Natural gas hydrate parallel horizontal well hot-water-injection mining method

Abstract

The invention discloses a natural gas hydrate parallel horizontal well hot-water-injection mining method and belongs to the technical field of natural gas hydrate mining. The method includes the stepsthat in combination with geological data, a parallel horizontal well network is arranged for a target reservoir; matched well-completion operation is performed; after well completion is finished, depressurizing mining is performed through the horizontal wells till no economic benefit exists; after depressurizing mining is finished, fracturing operation is performed on the horizontal wells; then aground supply system and an underground movable electric heating system are arranged at the water injection wells; and hot water is injected into the natural gas hydrate reservoir through the water injection wells, and natural gas and produced water are collected from the producing wells. The natural gas hydrate parallel horizontal well hot-water-injection mining method is suitable for the reservoir which is poor in communication property, rich in storage and low in natural gas hydrate saturability; the reservoir is movably heated through the underground movable electric heating system; and by changing the heating position, heat output power and drainage gas recovery speed, optimal mining of the natural gas hydrate reservoir is achieved, the gas mining efficiency can be improved, and theeconomic benefits are improved.

Description

technical field [0001] A method for exploiting natural gas hydrate by hot water injection in 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 natural...

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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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