Expansion combined casing pipe and well cementation method

Abstract

The invention discloses an expansion combined casing and a well cementation method, and belongs to the technical field of oil and gas exploitation, the expansion combined casing comprises an oil-string casing, a self-thermal expansion assembly and a flexible alloy cover body, the outer surface of the oil-string casing is sleeved with the self-thermal expansion assembly, and the self-thermal expansion assembly comprises a flexible permeable coating film and a self-thermal material filled in the coating film; the flexible alloy cover body is arranged on the outer surface of the self-thermal expansion assembly in a sleeving mode, the two ends of the flexible alloy cover body are fixedly connected to the outer wall of the oil-string casing, a water inlet hole is formed in the flexible alloy cover body, the self-thermal material can absorb well cementation prepad fluid through the water inlet hole and thermally expand, and the flexible alloy cover body can expand in the radial direction under the expansion effect of the self-thermal material. The well cementation method adopts an expansion combined casing pipe and comprises the following steps: lowering the expansion combined casing pipe into a shaft; well cementation prepad fluid is continuously injected into the shaft for 30-45 minutes; and cement paste is injected into the shaft. According to the invention, the well cementation operation efficiency can be improved, and the protection capability on the oil-string casing can be enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and in particular to an expansion combination casing and a cementing method. Background Art

[0002] During oil and gas field development, hydraulic fracturing or formation activity can easily cause natural fractures or faults to slip, resulting in shear displacement of casing, causing deformation, dislocation, and even collapse. Particularly in unconventional reservoirs such as shale oil and gas, large-scale volume fracturing can significantly activate the natural fracture network, increasing the risk of reservoir casing damage. Traditional cement sheaths, due to their rigidity, are unable to adapt to such dynamic formation displacements.

[0003] Expansion rubber casing is a current solution to this problem. This involves wrapping the outer wall of the reservoir casing with a water-swellable rubber layer. The moisture in the cementing slurry triggers the rubber to expand, filling the annular space between the reservoir casing and the wellbore. When the fault slips, the expanded rubber layer absorbs some of the displacement through elastic-plastic deformation, thereby reducing the shear displacement directly acting on the casing.

[0004] However, the expansion process of expandable rubber casing, which absorbs water from the cementing slurry, is relatively slow, typically taking several hours, which can affect the quality of the cementing operation. Furthermore, during the lowering process, the rubber casing comes into contact with the wellbore wall, which can easily tear and damage the rubber layer, weakening its expansion effect and rendering it ineffective in protecting the casing.

[0005] Therefore, there is an urgent need to provide an expansion combination casing and a method of using the same to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide an expandable combined casing and a cementing method, which can improve the efficiency of cementing operations and enhance the protective capability of the oil layer casing.

[0007] As conceived above, the technical solution adopted by the present invention is:

[0008] The expandable combined casing is used for cementing operations in a wellbore and comprises at least one casing unit, each of which comprises:

[0009] Oil layer casing;

[0010] A self-heating expansion component, which is sleeved on the outer surface of the oil layer casing and includes a flexible and permeable coating film and a self-heating material filled in the coating film;

[0011] A flexible alloy cover body is sleeved on the outer surface of the self-heating expansion component, and both ends of the flexible alloy cover body are fixedly connected to the outer wall of the oil layer casing. The flexible alloy cover body is provided with a water inlet hole, and the water in the wellbore can enter the flexible alloy cover body through the water inlet hole and penetrate into the coating film. The self-heating material can absorb water and expand thermally, and the flexible alloy cover body can expand radially under the expansion action of the self-heating material.

[0012] Furthermore, the expandable combined casing comprises at least two sections of the casing units and at least one coupling, and the two oil layer casings of two adjacent sections of the casing units are connected via the coupling.

[0013] Furthermore, both ends of the oil layer casing are provided with external threads, and the inner wall of the coupling is correspondingly provided with internal threads matching the external threads.

[0014] Furthermore, the length of the self-thermal expansion component is shorter than the length of the oil layer casing.

[0015] Furthermore, the flexible alloy cover includes a plurality of support members and a plurality of connecting members, and the plurality of support members are evenly spaced along the circumference of the oil layer casing, and each support member extends axially along the oil layer casing and has a periodic waveform structure. Two adjacent support members are mirror-symmetrical, and the symmetrical trough parts of two adjacent support members are connected by the connecting members, so that the plurality of support members and the plurality of connecting members together form a mesh frame structure, and the mesh holes of the mesh frame structure are the water inlet holes.

[0016] Furthermore, both ends of the flexible alloy cover are circumferentially welded to the outer wall of the oil layer casing around the oil layer casing.

[0017] Furthermore, the flexible alloy cover is made of stainless steel and cobalt-chromium alloy.

[0018] Furthermore, the coating film is made of a mixture of aramid fiber and polyester fiber.

[0019] A cementing method, using the expandable combination casing as described above, comprises:

[0020] S1. Lower the expansion casing into the wellbore;

[0021] S2. Continuously inject cementing pre-pad fluid into the wellbore for 30-45 minutes. The self-heating material absorbs the water in the pre-pad fluid and expands thermally, pushing the flexible alloy cover to expand radially.

[0022] S3. Cement slurry is injected into the wellbore. The cement slurry solidifies between the expanded flexible alloy cover and the inner wall of the wellbore to form a cement ring.

[0023] Beneficial effects of the present invention:

[0024] The present invention proposes an expansion combination casing, in which a self-heating expansion component and a flexible alloy cover are sequentially arranged on the outer wall of the oil layer casing, wherein the self-heating material in the self-heating expansion component undergoes an exothermic reaction when it comes into contact with water, expands in a short time, and immediately fills the annulus between the casing and the inner wall of the wellbore, forming an effective seal before the cement solidifies, thereby improving the quality of the cementing operation; the two ends of the flexible alloy cover are respectively rigidly connected to the oil layer casing, constructing a stable support system, which can not only effectively constrain the expansion direction and amount of the self-heating expansion component, but also absorb the shear displacement of the formation through the unique plastic deformation characteristics of the flexible alloy, thereby reducing the risk of tearing and enhancing the protection capability of the oil layer casing.

[0025] The present invention proposes a cementing method that uses an expansion combination casing. When injecting pre-fluid, the water absorption and thermal expansion characteristics of the self-heating material are utilized to drive the radial expansion of the flexible alloy cover, thereby improving the efficiency of the cementing operation and reducing the construction time. At the same time, the expanded flexible alloy cover and the subsequently formed cement ring work together to enhance the supporting strength between the expansion combination casing and the inner wall of the wellbore, thereby reducing the risk of damage to the oil layer casing due to sliding of faults / cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of an expandable combined casing before expansion provided by a specific embodiment of the present invention;

[0027] Figure 2 is a cross-sectional view of an expandable combined casing provided by a specific embodiment of the present invention before expansion;

[0028] Figure 3 This is a schematic diagram of the structure of the expansion combination casing after expansion provided by a specific embodiment of the present invention;

[0029] Figure 4 It is a structural schematic diagram of a flexible alloy cover provided by a specific embodiment of the present invention.

[0030] In the picture:

[0031] 1. Oil layer casing;

[0032] 2. Self-heating expansion component; 21. Coating film; 22. Self-heating material;

[0033] 3. Flexible alloy cover; 30. Water inlet; 31. Support member; 32. Connector;

[0034] 4. Coupling;

[0035] 100. Shaft. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0037] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0038] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0039] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0040] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0041] like Figure 1-Figure 4As shown, the present invention provides an expansion combination casing for cementing operations in a wellbore 100, comprising at least one casing unit, each casing unit comprising an oil layer casing 1, a self-heating expansion component 2 and a flexible alloy cover 3, the self-heating expansion component 2 being sleeved on the outer surface of the oil layer casing 1, and the self-heating expansion component 2 comprising a flexible and permeable coating 21 and a self-heating material 22 filled in the coating 21; the flexible alloy cover 3 being sleeved on the outer surface of the self-heating expansion component 2, and both ends of the flexible alloy cover 3 being fixedly connected to the outer wall of the oil layer casing 1, the flexible alloy cover 3 being provided with a water inlet hole 300, water in the wellbore 100 can enter the flexible alloy cover 3 through the water inlet hole 30 and penetrate into the coating 21, the self-heating material 22 can absorb water and undergo thermal expansion, and the flexible alloy cover 3 can expand radially under the expansion action of the self-heating material 22.

[0042] A self-heating expansion component 2 and a flexible alloy cover 3 are sequentially arranged on the outer wall of the oil layer casing 1, wherein the self-heating material 22 in the self-heating expansion component 2 undergoes an exothermic reaction when it comes into contact with water, expands in a short time, and immediately fills the annulus between the casing and the inner wall of the wellbore, forming an effective seal before the cement solidifies, thereby improving the quality of the cementing operation; the two ends of the flexible alloy cover 3 are rigidly connected to the oil layer casing 1 respectively, constructing a stable support system, which can not only effectively constrain the expansion direction of the self-heating expansion component 2, but also absorb the shear displacement of the formation through the unique plastic deformation characteristics of the flexible alloy, reduce the risk of tearing, and enhance the protection capability of the oil layer casing 1.

[0043] In the flexible and permeable coating 21, flexibility means that the coating 21 has a certain elastic deformation ability and can deform when the self-heating material 22 absorbs water and expands to adapt to the action of the expansion force, while maintaining the integrity of the coating 21 to avoid rupture; permeability means that the coating 21 allows water or water-based fluid to penetrate, so that the moisture in the cementing pre-fluid can penetrate into the coating 21 and contact with the self-heating material 22 to undergo an exothermic expansion reaction. At the same time, it also limits the penetration of solid particles, prevents the powder or reaction products of the self-heating material 22 from leaking out, and avoids contaminating the wellbore 100 or affecting the quality of the cement ring.

[0044] Specifically, if Figure 1-Figure 3 As shown, the expandable combined casing comprises at least two casing units and at least one coupling 4, wherein two oil layer casings 1 of two adjacent casing units are connected by the coupling 4. The coupling 4 connection design ensures the mechanical strength between adjacent casing units and maintains the integrity of the combined casing during the expansion process.

[0045] Specifically, the oil layer casing 1 has a first external thread on one end and a second external thread on the other end. The inner wall of the coupling 4 is correspondingly provided with a first internal thread that matches the first external thread, and a second internal thread that matches the second external thread. By adopting a differentiated matching thread structure at both ends, fast and precise fastening is achieved, significantly improving installation efficiency and reducing the difficulty of operation for operators.

[0046] In this embodiment, the first external thread and the second external thread are different in length, size and structure.

[0047] Specifically, the length of the self-expansion assembly 2 is shorter than the length of the oil layer casing 1, and the ends of the oil layer casing 1 are not covered by the self-expansion assembly 2. Downhole operations often require the use of equipment such as slips and pulling tools, which require reliable fulcrums. The ends of the oil layer casing 1 not covered by the self-expansion assembly 2 can provide a stable clamping surface for the tools, ensuring safe and stable tripping of the oil layer casing 1.

[0048] More specifically, the oil layer casing 1 is a 11-12m steel pipe, the length of the first external thread and the second external thread at both ends of the oil layer casing 1 is 10-15cm, the length of the elastic centralizer is 30-35cm, when the oil layer casing 1 is lowered, the length of the tongs grabbing the oil layer casing 1 is 40-50cm, the length of the slips is 50-60cm, and the length of the self-thermal expansion component 2 is 9-9.5m.

[0049] Specifically, if Figure 4 As shown, the flexible alloy cover 3 includes a plurality of support members 31 and a plurality of connecting members 32. The plurality of support members 31 are evenly spaced along the circumference of the oil layer casing 1. Each support member 31 extends axially along the oil layer casing 1 and has a periodic wave structure. Two adjacent support members 31 are mirror-symmetrical, and the symmetrical troughs of the two adjacent support members 31 are connected by connecting members 32, so that the plurality of support members 31 and the plurality of connecting members 32 together form a mesh frame structure, and the mesh of the mesh frame structure is the water inlet 30. The flexible alloy cover 3 is a mesh frame structure. The plurality of water inlet holes 300 greatly increase the contact area between the self-heating material 22 and the pre-fluid, so that the self-heating material 22 can quickly absorb water from multiple directions and undergo a thermal expansion reaction. In addition, the symmetrically arranged wave support members 31 can restrain each other during radial expansion, ensuring smooth expansion and preventing excessive deformation. At the same time, the rigid connection at the trough forms a stable force conduction node, so that the expansion stress is evenly distributed throughout the mesh frame structure.

[0050] Specifically, the flexible alloy cover 3 is circumferentially welded to the outer wall of the oil-layer casing 1 at both ends. This welding method forms a solid integrated structure between the flexible alloy cover 3 and the oil-layer casing 1, allowing the radial thrust generated by the self-thermal expansion component 2 during expansion to be evenly transmitted to the flexible alloy cover 3. At the same time, the weld seam enhances the deformation resistance of the connection when subjected to formation compression and shear forces, preventing the flexible alloy cover 3 from separating from the oil-layer casing 1.

[0051] Optionally, the flexible alloy cover 3 is made of stainless steel and cobalt-chromium alloy. These materials combine high strength, high toughness, and excellent corrosion resistance. Stainless steel provides basic support for the flexible alloy cover 3 and protects it from fluid corrosion, while cobalt-chromium alloy enhances stability in high-temperature and high-pressure environments. The combination of these two materials allows the flexible alloy cover 3 to withstand complex stresses and extreme temperatures, preventing the self-thermal expansion component 2 and the reservoir casing 1 from losing protection due to softening, brittle fracture, or corrosion failure.

[0052] In this embodiment, to meet the requirements of shale gas extraction at depths of 3000-4500m, bottomhole pressures approaching 100 MPa, and well temperatures of approximately 130-150°C, the outer flexible alloy cover 3 must meet the requirements of high temperature resistance, high strength, and wear resistance, while also possessing certain ductility and excellent machinability and weldability. The flexible alloy cover 3 is made of L605 cobalt-based high-temperature alloy, capable of normal operation at temperatures of 1000°C in corrosive environments. It has an elastic modulus of 243 GPa, a tensile strength greater than 860 MPa, a yield strength greater than 310 MPa, high elasticity, and a tensile elongation of 50%.

[0053] It should be noted that L605 cobalt-based high-temperature alloy is a high-performance material known in the art. It is a high-performance alloy mainly composed of cobalt and containing chromium, tungsten and nickel.

[0054] Optionally, the covering film 21 is made of a blend of aramid fiber and polyester fiber. Aramid fiber has a 19cNdtex -1 The polyester material has a breaking strength of more than 2 GPa, a tensile strength of more than 2 GPa, good insulation and aging resistance, and a temperature resistance of 200-240°C. It does not decompose or melt at a high temperature of 560°C. While meeting the requirements of high elasticity and high permeability, it also has high temperature resistance and stable chemical properties, can work normally at 200°C, and has a melting point of 255-265°C. After the two fibers are blended, the coating film 21 combines the characteristics of wear resistance, high elasticity, high permeability, and high temperature resistance. This can not only improve the safety of the combined casing during the installation process, but also enable the self-heating material 22 to function reliably and efficiently, thereby improving the adaptability and reliability of the combined casing in complex downhole environments.

[0055] In this embodiment, aramid fiber and polyester fiber are woven from fibers made from a polymer liquid crystal spinning solution in a ratio of 3:7 to accommodate the space expanded by the water vapor generated by heating the self-heating material 22. It should be noted that aramid fiber, polyester fiber, and polymer liquid crystal spinning solution are materials known in the art.

[0056] Optionally, the self-heating material 22 is composed of 40%-60% quicklime, 5%-10% activated carbon, 5%-10% aluminum powder, 3%-10% iron powder, 3%-10% coke powder and 1%-3% sodium carbonate, and the sum of the mass percentages of quicklime, activated carbon, aluminum powder, iron powder, coke powder and sodium carbonate is 100%.

[0057] Quicklime reacts with water to produce calcium hydroxide, releasing significant heat and accompanied by volume expansion. This is the core driving force of the self-heating material 22. When the quicklime mass is less than 40%, heat generation is insufficient and expansion is slow. When the quicklime mass is greater than 60%, the reaction is too intense, leading to uncontrolled initial heat generation and expansion rates, potentially causing localized stress overload in the flexible alloy cover 3. Activated carbon accelerates water penetration into the quicklime particles, shortening the reaction start-up time. When the activated carbon mass is less than 5%, the dispersion effect is insufficient, potentially causing localized accumulation of the quicklime. When the activated carbon mass is greater than 10%, the excess activated carbon dilutes the quicklime concentration, reducing total heat generation and expansion. Aluminum powder and water undergo a displacement reaction under alkaline conditions, releasing hydrogen and generating additional heat. The hydrogen accumulates to form pressure, which synergizes with the volume expansion of the quicklime and increases the radial expansion force. When the aluminum powder mass is less than 5%, the gas production and auxiliary heat are insufficient, the expansion force is limited, and it is difficult to effectively promote the expansion of the flexible alloy cover. When the aluminum powder mass is greater than 10%, the amount of hydrogen generated by the reaction is excessive, which may cause excessive pressure inside the self-heating expansion component 2 and cause the flexible alloy cover 3 to rupture. Iron powder and coke powder form a galvanic cell in water and sodium carbonate, accelerating the chemical reaction between aluminum powder and quicklime. When the mass of iron powder and coke powder is less than 3%, the galvanic cell effect is weak and the reaction rate is not significantly increased. When the mass of iron powder and coke powder is greater than 10%, the reaction is too rapid and heat is released in a concentrated manner, causing local overheating and damaging the coating 21. When the mass of sodium carbonate is less than 1%, the electrolyte concentration is insufficient, the galvanic cell efficiency is low, and the reaction rate is limited. When the mass of sodium carbonate is greater than 3%, the excess carbonate ions may react with calcium ions to form calcium carbonate precipitates, which block the coating 21, hinder water penetration, and inhibit subsequent reactions.

[0058] The present invention also provides a cementing method, using the above-mentioned expandable combined casing, comprising:

[0059] S1. Lowering the expansion combination casing into the wellbore 100;

[0060] S2. Continuously inject cementing pad fluid into the wellbore 100 for 30-45 minutes. The self-heating material 22 absorbs moisture in the pad fluid and undergoes thermal expansion, pushing the flexible alloy cover 3 to expand radially.

[0061] S3. Cement slurry is injected into the wellbore 100. The cement slurry solidifies between the expanded flexible alloy cover 3 and the inner wall of the wellbore 100 to form a cement ring.

[0062] This method uses an expansion combination casing and utilizes the water absorption and thermal expansion characteristics of the self-heating material 22 to drive the radial expansion of the flexible alloy cover 3 when injecting the pre-fluid, thereby improving the cementing operation efficiency and reducing the construction time; at the same time, the expanded flexible alloy cover 3 and the subsequently formed cement ring work together to enhance the support strength between the expansion combination casing and the inner wall of the wellbore 100, thereby reducing the risk of damage to the oil layer casing 1 due to sliding of the fault / crack.

[0063] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An expandable composite casing for cementing operations in a wellbore (100), characterized in that: It comprises at least one casing unit, each of which comprises: Oil layer casing (1); A self-heating expansion component (2), the self-heating expansion component (2) being sleeved on the outer surface of the oil layer casing (1), and the self-heating expansion component (2) comprising a flexible and permeable coating film (21) and a self-heating material (22) filled in the coating film (21); A flexible alloy cover (3) is provided, wherein the flexible alloy cover (3) is sleeved on the outer surface of the self-heating expansion component (2), and both ends of the flexible alloy cover (3) are fixedly connected to the outer wall of the oil layer casing (1); the flexible alloy cover (3) is provided with a water inlet hole (30); water in the wellbore (100) can enter the flexible alloy cover (3) through the water inlet hole (30) and penetrate into the coating film (21); the self-heating material (22) can absorb water and undergo thermal expansion; and the flexible alloy cover (3) can expand radially under the expansion action of the self-heating material (22).

2. The expansion combination casing according to claim 1, characterized in that: The expandable combined casing comprises at least two sections of casing units and at least one coupling (4), and the two oil layer casings (1) of two adjacent sections of the casing units are connected via the coupling (4).

3. The expansion combination casing according to claim 2, characterized in that: The two ends of the oil layer casing (1) are provided with a first external thread at one end and a second external thread at the other end, and the two ends of the coupling (4) are correspondingly provided with a first internal thread matching the first external thread and a second internal thread matching the second external thread.

4. The expansion combination casing according to claim 1, characterized in that: The length of the self-thermal expansion component (2) is shorter than the length of the oil layer casing (1), and both ends of the oil layer casing (1) are not covered by the self-thermal expansion component (2).

5. The expansion combination casing according to claim 1, characterized in that: The flexible alloy cover (3) comprises a plurality of support members (31) and a plurality of connecting members (32), wherein the plurality of support members (31) are evenly spaced along the circumference of the oil layer casing (1), and each support member (31) extends axially along the oil layer casing (1) and has a periodic wave structure, wherein two adjacent support members (31) are mirror-symmetrical, and the symmetrical troughs of the two adjacent support members (31) are connected by the connecting member (32), so that the plurality of support members (31) and the plurality of connecting members (32) together form a mesh frame structure, and the meshes of the mesh frame structure are the water inlet holes (30).

6. The expansion combination casing according to claim 1, characterized in that: The two ends of the flexible alloy cover (3) are circumferentially welded to the outer wall of the oil layer casing (1) around the oil layer casing (1).

7. The expansion combination casing according to any one of claims 1 to 6, characterized in that: The flexible alloy cover (3) is made of stainless steel and cobalt-chromium alloy.

8. The expansion combination casing according to any one of claims 1 to 6, characterized in that: The coating film (21) is made of a mixture of aramid fibers and polyester fibers.

9. A cementing method, characterized in that: The expansion combination casing according to any one of claims 1 to 8 comprises: S1, lowering the expansion combination casing into the wellbore (100); S2, continuously injecting cementing pre-fluid into the wellbore (100) for 30-45 minutes, so that the self-heating material (22) absorbs the water in the pre-fluid and expands thermally, pushing the flexible alloy cover (3) to expand radially; S3. Cement slurry is injected into the wellbore (100), and the cement slurry solidifies between the expanded flexible alloy cover (3) and the inner wall of the wellbore (100), forming a cement ring.

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