A reverse mining method and mining equipment for a seabed natural gas hydrate stable layer

Abstract

The invention relates to a reverse production method for a seafloor gas hydrate stable layer. The reverse production method comprises the following steps of S1, pressure-drop gas production: firstly, sucking out liquid in a production well, dropping the pressure at the bottom of the well, producing free gas under the hydrate stable layer, and decomposing the lower surface of the hydrate stable layer; S2, heat-injection decomposing: injecting hot water or steam into the upper part of a production layer, decomposing the gas hydrate stable layer from bottom to top, and producing from the production well after decomposing; S3, cementing of carbon dioxide: injecting the carbon dioxide into the lower part of the production layer, and gradually cementing at the bottom part of the production layer from bottom to top; S4, after the cementing is completed, repeating the steps S1, S2 and S3, cycling to produce, and stopping production until the natural gas hydrate stable layer is thinned to the proper thickness. The reverse production method has the advantage that the problems of easy leakage of natural gas, easy pollution to sea environment, and easy occurrence of geological disasters in the production process of seafloor natural gas hydrates are solved.

Description

technical field [0001] The invention relates to the technical field of natural gas hydrate exploitation, in particular to a reverse exploitation method and exploitation equipment of a seabed natural gas hydrate stable layer. Background technique [0002] Natural gas hydrates (Natural Gas Hydrates, NGH) are composed of light hydrocarbons, CO 2 and H 2 It is a white solid crystalline substance formed during the interaction between small molecule gases such as S and water, which can burn when exposed to fire, also known as combustible ice. 1 cubic meter of natural gas hydrate can be converted into 164 cubic meters of natural gas and 0.8 cubic meters of water. It is an extremely efficient and clean energy source with much less pollution than coal and oil. [0003] There are four main types of conventional mining methods for hydrates: depressurization method, heat injection method, chemical reagent injection method and carbon dioxide replacement method. The depressurization m...

AI Technical Summary

Problems solved by technology

The problem of carbon dioxide replacement method is that the replacement process lasts for a long time, the replacement efficiency is low, the effect is not obvious, and it is not suitable for the exploitation of seabed gas hydrate stable layers without closed cap rocks

To sum up, if conventional methods are used to directly exploit this stable layer of marine gas hydrate along the bedding, it will easily lead to uncontrolled decomposition of gas hydrate reservoirs without sealed cap rocks, releasing a large amount of natural gas and causing environmental pollution.

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