CN115450598B - Sea area natural gas hydrate solid-state fluidization green mining system and method - Google Patents
Sea area natural gas hydrate solid-state fluidization green mining system and method Download PDFInfo
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- CN115450598B CN115450598B CN202111483785.9A CN202111483785A CN115450598B CN 115450598 B CN115450598 B CN 115450598B CN 202111483785 A CN202111483785 A CN 202111483785A CN 115450598 B CN115450598 B CN 115450598B
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- NMJORVOYSJLJGU-UHFFFAOYSA-N methane clathrate Chemical compound C.C.C.C.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O NMJORVOYSJLJGU-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 238000005243 fluidization Methods 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000005065 mining Methods 0.000 title claims description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 294
- 239000007787 solid Substances 0.000 claims abstract description 226
- 239000007788 liquid Substances 0.000 claims abstract description 166
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 147
- 239000002245 particle Substances 0.000 claims abstract description 147
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 91
- 239000007789 gas Substances 0.000 claims abstract description 68
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 62
- 238000010438 heat treatment Methods 0.000 claims abstract description 58
- 238000003860 storage Methods 0.000 claims abstract description 54
- 239000013049 sediment Substances 0.000 claims abstract description 29
- 239000013535 sea water Substances 0.000 claims abstract description 18
- 238000004519 manufacturing process Methods 0.000 claims description 55
- 238000000926 separation method Methods 0.000 claims description 46
- 238000007789 sealing Methods 0.000 claims description 30
- 238000002347 injection Methods 0.000 claims description 25
- 239000007924 injection Substances 0.000 claims description 25
- 238000004064 recycling Methods 0.000 claims description 23
- 238000004321 preservation Methods 0.000 claims description 17
- 238000011084 recovery Methods 0.000 claims description 16
- 239000000203 mixture Substances 0.000 claims description 9
- 238000010276 construction Methods 0.000 claims description 6
- 238000009413 insulation Methods 0.000 claims description 6
- 238000005520 cutting process Methods 0.000 claims description 4
- 238000005516 engineering process Methods 0.000 claims description 3
- 238000011144 upstream manufacturing Methods 0.000 claims description 3
- 238000013461 design Methods 0.000 claims description 2
- 239000003345 natural gas Substances 0.000 abstract description 10
- 238000000354 decomposition reaction Methods 0.000 abstract description 8
- 238000012544 monitoring process Methods 0.000 description 13
- 230000000694 effects Effects 0.000 description 12
- 230000009471 action Effects 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 230000008569 process Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 238000006386 neutralization reaction Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- -1 Natural gas hydrates Chemical class 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 238000005191 phase separation Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 238000003303 reheating Methods 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011549 displacement method Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 238000013467 fragmentation Methods 0.000 description 1
- 238000006062 fragmentation reaction Methods 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000005360 mashing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000009965 odorless effect Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/2605—Methods for stimulating production by forming crevices or fractures using gas or liquefied gas
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
- E21B41/0099—Equipment or details not covered by groups E21B15/00 - E21B40/00 specially adapted for drilling for or production of natural hydrate or clathrate gas reservoirs; Drilling through or monitoring of formations containing gas hydrates or clathrates
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/2607—Surface equipment specially adapted for fracturing operations
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
- E21B43/305—Specific pattern of wells, e.g. optimising the spacing of wells comprising at least one inclined or horizontal well
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/34—Arrangements for separating materials produced by the well
- E21B43/35—Arrangements for separating materials produced by the well specially adapted for separating solids
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/34—Arrangements for separating materials produced by the well
- E21B43/40—Separation associated with re-injection of separated materials
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Geology (AREA)
- Fluid Mechanics (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Drilling And Exploitation, And Mining Machines And Methods (AREA)
Abstract
The application relates to a sea natural gas hydrate solid fluidization green exploitation system and a method, wherein the exploitation system comprises a liquid nitrogen fracturing system and a gas acquisition system, the liquid nitrogen fracturing system utilizes high-pressure liquid nitrogen to carry out body fracture operation on a solid hydrate reservoir, and low-temperature liquid nitrogen ensures that the hydrate keeps solid form underground and cannot be decomposed into water and gaseous methane; the gas collection system can collect solid hydrate solid particles to the ground and store the solid hydrate solid particles in the storage tank, the storage tank filled with the hydrate solid particles is heated by the heating system, so that the solid small particles are decomposed into methane gas, water, sediment and the like, the methane gas is recovered, the decomposed water flows into seawater, and the sediment can be utilized to fill the goaf under the well after exploitation is completed. The application can effectively avoid geological disasters possibly caused by hydrate decomposition, realizes safe and green exploitation of natural gas, can recycle liquid nitrogen and saves resources.
Description
Technical Field
The application belongs to the technical field of natural gas hydrate exploitation, and particularly relates to a sea area natural gas hydrate solid-state fluidization green exploitation system and method.
Background
The national program realizes the carbon neutralization comprehensively in 2060, and improves the energy proportion with lower carbon emission in all the fossil energy sources used, thus being an effective way for realizing the carbon neutralization. Natural gas plays an increasingly important role in achieving "carbon neutralization" due to the small carbon emissions. Natural gas hydrate is one of the most potential unconventional successor energy sources following shale gas and coalbed gas. Natural gas hydrates are found in the east China sea, the south China sea, the Qinghai-Tibet plateau and the Heilongjiang. It is estimated that the natural gas hydrate resource amount in China will exceed 2000×10 8 t oil equivalent. Wherein the sea area of south sea is about 650×10 8 t, the Qinghai-Tibet and Heilongjiang frozen soil bands are 1400 multiplied by 10 8 t. It can be seen that the reserves of ocean hydrates are huge.
The prior method for exploiting natural gas hydrate mainly comprises a depressurization method, a heat injection method, a chemical agent injection method and co 2 Displacement methods, however, require breaking the solid form of the natural gas hydrate and decomposing downholeAnd natural gas, and has the potential risk of causing environmental geological disasters. Because the natural gas hydrate in the sea area of China has the characteristics of deep and shallow burying, no compact cover layer, non-diagenetic, weak cementation, easy fragmentation and the like, the underground decomposed natural gas easily escapes out through the cover layer with poor compactness to cause a greenhouse effect, and the content of methane gas easily exceeds the standard on the sea surface to generate aggregated explosion. Therefore, a learner puts forward a natural gas hydrate solid state fluidization exploitation thought, namely, carrying hydrate solid particles to the ground by using seawater and then decomposing, but the defect is that the hydrate solid particles are easy to decompose under the soaking of the seawater, and are also easy to decompose into natural gas in the pit, so that the aim of carrying all the hydrate solid particles to the ground cannot be realized.
Disclosure of Invention
In view of the above analysis, the present application aims to provide a system and a method for solid fluidization green exploitation of natural gas hydrate in sea area, which are used for solving the above technical problems.
The purpose of the application is realized in the following way:
in one aspect, there is provided a sea-area natural gas hydrate solid state fluidization green recovery system comprising:
the liquid nitrogen fracturing system comprises a liquid nitrogen conveying pipeline, a pressurizing pipeline, an injection well and a horizontal fracturing well which are sequentially arranged, wherein the liquid nitrogen conveying pipeline is connected with the pressurizing pipeline through a tee joint, and a liquid nitrogen booster pump is arranged on the pressurizing pipeline and used for boosting liquid nitrogen;
the gas collection system comprises a production well and a solid particle output pipeline, at least one part of the production well is positioned in the hydrate reservoir, and the solid particle output pipeline extends into the hydrate reservoir through the production well; the solid particle output pipeline is sequentially provided with a gas storage container, a gas pump, a gas-liquid-solid separation device, a first high-pressure pump, a heating system, a liquid-solid separation device and a second high-pressure pump from a gas collecting end to a gas collecting end.
Further, the second high-pressure pump is arranged at the gas production end of the solid particle output pipeline and is used for supplying liquid nitrogen and a hydrate solid particle mixture in the fractured hydrate reservoir into the solid particle output pipeline; the liquid-solid separation device is used for separating liquid nitrogen and a hydrate solid particle mixture and is provided with a liquid outlet and a solid particle outlet, the separated liquid nitrogen is discharged from the liquid outlet, and the solid particle outlet is connected with the heating system; the discharge port of the heating system is connected with the feed port of the gas-liquid-solid separation device, and the gas outlet of the gas-liquid-solid separation device is connected with the gas storage container through the gas pump.
Further, the device also comprises a liquid nitrogen recovery system, wherein the liquid nitrogen recovery system comprises a liquid nitrogen recycling conveying pipeline, a liquid inlet of the liquid nitrogen recycling conveying pipeline is connected with a liquid outlet of the liquid-solid separation device, and a liquid outlet of the liquid nitrogen recycling conveying pipeline is connected with a pressurizing pipeline through a tee joint; the liquid nitrogen recycling conveying pipeline is provided with a liquid pump and a liquid nitrogen recycling storage.
Further, the device also comprises a sediment conveying pipeline, one end of the sediment conveying pipeline is connected with a sediment outlet of the gas-liquid-solid separation device, and the other end of the sediment conveying pipeline extends to the finished goaf through the old well.
Further, the horizontal fracturing well adopts bridge plug type staged fracturing, the horizontal fracturing well is provided with a plurality of sections of fracturing pipe sections, a bridge plug is arranged between two adjacent fracturing pipe sections, and each fracturing section is provided with a high-pressure perforation.
Further, a first heat preservation sleeve layer is arranged in the injection well, and a first well head sealing device is arranged at the well head of the injection well;
a second heat preservation sleeve layer is arranged in the production well, and a second wellhead sealing device is arranged at the wellhead of the production well.
Further, the diameter of the well bore of the production well is larger than the diameter of the solid particle output pipeline, and a gap is formed between the solid particle output pipeline and the well wall of the production well.
Further, the production wellbore diameter is equal to 5-10 times the output tubing diameter.
Further, the production well comprises an upper section and a lower section which are arranged from top to bottom, wherein the upper section penetrates through the sea water layer and the upper hydrate coating, and the lower section penetrates through the hydrate reservoir; the bottom of the hole of the lower section is leveled with the top surface of the base layer or is positioned 10-20cm below the top surface of the base layer.
Further, the portion of the production well within the hydrate reservoir is provided with a solid particle screen.
Further, the gas collection system further comprises a mincing device, the mincing device is provided with a linear motor, a connecting rod and blades, the linear motor is arranged on a working platform on the sea surface, an output shaft of the linear motor is connected with a first end of the connecting rod, a plurality of blades are arranged at a second end of the connecting rod through a tool apron, cutting edges of the blades are arranged downwards, a plurality of blades form an annular space in a surrounding mode, and the second high-pressure pump is located in the annular space formed by the blades in a surrounding mode.
Further, the connecting rod is a hollow pipe, the connecting rod is sleeved on the solid particle output pipeline, the second wellhead sealing device is provided with a mounting opening, the connecting rod penetrates through the mounting opening of the second wellhead sealing device and is in sliding sealing contact with the mounting opening of the second wellhead sealing device, the connecting rod is driven to linearly reciprocate by the linear motor, the blade is driven to linearly reciprocate, and large-particle-size hydrate solid particles around the second high-pressure pump are crushed.
Further, the blades are arranged in a plurality of rows, each row forming a ring; radially outward from the center of the concentric rings, the spacing between adjacent concentric rings increases gradually.
Further, the heating system is arranged on the ground or an offshore working platform; the heating system comprises a high-pressure container and a heating device for heating the high-pressure container, wherein the high-pressure container is arranged on the solid particle output pipeline and is positioned at the upstream of the gas-liquid-solid separation device so as to be used for heating the fed hydrate solid particles.
Further, the heating device comprises a hot water storage and a boiler, a high-pressure container is arranged in the hot water storage, and a water bath space is formed between the high-pressure container and the inner wall of the hot water storage so as to be filled with high-temperature water; the boiler is communicated with the water bath space through a water inlet pipe and a water return pipe, and a water pump is arranged on the water inlet pipe.
Further, the hot water storage is provided with a container main body and a sealing cover, and the sealing cover has a heat insulation function; the outside heat preservation that is equipped with of hot water storage, heat preservation set up around the container main part of hot water storage, and the opening of heat preservation is higher than the opening of container main part, and the inner wall of heat preservation is embedded to the outer edge of sealed lid.
Further, a thermometer I is arranged in the hot water storage and is used for monitoring the temperature of the high-temperature water in the hot water storage; the high-pressure container is provided with a pressure monitoring pipeline and a thermometer II, the pressure monitoring pipeline is provided with a pressure gauge for monitoring the air pressure in the high-pressure container, and the thermometer II is used for monitoring the air temperature in the high-pressure container.
On the other hand, the application also provides a sea natural gas hydrate solid fluidization green exploitation method, which utilizes the sea natural gas hydrate solid fluidization green exploitation system, and comprises the following steps:
step one: constructing an injection well, a horizontal fracturing well and a production well according to the design, wherein the horizontal fracturing well is positioned in a hydrate reservoir, and the production well penetrates through a sea water layer, a hydrate upper covering layer and the hydrate reservoir;
step two: injecting liquid nitrogen at-196 ℃ into a horizontal fracturing well by utilizing a liquid nitrogen fracturing system, and fracturing a hydrate reservoir to fracture a solid hydrate body into hydrate solid particles; and extracting hydrate solid particles and the liquid nitrogen after fracturing by using a gas acquisition system, separating the liquid nitrogen after fracturing from the hydrate solid particles by using a liquid-solid separation device, and feeding the separated hydrate solid particles into a heating system for heating, wherein the generated gaseous methane is stored in a methane gas storage.
Further, in the second step, before the liquid nitrogen at-196 ℃ is injected into the horizontal fracturing well by utilizing the liquid nitrogen fracturing system, the pressure P of the injected liquid nitrogen is determined based on the maximum principal stress sigma and trend of the hydrate reservoir, and the pressure P of the injected liquid nitrogen is specifically determined according to the following formula: p is more than or equal to 2 sigma, wherein P is the pressure of injected liquid nitrogen and Mpa; sigma is the maximum principal stress of the hydrate reservoir, mpa.
In the second step, the bridge plug staged fracturing technology is adopted to carry out fracturing construction of the horizontal fracturing well, and high-pressure liquid nitrogen is utilized to carry out staged and clustered high-pressure jet fracturing activities in the horizontal fracturing well in sequence.
In the second step, the liquid nitrogen separated by the liquid-solid separation device is recovered to a liquid nitrogen recovery storage through a liquid pump; when the pressure of the pressure gauge reaches a preset pressure, a gate valve II on the liquid nitrogen recycling conveying pipeline is opened, and the recycled liquid nitrogen is pressurized by a tee joint and a liquid nitrogen booster pump and then conveyed into a corresponding fracturing section in the horizontal well again for fracturing activities.
In the second step, the separated hydrate solid particles are fed into a heating system for heating, and the generated gas methane is stored in a methane gas storage
In the second step, when the ground heating system is used for heating the high-pressure container filled with the hydrate solid particles, the gate valve III is opened, hot water at 80-100 ℃ in the boiler is conveyed to the hot water storage container through the water pump, the high-pressure container is heated, and then the hot water flows back to the boiler through the water return pipe for reheating, so that continuous heating of the high-pressure container is realized.
In the second step, after the hydrate solid particles are heated by a heating system, the generated methane gas, water and sediment are fed into a gas-liquid-solid separation device for gas-liquid-solid three-phase separation;
methane gas separated by the gas-liquid-solid separation device is conveyed to a gas storage under the action of a gas pump, separated water is directly discharged into seawater, and separated sediment is injected into a hydrate goaf after exploitation through a sediment conveying pipeline in an old well.
In the second step, in the process of pumping, fracturing and crushing hydrate solid particles and releasing the pressure of liquid nitrogen by the second high-pressure pump, starting a crushing device, and crushing the large-particle-size hydrate solid particles around the second high-pressure pump by using the crushing device.
Compared with the prior art, the sea natural gas hydrate solid fluidization green mining system and method provided by the application fully utilize the low-temperature effect of liquid nitrogen, and fracture a hydrate reservoir by using low-temperature liquid nitrogen, so that broken hydrate solid particles keep a low-temperature solid state and are not decomposed in the pit; when liquid nitrogen carries hydrate solid particles to be conveyed to the ground, liquid nitrogen and the hydrate solid particles are separated, the liquid nitrogen is recycled for recycling, so that resources are saved, meanwhile, the separated hydrate solid particles are subjected to heating treatment, the decomposition speed of the hydrate solid particles is increased, and the purpose of high yield is realized.
Drawings
In order to more clearly illustrate the embodiments of the present description or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the embodiments of the present description, and other drawings may be obtained according to these drawings for a person having ordinary skill in the art.
FIG. 1 is a schematic diagram of a solid state fluidization green mining system for natural gas hydrates in the sea area;
FIG. 2 is a schematic diagram of a heating system according to the present application;
fig. 3 is a schematic partial structure of the mashing device provided by the application.
Reference numerals:
1-a working platform; 2-liquid nitrogen storage; 3-gate valve I; 4-a one-way valve; 5-liquid nitrogen delivery pipeline; 6-tee joint; 7-a liquid nitrogen booster pump; 8-a first wellhead sealing device; 9-a first insulation sleeve layer; 10-an injection well; 11-liquid nitrogen recycling conveying pipelines; 12-a second insulation sleeve layer; 13-a second wellhead sealing device; 14-a solid particle output conduit; 15-a production well; 16-a liquid-solid separation device; 17-a heating system; 171-an insulating layer; 172-sealing cover; 173-a water bath space; 174-a first pressure relief valve; 175-a pressure gauge; 176-feed line; 177-thermometer one; 178-an output conduit; 179-thermometer two; 1710-second pressure relief valve; 1711-inlet tube; 1712-a hot water reservoir; 1713-a water pump; 1714-gate valve three; 1715-a return pipe; 1716-boiler; 1717-high pressure vessel; 18-a first high-pressure pump; 19-a liquid pump; 20-a gas-liquid-solid separation device; 21-a pressure gauge; 22-liquid nitrogen recovery storage; 23-gas pump; a 24-methane gas storage; 25-drainage pipe; 26-sea water layer; 27-a silt conveying pipeline; a 28-hydrate upper coating; 29-hydrate goaf; 30-a second high-pressure pump; 31-base stratum; 32-fracturing a breaker belt; 33-a first frac section; 34-a second frac section; 35-third frac section; 36-fourth frac section; 37-bridge plug; 38-perforating direction; 39-horizontal fracturing well; 40-hydrate reservoir; 41-a solid particle screen; 42-connecting rod; 43-blade.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
For the purpose of facilitating an understanding of the embodiments of the present application, reference will now be made to the following description of specific embodiments, taken in conjunction with the accompanying drawings, which are not intended to limit the embodiments of the application.
In describing embodiments of the present application, it should be noted that, unless explicitly stated and limited otherwise, the term "coupled" should be interpreted broadly, for example, as being fixedly coupled, as being detachably coupled, as being integrally coupled, as being mechanically coupled, as being electrically coupled, as being directly coupled, as being indirectly coupled via an intermediate medium. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
The terms "top," "bottom," "above … …," "below," and "on … …" are used throughout the description to refer to the relative positions of components of the device, such as the relative positions of the top and bottom substrates inside the device. It will be appreciated that the devices are versatile, irrespective of their orientation in space.
Example 1
In a specific embodiment of the application, as shown in fig. 1, a sea area natural gas hydrate solid fluidization green mining system is disclosed, which is used for mining the natural gas hydrate in the sea, a bedrock layer 31, a hydrate storage layer 40, a hydrate upper covering layer 28 and a sea water layer 26 are developed from bottom to top on the longitudinal section of the sea in a mining area, and a working platform 1 is built on the sea surface for installing various equipment and serving as a construction site.
A sea area natural gas hydrate solid state fluidization green mining system comprising:
the liquid nitrogen fracturing system comprises a liquid nitrogen conveying pipeline 5, a pressurizing pipeline, an injection well 10 and a horizontal fracturing well 39 which are sequentially arranged, wherein a liquid nitrogen storage 2, a gate valve I3 and a one-way valve 4 are sequentially arranged on the liquid nitrogen conveying pipeline 5; the liquid nitrogen conveying pipeline 5 is connected with a pressurizing pipeline through a tee joint 6, and a liquid nitrogen pressurizing pump 7 is arranged on the pressurizing pipeline and is used for pressurizing liquid nitrogen, and the pressurized liquid nitrogen is supplied into a horizontal fracturing well 39 through an injection well 10 for fracturing; the liquid nitrogen outlet pipe of the liquid nitrogen booster pump 7 enters the horizontal fracturing well 39 through the injection well 10, the horizontal fracturing well 39 adopts bridge plug type staged fracturing, the horizontal fracturing well 39 is provided with a plurality of segments of fracturing pipe sections, a bridge plug 37 is arranged between two adjacent fracturing pipe sections, and each fracturing section is provided with a high-pressure perforation.
The gas collection system comprises a gas collection pipeline, the gas collection pipeline comprises a production well 15 and a solid particle output pipeline 14, at least one part of the production well 15 is positioned in the hydrate reservoir 40, and the solid particle output pipeline 14 extends into the hydrate reservoir 40 through the production well 15; the solid particle output pipeline 14 is provided with a gas storage container 24, a gas pump 23, a gas-liquid-solid separation device 20, a first high-pressure pump 18, a heating system 17, a liquid-solid separation device 16 and a second high-pressure pump 30 in sequence from the gas collecting end to the gas collecting end, wherein the second high-pressure pump 30 extends into a hydrate reservoir 40 through a production well 15 so as to prepare for pumping out a mixture of liquid nitrogen and hydrate solid particles. The liquid-solid separation device 16 is used for solid-liquid separation, separates liquid nitrogen and hydrate solid particle mixture pumped from the underground, the liquid-solid separation device 16 is provided with a liquid outlet and a solid particle outlet, the separated liquid nitrogen is discharged from the liquid outlet, and the solid particle outlet is connected with the heating system 17; the discharge port of the heating system 17 is connected with the feed port of the gas-liquid-solid separation device 20, and the gas outlet of the gas-liquid-solid separation device 20 is connected with the gas storage container 24 through the gas pump 23.
In this embodiment, the hydrate solid particles generated after fracturing include solid natural gas hydrate particles, silt and water due to the low temperature of the liquid nitrogen.
Further, the sea natural gas hydrate solid fluidization green mining system also comprises a liquid nitrogen recovery system so as to realize the recovery and utilization of liquid nitrogen. The liquid nitrogen recovery system comprises a liquid nitrogen recycling conveying pipeline 11, a liquid inlet of the liquid nitrogen recycling conveying pipeline 11 is connected with a liquid outlet of a liquid-solid separation device 16, and a liquid outlet of the liquid nitrogen recycling conveying pipeline 11 is connected with a pressurizing pipeline through a tee joint 6; the liquid nitrogen recycling conveying pipeline 11 is provided with a liquid pump 19 and a liquid nitrogen recycling storage 22.
Further, the sea natural gas hydrate solid fluidization green mining system further comprises a sediment conveying pipeline 27, one end of the sediment conveying pipeline 27 is connected with a sediment outlet of the gas-liquid-solid separation device 20, and the other end of the sediment conveying pipeline extends to the finished goaf 29 through the old well. Old wells refer to the injection well 10, the production well 15 where fracturing production has been completed previously. After completion of fracturing by one horizontal fracturing well 39 and gas production by production well 15, hydrate goaf 29 is formed in the underground mining area, and the old well is communicated with the mined-out goaf 29. The sediment produced and separated by the current production well 15 is injected into the hydrate goaf which is already mined through the sediment conveying pipeline 27 in the old well, and the goaf is filled with the sediment, so that the large deformation of the submarine structure can be avoided, and geological disasters are caused.
In the implementation, in a determined submarine hydrate development area, the drilling equipment is utilized to construct and construct the injection well 10, the aquatic well 39 and the production well 15 on the hydrate upper cover layer 28 and the hydrate reservoir 40, the liquid nitrogen fracturing system is utilized to fracture the horizontal fracturing well 39 positioned in the hydrate reservoir 40 to form the fracturing fracture zone 32, and solid hydrate bodies in the fracturing zone are broken into small-particle-size hydrate solid particles under the high-pressure jet fracturing action of a large amount of high-pressure liquid nitrogen. Because of the lower temperature condition of the seabed, the decompressed liquid nitrogen can be gasified into nitrogen with higher pressure in a very small part due to the change of the temperature, the secondary fracturing effect is carried out on the broken hydrate solid, but most of the liquid nitrogen can still be kept in a liquid state, and the temperature of the liquid nitrogen at the temperature of 196 ℃ below zero ensures that the hydrate can keep a solid form and cannot be decomposed into water and gaseous methane. Under the negative pressure action of the second high-pressure pump 30, hydrate solid particles in the fracturing breaking belt 32 pass through a solid particle screen 41 along with the depressurized liquid nitrogen, enter the liquid-solid separation device 16 through a solid particle output pipeline 14 in the production well 15, the liquid nitrogen separated by the liquid-solid separation device 16 is supplied into a liquid nitrogen recovery storage 22 through the liquid pump 19 to recover the liquid nitrogen, and the liquid nitrogen in the liquid nitrogen recovery storage 22 is supplied into a pressurizing pipeline through a one-way valve to be pressurized and sent into a horizontal well to perform fracturing again, so that the cyclic use of the liquid nitrogen is realized; the hydrate solid particles separated by the liquid-solid separation device 16 enter the heating system 17 for heating treatment, the decomposition speed of the hydrate solid particles is obviously improved, the hydrate solid particles are heated to form a gas-water-sediment particle three-part mixture, the gas-liquid-solid separation device 20 is used for separating the gas, the water and the sediment particles into three phases, the decomposed gas is methane gas, the methane gas enters and is stored in the gas storage 24 for recovery, the decomposed water is discharged into the sea water through the drain pipe 25, and the sediment particles are injected into the mined hydrate goaf 29 through the sediment conveying pipeline 27 for filling.
In order to maintain the liquid nitrogen temperature, a first thermal jacket layer 9 is provided over the upper portion of the injection well 10, the length of the first thermal jacket layer 9 being at least greater than the sum of the thicknesses of the hydrate upper cover layer 28 and the sea water layer 26, and a first wellhead seal 8 is provided at the wellhead of the injection well 10.
In this embodiment, the production well 15 penetrates the sea water layer 26, the hydrate upper cover layer 28 and the hydrate reservoir 40, the second wellhead sealing device 13 is disposed at the wellhead of the production well 15, the diameter of the well hole of the production well 15 is larger than that of the solid particle output pipeline 14, a gap is formed between the solid particle output pipeline 14 and the well wall of the production well 15, and air is in the gap, so that heat transfer is reduced. Alternatively, the wellbore diameter of the production well 15 is 5-10 times the diameter of the output tubing 14. Wherein the production well 15 comprises an upper section and a lower section which are arranged from top to bottom, the upper section penetrates through the sea water layer 26 and the hydrate upper covering layer 28, the lower section penetrates through the hydrate reservoir 40, and the bottom of the hole of the lower section is leveled with the top surface of the bedrock layer 31 or is positioned 10 cm to 20cm below the top surface of the bedrock layer 31. The second insulation layer 12 is arranged at the upper section of the production well 15 to prevent the hydrate solid particles from sublimating when heated.
After the pressure of the reservoir 40 is released, the hydrate solid particles can instantaneously enter the lower section of the production well 15, and rapidly accumulate in a short time, so that the inlet of the second high-pressure pump 30 is blocked, and the pressure release of the hydrate reservoir is not facilitated. Therefore, in an alternative implementation manner of this embodiment, the diameter of the well bore of the production well 15 is larger than that of the fracturing well, the diameter of the well bore of the upper section of the production well 15 is larger than that of the well bore of the lower section, and the upper section is reamed, so that the space of the upper section of the well bore is large, and the upper section can be used as a buffer space for storing solid hydrate particles, which is beneficial to rapid decompression of the hydrate reservoir 40, thereby improving the production efficiency.
Optionally, the lower section of the production well 15 is provided with a solid particle screen 41, the solid particle screen 41 is of a hollow cylindrical structure, and the length of the solid particle screen 41 is greater than or equal to the length of the lower section. Due to the fracturing pressure relief of the reservoir 40, the particulate hydrate solid particles will rapidly pass through the solid particle screen 41 into the lower section and be pumped to the surface by the second high pressure pump 30. The mesh size of the solid particle screen 41 is 5cm, so that hydrate solid particles with the particle size smaller than 5cm can be screened out, and hydrate solid particles which can enter the inlet of the second high-pressure pump 30 can be screened out by using the solid particle screen 41, so that the smooth extraction of the hydrate solid particles in the well can be ensured.
In order to prevent the excessive particle size of the hydrate solid particles from blocking the inlet of the second high-pressure pump 30, the gas collecting system of the embodiment further comprises a mincing device, the mincing device is provided with a linear motor, a connecting rod 42 and blades 43, the linear motor is arranged on the working platform 1 on the sea surface, an output shaft of the linear motor is connected with a first end of the connecting rod 42, a plurality of blades 43 are arranged at a second end of the connecting rod 42 through a cutter holder, the cutting edges of the blades 43 are arranged downwards, the plurality of blades 43 form an annular space, and the second high-pressure pump 30 is positioned in the annular space formed by the blades 43, as shown in fig. 3; the connecting rod 42 is a hollow pipe, the connecting rod 42 is sleeved on the solid particle output pipeline 14, the second wellhead sealing device 13 is provided with a mounting opening, the connecting rod 42 penetrates through the mounting opening of the second wellhead sealing device 13 and is in sliding sealing contact with the mounting opening of the second wellhead sealing device 13, the connecting rod 42 is driven to reciprocate linearly by utilizing the linear motor to drive the blade 43 to reciprocate linearly, large-particle-diameter hydrate solid particles around the second high-pressure pump 30 are crushed, the inlet blockage of the second high-pressure pump 30 caused by overlarge particle diameters of the hydrate solid particles is prevented, and smooth extraction of the hydrate solid particles is ensured.
Further, the blades 43 enclose a plurality of concentric rings, that is, the blades 43 are arranged in a plurality of rows, each row constituting a ring; the center of each concentric ring is radially outwards, the distance between every two adjacent concentric rings is gradually increased, the structure is arranged to enable hydrate solid particles close to the second high-pressure pump 30 to be crushed into smaller particle sizes, the hydrate solid particles with small particle sizes close to the second high-pressure pump 30 are pumped out, the hydrate solid particles with large particle sizes far away are close to the second high-pressure pump 30, at the moment, the stirring device continuously breaks, the close hydrate solid particles with large particle sizes are cut into smaller particles by blades of the inner ring, sequential breaking is achieved, the cutting effect is guaranteed, and the hydrate solid particles are smoothly pumped out.
In this embodiment, as shown in fig. 2, the heating system 17 is disposed on the ground or on the offshore platform 1, and the heating system 17 disposed on the ground can achieve the purpose of high yield, so that a great amount of heat energy is saved compared with downhole pyrolysis of natural gas hydrate. The heating system includes a high pressure vessel 1717 and a heating device for heating the high pressure vessel 1717, the high pressure vessel 1717 being provided on the solid particle output pipe 14 and upstream of the gas-liquid-solid separation device 20 in preparation for heating the hydrate solid particles fed in. As shown in fig. 2, the high-pressure container 1717 is provided with a feeding pipe 176 and an output pipe 178, the feeding pipe 176 and the output pipe 178 are connected to the solid particle output pipe 14, hydrate solid particles separated from the liquid-solid separation device 16 enter the high-pressure container 1717 through the feeding pipe 176, and are heated by the heating device to form a gas-liquid-solid three-phase mixture, and the gas-liquid-solid three-phase mixture flows out of the output pipe 178 into the gas-liquid-solid separation device 20 under the action of the first high-pressure pump 18 to perform three-phase separation of methane gas, water and silt particles.
In this embodiment, the heating device heats the high-pressure container 1717 in a water bath, and the water bath heating method has the advantages of convenience in taking seawater, strong temperature controllability and low cost. Specifically, the heating device includes a hot water storage 1712 and a boiler 1716, a high pressure container 1717 is disposed in the hot water storage 1712, a water bath space 173 is formed between the high pressure container 1717 and an inner wall of the hot water storage 1712 for filling high temperature water, the boiler 1716 is communicated with the water bath space 173 through a water inlet pipe 1711 and a water return pipe 1715, a water pump 1713 is disposed on the water inlet pipe 1711, the high temperature water heated in the boiler 1716 enters the water bath space 173 of the hot water storage 1712 through the water inlet pipe 1711 under the action of the water pump 1713 from a boiler outlet, and is recovered into the boiler 1716 through the water return pipe 1715 for reheating, so as to realize continuous heating.
The hot water storage 1712 is provided with a container main body and a sealing cover 172, and the sealing cover 172 has a heat insulation function; the outside of the hot water storage 1712 is provided with a heat preservation layer 171, the heat preservation layer 171 is arranged around the container main body of the hot water storage 1712, the inner wall surface of the heat preservation layer 171 is contacted with the outer wall surface of the container main body, the opening of the heat preservation layer 171 is higher than the opening of the container main body, and the outer edge of the sealing cover 172 is embedded into the inner wall of the heat preservation layer 171, so that the heat preservation function is improved.
Further, a first thermometer 177 is disposed in the hot water storage 1712 and is used for monitoring the temperature of the hot water in the hot water storage 1712, and the hot water storage 1712 is further provided with a second pressure release valve 1710, wherein a pressure release end of the second pressure release valve 1710 passes through the sealing cover 172 to be communicated with the atmosphere. The high pressure container 1717 is provided with a pressure monitoring pipeline and a second thermometer 179, the pressure monitoring pipeline is provided with a pressure gauge 175 for monitoring the air pressure in the high pressure container 1717, and the second thermometer 179 is used for monitoring the air temperature in the high pressure container 1717. The pressure monitoring pipeline passes through the sealing cover 172, and is further provided with a first pressure relief valve 174 communicated with the atmosphere, when the first high-pressure pump 18 fails or the gas collecting end of the gas collecting pipeline is blocked, the air pressure in the high-pressure container 1717 is rapidly increased, and the pressure is relieved by the first pressure relief valve 174 at the moment, so that the air pressure in the high-pressure container 1717 is prevented from being too high, and the high-pressure container 1717 is damaged.
The embodiment also discloses a sea area natural gas hydrate solid fluidization green exploitation method, which utilizes the sea area natural gas hydrate solid fluidization green exploitation system, and the exploitation method comprises the following steps:
step one: injection well 10, horizontal fracturing well 39 and production well 15 are constructed as designed, with horizontal fracturing well 39 being located within hydrate reservoir 40 and production well 15 extending through sea water layer 26, hydrate overburden 28 and hydrate reservoir 40.
Specifically, in the selected natural gas hydrate reservoir development area, well point positions of the injection well 10, the horizontal well 39 and the production well 15 are respectively determined, the injection well 10, the horizontal well 39 and the production well 15 are constructed by using drilling equipment, a first heat preservation jacket layer 9 and a second heat preservation jacket layer 12 are respectively arranged on the upper parts of the injection well 10 and the production well 15, and a first well mouth sealing device 8 and a second well mouth sealing device 13 are respectively arranged on the well mouths of the injection well 10 and the production well 15.
Step two: injecting liquid nitrogen at-196 ℃ into the horizontal fracturing well 39 by utilizing a liquid nitrogen fracturing system to fracture the hydrate reservoir 40 so as to fracture the solid hydrate bodies into hydrate solid particles; the hydrate solid particles and the liquid nitrogen after fracturing are extracted by a gas acquisition system, the liquid nitrogen after fracturing and the hydrate solid particles are separated by a liquid-solid separation device 16, the separated hydrate solid particles are fed into a heating system 17 for heating, and the generated gas methane is stored in a methane gas storage 24.
Before the liquid nitrogen fracturing system is used for injecting the liquid nitrogen at the temperature of minus 196 ℃ into the horizontal fracturing well 39, the pressure P of the injected liquid nitrogen is determined based on the maximum principal stress sigma and trend of the hydrate reservoir, and the pressure P of the injected liquid nitrogen is specifically determined according to the following formula:
P≥2σ，
wherein P is the pressure of injected liquid nitrogen, and Mpa; sigma is the maximum principal stress of the hydrate reservoir, mpa.
During the fracturing construction, the bridge plug staged fracturing technology is adopted to carry out the fracturing construction of the horizontal fracturing well, and a large amount of high-pressure liquid nitrogen is utilized to carry out the high-pressure jet fracturing activities in the horizontal fracturing well in a staged and clustered manner in sequence. Specifically, the first gate valve 3 is opened, the second gate valve on the liquid nitrogen recycling conveying pipeline 11 is closed, and high-pressure liquid nitrogen with the pressure P is injected into the horizontal well 39 through the injection well 10 by utilizing the liquid nitrogen fracturing system. Bridge plugs are arranged among the fracturing pipe sections of the horizontal well, each fracturing section is provided with a high-pressure perforation, the first fracturing section 33, the second fracturing section 34, the third fracturing section 35, the fourth fracturing pipe section 36 … and the like are sequentially subjected to perforation shower, the first cluster, the second cluster, the third cluster and the like are sequentially subjected to fracturing construction, a fracturing fracture zone 32 is formed in the hydrate reservoir 40, and the perforation direction 38 is shown in fig. 1. The high-pressure liquid nitrogen is used for fracturing the hydrate solid through the jet nozzle, so that the hydrate solid in the corresponding area of each fracturing section is subjected to large-scale bulk fracturing, a solid hydrate reservoir is large-scale and is greatly broken into hydrate solid particles with small particle sizes, and the hydrate solid particles comprise solid natural gas hydrate particles, silt and water. As the temperature of the liquid nitrogen is-196 ℃, the hydrate is effectively ensured to keep solid form, and the hydrate cannot be decomposed into water and gaseous methane in the liquid nitrogen soaking process. Because the temperature of the seabed is usually kept at-10 to +10 ℃, the temperature of the hydrate reservoir is higher than the temperature of liquid nitrogen, a small part of the liquid nitrogen is gasified into nitrogen with higher pressure due to the change of the temperature after pressure relief, and the gasified high-pressure nitrogen further carries out secondary fracturing on hydrate solids, but most of the liquid nitrogen can still be kept in a liquid state.
After the hydrate solid state in the corresponding area of the first fracturing section 33 is broken into small-particle-size hydrate solid particles, the second fracturing section of the horizontal well is sequentially subjected to fracturing activity, meanwhile, the second high-pressure pump 30 is opened to pump the hydrate solid particles generated by fracturing and the depressurized liquid nitrogen, the hydrate solid particles and the depressurized liquid nitrogen are conveyed to the ground liquid-solid separation device 16 through the solid particle conveying pipeline 14, the liquid nitrogen and the hydrate solid particles are separated in the liquid-solid separation device 16, the separated liquid nitrogen is recycled to the liquid nitrogen recycling storage 22 through the liquid pump 19, when the pressure of the pressure gauge 21 reaches the preset pressure, the gate valve II on the liquid nitrogen recycling conveying pipeline 11 is opened, the recycled liquid nitrogen is conveyed to the corresponding fracturing section in the horizontal well 39 again for fracturing activity after being pressurized through the tee joint 6 and the liquid nitrogen booster pump 7, so that the recycling of the liquid nitrogen is realized, and a large amount of resources are saved. The separated hydrate solid particles are conveyed to a heating system 17 on the ground, and are subjected to heating treatment in a high-pressure container resistant to high pressure, so that the hydrate solid is promoted to be rapidly decomposed, the decomposition speed of the solid particles is greatly improved, the recovery efficiency is further improved, and a large amount of heat energy is saved compared with underground heating. The solid hydrate particles are quickly decomposed into methane gas, water, sediment and the like after being heated, the methane gas is collected into a storage container, the decomposed water flows into seawater, and the separated sediment fills the well area after the exploitation is completed through an old well.
When the ground heating system 17 is utilized to heat the high-pressure container 1717 filled with hydrate solid particles, firstly, the gate valve III 1714 is opened, the water in the boiler 1716 is controlled to be maintained at 80-100 ℃, hot water at 80-100 ℃ in the boiler 1716 is conveyed to the hot water storage container 1712 through the water pump 1713, after the hot water in the water bath space heats the high-pressure container 1717, the hot water flows back to the boiler 1716 through the water return pipe 1715 to be heated again, and thus the continuous heating of the high-pressure container 1717 is realized, and the recycling of the water is realized. In the heating process of the circulating hot water, the heat preservation layer 171 and the sealing cover 17172 can perform a certain heat preservation function on the hot water, meanwhile, the thermometer I177 is used for monitoring the water temperature in the hot water storage container 1712, the manometer is used for monitoring the pressure in the hot water storage container 1712, and when the pressure in the hot water storage container 1712 exceeds 0.2MPa, the second pressure relief valve 1710 automatically relieves the pressure. After the high-pressure container 1717 filled with the hydrate solid particles is heated, the decomposition speed of the hydrate solid particles is greatly improved relative to normal-temperature decomposition, so that the recovery efficiency can be further improved. During the heating process, the pressure gauge 175 detects the pressure in the high-pressure container, and when the pressure exceeds the maximum allowable pressure of the high-pressure container, the first pressure relief valve 174 automatically relieves the pressure so as to ensure safety.
The heated and decomposed water, gas and sediment are further conveyed to the gas-liquid-solid separation device 20 for separation through the action of the first high-pressure pump 18, the separated methane gas is collected under the action of the gas pump 23 and conveyed to the gas storage 24, the water is directly discharged into seawater, the sediment is injected into the mined hydrate goaf 29 through the sediment conveying pipeline 27 in the old well, the hydrate goaf 29 is filled, and the submarine structure can be prevented from being greatly deformed to cause geological disasters.
When the second high-pressure pump 30 pumps the hydrate solid particles generated by fracturing and crushing and the liquid nitrogen subjected to pressure relief, a crushing device is started, and the large-particle-size hydrate solid particles around the second high-pressure pump 30 are crushed in real time by the crushing device. Specifically, the connecting rod 42 is driven by linear motor in a linear reciprocating manner, the blade 43 is driven to do linear reciprocating motion, and large-particle-size hydrate solid particles around the second high-pressure pump 30 are crushed, so that the blockage of the inlet of the second high-pressure pump 30 caused by the overlarge particle size of the hydrate solid particles is prevented, and the smooth extraction of the hydrate solid particles is ensured.
Compared with the prior art, the sea natural gas hydrate solid fluidization green mining system and method provided by the application have at least one of the following beneficial effects:
1. the fracturing effect and the low-temperature effect of the high-pressure liquid nitrogen are fully utilized, and the hydrate solid is broken into small-size hydrate solid particles in a large area and in a large extent through the jet flow effect of a large amount of high-pressure liquid nitrogen. Because the temperature of the submarine hydrate reservoir is usually-10 to +10 ℃, and the change of the temperature is considered, the tiny part of liquid nitrogen can be gasified to generate nitrogen with higher pressure, and the nitrogen with higher pressure can enter hydrate solid microcracks more easily to perform secondary fracturing, so that the fractured hydrate solid particles are further broken. As the temperature of the liquid nitrogen is-196 ℃, the broken hydrate solid particles are soaked in the liquid nitrogen after pressure relief and cannot be further decomposed, and are conveyed to the ground together with the liquid nitrogen under the action of a high-pressure pump, the problems that the hydrate is easy to decompose underground to cause natural gas leakage, fire and other geological disasters when the hydrate solid particles are conveyed through seawater at present are solved, and the safe and green exploitation of the natural gas is realized.
2. After the hydrate solid particles and the liquid nitrogen which are conveyed to the ground are separated by the liquid-solid separation device, the separated liquid nitrogen can be further recycled, and a large amount of resources are saved.
3. The ground heating system can heat the hydrate solid particles by using hot water on the ground, so that the decomposition speed of the hydrate solid particles is greatly improved, and the recovery efficiency of natural gas is greatly improved; compared with the traditional method for heating and accelerating the decomposition of the hydrate reservoir under the ground, the method avoids the loss of a large amount of heat energy in the heat energy conveying process, and greatly saves the heat energy.
4. The sediment separated after the solid hydrate particles are decomposed is injected into the submarine hydrate finished goaf through the old well, so that natural disasters such as earthquake, tsunami and the like caused by deformation of a submarine structure can be further avoided.
5. The liquid nitrogen is colorless, odorless, corrosion-free, pollution-free and extremely low in temperature, is inert gas with extremely good stability, can be directly prepared through nitrogen preparation equipment on a production site, and avoids the danger and high cost in the process of liquid nitrogen transportation.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the application, and is not meant to limit the scope of the application, but to limit the application to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the application are intended to be included within the scope of the application.
Claims (9)
1. A sea area natural gas hydrate solid state fluidization green mining system, comprising:
the liquid nitrogen fracturing system comprises a liquid nitrogen conveying pipeline (5), a pressurizing pipeline, an injection well (10) and a horizontal fracturing well (39) which are sequentially arranged, wherein the liquid nitrogen conveying pipeline (5) is connected with the pressurizing pipeline through a tee joint (6), and a liquid nitrogen pressurizing pump (7) is arranged on the pressurizing pipeline and is used for pressurizing liquid nitrogen, and the pressurized liquid nitrogen is supplied into the horizontal fracturing well (39) through the injection well (10) for fracturing;
a gas collection system comprising a production well (15) and a solid particle output conduit (14), at least a portion of the production well (15) being located within the hydrate reservoir (40), the solid particle output conduit (14) extending through the production well (15) into the hydrate reservoir (40); a gas storage container (24), a gas pump (23), a gas-liquid-solid separation device (20), a first high-pressure pump (18), a heating system (17), a liquid-solid separation device (16) and a second high-pressure pump (30) are sequentially arranged on the solid particle output pipeline (14) from the gas collecting end to the gas collecting end;
the second high-pressure pump (30) is arranged at the gas production end of the solid particle output pipeline (14) and is used for supplying liquid nitrogen and a hydrate solid particle mixture in the hydrate reservoir after fracturing into the solid particle output pipeline (14);
the liquid-solid separation device (16) is used for separating liquid nitrogen and a hydrate solid particle mixture, the liquid-solid separation device (16) is provided with a liquid outlet and a solid particle outlet, the separated liquid nitrogen is discharged from the liquid outlet, and the solid particle outlet is connected with the heating system (17);
the discharge port of the heating system 17 is connected with the feed port of the gas-liquid-solid separation device (20), and the gas outlet of the gas-liquid-solid separation device (20) is connected with the gas storage container (24) through the gas pump (23);
the gas collection system further comprises a mincing device, the mincing device is provided with a linear motor, a connecting rod (42) and blades (43), the linear motor is arranged on the working platform (1) on the sea surface, an output shaft of the linear motor is connected with a first end of the connecting rod (42), a plurality of blades (43) are arranged at a second end of the connecting rod (42) through a cutter holder, the cutting edges of the blades (43) are arranged downwards, an annular space is defined by the plurality of blades (43), and the second high-pressure pump (30) is located in the annular space defined by the blades (43); the connecting rod (42) is a hollow pipe, the connecting rod (42) is sleeved on the solid particle output pipeline 14, a second wellhead sealing device (13) is arranged at the wellhead of the production well (15), the second wellhead sealing device (13) is provided with a mounting hole, the connecting rod (42) penetrates through the mounting hole of the second wellhead sealing device (13) and is in sliding sealing contact with the mounting hole of the second wellhead sealing device (13), the connecting rod (42) is driven by a linear motor to linearly reciprocate, a blade (43) is driven to linearly reciprocate, and large-particle-diameter hydrate solid particles around the second high-pressure pump (30) are crushed.
2. The sea natural gas hydrate solid fluidization green mining system according to claim 1, further comprising a liquid nitrogen recovery system, wherein the liquid nitrogen recovery system comprises a liquid nitrogen recycling conveying pipeline (11), a liquid inlet of the liquid nitrogen recycling conveying pipeline (11) is connected with a liquid outlet of a liquid-solid separation device (16), and a liquid outlet of the liquid nitrogen recycling conveying pipeline (11) is connected with a pressurizing pipeline through a tee joint (6);
the liquid nitrogen recycling conveying pipeline (11) is provided with a liquid pump (19) and a liquid nitrogen recycling storage (22).
3. The ocean natural gas hydrate solid state fluidization green mining system as claimed in claim 1, further comprising a sediment transport pipe (27), wherein one end of the sediment transport pipe (27) is connected to a sediment outlet of the gas-liquid-solid separation device (20), and the other end extends to the completed goaf (29) through the old well.
4. The sea area natural gas hydrate solid fluidization green mining system according to claim 1, wherein a first insulation sleeve layer (9) is arranged in the injection well (10), and a first wellhead sealing device (8) is arranged at the wellhead of the injection well (10);
a second heat preservation sleeve layer (12) is arranged in the production well (15).
5. The sea area gas hydrate solid fluidized green production system of claim 1, wherein the portion of the production well (15) located within the hydrate reservoir is provided with a solid particle screen (41).
6. Sea area natural gas hydrate solid state fluidization green mining system according to claim 1, characterized in that the heating system (17) is arranged on the ground or on the working platform (1) at sea;
the heating system comprises a high-pressure container (1717) and a heating device for heating the high-pressure container (1717), wherein the high-pressure container (1717) is arranged on the solid particle output pipeline (14) and is positioned at the upstream of the gas-liquid-solid separation device (20) so as to heat the fed hydrate solid particles.
7. The sea natural gas hydrate solid state fluidization green mining system according to claim 1, wherein the heating device comprises a hot water storage (1712) and a boiler (1716), a high pressure container (1717) is arranged in the hot water storage (1712), and a water bath space (173) is formed between the high pressure container (1717) and the inner wall of the hot water storage (1712) so as to be filled with high temperature water; the boiler (1716) is communicated with the water bath space (173) through a water inlet pipe (1711) and a water return pipe (1715), and a water pump (1713) is arranged on the water inlet pipe (1711).
8. A method for producing sea natural gas hydrate by solid fluidization and green mining, characterized in that the sea natural gas hydrate solid fluidization and green mining system as claimed in any one of claims 1 to 7 is used, comprising the steps of:
step one: constructing an injection well (10), a horizontal fracturing well (39) and a production well (15) according to the design, wherein the horizontal fracturing well (39) is positioned in a hydrate reservoir (40), and the production well (15) penetrates through a sea water layer (26), a hydrate upper covering layer (28) and the hydrate reservoir (40);
step two: injecting liquid nitrogen at-196 ℃ into a horizontal fracturing well (39) by utilizing a liquid nitrogen fracturing system, and fracturing a hydrate reservoir (40) to break solid hydrate bodies into hydrate solid particles; the hydrate solid particles and the liquid nitrogen after fracturing are extracted by utilizing a gas acquisition system, the liquid nitrogen after fracturing and the hydrate solid particles are separated by a liquid-solid separation device (16), the separated hydrate solid particles are fed into a heating system (17) for heating, and the generated gaseous methane is stored in a methane gas storage (24).
9. The sea area natural gas hydrate solid state fluidization green mining method according to claim 8, wherein in the second step, the bridge plug staged fracturing technology is adopted to carry out fracturing construction of a horizontal fracturing well, and high-pressure liquid nitrogen is utilized to carry out staged and clustered high-pressure jet fracturing in the horizontal fracturing well in sequence.
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