A method of hydraulic fracturing gas extraction by drilling through layers

Abstract

Provided is a seam-penetrating drilling hydrofracturing gas extracting method. The method includes that a target drill hole and a hole for penetrating a coal seam are preset as a hydrofracturing free surface; a chambering section of the target drill hole is expanded, and a sleeve is put into the drill hole, fixed and connected with a separating chamber. High-pressure water enters the fracturing drill hole to fracture a coal body, and a fracturing gap is gradually expanded until the gap is communicated with the hole. The water pressure and water amount are increased, and the coal body around the gap is washed. Water flow carries gas and the coal body to pass through the target drill hole to enter the chamber, the gas is extracted, and separation of the gas is achieved. After the coal body is washed, a macro gap communicating the fracturing drill hole and the target drill hole is formed. During extraction, the gas leaks into the gap, flows into the target drill hole and the hydrofracturing drill hole, and a gas flowing mode is changed fundamentally. The gap is equivalent to extension of the length of the target drill hole and the hydrofracturing drill hole in the coal seam, contact area between the gap and the coal body is increased, and a gas extraction effect can be improved.

Description

technical field [0001] The invention relates to a layer-crossing drilling gas drainage method, in particular to a hydraulic fracturing networked layer-crossing drilling method suitable for coal seam gas extraction. Background technique [0002] With the increase of mining depth, the pressure and content of coal seam gas increase, the coal quality is soft, the gas permeability of coal seam is low, it is difficult to extract coal seam gas before mining, and the danger of coal and gas outburst is becoming more and more serious. my country has become the most serious outburst in the world. coal-producing countries. In order to eliminate the outburst risk of coal seams before mining and transform high gas outburst coal seams into low gas coal seams, regional gas drainage methods are required. At present, the regional coal seam gas pre-extraction method widely used in the coal mine field is the pre-extraction of the densely penetrated bed drilling strips in the floor rock roadway ...

AI Technical Summary

Problems solved by technology

[0003] In addition, there are two deficiencies in the pre-extraction of the through-bed drilling: 1) the rock section of the drilled hole is long, the coal seam section is short, and the utilization rate of the drill hole is low; It enters the borehole in the form of seepage, and each borehole extracts the coal body within its own control range, and there is no direct connection between the boreholes, resulting in a large amount of engineering work and low extraction efficiency

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