阅读说明：本技术 一种海相天然气水合物的开采方法及开采装置 (Exploitation method and exploitation device for marine natural gas hydrate ) 是由 李小森 申鹏飞 李刚 陈朝阳 张郁 王屹 刘建武 于 2019-11-14 设计创作，主要内容包括：本发明公开了一种海相天然气水合物的开采方法及开采装置。该开采方法,包括如下步骤：(1)完成垂直井的构建后构造固定管,固定管中心设置开采井,固定管内壁和开采井外壁之间填充混合均匀的混合物；(2)自激振荡射流喷嘴沿垂直井进入到开采井内,通过开采井上的孔口到达指定位置对混合物进行喷射,进而使得混合物均匀打碎,形成人造裂缝；(3)在相应温度之下,进行降压开采,水合物分解产气；(4)开采井开采出来的气液混合物在气液分离装置内进行分离得到液体和气体,收集得到的液体和气体。本发明提出的开采方法有稳定降压开采、提高开采效率、高浓度天然气的回收、自动化操作和远程控制的优点,能为海相天然气水合物的开采提供指导。(The invention discloses a method and a device for exploiting marine natural gas hydrate. The mining method comprises the following steps: (1) constructing a fixed pipe after the construction of the vertical well is completed, arranging a production well in the center of the fixed pipe, and filling a uniformly mixed mixture between the inner wall of the fixed pipe and the outer wall of the production well; (2) the self-oscillation jet nozzle enters the exploitation well along the vertical well, and reaches a designated position through an orifice on the exploitation well to jet the mixture, so that the mixture is uniformly broken to form artificial cracks; (3) carrying out decompression exploitation under the corresponding temperature, and decomposing the hydrate to generate gas; (4) and separating the gas-liquid mixture produced by the production well in a gas-liquid separation device to obtain liquid and gas, and collecting the obtained liquid and gas. The exploitation method provided by the invention has the advantages of stable decompression exploitation, improvement of exploitation efficiency, recovery of high-concentration natural gas, automatic operation and remote control, and can provide guidance for exploitation of marine natural gas hydrate.)

1. A method for exploiting marine natural gas hydrates is characterized by comprising the following steps:

(1) constructing an artificial sand control well wall: when a hydrate production area is exploited, a vertical well is constructed firstly, after the vertical well reaches a hydrate layer, a fixed pipe is arranged in the hydrate layer, an exploitation well is arranged at the center of the fixed pipe, a mixture of uniformly mixed hydrophobic porous materials and inorganic permeable concrete reinforcing agents is filled between the inner wall of the fixed pipe and the outer wall of the exploitation well, and the mixture is cemented and molded to form the artificial sand control well wall;

(2) the hydraulic jet permeability-increasing artificial sand-prevention well wall: the self-oscillation jet nozzle enters the exploitation well of the fixed pipe along the vertical well, and the mixture is sprayed at a specified position through an orifice on the exploitation well, so that the mixture formed by cementing is uniformly crushed to form an artificial crack;

(3) and (3) depressurization mining: under the corresponding temperature, when the exploitation pressure is lower than the pressure of the natural gas hydrate phase equilibrium, the hydrate decomposes to produce gas, the intelligent control system judges the start and stop of the heating device and the inhibitor circulating device according to the conditions of the temperature sensor and the pressure sensor, when the temperature and pressure corresponding points measured by the temperature sensor and the pressure sensor are under the natural gas hydrate phase equilibrium, the heating device and the inhibitor circulating device are automatically started, the heating device continuously heats the outer layer of the fixed pipe, and an inhibitor nozzle in the inhibitor circulating device sprays the inhibitor to the wellhead of the exploitation well to inhibit the formation of the outer layer of the fixed pipe and the secondary hydrate at the bottom of the well;

(4) gas-liquid separation: the gas-liquid mixture that the exploitation well was mined out separates in gas-liquid separation device and obtains liquid and gas, and liquid discharges to the upper mud layer from the fluid-discharge outlet, and gas follows vertical well from the gas outlet and reaches the gas plenum chamber, and when pressure was higher than the set pressure value, gas rose to offshore platform, accomplished gaseous collection.

2. The exploitation method of marine natural gas hydrate according to claim 1, wherein the mass ratio of the hydrophobic porous material to the inorganic water-permeable concrete reinforcing agent in the mixture of the hydrophobic porous material and the inorganic water-permeable concrete reinforcing agent is 1000:1 to 10: 1.

3. A method for producing marine natural gas hydrates according to claim 1, wherein the production well is a vertical production well or a horizontal production well.

4. An offshore natural gas hydrate exploitation device for implementing the offshore natural gas hydrate exploitation method according to claim 1, comprising an artificial sand control borehole wall system, a hydraulic jet permeability increasing system, a depressurization exploitation system and a gas-liquid separation control system; the artificial sand control well wall system comprises a fixed pipe buried in a hydrate layer, and the hydraulic jet permeability increasing system comprises a self-oscillation jet nozzle; the pressure reduction mining system comprises a vertical well, a mining well arranged in the center of a fixed pipe, a heating device arranged outside the fixed pipe and an inhibitor circulating device arranged outside the fixed pipe, wherein the inhibitor circulating device comprises an inhibitor nozzle arranged outside the mining well and an inhibitor recovery bin arranged outside the fixed pipe; the gas-liquid separation control system comprises a gas-liquid separation device, a gas pressurizing chamber and an intelligent control system, the intelligent control system judges the start and stop of the heating device and the inhibitor circulating device according to the conditions of a temperature sensor and a pressure sensor which are arranged outside the fixed pipe, a gas-liquid mixture which is mined from the mining well is separated in the gas-liquid separation device to obtain liquid and gas, the liquid is discharged to an upper mud layer from a liquid discharge port, the gas reaches the gas pressurizing chamber from a gas outlet along a vertical well, and when the pressure is higher than a set pressure value, the gas rises to an offshore platform to finish the collection of the gas.

5. An apparatus for producing marine natural gas hydrate as claimed in claim 4, wherein the production well is externally provided with an inner net and an outer net for preventing the ultrafine particles from being mixed into the horizontal production well, and the inner net and the outer net are provided with openings for the inflow of gas-liquid mixture.

6. An exploitation device of marine natural gas hydrate according to claim 5, wherein the temperature raising device is a heating wire, the heating wire is uniformly arranged on the outer layer of the fixed pipe, and when the corresponding points of the temperature and the pressure measured by the temperature sensor and the pressure sensor are below the phase equilibrium of the natural gas hydrate, the heating wire continuously heats the outer layer of the fixed pipe, so as to break hydrates generated on the outer layer of the fixed pipe and ensure that gas enters the exploitation well from the orifice of the exploitation well.

7. An exploitation device of marine natural gas hydrate according to claim 4, wherein a mixture of a hydrophobic porous material and an inorganic water-permeable concrete reinforcing agent is filled between the inner wall of the fixed pipe and the outer wall of the exploitation well.

The technical field is as follows:

the invention belongs to the technical field of energy, and particularly relates to a method and a device for exploiting marine natural gas hydrate.

Background art:

the natural gas hydrate is an ice-like crystalline substance formed by natural gas and water under high-pressure and low-temperature conditions, is called as 'combustible ice' because the natural gas hydrate has the same appearance as ice and can be combusted when meeting fire, has high resource density, wide global distribution and extremely high resource value, is considered as one of new energy sources with application prospects and capable of replacing fossil energy such as petroleum, and is officially approved to be listed as a new mineral species in 11-3.2017 by the national institute, so that the natural gas hydrate becomes the 173 th mineral species in China.

A natural gas hydrate pressure-reducing exploitation method is an exploitation method which utilizes the pressure of a hydrate reservoir to destroy the phase equilibrium stability of the hydrate, and further promotes the decomposition of the hydrate, and is the most promising development of all exploitation methods, so that the method can become one of effective methods for exploiting the natural gas hydrate on a large scale in the future. In 2013, combustible ice is mined at the sea bottom of 70 km in south and 1000 m in depth in Woman of Aizhi county in Japan, 12 ten thousand cubic meters of natural gas is successfully mined within 6 days, and the country for mining the combustible ice at the sea bottom for the first time in the world becomes, and the mining end in 6 days is mainly caused by the blockage of a drilling channel by silt, so that a mining well is blocked, and gas cannot be produced. In 28 th 3 th 2017, in Shenhu sea area at 320 km south north of south of east of Zhuhai city, China, drilling of a first mouth test production well is started, the first mouth test production well works after ignition at 14 pm in 5 th 10 th 5 th, natural gas is mined from natural gas hydrate ore deposit with 277 m of 203-. For the two times of exploitation of the seabed natural gas hydrate reservoir, the adopted methods are decompression exploitation, and the conditions that the exploitation well is blocked by seabed sediment and the exploitation efficiency is low exist.

The reason that the exploitation efficiency of the low-permeability marine phase sediment is low is deeply analyzed, and the fact that the phase balance condition of the natural gas hydrate is damaged by the pressure reduction of the pressure reduction exploitation method to cause the decomposition of the hydrate is found, but for the low-permeability marine phase sediment, the traditional hydraulic fracturing cannot cause the permeability of a reservoir to be improved, because cracks caused by the hydraulic fracturing are quickly filled and sealed by ultrafine particles such as silty sand and the like, the permeability of the hydrate reservoir determines the success or failure of the pressure reduction exploitation, and meanwhile, a large number of researches show that the increase of the pressure reduction amplitude can cause the generation of a large number of secondary hydrates, so that the key for exploiting the marine phase natural gas hydrate is that how to improve the permeability of the reservoir is guaranteed not to be blocked by the silt and the generation of the.

The invention content is as follows:

the invention aims to overcome the defects of the prior art and provides a method and a device for exploiting marine natural gas hydrate.

The invention aims to provide a method for exploiting a marine natural gas hydrate, which comprises the following steps:

(1) constructing an artificial sand control well wall: when a hydrate production area is exploited, a vertical well is constructed firstly, after the vertical well reaches a hydrate layer, a fixed pipe is arranged in the hydrate layer, an exploitation well is arranged at the center of the fixed pipe, a mixture of uniformly mixed hydrophobic porous materials and inorganic permeable concrete reinforcing agents is filled between the inner wall of the fixed pipe and the outer wall of the exploitation well, and the mixture is cemented and molded to form the artificial sand control well wall;

(2) the hydraulic jet permeability-increasing artificial sand-prevention well wall: the self-oscillation jet nozzle enters the exploitation well of the fixed pipe along the vertical well, and the mixture is sprayed at a specified position through an orifice on the exploitation well, so that the mixture formed by cementing is uniformly crushed to form an artificial crack;

(3) and (3) depressurization mining: under the corresponding temperature, when the exploitation pressure is lower than the pressure of the natural gas hydrate phase equilibrium, the hydrate decomposes to produce gas, the intelligent control system judges the start and stop of the heating device and the inhibitor circulating device according to the conditions of the temperature sensor and the pressure sensor, when the temperature and pressure corresponding points measured by the temperature sensor and the pressure sensor are under the natural gas hydrate phase equilibrium, the heating device and the inhibitor circulating device are automatically started, the heating device continuously heats the outer layer of the fixed pipe, and an inhibitor nozzle in the inhibitor circulating device sprays the inhibitor to the wellhead of the exploitation well to inhibit the formation of the outer layer of the fixed pipe and the secondary hydrate at the bottom of the well;

(4) gas-liquid separation: the gas-liquid mixture that the exploitation well was mined out separates in gas-liquid separation device and obtains liquid and gas, and liquid discharges to the upper mud layer from the fluid-discharge outlet, and gas follows vertical well from the gas outlet and reaches the gas plenum chamber, and when pressure was higher than the set pressure value, gas rose to offshore platform, accomplished gaseous collection.

In the step (1), the diameter of the fixed pipe is determined according to the seepage condition of a hydrate layer, the constructed fixed pipe is filled with the hydrophobic porous material and the inorganic pervious concrete reinforcing agent, the hydrophobic porous material and the inorganic pervious concrete reinforcing agent are uniformly mixed and filled in the whole fixed pipe and are glued and formed, and the step aims to utilize the pores of the hydrophobic porous material to block sea mud outside the fixed pipe through decomposed gas and liquid.

The artificial cracks in the step (2) are used for improving the permeability of the periphery of the production well and improving the gas production efficiency.

In the step (3), under the corresponding temperature and when the exploitation pressure is lower than the phase equilibrium pressure of the natural gas hydrate, the hydrate is decomposed to generate gas, because the ambient temperature is reduced in the hydrate decomposition process, the pressure of the natural gas hydrate phase equilibrium is reduced, this leads to the easy occurrence of secondary hydrate on the walls of the production well and the fixed pipe, which causes the blockage of the pipe body, therefore, the intelligent control system is adopted, the intelligent control system can judge the start and stop of the temperature rising device and the inhibitor circulating device according to the conditions of the temperature sensor and the pressure sensor, when the corresponding points of temperature and pressure are below the natural gas hydrate phase equilibrium, the heating device and the inhibitor circulating device are automatically started to continuously heat the outer layer of the fixed pipe, and meanwhile, the inhibitor is sprayed to the wellhead of the production well, so that the formation of secondary hydrates on the outer layer of the fixed pipe and the bottom of the well is effectively inhibited.

Preferably, the mass ratio of the hydrophobic porous material to the inorganic water-permeable concrete reinforcing agent in the mixture of the hydrophobic porous material and the inorganic water-permeable concrete reinforcing agent is 1000:1-10: 1.

Preferably, the production well is a vertical production well or a horizontal production well.

The invention also protects the exploitation device of the marine natural gas hydrate for realizing the exploitation method of the marine natural gas hydrate, which comprises an artificial sand control well wall system, a hydraulic jet permeability increasing system, a depressurization exploitation system and a gas-liquid separation control system; the artificial sand control well wall system comprises a fixed pipe buried in a hydrate layer, and the hydraulic jet permeability increasing system comprises a self-oscillation jet nozzle; the pressure reduction mining system comprises a vertical well, a mining well arranged in the center of a fixed pipe, a heating device arranged outside the fixed pipe and an inhibitor circulating device arranged outside the fixed pipe, wherein the inhibitor circulating device comprises an inhibitor nozzle arranged outside the mining well and an inhibitor recovery bin arranged outside the fixed pipe; the gas-liquid separation control system comprises a gas-liquid separation device, a gas pressurizing chamber and an intelligent control system, the intelligent control system judges the start and stop of the heating device and the inhibitor circulating device according to the conditions of a temperature sensor and a pressure sensor which are arranged outside the fixed pipe, a gas-liquid mixture which is mined from the mining well is separated in the gas-liquid separation device to obtain liquid and gas, the liquid is discharged to an upper mud layer from a liquid discharge port, the gas reaches the gas pressurizing chamber from a gas outlet along a vertical well, and when the pressure is higher than a set pressure value, the gas rises to an offshore platform to finish the collection of the gas.

Preferably, the exterior of the production well is provided with an inner net and an outer net which prevent the ultrafine particles from being mixed into the horizontal production well, and the inner net and the outer net are both provided with orifices for the inflow of the gas-liquid mixture.

Further preferably, the rising temperature device be the heater strip, the heater strip evenly set up in the skin of fixed pipe, when the temperature that temperature sensor and pressure sensor measured and the corresponding point of pressure are under natural gas hydrate phase equilibrium, the heater strip is the skin continuous heating of fixed pipe, breaks the hydrate that generates at the fixed pipe skin, guarantees that gas gets into the exploitation well from the drill way of exploitation well.

Heating wires are uniformly arranged on the outer layer of the fixed pipe, the intelligent control system can judge the start and stop of the heating device according to the conditions of the temperature sensor and the pressure sensor, and when the corresponding point of the temperature and the pressure is below the balance of the natural gas hydrate, the heating device is automatically started to continuously heat the outer layer of the fixed pipe, so that the hydrate generated on the outer layer of the fixed pipe is broken, and the gas can enter the exploitation well from the orifice; the gas-liquid mixture that is mined out from the exploitation well is separated in the gas-liquid separation device, and liquid discharges to the upper mud layer from the drain outlet, and gas reaches the gas plenum chamber along vertical well from the gas outlet, and when pressure was higher than the set pressure value, gas rose to offshore platform.

Preferably, a mixture of a hydrophobic porous material and an inorganic permeable concrete reinforcing agent is filled between the inner wall of the fixed pipe and the outer wall of the production well. The hydrophobic porous material has no affinity to water, the inorganic permeable concrete reinforcing agent and the hydrophobic porous material are aggregated in water to form a hydrated body of a high molecular polymer, the hydrated body is not easily dispersed by water, the compression resistance and the bonding strength of the hydrated body are greatly improved, and the freeze-thaw resistance, the durability and the weather resistance of the hydrophobic porous material are enhanced.

The fixed pipe is pre-embedded in a hydrate layer in advance, the mining well is sleeved inside the fixed pipe, the hydrophobic porous material from the hydrophobic porous material bin is mixed with the inorganic permeable concrete reinforcing agent from the inorganic permeable concrete reinforcing agent storage tank, then the mixture enters and fills the space between the outer wall of the whole mining well and the inner wall of the fixed pipe through the vertical well under the action of a hydraulic pressure booster, and the mixture is glued and molded under the action of the inorganic permeable concrete reinforcing agent; the self-oscillation jet nozzle can directionally move in the fixed pipe and the production well, and can reach a designated position to spray the hydrophobic porous material according to requirements, so that the hydrophobic porous material which is formed by cementing with the inorganic permeable concrete reinforcing agent is uniformly broken to form artificial cracks; the inhibitor circulating device can control the opening and the stopping of the inhibitor nozzle by an intelligent control system, when the inhibitor nozzle is opened, the inhibitor is sprayed to the wellhead of the production well to inhibit the formation of secondary hydrate at the bottom of the well, and when the inhibitor nozzle is stopped, redundant inhibitor is delivered to the inhibitor recovery bin.

The invention has the beneficial effects that: the mining method provided by the invention can realize automatic operation and remote control, can effectively prevent the sand production of the mining well, improve the permeability of the periphery of the mining well, inhibit the generation of secondary hydrate in the mining well, realize stable decompression mining, improve the mining efficiency and recover high-concentration natural gas.

Description of the drawings:

fig. 1 is a schematic structural view of an apparatus for producing marine natural gas hydrate according to the present invention, in which dashed arrows indicate gas-liquid flow directions;

FIG. 2 is a schematic view of the longitudinal section of the fixing tube in FIG. 1;

description of reference numerals:

1. producing a cell boundary; 2. a sea water layer; 3. applying a mud layer; 4. a hydrate layer; 5. a mud layer is laid; 6. a self-oscillating jet nozzle; 7. a horizontal production well; 8. a fixed tube; 8-1, fixing the outer layer of the pipe; 8-2, fixing the inner layer of the tube; 9. an orifice; 10. a hydrophobic porous material; 11. artificial cracks; 12. a hydraulic jet hose; 13. an inhibitor recovery bin; 14. an inhibitor nozzle; 15. a temperature sensor; 16. a pressure sensor; 17. a temperature raising device; 18. a liquid discharge port; 19. an air outlet; 20. a gas-liquid separation device; 21. a plenum chamber; 22. a vertical well; 23. a hydrophobic porous material bin; 24. an inorganic permeable concrete reinforcing agent storage tank; 25. an abrasive buffer tank; 26. a hydraulic pressure booster; 27. an offshore platform; 28. an intelligent control system; 29. gas-liquid flow direction.

The specific implementation mode is as follows:

the following examples are further illustrative of the present invention and are not intended to be limiting thereof.

Unless otherwise specified, the devices and materials mentioned in the present invention are commercially available. SR-inorganic permeable concrete reinforcing agent purchased from Nanjing Jiaoyin