Permeability improvement technology for coal bed gas reservoir cap by using three-dimensional fracture network modification

Abstract

The invention relates to a permeability improvement technology for a coal bed gas reservoir cap by using three-dimensional fracture network modification. The technology is as follows: building a bedding horizontal well from ground to top and bottom plates of the coal bed of an area not mined; building bedding, three-dimensional cross-type or multi-branch long boreholes on the top and bottom plates of the coal bed of the area not mined through perforation and segmented fracturing or existing sinking and driving engineering, and then carrying out hydraulic fracturing; modifying the coal bed gas reservoir cap into a crisscross fracture network system to form a modified volume; building various types of drainage boreholes in the modified volume; and carrying out negative pressure extraction together with a fractured well, so that coal bed gas can be continuously desorbed and dispersed and then extracted out in large scale through the modified volume. According to the invention, the crisscross fracture network system is formed in the coal bed gas reservoir cap, so that the coal bed gas can be continuously desorbed and dispersed at negative pressure and then extracted out in large scale through the modified volume, thus the content of coal bed gas in the modified bed can be quickly reduced to be below the safety standard in the outburst prevention formulation, and safe and high-efficiency production of mines can be realized on the basis of forming scale coal bed gas development.

Description

technical field [0001] The invention relates to the technical field of enhancement and anti-permeability of coalbed methane (gas) reservoir caprock, in particular to a new technology for reconstruction and antireflection of three-dimensional fracture network of coalbed methane (gas) reservoir caprock. Background technique [0002] In recent years, mine mining has developed to the deep, and the mining depth of some mines has exceeded 1000 m. With the increase of mining depth, the gas content of coal seams gradually increases, and the gas pressure of coal seams increases. Some low-gas mines or high-gas mines are gradually upgraded to outburst mines, resulting in frequent gas accidents and has become a bottleneck restricting the improvement of coal mine safety. Therefore, gas control is the primary task of the current coal mine safety work, and this problem needs to be solved urgently. [0003] The twelve-character policy of my country's gas control "pumping first, monitoring ...

AI Technical Summary

Problems solved by technology

However, due to the serious influence of the low permeability characteristics of the coal seam, when the conventional drilling arrangement is used to pre-drain coal seam gas, the required drainage effect is often not achieved; therefore, improving the permeability of the coal seam has become the key to improving the gas drainage effect

For the problem of gas drainage in low-permeability coal seams, the traditional methods only rely on measures such as reducing the drilling distance, increasing the amount of drilling, and prolonging the drainage time to achieve the pre-drainage effect. The tense situation of mining replacement is not in line with the purpose of building intrinsically safe mines. New gas drainage methods are urgently needed to change this dilemma. The original fracture network in the reservoir caprock and a new fracture network are generated to realize the transformation of the three-dimensional fracture network, which increases the gas permeability of the coal reservoir caprock, provides a wider operating space for strengthening gas drainage, and improves the gas drainage effect

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