A gas hydrate coring drill and method

Abstract

The application provides a natural gas hydrate freezing coring drill, which comprises an outer pipe assembly provided with a drill bit at a lower end and an inner pipe assembly arranged in the outer pipe assembly and used for freezing collection of natural gas hydrate, and the inner pipe assembly comprises, from top to bottom, a spear head, a hovering mechanism, a single-acting mechanism, a refrigeration mechanism and a freezing coring chamber; the outlet of the lower liquid passage is blocked by the pedestal, at this time, the pressure in the circulating cavity is increased, the piston column is pushed to move downward, the piston column continues to push the transmission column to move downward after moving downward by a distance, the isolation membrane at the lower end of the transmission column is broken by the cone head during the downward movement of the transmission column, the first channel and the second channel are conducted, the heat carrier stored in the refrigerant storage tank enters the refrigeration cavity to be mixed with the cold source, and the heat carrier and the cold source are mixed to start refrigeration of the core tube, and the application solves the problems of the prior art, such as complex structure of the freezing coring drill, complicated coring steps, processes and principles, and poor work reliability and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas hydrate freezing coring drill, in particular to a natural gas hydrate freezing coring drill and a coring method. BACKGROUND

[0002] The core is the geological data necessary to obtain in the process of natural gas hydrate exploration and development, and the qualitative and quantitative analysis of the hydrate core is the prerequisite for evaluating hydrate resource reserves, reasonably formulating hydrate drilling and production schemes and increasing production schemes; in addition to implementing geophysical prospecting, it is necessary to sample and analyze various indicators from the target stratum to master the hydrate occurrence characteristics (gas and water distribution) and hydrate reservoir characteristics (permeability, porosity and other physical parameters) when searching for natural gas hydrate on the seabed. It can be said that the observation and research of the core are necessary at each stage of natural gas hydrate exploration and development.

[0003] Natural gas hydrate mainly occurs in underground high-pressure and low-temperature environment, and requires very low environmental temperature for stable existence under normal pressure. Therefore, there are mainly two ways of hydrate core sampling: one is pressure and temperature preservation coring, and the other is bottom freezing coring. For the first coring method, after the core is drilled underground, the pressure sealing of the coring chamber is realized through the ball valve or the plate valve; the sealing accuracy of the ball valve or the plate valve is very high, and the failure rate of the core in the field engineering is high. For the bottom freezing coring method, when the core enters the coring chamber at the bottom of the hole, the self-protection effect of the hydrate under the low-temperature environment of the hydrate is fully utilized by injecting the refrigerant (generally alcohol) into the coring chamber to achieve the purpose of coring; the success rate of the method is higher than that of the pressure preservation coring method. However, the existing patents of hydrate freezing coring drill mainly use mechanical force generated by the structure of the drill to send the refrigerant (generally alcohol) and the cold source into the coring chamber to freeze the hydrate core, and there are few hole-bottom freezing drills with gas / liquid force-mechanical combined transmission.

[0004] The existing patent application No. CN201811016786.0 proposes a marine natural gas hydrate phase change refrigeration wireline coring drill and a coring method, which uses liquid force-mechanical combined drive refrigerant to achieve freezing in the coring chamber, but the drill structure is relatively complex, the coring steps, processes and principles are relatively complicated, and the working reliability and stability are poor. SUMMARY

[0005] The present application aims to provide a natural gas hydrate freezing coring drill and a coring method, which solves the problems of the existing freezing coring drill, such as complex structure, complicated coring steps, processes and principles, and poor working reliability and stability.

[0006] The embodiments of the present invention are achieved through the following technical solutions: a natural gas hydrate cryogenic coring drill, comprising an outer tube assembly with a drill bit at the lower end and an inner tube assembly disposed inside the outer tube assembly, for cryogenic collection of natural gas hydrate, wherein the inner tube assembly comprises, from top to bottom, a retrieval head, a hovering mechanism, a single-action mechanism, a refrigeration mechanism and a cryogenic coring chamber;

[0007] The refrigeration mechanism includes a perforated connector, a refrigerant protection outer pipe, a refrigerant storage tank, a transmission column, a support base, and a through-hole connector. The upper and lower ends of the refrigerant protection outer pipe are respectively connected to the perforated connector and the through-hole connector. The upper end of the perforated connector is connected to the single-action mechanism, and the lower end of the through-hole connector is connected to the cryogenic core extraction chamber.

[0008] The refrigerant storage tank and the support base are both installed inside the refrigerant protection outer pipe. The upper end of the refrigerant storage tank abuts against the perforated connecting seat, the lower end of the refrigerant storage tank is connected to the upper end of the support base, and the lower end of the support base abuts against the through hole connecting seat.

[0009] The perforated connector, refrigerant storage tank, support base, and through-hole connector are all vertically opened and coaxially connected through holes. The transmission column slides through the through holes opened by the refrigerant storage tank and the support base. A first channel is opened on the transmission column. The upper end of the first channel is connected to the inner cavity of the refrigerant storage tank, and the lower end of the first channel is connected to the lower end of the transmission column. An isolation membrane is provided on the lower end surface of the transmission column.

[0010] A cone head is provided inside the through hole of the through hole connector. The cone head is located below the isolation membrane and a second channel is provided on the cone head.

[0011] The cryogenic core extraction chamber includes a refrigerant storage tube, a core tube, and a snap ring seat. The upper and lower ends of the refrigerant storage tube are respectively connected to the through hole connector and the snap ring seat. The core tube is coaxially arranged inside the refrigerant storage tube. A cooling cavity is formed between the refrigerant storage tube, the core tube, the through hole connector, and the snap ring seat. The cooling cavity is connected to the second channel.

[0012] The refrigerant storage tank stores a refrigerant, and the refrigeration chamber is equipped with a cold source;

[0013] It also includes a drive mechanism for pushing the transmission column to move vertically.

[0014] Furthermore, the single-action mechanism includes a first perforated bearing seat; the drive mechanism includes a mud circulation joint and a piston rod, the mud circulation joint has a circulation chamber inside, and the mud circulation joint has a plurality of upper liquid passage holes and a plurality of lower liquid passage holes spaced apart vertically, the upper liquid passage holes and the lower liquid passage holes are all connected to the circulation chamber;

[0015] The mud circulating joint bottom is connected with the first perforated bearing seat, the first perforated bearing seat is vertically provided with a piston cavity, the piston cavity is communicated with the circulating cavity, the piston column is slidably arranged in the piston cavity, and the lower end of the piston column is coaxially arranged with the transmission column and is spaced apart from the transmission column;

[0016] The suspension mechanism comprises a pedestal and a suspension ring, the pedestal is arranged in the outer pipe assembly, the suspension ring is arranged on the outer wall of the mud circulating joint, the suspension ring is located between the upper liquid passage and the lower liquid passage, the suspension ring is in abutment with the pedestal, and the pedestal is in sliding fit with the mud circulating joint.

[0017] Further, the top of the mud circulating joint is connected with the spear head.

[0018] The suspension mechanism further comprises a bearing ring and an elastic buckle, the bearing ring is arranged on the mud circulating joint, and the bearing ring is located above the suspension ring.

[0019] A plurality of elastic buckles are arranged around the inner portion of the outer pipe assembly, the elastic buckles are matched with the top of the bearing ring, and the elastic buckles are used for providing downward force to the mud circulating joint.

[0020] Further, the spear head is provided with an unlocking sleeve, the outer diameter of the spear head is smaller than the outer diameter of the mud circulating joint.

[0021] The unlocking sleeve is provided with a limiting portion at the top, a sliding hole is formed in the limiting portion, and the sliding hole is in gap fit with the spear head.

[0022] The inner cavity of the unlocking sleeve is in sliding fit with the bearing ring and the suspension ring.

[0023] The outer wall of the unlocking sleeve is in sliding fit with the outer pipe assembly and the elastic buckle.

[0024] Further, the single-acting mechanism further comprises a second perforated bearing seat, a first single-acting bearing, a second single-acting bearing, a buffer spring, a spring stopper, a gasket and a stop nut, the first perforated bearing seat is sequentially provided with a first stepped portion and a second stepped portion from top to bottom, the first single-acting bearing and the second single-acting bearing are respectively sleeved on the first stepped portion and the second stepped portion.

[0025] The inner cavity of the second perforated bearing seat is sequentially provided with a first stepped portion, a second stepped portion and a third stepped portion from top to bottom, the inner cavity diameter of the third stepped portion is greater than the inner cavity diameter of the second stepped portion, the first stepped portion is matched with the first single-acting bearing, and the second stepped portion is matched with the second single-acting bearing.

[0026] The buffer spring is sleeved on the second step of the first perforated bearing seat. The lower end of the second step is fitted with a spring stop and a washer from top to bottom, and is threadedly connected to the stop nut.

[0027] The upper and lower ends of the buffer spring abut against the third step and the spring stop, respectively;

[0028] The lower end of the second perforated bearing housing is connected to the perforated connecting seat.

[0029] Furthermore, it also includes a first sealing ring, a second sealing ring, and a third sealing ring, wherein the first sealing ring is disposed between the piston rod and the piston chamber;

[0030] The second sealing ring is disposed between the transmission column and the through hole at the upper end of the refrigerant storage tank;

[0031] The third sealing ring is disposed between the through hole on the transmission column and the support base.

[0032] Furthermore, it also includes a mud check valve, through which the upper end of the core tube is unidirectionally connected to the cavity between the refrigerant storage pipe and the outer pipe assembly.

[0033] Furthermore, it also includes a gas one-way valve, wherein a gas guide hole is radially provided on the through hole connector, the gas guide hole is connected to the through hole below the cone head, and the gas one-way valve is embedded in the gas guide hole.

[0034] Furthermore, the inner wall of the refrigerant storage pipe is provided with an insulation layer.

[0035] Furthermore, a method for cryogenic coring of natural gas hydrates, employing a natural gas hydrate cryogenic coring drill, includes the following steps:

[0036] S1. Core drilling: During the drilling process in the natural gas hydrate layer, the drill bit is carried by the outer tube assembly. Natural gas hydrate continuously enters the core tube, and useless mud and other substances inside the core tube are discharged from the mud check valve.

[0037] S2. After the core tube is filled with natural gas hydrate, stop drilling, but maintain the circulation of mud at the bottom of the hole. At this time, when the drilling fluid passes through the platform, it enters the circulation chamber through several upper fluid passages, and then enters the cavity between the inner tube assembly and the outer tube assembly below the platform through several lower fluid passages.

[0038] S3. Raise the inner tube assembly until the lower fluid passage is level with the platform, that is, the outlet of the lower fluid passage is blocked by the platform. Since the drilling fluid is still being injected downwards, the pressure inside the circulation chamber increases, which in turn pushes the piston column to move downwards.

[0039] S4, the piston column moves down a distance and abuts with the transmission column, continues to push the transmission column to move down, the transmission column moves down in the process to make the isolation membrane at the lower end of the cone head to be broken by the cone, make the first channel and the second channel conductive, and then make the refrigerant storage tank in the refrigeration cavity store the load refrigerant into the refrigeration cavity and mix with the cold source, the load refrigerant and the cold source mix to start refrigeration of the core tube, and the volatilized gas is discharged from the gas one-way valve;

[0040] S5, when the isolation membrane is broken, and then the refrigerant storage tank and the refrigeration cavity are conductive, the inner tube assembly is reset, the upper liquid hole and the lower liquid hole are conductive, the drilling fluid is circulated until the freezing of the core tube is completed.

[0041] S6, the tripping sleeve is lowered from the outer tube assembly, the tripping sleeve is sleeved on the mud circulating joint under the action of gravity and the drilling fluid, until abutting with the pedestal, at this time the elastic buckle is extruded by the tripping sleeve, and then the elastic buckle is separated from the bearing ring, and the inner tube assembly and the tripping sleeve are taken out from the outer tube assembly by the fishing tool, and the sampled core sample is stored in a high-pressure low-temperature container.

[0042] The technical scheme of the embodiment of the application has at least the following advantages and beneficial effects:

[0043] 1. The inner tube assembly is lifted until the lower liquid hole is level with the pedestal, that is, the outlet of the lower liquid hole is blocked by the pedestal, the internal pressure of the circulating cavity increases due to the continuous pouring of the drilling fluid downward, and then the piston column is pushed to move downward, the piston column abuts with the transmission column after moving downward for a distance, the transmission column continues to move downward, the isolation membrane at the lower end of the transmission column is broken by the cone head in the process of moving downward, the first channel and the second channel are conductive, and then the refrigerant storage tank in the refrigeration cavity stores the load refrigerant into the refrigeration cavity and mixes with the cold source, the load refrigerant and the cold source mix to start refrigeration of the core tube, and the core integrity can be well protected during drilling and coring, and the freezing efficiency is high.

[0044] 2. When the core tube is frozen, the entire inner tube assembly is lifted, the tripping sleeve is released, the elastic buckle is removed from the bearing ring in the process of falling of the structure sleeve, and then the elastic lock plate is attached to the wall of the outer tube assembly, the tripping sleeve can be wrapped on the hanging ring, and then the entire inner tube assembly can be smoothly lifted, the elastic buckle and the tripping sleeve are matched to assist the recovery and lowering of the inner tube assembly, the structure of the drilling tool is simplified, and the reliability is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0046] Figure 1 A structure diagram of a natural gas hydrate frozen coring drill provided by the present application;

[0047] Figure 2 A structure diagram of a natural gas hydrate frozen coring drill provided by the present application; Figure 1 An enlarged structure diagram of the structure at A in the present application;

[0048] Figure 3 A structure diagram of a natural gas hydrate frozen coring drill provided by the present application; Figure 1 An enlarged structure diagram of the structure at B in the present application;

[0049] Figure 4 A structure diagram of a natural gas hydrate frozen coring drill provided by the present application;

[0050] Figure legend: 1, drill bit, 2, outer pipe assembly, 3, inner pipe assembly, 31, spear head,

[0051] 32, hovering mechanism, 321, pedestal, 322, suspension ring, 323, bearing ring, 324, elastic buckle,

[0052] 33, single-action mechanism, 331, first hole bearing seat, 3311, piston cavity, 3312, first step part, 3313, second step part, 332, second hole bearing seat, 3321, first step part, 3322, second step part, 3323, third step part, 3324, oil nozzle, 333, first single-action bearing, 334, second single-action bearing, 335, buffer spring, 336, spring stopper, 337, gasket, 338, stop nut,

[0053] 34, refrigeration mechanism, 341, hole connecting seat, 342, refrigerant protection outer pipe, 343, refrigerant storage tank, 344, transmission column, 3441, first channel, 345, support seat, 346, through-hole handle, 3461, gas guide hole, 347, second sealing ring, 348, third sealing ring, 349, gas one-way valve,

[0054] 35, frozen core chamber, 351, refrigerant storage pipe, 352, core pipe, 353, clasp seat, 354, refrigeration cavity, 355, mud one-way valve, 356, heat preservation layer, 357, support ring,

[0055] 36, driving mechanism, 361, mud circulating joint, 3611, circulating cavity, 3612, upper liquid passage, 3613, lower liquid passage, 362, piston column, 363, first sealing ring,

[0056] 37, isolation film, 38, cone head, 381, second channel, 4, trip sleeve, 41, limiting portion, 411, sliding hole. DETAILED DESCRIPTION

[0057] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0058] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0059] Reference Figures 1 to 4 As shown in the drawings, the present embodiment provides a natural gas hydrate frozen coring drill, comprising an outer pipe assembly 2 provided with a drill bit 1 at a lower end and an inner pipe assembly 3 arranged inside the outer pipe assembly 2, for frozen collection of natural gas hydrate, the inner pipe assembly 3 comprises, from top to bottom, a spear head 31, a hovering mechanism 32, a single-acting mechanism 33, a refrigeration mechanism 34 and a frozen coring chamber 35 in sequence;

[0060] The refrigeration mechanism 34 comprises a hole connecting seat 341, a refrigerant protection outer pipe 342, a refrigerant storage tank 343, a transmission column 344, a support seat 345 and a through-hole handle 346, the upper and lower ends of the refrigerant protection outer pipe 342 are connected with the hole connecting seat 341 and the through-hole handle 346 respectively, the upper end of the hole connecting seat 341 is connected with the single-acting mechanism 33, and the lower end of the through-hole handle 346 is connected with the frozen coring chamber 35.

[0061] The refrigerant storage tank 343 and the support seat 345 are both arranged in the refrigerant protection outer pipe 342, the upper end of the refrigerant storage tank 343 abuts against the hole connecting seat 341, the lower end of the refrigerant storage tank 343 is connected with the upper end of the support seat 345, and the lower end of the support seat 345 abuts against the through-hole handle 346, as shown in the drawings. Figure 3 As shown in the drawings, the refrigerant storage tank 343 is fixed inside the refrigerant protection outer pipe 342 to prevent it from shaking, thereby providing a basis for subsequent movement of the transmission column 344.

[0062] More specifically, as shown in Figures 1-3 The through hole connector 341, the refrigerant storage tank 343, the support seat 345 and the through hole handle 346 are vertically provided with coaxially communicated through holes, the transmission column 344 is slidably arranged in the through holes of the refrigerant storage tank 343 and the support seat 345, the first channel 3441 is provided on the transmission column 344, the upper end of the first channel 3441 is communicated with the inner cavity of the refrigerant storage tank 343, the lower end of the first channel 3441 is communicated with the lower end of the transmission column 344, and the isolation film 37 is arranged on the lower end surface of the transmission column 344;

[0063] The through hole of the through hole handle 346 is provided with the tapered head 38, the tapered head 38 is located below the isolation film 37, and the second channel 381 is provided on the tapered head 38;

[0064] In specific implementation, the isolation film 37 is used to block the lower end of the first channel 3441 to prevent the cold carrier in the refrigerant storage tank 343 from overflowing, when the transmission column 344 moves downward to drive the isolation film 37 to move downward, until the isolation film is pierced by the tapered head 38, the second channel 381 is communicated with the first channel 3441, and the cold carrier in the refrigerant storage tank 343 enters the frozen core chamber.

[0065] More specifically, the frozen core chamber 35 comprises the refrigerant storage tube 351, the core tube 352 and the snap spring seat 353, the upper and lower ends of the refrigerant storage tube 351 are connected with the through hole handle 346 and the snap spring seat 353 respectively, the core tube 352 is coaxially and spacedly arranged in the refrigerant storage tube 351 and is fixed by the support ring 357 with a through hole by welding, the refrigerant storage tube 351, the core tube 352, the through hole handle 346 and the snap spring seat 353 form the refrigeration cavity 354, and the refrigeration cavity 354 is communicated with the second channel 381;

[0066] As shown in Figures 1-3 In specific implementation, the cold carrier in the refrigerant storage tank 343 enters the refrigeration cavity 354 formed between the refrigerant storage tube 351, the core tube 352, the through hole handle 346 and the snap spring seat 353 through the second channel 381, and the cold carrier is mixed with the cold source in the refrigeration cavity 354 to refrigerate the core tube 352, wherein the cold carrier is alcohol and the cold source is dry ice.

[0067] The refrigerant storage tank 343 stores the cold carrier, and the refrigeration cavity 354 is provided with the cold source; the above implementation steps are only described by taking alcohol+dry ice as an example; the cold carrier can also use other alcohol substances with low freezing points, such as ethylene glycol; the cold source can also use liquid nitrogen and other fluids that are easy to phase change as the cold source.

[0068] More specifically, the drive mechanism 36 is further included, and the drive mechanism 36 is used to push the transmission column 344 to move vertically.

[0069] The single-acting mechanism 33 comprises a first bearing seat with holes 331; the driving mechanism 36 comprises a mud circulating joint 361 and a piston column 362, the mud circulating joint 361 is internally provided with a circulating cavity 3611, a plurality of upper liquid passages 3612 and a plurality of lower liquid passages 3613 are spaced apart on the mud circulating joint 361, and the upper liquid passages 3612 and the lower liquid passages 3613 are in communication with the circulating cavity 3611; as shown in Figure 1 and 2 During normal drilling, drilling fluid enters the circulating cavity 3611 from the plurality of upper liquid passages 3612, and then is discharged from the lower liquid passages 3613, thereby enabling the drilling fluid to pass through the hovering mechanism 32 in this way.

[0070] The bottom of the mud circulating joint 361 is connected to the first bearing seat with holes 331, the first bearing seat with holes 331 is vertically provided with a piston cavity 3311, the piston cavity 3311 is in communication with the circulating cavity 3611, the piston column 362 is slidably arranged through the piston cavity 3311, the upper end of the piston column 362 extends into the circulating cavity 3611, and the lower end of the piston column 362 is coaxially and spaced apart from the transmission column 344, so that the piston column 362 does not affect the transmission column 244 during drilling rotation, thereby ensuring that the early-stage isolation membrane 37 is not affected; when the core barrel 352 is full and the refrigerant in the refrigerant storage tank 343 needs to enter the refrigeration cavity 354, only the lower liquid passages 3613 need to be properly blocked to increase the internal pressure of the circulating cavity 3611, and when a certain pressure is reached, the piston column 362 moves downward, abuts against the transmission column 344 after moving a distance, and continues to push the transmission column 344 to move, so that the isolation membrane 37 is pierced by the conical head 38.

[0071] The hovering mechanism 32 comprises a pedestal 321 and a suspension ring 322, the inner tube assembly 2 is internally provided with the pedestal 321, the mud circulating joint 361 is externally provided with the suspension ring 322, the suspension ring 322 is located between the upper liquid passages 3612 and the lower liquid passages 3613, the suspension ring 322 abuts against the pedestal 321, and the pedestal 321 is in sliding fit with the mud circulating joint 361, as shown in Figure 1 In specific implementation, the suspension ring 322 cooperates with the pedestal 321 to prevent the inner tube assembly 3 from falling, and when the circulating cavity 3611 needs to be pressurized, only the inner tube assembly 3 needs to be slightly lifted, so that the plurality of lower liquid passages 3613 are blocked by the pedestal 321.

[0072] More specifically, the top of the mud circulating joint 361 is connected to the spear head 31;

[0073] As shown in Figure 1 and 2 The hovering mechanism 32 further comprises a bearing ring 323 and an elastic buckle 324, the bearing ring 323 is arranged on the mud circulating joint 361, and the bearing ring 323 is located above the suspension ring 322.

[0074] The outer tube assembly 2 is internally provided with a plurality of elastic buckles 324, which are matched with the top of the bearing ring 323, and are used to provide downward force to the mud circulating joint 361, so as to provide thrust to the inner tube assembly 3 during drilling core, and make the sample smoothly enter the core barrel 352.

[0075] As shown in Figure 1 and 4 , the outer diameter of the spear head 31 is smaller than the outer diameter of the mud circulating joint 361, and the outer tube assembly 2 is internally provided with a plurality of elastic buckles 324, which are matched with the top of the bearing ring 323, and are used to provide downward force to the mud circulating joint 361, so as to provide thrust to the inner tube assembly 3 during drilling core, and make the sample smoothly enter the core barrel 352.

[0076] The top of the release sleeve 4 is provided with a limiting portion 41, and a sliding hole 411 is formed in the limiting portion 41 and is matched with the spear head 31 in a gap manner.

[0077] The inner cavity of the release sleeve 4 is slidably matched with the bearing ring 323 and the suspension ring 322.

[0078] The outer wall of the release sleeve 4 is slidably matched with the outer tube assembly 2 and the elastic buckle 324. The elastic buckle 324 is connected with the outer tube assembly 2 at one end of the elastic locking piece, and extends obliquely downward at the other end. The elastic locking piece itself has elasticity, and the free end thereof can extend to the axis of the outer tube assembly 2 in a normal state. The suspension ring 322 and the bearing ring 323 can pass through the elastic locking piece. When the suspension ring 322 abuts against the pedestal 321, the free end of the elastic locking piece points to the upper end surface of the bearing ring 323, so that downward force can be provided to the entire inner tube assembly 3 through the bearing ring 323 during drilling.

[0079] When the core barrel 352 is frozen and the entire inner tube assembly 3 needs to be pulled out, the release sleeve 4 is released. During the falling of the structure sleeve 4, the abutting force of the elastic buckle 324 on the bearing ring 323 is released, so that the elastic locking piece is attached to the wall of the outer tube assembly 2, the release sleeve can be wrapped on the suspension ring 322, and then the entire inner tube assembly 3 can be smoothly pulled out.

[0080] The elastic buckle 324 and the release sleeve 4 are matched to assist in the recovery and lowering of the inner tube assembly 3, which simplifies the structure of the drilling tool and further improves the reliability.

[0081] As shown in Figure 1 and 2 , the single-action mechanism 33 further includes a second hole-bearing seat 332, a first single-action bearing 333, a second single-action bearing 334, a buffer spring 335, a spring stopper 336, a gasket 337, and a stop nut 338. The first hole-bearing seat 331 is provided with a first stepped portion 3312 and a second stepped portion 3313 from top to bottom, and the first single-action bearing 333 and the second single-action bearing 334 are respectively sleeved on the first stepped portion 3312 and the second stepped portion 3313.

[0082] More specifically, the inner cavity of the second hole bearing seat 332 is sequentially provided with a first step portion 3321, a second step portion 3322 and a third step portion 3323 from top to bottom, and the inner cavity diameter of the third step portion 3323 is greater than that of the second step portion 3322; the first step portion 3321 is matched with the first single-acting bearing 333, and the second step portion 3322 is matched with the second single-acting bearing 334;

[0083] The buffer spring 335 is sleeved on the second step portion 3313 of the first hole bearing seat 331, the second step portion 3313 is sequentially sleeved with a spring stopper 336 and a gasket 337 from top to bottom at the lower end, and is threadedly connected with a stop nut 338;

[0084] The upper and lower ends of the buffer spring 335 are respectively abutted against the third step portion 3323 and the spring stopper 336;

[0085] The lower end of the second hole bearing seat 332 is connected with a hole connecting seat 341.

[0086] In specific implementation, the first hole bearing seat 331 is rotationally connected with the second hole bearing seat 332 through the first single-acting bearing 333 and the second single-acting bearing 334, and the first hole bearing seat 331 and the second hole bearing seat 332 can be elastically sleeved through the buffer spring 335, so that the first hole bearing seat 331 can keep relative rotation with the second hole bearing seat 332 during rotation of the outer pipe assembly 2, and the action force between the two can be reduced in the longitudinal direction through the buffer spring 335.

[0087] More specifically, the first single-acting bearing 333 and the second single-acting bearing 334 are lubricated by adding lubricating oil through the oil nozzle 3324.

[0088] As shown in Figures 1-3 It also includes a first sealing ring 363, a second sealing ring 347 and a third sealing ring 348, the first sealing ring 363 is arranged between the piston column 362 and the piston cavity 3311, which can prevent liquid leakage and provide certain resistance to the piston column 362 to prevent the piston column 362 from falling without being driven by pressure;

[0089] The second sealing ring 347 is arranged between the transmission column 344 and the through hole at the upper end of the refrigerant storage tank 343;

[0090] The third sealing ring 348 is arranged between the transmission column 344 and the through hole on the support seat 345, and in specific implementation, the second sealing ring 347 and the third sealing ring 348 are mainly used to prevent liquid leakage.

[0091] As shown in Figure 1 and 3As shown, the mud one-way valve 355 is arranged on the upper end of the core tube 352, and the core tube 352 is in one-way communication with the cavity between the refrigerant storage tube 351 and the outer tube assembly 2 through the mud one-way valve 355. During the process of continuously loading the core sample in the core tube 352, the useless liquid substances such as mud originally in the core tube 352 are discharged through the mud one-way valve 355, and the mud one-way valve 355 can prevent the external drilling fluid from entering the core tube 352.

[0092] The gas one-way valve 349 is further arranged, and the gas guide hole 3461 is radially arranged on the upper end of the through-hole adapter 346, and the gas guide hole 3461 is in communication with the through-hole below the cone head 38. The gas one-way valve 349 is embedded in the gas guide hole 3461, as shown in Figure 1 and 3 As shown, in the specific implementation, the gas one-way valve 349 is used to discharge the gas generated after the reaction of the refrigerant and the cold source, so that the internal pressure of the refrigeration cavity 354 is maintained normal, and the external drilling fluid is prevented from entering the refrigeration cavity 354.

[0093] More specifically, the inner wall of the refrigerant storage tube 351 is provided with a heat preservation layer 356 for preventing the external heat from entering, so as to ensure the refrigeration effect after the reaction of the cold source and the refrigerant.

[0094] A natural gas hydrate freezing coring method adopts a natural gas hydrate freezing coring drilling tool, and includes the following steps:

[0095] The clasp spring seat 353 is removed on the ground, dry ice is put into the refrigeration cavity 354 of the refrigerant storage tube 351, and then the clasp spring and the clasp spring seat 353 are assembled, so that the refrigeration cavity 354 is kept sealed;

[0096] The through-hole adapter 346 is removed, the refrigerant alcohol is injected into the refrigerant storage tank 343 along the first channel 3441, the isolation film 37 is sleeved and fixed at the lower end of the transmission column 344 after the injection is completed, then the through-hole adapter 346 is assembled with the refrigerant protection outer tube 342, and the refrigerant storage tube 351 is assembled and connected;

[0097] Then, the spear head 31, the mud circulating joint 361, the first bearing seat 331 with holes, the piston column 362, the connecting seat 341 with holes and the like are connected together to form the entire inner tube assembly 3.

[0098] The inner tube assembly 3 is lowered, the suspension ring 322 and the bearing ring 323 are sequentially compressed and pass through the elastic buckle 324, until the suspension ring 322 is seated on the pedestal 321, so that the gap between the clasp spring seat 353 and the drill bit 1 is about 3 mm, and the circulation of the drilling fluid is ensured.

[0099] During the drilling process of the drill bit 1 in the natural gas hydrate layer by the outer pipe assembly 2, the natural gas hydrate continuously enters into the core tube 352, and the useless mud and other substances inside the core tube 352 are discharged from the mud one-way valve 355;

[0100] After the core tube 352 is filled with the natural gas hydrate, the drilling is stopped, but the circulation of the mud at the bottom of the hole is maintained, at this time, the drilling fluid enters into the circulation cavity 3611 from the upper liquid holes 3612 of the seat 321, and then enters into the cavity between the inner pipe assembly 3 and the outer pipe assembly 2 below the seat 321 from the lower liquid holes 3613;

[0101] The inner pipe assembly 3 is lifted until the lower liquid holes 3613 are leveled with the seat 321, that is, the outlet of the lower liquid holes 3613 is blocked by the seat 321, at this time, the drilling fluid is still being injected downward, the pressure inside the circulation cavity 3611 is increased, and then the piston column 362 is pushed to move downward, it should be noted that the elastic buckle 324 and the bearing ring 323 are kept at a certain distance to meet the needs of lifting the inner pipe assembly 3 to a certain distance until the lower liquid holes 3613 are leveled with the seat 321;

[0102] After the piston column 362 moves downward for a distance and abuts against the transmission column 344, the transmission column 344 is continuously pushed to move downward, in the process of moving downward, the isolation membrane 37 at the lower end of the transmission column 344 is broken by the cone head 38, the first channel 3441 is communicated with the second channel 381, and then the refrigerant storage tank 343 is communicated with the refrigeration cavity 354, the refrigerant in the refrigerant storage tank 343 enters into the refrigeration cavity 354 to mix with the cold source, after the refrigerant and the cold source are mixed, the refrigeration of the core tube 352 is started, and the volatilized gas is discharged from the gas one-way valve 349;

[0103] After the isolation membrane 37 is broken and the refrigerant storage tank 343 and the refrigeration cavity 354 are communicated, the inner pipe assembly 3 is lowered to reset, the upper liquid holes 3612 are communicated with the lower liquid holes 3613, and the drilling fluid is kept circulating until the freezing of the core tube 352 is completed;

[0104] The trip sleeve 4 is lowered from the outer pipe assembly 2, the trip sleeve 4 is sleeved on the mud circulation joint 361 under the action of gravity and the drilling fluid until abutting against the seat 321, at this time, the elastic buckle 324 is extruded by the trip sleeve 4, and then the elastic buckle 324 is kept separated from the bearing ring 323, the inner pipe assembly 3 and the trip sleeve 4 are taken out from the outer pipe assembly 2 by the fisher, and the sampled core sample is stored in the high-pressure low-temperature container.

[0105] Compared with the existing natural gas hydrate freezing coring drill and method, the proposed coring drill has the characteristics of simple structure, strong feasibility of implementation method and good reliability in the implementation process, and the combination of the mud circulating pressure and the piston column 362 and the transmission column 344 is used to realize the connection of the refrigerant storage tank 343 and the refrigeration cavity 354, and then the freezing of the core is realized. Meanwhile, the drill can well protect the core integrity during drilling and coring, and has high freezing efficiency.

[0106] The preferred embodiments of the present application have been described above by way of example only, not for limitation, and various changes and modifications can be made by those skilled in the art without departing from the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A natural gas hydrate coring drill comprising an outer pipe assembly (2) provided with a drill bit (1) at a lower end and an inner pipe assembly (3) provided inside the outer pipe assembly (2) for freezing and collecting natural gas hydrate, characterized in that, The inner tube assembly (3) comprises, from top to bottom, a spear head (31), a hovering mechanism (32), a single-action mechanism (33), a refrigeration mechanism (34), and a frozen core chamber (35); The refrigeration mechanism (34) comprises a perforated connecting seat (341), a refrigerant protection outer tube (342), a refrigerant storage tank (343), a transmission column (344), a support seat (345), and a through-hole handle (346). The upper and lower ends of the refrigerant protection outer tube (342) are connected with the perforated connecting seat (341) and the through-hole handle (346), respectively. The upper end of the perforated connecting seat (341) is connected with the single-action mechanism (33). The lower end of the through-hole handle (346) is connected with the frozen core chamber (35); The refrigerant storage tank (343) and the support seat (345) are arranged in the refrigerant protection outer tube (342). The upper end of the refrigerant storage tank (343) abuts against the perforated connecting seat (341). The lower end of the refrigerant storage tank (343) is connected with the upper end of the support seat (345). The lower end of the support seat (345) abuts against the through-hole handle (346); The perforated connecting seat (341), the refrigerant storage tank (343), the support seat (345), and the through-hole handle (346) are vertically provided with coaxially-communicating through holes. The transmission column (344) is slidably arranged in the through holes of the refrigerant storage tank (343) and the support seat (345). The transmission column (344) is provided with a first channel (3441) at the upper end. The upper end of the first channel (3441) is in communication with the inner cavity of the refrigerant storage tank (343). The lower end of the first channel (3441) is in communication with the lower end of the transmission column (344). The lower end face of the transmission column (344) is provided with a separation membrane (37); The through-hole handle (346) is provided with a tapered head (38) in the through hole. The tapered head (38) is located below the separation membrane (37). The tapered head (38) is provided with a second channel (381); The frozen core chamber (35) comprises a refrigerant storage tube (351), a core tube (352), and a clasp seat (353). The upper and lower ends of the refrigerant storage tube (351) are connected with the through-hole handle (346) and the clasp seat (353), respectively. The core tube (352) is coaxially arranged in the refrigerant storage tube (351). A refrigeration cavity (354) is formed between the refrigerant storage tube (351), the core tube (352), the through-hole handle (346), and the clasp seat (353). The refrigeration cavity (354) is in communication with the second channel (381); The refrigerant storage tank (343) stores a refrigerant. The refrigeration cavity (354) is provided with a cold source; The drive mechanism (36) is used for vertically moving the transmission column (344).

2. A natural gas hydrate coring drill according to claim 1, wherein, The single-acting mechanism (33) comprises a first hole-bearing seat (331); the driving mechanism (36) comprises a mud circulating joint (361) and a piston column (362), the mud circulating joint (361) is internally provided with a circulating cavity (3611), a plurality of upper liquid through holes (3612) and a plurality of lower liquid through holes (3613) are spaced apart on the mud circulating joint (361), and the upper liquid through holes (3612) and the lower liquid through holes (3613) are in communication with the circulating cavity (3611); The bottom of the mud circulating joint (361) is connected with the first hole-bearing seat (331), the first hole-bearing seat (331) is vertically provided with a piston cavity (3311), the piston cavity (3311) is in communication with the circulating cavity (3611), and the piston column (362) is slidably arranged out of the piston cavity (3311), and the lower end of the piston column (362) is coaxially and spaced apart from the transmission column (344); The hovering mechanism (32) comprises a pedestal (321) and a suspension ring (322), the outer pipe assembly (2) is internally provided with the pedestal (321), the outer wall of the mud circulating joint (361) is sleeved with the suspension ring (322), the suspension ring (322) is located between the upper liquid through holes (3612) and the lower liquid through holes (3613), the suspension ring (322) abuts against the pedestal (321), and the pedestal (321) is in sliding fit with the mud circulating joint (361).

3. A natural gas hydrate coring drill according to claim 2, wherein, The top of the mud circulating joint (361) is connected with the spear head (31); The hovering mechanism (32) further comprises a bearing ring (323) and an elastic buckle (324), the bearing ring (323) is arranged on the mud circulating joint (361), and the bearing ring (323) is located above the suspension ring (322); A plurality of elastic buckles (324) are arranged around the inner part of the outer pipe assembly (2), the elastic buckles (324) are matched with the top of the bearing ring (323), and the elastic buckles (324) are used for providing downward force to the mud circulating joint (361).

4. A natural gas hydrate coring drill according to claim 3, wherein, A release sleeve (4) is further arranged, the outer diameter of the spear head (31) is smaller than the outer diameter of the mud circulating joint (361); A limiting portion (41) is arranged at the top of the release sleeve (4), a sliding hole (411) is arranged on the limiting portion (41), and the sliding hole (411) is in clearance fit with the spear head (31); The inner cavity of the release sleeve (4) is in sliding fit with the bearing ring (323) and the suspension ring (322); The outer wall of the release sleeve (4) is in sliding fit with the outer pipe assembly (2) and the elastic buckle (324).

5. A hydrate coring tool according to any one of claims 2 to 4, wherein, The single-action mechanism (33) further includes a second perforated bearing seat (332), a first single-action bearing (333), a second single-action bearing (334), a buffer spring (335), a spring stop (336), a washer (337), and a stop nut (338). The first perforated bearing seat (331) is provided with a first step portion (3312) and a second step portion (3313) that are successively narrowed from top to bottom. The first single-action bearing (333) and the second single-action bearing (334) are respectively sleeved on the first step portion (3312) and the second step portion (3313). The inner cavity of the second perforated bearing housing (332) is provided with a first step portion (3321), a second step portion (3322), and a third step portion (3323) from top to bottom. The inner diameter of the third step portion (3323) is larger than the inner diameter of the second step portion (3322). The first step portion (3321) cooperates with the first single-acting bearing (333), and the second step portion (3322) cooperates with the second single-acting bearing (334). The buffer spring (335) is sleeved on the second step (3313) of the first perforated bearing seat (331). The lower end of the second step (3313) is sleeved with a spring stop (336) and a washer (337) from top to bottom, and is threadedly connected to the stop nut (338). The upper and lower ends of the buffer spring (335) abut against the third step (3323) and the spring stop (336) respectively; The lower end of the second perforated bearing seat (332) is connected to the perforated connecting seat (341).

6. A natural gas hydrate coring drill according to claim 5, wherein, It also includes a first sealing ring (363), a second sealing ring (347) and a third sealing ring (348), wherein the first sealing ring (363) is disposed between the piston rod (362) and the piston chamber (3311); The second sealing ring (347) is disposed between the transmission column (344) and the through hole at the upper end of the refrigerant storage tank (343); The third sealing ring (348) is disposed between the through hole on the transmission column (344) and the support seat (345).

7. A natural gas hydrate coring drill according to claim 6, wherein, It also includes a mud check valve (355), through which the upper end of the core tube (352) is unidirectionally connected to the cavity between the refrigerant storage tube (351) and the outer tube assembly (2).

8. A natural gas hydrate coring drill according to claim 7, wherein, It also includes a gas check valve (349), and a gas guide hole (3461) is provided radially on the through hole connector (346). The gas guide hole (3461) is connected to the through hole below the cone (38), and the gas check valve (349) is embedded in the gas guide hole (3461).

9. A natural gas hydrate coring drill according to claim 8, wherein, The inner wall of the refrigerant storage pipe (351) is provided with a heat insulation layer (356).

10. A method for coring frozen natural gas hydrates using a frozen natural gas hydrate coring tool as claimed in any one of claims 1 to 9, wherein, Includes the following steps: S1. Core drilling: During the drilling process of the natural gas hydrate layer, the drill bit (1) is carried by the outer tube assembly (2). Natural gas hydrate continuously enters the core tube (352). The useless mud and other substances inside the core tube (352) are discharged from the mud check valve (355). S2, after the core barrel (352) is filled with natural gas hydrate, drilling is stopped, but the circulation of the mud at the bottom of the hole is maintained, at this time, the drilling fluid enters the circulation cavity (3611) from the upper liquid passage (3612) when passing through the seat (321), and then enters the cavity between the inner tube assembly (3) and the outer tube assembly (2) below the seat (321) from the lower liquid passage (3613); S3, the inner tube assembly (3) is pulled up until the lower liquid passage (3613) is flush with the seat (321), that is, the outlet of the lower liquid passage (3613) is blocked by the seat (321), at this time, the drilling fluid is still being poured downward, the pressure in the circulation cavity (3611) increases, and then pushes the piston column (362) to move downward; S4, after the piston column (362) moves downward for a distance, it abuts against the transmission column (344), the transmission column (344) is continuously pushed to move downward, and the lower end of the transmission column (344) is broken by the cone head (38) during the downward movement of the transmission column (344), so that the first passage (3441) and the second passage (381) are communicated, and then the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigeration cavity (354), and the refrigerant storage tank (343) is communicated with the refrigerant ​ ​

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