CN210396709U - Natural gas hydrate underwater production system based on fluidization exploitation - Google Patents
Natural gas hydrate underwater production system based on fluidization exploitation Download PDFInfo
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Abstract
The utility model discloses a natural gas hydrate underwater production system based on fluidization exploitation, including central collection system, the broken and decomposition system of slurry, underwater separation system, divide defeated system and umbilical cable system under water. Compared with the prior art, the utility model has the positive effects that: the utility model discloses according to sea area natural gas hydrate becomes to hide and exploit characteristics, combine the actual problem that the slurry lifted, provided one set of production system that collects, decomposes, divides to defeated under water based on natural gas hydrate fluidization exploitation. The system reduces the slurry lifting risk from the underground to the offshore processing facility under the large height difference, improves the natural gas collecting efficiency, adapts to centralized collection and processing after underwater multipoint dispersion production, and in addition, utilizes the circulating suspension to suspend and lift the residual silt after underwater decomposition so as to further process at the sea, thereby realizing the closed collection of all media.
Description
Technical Field
The utility model relates to a natural gas hydrate underwater production system based on fluidization exploitation.
Background
Natural gas hydrates (hereinafter referred to as hydrates) are ice-like crystalline compounds with cage-like structures formed by contacting water molecules and gas small molecules (mainly hydrocarbon gases) under the conditions of low temperature and high pressure, are widely accepted at present, and are mainly distributed in deep-water ocean storage. Natural gas hydrates can be regarded as highly compressed natural gas resources, 1m3The natural gas hydrate can be decomposed to release 160-180 m3(Standard State) natural gas, the total volume of natural gas in the global natural gas hydrate deposit, roughly estimated from this, is approximately 1.8X 1016～2.1×1016m3Equivalent to 2 times of the total carbon amount of the conventional fossil fuel which is proved in the world, so the energy position of the hydrate is expected to be in the futureThe energy-saving clean energy can replace the conventional fossil fuels such as petroleum, coal and the like and become a novel clean energy. At present, sea natural gas hydrate is still in exploration and trial production stages, and a large amount of basic research is carried out at the same time. In recent years, a plurality of sea area natural gas hydrate trial production activities are successively carried out.
According to the formation conditions of the natural gas hydrate in the sea area, the scholars propose a natural gas hydrate pilot production method based on fluidized exploitation. According to the method, after shallow natural gas hydrate is mechanically crushed, high-pressure fluid is injected to form natural gas hydrate slurry, and the natural gas hydrate slurry is discharged to an offshore facility through a pipeline (a flow channel in a pilot production stage is a shaft) to be processed, so that natural gas is obtained. The method has the typical characteristic of green mining, can realize the in-situ mining of the non-diagenetic natural gas hydrate, but has the characteristics of large sediment lifting and large liquid-solid ratio lifting, and has larger lifting energy consumption. Therefore, some researchers further propose to separate the silt of the natural gas hydrate slurry under water, and convey the separated slurry to the sea surface, and backfill the silt. However, although the above technology solves some technical problems of fluidized exploitation of natural gas hydrate to a certain extent, and advances the technology, there are still some parts that can be further innovated and optimized: (1) the natural gas hydrate suitable for the fluidized mining method is mainly located in a sea area of more than 1000m, so that the lifting efficiency advantage is not obvious for slurry lifting, and in the lifting process, the problem of gasification in a pipeline caused by changes of environmental temperature, self pressure and the like of natural gas needs to be solved; (2) although a method for separating mud and sand underwater is proposed to improve the lifting efficiency, the flow guarantee problem described in (1) still exists, and particularly for large-scale development in the later period, the conveying efficiency of the vertical pipe to natural gas is improved; (3) the silt carried by the exploitation of the natural gas hydrate can be further optimized for silt collection and treatment on the premise of sensitive marine environment.
Disclosure of Invention
In order to overcome prior art's shortcoming, the utility model provides a natural gas hydrate underwater production system based on fluidization exploitation aims at carrying out deep water natural gas hydrate development and production safely, high-efficiently.
The utility model discloses based on fluidization exploitation theory, combine to concentrate the production mode under water, concentrate broken, gasification, three-phase separation back with the natural gas hydrate slurry of multiple spot collection, with each looks result close transport to the offshore processing facility to the silt particle suspending agent with the help of the offshore facility provides mixes the extraction silt particle, solves its transport problem, in order to further improve production efficiency, reduces the risk of flowing, realizes the green of the extraction silt particle and handles.
The utility model adopts the technical proposal that: the utility model provides a natural gas hydrate underwater production system based on fluidization exploitation, includes central collection system, broken and decomposition system of slurry, separation system, branch transmission system and umbilical cable system under water, wherein:
the underwater central acquisition system is used for regulating pressure and collecting the received natural gas hydrate slurry and then transmitting the slurry to the slurry crushing and decomposing system;
the slurry crushing and decomposing system is used for carrying out primary crushing, depressurization gasification decomposition, secondary crushing and heating gasification decomposition on the received natural gas hydrate slurry in the conveying process to obtain a natural gas, free water and silt three-phase dispersing system;
the underwater separation system is used for buffering and separating natural gas, free water and silt conveyed from the upstream and conveying separated natural gas, free water and silt slurry to the downstream;
the separate transportation system is used for respectively transporting the separated natural gas, free water and silt slurry to an offshore treatment facility;
the umbilical cable system is used for providing hydrate inhibitors, mud suspending agents, process demand media, power supply, control and communication support for underwater production;
the underwater central acquisition system, the underwater separation system, the sub-transmission system and the umbilical cable system are respectively connected with the logic control system.
By the system, natural gas hydrate slurry collected at the front end can be collected, the natural gas hydrate slurry is crushed by a continuous crushing system, and gas separation is realized by means of pressure reduction, heating and other measures; the multiphase medium is subjected to phase separation in an underwater separation system, natural gas is output from a gas phase pipeline, most of free water turns over a weir plate, enters a free water storage tank and is conveyed to an offshore processing facility through an external conveying pump; a small part of free water and the silt are discharged through an outlet at the bottom of the separator, mixed with the suspending agent conveyed at sea, enter a silt liquid storage tank and further conveyed to an offshore treatment facility through an external conveying pump. Meanwhile, through the umbilical cable system, the supply of power, communication, control, suspension and the like to the underwater production system can be realized. By the system, the technical problem of conveying natural gas hydrate slurry by the large-head stand pipe can be solved, and the aims of fluidized exploitation of natural gas hydrate, underwater sub-conveying, efficient stand pipe conveying, green product treatment and the like are fulfilled.
Compared with the prior art, the utility model has the positive effects that:
the utility model discloses according to sea area natural gas hydrate becomes to hide and exploit characteristics, combine the actual problem that the slurry lifted, provide one set collect under water, decompose, divide defeated production system. The system reduces slurry liquid-solid ratio and slurry lifting risk under large height difference from a downhole to an offshore processing facility on one hand, improves natural gas acquisition efficiency, and adapts to centralized acquisition and processing after underwater multipoint dispersion production on the other hand. The method has the following specific advantages:
(1) science of setup
The utility model discloses based on the setting of fluidization exploitation principle, the mode that utilizes the fluidization to exploit at the front end obtains the natural gas hydrate slurry. Because the central production system is arranged underwater, underwater multi-point production can be realized. A decomposition system is arranged underwater, so that the natural gas is gasified and extracted from the natural gas hydrate, and the slurry decomposition efficiency is improved. The gas phase is conveyed to the offshore processing device by utilizing the self energy of the natural gas. The horizontal weir plate separator is arranged under water, so that the separation of the free water and the cement-containing sand is realized, the production rate of the free water and the cement-containing sand can be dynamically adjusted according to the fluctuation of the yield, and the water content of the cement-containing sand is controlled. And (3) injecting a suspending agent into the separated cement-containing sand by using the umbilical cable system to form a mud-sand slurry with better fluidity, and realizing green recovery and efficient transportation of the mud-sand slurry. Finally, a set of sea area natural gas hydrate production system based on fluidized exploitation, multi-phase underwater decomposition, high-efficiency outward transportation and green recovery is formed.
(2) Good economical efficiency
The utility model discloses a natural gas hydrate is collected to the mode of concentrating the collection under water to the multiphase is defeated separately, has reduced the high drop of natural gas hydrate thick liquids and has lifted the energy consumption, has also improved the efficiency of lifting under the unit water injection volume. Meanwhile, multi-phase separate transportation after decomposition is carried out underwater, so that efficient and safe transportation of each phase can be realized, and potential risks in the conventional natural gas hydrate slurry high-fall lifting are avoided.
(3) Green environment protection
The utility model discloses a reinjection suspending agent to obtain after decomposing the natural gas hydrate slurry carry out safe lifting and retrieve, this environmental protection risk of backfilling under water and probably arousing to the silt particle after having avoided the natural gas hydrate to decompose.
(4) Advanced in concept
At present, although the sea natural gas hydrate is still in the pilot production stage, a great deal of research and development work is carried out on the problems of the mining principle, the later-stage production risk and the like. The utility model discloses based on natural gas hydrate exploitation characteristics, the point of collection, heterogeneous branch are defeated, medicament filling etc. is concentrated under water that provides, can better match the actual problem of sea area natural gas hydrate later stage multi-well production, shifts the operation in the pit of complicacy to the operating condition better under water, and the system of being convenient for extends and the facility is maintained.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
fig. 1 is the schematic diagram of the utility model discloses a natural gas hydrate underwater production system based on fluidization exploitation.
Detailed Description
A gas hydrate underwater production system based on fluidized exploitation mainly comprises: the device comprises a collection pipeline 101, a reserved collection pipeline 102, a pressure transmitter 1, a ball valve 2, a regulating valve 3, a reserved ball valve 4, a reserved regulating valve 5, an underwater manifold 6, a converging pipeline 7, a normally open pipeline 201, a standby pipeline 202, a ball valve 8, a primary crushing system 9, a pressure transmitter 10, a pressure reducing valve 11, a pressure transmitter 12, an expanding reducer 13, a secondary crushing system 14, a ball valve 15, a ball valve 16, a primary crushing system 17, a pressure transmitter 18, a pressure reducing valve 19, a pressure transmitter 20, an expanding reducer 21, a secondary crushing system 22, a ball valve 23, a separator inlet pipeline 24, a horizontal weir plate separator 25, a pressure transmitter 26, a gas phase external conveying pipeline 27, a liquid level transmitter 28, a ball valve 29, a regulating valve 30, a cement and sand containing pipeline 31, a cement and sand slurry storage tank 32, a liquid level transmitter 33, a cement sand slurry external conveying pump 34, a pressure transmitter 35, a cement sand, Ball valve 37, free water pipeline 38, regulating valve 39, free water storage tank 40, liquid level transmitter 41, free water pipeline 42, free water export pump 43, pressure transmitter 44, free water export pipeline 45, umbilical 46, umbilical junction box 47, hydrate inhibitor pipeline 48, suspending agent pipeline 49, other pipelines 50 and cable 51.
The system comprises an underwater central acquisition system, an acquisition pipeline 101, a reserved acquisition pipeline 102, a pressure transmitter 1, a ball valve 2, an adjusting valve 3, a reserved ball valve 4, a reserved adjusting valve 5 and an underwater manifold 6, wherein the underwater central acquisition system is responsible for receiving natural gas hydrate slurry output by a plurality of underwater natural gas hydrate acquisition wells or devices, and outputting the slurry to a downstream slurry crushing and decomposing system after pressure regulation and convergence; the slurry crushing and decomposing system comprises a collecting pipeline 7, a normally open pipeline 201, a standby pipeline 202, a ball valve 8, a primary crushing system 9, a pressure transmitter 10, a pressure reducing valve 11, a pressure transmitter 12, an expanding reducer 13, a secondary crushing system 14, a ball valve 15, a ball valve 16, a primary crushing system 17, a pressure transmitter 18, a pressure reducing valve 19, a pressure transmitter 20, an expanding reducer 21, a secondary crushing system 22, a ball valve 23 and the like, and is used for continuously turning and stirring the collected natural gas hydrate slurry in a flowing process to perform 2-stage crushing, and promoting natural gas to be separated out in a pressure reducing and heating mode. The separator inlet pipeline 24, the horizontal weir plate separator 25, the pressure transmitter 26 and the like form an underwater separation system which is responsible for buffering and separating natural gas, free water and silt conveyed from the upstream and conveying the separated natural gas, free water and cement-containing sand to the downstream; the gas phase outward conveying pipeline 27, the liquid level transmitter 28, the ball valve 29, the regulating valve 30, the cement and sand containing pipeline 31, the mud and sand slurry storage tank 32, the liquid level transmitter 33, the mud and sand slurry outward conveying pump 34, the pressure transmitter 35, the mud and sand slurry outward conveying pipeline 36, the ball valve 37, the free water pipeline 38, the regulating valve 39, the free water storage tank 40, the liquid level transmitter 41, the free water pipeline 42, the free water outward conveying pump 43, the pressure transmitter 44, the free water outward conveying pipeline 45 and the like form a separate conveying system which is responsible for respectively outward conveying the natural gas, the free water and the mud and sand slurry separated by the horizontal weir plate separator to an offshore treatment facility for further treatment; the umbilical 46, the umbilical distribution box 47, the hydrate inhibitor pipeline 48, the suspending agent pipeline 49, other pipelines 50, the cable 51 and the like form an umbilical system which is responsible for providing the hydrate inhibitor, the slurry suspending agent, other process requirement media, power supply, control communication and other support for underwater production. In addition, the system also comprises a logic control system which is responsible for collecting signals of all the transmitters and is combined with a front-end production instrument to provide instructions for the operation of valves, regulating valves, pumps and the like in the system.
The underwater central acquisition system comprises a ball valve, an adjusting valve, a reserved ball valve, a reserved adjusting valve, an underwater manifold, a pressure transmitter and the like which are arranged underwater, and is used for receiving natural gas hydrate slurry output by a plurality of underwater natural gas hydrate acquisition wells or equipment, and the slurry is output to a downstream slurry crushing and decomposing system after pressure regulation and convergence. The upstream submarine collection pipeline is sequentially connected with the ball valve and the regulating valve and is simultaneously connected with other collection pipelines provided with the reserved ball valve and the regulating valve into an underwater manifold. And a pressure transmitter is arranged at the upstream of the receiving valve group and used for monitoring the pressure before pressure regulation of each collecting pipeline.
Specifically, in the system, the collecting pipeline 101 is a steel pipeline, and a pressure transmitter 1, a ball valve 2 and a regulating valve 3 are sequentially installed; the ball valve 2 is controlled by remote electric control and is responsible for communicating/separating an upstream acquisition pipeline and the system; the regulating valve 3 adopts remote electric control and is responsible for regulating the pressure of the upstream medium so as to match with a downstream production system; the reserved acquisition pipelines 102 are steel pipelines, are in multiple paths, are sequentially provided with reserved ball valves 4 and reserved regulating valves 5, and are temporarily closed by blind flanges; the reserved ball valve 4 is controlled by remote electric control and is responsible for communicating/separating an upstream acquisition pipeline and the system; the reserved regulating valve 5 adopts remote electric control and is responsible for regulating the pressure of the upstream medium so as to match a downstream production system; each pipeline is connected to an underwater manifold 6 which is made of steel, adopts a form of multi-channel inlet and single-channel outlet and is responsible for converging each channel of material flow. Because the system is positioned on the seabed with the water depth of about 1000m, the strength requirements of pipelines and pipe fittings are controlled by external pressure, and in order to simplify the process, an overpressure relief system is not arranged at the upstream of the regulating valve 3 and the reserved regulating valve 5, and the strength of the pipelines and the pipe fittings at the upstream and the downstream of the regulating valve is designed according to the same pressure.
The slurry crushing and decomposing system comprises a primary crushing system, a pressure reducing valve, an expanding large head, a secondary crushing system and a ball valve which are arranged under water, and is used for carrying out primary crushing, pressure reducing gasification decomposition and secondary crushing on the received natural gas hydrate slurry in the conveying process, further promoting gasification decomposition through an underwater heating system, and forming a gas-liquid-sand three-phase dispersing system at the tail end of the system. The primary crushing system is connected with an upstream header; the primary continuous steering system is a pipe system consisting of a plurality of short pipes and bent pipes with small curvature radius and is used for forcibly steering, impacting and crushing the natural gas hydrate slurry, and spoilers are arranged on the inner walls of the outer sides of the bent pipes to promote the crushing effect; a pressure reducing valve is arranged at the downstream of the primary crushing system and is remotely controlled; an expanding large-small head is arranged at the downstream of the pressure reducing valve to expand the pipe diameter of the downstream and properly reduce the flow speed of decomposed natural gas and the flow speed of slurry; the secondary crushing system is arranged at the downstream of the diameter-expanding big end and the diameter-expanding small end, is a pipe system consisting of a plurality of short pipes and bent pipes with small curvature radius, and is used for carrying out secondary crushing on residual slurry and promoting the decomposition of residual natural gas hydrate; the outer surfaces of the primary crushing system and the secondary crushing system are provided with electric heating and heat preservation elements, and the temperature of the fluid is improved through heating, so that the decomposition effect is promoted. Finally, the system discharges the natural gas, free water and silt slurry downstream.
Specifically, in the system, the collecting pipeline 7 is horizontally installed and made of steel, is connected out of the underwater collecting pipe 6 and is divided into a normally open pipeline 201 and a standby pipeline 202, and is installed in parallel to realize 'one use and one standby'; the normally open pipeline 201 is sequentially provided with a ball valve 8, a primary crushing system 9, a pressure transmitter 10, a pressure reducing valve 11, a pressure transmitter 12, an expanding reducer 13, a secondary crushing system 14 and a ball valve 15; the ball valve 8 and the ball valve 15 are controlled by remote electric control and are used for opening and closing the normally open pipeline 201; the primary crushing system 9 is a continuous steering device with alternately arranged straight pipes and bent pipes, the inner wall of the outer side of each bent pipe is welded by adopting a forced turbulence component, and further, a stirring device is arranged in the flowing direction of the fluid of each bent pipe and is electrically driven, so that the slurry in the fluid is crushed for multiple times through the stirring device and the forced turbulence component, and the fluid is promoted to be gasified after passing through the pressure reducing valve 11; the pressure reducing valve 11 is a remote electric control regulating valve, is used for reducing the medium pressure below the natural gas hydrate generation pressure, inducing the natural gas in the natural gas hydrate in the fluid to be gasified, and is matched with the upstream and downstream pressure transmitter 10/12 for real-time monitoring; an expanding large-small head 13 is arranged at the downstream of the pressure reducing valve 11, so that the flow of gas-containing multiphase flow formed after pressure reduction is facilitated; the secondary crushing system 14 is arranged at the downstream of the diameter-expanding reducer 13, has the same function as the primary crushing system 9 in structure, and is used for further promoting gasification of the partial natural gas hydrate slurry blocked by slurry wrapping after pressure reduction; further, an electric heating and heat preservation system is arranged on the normally open pipeline 201 to heat the medium, so that natural gas gasification is promoted. Similarly, the standby line 202 and its installed valves, pipes, etc. are identical to the normally open line 201, but are in a closed state.
And the underwater separation system comprises a horizontal weir plate separator and a matched pipeline which are arranged underwater, and is used for buffering and separating natural gas, free water and silt which are conveyed from the upstream and conveying the separated natural gas, free water and cement-containing sand to the downstream. The liquid content in the silt slurry can be controlled by adjusting the discharge capacity of the external delivery pumps of the free water outlet pipeline and the silt slurry outlet pipeline, and the performance of the silt suspension liquid obtained by mixing the silt slurry and the suspending agent can be further controlled. And the horizontal weir plate separator is internally provided with a middle weir plate for preventing silt from entering a free water storage area.
Specifically, in the illustrated system, the separator inlet pipeline 24 is a steel pipeline, and a junction pipe of the normally open pipeline 201 and the standby pipeline 202 is connected to the upstream of the steel pipeline and is connected to the horizontal weir plate separator 25; the horizontal weir plate separator 25 is a horizontal three-phase separator and is used for separating a natural gas-free water-silt system generated after upstream depressurization and heating; a weir plate is arranged in the horizontal weir plate separator 25 and is used for dividing a cement sand containing area and a free water area, the horizontal position of the weir plate is determined according to the sedimentation speed of the silt, and the height of the weir plate is not more than 50% of the inner diameter of the separator; the horizontal weir plate separator 25 adopts single liquid level control, a liquid level transmitter 28 is arranged, the normal liquid level is higher than the weir plate and is 55 percent of the inner diameter of the separator, and the liquid level is controlled in real time; according to production requirements, the discharge capacity of cement-containing sand and free water can be dynamically distributed, and the process is controlled by a downstream regulating valve and an output pump; the bottom of the separator is provided with a cement-containing sand outlet and a free water outlet; the separator is provided with a pressure transmitter 26; the horizontal weir plate separator 25 and the inlet and outlet piping system adopt a modularized prying structure, so that the hoisting and the replacement are convenient.
And the separate transportation system comprises a gas phase external transportation pipeline, a free water storage tank, a free water external transportation pump, a free water external transportation pipeline, a cement and sand containing storage tank, a mud and mortar liquid external transportation pump, a mud and mortar liquid external transportation pipeline and the like, and is used for respectively transporting the natural gas, the free water and the mud and sand liquid separated by the horizontal weir plate separator out, and transporting the natural gas, the free water and the mud and sand liquid to an offshore treatment facility for further treatment. The gas phase outward conveying pipeline is connected with a gas phase outlet of the horizontal weir plate separator and comprises a gas phase outward conveying submarine pipeline and a gas phase vertical pipe; the gas phase external transportation submarine pipeline adopts a flexible pipe or a steel pipeline; the gas phase riser may be in the form of an SCR or a flexible pipe. The free water storage tank is connected with an upstream free water pipeline to play a role in buffering; the downstream is provided with a free water outward-conveying pump in the form of an electric reciprocating pump; the free water outward transport pipeline is connected with a free water storage tank and comprises a free water outward transport submarine pipeline and a free water vertical pipe; the free water outward-conveying submarine pipeline adopts a flexible pipe or a steel pipeline; the free water riser may be in the form of an SCR or flexible pipe. The free water storage tank is connected with an upstream pipeline containing cement and sand, plays a role of buffering, and is mixed with suspension liquid provided at sea before entering the storage tank to form cement and sand slurry; a mud-sand slurry outward-conveying pump is arranged at the downstream, and the type of the mud-sand slurry outward-conveying pump is an electric reciprocating pump; the mud slurry outward conveying pipeline is connected with a mud slurry storage tank and comprises a mud slurry outward conveying submarine pipeline and a mud slurry vertical pipe; the submarine pipeline for transporting the mud slurry out adopts a flexible pipe or a steel pipeline; the silt slurry riser may be in the form of an SCR or flexible pipe.
Specifically, in the illustrated system, the gas phase export pipeline 27 comprises a submarine pipeline and a riser, and can be a steel pipeline or a flexible pipeline, and is responsible for transporting the natural gas separated by the horizontal weir plate separator 25 to an offshore processing facility; the ball valve 29 and the regulating valve 30 are arranged on a cement-sand-containing pipeline 31, are controlled by remote electric control and are responsible for opening and closing of the pipeline and flow regulation; the mud-sand slurry storage tank 32 receives mud-sand slurry obtained after the pipeline 31 containing the mud-sand and the pipeline 49 containing the suspending agent are intersected, the form of the mud-sand slurry is a vertical tank, a liquid level transmitter 33 is arranged, the normal liquid level is 70% of the height inside the tank body, and the continuous operation control is performed; the mud-sand slurry outward-conveying pump 34 is a screw pump, is electrically driven, is responsible for conveying the mud-sand slurry after being pressurized, and is conveyed to an offshore treatment facility through a mud-sand slurry outward-conveying pipeline 36; the external mud slurry transportation pipeline 36 comprises a submarine pipeline and a vertical pipe, and can adopt a steel pipeline or a flexible pipeline; the ball valve 37 and the regulating valve 39 are installed on the free water pipeline 38, are controlled by remote electric control and are responsible for opening and closing of the pipeline and flow regulation; the free water storage tank 40 receives the separated free water, is in the form of a vertical tank, is provided with a liquid level transmitter 41, has a normal liquid level of 70% of the internal height of the tank body, and is used for continuous operation control; the free water outward conveying pump 43 is a screw pump and is electrically driven, is responsible for conveying the pressurized free water to an offshore treatment facility through a free water outward conveying pipeline 45; the free water export pipeline 45 comprises a submarine pipeline and a vertical pipe, and can adopt a steel pipeline or a flexible pipeline; further, an interface is arranged on the free water pipeline 42, and hydrate inhibitors injected by the hydrate inhibitor pipeline 48 are received, so that secondary generation of hydrates in the free water delivery pipeline 45 caused by pressurization is prevented; furthermore, the silt body storage tank 32 and the free water storage tank 40 adopt modularized prying structures, so that the hoisting and the replacement are convenient; further, the mud slurry out-feed pump 34 and the free water out-feed pump 43 may be optionally installed in a pressure-resistant casing, resisting high pressure outside the deepwater.
And fifthly, the umbilical cable system comprises a hydrate inhibitor injection pipeline, a suspension injection pipeline, and various pipelines and cables for assisting underwater production. The hydrate inhibitor injection pipeline is connected with a pipeline in front of a free water outward delivery pump, so that secondary hydrate generation caused by high pressure of a small amount of natural gas possibly carried in free water after pressurization is prevented. The suspension injection pipeline is connected with an inlet pipeline of the mud slurry storage tank so as to form mud slurry with the contained mud and sand and limit the deposition of the mud and sand in subsequent transportation. The auxiliary underwater production pipeline and the cable provide necessary process, power supply, communication and control support for underwater production.
Specifically, in the illustrated system, an umbilical 46 is connected to the offshore production facility, provides chemicals, other process auxiliary media and cables to the water, and is connected to an umbilical connection box 47; the umbilical connection box 47 branches off a hydrate inhibitor conduit 48, a suspension agent conduit 49, other conduits 50, and a cable 51; the hydrate inhibitor pipeline 48 is a steel pipeline, is connected to the free water pipeline 42, and is responsible for providing hydrate inhibitors for the free water before pressurization; the suspending agent pipeline 49 is connected to the cement-containing sand pipeline 31 and is responsible for providing suspending agent for cement-containing sand to form a mud-sand slurry body with better suspension property, so that the pressurized vertical pipe can be conveniently conveyed; the other pipelines 50 are other process pipes, and the number is determined according to the front-end production requirement; the cables 51 are cables for underwater power supply, control signals, communication signals and the like, and the number of the cables is determined according to production requirements.
And sixthly, the logic control system comprises an overall control system of an underwater central acquisition system, an underwater separation system, a distribution system, an umbilical cable system and a front-end wellhead acquisition system, provides signals for the transmitters in the systems, combines underground instrument control signals, and provides operation instructions for safety valves, regulating valves, pumps and the like in the system.
The utility model discloses a theory of operation does:
the natural gas hydrate slurry produced by adopting a fluidized mining mode is connected into an underwater manifold 6 through a multi-path collecting pipeline after pressure regulation; after being crushed and heated by a primary crushing system 9 of the normally open pipeline 201, the temperature of the medium is increased, and the unit volume of the slurry is reduced; further reducing the pressure through a pressure reducing valve 11 to reach the natural gas gasification condition, processing the natural gas by a secondary crushing system 14 again to form a dispersed natural gas, free water and silt system, and feeding the dispersed natural gas, free water and silt system into a horizontal weir plate separator 25; the medium is separated in a horizontal weir plate separator 25, the gas phase enters the offshore treatment facility through a gas phase outward conveying pipeline 27, and after sedimentation, the silt is gathered at the front end area of the weir plate, and free water also exists in the area; the rear end area of the weir plate is free water; through the design of the production scheme, the cement-containing sand and the free water are respectively discharged outside through a pipeline, the total discharge amount is basically constant, the liquid level in the separator is ensured to be controlled at the position of 55% of the inner diameter, and the relative discharge amount of the cement-containing sand and the free water can be adjusted; the discharged mud-containing sand is mixed with a suspending agent injected at sea to form mud-sand slurry with better fluidity, and after being buffered by a mud-sand slurry storage tank 32, the mud-sand slurry is pressurized by a mud-sand slurry outward conveying pump 34 and is input into a mud-sand slurry outward conveying pipeline 36, and finally the mud-sand slurry reaches an offshore production facility; the discharged free water is buffered by the free water storage tank 40, mixed with the hydrate inhibitor injected at sea, pressurized by the free water delivery pump 43 and delivered into the free water delivery pipeline 45, and finally delivered to the offshore production facility.
The method for underwater production of natural gas hydrate by using the utility model comprises the following main contents:
the method comprises the following steps: the sea area natural gas hydrate development is carried out according to the principle of fluidized exploitation of natural gas hydrate, namely, the hydrate is stored and crushed on the surface of the seabed or shallow layer, high-pressure liquid is introduced for mixing to form natural gas hydrate slurry, and the natural gas hydrate slurry is conveyed to an underwater central processing facility on the surface of the seabed through a shaft and a collecting pipeline for further processing.
Step two: during normal production, the ball valve 2 and the regulating valve 3 at the inlet of the collecting pipeline are opened, the pressure in front of the valves is controlled by the regulating valve, the pressure meets the requirement of remote production, and when a plurality of collecting pipelines run, the regulating valves of all paths are cooperatively controlled to ensure that the pressure is consistent after all paths are converged; opening a primary crushing system inlet ball valve 8 and a heating system, and continuously heating the natural gas hydrate slurry through multiple turning to realize primary crushing and temperature increase of the slurry; opening the pressure reducing valve 11 to reduce the pressure of the natural gas hydrate slurry to achieve the gasification condition; the gasified multiphase medium is further crushed by a secondary crushing system, and simultaneously, the temperature is raised again, and the gasified multiphase medium enters a horizontal weir plate separator 25. Opening ball valves of outlet pipelines of each path of the horizontal weir plate separator, and allowing natural gas to flow out of the gas phase pipeline 27 and enter an offshore production facility; after the free water turns over the weir plate, the free water enters a free water storage tank 40 from a free water pipeline 38, and after pressurization, the free water enters a free water outward conveying pipeline 45 and is conveyed to an offshore production facility; the silt is separated by the weir plate, and after being mixed with part of the free water, the silt is discharged from the silt-containing pipeline 31, the suspension pipeline 49 in the umbilical cable is opened, silt suspending agent is injected into the silt-containing pipeline to promote the even dispersion of the silt, the sedimentation of the silt is inhibited, the formed silt slurry enters the silt slurry storage tank 32, and the silt slurry outward-conveying pump 34 is further opened to convey the silt slurry to the offshore treatment facility through the silt slurry vertical pipe 36.
Step three: further, when the offshore facility monitors that the content of the silt in the silt slurry is increased or the flow of the silt slurry outlet fluctuates greatly, the increase of the yield of the silt or the insufficient supply of the liquid phase is indicated. The discharge capacity of a pipeline containing the silt and sand of the horizontal weir plate separator is increased, the discharge capacity of a free water pipeline is reduced, and meanwhile, the delivery capacity of a suspending agent pipeline of the umbilical cable is increased, so that the problem of increasing the yield of the silt and sand is solved.
Step four: further, when the offshore facility monitors a decrease in the content of silt in the silt slurry, it indicates that the silt production is reduced or the free water pipeline transport capacity can be increased. Reduce the cement sand containing pipeline discharge capacity of horizontal weir plate separator, improve free water pipeline discharge capacity, reduce the suspending agent pipeline output of umbilical cable simultaneously to alleviate the problem that silt particle output reduces, practice thrift the energy consumption.
Step five: further, when the liquid level of the horizontal weir plate separator is lower than the height of the weir plate, the discharge capacity of the cement-sand containing pipeline and the free water pipeline is reduced to restore the liquid level, and the normal liquid level is kept 0.5m higher than the weir plate.
Step six: in production, if the free water delivery pipeline has the risk of secondary hydrate generation, the hydrate inhibitor pipeline 48 of the umbilical cable is opened, and hydrate inhibitors are injected into the free water pipeline entering the pump, so that the flowing risk is reduced.
Claims (9)
1. A natural gas hydrate underwater production system based on fluidization exploitation is characterized in that: including central collection system, broken and decomposition system of slurry, underwater separation system, branch transmission system and umbilical cable system under water, wherein:
the underwater central acquisition system is used for regulating pressure and collecting the received natural gas hydrate slurry and then transmitting the slurry to the slurry crushing and decomposing system;
the slurry crushing and decomposing system is used for carrying out primary crushing, depressurization gasification decomposition, secondary crushing and heating gasification decomposition on the received natural gas hydrate slurry in the conveying process to obtain a natural gas, free water and silt three-phase dispersing system;
the underwater separation system is used for buffering and separating natural gas, free water and silt conveyed from the upstream and conveying separated natural gas, free water and silt slurry to the downstream;
the separate transportation system is used for respectively transporting the separated natural gas, free water and silt slurry to an offshore treatment facility;
the umbilical cable system is used for providing hydrate inhibitors, mud suspending agents, process demand media, power supply, control and communication support for underwater production;
the underwater central acquisition system, the underwater separation system, the sub-transmission system and the umbilical cable system are respectively connected with the logic control system.
2. The subsea production system of natural gas hydrates based on fluidized production according to claim 1, characterized in that: the underwater central acquisition system comprises an acquisition pipeline and at least one reserved acquisition pipeline, wherein a pressure transmitter, a ball valve and an adjusting valve are sequentially installed on the acquisition pipeline, the reserved ball valve and the reserved adjusting valve are installed on the reserved acquisition pipeline, and the acquisition pipeline and the reserved acquisition pipeline are both connected into an underwater manifold.
3. The subsea production system of natural gas hydrates based on fluidized production according to claim 2, characterized in that: the collecting pipeline and the reserved collecting pipeline are both steel pipelines; the ball valve and the reserved ball valve are both controlled by remote electric control and are responsible for communicating/separating the upstream acquisition pipeline and the system; the regulating valve and the reserved regulating valve are remotely and electrically controlled and are responsible for regulating the pressure of the upstream incoming medium to match with a downstream production system; the reserved acquisition pipeline is temporarily closed by adopting a blind flange; the underwater manifold is made of steel and adopts a form of a multi-path inlet and a single-path outlet.
4. The subsea production system of natural gas hydrates based on fluidized production according to claim 1, characterized in that: the slurry crushing and decomposing system comprises a collecting pipeline, a normally open pipeline and a standby pipeline, wherein the normally open pipeline and the standby pipeline are separated from the collecting pipeline, and an upstream ball valve, a primary crushing system, a pressure transmitter, a pressure reducing valve, a pressure transmitter, an expanding reducer, a secondary crushing system and a downstream ball valve are sequentially arranged on the normally open pipeline and the standby pipeline.
5. The subsea production system of natural gas hydrates based on fluidized production according to claim 4, characterized in that: the upstream ball valve and the downstream ball valve are remotely electrically controlled and are used for opening and closing a pipeline; the primary crushing system and the secondary crushing system are both continuous steering devices with alternately arranged straight pipes and bent pipes, the inner wall of the outer side of each bent pipe is welded by adopting a forced turbulence component, and an electrically driven stirring device is arranged in the flowing direction of the fluid of each bent pipe; the pressure reducing valve is a remote electric control regulating valve; an electric heating and heat preservation system is arranged on the normally open pipeline.
6. The subsea production system of natural gas hydrates based on fluidized production according to claim 1, characterized in that: the underwater separation system comprises a horizontal weir plate separator, wherein a weir plate is arranged in the horizontal weir plate separator, and the height of the weir plate is not more than 50% of the inner diameter of the separator; a liquid level transmitter is arranged in the horizontal weir plate separator, and the normal liquid level of the liquid level transmitter is 55% of the inner diameter of the separator; a cement-containing sand outlet and a free water outlet are arranged at the bottom of the horizontal weir plate separator; and a pressure transmitter is arranged on the horizontal weir plate separator.
7. The subsea production system of natural gas hydrates based on fluidized production according to claim 1, characterized in that: the separate transportation system comprises a gas phase external transportation pipeline, a free water external transportation pipeline and a mud slurry liquid external transportation pipeline; the free water outward conveying pipeline is sequentially provided with a ball valve, an adjusting valve, a free water storage tank and a free water outward conveying pump; and the mud mortar liquid outward conveying pipeline is sequentially provided with a ball valve, an adjusting valve, a mud mortar body storage tank and a mud mortar body outward conveying pump.
8. The subsea production system of natural gas hydrates based on fluidized production according to claim 7, wherein: the ball valves and the regulating valves arranged on the free water outward conveying pipeline and the mud slurry outward conveying pipeline are controlled by remote electric control and are responsible for opening and closing of the pipelines and flow regulation; the free water storage tank and the mud-mortar body storage tank are both vertical tanks and are respectively provided with a liquid level transmitter, and the normal liquid level of the liquid level transmitter is 70% of the height of the interior of the tank body; the free water outward conveying pump and the mud and sand slurry outward conveying pump are electric-driven screw pumps.
9. The subsea production system of natural gas hydrates based on fluidized production of claim 8, wherein: the umbilical system comprises an umbilical connection box, an umbilical connected to the umbilical connection box and used for connecting an offshore production facility, and a hydrate inhibitor pipeline, a suspending agent pipeline, a cable and a process pipe which are separated from the umbilical connection box; the hydrate inhibitor pipeline is connected with an interface arranged on the free water pipeline; the suspending agent pipeline is connected to a cement-containing sand pipeline of the mud-sand slurry storage tank; the cable is used for underwater power supply, control signals and communication signals.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110374557A (en) * | 2019-08-01 | 2019-10-25 | 中国石油工程建设有限公司 | A kind of gas hydrates subsea production system and method based on fluidisation exploitation |
| CN110374557B (en) * | 2019-08-01 | 2024-06-11 | 中国石油工程建设有限公司 | Natural gas hydrate underwater production system and method based on fluidization exploitation |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110374557A (en) * | 2019-08-01 | 2019-10-25 | 中国石油工程建设有限公司 | A kind of gas hydrates subsea production system and method based on fluidisation exploitation |
| CN110374557B (en) * | 2019-08-01 | 2024-06-11 | 中国石油工程建设有限公司 | Natural gas hydrate underwater production system and method based on fluidization exploitation |
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