Method for extracting natural gas hydrate in hot-water injection mode through parallel horizontal wells

Abstract

The invention discloses a method for extracting natural gas hydrate in a hot-water injection mode through parallel horizontal wells, and belongs to the technical field of natural gas hydrate extraction. The method includes the steps that in combination with geological data, arrangement of a parallel horizontal well network and matched well completion operation are conducted for a target reservoir;after well completion, depressurization extraction is conducted through the horizontal wells until no economic benefit can be gained; then, a ground supply system and an underground mobile electric heating system are arranged on the water injection well, hot water is injected into the natural gas hydrate reservoir through the water injection well, and natural gas and extracted water are collectedfrom the production well. According to the method, the reserve of available natural gas hydrate is increased by arranging the parallel horizontal wells for the target reservoir, the reservoir is heated in a mobile mode by using the mobile electric heating system, optimized extraction of the natural gas hydrate reservoir is achieved by changing the heating position, the heat output power and the drainage gas extraction speed, the gas extraction efficiency can be improved, and the economic benefit can be increased.

Description

technical field [0001] A method for exploiting natural gas hydrate by injecting hot water into parallel horizontal wells belongs to the technical field of natural gas hydrate exploitation, and in particular relates to a method for exploiting natural gas hydrate by comprehensively utilizing a heating method and a depressurization method. Background technique [0002] Natural gas hydrate (NGH for short) is a non-stoichiometric clathrate compound formed by natural gas and water at a certain low temperature and high pressure, also known as "combustible ice". 1m 3 Natural gas hydrate can contain 164m 3 methane gas and 0.8m 3 of water. "Combustible ice" is a secondary product of natural gas, and its application range is roughly the same as that of natural gas. It is a typical oil substitute. "Combustible ice" is extremely flammable. Under the same conditions, the energy generated by the combustion of "combustible ice" is dozens of times higher than that of coal, oil, and natur...

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Problems solved by technology

However, the decomposition driving force provided by the depressurization method alone is small, and the decomposition of natural gas hydrate causes the temperature to drop. When the temperature drops below 0°C, it will also cause ice blockage and stagnation of natural gas hydrate decomposition. CN 20111048906.4 discloses a drainage The natural gas hydrate is exploited by depressurization and heating at the same time, which continuously promotes the decomposition of hydrate. The above two methods use the gas escaping after the hydrate is decomposed, and the water falls due to its own weight. The water pump discharges the water out of the natural gas hydrate production well. But in fact, the decomposed gas carries a large amount of water vapor when it escapes, and the escape speed is very slow, and the extraction efficiency is very low

Moreover, in CN 20111048906.4, horizontal wells are used for combustion and heating. It is unsafe to burn and heat in natural gas hydrate exploitation wells. There are combustible gases inside and outside the natural gas hydrate exploitation wells. It is very dangerous to use open flames for direct heating.

In CN 201310398998.0, microwave generators are used to heat and exploit natural gas hydrates, and the decomposition of natural gas hydrates is promoted by heating. However, the use of vertical wells limits the heated volume of heated natural gas hydrates, and it is more convenient to fix the microwave generators on the upper part of the packer. Further limit the heating volume of gas hydrate

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