High Drilling Methane Drainage in Fracturing Zones Formed by Water Injection into Boreholes

Abstract

Methane drainage method should be used before coal mining of many modern collieries because venti lation air methane is in sufficient to keep methane level within regulation values. The technology of high drilling methane drainage (HDMD) has been used for methane drainage although its effect is not very stable due to parameter design. The height of the fracturing zones is determined mostly according to empirical formula, on-site observation and numerical simulation analysis. In this paper, a method was introduced for determining the height of the air f ract uring zones (AFZs) based on its high similarity to the characteristics of Fracturing zones and the relationship between the height of Fracturing zones and the strain of overl ying rock strata. The application of water injection in both Shuangdingshan and Dongrong collieries found that the theoretically calculated the height of the Fracturing zones was approximately equal to the measured one in field tests within a permissible error of less than 5%, proving that the method is feasible. Based on the designed drainage parameters, the u tilization of HDMD technology in the collieries mentioned above found that the methane concentrations in both tail gate and upper corner were controlled in the ranges of 0.17% to 0.32% and 0.26% to 0.84%, respectively. These results showed that the water injection verified HDMD in Fracturing zones could effectively solve the problem of metha ne overrun and also verified the accuracy and reliability of its related theory.