Method and device for exploiting natural gas hydrate in permafrost region

Abstract

The invention discloses a method and a device for exploiting natural gas hydrate in a permafrost region. The device comprises a water-pumping depressurization system, an underground in-situ combustion heating system, a gas collection system and a control system. The water pumping depressurization system comprises a water delivery pipe, a deep-well pump and a gas-liquid separator, wherein the deep-well pump is arranged at the bottom of a vertical well; and the gas-liquid separator is connected with the deep-well pump by the water delivery pipe. The underground in-situ combustion heating system comprises an electronic ignition device and an oxygen-containing gas conveying pipe, wherein the electronic ignition device is connected with a ground power supply by a power switch; and the oxygen-containing gas conveying pipe is connected with an external gas supply system and paved from the ground to the electronic ignition device through the vertical well. The gas collection system comprises a gas collection pipe which is arranged at a well head of the vertical well. The control system comprises a pressure sensor, the power switch and a regulation valve, wherein the regulation valve is arranged on the oxygen-containing gas conveying pipe; and the control system controls the aperture of the regulation valve and the on and off of the power switch according to a pressure, which is measured by the pressure sensor, of the vertical well. By the invention, the synchronous continuous exploitation of depressurization and underground in-situ combustion heating can be realized.

Description

technical field [0001] The invention belongs to the field of energy technology, and relates to natural gas hydrate exploitation technology, in particular to a natural gas hydrate exploitation method and device in permafrost regions. Background technique [0002] Natural Gas Hydrate (NGH for short) is a non-stoichiometric, ice-like, cage-type crystalline compound formed by low-molecular-weight hydrocarbons in water and natural gas under low temperature and high pressure conditions. NGH has the characteristics of a host-guest material. Water molecules (hosts) form a spatial lattice structure through hydrogen bonding, and gas molecules (guests) fill the cavities between the water molecule lattices through van der Waals forces with water molecules. There are extensive natural gas hydrate formation conditions under the seabed and terrestrial permafrost. It is estimated that the organic carbon stored in the form of natural gas hydrate on the earth accounts for 53% of the global to...

AI Technical Summary

Problems solved by technology

The various NGH mining technologies mentioned above have their own advantages and disadvantages and application fields. At present, there is no internationally recognized large-scale NGH mining method that is technically, economically, safe, and environmentally feasible.

[0004] The pressure and temperature of NGH reservoirs in permafrost regions are relatively low, and the amount of free water is small, which is suitable for pumping and depressurization. The decomposition rate of "self-protection effect" is extremely slow. Once the temperature drops below 0°C, it will also cause "ice blockage" and "secondary hydrate" formation, resulting in a significant decrease in the permeability of NGH reservoirs; in addition, if mining is located on the permafrost floor For the above-mentioned NGH, the depressurization method converts all NGH into ice, making the mining impossible; therefore, the depressurization method alone is difficult to be effective in the commercial large-scale mining of NGH in permafrost regions, and a combination of thermal excitation and depressurization method is required. method of mining

Although the conventional hot water injection + depressurization mining method can speed up the mining rate, the hot water is transported from the surface to the NGH layer through the permafrost layer, which will cause heat loss; hot water injection will generate water pressure in the NGH layer, resulting in the decomposition temperature of NGH. The heat loss will also increase accordingly; at the same time, due to the hot water injection, the water production in the mining process will increase, and the pump power consumption and equipment investment will greatly increase in the whole process of hot water preparation, injection, and extraction. More importantly, this method The depressurization and hot water injection can only be carried out in turn, and cannot be carried out synchronously and continuously

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