A gas hydrate recovery method based on gas-water balance

Abstract

The invention discloses a natural gas hydrate exploitation method based on gas-water balance, belonging to the technical field of natural gas hydrate exploitation. According to the method, gas is usedfor maintaining the pressure in a production well instead of liquid pressure used for the conventional depressurizing production. The method comprises the steps of drilling to the underlaying bed ofa hydrate, and tripping in a casing pipe and a production well pipe. By controlling the gas pressure and the liquid pressure, a liquid level difference is formed between the inside and outside the production well pipe, so that the gas-water balance is realized; furthermore, the natural gas hydrate reservoir section is enabled to be free of liquid, so that the water and the gas, which decomposed from the hydrate, are facilitated to enter the production well. The natural gas hydrate exploitation method can reduce the water saturation degree of the near-well reservoir, improves the relative gas permeability of the near-well reservoir, and slows down the formation of the secondary hydrate in the near-well reservoir, thus finally realizing the safe and efficient exploitation of the natural gashydrate.

Description

technical field [0001] The invention belongs to the technical field of natural gas hydrate exploitation, and in particular relates to a natural gas hydrate exploitation method based on gas-water balance. Background technique [0002] Natural gas hydrate refers to a cage-shaped crystal substance formed by natural gas and water at a specific temperature and pressure. It looks like ice and snow. Because it can be ignited, it is commonly called "combustible ice". Natural gas hydrate has the characteristics of high energy density, wide distribution, large reserves and shallow burial, and is considered to be an ideal alternative energy source in the 21st century. It is preliminarily predicted that the natural gas hydrate resources in my country's sea area are about 80 billion tons of oil equivalent. [0003] In 2017, my country successfully realized the safe and controllable exploitation of natural gas hydrates in muddy silt sands in sea areas by adopting the depressurization met...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a gas-based gas hydrate solution based on low gas phase relative permeability and low intrinsic permeability caused by high water saturation in the near-well reservoir during depressurization of natural gas hydrate, which will lead to low gas production rate and low gas production efficiency. Water-balanced natural gas hydrate production method, by using high-pressure gas to maintain the production bottom hole pressure to reduce near-well reservoir water saturation

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