A method and device for sealing and isolating the bottom of an old well

Abstract

This invention discloses a method and device for sealing and packing abandoned wells, belonging to the field of oil and gas well abandonment sealing technology. The device includes a central cylinder, a thermoplastic sealing ball, a movable support base for the sealing ball, a telescopic rod, a deformable rubber cylinder, and a connecting valve body. The method includes: lowering the device and then inserting the thermoplastic sealing ball to seal the central flow channel; pumping in high-temperature rubber fluid to generate hydraulic pressure to drive the central cylinder downwards; the downward movement of the central cylinder synchronously compresses the deformable rubber cylinder, causing it to expand radially and conform to the well wall, thus opening the setting channel; the high-temperature rubber fluid enters the annular space formed by the expanded rubber cylinder and the well wall through the setting channel. This invention achieves mechanical setting and thermoplastic material injection through integrated action, utilizing material phase change to form a creep-resistant permanent seal, and forming a two-stage sealing system with the rubber cylinder, fundamentally solving the long-term sealing reliability problem caused by material stress relaxation in traditional packers.

Description

Technical Field

[0001] This invention relates to the field of abandoned well sealing technology, specifically to a method and device for sealing and isolating the bottom of old wells. Background Technology

[0002] In the later stages of oil and gas field development, a large number of old and depleted wells need to be permanently abandoned and sealed in accordance with national regulations and safety and environmental protection requirements. One of the core aspects is to establish a reliable wellbore barrier above the target formation to isolate formation fluids and prevent inter-layer flow or leakage to the surface. Currently, the industry typically uses methods such as injecting cement slurry into the wellbore to form a cement plug, or using mechanical packers in conjunction with sealing materials such as cement and polymers to achieve sealing.

[0003] However, existing technical solutions all have the following shortcomings in achieving "permanent" sealing:

[0004] During the solidification process, cement grout may develop microcracks or fail to bond completely with the casing and wellbore. Under long-term stress changes, thermal cycling, and fluid corrosion, its sealing integrity may deteriorate. Furthermore, cement grout is susceptible to contamination by formation fluids and is prone to channeling within narrow annulus spaces, affecting the sealing quality.

[0005] Conventional packers primarily rely on the radial force generated by the elastic deformation of the rubber sleeve to adhere to the wellbore and achieve a seal. Their sealing pressure originates from the elastic recovery force of the rubber material. However, in the long-term high-temperature, high-pressure, and formation fluid environment downhole, polymer rubber materials inevitably undergo stress relaxation and creep, causing the contact pressure applied to the wellbore to gradually decrease over time, resulting in a decline in sealing performance.

[0006] Some existing improvement solutions employ a "two-step" approach: first, a mechanical packer is set as a temporary barrier or flow diverter, and then sealing material (such as cement or resin) is injected into the annulus above the packer through other channels. This method requires complex pipe string structures, multi-stage control valves, or additional operating steps, which not only increases operating costs and risks but also introduces more potential failure points at the connection and sealing points of various components. Summary of the Invention

[0007] The purpose of this invention is to provide a well bottom sealing device and method for sealing old wells, which solves the technical problem that traditional packers rely on rubber elastic seals and fail due to material stress relaxation during long-term service.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A well-sealing and packing device for old wells includes a central cylinder, a heat-melting sealing ball, a movable support seat for the sealing ball, a telescopic rod, a deformable rubber cylinder, and a connecting valve body;

[0010] A central flow channel is formed inside the central cylinder; the outer diameter of the thermoplastic sealing ball is larger than at least one inner diameter of the central flow channel; a movable support seat for the sealing ball is disposed inside the central cylinder for receiving and positioning the thermoplastic sealing ball; the telescopic rod is slidably and sealingly connected to the central cylinder, and the central cylinder and the telescopic rod together define an annular flow channel for fluid passage; a deformable rubber sleeve is fitted outside the telescopic rod; a setting channel is disposed on the side of the central cylinder, initially closed, and opened when the central cylinder undergoes axial displacement; the connecting valve body is disposed downstream of the telescopic rod for connecting to the lower tubing column;

[0011] When the hot-melt sealing ball blocks the central flow channel, the high-temperature rubber liquid injected into the central flow channel generates hydraulic pressure, driving the central cylinder to move downward relative to the telescopic rod;

[0012] The downward movement of the central cylinder simultaneously performs two actions: compressing the deformable rubber cylinder to expand radially to fit the well wall, and opening the setting channel;

[0013] The high-temperature rubber liquid flows out through the opened setting channel and enters the annular space formed by the expanded deformable rubber cylinder and the well wall.

[0014] Furthermore, it also includes an upper connector; the upper end of the upper connector is provided with an API standard female thread for connecting the upper drill string, and the lower end of the upper connector is connected to the upper end of the center cylinder.

[0015] Furthermore, the movable support seat of the sealing ball is provided with a conical flow channel inside, and the maximum inner diameter of the conical flow channel is smaller than the outer diameter of the thermoplastic sealing ball;

[0016] The device also includes a locking block disposed inside the central cylinder, which is used to limit the movable support seat of the sealing ball in the radial direction.

[0017] Furthermore, the outer wall of the central cylinder is provided with a stepped structure for installing springs or limiting components; the upper end of the central cylinder is positioned with the upper connector through a shoulder structure, and the lower end of the central cylinder extends into the telescopic rod and forms a sliding sealing pair with the telescopic rod.

[0018] Furthermore, the upper inner wall of the telescopic rod forms a sliding seal connection with the outer wall of the central cylinder; the lower end of the telescopic rod is provided with a quick-connect male head, which is used to insert into the quick-connect female head of the connecting valve body and form a seal.

[0019] Furthermore, the connecting valve body is a quick-connect female connector; the connecting valve body is equipped with a locking mechanism and a sealing ring inside, which are used to achieve quick connection and sealing with the quick-connect male connector at the lower end of the telescopic rod.

[0020] Furthermore, it also includes a support cylinder; the support cylinder is a rigid cylinder, sleeved outside the telescopic rod and located inside the deformable rubber cylinder; the melting point of the material of the deformable rubber cylinder is higher than the melting point of the high-temperature rubber liquid.

[0021] Furthermore, the locking block is a wedge-shaped block; the locking block is configured to release the restriction on the movable support seat of the sealing ball when the central cylinder moves downward to a predetermined position.

[0022] Furthermore, it also includes springs;

[0023] The spring is sleeved on the outside of the central cylinder;

[0024] The upper and lower ends of the spring are respectively limited by the stepped structure and the upper shell;

[0025] The spring is used to provide an elastic force to reset the central cylinder after the thermoplastic sealing ball is melted.

[0026] In addition, the present invention also discloses a method for sealing the bottom of an old well, including the use of an old well sealing device as described above, comprising the following steps:

[0027] S1: Lower the well bottom sealing and packing device for sealing old wells as described above to the predetermined position at the bottom of the well;

[0028] S2: Insert a thermoplastic sealing ball into the central flow channel of the device from the wellhead, so that the thermoplastic sealing ball sits on the movable support seat of the sealing ball, thereby sealing the central flow channel;

[0029] S3: High-temperature rubber liquid is pumped into the blocked central flow channel, and the hydraulic pressure generated by the high-temperature rubber liquid pushes the central cylinder downward;

[0030] S4: The downward movement of the central cylinder is executed synchronously:

[0031] a. Compress the deformable rubber cylinder to cause it to expand radially until it fits against the well wall, forming an initial mechanical seal;

[0032] b. Open the sealing passage;

[0033] S5: The high-temperature rubber liquid flows out through the opened setting channel and enters the annular space formed by the expanded deformable rubber cylinder and the well wall;

[0034] S6: The heat from the high-temperature rubber liquid dissolves the heat-melting sealing ball, restoring the unobstructed flow of the central channel;

[0035] S7: The high-temperature rubber liquid cools and solidifies within the annular space to form a solid sealing section;

[0036] The solid sealing section and the deformable rubber cylinder together form a double-stage seal.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] This invention introduces a high-temperature rubber liquid solidified into a solid sealing section as the final plugging body. This material transforms from a liquid state to a solid state downhole. The resulting solid sealing section does not possess the creep characteristics unique to polymer elastomers; its sealing ability relies on the structural strength of the solid material itself and its adhesion to the wellbore, ensuring long-term stability of the sealing effect and making it suitable for engineering requirements requiring permanent plugging.

[0039] This invention integrates two key steps—the mechanical setting of a deformable rubber cylinder to form the initial seal and the injection of high-temperature rubber fluid to form a solid sealing section—into a continuous and automated process. The high-temperature rubber fluid simultaneously serves as the hydraulic medium driving the central cylinder downwards, the solvent dissolving the thermoplastic plugging ball, and the final plugging material, eliminating the need for additional hydraulic control lines or complex multi-stage valve systems. By leveraging the integrated opening and injection process of the setting channel, it significantly reduces the number of operational steps and potential failure points in downhole tools, lowers operational complexity, and makes the plugging process more coherent and controllable.

[0040] This invention constructs a redundant two-stage sealing system consisting of a deformable rubber cylinder and a solid sealing section, enhancing overall sealing reliability. It forms a dual physical and material barrier: the first stage is a mechanical compression seal provided by the deformable rubber cylinder, and the second stage is a rigid filling seal formed by the solidification of high-temperature rubber liquid. The failure mechanisms of the two stages of sealing are different (stress relaxation in the first stage, and material failure in the second stage), greatly reducing the probability of simultaneous failure. Even after long-term service, although the elasticity of the deformable rubber cylinder may decrease, the internal solid sealing section can still independently provide a reliable sealing effect, forming an effective safety redundancy.

[0041] The solid sealing section ultimately formed by this invention originates from a flowable, injectable high-temperature rubber fluid. Its ability to fill and fit irregular well walls (such as corroded casing or open hole walls) is far superior to that of mechanical seals that rely solely on the deformation of deformable rubber cylinders. It can effectively seal micro-gap and micro-holes, improving the sealing success rate under harsh well conditions.

[0042] The present invention can also achieve closed-loop stable pressure control during the annular space filling stage through a matching intelligent control system, and estimate the curing state of the sealing body based on real-time temperature monitoring and curing model, thereby achieving more accurate process control and endpoint judgment, and further improving the reliability and success rate of sealing operations. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 A schematic diagram of the overall structure of the present invention.

[0045] Figure 2 For the present invention Figure 1 A magnified view of a portion of point A in the middle.

[0046] Figure 3 For the present invention Figure 1 A magnified view of a portion of point B in the middle.

[0047] Figure 4 This is an overall flowchart of the method described in this invention.

[0048] Figure label:

[0049] 1-Upper connector, 2-Positive support for the plugging ball, 3-Locking block, 4-Thermo-melting plugging ball, 5-Upper housing, 6-Central cylinder, 7-Telescopic rod, 8-Support cylinder, 9-Deformable rubber cylinder, 10-Lower housing, 11-Connecting valve body, 12-Lower connector. Detailed Implementation

[0050] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0051] In the description of the embodiments of the present invention, it should be understood that the terms "length", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0053] In this embodiment of the invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment of the invention according to the specific circumstances.

[0054] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0055] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0056] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0057] Example 1: See Figures 1-4 This embodiment discloses an old well sealing and packing device, which mainly includes an upper connector 1, a sealing ball movable support seat 2, a locking block 3, a thermoplastic sealing ball 4, an upper shell 5, a central cylinder 6, a telescopic rod 7, a support cylinder 8, a deformable rubber cylinder 9, a lower shell 10, a connecting valve body 11, and a lower connector 12.

[0058] The upper end of the upper connector 1 is machined with a female thread conforming to API standards for connection with the upper drill string or working string. The lower end of the upper connector 1 is connected to the upper housing 5 via a thread or shoulder structure. The upper end of the central cylinder 6 is positioned within the upper connector 1 or the upper housing 5 via a shoulder and can move axially up and down. A central flow channel running vertically is formed inside the central cylinder 6. The movable support seat 2 for the plugging ball is installed in the upper inner cavity of the central cylinder 6, and its interior is machined with a tapered flow channel whose inner diameter gradually decreases from top to bottom. The locking block 3, in this embodiment, consists of two or more wedge-shaped blocks arranged circumferentially and installed in a groove on the inner wall of the central cylinder 6. It is used to limit the movable support seat 2 for the plugging ball from the radial inside in the initial state, preventing it from falling.

[0059] Furthermore, the upper inner hole of the telescopic rod 7 is fitted with the lower outer wall of the central cylinder 6 in a clearance fit, and at least one sealing ring (such as an O-ring) is provided between them to form a sliding sealing pair. This allows the central cylinder 6 to slide up and down within the telescopic rod 7 while maintaining a seal. The telescopic rod 7, the central cylinder 6, and the annular space between them together constitute an annular flow channel for the fluid. The lower end of the telescopic rod 7 is machined into a quick-connect male head. The upper end of the connecting valve body 11 is correspondingly machined into a quick-connect female head, which contains a locking steel ball, a spring, and a sealing ring to form a quick-connect self-locking sealing joint. When the quick-connect male head at the lower end of the telescopic rod 7 is inserted into the quick-connect female head of the connecting valve body 11 and reaches the predetermined position, the locking mechanism is activated to lock it, and the sealing ring achieves high-pressure sealing. The lower end of the connecting valve body 11 is connected to the lower tubular column (such as a guide shoe, screen pipe, etc.) through the lower connector 12, which is usually an API standard male thread.

[0060] The deformable rubber cylinder 9 is sleeved around the middle periphery of the telescopic rod 7. Inside the deformable rubber cylinder 9, a rigid support cylinder 8 is sleeved on the telescopic rod 7. The support cylinder 8 is a metal cylinder with an outer diameter smaller than the inner diameter of the deformable rubber cylinder 9. When the deformable rubber cylinder 9 is subjected to axial compression, the rubber material mainly expands and deforms in the radial direction due to the constraint of the rigid support cylinder 8 inside. The deformable rubber cylinder 9 is made of high-temperature resistant rubber material, and its heat resistance temperature or softening point is significantly higher than the melting temperature of the subsequently injected high-temperature rubber liquid to ensure that it will not soften and fail during the injection process. The upper shell 5, the central cylinder 6, the lower shell 10, and other components form an annular cavity, in which the deformable rubber cylinder 9 is located.

[0061] At least one radial through hole is provided on the upper side wall of the central cylinder 6. This through hole is initially closed under the cover of the inner wall of the upper housing 5. This through hole is the outlet of the setting channel. Only when the central cylinder 6 moves downward relative to the upper housing 5 by a certain distance can the through hole be exposed beyond the cover of the upper housing 5, thereby opening the setting channel.

[0062] The setting channel includes at least one radial injection hole on the side wall of the central cylinder 6, and an annular flow channel formed by the inner wall of the upper shell 5 and the outer wall of the central cylinder 6. In the initial state, the radial injection hole is covered by the inner wall of the upper shell 5. When the central cylinder 6 is hydraulically driven to move downward to a predetermined position, the radial injection hole moves down to a position connected with the annular flow channel, thereby opening the setting channel and allowing the high-temperature rubber liquid to enter the outer annular space from the central flow channel through the radial injection hole and the annular flow channel.

[0063] As an alternative implementation, the opening of the setting channel can be controlled by a hydraulically operated slide valve. This slide valve is integrated within the upper housing 5, and its valve core is connected to the central cylinder 6 via a connecting rod. When the central cylinder 6 moves downward a predetermined distance, it drives the connecting rod, which in turn pushes the valve core, opening the flow channel connecting the central flow channel and the annular space.

[0064] This embodiment also discloses a method for sealing and isolating the bottom of an old well, including the following steps:

[0065] S1: Ground assembly.

[0066] Surface assembly and downhole deployment. Assemble the components as needed. Figure 1 Connect the components in the sequence shown. First, ensure that the locking block 3 locks the movable support seat 2 of the plugging ball. Then, insert the quick-connect male end of the telescopic rod 7 into the quick-connect female end connecting the valve body 11 until the locking mechanism actuates and forms a seal, completing the overall assembly of the device. Finally, lower the assembled device to the predetermined location at the bottom of the well (e.g., above the producing formation) using the drill string.

[0067] S2: Shot block.

[0068] A thermoplastic plugging ball 4 is inserted into the wellhead through the drill string borehole. The thermoplastic plugging ball 4 falls with the drilling fluid and eventually settles within the conical flow channel of the plugging ball movable support 2. Because the outer diameter of the thermoplastic plugging ball 4 is larger than the minimum inner diameter of the conical flow channel, the central flow channel is effectively sealed.

[0069] S3: Pump injection pressurization.

[0070] Preheated high-temperature rubber liquid is pumped into the sealed central flow channel through a drill string. The high-temperature rubber liquid is a thermoplastic sealing composite material, composed of, by weight, 40-60 parts of a thermoplastic elastomer substrate (such as styrene-isoprene-styrene block copolymer SIS), 30-50 parts of a tackifying resin (such as C5 petroleum resin), 10-20 parts of a plasticizer (such as naphthenic oil), and 1-3 parts of a stabilizer. The material has a melting temperature range of 140°C to 180°C, and a melt viscosity below 5000 cP within this temperature range. After curing (at 25°C and normal pressure), its Shore hardness A is not less than 70, its compressive strength is not less than 5 MPa, and its bond strength to N80 grade steel sheet is not less than 2 MPa.

[0071] Optionally, in step S3, before pumping in the high-temperature rubber liquid, a section of clean water or low-viscosity oil-based separator at a temperature of 100°C to 140°C can be pumped in first to clean the flow channel and preheat the inside of the tool, ensuring that the heat-melting sealing ball can be dissolved more efficiently.

[0072] S4: Sealing and opening the passage.

[0073] The increased hydraulic pressure acts on the cross-section of the sealing ball movable support 2 and the central cylinder 6, generating a downward axial force. This force overcomes initial resistance (such as the friction of the sealing ring) and pushes the central cylinder 6 downward relative to the stationary telescopic rod 7 and the upper housing 5. The downward movement of the central cylinder 6 simultaneously performs two key actions:

[0074] a) Compression of the rubber cylinder: The lower end of the central cylinder 6 pushes or compresses the deformable rubber cylinder 9 through other transmission structures (such as the lower housing 10). Under axial compression and radial restriction by the rigid support cylinder 8, the deformable rubber cylinder 9 undergoes significant radial expansion until its outer surface tightly adheres to the well wall or the inner wall of the casing, forming an initial mechanical seal ring and dividing the wellbore annulus into upper and lower independent spaces.

[0075] b) Opening the setting channel: After the center cylinder 6 moves down to the predetermined stroke, the radial through hole (setting channel outlet) on its side wall is completely moved out of the shielding area of ​​the upper housing 5, and the setting channel is opened.

[0076] S5: Glue injection and filling.

[0077] The high-temperature rubber fluid immediately flows out laterally from the central flow channel through the opened setting seal channel and enters the upper annular space surrounded by the expanded deformable rubber cylinder 9, well wall (or casing), upper shell and lower shell, etc.

[0078] S6: Continuous glue injection and dissolution of spheres.

[0079] During the continuous pumping of high-temperature rubber liquid, allowing it to fully enter and fill the annular space through the sealing channel, the heat-melting sealing ball 4 is made of low-density polyethylene (LDPE) or polycaprolactone (PCL), with a melting point of 90°C to 130°C. Under the action of the high-temperature rubber liquid (temperature ≥150°C) pumped in step S3, the heat-melting sealing ball 4 can completely soften and dissolve within 5 to 15 minutes.

[0080] S7: Complete the injection and curing seal.

[0081] Complete the injection and curing seal. Continuously pump high-temperature rubber fluid until it fills the annular space, judging by the pumping pressure or volume. When the thermoplastic sealing ball 4 is completely dissolved by the high temperature, the central flow channel is restored to unobstructed flow. At this point, pumping can be stopped. The high-temperature rubber fluid filling the annular space dissipates heat, cools, and eventually completely solidifies in the wellbore environment, forming a hard, solid seal section that tightly bonds to the wellbore wall and the outer wall of the tool. This solid seal section, together with the elastic sealing ring composed of the deformable rubber cylinder 9 below, forms a reliable "double-stage sealing" barrier, achieving permanent isolation of the well bottom.

[0082] The working principle of this invention is based on thermodynamics and fluid mechanics, achieving permanent sealing through material phase change. To achieve this, the materials must meet specific temperature relationships: the temperature T2 of the pumped high-temperature rubber liquid must be higher than the melting point T1 of the thermoplastic sealing ball to ensure its dissolution; simultaneously, T1 must be higher than the temperature T3 of the target downhole containment layer to prevent the sealing ball from softening prematurely before setting. Furthermore, the temperature resistance threshold T4 of the deformable rubber sleeve material must be higher than T2 to ensure structural integrity during the injection process. That is, the pumping temperature of the high-temperature rubber liquid must be higher than the melting point of the thermoplastic sealing ball, and the melting point of the thermoplastic sealing ball must be higher than the temperature of the target downhole containment layer; simultaneously, the heat resistance temperature of the deformable rubber sleeve material must be higher than the pumping temperature of the high-temperature rubber liquid.

[0083] To ensure the sealing process proceeds sequentially and forms a reliable seal, the materials of the high-temperature rubber fluid, the thermoplastic sealing ball, and the deformable rubber sleeve must meet specific temperature matching requirements: the pumping temperature of the high-temperature rubber fluid should be higher than the melting point of the thermoplastic sealing ball; the melting point of the thermoplastic sealing ball should be higher than the temperature of the target downhole containment layer. The material used for the deformable rubber sleeve should have a short-term operating temperature not lower than the pumping temperature of the high-temperature rubber fluid to ensure structural integrity during the injection process; its long-term operating temperature should be adapted to the ambient temperature of the target downhole containment layer.

[0084] Example 2: Based on Example 1, this example further discloses an optimized scheme including a return spring and a locking block release mechanism to more accurately control the setting process and may reset the central cylinder portion to improve the shape of the sealing section.

[0085] The device structure in this embodiment is mostly the same as that in Embodiment 1, with the main difference being:

[0086] Spring reset mechanism:

[0087] A helical compression spring is fitted inside the upper shell 5 and outside the central cylinder 6. The upper end of the spring rests against a spring seat formed by the inner step of the upper shell 5, and the lower end rests against the stepped structure (shoulder) on the outer wall of the central cylinder 6. In the initial state, the spring is in a pre-compressed or free state. When the central cylinder 6 moves downward under hydraulic pressure, the spring is further compressed, storing elastic potential energy.

[0088] Release structure of the locking block: The mounting groove of the locking block 3 is designed with a guide slope. The inner wall of the central cylinder 6 has a release groove corresponding to the position of the locking block 3. When the central cylinder 6 moves downward to a specific position, the outer slope of the locking block 3 contacts the edge of the release groove on the inner wall of the central cylinder 6. Under the action of the radial component force, the locking block 3 is forced to retract radially inward towards the central cylinder 6, thereby releasing the radial restriction on the movable support seat 2 of the sealing ball.

[0089] The working method of this embodiment is basically the same as that of Embodiment 1 in steps S1 to S5. The difference lies in step S6 and beyond:

[0090] S601: Dissolves the ball, releases the locking mechanism, and resets the spring. High-temperature rubber melt dissolves the thermoplastic sealing ball 4, releasing pressure in the central flow channel.

[0091] Simultaneously, since the central cylinder 6 has moved down to a specific position, the locking block 3 is automatically released, and the sealing ball movable support seat 2 is no longer limited. At this time, the main downward hydraulic pressure acting on the central cylinder 6 has disappeared, and the elastic restoring force of the compressed spring below becomes dominant. Under the action of the spring force, the central cylinder 6 is pushed upward a small distance (partial reset).

[0092] The primary function of the spring is to provide force feedback and safety redundancy during the setting process. When the thermoplastic sealing ball 4 melts and the central flow channel depressurizes, the spring's restoring force helps maintain the compressed state of the deformable rubber cylinder 9, compensating for any transient, minute creep that may occur at high temperatures. The upward reset tendency of the central cylinder 6 is limited by the gradually thickening high-temperature rubber liquid within the annular space, resulting in a very small actual displacement. To ensure that the curing process of the material within the annular space is not interfered with, the radial injection hole's flow section is not closed due to the minute displacement of the central cylinder 6 after the setting channel is fully opened.

[0093] S602: Curing forms a permanent seal. This step is the same as S7 in Example 1. Finally, a two-stage seal is formed, consisting of a solid sealing section and a deformable rubber sleeve 9. The introduction of a spring reset mechanism makes the termination of the setting process more proactive and controllable.

[0094] Example 3: Based on the device described in Example 1 or 2, this example further illustrates a compatible intelligent control system, which includes:

[0095] The downhole sensing unit, integrated into the packer, includes at least:

[0096] A temperature sensor is installed on the outer wall of the lower housing to monitor the temperature of the sealing material within the annular space in real time. ;

[0097] A pressure sensor, disposed within the upper housing and communicating with the annular space downstream of the setting channel, is used to monitor the pressure of the annular space in real time. ;

[0098] A surface control unit, communicatively connected to the downhole sensing unit and connected to the surface pumping equipment, includes:

[0099] The pressure control module is configured to use the pressure of the annular space. To provide feedback, adjust the surface pump discharge rate. ,make Maintain within the preset range;

[0100] The curing monitoring module is configured to monitor the curing temperature. Estimate the degree of curing of the sealing material and in A signal is emitted when the preset threshold is reached.

[0101] The curing monitoring module uses the following formula to iteratively estimate the degree of curing:

[0102] ;

[0103] in, The iteration number; and These represent the degree of solidification at the current and previous moments, respectively. Pre-exponential factors; It is the activation energy; It is the ideal gas constant; The current temperature; The reaction order is [number]. For time step.

[0104] The pressure control module uses the following control law to regulate the displacement:

[0105] ;

[0106] in, This is the initial displacement; For pressure deviation; Preset pressure value; and This is the control factor.

[0107] The intelligent control system includes the following steps:

[0108] 1) After the high-temperature rubber liquid enters the annular space through the setting channel, the intelligent control system is activated;

[0109] 2) The pressure control module starts working, adjusting the ground pump injection rate in real time. This causes the annular space pressure Stable within the preset range Inside;

[0110] 3) Simultaneously, the curing monitoring module, based on the temperature measured by the temperature sensor... The real-time curing degree of the sealing material is estimated iteratively according to formula (1). ;

[0111] 4) When the curing monitoring module determines Reaching the preset curing completion threshold When the pressure in the annular space remains stable, the system determines that the sealing body has solidified and issues a signal to stop pumping.

[0112] In practice:

[0113] 1. The system is structured as follows:

[0114] Temperature sensor: An armored K-type thermocouple is installed on the outer wall of the lower housing 10 to monitor the temperature of the annular space. .

[0115] Pressure sensor: A sputtered thin-film pressure sensor is used, which is connected to the annular space downstream of the setting channel through the pressure guide hole on the side wall of the upper housing 5, for monitoring pressure. .

[0116] Signal transmission: Sensor signals are uploaded to the ground via the Measurement While Drilling (MWD) system.

[0117] Ground control unit: Based on programmable logic controller (PLC), it receives sensor data and controls the pumping equipment.

[0118] 2. Parameter settings are as follows:

[0119] Pressure control range set to , To preset the lower limit of pressure, To preset the upper pressure limit, control coefficient .

[0120] The curing model parameters were obtained through standard testing methods: differential scanning calorimetry (DSC) was performed on the high-temperature rubber liquid described in Example 1, and the non-isothermal DSC curves were fitted using the Kissinger method or the Ozawa method to obtain the pre-exponential factor. ,activation energy and reaction order Typical values, for example: , .

[0121] 3. The control process is as follows:

[0122] After the device is set and sealed, the intelligent control system is activated.

[0123] Pressure control: Real-time monitoring ,according to Dynamically adjust displacement ,make Stable at Within the range.

[0124] Solidification monitoring and calculation example: Setting the iteration step size Each interval Read the temperature once And iteratively calculate the degree of curing. For example, when the temperature is measured in a certain iteration And the solidification degree of the previous iteration cycle At that time, calculate the current degree of cure increment. : , The current cumulative degree of curing .

[0125] Endpoint Judgment: When When the pressure stabilizes, the system indicates that curing is complete.

[0126] The intelligent control system integrated in this embodiment combines real-time process monitoring, closed-loop feedback control, and material curing state prediction to construct a quantifiable and controllable intelligent operation process. The downhole sensing unit continuously collects real-time pressure and temperature data of the annular space and uploads it to the surface control unit. Based on this pressure data, the pressure control module in the surface control unit dynamically adjusts the pumping rate of the high-temperature rubber fluid, ensuring that the fluid pressure within the annular space remains within a preset optimal range. This guarantees that the high-temperature rubber fluid can uniformly and densely fill the entire annular space, preventing voids due to insufficient pressure and avoiding damage to the wellbore or tools due to excessive pressure.

[0127] Meanwhile, the curing monitoring module, based on real-time temperature data, drives the built-in curing kinetics model to continuously calculate and evaluate the curing process of the high-temperature rubber liquid. This model simulates the curing reaction of materials at specific temperatures, transforming the history of temperature changes into a quantitative judgment of the material's internal strength development. This allows for the scientific prediction of when the sealing material will reach the predetermined curing strength, rather than relying on empirically fixed waiting times.

[0128] Precise and stable pressure control ensures a uniform and dense internal structure of the final solid seal section, fundamentally improving seal integrity. The model-determined curing completion point provides objective and reliable time data for subsequent operations, significantly reducing the risk of seal failure due to premature disturbance. Recording and tracing key parameters throughout the process not only improves the success rate and quality consistency of individual operations but also provides a data foundation for process optimization and standardization. This process control enhances the reliability and sophistication of the entire technical solution, providing crucial intelligent assurance for achieving truly long-term reliable sealing.

[0129] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A well-sealing and packing device for old wells, characterized in that, It includes a central cylinder, a heat-melting plugging ball, a movable support seat for the plugging ball, a telescopic rod, a deformable rubber cylinder, and a connecting valve body; A central flow channel is formed inside the central cylinder; the outer diameter of the thermoplastic sealing ball is larger than at least one inner diameter of the central flow channel; the movable support seat of the sealing ball is disposed inside the central cylinder for receiving and positioning the thermoplastic sealing ball; the telescopic rod is slidably and sealingly connected to the central cylinder, and the central cylinder and the telescopic rod together define an annular flow channel for fluid passage; the deformable rubber sleeve is sleeved on the outside of the telescopic rod; The setting channel is located on the side of the central cylinder, and is initially closed and opened when the central cylinder undergoes axial displacement; the connecting valve body is located downstream of the telescopic rod and is used to connect to the lower tubular column. When the hot-melt sealing ball blocks the central flow channel, the high-temperature rubber liquid injected into the central flow channel generates hydraulic pressure, driving the central cylinder to move downward relative to the telescopic rod; The downward movement of the central cylinder simultaneously performs two actions: compressing the deformable rubber cylinder to expand radially to fit the well wall, and opening the setting channel; The high-temperature rubber liquid flows out through the opened setting channel and enters the annular space formed by the expanded deformable rubber cylinder and the well wall.

2. The well bottom sealing and packing device for old wells according to claim 1, characterized in that, It also includes an upper connector; the upper end of the upper connector is provided with an API standard female thread for connecting the upper drill string, and the lower end of the upper connector is connected to the upper end of the center cylinder.

3. A well-sealing and bottom-sealing device for sealing old wells according to claim 1 or 2, characterized in that, The movable support seat of the plugging ball has a conical flow channel inside, and the maximum inner diameter of the conical flow channel is smaller than the outer diameter of the thermoplastic plugging ball; The device also includes a locking block disposed inside the central cylinder, which is used to limit the movable support seat of the sealing ball in the radial direction.

4. The well bottom sealing and packing device for sealing old wells according to claim 1, characterized in that, The outer wall of the central cylinder is provided with a stepped structure for installing springs or limiting components; the upper end of the central cylinder is positioned with the upper connector through a shoulder structure, and the lower end of the central cylinder extends into the telescopic rod and forms a sliding sealing pair with the telescopic rod.

5. The well bottom sealing and packing device for old wells according to claim 1, characterized in that, The upper inner wall of the telescopic rod forms a sliding seal connection with the outer wall of the central cylinder; the lower end of the telescopic rod is provided with a quick-connect male head, which is used to insert into the quick-connect female head of the connecting valve body and form a seal.

6. A well-sealing and bottom-sealing device for sealing old wells according to claim 1 or 5, characterized in that, The connecting valve body is a quick-connect female connector; the connecting valve body is equipped with a locking mechanism and a sealing ring inside, which are used to achieve quick connection and sealing with the quick-connect male connector at the lower end of the telescopic rod.

7. The well bottom sealing and packing device for old wells according to claim 1, characterized in that, It also includes a support cylinder; the support cylinder is a rigid cylinder, sleeved outside the telescopic rod and located inside the deformable rubber cylinder; the melting point of the material of the deformable rubber cylinder is higher than the melting point of the high-temperature rubber liquid.

8. The well bottom sealing and packing device for old wells according to claim 3, characterized in that, The locking block is a wedge-shaped block; the locking block is configured to release the restriction on the movable support seat of the sealing ball when the central cylinder moves downward to a predetermined position.

9. A well-sealing and bottom-sealing device for sealing old wells according to claim 4, characterized in that, It also includes springs; The spring is sleeved on the outside of the central cylinder; The upper and lower ends of the spring are respectively limited by the stepped structure and the upper shell; The spring is used to provide an elastic force to reset the central cylinder after the thermoplastic sealing ball is melted.

10. A method for sealing the bottom of an old well, comprising using a bottom sealing device for sealing an old well as described in any one of claims 1-9, characterized in that, Includes the following steps: S1: Lower the old well sealing and packing device to the predetermined position at the bottom of the well; S2: Insert a thermoplastic sealing ball into the central flow channel of the device from the wellhead, so that the thermoplastic sealing ball sits on the movable support seat of the sealing ball, thereby sealing the central flow channel; S3: High-temperature rubber liquid is pumped into the blocked central flow channel, and the hydraulic pressure generated by the high-temperature rubber liquid pushes the central cylinder downward; S4: The downward movement of the central cylinder is executed synchronously: a. Compress the deformable rubber cylinder to cause it to expand radially until it fits against the well wall, forming an initial mechanical seal; b. Open the sealing passage; S5: The high-temperature rubber liquid flows out through the opened setting channel and enters the annular space formed by the expanded deformable rubber cylinder and the well wall; S6: The heat from the high-temperature rubber liquid dissolves the heat-melting sealing ball, restoring the unobstructed flow of the central channel; S7: The high-temperature rubber liquid cools and solidifies within the annular space to form a solid sealing section; The solid sealing section and the deformable rubber cylinder together form a double-stage seal.

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