Method for horizontal well mixed gas displacing coal-bed gas

Abstract

The invention discloses a method for displacing coal seam gas via horizontal well mixed gas, relating to the method of coal seam gas coal mining, which comprises the following steps: 1. A plurality of horizontal wells (10) are formed in the coal seam (30) through the horizontal well craft, which comprise injection wells (11) and harvesting wells (12) alternatively arranged at intervals ; 2. A high-pressure injecting equipment is used to inject the mixed gas into the coal seam (30) with coal seam gas via injection wells (11); 3. The mixed gas with coal seam gas is acquired in harvesting wells (12) until the methane concentration is lower than the coal mining concentration and the preservation concentration. The invention has the advantages of considering both the competitive absorption of strong replacement gas and the effect of permeation increase and methane gas partial pressure of feeble replacement gas; improving the recovery factor and the single yield of the coal seam gas, and reducing the coal mining cost of the coal seam gas, simultaneously, mothballing the waste gas geologically, and reducing and sealing waste gas at a maximum.

Description

technical field [0001] The invention relates to a method for mining coal bed gas, in particular to a method for displacing coal bed gas with mixed gas in a horizontal well. Background technique [0002] Most coal seams in my country have relatively high gas content, with an average gas content of 10m 3 Mining areas above / t account for 41%; but the permeability of coal seams is low, generally 0.002-16.17mD (milli-Darcy). Among them, those with permeability less than 1.0mD account for 72%, which is very unfavorable to the exploitation and utilization of coalbed methane. my country's coal seams generally have low permeability and slow desorption speed, which lead to low production and fast attenuation of most coal seam test wells, and it is difficult to form a stable industrial gas flow. [0003] The current CBM mining methods with relatively mature technology include: surface vertical wells, ground mining area wells (Gobwell), underground horizontal holes (that is, undergro...

AI Technical Summary

Problems solved by technology

As shown in Figure 1, when the recovery well (22) is arranged at four points in the traditional vertical well displacement method, there is a displacement dead zone (40), and this part of the coalbed methane cannot be recovered or fully recovered, which reduces the recovery of the coalbed methane rate; and a large part of the vertical well is in other rock formations (non-coal seams), and a very small part is in coal seams, which takes up a lot of money

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