Method and device for exploiting natural gas hydrate from marine rock

Abstract

An exploiting method and device of marine facies natural gas hydrate. The exploiting method comprises the following steps: (1) after the construction of a vertical well, a fixed pipe is constructed, the exploiting well is set in the center of the fixed pipe, and the mixture is filled between the inner wall of the fixed pipe and the outer wall of the exploiting well; (2) the self-excited oscillating jet nozzle enters the exploiting well along the vertical well to the designated position through an orifice on the exploiting well and sprays the mixture, so that the mixture is broken evenly to form artificial fractures; (3) under the corresponding temperature, the hydrate decomposes to produce gas by depressurized exploiting; (4) the gas-liquid mixture exploited by the exploiting well is separated into liquid and gas in the gas-liquid separation device to collect liquid and gas.

Claims

1. A method of exploiting natural gas hydrate from marine rock, comprising the following steps: positioning a vertical well to contact a hydrate layer, wherein a fixed pipe is connected to the vertical well and positioned in the hydrate layer, wherein an exploiting pipe is positioned in a center of the fixed pipe, and wherein an annulus between an inner wall of the fixed pipe and an outer wall of the exploiting pipe is filled with an adhesive mixture of a hydrophobic porous material and an inorganic permeable concrete reinforcing agent; inserting a self-excited oscillating jet nozzle into an orifice in the exploiting pipe within the fixed pipe to a designated position, the nozzle being configured to spray the mixture to break the mixture and form a plurality of artificial fractures in the mixture; triggering an intelligent control system comprising a temperature rise device and an inhibitor circulation device when a corresponding point of a temperature and pressure measured by a temperature sensor and a pressure sensor is under a level of a natural gas hydrate phase equilibrium, wherein the temperature rise device is configured to heat an outer layer of the fixed pipe and an inhibitor nozzle in the inhibitor circulation device is configured to spray out an inhibitor to inhibit a secondary hydrate formation on the outer layer of the fixed pipe and within the exploiting pipe when the intelligent control system is triggered; collecting a gas rising to an offshore platform, wherein a gas-liquid mixture extracted from the exploiting pipe is separated in a gas-liquid separation device to obtain liquid and gas, wherein a liquid from the gas-liquid mixture is discharged from a discharge port to an upper mud layer and gas from the gas-liquid mixture is discharged from a gas outlet along the vertical well to a gas booster chamber, and wherein when the pressure is higher than a set pressure, the gas rises to the offshore platform to complete gas collection.

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

3. A device for exploiting natural gas hydrate from marine rock comprising a vertical well connected to a fixed pipe buried in a hydrate layer, an exploiting pipe arranged in the center of the fixed pipe, a self-excited oscillating jet nozzle arranged in the exploiting pipe, a temperature rise device, and an inhibitor circulation device arranged outside the fixed pipe, wherein the inhibitor circulation device comprises an inhibitor nozzle arranged outside the exploiting pipe and an inhibitor recovery bin arranged outside the fixed pipe, and the self-excited oscillating jet nozzle is configured to spray a mixture to break the mixture and form a plurality of artificial fractures in the mixture; a gas-liquid separation control system comprises a gas-liquid separation device, a gas booster chamber and an intelligent control system, wherein the intelligent control system is configured to start and stop the temperature rise device and the inhibitor circulation device based on temperature and pressure conditions sensed by a temperature sensor and a pressure sensor arranged outside the fixed pipe, the gas-liquid separation device is configured to separate a gas-liquid mixture extracted from the exploiting pipe to obtain liquid and gas, wherein the liquid is discharged from a discharge port to an upper mud layer and the gas is discharged from a gas outlet along the vertical well to the gas booster chamber, and wherein when the pressure is higher than a set pressure, the gas rises to an offshore platform to complete gas collection.

4. The device for exploiting natural gas hydrate from marine rock according to claim 3, wherein an inner layer filter screen and an outer layer filter screen are arranged outside the exploiting pipe to prevent a plurality of fine particles from entering mixing into the exploiting pipe, and the inner layer filter screen and the outer layer filter screen are both provided with a plurality of orifices for an inflow of the gas-liquid mixture.

5. The device for exploiting natural gas hydrate from marine rock according to claim 4, wherein the temperature rise device is a heating wire, wherein the heating wire arranged on the outer layer of the fixed pipe, and wherein when the corresponding point of the temperature and pressure measured by the temperature sensor and the pressure sensor is less than the level of the natural gas hydrate phase equilibrium, the heating wire is configured to heat the outer layer of the fixed pipe to break the hydrate formed on the outer layer of the fixed pipe.

6. The device for exploiting natural gas hydrate from marine rock according to claim 3, wherein the inner wall of the fixed pipe and the outer wall of the exploiting pipe is filled with the mixture, the mixture comprising hydrophobic porous material and an inorganic permeable concrete reinforcing agent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a structure diagram of an exploiting device of marine facies natural gas hydrate of the present invention, and the dotted line arrow in the diagram is the gas-liquid flow direction;

(2) FIG. 2 is a structural diagram of the longitudinal section of the fixed pipe in FIG. 1;

(3) Meanings of reference signs in the figures:

(4) 1. Boundary of production unit; 2. Sea water layer; 3. Upper mud layer; 4. Hydrate layer; 5. Lower mud layer; 6. Self-excited oscillating jet nozzle; 7. Horizontal exploiting pipe; 8. Fixed pipe; 8-1. fixed pipe outer layer; 8-2. fixed pipe inner layer; 9. Orifice; 10. Hydrophobic porous material; 11. Artificial fractures; 12. Hydraulic jet hose; 13. Inhibitor recovery bin; 14. Inhibitor nozzle; 15 Temperature sensor; 16. Pressure sensor; 17. Temperature rise device; 18. Liquid outlet; 19. Gas outlet; 20. Gas-liquid separation device; 21. Booster chamber; 22. Vertical well; 23. Hydrophobic porous material bin; 24. Inorganic permeable concrete reinforcing agent tank; 25. Abrasive buffer tank; 26. Hydraulic booster; 27. Offshore platform; 28. Intelligent control system; 29. Gas-liquid flow direction.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) The following embodiments are a further description of the present invention, rather than a limitation of it.

(6) Unless otherwise specified, the equipment and materials mentioned in the present invention are all commercially available. SR-inorganic permeable concrete reinforcing agent was purchased from Nanjing Jiajing.

Embodiment 1

(7) As shown in FIG. 1 and FIG. 2, when exploiting a hydrate production area, the boundary of production unit 1 is determined first. The production unit is divided into sea water layer 2, upper mud layer 3, hydrate layer 4 and lower mud layer 5 from top to bottom. The gas-liquid flow direction of hydrate 29 is shown in FIG. 1.

(8) The exploiting device of marine facies natural gas hydrate comprises an artificial sand control well wall system, a hydraulic jet permeability enhancement system, a depressurized exploiting system and a gas-liquid separation control system; an artificial sand control well wall system comprises a fixed pipe 8 buried in a hydrate layer 4, a hydraulic jet permeability enhancement system comprises a water jet hose 12, a self-excited oscillating jet nozzle 6 and jet abrasive stored in an abrasive buffer tank 25; the depressurized exploiting system comprises a vertical well 22, an exploiting pipe arranged in the center of the fixed pipe 8, a temperature rise device arranged outside the fixed pipe 8 and an inhibitor circulation device arranged outside the fixed pipe 8. The mixture of hydrophobic porous material and inorganic permeable concrete reinforcing agent is filled between the inner wall of the fixed pipe and the outer wall of the exploiting pipe. The inhibitor circulation device comprises an inhibitor nozzle 14 arranged outside the exploiting pipe and the inhibitor recovery bin 13 arranged outside the fixed pipe 8, a self-excited oscillating jet nozzle 6 enters the exploiting pipe of the fixed pipe 8 along the vertical well 22 to the designated position and sprays the mixture through the orifice 9 (e.g., port, opening) of the exploiting pipe, so that the mixture can be broken evenly, forming artificial fractures; a gas-liquid separation control system comprises a gas-liquid separation device 20, a gas booster chamber 21 and an intelligent control system 28 which determines the start and stop of the temperature rise device 17 and the inhibitor circulation device according to the conditions of the temperature sensor 15 and the pressure sensor 16 arranged outside the fixed pipe 8.

(9) The exploiting pipe can be set as a vertical exploiting pipe or a horizontal exploiting pipe according to the actual exploiting location. The gas-liquid separation device 20 is a device that can realize the gas-liquid separation of hydrate. In this embodiment, the preferred exploiting pipe is a horizontal exploiting pipe 7. The preferred gas-liquid separation device 20 is a separator with centrifugal force separation and flow separation structure. The gas-liquid mixture extracted from the horizontal exploiting pipe 7 is separated in the separation device 20 to obtain liquid and gas, and the liquid is discharged from the liquid outlet 18 to the upper mud layer 3. The gas is discharged from the gas outlet 19 along the vertical well 22 to the gas booster chamber 21. When the pressure is higher than the set pressure, the gas rises to the offshore platform 27 to complete gas collection. The outer part of the horizontal exploiting pipe 7 is provided with an inner filter screen to prevent the mixing of extremely fine particles into the horizontal exploiting pipe 7 and an outer filter screen to prevent the mixing of large particles into the horizontal exploiting pipe 7. The horizontal exploiting pipe 7 is provided with an orifice 9 for the inflow of gas-liquid mixture. The outer part of the fixed pipe 8 is provided with a fixed pipe outer layer 8-1 and a fixed pipe inner layer 8-2. The fixed pipe outer layer 8-1 of the fixed pipe is evenly arranged with I-beam made from steel, which is to prevent the large particles from mixing into the fixed pipe, and the fixed pipe inner layer 8-2 of the fixed pipe is a filter screen to prevent the extremely fine particles from mixing into the fixed pipe 8. In this embodiment, the temperature rise device 17 is a heating wire, which is uniformly arranged on the outer layer of the fixed pipe 8. When the corresponding point of the temperature and pressure measured by the temperature sensor 15 and the pressure sensor 16 is under the level of the natural gas hydrate phase equilibrium, the heating wire heats the outer layer of the fixed pipe 8 continuously to break the hydrate formed on the outer layer of the fixed pipe 8, ensuring that the gas enters the exploiting pipe 7 from the orifice 9 of the exploiting pipe 7.

(10) The hydrophobic porous material is diatomite, aerogel or foam alloy, and the mass ratio of hydrophobic porous material and inorganic permeable concrete reinforcing agent is 1000:1-10:1. Hydrophobic porous materials have no affinity to water, and gather into blocks in water. Inorganic permeable concrete reinforcing agent reacts with hydrophobic porous materials to form polymer hydrate which is not easy to be dispersed by water, which greatly improves the compressive strength and adhesive strength of hydrate, and enhances the freeze-thaw resistance, durability and weather resistance of hydrophobic porous materials.

(11) The fixed pipe 8 is buried in the hydrate layer 4 in advance, and the horizontal exploiting pipe 7 is set in the fixed pipe 8. The hydrophobic porous material 10 from the hydrophobic porous material bin 23 is mixed with the inorganic permeable concrete reinforcing agent from the inorganic permeable concrete reinforcing tank 24, the mixture is acted by the hydraulic booster 26, and then enters and fills between the outer wall of the horizontal exploiting pipe 7 and the inner wall of the fixed pipe 8 through the vertical well 22. The hydrophobic porous material 10 is adhesive formed under the action of inorganic permeable concrete reinforcing agent; the abrasive of the abrasive buffer tank 25 is sprayed under a high pressure through the self-excited oscillating jet nozzle 6 under the action of constant pressure and constant speed pump on the adhesive formed hydrophobic porous material in the fixed pipe 8, and the self-excited oscillating jet nozzle 6 is connected with the hydraulic jet hose 12 to realize the directional moves of the self-excited oscillating jet nozzle 6 in the fixed pipe 8 and the horizontal exploiting pipe 7 to the designated position to spray the hydrophobic porous material 10 according to the demand, so that the hydrophobic porous material 10 which is adhesive formed with the inorganic permeable concrete reinforcing agent can be broken evenly to form artificial fractures 11; the start and stop of the inhibitor nozzle 14 of the inhibitor circulation device can be controlled by the intelligent control system 28, when the inhibitor nozzle 14 is started, the inhibitor is sprayed out to the wellhead of the exploiting pipe to inhibit the secondary hydrate formation at the bottom of the well. When inhibitor nozzle 14 is stopped, the redundant inhibitor flows to inhibitor recovery bin 13.

(12) The method of exploiting natural gas hydrate from marine rock comprises the following steps:

(13) (1) when exploiting a hydrate production area, the construction of a vertical well is completed first by drilling technology, and then the horizontal fixed pipe is constructed after reaching the middle of the hydrate layer. The diameter of the horizontal fixed pipe is determined according to the seepage conditions of the hydrate layer. The constructed fixed pipe is filled with a mixture of hydrophobic porous material and inorganic permeable concrete reinforcing agent, the mass ratio of hydrophobic porous material and inorganic permeable concrete reinforcing agent in the mixture of hydrophobic porous material and inorganic permeable concrete reinforcing agent is 1000:1-10:1. They are evenly mixed to fill the inner wall of the fixed pipe and the outer wall of the horizontal exploiting pipe and adhesive formed. The purpose of this step is to use the pores of hydrophobic porous material to discharge the gas and liquid produced by decomposing to block the sea mud outside the fixed pipe; the horizontal exploiting pipe is arranged in the middle of the hydrophobic porous material inside the fixed pipe, the horizontal exploiting pipe is divided into two layers: an inner layer and an outer layer. Both of them are equipped with fine mesh and orifices. The fine mesh prevents the very fine particles from mixing into the horizontal exploiting pipe. The orifice is used for the inflow of gas and liquid into the artificial sand control well wall;

(14) (2) Artificial sand control well wall with hydraulic jet permeability enhancement: the self-excited oscillating jet nozzle enters the exploiting pipe with a fixed pipe along the vertical well to the designated position through the orifice on the exploiting pipe and sprays the mixture, so as to break the glued mixture evenly and form artificial fractures. The artificial fractures are to improve the permeability around the exploiting pipe and improve gas production efficiency.

(15) (3) Depressurized exploiting: under the corresponding temperature, when the exploiting pressure is lower than the natural gas hydrate phase equilibrium pressure, the hydrate decomposes to produce gas. As the temperature around the hydrate is decreased due to the decomposition process, the natural gas hydrate phase equilibrium pressure is also decreased, which leads to the secondary hydrate easily appearing in the exploiting pipe and on the fixed pipe wall, resulting in the blockage of the pipe body. An intelligent control system judges the start and stop of a temperature rise device and an inhibitor circulation device according to the conditions of a temperature sensor and a pressure sensor. When the corresponding point of the temperature and pressure measured by the temperature sensor and the pressure sensor is under the level of the natural gas hydrate phase equilibrium, the temperature rise device and inhibitor circulation device start automatically. The temperature rise device heats the outer layer of the fixed pipe continuously. The inhibitor nozzle in the inhibitor circulation device sprays out the inhibitor to the wellhead of the exploiting pipe to inhibit the secondary hydrate formation on the outer layer of the fixed pipe and at the bottom of the well;

(16) (4) Gas liquid separation: the gas-liquid mixture extracted from the horizontal exploiting pipe is separated in the gas-liquid separation device to obtain liquid and gas. The liquid is discharged from the discharge port to the upper mud layer and the gas is discharged from the gas outlet along the vertical well to the gas booster chamber. When the pressure is higher than the set pressure, the gas rises to an offshore platform to complete gas collection.

Embodiment 2

(17) According to the exploiting method and device of marine facies natural gas hydrate in the Embodiment 1, the hydrate reservoir is exploited. The hydrophobic porous material is diatomite, aerogel or foam alloy, and the mass ratio of hydrophobic porous material and inorganic permeable concrete reinforcing agent is 1000:1-10:1. In this embodiment, the hydrophobic porous material is diatomite, and the inorganic permeable concrete reinforcing agent is SR-inorganic permeable concrete reinforcing agent. The mass ratio of hydrophobic porous material and inorganic permeable concrete reinforcing agent is 100:1, and the exploiting pressure is 3 MPa. After the gas-liquid mixture generated by hydrate separation enters the horizontal well, the gas is discharged from the outlet along the vertical well to the gas booster chamber. When the pressure is higher than the set pressure, the gas is exploited from the vertical well to complete gas collection. The natural gas concentration obtained by the exploiting method of this embodiment is high, the gas production rate is more than 4 times of the gas production rate of the prior art (the artificial sand control well wall of the Embodiment 1 was not used).

(18) The above is a detailed introduction given to the exploiting method and device of marine facies natural gas hydrate provided by the present invention. The above description of the embodiments is only used to help understand the technical scheme and the core idea of the present invention. It should be pointed out that for those skilled in the art, the present invention can be improved and modified without departing from the principle of the invention, these improvements and modifications also fall into the protection scope of the claims of the present invention.