Dissolvable, variable-diameter metal sealing and fracturing bridge plug

1. A dissolvable, variable-diameter metal sealing and fracturing bridge plug, comprising:

a conical body, wherein, the conical body is made from a dissolvable metal and has an axial hollow passage therein, an external conical surface, and an external thread section on the top thereof;

a central connection shaft, wherein, the central connection shaft is slidably inserted into the hollow passage of the conical body and has an external thread section on an end portion thereof;

a slip, wherein, the slip is made from a dissolvable metal, the slip is provided with an internal conical surface corresponding in shape to the external conical surface of the conical body and an external surface having a radical section that is a plane, and is movably installed on the external conical surface of the conical body;

a tail base, wherein, the tail base is made from a dissolvable metal, is installed on an end of the top of the conical body and contacted with the slip, and is internally provided with two adjacent internal thread sections orderly reduced in diameter, wherein a broken interlocking thread bushing having threads on internal and external surfaces thereof is screwed at a big-diameter internal thread section, and a small-diameter internal thread section is screwed with an external thread section of the central connection shaft;

a variable-diameter sealing ring, wherein, the variable-diameter sealing ring is made from a dissolvable metal, is increased in overall diameter when internally subjected to an outward expansion force, is installed on a side of the slip close to the bottom of the conical body, and is provided with an internal conical surface matching with the external conical surface and the external surface having the radical section; and

a variable-diameter supporting ring, wherein, the variable-diameter supporting ring is made from a dissolvable metal, is increased in overall diameter when internally subjected to an outward expansion force, is installed between the variable-diameter sealing ring and the slip, is provided with an internal conical surface matching with the external conical surface and the external surface having the radical section, and is arranged to transfer a squeezing force of the slip to the variable-diameter sealing ring and relieve the squeezing force.

2. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 1 , wherein

an annular inwardly-recessed sealing groove is arranged on the external surface of the variable-diameter sealing ring or the variable-diameter supporting ring, and a sealing ring made from a dissolvable metal or rubber is installed in the sealing groove.

3. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 2 , wherein

more than one variable-diameter sealing ring or variable-diameter supporting ring is arranged in the sealing groove.

4. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 1 , wherein

a ceramic structure having an anchoring reinforcement effect is arranged on the external surface of the slip, the ceramic structure being ceramic blocks, ceramic plates or arc-shaped ceramic sections are arranged at intervals, and a protruding included angle is arranged on a side of the ceramic structure that faces a well wall.

5. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 1 , wherein

a thread pitch between the threads on the external surface of the interlocking thread bushing is greater than that between the threads on the internal surface of the interlocking thread bushing, and the threads on the external surface of the interlocking thread bushing are leaning threads leaning towards the direction of the tail base.

6. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 1 , wherein

a chamfer configured to be inserted into the inside of the interlocking thread bushing is arranged on an end portion of the external thread section of the conical body, and a space is reserved between the external surface of the interlocking thread bushing and the big-diameter internal thread section of the tail base for the inserted external thread section of the conical body to expand.

7. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 1 , wherein

a tail end of the central connection shaft is provided with an external thread section for facilitating the connection of another device.

8. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 7 , wherein

an end surface of the bottom of the conical body is a conical pit that is axially inwardly recessed.

9. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 8 , wherein

the external thread section on the tail end of the central connection shaft is provided with a stop collar on an end close to the conical body, one end surface of the stop collar is a conical surface facing the conical pit, and the other end surface of the stop collar is a plane, the conical surface has a smaller taper than the conical pit, and the stop collar has a smaller diameter than the bottom of the conical body.

10. The dissolvable, variable-diameter metal sealing and fracturing bridge plug according to claim 1 , wherein

contact surfaces of the tail base and the slip are provided with limiting keys snapped with each other to prevent either of the tail base and the slip from rotating in a radical direction.