollastonite fiber, and basalt fiber.

[0064] In the present invention, after the wellbore strengthening is completed, the drilling tool assembly can be replaced and the original size drill bit can be used to sweep the plug to form the original diameter and drill normally. When leakage or collapse occurs again during the drilling process, the method of the present invention can be used again to repeat the wellbore strengthening.

[0065] In one embodiment of the present invention, the chemical plugging slurry may further include some common additives in the art, such as weighting agents, defoaming agents, lubricants, dispersants, viscosity enhancers, viscosity reducers, and the like.

[0066] The present invention is described in detail below by way of examples and comparative examples.

[0067] The well wall isolation device used in the embodiment includes a delivery pipe string and an expansion pipe. Among them, 4 hanging keys are evenly arranged on the outer wall of the lower pipe end of the delivery pipe string, and the distance h between the hanging key and the bottom of the lower pipe end is 2 cm, and the thickness of the hanging key is 14 mm. The expansion pipe is 50 cm long, the inner diameter before expansion is 6 cm, and the wall thickness is 30 mm. The expansion pipe includes a notched end and a threaded end. A J-shaped groove matching the hanging key is arranged on the inner wall of the notched end; the groove depth of the J-shaped groove is 18 mm.

[0068] The expansion tube is made of hard polyurethane foam material purchased from Sinopec Petroleum Engineering Technology Research Institute Co., Ltd. The expansion amount at 75°C is 80%, the porosity after expansion is 35%, and the permeability is 160md.

[0069] Simulated wellbore: a metal cylinder with a length of 150 cm, an inner diameter of 16 cm, and a wall thickness of 15 mm. A loss section is provided at the lower end of the metal cylinder. The loss section is 20 cm long. A plurality of small holes with an aperture range of 2-10 mm are provided on the cylinder wall of the loss section. The loss section is used to simulate the ground fractures in the wellbore.

[0070] The base slurry includes water, sodium bentonite and sodium carbonate, wherein the mass ratio of water, sodium bentonite and sodium carbonate is 95:5:0.25g.

[0071] Plugging verification method: According to the indoor test method of bridging plugging materials for drilling fluids SY / T5840-2007, the maximum bearing pressure of the simulated wellbore after plugging is tested at room temperature. The greater the maximum bearing pressure, the better the plugging effect.

[0072] Example 1

[0073] 1) Connect the delivery string and the expansion pipe together through the hanging key and the J-shaped slot hook, and use the delivery string to lower the expansion pipe to the lost circulation section of the simulated test wellbore;

[0074] 2) The simulated test wellbore is heated to 75°C, and the expansion tube expands at 75°C, so that the outer wall of the expansion tube is close to the wellbore wall; after the expansion tube is fully expanded, the hanging key is pulled out from the J-shaped groove to complete the release operation;

[0075] 3) Chemical plugging is performed by injecting chemical plugging slurry into the delivery column; wherein the chemical plugging slurry comprises: base slurry, asphalt copolymer HQ-1, calcium carbonate, calcite, elastic graphite, basalt fiber and polypropylene fiber, and the mass ratio of the base slurry, asphalt copolymer HQ-1, calcium carbonate, calcite, elastic graphite, basalt fiber and polypropylene fiber is 100:4:6:6:10:1:1.5;

[0076] 4) The delivery string is lifted out of the wellbore to recover the delivery string.

[0077] A pressure test was carried out on the simulated wellbore at room temperature, and the maximum pressure was 15.0MPa.

[0078] Example 2

[0079] 1) Connect the delivery string and the expansion pipe together through the hanging key and the J-shaped slot hook, and use the delivery string to lower the expansion pipe to the lost circulation section of the simulated test wellbore;

[0080] 2) The simulated test wellbore is heated to 75°C, and the expansion tube expands at 75°C, so that the outer wall of the expansion tube is close to the wellbore wall; after the expansion tube is fully expanded, the hanging key is pulled out from the J-shaped groove to complete the release operation;

[0081] 3) chemical plugging is performed by injecting chemical plugging slurry into the delivery column; wherein the chemical plugging slurry comprises: base slurry, asphalt copolymer HQ-1, mica flakes, calcite, elastic rubber particles, sawdust and basalt fiber, wherein the mass ratio of base slurry, asphalt copolymer HQ-1, mica flakes, calcite, elastic rubber particles, sawdust and basalt fiber is 100:6:5:3:15:2:1.5;

[0082] 4) The delivery string is lifted out of the wellbore to recover the delivery string.

[0083] The pressure test was carried out on the simulated wellbore at normal temperature, and the maximum pressure bearing capacity was 14.3MPa.

[0084] Example 3

[0085] 1) Connect the delivery string and the expansion pipe together through the hanging key and the J-shaped slot hook, and use the delivery string to lower the expansion pipe to the lost circulation section of the simulated test wellbore;

[0086] 2) The simulated test wellbore is heated to 75°C, and the expansion tube expands at 75°C, so that the outer wall of the expansion tube is close to the wellbore wall; after the expansion tube is fully expanded, the hanging key is pulled out from the J-shaped groove to complete the release operation;

[0087] 3) chemical plugging is performed by injecting chemical plugging slurry into the delivery column; wherein the chemical plugging slurry comprises base slurry, sulfonated asphalt powder, calcite, elastic sponge particles and wollastonite fibers, and the mass ratio of the base slurry, sulfonated asphalt powder, calcite, elastic sponge particles and wollastonite fibers is 100:2:15:5:2;

[0088] 4) The delivery string is lifted out of the wellbore to recover the delivery string.

[0089] The simulated wellbore was tested for pressure at room temperature, and the maximum pressure capacity was 12.5MPa.

[0090] Example 4

[0091] 1) Connect the delivery string and the expansion pipe together through the hanging key and the J-shaped slot hook, and use the delivery string to lower the expansion pipe to the lost circulation section of the simulated test wellbore;

[0092] 2) The simulated test wellbore is heated to 75°C, and the expansion tube expands at 75°C, so that the outer wall of the expansion tube is close to the wellbore wall; after the expansion tube is fully expanded, the hanging key is pulled out from the J-shaped groove to complete the release operation;

[0093] 3) chemical plugging is performed by injecting chemical plugging slurry into the delivery column; wherein the chemical plugging slurry comprises: base slurry, sulfonated asphalt powder, calcium carbonate, elastic rubber particles and wheat straw, wherein the mass ratio of the base slurry, sulfonated asphalt powder, calcium carbonate, elastic rubber particles and wheat straw is 100:8:5:20:4;

[0094] 4) The delivery string is lifted out of the wellbore to recover the delivery string.

[0095] The pressure test was carried out on the simulated wellbore at normal temperature, and the maximum pressure bearing capacity was 11.6MPa.

[0096] Comparative Example 1

[0097] 1) Connect the delivery string and the expansion pipe together through the hanging key and the J-shaped slot hook, and use the delivery string to lower the expansion pipe to the lost circulation section of the simulated test wellbore;

[0098] 2) The simulated test wellbore is heated to 75°C, and the expansion tube expands at 75°C, so that the outer wall of the expansion tube is close to the wellbore wall; after the expansion tube is fully expanded, the hanging key is pulled out from the J-shaped groove to complete the release operation;

[0099] 3) chemical plugging is performed by injecting chemical plugging slurry into the delivery column; wherein the chemical plugging slurry comprises: base slurry, sulfonated asphalt powder and elastic rubber particles, wherein the mass ratio of the base slurry, the sulfonated asphalt powder and the elastic rubber particles is 100:8:20;

[0100] 4) The delivery string is lifted out of the wellbore to recover the delivery string.

[0101] A pressure test was conducted on a simulated wellbore at normal temperature, and the maximum pressure capacity was 5.7MPa.

[0102] Comparative Example 2

[0103] 1) Connect the delivery string and the expansion pipe together through the hanging key and the J-shaped slot hook, and use the delivery string to lower the expansion pipe to the lost circulation section of the simulated test wellbore;

[0104] 2) The simulated test wellbore is heated to 75°C, and the expansion tube expands at 75°C, so that the outer wall of the expansion tube is close to the wellbore wall; after the expansion tube is fully expanded, the hanging key is pulled out from the J-shaped groove to complete the release operation;

[0105] 3) chemical plugging is performed by injecting chemical plugging slurry into the delivery column; wherein the chemical plugging slurry comprises: base slurry, sulfonated asphalt powder, calcium carbonate, elastic rubber particles and wheat straw, wherein the mass ratio of the base slurry, sulfonated asphalt powder, calcium carbonate, elastic rubber particles and wheat straw is 100:15:5:20:4;

[0106] 4) The delivery string is lifted out of the wellbore to recover the delivery string.

[0107] The pressure test was carried out on the simulated wellbore at normal temperature, and the maximum pressure bearing capacity was 8.9MPa.

[0108] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A well wall isolation device, characterized in that: The wellbore isolation device comprises a delivery string (1) and an expansion tube (2); wherein a plurality of hanging keys (11) are arranged on the outer wall of the delivery string (1); the expansion tube (2) comprises a notched end and a threaded end, and a J-shaped groove (21) matching the hanging key (11) is arranged on the inner wall of the notched end; the delivery string (1) and the expansion tube (2) are hooked together via the hanging key (11) and the J-shaped groove (21).

2. The well wall isolation device according to claim 1, wherein: The delivery pipe column (1) comprises an upper pipe end and a lower pipe end, and the suspension key (11) is arranged on the outer wall of the lower pipe end; Preferably, the distance h between the suspension key (11) and the bottom of the lower tube end is 1-8 cm, preferably 2-4 cm; Preferably, the number of the hanging keys (11) is 2-8, preferably 3-4.

3. The well wall isolation device according to claim 2, wherein: The J-shaped groove (21) comprises a first vertical groove, a transverse groove and a second vertical groove, wherein the first vertical groove and the second vertical groove are connected via the transverse groove; Preferably, the thickness of the suspension key (11) is 50-90%, preferably 60-80%, of the depth of the J-shaped groove (21).

4. The well wall isolation device according to any one of claims 1 to 3, wherein: The material of the expansion tube (2) is selected from a porous shape memory material with temperature-sensitive properties, preferably a hard polyurethane foam material.

5. The well wall isolation device according to claim 4, wherein: The expansion temperature of the rigid polyurethane foam material is 40-90°C, preferably 60-80°C; the expansion amount is 50-350%, preferably 80-120%; the porosity after expansion is 30-50%, preferably 35-40%; the permeability is 150-300md, preferably 160-200md.

6. The well wall isolation device according to any one of claims 1 to 5, wherein: The well wall isolation device also includes at least one extension pipe; wherein the extension pipe is a connecting pipe of the expansion pipe (2) and is used to extend the length of the expansion pipe.

7. The well wall isolation device according to claim 6, wherein: The extension pipe is connected to the expansion pipe (2) via a trapezoidal thread, and the extension pipes are also connected to each other via a trapezoidal thread; Preferably, the female thread pitch of the trapezoidal thread is 6-8 mm.

8. A wellbore strengthening method, characterized in that: The method is carried out using the well wall isolation device according to any one of claims 1 to 7, comprising the following steps: (1) hooking an expansion pipe (2) onto a delivery string (1), and lowering the expansion pipe (2) to a predetermined position in the wellbore using the delivery string (1); wherein the expansion pipe (2) is optionally connected to at least one extension pipe; (2) using a preset temperature to excite the expansion tube (2) and the optional extension tube to complete the expansion operation and the release operation; (3) injecting chemical plugging slurry into the delivery column (1) for chemical plugging; (4) The delivery pipe string (1) is lifted out of the wellbore.

9. The wellbore strengthening method according to claim 8, wherein: The raw materials for preparing the chemical plugging slurry include: 100 parts by weight of base slurry, 2-10 parts by weight of well wall strengthening agent, 5-15 parts by weight of rigid plugging agent, 5-20 parts by weight of elastic plugging agent and 1-5 parts by weight of flexible plugging agent.

10. The wellbore strengthening method according to claim 9, wherein: The well wall strengthening agent is selected from asphalt well wall strengthening agents and / or gel well wall strengthening agents; Preferably, the rigid plugging agent is selected from one or more of calcium carbonate, mica flakes, calcite, and limestone; Preferably, the elastic plugging agent is selected from one or more of elastic rubber particles, elastic graphite, and elastic sponge particles; Preferably, the flexible plugging agent is selected from a fiber material, and the fiber material is selected from one or more of plant fibers, polymer fibers, and inorganic fibers; Among them, the plant fiber is selected from one or more of sawdust, rice husk, wheat straw, buckwheat husk, and straw; the polymer fiber is selected from polypropylene fiber and / or polyester fiber; the inorganic fiber is selected from one or more of asbestos fiber, wollastonite fiber, and basalt fiber.

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