Method for extracting gas from bedding level fractured well of ground coal seam roof

Abstract

The invention provides a method for extracting gas from a bedding level fractured well of a ground coal seam roof, orderly comprising the following steps: selecting a coal storage layer with the gas content more than 8 m<3> / t; determining fissure zone position generated by extracting the coal layer, taking the rock formation at 3-7 m of the middle lower part of the fissure zone as the level construction layer; determining positions of the well opening and kickoff points according to landing points of the level segment; and realizing large curvature radius increased slanting, wherein the drilling position is parallel to a gate road at a coal stope working surface or vertical to the largest principal stress direction, and the length of the level segment is less than or equal to the strike length of the working surface; the well structure adopts a three-part structure; the level segment can be an uncased hole or a lower sleeve tube which is an emission hole; the level segment is constructed in the selected rock layer; the level segment uses an open hole packer or a sleeve tube packer for performing hydraulic fracture in segments; a drainage and extracting apparatus is arranged for extracting the ground gas by a virtual storage layer; and the negative pressure extracting is exchanged between the middle and last phase, thereby realizing multiple functions of the well. The method in the invention improves the extracting efficiency of the ground drilling well, realizes area outburst elimination, and reduces the gas disasters to the maximum limit.

Description

technical field [0001] The invention relates to a method for extracting gas from a bedding horizontal fracturing well on the roof of a ground coal seam. Background technique [0002] The world's coalbed methane (gas) surface development has experienced more than 30 years of history, and a set of systematic process technology has basically been formed. After more than 20 years of arduous exploration, China has realized partial commercial development in Qinshui Basin in Shanxi, Hedong Coalfield, and Fuxin in Liaoning. The hydraulic fracturing completion technology of surface vertical wells supports the entire coalbed methane industry. Although cluster wells and horizontal lateral wells are also actively tested, the harsh geological and construction requirements make it difficult to promote them on a large scale in the near future. However, no matter what kind of well completion technology is used above, the coal reservoir is required to have a primary structure or a fragmente...

AI Technical Summary

Problems solved by technology

However, for the original structure and fragmented coal, the connectivity of the fracture itself is poor, and there is pollution near the wellfield during the drilling process. If no anti-permeability measures are taken, the drainage effect will be limited.

Gas outburst coal seams are often broken coal and mylonitic coal with extremely poor permeability and low strength. Directly extracting gas from it is not only difficult to drill, but also has poor extraction effect. The drilling radius is very small and it is difficult to seal the hole. , making it difficult to stabilize the gas concentration in the long-term

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