Method for exploiting natural gas hydrate through U-shaped well microwave heating

Abstract

The invention relates to a method for exploiting a natural gas hydrate through U-shaped well microwave heating and belongs to the technical field of natural gas hydrate exploitation. The method comprises the steps that by combining geologic information, a U-shaped well is arranged for a target reservoir, well-completion practice is matched, after well completion, depressurizing exploitation is conducted through the U-shaped well till the economic benefit is avoided, and after depressurizing exploitation, fracturing operation is conducted on a horizontal well; and then a ground supplying systemand a down-hole microwave heating system are arranged on the horizontal well, through a microwave heater, a natural gas hydrate layer is heated, and natural gas and exploited water are collected froma vertical well. According to the method for exploiting the natural gas hydrate through U-shaped well microwave heating, the U-shaped well is arranged for the target reservoir, the usable natural gashydrate reserve volume is increased, movable heating reserving is achieved by using coiled tubing and the microwave heater, by changing the heating position, the heat output power and the water drainage and gas recovery speed, optimal exploitation of the natural gas hydrate reservoir can be achieved, the gas recovery efficiency can be improved, and the economic benefits can be increased.

Description

technical field [0001] The invention relates to a microwave heating extraction method of a U-shaped well of natural gas hydrate, which belongs to the technical field of extraction of natural gas hydrate, 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,...

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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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