Underground packing tool and packing method

Abstract

The invention relates to the technical field of oil and gas exploitation, in particular to an underground packing tool and a packing method.The tool comprises an oil pipe body, a hydration expansion sealing body, a fixed end assembly and a floating end assembly; the hydration expansion sealing body is arranged on the outer side of the oil pipe body in a sleeving mode and extends in the axial direction of the oil pipe body. The hydration expansion sealing body is used for expanding through metal hydration reaction with well fluid; the fixed end assembly and the floating end assembly are arranged at the two ends of the hydration expansion sealing body respectively. The floating end assembly is used for limiting the oil pipe body in the axial direction and deforming at the high temperature to relieve limiting. The fixed end assembly is used for driving the end of the hydrated expansion sealing body to expand in the radial direction through well fluid so as to be tightly attached to the well wall to complete setting. According to the packing tool, the high-temperature resistance of an existing underground packer can be improved, so that the production requirements of deep and ultra-deep wells are met.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas extraction, and in particular to a downhole isolation tool and an isolation method. Background Art

[0002] During oil and gas production, high-temperature, high-pressure oil and gas reservoirs and high-temperature geothermal resources require reservoir modification to increase and stabilize production. Due to high downhole temperatures, high-temperature-resistant external packers must be used to isolate the annulus, thereby extending the development life of wells constructed using horizontal openhole completion techniques. The performance of the packers directly determines the effectiveness of downhole processing.

[0003] Currently, packers are primarily categorized into mechanical and self-expanding types. Mechanical packers are further divided into compression and hydraulic expansion types. Their key components include slips, compression (expanding) rubber cartridges, retaining pins, and release mechanisms. Compared to mechanical packers, self-expanding packers lack complex mechanical structures and primarily utilize a long rubber cartridge made of a rubber material that self-expands in the presence of oil or water. Primary rubber materials include nitrile, carboxylated nitrile, hydrogenated nitrile, and EPDM, all of which generally withstand temperatures below 150°C. While fluoropolymer can withstand temperatures exceeding 200°C, it is expensive and not suitable for widespread use. For development projects with higher reservoir temperatures, such as hot dry rock reservoir reconstruction and deep wells with abnormal geothermal gradients, high-temperature cementing is often used for isolation. However, high temperatures can easily weaken and disintegrate the cement stone, leading to ineffective sealing of the cement sheath. Therefore, there is an urgent need for a high-temperature downhole packer to address these issues. Summary of the Invention

[0004] This application proposes a downhole isolation tool and isolation method, which aims to improve the high-temperature resistance of existing downhole isolation tools to meet the production needs of deep and ultra-deep wells.

[0005] In a first aspect, the present application discloses a downhole isolation tool, the tool comprising a tubing body, a hydration-swellable seal, a fixed end assembly, and a floating end assembly;

[0006] The hydration expansion sealing body is sleeved on the outside of the oil pipe body and extends axially along the oil pipe body;

[0007] The hydration expansion seal can undergo metal hydration reaction with well fluid to expand;

[0008] The fixed end assembly and the floating end assembly are respectively arranged at two ends of the hydration expansion sealing body;

[0009] The floating end assembly is used to limit the oil pipe body in the axial direction and release the limit when the temperature reaches a preset temperature;

[0010] The fixed end assembly is fixed to the oil pipe body and is used to drive the end of the hydration expansion seal body to expand radially under the action of hydraulic pressure so as to close to the well wall to complete the sealing.

[0011] Optionally, the material of the hydrated expansion seal comprises expandable metal and adhesive;

[0012] The expandable metal is used to undergo a metal hydration reaction with the well fluid to expand;

[0013] The adhesive is used to react with metal ions in the well fluid to form a gel, so that the expanded hydrated expansion seal is tightly bonded to the well wall.

[0014] Optionally, a protective layer is provided outside the hydration expansion sealing body;

[0015] The protective layer is made of decomposable alloy material;

[0016] The decomposable alloy material can be decomposed in well fluid with mineralization but not in air.

[0017] Optionally, the fixed end assembly includes a fixed component, a one-way valve component and an expandable anti-burst body;

[0018] The fixing assembly is fixed to the oil pipe body;

[0019] The expandable anti-burst body is located between the hydration expansion sealing body and the one-way valve assembly;

[0020] The one-way valve assembly is located in the fixed assembly and is used to pass well fluid into the expandable burst prevention body;

[0021] The end portion of the expandable anti-bumping body is embedded in the hydration expansion sealing body and can be expanded radially under the action of hydraulic pressure to drive the end portion of the hydration expansion sealing body to expand radially.

[0022] Optionally, the fixed end assembly further includes a sliding body;

[0023] The sliding body is arranged between the one-way valve assembly and the expandable anti-burst body, and is dynamically sealed with the fixed assembly;

[0024] The sliding body is used to move toward the inside of the expandable outburst prevention body under the drive of well fluid, so as to expand the expandable outburst prevention body.

[0025] Optionally, the sliding body includes a cone segment;

[0026] The front end portion of the cone segment can extend into the expandable outburst prevention body to expand the expandable outburst prevention body in the radial direction.

[0027] Optionally, the sliding body further comprises a cylindrical section;

[0028] The cylindrical section is located at the rear end of the cone section and is dynamically sealed with the fixing assembly.

[0029] Optionally, the inner side of the expandable anti-outburst body has an inner conical surface that is compatible with the conical section of the sliding body.

[0030] Optionally, the expandable outburst prevention body includes a plurality of expandable outburst prevention units sequentially connected along the circumferential direction;

[0031] Each of the expandable anti-bumping units has an embedded portion at an end close to the hydrated and swelled sealing body, and the embedded portion is embedded in the hydrated and swelled sealing body.

[0032] Optionally, the fixing assembly includes a first limiting ring, an intermediate joint and an end joint connected in sequence;

[0033] The first limiting ring is sealed and connected to the oil pipe body;

[0034] The end joint is sealedly connected to the sliding body;

[0035] The first limiting ring, the middle joint, the end joint, the sliding body and the oil pipe body form a sealed cavity;

[0036] The one-way valve assembly is arranged in the sealing cavity and connected to the middle joint.

[0037] Optionally, the end of the end joint close to the hydration expansion seal has an inwardly inclined inner conical surface structure;

[0038] The inner conical surface structure abuts against the conical section of the sliding body and is used to limit the axial movement of the sliding body.

[0039] Optionally, the fixed end assembly further includes a filter element;

[0040] The filter element is arranged in the sealing cavity and located at the inlet of the one-way valve assembly.

[0041] Optionally, the floating end assembly includes a positioning ring;

[0042] A positioning groove is provided on the oil pipe body;

[0043] The positioning ring can be embedded in the positioning groove at room temperature to be fixed to the oil pipe body, and can be deformed when the temperature rises to the transition temperature and detached from the positioning groove to float relatively with the oil pipe body.

[0044] Optionally, the floating end assembly further includes a second limiting ring;

[0045] The second limiting ring is dynamically sealed with the oil pipe body;

[0046] The positioning ring is arranged in the second limiting ring.

[0047] In a second aspect, the present application discloses a downhole isolation method, wherein the method uses the downhole isolation tool according to the first aspect, and the method comprises:

[0048] Connect the downhole isolation tool to the downhole tubing and run it into the wellbore;

[0049] The floating end assembly deforms at high temperatures to release the limit;

[0050] After being exposed, the hydration expansion seal undergoes a metal hydration reaction with the well fluid and expands;

[0051] The wellbore is pressurized to allow well fluid to enter the fixed end assembly, and the well fluid drives the end of the hydrated expansion seal to expand radially to fit closely to the well wall.

[0052] Based on the above technical solution, the beneficial effects of this application compared with the prior art are as follows:

[0053] 1. The hydrated expandable seal in the embodiments of this application utilizes a hydrated expandable alloy. The expanded hydrated expandable alloy exhibits high-temperature resistance comparable to that of high-temperature cementitious materials and superior to elastomeric materials such as synthetic rubber. Therefore, it can effectively meet the development requirements of deep and ultra-deep oil and gas wells and high-temperature geothermal wells.

[0054] 2. In the embodiments of the present application, the hydration-swellable seal is secured at one end by a fixed end assembly and floated at the other end by a floating end assembly. Once the isolation tool is lowered into position, the floating end assembly is first released from its position with respect to the tubing body, as the reservoir temperature is higher than the transition temperature of the positioning ring. Then, as the hydration-swellable seal reacts and expands, the fixed end assembly expands outward along with the hydration-swellable seal, jointly with the hydration-swellable seal to withstand the high pressure differential in the wellbore and prevent the end of the hydration-swellable seal from being excessively squeezed out.

[0055] 3. The hydrated expansion seal in the embodiments of the present application is primarily composed of expandable metal and a binder, resulting in a relatively simple manufacturing process and low material costs. Furthermore, since the isolation tool omits complex mechanical sealing mechanisms such as slips and anchors, the processing and assembly process is simplified, resulting in a low overall assembly cost. This also reduces the risk of tool failure, resulting in high overall tool reliability and a longer service life.

[0056] 4. The operation process of the downhole isolation tool in the embodiment of the present application is simple. After the isolation tool is lowered into the wellbore, the relevant chemical reaction is automatically completed. The operator only needs to pressurize the ground to drive and expand the expandable anti-blowout body to enable the hydrated expansion sealing body to be sealed. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is an overall schematic diagram of a downhole isolation tool in an embodiment of the present application;

[0058] Figure 2 is a partial schematic diagram of the fixed end assembly in an embodiment of the present application;

[0059] Figure 3 is a partial schematic diagram of the floating end assembly in an embodiment of the present application;

[0060] Figure 4 is a schematic diagram of a protective layer in an embodiment of the present application;

[0061] Figure 5 Schematic diagram of an expandable anti-burst body in an embodiment of the present application;

[0062] Figure 6 Schematic diagram of an expansion type outburst prevention unit in an embodiment of the present application;

[0063] Figure 7 It is a flow chart of the downhole isolation method in the embodiment of the present application.

[0064] Description of reference numerals:

[0065] 1. Oil pipe body; 11. Positioning groove;

[0066] 2. Hydration expansion seal;

[0067] 3. Fixed end assembly; 31. Fixed assembly; 311. First stop ring; 312. Intermediate joint; 313. End joint; 3131. Inner cone structure; 32. One-way valve assembly; 321. Valve seat; 322. Valve body; 323. Spring; 324. Valve ball; 33. Sliding body; 331. Cylindrical section; 332. Conical section; 34. Expandable anti-burst body; 341. Expandable anti-burst unit; 342. Embedded portion; 35. Sealing chamber; 36. Filter element; 37. Rupture disk;

[0068] 4. Floating end assembly; 41. Positioning ring; 42. Second limiting ring;

[0069] 5. Protective layer. 6. Sealing ring. DETAILED DESCRIPTION

[0070] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0071] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.

[0072] In the description of this disclosure, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this disclosure and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this disclosure. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0073] In the description of this disclosure, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this disclosure based on the specific circumstances.

[0074] The inventors discovered that the self-expanding downhole packers commonly used in the prior art are primarily made of rubber materials, including nitrile, carboxylated nitrile, hydrogenated nitrile, and EPDM. These materials generally have a temperature resistance below 150°C, while the actual temperatures in deep and ultra-deep completion and fracturing wells can reach 200°C and above. Therefore, these materials are unable to meet the production needs of deep and ultra-deep wells. While some rubber materials, such as fluororubber, can withstand temperatures above 200°C, their high price makes them difficult to widely adopt. To address this issue, the inventors conducted further research and development, resulting in the present invention.

[0075] In the first aspect, the embodiment of the present application provides a downhole isolation tool, referring to Figure 1-Figure 3The tool includes a tubing body 1, a hydration expansion seal 2, a fixed end assembly 3 and a floating end assembly 4; the hydration expansion seal 2 is sleeved on the outside of the tubing body 1 and extends axially along the tubing body 1; the hydration expansion seal 2 is used to expand by undergoing a metal hydration reaction with the well fluid; the fixed end assembly 3 and the floating end assembly 4 are respectively arranged at both ends of the hydration expansion seal 2; the floating end assembly 4 is used to limit the tubing body 1 in the axial direction and deform at high temperature to release the limit; the fixed end assembly 3 is used to drive the end of the hydration expansion seal 2 to expand radially through the well fluid so as to fit closely to the well wall.

[0076] The downhole isolation tool in the present application uses a hydrated expansion alloy material as the expansion material. This material can undergo a metal hydration reaction with the well fluid, and the volume of the generated product is higher than that of the original alloy material. The generated product of this reaction is close to the properties of materials such as cement and rock, which is conducive to the hydrated expansion seal 2 to be tightly bonded to the well wall after expansion and sealing. Under room temperature conditions, the volume expansion rate of the hydrated expansion seal 2 can reach 3-5 times, and under high temperature conditions, the expansion rate is faster and more stable, which is conducive to improving the downhole sealing effect of high-temperature wells to meet the production needs of deep and ultra-deep wells. In addition, the cost of alloy materials is lower than that of some rubber materials, which is conducive to large-scale popularization.

[0077] In an optional embodiment, the hydrated expansion seal 2 in the embodiment of the present application includes an expandable metal and an adhesive. The expandable metal is used to undergo a metal hydration reaction with the well fluid to expand, and the adhesive is used to react with metal ions to form a gel, which can enhance the structural strength of the expansion body so that the hydrated expansion seal 2 fits tightly against the well wall.

[0078] Specifically, the expandable metal may include a variety of metals or metal alloys. The principle of the metal hydration reaction is: the expandable metal undergoes a metal hydration reaction in brine to form a metal hydroxide, and the volume of the metal hydroxide is higher than that of the original metal material. For example, the volume of Mg(OH)2 increases by about 85% compared to Mg, the volume of Ca(OH)2 increases by about 32% compared to Ca, and the volume of Al(OH)3 increases by about 160% compared to Al. The increase in volume causes the expandable metal to expand, thereby forming a seal at the interface with the adjacent surface. The adhesive has strong bonding force, high strength, good acid resistance and heat resistance, and can react with metal ions in the solution to form a gel. The product is close to the properties of materials such as cement and rock, and can make the hydrated expansion seal 2 more tightly bonded to the well wall after expansion and sealing.

[0079] In an optional embodiment, the metals in the expandable metal of the present application include, but are not limited to, magnesium, calcium, aluminum, iron, nickel, copper, chromium, tin, zinc, etc., or any combination thereof. Preferred are magnesium, calcium, and aluminum. Metal alloys include, but are not limited to, any alloy of magnesium, calcium, aluminum, iron, nickel, copper, chromium, tin, zinc, etc. In some examples, the metal alloy may include non-metallic alloying elements. The expandable metal is dispersed in a binder. The binder may be degradable or non-degradable; in some specific embodiments, the binder may be expandable or non-expandable. The binder includes, but is not limited to, sodium silicate, PAM, polyvinyl alcohol, polylactic acid, polyurethane, polyglycolic acid, nitrile rubber, isoprene rubber, PTFE, silicone, fluoroelastomer, vinyl rubber, and PEEK, etc., or any combination thereof. In the embodiments of the present application, sodium silicate is preferred.

[0080] In a specific embodiment, Mg, Ca, or their alloys are selected as the expandable metal, and sodium silicate is selected as the binder. The magnesium ions and calcium ions in the solution react rapidly with the sodium silicate to form silicate gel and very strong calcium silicate and magnesium silicate gel. The chemical reaction formula is as follows:

[0081] Na2O·nSiO2+CaCl2=2NaCl+CaO·nSiO2↓

[0082] Na2O·nSiO2+MgCl2=2NaCl+MgO·nSiO2↓

[0083] In an optional embodiment, a protective layer 5 is provided on the outside of the hydration expansion seal 2, which can protect the hydration expansion seal 2 to prevent the metal hydration reaction from occurring prematurely and setting the seal before the tool is lowered into place. At the same time, it can prevent the hydration expansion seal 2 from being scratched and damaged by the well wall during the downhole process. Figure 4 The protective layer 5 is wound around the outside of the hydrated expansion sealing body 2 in the form of a spiral strip. When wrapping, it is necessary to ensure that the arrangement is tight so that the hydrated expansion sealing body 2 is not exposed.

[0084] In a specific embodiment, the protective layer 5 is made of a decomposable alloy material, which can decompose based on electrochemical principles in a well fluid with a mineralization degree, but does not decompose in the air. Specifically, the decomposable alloy material includes but is not limited to aluminum alloy, magnesium alloy, copper alloy, iron alloy, zinc alloy, etc., and the above alloys can decompose in water (well fluid) containing carbonates, bicarbonates, chlorides, sulfates, nitrates and various sodium salts of metals such as calcium, magnesium, aluminum and manganese. In the embodiment of the present application, the decomposable alloy material is preferably a magnesium-aluminum alloy. The metal ions released during the decomposition of the protective layer 5, as reactants of the metal hydration reaction, can promote the hydration reaction of the hydrated expansion seal 2.

[0085] Furthermore, in high-temperature wells, due to the high-temperature expansion effect, large internal stresses are easily generated inside the tubing and tools. Since there are differences in the expansion coefficients of various regions of the hydrated expansion seal 2, after the tubing is lowered into place and the oil and gas well is put into production, the expansion amounts of various regions at high temperatures are different, which will cause a large relative displacement and internal stress between the end of the hydrated expansion seal 2 and the tubing, which will affect the pressure-bearing performance and sealing service life of the hydrated expansion seal 2 over a long period of time. Therefore, the sealing tool in the embodiment of the present application is further improved by adopting a fixed end assembly 3 and a floating end assembly 4 to form a pressure-bearing assembly at the end of the hydrated expansion seal 2, so that one end of the hydrated expansion seal 2 is fixed and the other end is floatingly limited, thereby improving the pressure-bearing performance and sealing service life of the hydrated expansion seal 2.

[0086] In an alternative embodiment, referring to Figure 2 The fixed end assembly 3 includes a fixed component 31, a one-way valve component 32, a sliding body 33 and an expandable anti-blowout body 34. The fixed component 31 is fixed to the tubing body 1; the hydration expansion seal 2, the sliding body 33, the expandable anti-blowout body 34 and the one-way valve component 32 are sequentially distributed along the axial direction of the tubing body 1; the one-way valve component 32 is located inside the fixed component 31 and is used to allow well fluid to enter to drive the expandable anti-blowout body 34 to expand radially; the sliding body 33 is used to move toward the inside of the expandable anti-blowout body 34 under the drive of the well fluid to expand the expandable anti-blowout body 34; the expandable anti-blowout body 34 is used to drive the end of the hydration expansion seal 2 to expand radially by being embedded in the hydration expansion seal 2.

[0087] Reference Figure 1 , refer to Figure 2 The fixing assembly 31 includes a first retaining ring 311, an intermediate joint 312, and an end joint 313, which are connected in sequence. The first retaining ring 311 is sealed to the tubing body 1. Specifically, the small-diameter inner surface of the first retaining ring 311 has a prefabricated crimping groove, and the outer surface of the tubing body 1 also has a corresponding crimping groove at a corresponding position. During assembly, a hydraulic crimping machine can be used to secure the first retaining ring 311 to the tubing body 1. Since the crimped joint surface has a certain sealing capability, a sealed connection is achieved, preventing external high-pressure well fluid from entering the interior of the fixed end assembly 3 through this joint surface.

[0088] Further, continue to refer to Figure 2 The first stop ring 311, the intermediate joint 312, and the end joint 313 are sequentially threadedly connected, and the end joint 313 is further sealed with the sliding body 33. Thus, the first stop ring 311, the intermediate joint 312, the end joint 313, the sliding body 33, and the oil pipe body 1 collectively enclose a sealed cavity 35. The one-way valve assembly 32 is disposed in the sealed cavity 35 and is screwed into the intermediate joint 312 via threads.

[0089] Specifically, refer to Figure 2 The one-way valve assembly 32 includes a valve seat 321, a spring 323, a valve ball 324, and a valve body 322. The outer surface of the valve body 322 is threaded and is threadedly connected to the intermediate joint 312 via the threaded structure. The valve seat 321 is located at the bottom of the valve body 322, and the spring 323 is embedded between the valve seat 321 and the valve ball 324. The valve ball 324 is pressed against the inner conical surface of the valve body 322 by the pre-tensioned spring 323, forming an effective seal.

[0090] In an alternative embodiment, referring to Figure 2 A sealing ring 6 is further provided between the valve body 322 and the intermediate joint 312 , and the sealing ring 6 can further seal the valve body 322 to prevent the fluid entering the valve body 322 from flowing.

[0091] In an alternative embodiment, referring to Figure 2 A filter element 36 is also located within the sealed cavity 35, at the fluid inlet of the valve body 322. This element filters solid impurities from the high-pressure fluid entering the one-way valve assembly, preventing them from damaging the seal ring 6 and wearing out important components. Correspondingly, a rupture disk 37 is provided on the other side of the oil pipe body 1, designed to rupture at a predetermined pressure and temperature to relieve pressure.

[0092] In a specific implementation, by increasing the pressure within the tubing body 1 to exceed the burst pressure of the rupture disk 37, the rupture disk 37 ruptures, allowing well fluid to pass through the filter element 36 and into the one-way valve assembly 32 within the sealing chamber 35. The one-way valve assembly allows fluid at a certain pressure to pass through, preventing backflow caused by fluid pressure fluctuations, thereby ensuring the stability of the seal. Consequently, under the action of the one-way valve assembly 32, the high-pressure fluid flows at a certain pressure toward the slider 33, further applying force to the slider 33, causing it to move axially.

[0093] In an alternative embodiment, referring to Figure 2 The slider 33 comprises a cylindrical section 331 and a conical section 332. The cylindrical section 331 is located near the one-way valve assembly 32, while the conical section 332 is located near the expandable anti-bumping body 34. The cylindrical section 331 has a set of sealing grooves on its inner and outer surfaces, each containing a sealing ring 6 to prevent fluid leakage during axial movement of the slider 33. The conical section 332 has an inner diameter that gradually decreases from the end near the cylindrical section 331 to the end near the expandable anti-bumping body 34.

[0094] In an alternative embodiment, referring to Figure 2The end of the end fitting 313 near the hydration-swelling seal 2 has an inwardly inclined inner conical surface structure 3131. Specifically, the inner conical surface structure 3131 of the end fitting 313 abuts against the vertebral segment of the sliding body 33, thereby limiting the axial movement of the sliding body 33 and preventing excessive pressure within the tubing body 1 during fracturing operations from causing the sliding body 33 to apply excessive load to the expandable burst prevention body 34, thereby causing the hydration-swelling seal 2 to be cracked or damaged.

[0095] In an alternative embodiment, referring to Figure 5 and Figure 6 The expandable anti-burst body 34 is specifically a closed annular body formed by a number of expandable anti-burst units 341 connected in sequence along the circumferential direction. The lower part of the inner wall of the annular body is a cylindrical surface, and the upper part of the inner wall of the annular body near the sliding body 33 is a conical surface (not shown in the figure). The surface of the conical section of the sliding body 33 fits with the inner conical surface of the expandable anti-burst body 34. Furthermore, each expandable anti-burst unit 341 has an embedded portion 342 near the end of the hydration expansion sealing body 2. The inner side wall and / or the outer side wall of the embedded portion 342 are provided with embedded teeth to improve the embedding degree of the expandable anti-burst unit 341. The expandable anti-burst body 34 is made of nylon material, which can reduce friction during movement. The expandable anti-burst unit 341 is a petal-type structure. During the radial expansion movement, the mating surfaces of the two adjacent expandable anti-burst units 341 are kept in contact, reducing the possibility of high-pressure fluid flowing from the inside.

[0096] Driven by the high-pressure fluid, the sliding body 33 slides toward the side of the hydration expansion seal 2. Since each expandable anti-blowout unit 341 is embedded in the hydration expansion seal 2, the conical section of the sliding body 33 expands the expandable anti-blowout body 34, causing it to expand outward together with the continuously expanding hydration expansion seal 2. The expandable anti-blowout body 34 that expands to the well wall and the hydration expansion seal 2 withstand the high pressure difference in the wellbore together, which can prevent the end of the hydration expansion seal 2 from being excessively squeezed out.

[0097] In an alternative embodiment, referring to Figure 3 The floating end assembly 4 includes a locating ring 41, and a locating groove 11 is defined in a corresponding position on the tubing body 1. The locating ring 41 is embedded in the locating groove 11 at room temperature to secure the tubing body 1. When the temperature rises to a transition temperature, the locating ring 41 deforms and releases from the locating groove 11, allowing it to float relative to the tubing body 1.

[0098] Specifically, the positioning ring 41 is made of shape memory alloy (SMA). The characteristics of shape memory alloy are: when the part is processed at its higher transition temperature point, the part will "remember" its own state at that temperature. The part can be transformed into the desired shape through processing at room temperature. When the system is working and the ambient temperature reaches the transition temperature of the shape memory alloy, the part automatically returns to its initial state. When the positioning ring 41 is processed, the temperature is raised to a temperature value higher than the transition temperature so that it "remembers" the initial shape. After processing, its outer diameter is appropriately reduced at room temperature so that it can be placed in the positioning groove 11 of the tubing body 1 when assembling the isolation tool, so that the floating end assembly 4 is fixed relative to the tubing body 1. By adjusting the transition temperature of the shape memory alloy, it can adapt to different downhole temperatures.

[0099] It should be noted that shape memory alloy (SMA) materials include but are not limited to: Ni-Ti based, Cu based and Fe based, or any combination thereof, and the transition temperature thereof can be specifically set according to downhole conditions.

[0100] In an alternative embodiment, referring to Figure 3 The floating end assembly 4 also includes a second retaining ring 42. The positioning ring 41 is disposed within the second retaining ring 42, which is dynamically sealed with the tubing body 1. Specifically, the second retaining ring 42 employs the same structure and connection method as the first retaining ring 311. A sealing ring 6 is also disposed between the second retaining ring 42 and the tubing body 1 to ensure downhole sealing after the packer tool is seated.

[0101] Therefore, the packer tool's floating end assembly 4 utilizes a locating ring 41 made of shape memory alloy (SMA) to achieve floating position retention of the tubing body 1. At room temperature, the locating ring 41, through machining and the relative sealing provided by a second retaining ring 42, is embedded within the locating groove 11 of the tubing body 1, securing the floating end assembly 4 relative to the tubing body 1. Once the temperature rises to its transition temperature, the locating ring 41 returns to its initial state, disengaging from the locating groove 11 and releasing its attachment to the tubing body 1.

[0102] It should be noted that the floating end assembly 4 further includes the end joint 313, intermediate joint 312, one-way valve assembly 32, slider 33, and expandable anti-bumping body 34 of the fixed end assembly 3. This also enables hydraulically driven radial expansion of the end of the hydration expansion seal 2, which will not be further described here.

[0103] In summary, the isolation tool in the embodiment of the present application adopts a hydrated expansion alloy material system as an expansion body, and a fixed end assembly 3 is used to fix one end of the hydrated expansion seal 2, and a floating end assembly 4 is used to float and limit the other end. When the isolation tool is lowered into place, since the reservoir temperature is higher than the transition temperature of the positioning ring 41, the floating end assembly 4 is first released from the fixation with the oil pipe body 1. Then, after the hydrated expansion seal 2 reacts and expands, the rupture disk 37 is exploded by increasing the internal pressure of the wellbore, and then the high-pressure well fluid drives the sliding body 33 to move through the one-way valve assembly 32, so as to drive the expandable anti-blowout body 34 to expand radially, and drive the end of the hydrated expansion seal 2 to stick to the well wall or the inner wall of the upper casing, thereby preventing the end of the hydrated expansion seal 2 from being excessively squeezed out.

[0104] In the second aspect, the present invention provides a downhole isolation method, referring to Figure 7 The method uses the downhole isolation tool of the first aspect, specifically comprising:

[0105] S1: Connect the downhole isolation tool to the downhole tubing and lower it into the wellbore. Before lowering into the wellbore, the function of the isolation tool is first checked on the ground. If there is no problem, the isolation tool is connected to the production or fracturing tubing and lowered into the well. It should be noted that a shape memory alloy (SMA) material whose transformation temperature does not exceed the temperature in the wellbore to be lowered is selected and processed at a temperature value higher than the transformation temperature so that it "remembers" its initial shape. After processing, its outer diameter is appropriately reduced at room temperature so that it can be placed in the positioning groove 11 of the oil pipe body 1 when assembling the isolation tool.

[0106] S2: Floating end assembly 4 deforms at high temperature to release the restraint. Specifically, after the packer tool is lowered into position, the wellbore temperature exceeds the transition temperature of the shape memory alloy, causing the retaining ring 41 to expand and return to its original shape, disengaging from the retaining groove 11 of the tubing body 1. This releases the restraint of the floating end assembly 4.

[0107] S3: After being exposed, the hydrated swellable seal 2 undergoes a metal hydration reaction with the well fluid, causing it to expand. After the isolation tool is lowered into the wellbore, the protective layer 5 first comes into contact with the well fluid and undergoes an electrochemical reaction, gradually decomposing and shedding, exposing the hydrated swellable seal 2 within. The swellable seal further undergoes a metal hydration reaction under the action of the well fluid, gradually expanding in volume.

[0108] S4: Pressurize the wellbore to allow the well fluid to enter the fixed end assembly, and the well fluid drives the end of the hydrated expansion seal to expand radially to fit closely to the well wall. Specifically, the pressure can be increased by performing a pressure operation at the wellhead on the ground, and the pressure in the wellbore can be increased in a step-by-step manner until the bursting pressure value of the rupture disk 37 is reached. After the rupture disk 37 explodes, the well fluid enters the sealing chamber 35 in the fixed end assembly 3. After entering the sealing chamber 35, the well fluid acts on the sliding body 33 after passing through the one-way valve assembly 32. The sliding body 33 moves axially and drives the expandable anti-blowout body 34 to open, thereby driving the end of the hydrated expansion seal 2 to expand radially until it fits closely to the well wall or the inner wall of the upper casing. During actual construction, it is necessary to pressurize the wellhead and stabilize the pressure for about half an hour before releasing the pressure to ensure that the hydrated expansion seal 2 is completely sealed. Subsequently, annular pressure construction is carried out to verify the sealing effect of the isolation tool.

[0109] The downhole isolation tool in the embodiment of the present application is based on a hydrated expandable alloy material and can effectively meet the development requirements of deep and ultra-deep oil and gas and high-temperature geothermal wells. First, the hydrated expandable alloy material has better high-temperature resistance. The high-temperature resistance of the material formed after expansion is comparable to that of high-temperature resistant cement materials and is superior to elastomeric materials such as synthetic rubber. Second, the cost of the entire tool is low. The hydrated expandable seal 2 is mainly composed of expandable metal and adhesive, and the preparation process is relatively simple, with low material cost. Moreover, since the isolation tool omits complex mechanical sealing mechanisms such as slips and anchoring mechanisms, the processing and assembly processes are simple, so the overall assembly cost of the tool is also low. Furthermore, since the isolation tool in the present application has a simple and compact structure and omits complex mechanical sealing mechanisms, the risk of tool failure is reduced, the overall reliability of the tool is high, and the service life is longer. Finally, the operation process of the downhole isolation tool is simple. After the isolation tool is lowered into the wellbore, the relevant chemical reactions are automatically completed. The operator only needs to pressurize the ground to drive and propel the expandable anti-blowout body 34 to achieve the sealing of the hydrated expandable seal 2.

[0110] The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it will be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, to the extent that the term "comprising" is used in the specification or claims, the term is intended to be encompassed in a manner similar to the term "including", as explained by the use of "including" as a transitional word in the claims. In addition, any use of the term "or" in the specification of the claims is intended to mean a "non-exclusive or".

Claims

1. A downhole isolation tool, characterized in that: The tool comprises an oil pipe body (1), a hydration expansion sealing body (2), a fixed end assembly (3) and a floating end assembly (4); The hydration expansion sealing body (2) is sleeved on the outside of the oil pipe body (1) and extends axially along the oil pipe body (1); The hydration expansion seal (2) can undergo a metal hydration reaction with the well fluid to expand; The fixed end assembly (3) and the floating end assembly (4) are respectively arranged at two ends of the hydration expansion sealing body (2); The floating end assembly (4) is used to limit the oil pipe body (1) in the axial direction and release the limit when the temperature reaches a preset temperature; The fixed end assembly (3) is fixed to the oil pipe body (1) and is used to drive the end of the hydration expansion sealing body (2) to expand radially under the action of hydraulic pressure so as to close to the well wall and complete the sealing.

2. The downhole isolation tool according to claim 1, characterized in that: The material of the hydrated expansion sealing body (2) includes expandable metal and adhesive; The expandable metal is used to undergo a metal hydration reaction with the well fluid to expand; The adhesive is used to react with metal ions in the well fluid to form a gel, so that the expanded hydrated expansion sealing body (2) is tightly bonded to the well wall.

3. The downhole isolation tool according to claim 1, characterized in that: The hydration expansion sealing body (2) is provided with a protective layer on the outside; The protective layer is made of decomposable alloy material; The decomposable alloy material can be decomposed in well fluid with mineralization.

4. The downhole isolation tool according to claim 1, characterized in that: The fixed end assembly (3) includes a fixed component (31), a one-way valve component (32) and an expansion type anti-burst body (34); The fixing assembly (31) is fixed to the oil pipe body (1); The expandable anti-burst body (34) is located between the hydration expansion sealing body (2) and the one-way valve assembly (32); The one-way valve assembly (32) is located in the fixed assembly (31) and is used to pass well fluid into the expandable anti-bumping body (34); The end of the expandable anti-burst body (34) is embedded in the hydration expansion sealing body (2) and can be radially expanded under the action of hydraulic pressure to drive the end of the hydration expansion sealing body (2) to expand radially.

5. The downhole isolation tool according to claim 4, characterized in that: The fixed end assembly (3) further includes a sliding body (33); The sliding body (33) is arranged between the one-way valve assembly (32) and the expansion type anti-burst body (34), and is dynamically sealed with the fixed assembly (31); The sliding body (33) is used to move toward the inside of the expandable anti-blowout body (34) under the drive of well fluid, so as to expand the expandable anti-blowout body (34).

6. The downhole isolation tool according to claim 5, characterized in that: The sliding body (33) includes a cone section (332); The front end portion of the cone section (332) can extend into the expandable anti-outburst body (34) to expand the expandable anti-outburst body (34) in the radial direction.

7. The downhole isolation tool according to claim 6, characterized in that: The sliding body (33) further includes a cylindrical section (331); The cylindrical section (331) is located at the rear end of the cone section and is dynamically sealed to the fixing assembly (31).

8. The downhole isolation tool according to claim 6, characterized in that: The inner side of the expansion type anti-burst body (34) has an inner conical surface adapted to the conical section (332) of the sliding body (33).

9. The downhole isolation tool according to claim 4, characterized in that: The expandable anti-outburst body (34) comprises a plurality of expandable anti-outburst units (341) connected in sequence along the circumferential direction; Each of the expandable anti-burst units (341) has an embedded portion (342) at the end close to the hydrated and expanded sealing body (2), and the embedded portion (342) is embedded in the hydrated and expanded sealing body (2).

10. The downhole isolation tool according to claim 7, characterized in that: The fixing assembly (31) comprises a first limiting ring (311), an intermediate joint (312) and an end joint (313) which are connected in sequence; The first limiting ring (311) is sealedly connected to the oil pipe body (1); The end joint (313) is sealedly connected to the sliding body (33); The first limiting ring (311), the middle joint (312), the end joint (313), the sliding body (33) and the oil pipe body (1) form a sealed cavity (35); The one-way valve assembly (32) is arranged in the sealed cavity (35) and connected to the intermediate joint (312).

11. The downhole isolation tool according to claim 10, characterized in that: The end of the end joint (313) close to the hydration expansion sealing body (2) has an inner conical surface structure (3131) inclined inwardly; The inner conical surface structure (3131) abuts against the conical section of the sliding body (33) and is used to limit the axial movement of the sliding body (33).

12. The downhole isolation tool according to claim 10, characterized in that: The fixed end assembly (3) further includes a filter element (36); The filter element (36) is arranged in the sealing cavity (35) and is located at the inlet of the one-way valve assembly (32).

13. The downhole isolation tool according to claim 1, characterized in that: The floating end assembly (4) includes a positioning ring (41); The oil pipe body (1) is provided with a positioning groove (11); The positioning ring (41) can be embedded in the positioning groove (11) at room temperature to be fixed to the oil pipe body (1), and can be deformed when the external temperature rises to a preset temperature and detached from the positioning groove (11) to float relative to the oil pipe body (1).

14. The downhole isolation tool according to claim 13, characterized in that: The floating end assembly (4) further includes a second limiting ring (42); The second limiting ring (42) is dynamically sealed to the oil pipe body (1); The positioning ring (41) is arranged inside the second limiting ring (42).

15. A downhole isolation method, characterized in that: Using the downhole isolation tool according to any one of claims 1 to 14, the method comprises: Connect the downhole isolation tool to the downhole tubing and run it into the wellbore; The floating end assembly (4) deforms at high temperature to release the limit; After being exposed, the hydration expansion seal (2) undergoes a metal hydration reaction with the well fluid and expands; The wellbore is pressurized to allow well fluid to enter the fixed end assembly (3), and the well fluid drives the end of the hydration expansion seal (2) to expand radially to fit closely against the well wall.

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