Gas pressure relief method of ground drilling extraction minery and goaf

Abstract

This invention discloses a method for depressuring gas in ground drilled well and mining area. Before extracting coal a ground drilling well is drilled from ground to long distance, low breathing, high gas, projecting and soft covered seams, then extracting down seam. The gas from the up covered seam is exhausted from pipe.

Description

Technical field: [0001] The invention relates to a method for pressure relief, permeability enhancement and flow enhancement of coal body gas. More specifically, it is a pressure-relieving coalbed methane mining method in mining areas aimed at overlying long-distance, low-permeable, high-gas, protruding, soft and thick coal seams. Background technique: [0002] Mine gas is the main reason that restricts production development and causes gas explosions and coal and gas outbursts. To control gas disasters, eliminate coal and gas outbursts, reduce the amount of gas gushing out of mining faces, improve productivity, and realize green co-mining of coal and gas resources The fundamental way is to extract coal gas. [0003] The Huainan Coalfield in Anhui is buried at a depth of more than 2000m, with a total of 50100Mt of preserved and predicted coal reserves. The coalbed methane resource density of the entire coalfield is 142Mm 2 / km 2 Above, up to 405Mm 3 / Km 2 . According ...

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Problems solved by technology

[0010] 1. The Lianghuai coalfield has experienced multiple tectonic movements, and the original structure of some coal seams has been destroyed, forming scaly and powdery structural coal. The damage types of coal are generally three to four types, resulting in a complex fracture-cleat system in the coal seam reservoir. The coal quality is soft, the permeability of the coal seam is low, and the fracturing effect is poor

[0011] 2. Most of the coal seams in the Lianghuai and Huaihe Rivers have low air permeability coefficients and large gas flow attenuation coefficients in boreholes, making them difficult to drain

As a result, the extraction and production of coalbed methane cannot achieve good production capacity

[0012] 3. The in-situ stress in the Lianghuai coalfield is relatively large, and the distribution is uneven. The greater the in-situ stress, the more difficult it is to fracturing the coal seam, and the more unfavorable it is for the fracturing of the coal seam and the extraction of coalbed methane

[0013] 4. The coal seam is soft, causing difficulties in drilling, cementing, completion and fracturing

Increase the solid content and easily pollute the coal seam, so it is very difficult to deal with

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