CN107130944B - A method of employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation - Google Patents

Abstract

The invention discloses a method for exploiting natural gas hydrate reservoirs by using geothermal energy in a fluid circulation mode. The main method is to drill a thermal well to penetrate the seabed hydrate layer and its lower geothermal layer, and inject fluid to return to the hydrate reservoir area after heat exchange. Geothermal energy is used to promote the decomposition of hydrate, and the decomposed natural gas is produced by the horizontal perforation section of the upper production well under the action of gravity. The specific method is: drill a concentric tubular thermal well on the sea surface to penetrate the hydrate layer and its lower geothermal layer, inject cold fluid into the oil pipe at the wellhead, and the fluid will be heated by the geothermal layer after entering the casing at the bottom of the well, and the heated fluid will return to the hydrate layer. The formation provides energy for hydrate decomposition, which is used to assist production wells in depressurization production. The invention adopts the combination method of depressurization and heating, has simple equipment, convenient operation and strong economy, and provides guidance for large-scale exploitation of hydrate deposits.

Description

A method of utilizing geothermal energy to exploit natural gas hydrate reservoirs by means of fluid circulation method

technical field

The invention relates to a method for exploiting seabed natural gas hydrate, in particular to a method for establishing a thermal well and utilizing geothermal energy in fluid circulation to exploit natural gas hydrate reservoirs.

Background technique

With the development of economy and technology, the world's demand for energy is increasing day by day, especially for oil and natural gas. However, conventional oil and gas resources are non-renewable resources. With the continuous reduction of conventional oil and gas resources, unconventional oil and gas resources are beginning to be affected widespread attention around the world. Gas hydrate, also known as combustible ice, is an ice-like solid crystal composed of natural gas and water molecules distributed in seabed sediments or land permafrost. The combustion of natural gas hydrate only produces carbon dioxide and water, and will not pollute the environment. It is a new type of green energy.

At present, the mining methods of marine natural gas hydrate mainly include thermal stimulation mining method, depressurization mining method, chemical agent injection mining method and solid mining method. However, all of the above mining technologies have their own limitations, such as the thermal stimulation mining method has large heat loss and low heat utilization efficiency; the depressurization mining method is only economically feasible when the natural gas hydrate reservoir is located near the temperature-pressure equilibrium boundary nature; the chemical agent injection mining method has a slow effect on the gas hydrate formation, and the cost is very high.

Studies have shown that my country's South China Sea seabed natural gas hydrate and geothermal resources are very rich. If the geothermal resources can be used effectively, environmental pollution can be avoided and the requirements of sustainable development can be met. methods, which largely restrict the efficient development of gas hydrate reservoirs. The invention proposes to establish a thermal well to develop geothermal energy, and transfer the thermal energy to the hydrate layer to promote the decomposition of hydrate and realize the purpose of utilizing geothermal energy to develop natural gas hydrate reservoirs. The equipment is simple, easy to operate, and economical, and can be used as Provide guidance for large-scale exploitation of hydrate reservoirs.

Contents of the invention

The invention relates to a method for exploiting natural gas hydrate reservoirs by using geothermal energy in a fluid circulation mode, which mainly includes the following steps:

(1) According to the geological structure environment of the block, the block containing hydrate reservoirs on the seabed and the geothermal layer under the hydrate layer is selected as the measure area, and the temperature of the geothermal layer is above 120°C;

(2) Drill two wells to form a thermal well and a production well group. The thermal well consists of four parts, including two vertical well sections and two horizontal well sections. Different well sections use different positions of insulation layers to obtain higher heat transfer efficiency, the specific drilling steps are: drill the vertical well section (1) to the distance from the top of the hydrate layer position, build up a horizontal well section (2) with a length of 500-1500m, and then drill a vertical well section (3) to the middle of the geothermal layer and the top position, the horizontal well section (4) with a build-up length of more than 1000m, the thermal well does not perforate, and there is no fluid exchange with the formation. position and parallel to and above the thermal well horizontal well section (2);

(3) The production well is decompressed and developed, the fluid injection rate of the thermal well is controlled to be 50-150m ³ /d, and the development method of tubing injection into the casing is adopted, and cold fluid is injected into the tubing at the wellhead. After reaching the bottom of the well, it enters the annular space between the tubing and the casing and exchanges heat with the geothermal layer. When the heating fluid returns to the hydrate layer through the casing, the energy it carries will be transferred to the hydrate, and the hydrate will be decomposed by heat. , the natural gas produced by decomposition is produced through the horizontal perforation section of the upper production well;

(4) Continuously monitor the gas production rate of the production well. When the gas production rate is lower than 1000-2000m ³ /d, the injection of the thermal well is stopped, and the production of the production well is stopped.

The beneficial effects of the present invention are:

It utilizes the deep geothermal energy to mine natural gas hydrate, which can greatly reduce the cost of heat injection during the mining process and greatly increase the recovery rate. The invention has simple equipment and convenient operation, and can open up a new approach for hydrate exploitation.

Description of drawings

Figure 1 is a schematic diagram of the development of hydrate reservoirs by well groups of thermal wells and production wells.

Fig. 2 is a schematic diagram of the wellbore structure of the vertical section (1) of the thermal well.

Fig. 3 is a schematic diagram of the wellbore structure of the horizontal section (2) of the thermal well.

Fig. 4 is a schematic diagram of the wellbore structure of the vertical section (3) of the thermal well.

Fig. 5 is a schematic diagram of the wellbore structure of the horizontal section (4) of the thermal well.

In the figure: 1. Vertical Well Section of Thermal Well (1); 2. Horizontal Well Section of Thermal Well (2); 3. Vertical Well Section of Thermal Well (3); 4. Horizontal Well Section of Thermal Well (4); 5. Natural Gas Hydrate reservoir; 6. Geothermal layer; 7. Thermal well; 8. Production well; 9. Insulation layer; 10. Sealing the bottom of the well.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings, but the implementation scope of the present invention is not limited.

According to the geological structure environment of the block, the block containing hydrate reservoirs on the seabed and the geothermal layer under the hydrate layer is selected as the measure area, and the temperature of the geothermal layer is 150°C;

As shown in Figure 1, two wells are drilled in the measure area to form a thermal well 7 and a production well 8 well group, in which the thermal well 7 consists of four parts, including two vertical well sections and two horizontal well sections, and different well sections are used Heat insulation layer 9 at different positions to obtain higher heat exchange efficiency. The specific drilling steps are: drill the vertical well section (1) to the top of the hydrate layer 5 position, build up a horizontal well section (2) with a length of 1000m, and then drill a vertical well section (3) to the middle of the geothermal layer 6 and the distance from the top position, a horizontal well section (4) with a length of 1,000 m is generated by deflection, the thermal well 6 does not perforate, and there is no fluid exchange with the formation, and the horizontal perforated section of the production well 8 is located at the upper part of the hydrate layer position and parallel to the thermal well 7 horizontal section (2);

As shown in Fig. 1, the production well 8 is under decompression production, the fluid injection rate of the thermal well 7 is controlled to be 70m ³ /d, and the development method of tubing injection and casing production is adopted, and cold fluid is injected into the tubing at the wellhead, and the fluid reaches After the bottom of the well, it enters the annular space between the tubing and the casing and exchanges heat with the geothermal layer 6. When the heating fluid returns to the hydrate layer 5 through the casing, the energy it carries will be transferred to the hydrate, and the hydrate will decompose under the action of gravity. Next, the natural gas produced by decomposition is produced through the horizontal perforation section of the upper production well 8;

The gas production rate of the production well 8 is continuously monitored, and when the gas production rate is lower than 1000m ³ /d, the injection of the thermal well is stopped, and the production of the production well is stopped.

The parts not mentioned in detail above are the common knowledge of those of ordinary skill in the art. The present invention is not limited to the above-mentioned preferred embodiment. The same or similar technical solutions all fall within the protection scope of the present invention.

Claims (9)

1. a kind of method for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation, it is same to beat a bite on sea Heart cast heating power well runs through hydrate layer and its underpart geothermal layer, and cold fluid is injected in well mouth oil pipe, and fluid enters in shaft bottom Heated after casing by geothermal layer, heating fluid returns to hydrate layer and for decomposition of hydrate provides energy, to assist producing well into Row decompression exploitation, to greatly improve recovery ratio, it is characterised in that comprise the following steps that:

Step (1): according to block geological tectonic environment, selecting seabed to contain hydrate hiding and hydrate layer lower part, there are geothermal layers Block as measure region；

Step (2): making a call to two mouthfuls of well constructions, one heating power well and producing well well group, wherein the horizontal perforated interval of the producing well is located at water Nitride layer is closed apart from topAt position, wherein the heating power well is drilled into hydrate layer apart from topAt position, deflecting is raw At the net horizontal section for having certain length, lower part geothermal layer is then drilled into apart from topAt position, deflecting generation has a fixed length The net horizontal section of degree, the heating power well not perforation, therefore fluid communication is not present with stratum；

Step (3): the producing well carries out decompression exploitation, injects cold fluid in the well mouth oil pipe of the heating power well, fluid arrives Heat exchange occurs into the annular space between oil pipe and casing after up to shaft bottom and with geothermal layer, heating fluid is returned through casing and is hydrated By the energy transmission of carrying to hydrate when nitride layer, hydrate is thermally decomposed, and under gravity, decomposes the natural gas of generation Through the horizontal perforated interval extraction of producing well described in top；

Step (4): continuing to monitor the production gas velocity degree of producing well, is lower than 1000~2000m when producing gas velocity degree³Heating power well stops when/d Injection, producing well stop exploitation.

2. a kind of side for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation as described in claim 1 Method, which is characterized in that it is heating secondary buck exploitation that hydrate, which hides mining method, and energy needed for decomposition of hydrate is by geothermal layer It provides.

3. a kind of side for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation as described in claim 1 Method, which is characterized in that the heating power well is made of four parts, including two vertical well sections, two net horizontal sections, is specifically connected to Sea well section (1) vertical with hydrate layer, positioned at hydrate layer lower part net horizontal section (2), be connected to hydrate layer and underground heat The vertical well section (3) of layer and the net horizontal section (4) in the middle part of geothermal layer.

4. a kind of side for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation as described in claim 1 Method, which is characterized in that the geothermal layer temperature is at 120 DEG C or more.

5. a kind of side for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation as claimed in claim 3 Method, which is characterized in that the length of the net horizontal section (2) positioned at hydrate layer lower part is 500~1500m, described to be located at ground The length of net horizontal section (4) in the middle part of thermosphere is in 1000m or more.

6. a kind of side for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation as claimed in claim 3 Method, which is characterized in that the net horizontal section (4) positioned at the net horizontal section (2) of hydrate layer lower part and in the middle part of geothermal layer Oil pipe outside plus one layer of heat insulation layer with reduce oily tube fluid and cover tube fluid heat exchange；Oil in vertical well section (3) Pipe is outer and casing adds one layer of heat insulation layer outside to reduce the loss of heat in the heating power well conveying heating flow liquid process.

7. a kind of side for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation as claimed in claim 6 Method, which is characterized in that the material of the heat insulation layer is polyethylene.

8. a kind of side for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation as claimed in claim 3 Method, which is characterized in that the horizontal perforated interval of producing well should with it is described be located at net horizontal section (2) of hydrate layer lower part it is parallel simultaneously It is positioned above.

9. a kind of side for employing geothermal energy exploitation of gas hydrate hiding in the way of fluid circulation as described in claim 1 Method, which is characterized in that the fluid injection rate of the heating power well is 50~150m³/d。