Dissolvable bridge plug with multi-section dissolving function for oil and gas well

Abstract

The invention discloses a dissolvable bridge plug with a multi-section dissolving function for an oil and gas well, comprising: a main body unit, which comprises a bridge plug main body and a connector fixedly connected to one end of the bridge plug main body, and a ball groove is formed in the connector; the ascending extrusion unit and the rotation acceleration unit are linked, so that when the whole equipment is put into an oil and gas well and reaches a preset position, a conical head is driven to rotate in a recycling mode through a thread shearing releasing tool, then the whole structure of the outer surface of a bridge plug body rotates and ascends, and a sliding plate further moves in a sliding groove; further, when the transition isolation layer ascends to extrude one side of the rapid dissolving layer, the inclined plane on one side of the rapid dissolving layer is utilized to extrude the sealing rubber ring, so that the sealing rubber ring is expanded and stretched outwards, and the sealing rubber ring and the inner surface of the oil and gas well are fully extruded and fixed; and the interior of the oil and gas well is plugged through the rubber sealing ring and the sealing rubber ring.

Description

Technical Field

[0001] The present invention relates to the technical field of dissolvable bridge plug structures, and particularly to a dissolvable bridge plug for oil and gas wells with a multi-stage dissolving function. Background Art

[0002] In the exploration and exploitation of oil fields, a temporary plugging process is required to plug the current production layer, so as to facilitate the exploitation of other production layers. After the process is completed, the temporary plugging is removed, and a flow channel between the production layer and the wellbore is established to realize the oil and gas production of oil and gas wells.

[0003] Existing dissolvable bridge plugs mostly use a single soluble material (such as magnesium alloy), and its dissolution rate is significantly affected by the composition of downhole fluids and temperature fluctuations. It is difficult to achieve staged dissolution control, and premature dissolution (sealing failure) or delayed residue (hindering oil production) is likely to occur. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions shall not be used to limit the scope of the present invention.

[0005] In view of the problems existing in the above-mentioned existing dissolvable bridge plugs for oil and gas wells with a multi-stage dissolving function, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to provide a dissolvable bridge plug for oil and gas wells with a multi-stage dissolving function, which is suitable for solving the problems of difficult staged dissolution control, premature dissolution or delayed residue.

[0007] To solve the above technical problems, the present invention provides the following technical solution: a dissolvable bridge plug for oil and gas wells with a multi-stage dissolving function, the dissolvable bridge plug comprising:

[0008] A main body unit, which includes a bridge plug main body and a connection head fixedly connected to one end of the bridge plug main body. A ball groove is formed in the connection head, and a connection ring is inserted and connected in the connection head;

[0009] A rising extrusion unit, which includes a quick-dissolving layer sleeved on the outer surface of the bridge plug main body and a connection ring fixedly connected to the upper surface of the quick-dissolving layer. A sliding groove is formed in the quick-dissolving layer, a triangular lifting plate is fixedly connected in the sliding groove, a sliding plate is slidably connected in the sliding groove, and an extrusion tooth plate is fixedly connected to one side of the sliding plate;

[0010] A rotation acceleration unit, which includes a rotating ring rotatably connected inside a bridge plug body and a connecting plate fixedly connected to the inner surface of the rotating ring. A blade is fixedly connected to the lower surface of the connecting plate, a fixing plate is rotatably connected to the lower surface of the blade, a rubber sealing ring is slidably connected to the outer side of the lower surface of the bridge plug body, and a tooth groove is formed on the outer surface of the rubber sealing ring.

[0011] As a preferred embodiment of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function of the present invention, wherein: a transition isolation layer is sleeved on the outer surface of the bridge plug body, a delayed dissolution layer is fixedly connected to the outer surface of the bridge plug body, a hydrophobic film is plated on the outer surface of the delayed dissolution layer, the rapid dissolution layer is made of soluble magnesium alloy, and the transition isolation layer is a ring-shaped PLA material.

[0012] As a preferred embodiment of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function of the present invention, wherein: the delayed dissolution layer is made of zinc-aluminum alloy material, both the transition isolation layer and the delayed dissolution layer can slide on the outer surface of the bridge plug body, and the side of the sliding plate away from the extrusion tooth plate is fixedly connected to the transition isolation layer.

[0013] As a preferred embodiment of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function of the present invention, wherein: a sealing rubber ring is fixedly connected to the outer surface of the transition isolation layer, the side of the transition isolation layer away from the rapid dissolution layer is fixedly connected to the delayed dissolution layer, sliding blocks are fixedly connected to both sides of the sliding plate, and the outer surface of the sliding block is slidably connected to the inner surface of the sliding groove.

[0014] As a preferred embodiment of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function of the present invention, wherein: a tapered head is fixedly connected to one side of the rubber sealing ring, a communication groove is formed in the fixing plate, an adapter ring is fixedly connected to the outer surface of the fixing plate, a T-shaped ring is fixedly connected to the lower surface of the adapter ring, and an insertion groove is formed in the tapered head.

[0015] As a preferred embodiment of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function of the present invention, wherein: the inclined planes are provided on the sides of the transition isolation layer and the rapid dissolution layer close to each other, and the inclined plane on the upper surface of the transition isolation layer can be in fitting contact with the inclined plane on one side of the rapid dissolution layer.

[0016] The beneficial effects of the present invention:

[0017] 1. The bridge plug is dissolved in stages by using the transition isolation layer, fast dissolving layer and delayed dissolving layer through the difference in dissolving rates of different materials. The initial fast dissolving layer provides the initial sealing pressure, and the delayed dissolving layer prolongs the stability of the overall structure to avoid premature failure. At the same time, the transition isolation layer delays liquid penetration through the hydrophobic membrane, further controls the dissolution sequence, and adapts to the complex downhole environment, thereby reducing the risk of bridge plug residue, eliminating the need for drilling and milling operations, saving costs, and making the material combination take into account both strength and solubility to meet environmental protection requirements;

[0018] 2. The ascending extrusion unit is linked with the rotation acceleration unit, so that when the whole device is placed in the oil and gas well and reaches the predetermined position, the threaded shearing release drives the conical head to be recovered and rotated, so that the structure of the outer surface of the bridge plug body is rotated and ascended as a whole, and the sliding plate is further moved in the sliding groove, so as to drive the extrusion tooth plate to slide out of the fast dissolving layer, so that it is fully engaged with the inner surface of the oil and gas well. Furthermore, the rubber sealing ring is squeezed by the conical head during the ascending process, and according to its outwardly protruding structure, when it is squeezed, the tooth groove on the outer surface of the rubber sealing ring is fully squeezed and contacted with the inner surface of the oil and gas well, and at the same time, the fixing plate is used to engage the connector provided inside the conical head, so that the device prevents the rubber sealing ring from loosening to a certain extent. Further, when the transition isolation layer rises and squeezes one side of the fast dissolving layer, the inclined plane on one side of the fast dissolving layer is used to squeeze the sealing rubber ring, so that it is expanded and stretched outward, and is fully squeezed and fixed with the inner surface of the oil and gas well, and then the inside of the oil and gas well is blocked by the rubber sealing ring and the sealing rubber ring;

[0019] 3. Using T-rings, connecting rings, rotating rings, fixed plates, connecting plates, and blades, the downhole fluid drives the blades to rotate, driving the rotating ring and connecting ring to move, accelerating the exposure and dissolution of the delayed dissolution layer, and then using fluid power to assist in accelerating the dissolution and reducing the post-operation processing time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0021] Figure 1 This is a schematic diagram of the overall structure of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function proposed by the present invention;

[0022] Figure 2 This is a schematic diagram of the overall cross-sectional structure of a dissolvable bridge plug for oil and gas wells with a multi-stage dissolution function proposed by the present invention;

[0023] Figure 3 Schematic diagram of the blade distribution structure of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function proposed by the present invention;

[0024] Figure 4 Schematic diagram of the sliding plate distribution structure of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function proposed by the present invention;

[0025] Figure 5 Schematic diagram of the rotational acceleration unit structure of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function proposed by the present invention;

[0026] Figure 6 Schematic diagram of the rising extrusion unit structure of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function proposed by the present invention;

[0027] Figure 7 Schematic diagram of the internal structure of the rotating ring of the dissolvable bridge plug for oil and gas wells with multi-stage dissolution function proposed by the present invention. Description of the drawings: 100, main body unit; 101, bridge plug main body; 102, connecting head; 103, ball groove; 104, connecting ring; 200, rising extrusion unit; 201, transition isolation layer; 202, sealing rubber ring; 203, sliding groove; 204, rapid dissolution layer; 205, extrusion tooth plate; 206, sliding plate; 207, hydrophobic film; 208, triangular lifting plate; 209, delayed dissolution layer; 210, sliding block; 300, rotational acceleration unit; 301, tooth groove; 302, conical head; 303, rubber sealing ring; 304, insertion groove; 305, T-shaped ring; 306, connecting ring; 307, rotating ring; 308, fixing plate; 309, connecting plate; 310, blade. Detailed implementation manners

[0028] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention with reference to the drawings of the specification.

[0029] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0030] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure or characteristic that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is separately or selectively mutually exclusive with other embodiments.

[0031] Next, the present invention will be described in detail with reference to the schematic diagrams. When describing the embodiments of the present invention in detail, for the convenience of explanation, the cross-sectional views showing the device structure will be locally enlarged out of the general scale, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, the three-dimensional spatial dimensions of length, width, and depth should be included in the actual production.

[0032] Embodiment 1:

[0033] Referring to Figure 1 - Figure 7 , an embodiment of the present invention provides a dissolvable bridge plug for oil and gas wells with a multi-stage dissolution function, including a main body unit 100, a rising extrusion unit 200, and a rotation acceleration unit 300.

[0034] Among them, the main body unit 100 includes a bridge plug main body 101 and a connector 102 fixedly connected to one end of the bridge plug main body 101. A ball groove 103 is formed in the connector 102, and a connection ring 104 is inserted and connected in the connector 102;

[0035] Next, the rising extrusion unit 200 includes a rapid dissolution layer 204 sleeved on the outer surface of the bridge plug main body 101 and a connection ring 104 fixedly connected to the upper surface of the rapid dissolution layer 204. A sliding groove 203 is formed in the rapid dissolution layer 204. A triangular lifting plate 208 is fixedly connected in the sliding groove 203, a sliding plate 206 is slidably connected in the sliding groove 203, and an extrusion tooth plate 205 is fixedly connected to one side of the sliding plate 206;

[0036] Finally, the rotation acceleration unit 300 includes a rotating ring 307 rotatably connected in the bridge plug main body 101 and a connecting plate 309 fixedly connected to the inner surface of the rotating ring 307. A blade 310 is fixedly connected to the lower surface of the connecting plate 309. The lower surface of the blade 310 is rotatably connected to a fixing plate 308. A rubber sealing ring 303 is slidably connected to the outer side of the lower surface of the bridge plug main body 101, and a tooth groove 301 is formed on the outer surface of the rubber sealing ring 303.

[0037] Furthermore, a transition isolation layer 201 is sleeved on the outer surface of the bridge plug body 101. A delayed dissolution layer 209 is fixedly connected to the outer surface of the bridge plug body 101. A hydrophobic film 207 is plated on the outer surface of the delayed dissolution layer 209. The rapid dissolution layer 204 is made of soluble magnesium alloy. The transition isolation layer 201 is made of annular PLA material. The delayed dissolution layer 209 is made of zinc-aluminum alloy material. Secondly, for the rapid dissolution layer 204: the magnesium alloy (Mg-6Al-1Zn) has a thickness of 3-5 mm, and the dissolution rate (in 90°C brine) is 0.5-1.0 mm / h. For the transition isolation layer 201: the PLA material has a thickness of 2-3 mm, and adding 5% nano-silica enhances the hydrophobicity. The degradation rate (at 80°C) is 0.2-0.3 mm / h. For the delayed dissolution layer 209: the zinc-aluminum alloy (Zn-5Al) has a thickness of 4-6 mm, and the surface hydrophobic film 207 is a polytetrafluoroethylene coating. The dissolution rate (at 90°C) is 0.1-0.2 mm / h.

[0038] Furthermore, both the transition isolation layer 201 and the delayed dissolution layer 209 can slide on the outer surface of the bridge plug body 101. One side of the sliding plate 206 away from the extrusion tooth plate 205 is fixedly connected to the transition isolation layer 201. A sealing rubber ring 202 is fixedly connected to the outer surface of the transition isolation layer 201. One side of the transition isolation layer 201 away from the rapid dissolution layer 204 is fixedly connected to the delayed dissolution layer 209. Sliding blocks 210 are fixedly connected to both sides of the sliding plate 206, and the outer surfaces of the sliding blocks 210 are slidably connected to the inner surface of the sliding groove 203. Secondly, the inner diameter dimension of the sealing rubber ring 202 is smaller than the inner diameter dimension of the transition isolation layer 201, and the inner diameter dimension of the sealing rubber ring 202 is larger than the dimension of the middle part of the inclined surface of the rapid dissolution layer 204. Thus, during the sliding of the sealing rubber ring 202 on the inclined surface of the rapid dissolution layer 204, its inner diameter dimension is continuously expanded and stretched, so as to make it fully contact with the inner surface of the oil and gas well. Among them, in the initial stage, there is no direct contact between the transition isolation layer 201 and the rapid dissolution layer 204.

[0039] Working principle: By utilizing the transition isolation layer 201, the rapid dissolution layer 204, and the delayed dissolution layer 209, and through the difference in dissolution rates of different materials, the staged dissolution of the bridge plug is achieved. In the initial stage, the rapid dissolution layer 204 provides the initial sealing pressure, and the delayed dissolution layer 209 prolongs the overall structural stability to avoid premature failure. At the same time, the transition isolation layer 201 delays the liquid penetration through the hydrophobic membrane 207, further controls the dissolution sequence, adapts to the complex downhole environment, thereby reducing the risk of bridge plug residues, eliminating the need for milling operations, saving costs, and enabling the material combination to balance strength and soluble characteristics to meet environmental protection requirements; By linking the upward extrusion unit 200 and the rotation acceleration unit 300, when the whole device is placed in the oil and gas well and reaches the predetermined position, the conical head 302 is driven to rotate and recover through the thread shear release, and then the overall structure on the outer surface of the bridge plug body 101 rotates upward. Further, the sliding plate 206 moves in the sliding groove 203, and then drives the extrusion tooth plate 205 to slide out of the rapid dissolution layer 204, so that it fully engages with the inner surface of the oil and gas well. Further, during the upward movement of the conical head 302, the rubber sealing ring 303 is extruded, and according to its outward protruding structure, when it is extruded, the tooth grooves 301 on the outer surface of the rubber sealing ring 303 are fully extruded and contacted with the inner surface of the oil and gas well. At the same time, the fixed plate 308 is used to clamp the clamping pipe arranged inside the conical head 302, so as to prevent the rubber sealing ring 303 from loosening to a certain extent. Further, when the transition isolation layer 201 moves upward and extrudes the side of the rapid dissolution layer 204, the inclined plane on one side of the rapid dissolution layer 204 is used to extrude the sealing rubber ring 202, so that it expands and stretches outward, and is fully extruded and fixed with the inner surface of the oil and gas well. Thus, the inside of the oil and gas well is sealed by the rubber sealing ring 303 and the sealing rubber ring 202;

[0040] By utilizing the T-shaped ring 305, the connecting ring 306, the rotating ring 307, the fixed plate 308, the connecting plate 309, and the blade 310, the downhole fluid drives the blade 310 to rotate, drives the rotating ring 307 and the connecting ring 306 to move, accelerates the exposure and dissolution of the delayed dissolution layer 209, and then utilizes the hydrodynamic force to assist in accelerating the dissolution and reduce the post-operation treatment time.

[0041] Example two:

[0042] Refer to Figure 2 - Figure 5 and Figure 7, the difference compared with the first embodiment is as follows: a conical head 302 is fixedly connected to one side of the rubber sealing ring 303, a communication groove is formed in the fixing plate 308, an adapter ring 306 is fixedly connected to the outer surface of the fixing plate 308, a T-shaped ring 305 is fixedly connected to the lower surface of the adapter ring 306, an insertion groove 304 is formed in the conical head 302. Secondly, a threaded groove is formed in the conical head so that it can be connected and driven with the threaded shear release. Further, a clamping tube is fixedly connected to the upper surface of the conical head. When the conical head rises, it is clamped and fixed to the fixing plate through the clamping tube, thereby performing a clamping and limiting process on the rubber sealing ring to a certain extent. Among them, the structure of the rubber sealing ring 303 bulges outwards.

[0043] Further, the mutually approaching sides of the transition isolation layer 201 and the rapid dissolution layer 204 are both set as inclined planes. The inclined plane on the upper surface of the transition isolation layer 201 can be fitted and contacted with the inclined plane on one side of the rapid dissolution layer 204. Secondly, after the sealing rubber ring is pushed by the inclined plane, its inner surface is ejected from one side of the inclined surface of the transition isolation layer, so that its inner surface is ejected and pressed against the outer surface of the transition isolation layer, thereby ensuring that the sealing rubber ring continuously performs a blocking process to a certain extent.

[0044] Working principle: First, after the bridge plug body 101 is lowered to the target position by the wellhead tool, the externally arranged threaded shear release is meshed and connected with the threaded groove of the conical head 302, triggering a shearing action to separate the bridge plug from the lowering tool. Subsequently, the conical head 302 is driven to rotate upwards and retract by the lifting tool, and this rotation is transmitted to the bridge plug body 101, driving the sliding plate 206 on its outer part to move along the sliding groove 203. When the sliding plate 206 moves, it drives the extrusion tooth plate 205 to slide out from the inside of the rapid dissolution layer 204, and the serrated outer edge thereof is embedded in the wellbore wall to form a preliminary mechanical anchoring. During the rising process of the conical head 302, it is limited by the clamping structure between the clamping tube and the fixing plate 308, and at the same time, the rubber sealing ring 303 is extruded to expand radially outwards, so that the tooth groove 301 is tightly engaged with the wellbore wall to form a double sealing barrier. The inclined plane design of the transition isolation layer 201 and the rapid dissolution layer 204 are mutually fitted when the bridge plug body 101 rotates and rises, pushing the sealing rubber ring 202 to slide along the inclined surface of the rapid dissolution layer 204. Under the action of the oblique thrust, the inner diameter of the sealing rubber ring 202 is expanded and stretched, and the outer diameter is completely attached to the wellbore wall, further enhancing its sealing performance;

[0045] Secondly, the fast-dissolving layer 204 (Mg-6Al-1Zn) first contacts the downhole fluid and rapidly degrades due to its high dissolution rate (0.5 - 1.0 mm / h), releasing the initial sealing pressure. The PLA material (containing 5% nano-silica) of the transition isolation layer 201 delays the fluid penetration through its hydrophobic property, preventing the premature exposure of the delayed-dissolving layer 209. After the fast-dissolving layer 204 is completely degraded, the transition isolation layer 201 begins to slowly degrade (0.2 - 0.3 mm / h), and its annular structure gradually disintegrates, exposing the delayed-dissolving layer 209. At this time, the sealing function is maintained by the zinc-aluminum alloy (Zn-5Al) of the delayed-dissolving layer 209 and the external hydrophobic film 207. Its low dissolution rate (0.1 - 0.2 mm / h) ensures the structural stability. The rotation acceleration unit 300 drives the blade 310 to rotate through the downhole fluid, driving the rotation of the rotating ring 307 and the linkage of the connecting ring 306, making the dissolution surface of the delayed-dissolving layer 209 be dynamically exposed to the fluid. The communication groove design of the fixing plate 308 accelerates the fluid circulation, flushing the surface of the delayed-dissolving layer 209, and further shortening the disintegration time of the residual structure in combination with the mechanical movement;

[0046] Finally, the engaging structure between the engaging tube of the conical head 302 and the fixing plate 308 forms a rigid lock after rising in place, preventing the rubber sealing ring 303 from retracting due to the downhole pressure fluctuation and ensuring the continuous effectiveness of the seal. The blade 310 drives the rotating ring 307 to rotate under the fluid impact, and through the linkage of the connecting ring 306 and the T-shaped ring 305, periodically disturbs the fluid around the delayed-dissolving layer 209, breaking the static dissolution equilibrium. This dynamic process accelerates the local damage of the hydrophobic film 207 and promotes the uniform dissolution of the zinc-aluminum alloy.

[0047] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A dissolvable bridge plug for oil and gas wells with a multi-stage dissolution function, characterized in that, The dissolvable bridge plug includes: A main body unit (100), which includes a bridge plug main body (101) and a connector (102) fixedly connected to one end of the bridge plug main body (101). A ball groove (103) is formed in the connector (102), and a connecting ring (104) is inserted and connected in the connector (102); A rising extrusion unit (200), which includes a quick dissolution layer (204) sleeved on the outer surface of the bridge plug main body (101) and a connecting ring (104) fixedly connected to the upper surface of the quick dissolution layer (204). A sliding groove (203) is formed in the quick dissolution layer (204), a triangular lifting plate (208) is fixedly connected in the sliding groove (203), a sliding plate (206) is slidably connected in the sliding groove (203), and an extrusion tooth plate (205) is fixedly connected to one side of the sliding plate (206); A rotation acceleration unit (300), which includes a rotating ring (307) rotatably connected in the bridge plug main body (101) and a connecting plate (309) fixedly connected to the inner surface of the rotating ring (307). A blade (310) is fixedly connected to the lower surface of the connecting plate (309), a fixing plate (308) is rotatably connected to the lower surface of the blade (310), a rubber sealing ring (303) is slidably connected to the outer side of the lower surface of the bridge plug main body (101), and a tooth groove (301) is formed on the outer surface of the rubber sealing ring (303).

2. The dissolvable bridge plug for oil and gas wells with a multi-stage dissolution function according to claim 1, wherein: A transition isolation layer (201) is sleeved on the outer surface of the bridge plug main body (101), a delayed dissolution layer (209) is fixedly connected to the outer surface of the bridge plug main body (101), a hydrophobic film (207) is plated on the outer surface of the delayed dissolution layer (209), the quick dissolution layer (204) is made of soluble magnesium alloy, and the transition isolation layer (201) is a ring-shaped PLA material.

3. The dissolvable bridge plug for oil and gas wells with a multi-stage dissolution function according to claim 2, characterized in that: The delayed dissolution layer (209) is made of zinc-aluminum alloy material. Both the transition isolation layer (201) and the delayed dissolution layer (209) can slide on the outer surface of the bridge plug main body (101). The side of the sliding plate (206) away from the extrusion tooth plate (205) is fixedly connected to the transition isolation layer (201).

4. The dissolvable bridge plug for oil and gas wells with a multi-stage dissolution function according to claim 3, wherein: A sealing rubber ring (202) is fixedly connected to the outer surface of the transition isolation layer (201). The side of the transition isolation layer (201) away from the quick dissolution layer (204) is fixedly connected to the delayed dissolution layer (209). Sliding blocks (210) are fixedly connected to both sides of the sliding plate (206), and the outer surfaces of the sliding blocks (210) are slidably connected to the inner surface of the sliding groove (203).

5. The dissolvable bridge plug for oil and gas wells with multi-stage dissolution function according to claim 1, wherein: A tapered head (302) is fixedly connected to one side of the rubber sealing ring (303). A communication groove is formed in the fixing plate (308). An adapter ring (306) is fixedly connected to the outer surface of the fixing plate (308). A T-shaped ring (305) is fixedly connected to the lower surface of the adapter ring (306). An insertion groove (304) is formed in the tapered head (302).

6. The dissolvable bridge plug for oil and gas wells with a multi-stage dissolution function according to claim 4, characterized in that: Both the side of the transition isolation layer (201) and the side of the fast dissolution layer (204) that are close to each other are provided with inclined planes, and the inclined plane on the upper surface of the transition isolation layer (201) can be fitted and contacted with the inclined plane on one side of the fast dissolution layer (204).

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