Natural gas hydrate water discharge gas production exploitation device and exploitation method of natural gas hydrate water discharge gas production exploitation device

Abstract

The invention provides a natural gas hydrate water discharge gas production exploitation device and an exploitation method of the natural gas hydrate water discharge gas production exploitation device, and belongs to the technical field of natural gas hydrate exploitation. A feeding cavity (12) communicated with a natural gas hydrate layer (29) is connected with an in-well gas-liquid separator (7), an exhaust cavity (8) of the in-well gas-liquid separator (7) is communicated with a gas production sleeve pipe (17), and a water discharge opening of the in-well gas-liquid separator (7) is communicated with a liquid storage cavity (2) arranged at the lower part. According to the exploitation method adopting the device, the natural gas hydrate layer (29) is firstly heated, the in-well gas-liquid separator (7) is utilized for separating gas-water mixture generated in the natural gas hydrate decomposition process, meanwhile, a liquid level monitoring device is utilized for regulating the water discharge speed of an electric submersible pump (4), and the decomposition speed of the natural gas hydrate is controlled. The device and the method have the advantages that the natural gas hydrate exploitation well liquid accumulation can be effectively prevented, the gas production efficiency is improved, the work is safe and reliable, the environment is protected, the service life is long, and the like.

Description

technical field [0001] The natural gas hydrate drainage and gas recovery exploitation device and its exploitation method belong to the technical field of natural gas hydrate exploitation, and specifically relate to a natural gas hydrate exploitation device and a exploitation method using the apparatus by comprehensively utilizing a heating method and a drainage and 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 do...

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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 upwards, and the upward escape speed is very slow, and the extraction efficiency is very low. Moreover, it was found in the experiment that the water vapor in the decomposed gas condenses into water or condensate before reaching the ground and stays in the natural gas hydrate exploitation. In the well, a liquid column is easily formed in the gas production casing, and it is easy to cause additional hydrostatic back pressure on the gas reservoir. At this time, the water pump only pumps the water in the liquid storage chamber at the bottom of the natural gas hydrate production well, and cannot pump out the water in the gas production casing. Water column, the accumulated liquid column will eventually kill the gas pressure, causing liquid accumulation in gas hydrate production wells, resulting in shutdown of gas hydrate production wells

Moreover, in CN 20111048906.4, horizontal wells are used for combustion and heating. Firstly, the cost of drilling horizontal wells is very high, and it is definitely not enough to gradually deepen a horizontal well with the exploitation. Secondly, combustion and heating in natural gas hydrate production wells is not safe. There are flammable gases inside and outside the well, and it is very dangerous to heat directly with an open flame

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