CN113006745B

CN113006745B - Semi-submersible mining equipment

Info

Publication number: CN113006745B
Application number: CN202110486401.2A
Authority: CN
Inventors: 刘刚
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-04-30
Filing date: 2021-04-30
Publication date: 2023-01-10
Anticipated expiration: 2041-04-30
Also published as: CN113006745A

Abstract

The invention discloses semi-submersible type mining equipment which comprises a semi-submersible type ship body, a leakproof cabin, an umbilical cable and a mining pipe column. The semi-submersible ship body can be arranged below the sea surface, so that the influence of weather and wind waves on the semi-submersible mining equipment is weakened to a certain extent, the working environment of the semi-submersible mining equipment is improved, the influence of marine environment on the semi-submersible mining equipment is reduced, the working range and the service life of the semi-submersible mining equipment are improved, meanwhile, the semi-submersible mining equipment is easy to isolate from air, the fire-proof and explosion-proof safety level of the semi-submersible mining equipment can be improved to a certain extent, and the risk of equipment and workers caused by natural gas hydrate mining is reduced; meanwhile, an independent space is formed in the natural gas hydrate formation region around the shaft by using the leakage-proof cabin, gas generated in the exploitation process can be gathered in the leakage-proof cabin, uncontrolled decomposition of hydrate caused by formation landslide possibly caused by exploitation is reduced, and the risk brought by natural gas hydrate exploitation is further reduced.

Description

Semi-submersible mining equipment

Technical Field

The invention relates to the technical field of ocean oil and gas exploitation, in particular to semi-submersible exploitation equipment.

Background

The exploitation of the natural gas hydrate is influenced by the marine environment, and the conditions of large wind, high wave or changeable climate in the exploitation sea area can be met in the exploitation process, so that the exploitation difficulty of the natural gas hydrate is increased.

The exploitation equipment of the natural gas hydrate floats on the sea surface, faces to the severe working environment, if the exploitation equipment is controlled improperly, gas decomposed from the natural gas hydrate is easy to leak, even fire and explosion are induced, the life of the equipment can be damaged, and the life safety of workers is greatly threatened.

Therefore, how to reduce the influence of marine environment on the exploitation equipment and reduce the risk of natural gas hydrate exploitation on the equipment and workers becomes a technical problem to be solved urgently by technical personnel in the field.

Disclosure of Invention

In view of the above, the invention provides a semi-submersible mining device, so as to reduce the influence of marine environment on the mining device and reduce the risk of natural gas hydrate mining on the device and workers.

In order to achieve the purpose, the invention provides the following technical scheme:

a semi-submersible type mining device comprises a semi-submersible type ship body, a leakproof cabin, an umbilical cable and a mining pipe column,

the semi-submersible hull can be located below the sea surface;

the umbilical cable is used for communicating the leakproof cabin with the semi-submersible hull;

the production string can be left in a wellbore of a gas hydrate formation as a production string;

the lower extreme of preventing leaking the cabin is open end, it establishes to prevent leaking the cabin through open end cover on the natural gas hydrate stratum and can with prevent leaking the cabin coverage in the natural gas hydrate stratum is kept apart with the external world, prevent leaking the cabin pass through the preventer with the upper end of exploitation tubular column is connected, prevent leaking the cabin pass through the umbilical cable mount pad with the umbilical cable is connected, prevent leaking the cabin and be used for gathering the gas that the exploitation tubular column was opened the extraction and prevent that the cabin covers the gas that the natural gas hydrate stratum released.

Preferably, in the semi-submersible mining apparatus, the containment tank includes a prismatic tank body and a sealing base,

the upper end of the prismatic cabin body is provided with a pyramid-shaped top, the pyramid-shaped top is connected with the umbilical cable through an umbilical cable mounting seat, the pyramid-shaped top is connected with the mining pipe column through the blowout preventer, and the lower end of the prismatic cabin body is an open end;

the sealing bases are connected with the open end of the prismatic cabin body and used for achieving sealing between the open end of the prismatic cabin body and the natural gas hydrate stratum, the number of the sealing bases is equal to the number of prismatic surfaces of the prismatic cabin body, and the sealing bases can be sunk on the natural gas hydrate stratum.

Preferably, in the semi-submersible mining apparatus, the sealing base is an elastomer base, and adjacent elastomer bases are connected in a sealing manner.

Preferably, in the semi-submersible mining apparatus, the number of the containment bays is plural, the open end of each containment bay is provided with the sealing base, and adjacent containment bays are connected through the sealing base.

Preferably, in the above semi-submersible production apparatus, the production string comprises a drilling tool and a string, the string being connected to the containment tank through the blowout preventer,

the drilling tool comprises a rotary jet drill bit and a bottom hole power drilling tool, the bottom hole power drilling tool is connected with the rotary jet drill bit,

the pipe column comprises an inner pipe, an outer pipe and a sieve pipe, wherein the inner pipe, the outer pipe and the sieve pipe are flexible pipes, one end of the outer pipe is connected with the prismatic cabin body through the blowout preventer, the other end of the outer pipe is connected with the sieve pipe, the sieve pipe is connected with the shell of the well bottom power drilling tool, the inner pipe is positioned in the outer pipe and the sieve pipe, a back pressure valve is arranged in the inner pipe and is positioned below the throwing and releasing hand, the other end of the inner pipe is communicated with a high-pressure fluid inlet of the well bottom power drilling tool,

and filling layers are arranged between the inner pipe and the outer pipe and between the inner pipe and the sieve pipe, the inner pipe is connected with the outer pipe and the inner pipe is connected with the sieve pipe through the filling layers, and the filling layers are used for filtering sand grains decomposed from the natural gas hydrate.

Preferably, in the semi-submersible mining equipment, an electric heater is embedded in the filling layer between the sieve tube and the inner tube, the electric heater is used for providing heat for decomposition of the natural gas hydrate, and the electric heater is connected with a power supply through a heating cable.

Preferably, in the semi-submersible mining equipment, the closed end of the prismatic tank body is provided with a mounting hole for mounting the blowout preventer, the blowout preventer comprises an outer blowout preventer assembly and an inner blowout preventer assembly, the outer blowout preventer assembly is mounted outside the prismatic tank body, the inner blowout preventer assembly is mounted inside the prismatic tank body,

the outer blowout preventer assembly comprises a mounting seat and a blowout preventer,

the mounting seat is mounted outside the prismatic cabin body and corresponds to the mounting hole in position, a first through hole for the outer pipe to pass through is formed in the mounting seat, a first channel and a second channel are arranged in the mounting seat, the first channel can be communicated with a first pipeline for supplying a chemical agent in the umbilical cable, and the second channel can be communicated with a second pipeline for supplying a high-pressure fluid in the umbilical cable;

the anti-spraying cover is covered at one end of the mounting seat, which is far away from the prismatic cabin body, and is used for preventing external seawater from entering the prismatic cabin body, the anti-spraying cover is sleeved on the outer pipe, the outer pipe is fixed on the mounting seat through the anti-spraying cover, the anti-spraying cover is in locking connection with the mounting seat through a stop ring, a second through hole corresponding to the first through hole is formed in the anti-spraying cover, a third channel and a fourth channel are arranged in the anti-spraying cover, one end of the third channel is communicated with the first channel, the other end of the third channel can be communicated with the inner pipe, one end of the fourth channel is communicated with the second channel, and the other end of the fourth channel can be communicated with the inner pipe;

the inner blowout prevention assembly comprises a flange base, a plurality of lotus-shaped claw flaps and a plurality of web-shaped claw flaps, the flange base and the mounting base are coaxially arranged, the lotus-shaped claw flaps and the web-shaped claw flaps are arranged along the circumferential direction of the flange base and are arranged at intervals, one ends of the lotus-shaped claw flaps and the web-shaped claw flaps are connected with the flange base through elastic hinges, one ends of the lotus-shaped claw flaps and the web-shaped claw flaps far away from the flange base are free ends, the free ends of the lotus-shaped claw flaps and the web-shaped claw flaps can stretch along the circumferential direction of the flange base to drive the free ends of the lotus-shaped claw flaps connected with the web-shaped claw flaps to move along the direction perpendicular to the axis direction of the flange base, and the free ends of the lotus-shaped claw flaps and the web-shaped claw flaps can be attached to the outer wall under the common action of the elastic force of the gas in the cabin body and the outer wall of the outer pipe.

Preferably, in the semi-submersible mining apparatus, the umbilical cable further includes a gas pipeline for conveying gas in the containment tank to the semi-submersible hull and a heat tracing cable for heating the gas pipeline.

According to the technical scheme, the semi-submersible type mining equipment comprises a semi-submersible type ship body, a leakproof cabin, an umbilical cable and a mining pipe column. The semi-submersible ship body can be arranged below the sea surface, so that the influence of weather and wind waves on the semi-submersible mining equipment is weakened to a certain extent, the working environment of the semi-submersible mining equipment is improved, the influence of marine environment on the semi-submersible mining equipment is reduced, the working range and the service life of the semi-submersible mining equipment are improved, meanwhile, the semi-submersible ship body is mainly arranged below the sea surface, the isolation from air is easy to realize, the fireproof and explosion-proof safety level of the semi-submersible mining equipment can be improved to a certain extent, and the risk of natural gas hydrate mining on equipment and workers is reduced; meanwhile, an independent space is formed in the natural gas hydrate formation region around the shaft by using the leakage-proof cabin, gas generated in the exploitation process can be gathered in the leakage-proof cabin, uncontrolled decomposition of hydrate and leakage to the surrounding seawater, which are possibly caused by stratum landslide due to exploitation, are reduced, and the risk brought by natural gas hydrate exploitation is further reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic structural view of a semi-submersible mining installation provided in accordance with an embodiment of the present invention;

FIG. 2 is a schematic illustration of a production string provided in accordance with an embodiment of the present invention;

FIG. 3 isbase:Sub>A cross-sectional view A-A of FIG. 2;

FIG. 4 is a cross-sectional view taken along line B-B of FIG. 2;

fig. 5 is a schematic structural view of a containment chamber according to a first embodiment of the present invention;

fig. 6 is a side view of a containment tank provided in accordance with a first embodiment of the present invention;

fig. 7 is a schematic structural view of a containment chamber according to a second embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a sealed blowout preventer according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of an umbilical cable according to an embodiment of the present invention.

1. The semi-submersible ship comprises a semi-submersible ship body, 2, a leakproof cabin, 21, a cabin body, 22, a sealing capsule, 3, a production string, 31, a downhole power drill, 311, a drill string, 312, a rotary jet drill bit, 32, a pipe column, 321, an inner pipe, 322, an outer pipe, 323, a sieve pipe, 4, a sealing blowout preventer, 41, a mounting seat, 42, a blowout preventer, 43, a blowout preventer, 431, a flange base, 432, a lotus-shaped claw-shaped-claw-shaped, 433, a web-shaped claw-shaped, 5, an umbilical cable, 51, a gas pipeline, 52, a first pipeline, 53, a second pipeline, 54 and a heat tracing cable.

Detailed Description

The invention discloses semi-submersible mining equipment, which aims to reduce the influence of marine environment on the mining equipment and reduce the risk of equipment and workers caused by natural gas hydrate mining.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Please refer to fig. 1-8.

The invention discloses semi-submersible type exploitation equipment which is used for realizing exploitation of natural gas hydrate and reducing the influence of marine environment on the exploitation of the natural gas hydrate.

The semi-submersible type mining equipment disclosed by the scheme comprises a semi-submersible type ship body 1, a leakage-proof cabin 2, an umbilical cable 5 and a mining pipe column 3.

The semi-submersible type ship body 1 can be arranged below the sea surface, the influence of weather and wind waves on the semi-submersible type mining equipment is weakened to a certain extent, the working environment of the semi-submersible type mining equipment is improved, the influence of marine environment on the semi-submersible type mining equipment is reduced, the working range and the service life of the semi-submersible type mining equipment are improved, meanwhile, the semi-submersible type ship body 1 is mainly arranged below the sea surface, isolation from air is easy to achieve, the fire and explosion protection safety level of the semi-submersible type mining equipment can be improved to a certain extent, and the risk of natural gas hydrate mining on equipment and workers is reduced.

The lower end of the leakproof cabin 2 is an open end, the leakproof cabin 2 is arranged on the natural gas hydrate stratum through an open end cover and can isolate the natural gas hydrate stratum within the coverage range of the leakproof cabin 2 from the outside, and a three-dimensional space with a certain volume is formed on the natural gas hydrate stratum.

Due to rapid sedimentation or turbidity current sedimentation formed by landslide and the formation of thick, soft, high-water-content and unconsolidated stratum by the sediment on the land slope, the exploitation is greatly influenced by an unstable seabed, and great difficulty is brought to the exploitation of the natural gas hydrate. The semi-submersible mining equipment disclosed by the scheme utilizes the leakage-proof cabin 2 to form an independent space in the natural gas hydrate stratum area around the shaft, gas generated in the mining process can be gathered in the leakage-proof cabin 2, meanwhile, uncontrolled decomposition of hydrate caused by stratum landslide possibly caused by mining is reduced, gas leakage is avoided, and pollution to the environment is reduced.

The containment tank 2 is in communication with the semi-submersible hull 1 via an umbilical 5 for conveying gases collected in the containment tank 2 to the semi-submersible hull 1. In order to improve the connection stability between the leakproof cabin 2 and the semi-submersible hull 1, the leakproof cabin 2 is connected with the semi-submersible hull 1 through a traction rope.

The production string 3 can be left in the wellbore of the gas hydrate formation as a production wellbore, and gas produced in the production wellbore enters the containment 2.

An escape cabin is arranged on the semi-submersible type ship body 1 of the semi-submersible type mining equipment. Under the condition that the semi-submersible type mining equipment is in a safe environment, the escape compartment can be used as a life center of workers, when the semi-submersible type mining equipment is in a dangerous environment, the escape compartment can be separated from the semi-submersible type ship body 1, the workers can take the escape compartment to escape quickly, the emergency action of the semi-submersible type mining equipment can be controlled remotely through the equipment in the escape compartment, and therefore the danger brought to the workers, the equipment and the environment due to the exploitation of natural gas hydrate is reduced.

In a specific embodiment of the scheme, the escape compartment is connected with the semi-submersible hull 1 in a hanging manner, the escape compartment can be quickly separated from the semi-submersible hull 1 in a connection manner, workers can quickly leave a dangerous environment, and the emergency action of the semi-submersible mining equipment can be remotely controlled to reduce the danger brought to the workers, equipment and the environment by the exploitation of natural gas hydrate.

Preferably, the escape compartment can remotely control the semi-submersible type mining equipment, and emergency and danger treatment is carried out by remotely controlling the semi-submersible type mining equipment; after the danger alarm is relieved, the escape compartment can be connected with the semi-submersible type hull 1 again, and the working safety of workers is improved.

Preferably, the escape capsule can be in communication connection with a ground control console, and the escape capsule is remotely controlled to be separated from the semi-submersible hull 1 through the ground control console.

An inert gas protection device is arranged in the semi-submersible type ship body 1 and is used for forming an inert gas environment in the semi-submersible type ship body 1, and the fire-proof and explosion-proof safety level of the semi-submersible type mining equipment is further improved. In this embodiment, the worker is required to wear the air breathing apparatus.

In a particular embodiment of the solution, the inert gas protection is a carbon dioxide protection. The carbon dioxide protection device can convey carbon dioxide gas into the protection area of the semi-submersible type ship body 1, so that the oxygen concentration in the protection area reaches and is kept below the limit oxygen content of explosion, and the purpose of fire protection is achieved.

In one embodiment of the present solution, the containment chamber 2 comprises a prismatic chamber body 21 and a sealing base 22.

The upper end of the prismatic cabin body 21 is provided with a pyramid top (the closed end of the prismatic cabin body 21 is in a pyramid shape), the pyramid top is connected with an umbilical cable 5 through an umbilical cable mounting seat, the pyramid top is connected with an exploitation tubular column 3 through a blowout preventer 4, and the lower end of the prismatic cabin body 21 is an open end and can be covered on a natural gas hydrate stratum to be drilled.

The sealing base 22 is connected with the open end of the prismatic tank body 21, and the sealing base 22 can be in contact with a natural gas hydrate stratum and is used for sealing the open end of the prismatic tank body 21 and the natural gas hydrate stratum.

The sealing bases 22 are arranged along the shape of the open end of the prismatic tank 21, the number of the sealing bases 22 is equal to the number of the prismatic surfaces of the prismatic tank 21, and the sealing bases 22 have large mass and can be settled on a natural gas hydrate stratum.

In a specific embodiment of the present embodiment, the sealing bases 22 are synthetic rubber bases, and the adjacent sealing bases 22 of the same prismatic cabin 21 are sealed, i.e. the adjacent sealing bases 22 are not communicated. The sealing base 22 disclosed by the scheme injects seawater with different volumes into the sealing base 22 at different positions of the prismatic cabin body 21 so as to adjust the posture of the leakproof cabin 2, thereby adjusting the sealing effect between different positions of the leakproof cabin 2 and the natural gas hydrate stratum; or, when the displacement is needed, the liquid and the gas in the sealing base 22 are filled or discharged, the shape of the sealing base 22 is changed, the silting on the periphery of the leakproof compartment 2 is removed, and the displacement of the leakproof compartment 2 is realized; or when the patient needs to be evacuated, part of liquid and gas in the sealing base 22 is discharged, and meanwhile, the sealing base 22 is inflated, so that the buoyancy of the containment chamber 2 is increased, and the lifting weight of the containment chamber 2 is reduced.

In the scheme, the prismatic cabin body 21 has certain strength and pressure resistance, a closed space with a certain area can be formed on a natural gas hydrate stratum, in the mining process, gas generated and/or overflowed from the natural gas hydrate stratum is collected in the prismatic cabin body 21 of the leakage-proof cabin 2, meanwhile, if the well wall collapses in the mining process, the natural gas hydrate is decomposed uncontrollably on a large scale, the decomposed gas is also collected in the prismatic cabin body 21 of the leakage-proof cabin 2, and the gas is prevented from overflowing and diffusing into seawater. The gas gathered in the leakproof cabin 2 is conveyed to the semi-submersible hull 1 through the pipeline, so that the resource waste and the environmental pollution are effectively reduced.

The containment chamber 2 comprises a plurality of prismatic chamber bodies 21, wherein the open end of each prismatic chamber body 21 is provided with a sealing base 22, and two adjacent prismatic chamber bodies 21 are connected through the sealing bases 22.

The honeycomb structure is formed by the appearances of the plurality of prismatic cabins 21, at least one blowout preventer 4 is arranged on each prismatic cabin 21, one pipe column 32 is arranged in each blowout preventer 4, and natural gas hydrate is exploited through the plurality of pipe columns 32, so that the exposed area of the stratum is increased, and the exploitation efficiency is improved.

Specifically, the coverage area of a single prismatic cabin body 21 to the natural gas hydrate formation can reach 2000 square meters, and a plurality of prismatic cabin bodies 21 are combined, so that the coverage area of the leakage-proof cabin 2 to the natural gas hydrate formation is increased. The methane gas generated by decomposition is dispersedly controlled in the plurality of prismatic cabin bodies 21 of the leakage-proof cabin 2, so that the large-scale decomposition of the natural gas hydrate can be effectively controlled, and the ecological risk caused by the large-scale decomposition and leakage of the natural gas hydrate is effectively prevented.

The separation process of natural gas hydrate and rock debris returned from a well bore in seawater in the mining process is as follows:

the natural gas hydrate and the rock debris returned from the shaft enter the leakage-proof cabin 2 in the mining process, the natural gas hydrate and the rock debris are automatically separated in seawater by virtue of density, the gas separated out from the natural gas hydrate rises and gathers at the top of the leakage-proof cabin 2 and is conveyed to the semi-submersible ship body 1 through the umbilical cable 5, and the rock debris sinks and remains at the bottom of the leakage-proof cabin 2.

In the scheme, the production string 3 comprises a drilling tool 31 and a string 32, and the string 3 is connected with the leakproof cabin 2 through a blowout preventer 4.

The drilling tool 31 comprises a rotary jet drill bit 311 and a bottom hole motor 312, the rotary jet drill bit 311 being connected to the bottom hole motor 312.

The tubular string 32 includes an inner pipe 321, an outer pipe 322, and a screen 323, all of which are flexible pipes.

One end of the outer pipe 322 is connected to the pod 2 through the blowout preventer 4, the other end of the outer pipe 322 is connected to the screen 323, the screen 323 is connected to the casing of the bottom hole motor 312, the inner pipe 321 is located inside the outer pipe 322 and the screen 323, and preferably, the length of the inner pipe 321 is at least equal to the sum of the lengths of the outer pipe 322 and the screen 323.

A back pressure valve is used to effect an internal seal at the upper end of the rear tubular string 32 after the release.

The inner pipe of the string 32 is a continuous inner pipe 321, the outer pipe 322 is a continuous outer pipe 322, the screen 323 is a continuous screen 323, the outer pipe 322 is connected with the screen 323, and the outer pipe 322 and the screen 323 are both outside the inner pipe 321.

It should be noted here that the continuous inner pipe 321 is an inner pipe 321 with no break in the middle, one pipe string 32 only has one inner pipe 321, and there is no need to connect adjacent inner pipes 321, and the length of the inner pipe 321 is determined according to the production depth of the gas hydrate; the continuous outer pipe 322 is the outer pipe 322 without interruption in the middle, one pipe column 32 only has one outer pipe 322, the connection of the adjacent outer pipes 322 is not required, and the length of the outer pipe 322 is determined according to the exploitation depth of the natural gas hydrate; the continuous screen pipe 323 is a screen pipe 323 without interruption in the middle, and one pipe column 32 is only provided with one screen pipe 323, so that the connection of the adjacent screen pipes 323 is not required, and only the connection between the screen pipes 323 and the outer pipe 322 is required; the inner pipe 321, the outer pipe 322, and the screen 323 are pipes having a small hardness, and can be bent in accordance with the bending of the wellbore.

In the scheme, a conveying space of the natural gas hydrate is formed between the inner pipe 321 and the outer pipe 322, gas decomposed from the natural gas hydrate enters the sieve pipe 323 and the inner pipe 321 through the sieve pipe 323, and the filling layers between the outer pipe 322 and the inner pipe 321 realize connection of the inner pipe 321 and the outer pipe 322 and the sieve pipe 323 and can filter gravel and the like decomposed from the natural gas hydrate.

During production, natural gas decomposed from the natural gas hydrate formation enters between the screen pipe 323 and the inner pipe 321 through the gaps of the screen pipe 323, and then enters the leakproof cabin through the gaps of the screen pipe 323 and the annular space between the well casing and the screen pipe.

The double-wall flexible pipe column 32 adopted by the scheme is a small-diameter and flexible pipe column, and compared with the mode that a large-diameter drilling tool and a large-diameter casing pipe column are adopted in the prior art, the influence of drilling operation on the stratum can be reduced, the risk of stratum landslide and collapse is reduced, the termination of pilot production and even failure are avoided, and the economic loss is reduced.

Because the tubular column 32 adopted by the scheme has little damage to the stratum, multi-point exploitation can be carried out on the target shallow natural gas hydrate stratum so as to improve the productivity. The multi-point mining needs to be explained here, and the multi-point mining is to reasonably drill a plurality of mineshafts in a target shallow natural gas hydrate stratum, and pipe columns disclosed by the scheme are reserved in the mineshafts.

The tubular string 32 is a tubular string 32 comprised of an inner pipe 321, an outer pipe 322, and a screen 323. The natural gas hydrate in the shallow natural gas hydrate formation enters the space between the sieve pipe 323 and the inner pipe 321 through the sieve pipe 323 of the pipe column 32, then enters the space between the outer pipe 322 and the inner pipe 321 upwards, and gravel decomposed from the natural gas hydrate is filtered through the filling layer between the outer pipe 322 and the inner pipe 321. In the scheme, the pipe column 32 consists of an inner pipe 321, an outer pipe 322 and a sieve pipe 323, can drill a shallow natural gas hydrate stratum, has relatively small diameter, is suitable for drilling a small well hole, and has relatively low cost compared with the mode of drilling a large well hole by utilizing the pipe column 32 with large diameter in the prior art.

The pipe column body disclosed by the scheme is a double-layer pipe column body, the outer pipe 322+ the sieve pipe 323 of the double-layer pipe column body and the inner pipe 321 are synchronously lowered in the one-time drilling process of the downhole power drilling tool 31, and the well drilling and the well completion are completed at one time.

The tubular column disclosed by the scheme is low in construction cost and simple in mining process, has no strict requirements on the type and lithology of the natural gas hydrate reservoir stratum, the particle size of the stratum and the like, and greatly improves the application range of the natural gas hydrate mining method related to the patent to the reservoir stratum.

In order to further optimize the technical scheme, an electric heater is arranged between the sieve tube 323 and the inner tube 321 of the mining pipe column 3 disclosed by the scheme, the electric heater is connected with a power supply of a production platform through a cable, and the electric heater is embedded in the filling layer.

The electric heater is used for heating the natural gas hydrate stratum, so that the decomposition of the natural gas hydrate is promoted, and the production efficiency is improved.

Preferably, the electric heater is spirally wound along the annular space between the sieve tube 323 and the inner tube 321, so that the length of the electric heater on the production string 3 is prolonged as much as possible, the heating area of the electric heater on the natural gas hydrate formation is increased, the decomposition speed of the natural gas hydrate is controlled, and the production efficiency is improved.

In a particular embodiment of the solution, the electric heater is a heat tracing band.

The closed end of the prismatic tank body 21 is provided with a mounting hole for mounting the blowout preventer 4, the blowout preventer 4 comprises an outer blowout preventer and an inner blowout preventer, the outer blowout preventer is mounted outside the prismatic tank body 21, and the inner blowout preventer (43) is mounted inside the prismatic tank body 21. The outer blowout preventer assembly includes a mount 41 and a blowout preventer 42,

the mounting seat 41 is mounted outside the prismatic cabin body 21 and corresponds to the mounting hole, a first through hole for the outer pipe 322 to pass through is formed in the mounting seat 41, a first channel and a second channel are arranged in the mounting seat 41, the first channel can be communicated with a first pipeline 52 for supplying chemical agents in the umbilical cable 5, and the second channel can be communicated with a second pipeline 53 for supplying high-pressure fluid in the umbilical cable 5;

the anti-spraying cover 42 is arranged at one end, far away from the prismatic cabin body 21, of the mounting seat 41 in a covering mode and used for preventing external seawater from entering the prismatic cabin body 21, the anti-spraying cover 42 is arranged on the outer pipe 322 in a covering mode, the outer pipe 322 is fixed on the mounting seat 41 through the anti-spraying cover 42, the anti-spraying cover 42 is in locking connection with the mounting seat 41 through a stop ring, a second through hole corresponding to the first through hole in position is formed in the anti-spraying cover 42, a third channel and a fourth channel are arranged in the anti-spraying cover 42, one end of the third channel is communicated with the first channel, the other end of the third channel can be communicated with the inner pipe 321, one end of the fourth channel is communicated with the second channel, and the other end of the fourth channel can be communicated with the inner pipe 321.

Specifically, the blowout preventer 42 is locked with the mounting seat 41 by a snap ring. The shape of the blowout preventer 42 is the same as that of the mounting base 41, one end of the blowout preventer 42 is a closed end, and the other end is an open end, and the blowout preventer 42 is installed on the mounting base 41 through the open end.

The mount 41 is provided therein with a first passage and a second passage, which are arranged along the axial direction of the mount 41, as shown in fig. 8.

In this embodiment, the first pipeline 52 is connected to the first channel in an inserting manner, and the second pipeline 53 is connected to the second channel in an inserting manner.

The blowout preventer 42 is provided with a third passage and a fourth passage, which are arranged along the radial direction of the blowout preventer 42, as shown in fig. 8.

When it is necessary to supply the chemical to the inner pipe 321 of the pipe string 32, the first line 52 supplies the chemical to the inner pipe 321 through the first and third passages, and when it is necessary to inject the chemical into the pipe string 32, the second line 53 supplies the high-pressure fluid to the inner pipe 321 through the second and fourth passages.

The inner blow out preventer assembly 43 functions to close the outer wall of the tubing string and also to guide the tubing string 32 into the containment chamber 2.

Inner blowout preventer assembly 43 includes a flange base 431, a plurality of lotus-shaped petals 432, and a plurality of web-shaped petals 433, flange base 431 is bolted to mount 41, and flange base 431 is coaxially arranged with mount 41.

The plurality of lotus-shaped claw flaps 432 and the plurality of web-shaped claw flaps 433 are arranged along the circumferential direction of the flange base 431, and the lotus-shaped claw flaps 432 and the web-shaped claw flaps 433 are arranged at intervals, that is, the lotus-shaped claw flaps 432, the web-shaped claw flaps 433, … …, the lotus-shaped claw flaps 432, and the web-shaped claw flaps 433 are sequentially arranged in the circumferential direction of the flange base 431.

The end with the larger size of the lotus-shaped claw piece 432 is connected with the flange base 431 through an elastic hinge, the end with the smaller size of the lotus-shaped claw piece 432 is a free end and can be attached to the outer wall of the outer pipe 322, and the lotus-shaped claw piece 432 cannot stretch along the circumferential direction of the flange base 431 and can only move along the direction vertical to the axis of the flange base 431; one end of web-shaped jaw piece 433 is connected with flange base 431 through an elastic hinge, the other end of web-shaped jaw piece 433 is a free end, the free end of web-shaped jaw piece 433 or the web-shaped jaw piece 433 as a whole can stretch along the circumferential direction of flange base 431, the free end of web-shaped jaw piece 433 can be attached to the outer wall of outer tube 322, and web-shaped jaw piece 433 not only can stretch along the circumferential direction of flange base 431, but also can move along the direction perpendicular to the axis of flange base 431.

Web-shaped jaw 433 can be extended or contracted along the circumferential direction of flange base 431, and a force moving toward the axial direction of outer tube 322 is applied to lotus-shaped jaw 432, so that lotus-shaped jaw 432 can be ensured to be attached to the outer wall of outer tube 322.

A hole for the pipe column 32 to pass through is formed between the free end of the web-shaped jaw 433 and the free end of the lotus-shaped jaw 432, the pipe column 32 passes through the hole formed by the free end of the web-shaped jaw 433 and the free end of the lotus-shaped jaw 432 to spread the web-shaped jaw 433, and applies a force to the lotus-shaped jaw 432 to move towards the direction away from the axis of the pipe column 32, so that the aperture of the hole formed between the free end of the web-shaped jaw 433 and the free end of the lotus-shaped jaw 432 is enlarged, the lotus-shaped jaw 432 is attached to the outer wall of the pipe column 32, and simultaneously, the free end of the web-shaped jaw 433 is also attached to the outer wall of the pipe column 32.

The blowout preventer 43 disclosed in the present embodiment is a low-pressure-difference blowout preventer 43, which can achieve sealing of the outer wall of the tubular string 32 under the action of low-pressure gas in the containment chamber 2.

In order to reduce the pipeline quantity between the semi-submersible type ship body 1 and the leakproof cabin 2 in the scheme, the semi-submersible type ship body 1 is connected with the leakproof cabin 2 through the umbilical cable 5. The umbilical 5 comprises a first pipeline 52, a second pipeline 53, an air pipeline 51 and a heat tracing cable 54, wherein the first pipeline 52, the second pipeline 53, the air pipeline 51 and the heat tracing cable 54 are integrally arranged in the umbilical 5. Correspondingly, the lower ends of the first and

second pipes

52, 53 are also mounted on the top of the containment tank 2 through the umbilical mount and extend into the containment tank 2, and the lower ends of the first and

second pipes

52, 53 are respectively communicated with the first and

second pipes

52, 53.

The heat tracing cable 54 is used for heating and insulating the gas transmission pipeline 51.

In the present solution, the gas pipe 51, the first pipe 52, the second pipe 53 and the heat tracing cable 54 all have redundancies.

The umbilical 5 includes a gathering line 51, a heat tracing cable 54, a tensile fiber filler material, and a tensile, compressive armor. Specifically, tensile resistance to compression armor is located outmost, and gathering pipeline 51, heat tracing cable 54 and tensile fibre filler material all are located tensile resistance to compression armor, fill tensile fibre filler material between gathering pipeline 51 and the heat tracing cable 54 for fill the inner space of umbilical 5, improve umbilical 5's intensity. The power cables are used to power the electromechanical components on the containment vessel 2 and are redundant.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A semi-submersible mining device is characterized by comprising a semi-submersible ship body (1), a leakproof cabin (2), an umbilical cable (5) and a mining pipe column (3),

the semi-submersible hull (1) can be located below the sea surface;

the umbilical cable (5) is used for communicating the leakproof cabin (2) with the semi-submersible hull (1);

the production string (3) can be left in a wellbore of a gas hydrate formation as a production string;

the lower end of the leakproof cabin (2) is an open end, the leakproof cabin (2) is arranged on the natural gas hydrate stratum through an open end cover and can isolate the natural gas hydrate stratum within the coverage range of the leakproof cabin (2) from external seawater, the leakproof cabin (2) is connected with the upper end of the exploitation tubular column (3) through a blowout preventer (4), the leakproof cabin (2) is connected with the umbilical cable (5) through an umbilical cable mounting seat, and the leakproof cabin is used for gathering gas exploited by the exploitation tubular column (3) and gas released by the natural gas hydrate stratum covered by the leakproof cabin (2),

the leakproof cabin (2) comprises a prismatic cabin body (21) and a sealing base (22),

the upper end of the prismatic cabin body (21) is provided with a pyramidal top, the pyramidal top is connected with the umbilical (5) through an umbilical mounting seat, the pyramidal top is connected with the production string (3) through the blowout preventer (4), and the lower end of the prismatic cabin body (21) is an open end;

the sealing bases (22) are connected with the open end of the prismatic tank body (21) and used for realizing the sealing between the open end of the prismatic tank body (21) and the natural gas hydrate formation, the number of the sealing bases (22) is equal to the number of prismatic surfaces of the prismatic tank body (21), and the sealing bases (22) can be sunk on the natural gas hydrate formation,

the number of the leakproof cabins (2) is multiple, the sealing base (22) is arranged at the open end of each leakproof cabin (2), and the adjacent leakproof cabins (2) are connected through the sealing bases (22);

the production string (3) comprising a drilling tool (31) and a string (32), the string (32) being connected to the containment tank (2) through the blowout preventer (4),

said drilling tool (31) comprising a rotary jet drill bit (311) and a bottom hole motor (312), said bottom hole motor (312) being connected to said rotary jet drill bit (311),

the pipe column (32) comprises an inner pipe (321), an outer pipe (322) and a sieve pipe (323), the inner pipe (321), the outer pipe (322) and the sieve pipe (323) are all flexible pipes, one end of the outer pipe (322) is connected with the prismatic cabin body (21) through the blowout preventer (4), the other end of the outer pipe (322) is connected with the sieve pipe (323), the sieve pipe (323) is connected with the shell of the well bottom power drilling tool (312), the inner pipe (321) is positioned in the outer pipe (322) and the sieve pipe (323), a back pressure valve is arranged in the inner pipe (321), the back pressure valve is positioned below a ball throwing release, and the other end of the inner pipe (321) is communicated with a high-pressure fluid inlet of the well bottom power drilling tool (312),

and filling layers (324) are respectively arranged between the inner pipe (321) and the outer pipe (322) and between the inner pipe (321) and the sieve tube (323), the inner pipe (321) and the outer pipe (322) and the inner pipe (321) and the sieve tube (323) are connected through the filling layers (324), and the filling layers (324) are used for filtering sand grains decomposed from natural gas hydrate.

2. Semi-submersible mining apparatus according to claim 1, characterized in that the sealing mounts (22) are elastomer mounts, with a sealing connection between adjacent ones of the elastomer mounts.

3. Semi-submersible production device according to claim 1, characterised in that an electric heater is embedded in the filling layer between the screen pipe (323) and the inner pipe (321) for providing heat for the decomposition of the gas hydrates, and the electric heater is connected with a power supply through a heating cable.

4. Semi-submersible production plant according to claim 3, characterized in that the closed end of the prismatic tank (21) is provided with mounting holes for mounting the blowout preventer (4), the blowout preventer (4) comprising an outer blowout preventer assembly mounted outside the prismatic tank (21) and an inner blowout preventer assembly (43), the inner blowout preventer assembly (43) being mounted inside the prismatic tank (21),

the outer blowout preventer assembly comprises a mounting seat (41) and a blowout preventer (42),

the mounting seat (41) is mounted outside the prismatic cabin body (21) and corresponds to the mounting hole in position, a first through hole for the outer pipe (322) to pass through is formed in the mounting seat (41), a first channel and a second channel are arranged in the mounting seat (41), the first channel can be communicated with a first pipeline (52) used for supplying a chemical agent in the umbilical cable (5), and the second channel can be communicated with a second pipeline (53) used for supplying a high-pressure fluid in the umbilical cable (5);

the anti-spraying cover (42) is covered at one end, far away from the prismatic cabin body (21), of the mounting seat (41) and used for preventing external seawater from entering the prismatic cabin body (21), the anti-spraying cover (42) is sleeved on the outer pipe (322), the outer pipe (322) is fixed on the mounting seat (41) through the anti-spraying cover (42), the anti-spraying cover (42) is in locking connection with the mounting seat (41) through a stop ring, a second through hole corresponding to the first through hole in position is formed in the anti-spraying cover (42), a third channel and a fourth channel are arranged in the anti-spraying cover (42), one end of the third channel is communicated with the first channel, the other end of the third channel can be communicated with the inner pipe (321), one end of the fourth channel is communicated with the second channel, and the other end of the fourth channel can be communicated with the inner pipe (321);

the inner blowout preventer assembly (43) comprises a flange base (431), a plurality of lotus-shaped claws (432) and a plurality of web-shaped claws (433), the flange base (431) is arranged coaxially with the mounting seat (41), the plurality of lotus-shaped claws (432) and the plurality of web-shaped claws (433) are arranged along the circumferential direction of the flange base (431) and the lotus-shaped claws (432) and the web-shaped claws (433) are arranged at intervals, one ends of the plurality of lotus-shaped claws (432) and the plurality of web-shaped claws (433) are connected with the flange base (431) by elastic hinges, one ends of the plurality of lotus-shaped claws (432) and the plurality of web-shaped claws (433) away from the flange base (431) are free ends, the free ends of the plurality of lotus-shaped claws (432) and the web-shaped claws (433) are capable of telescoping in the circumferential direction of the flange base (431), the free ends of the web-shaped claws (433) are capable of telescoping along the circumferential direction of the flange base (431) and bring the ends of the lotus-shaped claws (432) connected with the outer wall of the hinge into contact with the inner wall of the plurality of web-shaped claws (322) and the elastic hinges, and the gas pressure of the inner wall of the web-shaped claws (432) acts in the longitudinal direction of the flange base (431) together.

5. Semi-submersible production plant according to claim 4, characterized in that the umbilical (5) further comprises a gas line (51) for conveying gas in the containment tank (2) to the semi-submersible hull (1) and a heat tracing cable (54) for heating the gas line (51).