A rapid sampling system and method for marine natural gas hydrates

Abstract

The present invention discloses a rapid sampling system for marine natural gas hydrates, which includes a double-wall drill pipe and a separator, a drilling fluid solids control tank, a first circulation pump, a heat exchange device, a drilling fluid storage tank, and a second circulation pump that are sequentially connected through pipelines. The water outlet of the second circulation pump is connected to the top of the annulus of the double-wall drill pipe, and the top discharge port of the middle channel of the double-wall probe is connected to the feed port of the separator. The bottom of the annulus is connected to the bottom of the middle channel through a through hole, and the through hole is inclined, and the end of the through hole close to the annulus is lower than the end of the through hole close to the middle channel. A drill bit is installed at the bottom end of the double-wall drill pipe; the separator is used to separate marine natural gas hydrates and drilling fluid, the drilling fluid solids control tank is used to remove solid particles in the drilling fluid, and the heat exchange device is used to cool the drilling fluid. The rapid sampling system and method for marine natural gas hydrates of the present invention improve the efficiency of sampling marine natural gas hydrates and the core quality.

Description

Technical Field

[0001] The present invention relates to the technical field of marine oil and gas reservoir resource exploration, and particularly relates to a rapid sampling system and method for marine natural gas hydrates. Background Art

[0002] Natural gas hydrates are ice-like crystalline substances formed by natural gas and water under high pressure and low temperature conditions, and mainly exist under marine sediments at a water depth exceeding 300 m and a deep water temperature of about 2°C. To achieve the commercial exploitation of natural gas hydrates, it is first necessary to search for the areas where natural gas hydrates exist. The detection of natural gas hydrates is based on the method of submarine seismic exploration to draw a submarine geological structure map and determine the reflection layer of natural gas hydrates, so as to find the areas where natural gas hydrates exist. This method is currently relatively mature and effective, but in order to obtain more accurate hydrate formation information, it is necessary to further analyze and test through drilling and sampling.

[0003] Currently, the research on natural gas hydrate sampling methods mainly focuses on pressure-core sampling, but there are problems such as complex core drill tool structures, numerous procedures, and slow sampling speeds; there is also a sampling method as shown in the patent with publication number CN107631899B, which can achieve continuous coring, but mainly realizes drilling through the method of high-pressure and low-temperature water jets, and the core is relatively severely broken, disturbing the original core structure. Summary of the Invention

[0004] The purpose of the present invention is to provide a rapid sampling system and method for marine natural gas hydrates to solve the problems existing in the above-mentioned prior art and improve the sampling efficiency and core quality of marine natural gas hydrates.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] The present invention provides a rapid sampling system for marine natural gas hydrates, including a double-wall drill pipe and a separator, a drilling fluid solid control tank, a first circulation pump, a heat exchange device, a drilling fluid storage tank, and a second circulation pump that are sequentially connected through pipelines. The outlet of the second circulation pump is connected to the top of the annulus of the double-wall drill pipe, the top discharge port of the middle channel of the double-wall drill rod is connected to the inlet of the separator, the bottom of the annulus is connected to the bottom of the middle channel through a through hole, the through hole is inclined, and the end of the through hole close to the annulus is lower than the end of the through hole close to the middle channel. A drill bit is installed at the bottom end of the double-wall drill pipe; the separator is used to separate marine natural gas hydrates and drilling fluid, the drilling fluid solid control tank is used to remove solid particles in the drilling fluid, and the heat exchange device is used to cool the drilling fluid.

[0007] Preferably, the through hole is at least one.

[0008] Preferably, the gas separated by the separator accumulates in the upper part of the separator, and the gas outlet in the upper part of the separator is communicated with the gas inlet of the logging device.

[0009] Preferably, it further includes a coolant circulation pump and a refrigeration unit, and the heat exchange device adopts a heat exchanger; the feed port of the coolant circulation pump is communicated with the refrigerant outlet of the heat exchanger, the discharge port of the coolant circulation pump is communicated with the feed port of the refrigeration unit, and the discharge port of the refrigeration unit is communicated with the refrigerant inlet of the heat exchanger; the liquid outlet of the first circulation pump is communicated with the heat medium inlet of the heat exchanger, and the heat medium outlet of the heat exchanger is communicated with the liquid inlet of the drilling fluid storage tank.

[0010] Preferably, the overall marine natural gas hydrate rapid sampling system is arranged on a drilling ship.

[0011] Preferably, a power head for driving the double-wall drill pipe to rotate is arranged on the drilling ship.

[0012] Preferably, the connecting pipe between the separator and the double-wall drill pipe and the connecting pipe between the second circulation pump and the double-wall drill pipe are respectively rotationally and sealingly connected to the double-wall drill pipe.

[0013] The present invention also provides a method for rapidly sampling marine natural gas hydrates based on the above-mentioned marine natural gas hydrate rapid sampling system: cooling the drilling fluid to a set temperature through a heat exchange device, flowing the cooled drilling fluid to the drilling fluid storage tank, while driving the double-wall drill pipe to rotate, pumping the drilling fluid in the drilling fluid storage tank into the annulus of the double-wall drill pipe through the second circulation pump, after the drilling fluid enters the bottom of the annulus, it is sprayed obliquely upward into the middle channel of the double-wall drill rod through a through hole, thereby driving the core to return upward through the middle channel and enter the separator. In the separator, the marine natural gas hydrate rock sample is retained on the filter plate of the separator, and the separated drilling fluid flows back to the drilling fluid solids control tank. After the solid particles are removed by the drilling fluid solids control tank, the drilling fluid is cooled to the set temperature by the heat exchange device again, and this cycle continues.

[0014] The present invention has achieved the following technical effects compared with the prior art:

[0015] The rapid sampling system and method for marine natural gas hydrates of the present invention improve the sampling efficiency and core quality of marine natural gas hydrates. The present invention ensures a low-temperature environment throughout the wellbore by means of a closed cycle of cryogenic cooling drilling fluid, preventing the decomposition of natural gas hydrate rock samples at too high temperatures. The present invention realizes continuous sampling of hydrate formations by means of a hydraulic reverse circulation drilling method, injecting drilling fluid into the annulus between the inner and outer drill pipes of a dual-wall drill pipe and rapidly returning the drilling fluid and natural gas hydrate rock samples through the central channel of the dual-wall drill pipe. The entire sampling process has a simple process, a fast upward return speed, good core quality, and very little decomposition of the hydrate rock samples in the low-temperature mud, providing a rapid technical method for hydrate exploration sampling. The rapid sampling method for marine natural gas hydrates of the present invention realizes two closed cycles of drilling fluid and coolant, has zero pollution to the marine environment, and realizes green exploration of hydrate formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic structural diagram of the rapid sampling system for marine natural gas hydrates of the present invention;

[0018] Figure 2 is Figure 1 a partial enlarged view of part A in

[0019] Figure 3 It is a schematic diagram of a partial structure of the rapid sampling system for marine natural gas hydrates of the present invention;

[0020] Wherein: 100, rapid sampling system for marine natural gas hydrates; 1, coolant circulation pump; 2, first circulation pump; 3, separator; 4, second circulation pump; 5, power head; 6, dual-wall drill pipe; 601, annulus; 602, intermediate channel; 603, through hole; 61, inner drill pipe; 62, outer drill pipe; 621, second water inlet hole; 7, drilling ship; 8, original hydrate sample; 9, drill bit; 10, drilling fluid storage tank; 11, drilling fluid solids control tank; 12, heat exchanger; 13, refrigeration unit; 14, copper sleeve; 141, first water inlet hole; 15, rubber sealing ring; 16, first annular cavity; 17, second annular cavity; 18, sealing ring support frame; 19, outer pipe body; 20, upper flange; 21, O-ring; 22, first bearing; 23, second bearing; 24, liquid inlet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0022] The object of the present invention is to provide a rapid sampling system and method for marine natural gas hydrates to solve the problems existing in the above-mentioned prior art and improve the sampling efficiency and core quality of marine natural gas hydrates.

[0023] The present invention provides a rapid sampling system for marine natural gas hydrates, including a double-wall drill pipe and a separator, a drilling fluid solids control tank, a first circulation pump, a heat exchange device, a drilling fluid storage tank, and a second circulation pump that are sequentially connected through pipelines. The outlet of the second circulation pump is connected to the top of the annulus of the double-wall drill pipe. The top discharge port of the middle channel of the double-wall drill rod is connected to the feed port of the separator. The bottom of the annulus is connected to the bottom of the middle channel through a through hole. The through hole is inclined, and the end of the through hole close to the annulus is lower than the end of the through hole close to the middle channel. A drill bit is installed at the bottom end of the double-wall drill pipe. The separator is used to separate marine natural gas hydrates and drilling fluid. The drilling fluid solids control tank is used to remove solid particles in the drilling fluid. The heat exchange device is used to cool the drilling fluid.

[0024] The present invention also provides a rapid sampling method for marine natural gas hydrates based on the above rapid sampling system for marine natural gas hydrates: cooling the drilling fluid to a set temperature through the heat exchange device. After being cooled to the set temperature, the drilling fluid flows into the drilling fluid storage tank. While driving the double-wall drill pipe to rotate, the drilling fluid in the drilling fluid storage tank is pumped into the annulus of the double-wall drill pipe through the second circulation pump. After the drilling fluid enters the bottom of the annulus, it is sprayed obliquely upward into the middle channel of the double-wall drill rod through the through hole, thereby driving the core to return upward through the middle channel and enter the separator. In the separator, the marine natural gas hydrate rock sample is retained on the filter plate of the separator. The separated drilling fluid flows back to the drilling fluid solids control tank. After the solid particles are removed by the drilling fluid solids control tank, the drilling fluid is cooled to the set temperature by the heat exchange device again, and so on in a continuous cycle.

[0025] The rapid sampling system and method for marine natural gas hydrates of the present invention improve the sampling efficiency and core quality of marine natural gas hydrates.

[0026] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] AsFigures 1 to 3 As shown in the figure: In this embodiment, a rapid sampling system 100 for marine natural gas hydrates is provided, which includes a double-wall drill pipe 6 and a separator 3, a drilling fluid solids control tank 11, a first circulation pump 2, a heat exchange device, a drilling fluid storage tank 10, and a second circulation pump 4 that are connected in sequence through pipelines. The outlet of the second circulation pump 4 is connected to the top of the annulus 601 of the double-wall drill pipe 6, and the top discharge port of the middle channel 602 of the double-wall drill rod is connected to the inlet of the separator 3. The connecting pipes between the separator 3 and the double-wall drill pipe 6 and between the second circulation pump 4 and the double-wall drill pipe 6 are respectively rotationally and sealingly connected to the double-wall drill pipe 6.

[0028] The double-wall drill pipe 6 includes an inner drill pipe 61 and an outer drill pipe 62. The outer drill pipe 62 can rotate relative to the inner drill pipe 61 (this is a characteristic of the double-wall drill pipe 6 and will not be elaborated here). An outer pipe body 19 is sleeved on the outer drill pipe 62. The top end of the outer pipe body 19 is connected with an upper flange 20, and the bottom end is connected with a lower flange. A seal ring support frame 18 is arranged at the top end of the double-wall drill pipe 6. The seal ring support frame 18 is fixedly connected to the outer drill pipe 62. An O-ring 21 is arranged between the seal ring support frame 18 and the inner drill pipe 61. The seal between the seal ring support frame 18 and the inner drill pipe 61 is a dynamic seal. A rubber seal ring 15 is arranged between the seal ring support frame 18 and the upper flange 20. Two upper and lower rubber seal rings 15 are arranged between the outer drill pipe 62 and the outer pipe body 19. A copper sleeve 14 is arranged between the two rubber seal rings between the outer drill pipe 62 and the outer pipe body 19. The outer drill pipe 62 is rotationally matched with the upper flange 20 through a first bearing 22, and the outer drill pipe 62 is rotationally matched with the lower flange through a second bearing 23. A liquid inlet 24 is arranged on the side wall of the outer pipe body 19. A first annular cavity 16 is formed between the outer drill pipe 62 and the copper sleeve 14. A plurality of second water inlet holes 621 respectively communicating with the first annular cavity 16 are circumferentially arranged on the side wall of the outer drill pipe 62. A second annular cavity 17 is formed between the liquid inlet 24 and the copper sleeve 14. A plurality of first water inlet holes 141 are circumferentially arranged on the side wall of the copper sleeve 14. The liquid inlet 24 communicates with the second annular cavity 17, and the second annular cavity 17 communicates with the first annular cavity 16 through the first water inlet holes 141. The liquid outlet of the second circulation pump 4 is connected to the liquid inlet 24 through a pipeline. The inner drill pipe 61 is connected to the feed pipeline of the separator 3 through the upper flange 20. The outer drill pipe 62 can be driven to rotate by a power head 5, and the inner drill pipe 61 does not move when the outer drill pipe 62 rotates.

[0029] The bottom of the annulus 601 is connected to the bottom of the middle channel 602 through a plurality of through holes 603 evenly arranged circumferentially. The through holes 603 are inclined, and the end of the through hole 603 close to the annulus 601 is lower than the end of the through hole 603 close to the middle channel 602. By setting the through holes 603 in this way, the refrigerant in the annulus 601 can be sprayed obliquely upward into the middle channel 602, and the obliquely upward sprayed refrigerant can drive the core to return upward from the central channel.

[0030] The bottom end of the double-wall drill pipe 6 is installed with a drill bit 9; the separator 3 is used to separate marine natural gas hydrate and drilling fluid. The gas separated by the separator 3 accumulates in the upper part of the separator 3, and the gas outlet in the upper part of the separator 3 is communicated with the gas inlet of the logging device. The drilling fluid solids control tank 11 is used to remove solid particles in the drilling fluid. The drill bit 9, the separator 3, the logging device and the drilling fluid solids control tank 11 are all existing mature devices or products, and their specific combination and working principle will not be elaborated here.

[0031] The heat exchange device is used to cool the drilling fluid. In this embodiment, the heat exchange device adopts a heat exchanger 12; the marine natural gas hydrate rapid sampling system 100 of this embodiment further includes a carrier fluid circulation pump 1 and a refrigeration unit 13. The feed port of the carrier fluid circulation pump 1 is communicated with the refrigerant outlet of the heat exchanger 12, the discharge port of the carrier fluid circulation pump 1 is communicated with the feed port of the refrigeration unit 13, and the discharge port of the refrigeration unit 13 is communicated with the refrigerant inlet of the heat exchanger 12; the liquid outlet of the first circulation pump 2 is communicated with the heat medium inlet of the heat exchanger 12, and the heat medium outlet of the heat exchanger 12 is communicated with the liquid inlet of the drilling fluid storage tank 10.

[0032] It should be noted that the marine natural gas hydrate rapid sampling system 100 is integrally arranged on the drilling ship 7, and a power head 5 for driving the double-wall drill pipe 6 to rotate is arranged on the drilling ship 7.

[0033] This embodiment also provides a marine natural gas hydrate rapid sampling method based on the above-mentioned marine natural gas hydrate rapid sampling system 100, which is as follows:

[0034] The drilling fluid in the drilling fluid solids control tank 11 is pumped into the heat exchange device through the first circulation pump 2, and the drilling fluid is cooled to the set temperature by the heat exchange device. The drilling fluid after being cooled to the set temperature flows into the drilling fluid storage tank 10. While driving the double-wall drill pipe 6 to rotate, the drilling fluid in the drilling fluid storage tank 10 is pumped into the annulus 601 of the double-wall drill pipe 6 through the second circulation pump 4. After the drilling fluid enters the bottom of the annulus 601, it is sprayed obliquely upward into the middle channel 602 of the double-wall drill rod through the through hole 603, thereby driving the core, that is, the original hydrate sample 8, to return upward through the middle channel 602 and enter the separator 3. In the separator 3, the marine natural gas hydrate rock sample is retained on the filter plate of the separator 3, and the separated drilling fluid flows back to the drilling fluid solids control tank 11. After the solid particles are removed by the drilling fluid solids control tank 11, the drilling fluid is cooled to the set temperature by the heat exchange device again, and so on; the gas separated by the separator 3 accumulates in the upper part of the separator 3, and the gas outlet in the upper part of the separator 3 is communicated with the gas inlet of the logging device, and path operations are carried out through the path device.

[0035] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "center", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0036] Specific examples are used in this specification to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A rapid sampling system for marine natural gas hydrates, characterized in that: It includes a double-wall drill pipe and a separator, a drilling fluid solid control tank, a first circulation pump, a heat exchange device, a drilling fluid storage tank, and a second circulation pump that are connected in sequence through pipelines. The water outlet of the second circulation pump is connected to the top of the annulus of the double-wall drill pipe. The top discharge port of the middle channel of the double-wall drill pipe is connected to the feed port of the separator. The bottom of the annulus is connected to the bottom of the middle channel through a through hole. The through hole is inclined, and the end of the through hole close to the annulus is lower than the end of the through hole close to the middle channel. A drill bit is installed at the bottom end of the double-wall drill pipe. The separator is used to separate marine natural gas hydrates and drilling fluid. The drilling fluid solid control tank is used to remove solid particles in the drilling fluid. The heat exchange device is used to cool the drilling fluid. The double-wall drill pipe includes an inner drill pipe and an outer drill pipe. An outer pipe body is sleeved on the outer drill pipe. Two rubber sealing rings are arranged between the outer drill pipe and the outer pipe body. A copper sleeve is arranged between the two rubber sealing rings between the outer drill pipe and the outer pipe body. A liquid inlet is arranged on the side wall of the outer pipe body. A first annular cavity is formed between the outer drill pipe and the copper sleeve. A plurality of second water inlet holes respectively communicating with the first annular cavity are circumferentially arranged on the side wall of the outer drill pipe. A second annular cavity is formed between the liquid inlet and the copper sleeve. A plurality of first water inlet holes are circumferentially arranged on the side wall of the copper sleeve. The liquid inlet communicates with the second annular cavity. The second annular cavity communicates with the first annular cavity through the first water inlet holes. The liquid outlet of the second circulation pump is connected to the liquid inlet through a pipeline.

2. The rapid sampling system for marine natural gas hydrates according to claim 1, wherein: The through hole is at least one.

3. The rapid sampling system for marine natural gas hydrates according to claim 1, wherein: The gas separated by the separator accumulates in the upper part of the separator. The gas outlet of the upper part of the separator is connected to the gas inlet of the logging device.

4. The rapid sampling system for marine natural gas hydrates according to claim 1, wherein: It further includes a secondary refrigerant circulation pump and a refrigeration unit. The heat exchange device uses a heat exchanger. The feed port of the secondary refrigerant circulation pump is connected to the refrigerant outlet of the heat exchanger. The discharge port of the secondary refrigerant circulation pump is connected to the feed port of the refrigeration unit. The discharge port of the refrigeration unit is connected to the refrigerant inlet of the heat exchanger. The liquid outlet of the first circulation pump is connected to the hot medium inlet of the heat exchanger. The hot medium outlet of the heat exchanger is connected to the liquid inlet of the drilling fluid storage tank.

5. The rapid sampling system for marine natural gas hydrates according to claim 1, wherein: The marine natural gas hydrate rapid sampling system is integrally arranged on a drilling ship.

6. The rapid sampling system for marine natural gas hydrates according to claim 5, characterized in that: A power head for driving the double-wall drill pipe to rotate is arranged on the drilling ship.

7. The rapid sampling system for marine natural gas hydrates according to claim 1, wherein: The connecting pipes between the separator and the double-wall drill pipe and between the second circulation pump and the double-wall drill pipe are respectively rotationally and hermetically connected to the double-wall drill pipe.

8. A method for rapid sampling of marine natural gas hydrates based on the marine natural gas hydrate rapid sampling system according to any one of claims 1-7, characterized in that: The drilling fluid is cooled to a set temperature by a heat exchange device. After being cooled to the set temperature, the drilling fluid flows into a drilling fluid storage tank. While driving the double-wall drill pipe to rotate, the drilling fluid in the drilling fluid storage tank is pumped into the annulus of the double-wall drill pipe by a second circulation pump. After the drilling fluid enters the bottom of the annulus, it is sprayed obliquely upward into the middle channel of the double-wall drill pipe through a through hole, thereby driving the core to return upward through the middle channel and enter a separator. In the separator, the marine natural gas hydrate rock sample is retained on the filter plate of the separator, and the separated drilling fluid flows back to the drilling fluid solids control tank. After the solid particles are removed by the drilling fluid solids control tank, the drilling fluid is cooled to the set temperature by the heat exchange device again, and the cycle continues like this.

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