Offshore natural gas hydrate row-type horizontal well mining method

Abstract

The invention discloses an offshore natural gas hydrate row-type horizontal well mining method and belongs to the technical field of natural gas hydrate mining. The method includes the steps that in combination with geological data, a row-type 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 horizontal wells till no economic benefit exists; after depressurizing mining is finished, fracturing operation is performed on the horizontal wells; then a ground supplysystem and an underground water injection system are arranged at the water injection wells; and displacement water is injected into the natural gas hydrate reservoir through the water injection wells, and natural gas and formation water are collected from the producing wells. The offshore natural gas hydrate row-type horizontal well 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 developed by injecting surface seawater and additives, the surface seawater has certain temperature,natural gas hydrate decomposing can be promoted, then the optimal mining of the natural gas hydrate reservoir is achieved, the gas mining efficiency is improved, the cost is low, and the economic benefits can be improved.

Description

technical field [0001] A method for exploiting offshore natural gas hydrate row-type 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 gas. It is known...

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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.

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