Row-type horizontal well miscible-phase displacement exploiting method for natural gas hydrate

Abstract

The invention provides a row-type horizontal well miscible-phase displacement exploiting method for natural gas hydrate (NGH), and belongs to the technical field of NGH exploitation. The row-type horizontal well miscible-phase displacement exploiting method comprises the steps that combined with geological data, a row-type horizontal well net is arranged on a target reservoir, and well completingoperation is matched, and after well completion is conducted, depressurizing exploitation is conducted through horizontal wells until no economic benefits are left; , fracturing operation is conductedon the horizontal wells after the depressurizing exploitation, and then a ground supplying system and a downhole injection system are arranged in an injection well; and carbon dioxide and chemical agents are injected into the NGH reservoir in sections through an injection well, and natural gas and produced water are collected from a production well. The row-type horizontal well miscible-phase displacement exploiting method is suitable for the reservoir with low permeability, poor connectivity, thick reservoir and low NGH saturation, and reserves of the available NGH can be enhanced by arranging horizontal wells distributed in a row type in the target reservoir; and the carbon dioxide and chemical agents are injected through the injection well in sections for exploiting so that the gas exploiting efficiency and the ultimate recovery efficiency can be improved, and economic benefits are increased.

Description

technical field [0001] The invention discloses a method for producing natural gas hydrate by miscible flooding in row-type horizontal wells, belonging to the technical field of natural gas hydrate production. 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 as "the super energy of the future". [0003] my country is rich in combustible ice reserves. According to in...

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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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