Method for improving development of coal underground gasification gas cavity by applying double-pinniform horizontal well

Abstract

The invention discloses a method for improving development of a coal underground gasification gas cavity by applying a double-pinniform horizontal well. The method comprises the following steps that S1, a gas inlet hole of a gas injection well is constructed; S2, a horizontal branch well of the gas injection well is constructed; S3, a production well gas production hole is constructed; S4, horizontal branch wells of the production well are constructed; S5, auxiliary holes are constructed; S6, auxiliary devices such as an ignition device, a gasifying agent injection device and a retreating device are put down through a wellhead of the injection well; S7, a gasifying agent is injected into the horizontal branch well points for ignition; S8, after gasification cavities of the two adjacent horizontal branch wells at the finger tip communicate with each other, the auxiliary devices are arranged at the horizontal branch well points of the middle and rear section, and the steps S5-S8 are repeated till coal bed gas cavities of all the horizontal branch wells are integrally gasified and communicated; and S9, an air extractor is installed at the ground end of the production well. The using method can break through the limitation of point or line range injection and production of a vertical well and a horizontal well, a coal seam fracture system is communicated in a large range, the reaction contact area is increased, and the gas production rate is increased.

Description

technical field [0001] The invention relates to the technical field of thermal injection of coal bed gas to increase production, in particular to a method for improving the development of underground coal gasification gas chambers by applying double-pinnate horizontal wells. Background technique [0002] Underground coal gasification is a process in which underground coal is burned in a controlled manner, and combustible gases (CH4, H2, CO) are generated through thermal and chemical effects on coal. The modern underground coal gasification process route is formed on the basis of the Controlled Retreating Injection Point (CRIP) gasification process route, integrating modern drilling technology, advanced petroleum equipment and downhole measurement technology. Compared with the conventional coal mining process, the underground coal gasification process uses the chemical coal mining method to replace the physical coal mining, realizes the underground in-situ transformation of c...

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Problems solved by technology

[0003] Due to the heat insulation and low permeability characteristics of rocks and coal in deep coal seams, it is difficult for the synthetic gas produced by underground coal gasification to flow in the coal seams and rock formations, so that the gas produced and the heat released by coal gasification after ignition are easily limited to one In a small range, it not only affects the formation and development of the gasification chamber, it is difficult to form a far-field effect, but it is also easy to form a local high temperature at the ignition point of the horizontal well, causing damage to the horizontal well and causing production accidents

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