Geothermal-wind-light synergistic enhanced green coal body development and carbon storage integrated method

Abstract

The invention discloses a terrestrial heat-wind-light synergistic enhanced green coal body development and carbon storage integration method. The method comprises the following steps that S1, a ground heat exchange and gas production combined factory and a wind power or solar heating factory are built; s2, an injection well and an auxiliary heating well are drilled, staged fracturing is conducted on the geothermal reservoir, and a heat taking field is established; s3, drilling an extraction well, performing staged fracturing on the deep coal seam, and establishing a pyrolysis field; s4, a medium is injected into the injection well, the medium enters the deep coal seam in a supercritical state to pyrolyze the coal body under the heating of the geothermal reservoir and the reinforced heating of the auxiliary heating well, and gas obtained after pyrolysis of the coal body is extracted out through the extraction well and then treated; and S5, the step S4 is repeated, after pyrolysis of the pyrolysis field is completed, the auxiliary heating well and the injection well are closed, carbon dioxide is injected into the pyrolysis field through the extraction well, and when adsorption reaches saturation, injection is stopped, and the extraction well is closed. Development of deep coal resources is achieved, and meanwhile energy consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal pyrolysis development, and particularly relates to a method for integrated green development of coal body and carbon storage with synergistic enhancement of geothermal, wind and solar energy. Background Art

[0002] In the global energy consumption structure, although the three major fossil fuels are all important components, the consumption growth of coal remains relatively stable. Coal is not only one of the most important sources of electricity globally, especially in some Asian countries, where the proportion of coal-fired power even exceeds 50%. However, the combustion of coal is also one of the main sources of greenhouse gas emissions such as carbon dioxide, making a significant contribution to global climate change. As the world's largest coal producer and consumer, this requires a fundamental transformation of China's energy supply system. Given that it is difficult to fundamentally change the energy supply structure in the short term, the development and deployment of more efficient clean coal technologies have become a necessary choice.

[0003] In addition, the burial depth of coal seams is an important factor in determining whether they are suitable for direct mining or in-situ underground treatment technologies. Currently, the maximum direct mining depth of coal resources is defined between 900 and 1200 m. However, since most coal resources are buried too deep, it is not economically feasible for direct mining. Therefore, there is an urgent need to develop new technologies to extract and utilize these deep coal resources in a more economical and cleaner way. Summary of the Invention

[0004] The present invention aims to provide a method for integrated green development of coal body and carbon storage with synergistic enhancement of geothermal, wind and solar energy, which reduces energy consumption while realizing the development of deep coal resources.

[0005] For this purpose, the technical solution adopted by the present invention is as follows: A method for integrated green development of coal body and carbon storage with synergistic enhancement of geothermal, wind and solar energy, comprising the following steps:

[0006] Comprising the following steps:

[0007] S1: Mining preparation; first determine the positions of the target deep coal seam and the high-temperature geothermal reservoir, and build a ground heat exchange and gas production combined plant, a wind or solar heating plant according to the positions.

[0008] S2: Establish a heat exchange system; drill a vertical well from the ground heat exchange and gas production combined plant through the formation to reach the geothermal reservoir, construct an injection well, and at the same time drill a vertical well from the wind or solar heating plant through the formation to reach the geothermal reservoir, construct an auxiliary heat well, then horizontally drill the section of the geothermal reservoir between the injection well and the auxiliary heat well through the injection well to make it connected to form a heat exchange connection section, and perform segmented fracturing on the heat exchange connection section to establish a heat extraction field.

[0009] S3: Establish a drainage system. Drill a vertical well from the ground heat exchange and gas production combined plant through the formation to the deep coal seam, construct a drainage well, then horizontally drill through the section between the drainage well and the auxiliary heat well section in the deep coal seam through the drainage well to form a drainage connection section, and perform staged fracturing on the drainage connection section to establish a pyrolysis field;

[0010] S4: Realize pyrolysis drainage. Inject a medium into the injection well. Under the action of the pressure difference, it passes through the heat exchange connection section and the auxiliary heat well in sequence and then reaches the drainage well. Under the heating of the geothermal reservoir in the heat connection section and the enhanced heating of the auxiliary heat well, the medium entering the deep coal seam is in a supercritical state. The coal in the deep coal seam is pyrolyzed by the supercritical medium, and then the gas after the pyrolysis of the coal is extracted through the drainage well and processed to obtain combustible gas;

[0011] S5: Carbon sequestration; Repeat S4. When the amount of combustible gas obtained decreases to a certain amount, close the auxiliary heat well and the injection well, and inject liquid carbon dioxide into the pyrolysis field through the drainage well. The carbon dioxide will be adsorbed by the solid after the pyrolysis of the coal. When the adsorption reaches saturation, stop the injection and close the drainage well.

[0012] As a preference of the above solution, the medium is water or inert gas.

[0013] Further preferably, a pressurized injection device for ensuring that the injected medium is a high-pressure medium and the injected carbon dioxide is liquid and a drainage device for realizing drainage are provided in the ground heat exchange and gas production combined plant.

[0014] Further preferably, an electric heater powered by wind or solar energy heating the plant and used for heating the medium is provided in the auxiliary heat well.

[0015] Further preferably, high-temperature resistant capsules for plugging and sealed with liquid are provided at the junction of the deep coal seam and the overlying rock in the auxiliary heat well, at the junction of the deep coal seam and the overlying rock in the injection well, and at the junction of the deep coal seam and the overlying rock in the drainage well. And each high-temperature resistant capsule is correspondingly equipped with a sealed pipeline capable of realizing the charging and discharging of liquid in the high-temperature resistant capsule, and a circulating pump for facilitating the pressurized entry of liquid is provided on the ground.

[0016] Further preferably, when performing staged fracturing on the drainage connection section, the fracturing fluid used contains components that can promote coal pyrolysis.

[0017] Advantages of the present invention:

[0018] 1) Realize the development of deep coal resources through pyrolysis, and use the adsorption property of the carbon porous medium after pyrolysis to carry out carbon dioxide sequestration, thereby realizing the integration of coal pyrolysis and carbon sequestration, not only realizing the safe mining of coal, but also reducing greenhouse gases.

[0019] 2) The development of deep coal resources is achieved by pyrolysis. Not only does it not require the installation of equipment that can enter the mining area and mining equipment for supporting the mining area, thus saving development costs, but it also reduces the occurrence of mining areas and avoids deformation in the overlying rock area. Moreover, the combustible gas of the energy at the extraction site realizes the green development and utilization of the coal.

[0020] 3) After the extraction is completed, liquid carbon dioxide is injected into the pyrolysis solid product to achieve geological carbon sequestration. This not only improves the stability of the coal seam after pyrolysis but also reduces greenhouse gas emissions. And by using the injection of liquid carbon dioxide tower, which shares the device with the injection medium, it not only avoids the equipment from having a downtime but also effectively reduces costs.

[0021] 4) An injection well connected to the geothermal reservoir is provided, enabling the medium to be preliminarily heated through the geothermal reservoir and then supplemented by the electric energy converted by a wind or solar power plant. This not only ensures that all the energy used in the extraction process is clean energy but also effectively reduces the energy required for the heating medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the present invention.

[0023] Figure 2 It is a schematic diagram of the backpressure valve in the present invention.

[0024] Reference numerals: combined ground heat exchange and gas extraction plant - 1, wind or solar heating plant - 2, injection well - 3, auxiliary heat well - 4, extraction well - 5, upper cavity - 39a, lower cavity - 39b, backpressure washer - 39c, valve core - 39d, taper ring - 39e, diaphragm - 39f, centering washer - 39g, lower washer - 39h, backpressure lower inlet - 39i, backpressure lower outlet - 39j, backpressure upper inlet - 39k, backpressure upper outlet - 39m. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be further described below through embodiments in conjunction with the drawings:

[0026] As Figure 1 shown, a method for integrated geothermal - wind - light synergistic enhanced green development of coal seam and carbon storage includes the following steps:

[0027] The first step is mining preparation. First, determine the positions of the target deep coal seam and the high - temperature geothermal reservoir, and build a combined ground heat exchange and gas extraction plant 1 and a wind or solar heating plant 2 according to these positions. Among them, the ultra - deep high - temperature geothermal reservoir has a geothermal temperature exceeding 100 °C.

[0028] Step 2: Establish a heat exchange system. Drill a vertical well from the ground heat exchange and gas production combined plant through the formation to the geothermal reservoir to construct an injection well 3. At the same time, drill a vertical well from the wind or solar heating plant through the formation to the geothermal reservoir to construct an auxiliary heat well 4. Then, horizontally drill the section between the injection well and the auxiliary heat well in the geothermal reservoir through the injection well to connect them to form a heat exchange connection section, and perform staged fracturing on the heat exchange connection section to establish a heat extraction field.

[0029] Step 3: Establish a gas extraction system. Drill a vertical well from the ground heat exchange and gas production combined plant through the formation to the deep coal seam to construct a gas extraction well 5. Then, horizontally drill the section between the gas extraction well and the auxiliary heat well in the deep coal seam through the gas extraction well to connect them to form a gas extraction connection section, and perform staged fracturing on the gas extraction connection section to establish a pyrolysis field.

[0030] Among them, staged fracturing is an existing technology. When performing staged fracturing on the gas extraction connection section, the fracturing fluid used contains components that can promote coal pyrolysis.

[0031] Step 4: Realize pyrolysis and gas extraction. Inject a medium into the injection well. Under the action of the pressure difference, it passes through the heat exchange connection section and the auxiliary heat well in sequence and then reaches the gas extraction well. Under the heating of the geothermal reservoir in the heat connection section and the enhanced heating of the auxiliary heat well, the medium entering the deep coal seam is in a supercritical state (when the medium is water, its supercritical state: temperature greater than 374 °C, pressure greater than 22.1 MPa). The coal in the deep coal seam is pyrolyzed by the supercritical medium, and then the gas after coal pyrolysis is extracted through the gas extraction well and processed to obtain combustible gas.

[0032] To inject the medium into the injection well, a pressurized injection device for ensuring that the injected medium is a high-pressure medium is provided in the ground heat exchange and gas production combined plant. The pressurized injection device includes a storage container for accommodating the medium, a constant pressure pump, and a pressurized pipeline, and the pressurized pipeline extends into the geothermal reservoir.

[0033] To realize the heating of the auxiliary heat well, an electric heater powered by the wind or solar heating plant and used for heating the medium is provided in the auxiliary heat well, and the electric heater is a dry-burning electric heating tube. Preferably, the electric heater is located between the deep coal seam and the geothermal reservoir, and a temperature sensor and a pressure sensor for detecting the temperature and pressure of the supercritical medium are provided at the deep coal seam in the auxiliary heat well. The temperature sensor is an imported temperature control instrument with PID, and the detected temperature range is: room temperature - 999 °C, and the temperature control accuracy is ±0.5 °C, which is used to ensure that the supercritical medium entering the pyrolysis field can reach the temperature for realizing medium pyrolysis. The temperature sensor and the pressure sensor are used to monitor whether the medium entering the deep coal seam is in a supercritical state. If it is not in a supercritical state, the heating temperature of the electric heater and the pressurizing pressure of the pressurized injection device are adjusted according to the monitored state.

[0034] To prevent the escape of the medium, high-temperature-resistant capsules for sealing and liquid-based sealing are provided at the junction of the deep coal seam and the overlying rock in the auxiliary heat well, injection well, and extraction well. Each high-temperature-resistant capsule is correspondingly equipped with a sealing pipe capable of filling and discharging liquid into the high-temperature-resistant capsule. A circulation pump for facilitating the pressurized entry of liquid is provided on the ground. Preferably, a heat-insulating aerogel is sleeved at the front end of the high-temperature-resistant capsule to prevent heat loss of the supercritical medium.

[0035] To achieve the extraction of the extraction well, an extraction device is provided in the ground heat exchange and gas production combined plant. The extraction device includes a condenser, a back-pressure valve, a gas-liquid separation device, and a gas separation device connected in sequence through an extraction pipe. The extraction pipe extends into the deep coal seam. A back-pressure pump for controlling the pressure of the back-pressure valve is connected in parallel to the back-pressure valve. By adjusting the pressure of the back-pressure valve, extraction is carried out only after pyrolysis reaches a certain degree. The output port for separating the medium in either the gas-liquid separation device or the gas separation device is connected to the storage container of the pressurized injection device to achieve the recycling of the medium.

[0036] As Figure 2 shown, the back-pressure valve includes an upper cavity 39a and a lower cavity 39b arranged vertically. A back-pressure gasket 39c is provided between the upper cavity 39a and the lower cavity 39b. A valve core 39d is provided in the upper cavity 39a. A taper ring 39e is sleeved outside the valve core 39d. A diaphragm 39f located between the upper cavity and the lower cavity is provided at the lower end of the valve core 39d. A downward-facing centering gasket 39g is provided in the lower cavity 39b. A lower gasket 39h is provided between the centering gasket 39g and the diaphragm 39f.

[0037] To control the pressure of the back-pressure valve, a control pressure chamber is provided in the lower cavity 39b. The control pressure chamber is communicated with the diaphragm. At the same time, an exhaust port 39i and a control pressure port 39j communicated with the control pressure chamber are provided on the lower cavity 39b. A certain amount of liquid is injected through the control pressure port to ensure that the diaphragm is subjected to the pressure from the upper side. The control pressure port is connected to the back-pressure pump.

[0038] A backpressure inlet 39k and a backpressure outlet 39m are arranged in the upper cavity 39a, and whether the backpressure inlet 39k and the backpressure outlet 39m are communicated can be realized by the movement of the valve core. The backpressure inlet 39k is connected to the condenser, and the backpressure outlet is communicated with the gas-liquid separation device. As needed, after injecting a certain amount of liquid into the control pressure chamber through the control pressure port 39j, the setting of the opening pressure of the backpressure valve is realized. When the pressure at the backpressure inlet 39k is greater than the set pressure, the valve core will push the diaphragm to move downward into the lower cavity, so that the backpressure inlet and the backpressure outlet are communicated, thereby realizing the passage of the liquid. When the pressure is less than the set pressure, the liquid in the control pressure chamber will pass through the diaphragm and push the valve core to move upward into the upper cavity, thereby disconnecting the backpressure inlet and the backpressure outlet.

[0039] The fifth step is carbon sequestration. Repeat the fourth step. When the amount of combustible gas obtained is reduced to a certain amount, close the auxiliary heat well and the injection well, and inject liquid carbon dioxide into the pyrolysis field through the extraction well. The carbon dioxide will be adsorbed by the solid after the coal body is pyrolyzed. When the adsorption reaches saturation, stop injecting and close the extraction well. Among them, when closing the auxiliary heat well and the injection well, the amount of combustible gas separated needs to be determined according to factors such as economic benefits and the overall extraction time. Usually, when the amount of combustible gas is reduced to about 5% of the peak value, close the auxiliary heat well and the injection well for carbon sequestration.

[0040] To realize the injection of liquid carbon dioxide, lift the pressurized pipeline upward to the deep coal seam, and at the same time connect the pressurized pipeline to the carbon dioxide outlet pipeline of the carbon dioxide capture system.

Claims

1. A method for the integrated development of coal body and carbon storage with collaborative enhancement of geothermal, wind and solar energy, characterized in that, It includes the following steps: S1: Mining preparation; first, determine the positions of the target deep coal seam and the high-temperature geothermal reservoir, and build a combined ground heat exchange and gas extraction plant, a wind or solar heating plant according to these positions; S2: Establish a heat exchange system; vertically drill from the combined ground heat exchange and gas extraction plant through the formation to the geothermal reservoir to build an injection well. At the same time, vertically drill from the wind or solar heating plant through the formation to the geothermal reservoir to build an auxiliary heat well. Then, horizontally drill the section between the injection well and the auxiliary heat well in the geothermal reservoir through the injection well to make them connected to form a heat exchange connection section, and perform staged fracturing on the heat exchange connection section to establish a heat extraction field; S3: Establish a drainage system. Vertically drill from the combined ground heat exchange and gas extraction plant through the formation to the deep coal seam to build a drainage well. Then, horizontally drill the section between the drainage well and the auxiliary heat well in the deep coal seam through the drainage well to make them connected to form a drainage connection section, and perform staged fracturing on the drainage connection section to establish a pyrolysis field; S4: Realize pyrolysis drainage. Inject a medium into the injection well. Under the action of the pressure difference, it passes through the heat exchange connection section and the auxiliary heat well in sequence and then reaches the drainage well. Under the heating of the geothermal reservoir in the heat connection section and the enhanced heating of the auxiliary heat well, the medium entering the deep coal seam is in a supercritical state. The coal body in the deep coal seam is pyrolyzed by the supercritical medium, and then the gas after the pyrolysis of the coal body is extracted through the drainage well and processed to obtain combustible gas; S5: Carbon sequestration; repeat S4. When the amount of combustible gas obtained is reduced to a certain amount, close the auxiliary heat well and the injection well, and inject liquid carbon dioxide into the pyrolysis field through the drainage well. The carbon dioxide will be adsorbed by the solid after the pyrolysis of the coal body. When the adsorption reaches saturation, stop injecting and close the drainage well.

2. The geothermal-wind-solar collaborative enhanced green development method for integrated coal body and carbon storage according to claim 1, characterized in that: The medium is water or an inert gas.

3. The geothermal-wind-solar collaborative enhanced green development method for integrated coal body and carbon storage according to claim 1, wherein: In the combined ground heat exchange and gas extraction plant, there is a pressurized injection device for ensuring that the injected medium is a high-pressure medium and the injected carbon dioxide is in a liquid state, and a drainage device for realizing drainage.

4. The geothermal-wind-solar collaborative enhanced green development method for integrated coal body and carbon storage according to claim 1, wherein: In the auxiliary heat well, there is an electric heater powered by the wind or solar heating plant and used for heating the medium.

5. The geothermal-wind-solar collaborative enhanced green development method for coal body and carbon storage integration according to claim 1, characterized in that: At the junction of the deep coal seam and the overlying rock in the auxiliary heat well, at the junction of the deep coal seam and the overlying rock in the injection well, and at the junction of the deep coal seam and the overlying rock in the drainage well, there are high-temperature resistant capsules for plugging and sealed with liquid, and each high-temperature resistant capsule is correspondingly equipped with a sealed pipeline capable of realizing the charging and discharging of liquid in the high-temperature resistant capsule.

6. The method for the integrated development of geothermal-wind-solar collaborative enhanced green coal body and carbon storage according to claim 1, characterized in that: When performing staged fracturing on the drainage connection section, the fracturing fluid used contains components that can promote the pyrolysis of the coal seam.

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