Author(s)

Ba Quanbin, Liu Yanbao

Corresponding Author

Ba Quanbin

Abstract

A large amount of water and coal slag generally accumulates in the downward drilling of aquifer coal seam, and the effect of gas drainage boreholes is seriously affected. In this paper, the influence of simulated borehole water on coal desorption test and coal stability is analyzed. The test results show that the gas desorption capacity of the coalbed invaded by water accumulated in boreholes decreases by 70% on average, and the strength of coal and rock mass is reduced. The sedimentation, adhesion and cementation of suspended coal and rock particles in the borehole wall results in the sealing of coal cracks, which directly reduces or blocks the gas migration and production channels in the borehole. This paper studies and designs borehole drainage technology and equipment, and achieves the purpose of automatic circulation drainage in parallel with multi-holes. The field test results show that the process equipment can effectively discharge the Water-accumulated coal slag in the borehole. After drainage, the concentration and quantity of single-hole gas extraction are greatly increased, and the purity of single-hole gas extraction is stable at about 0.04m3/min. The problem of water lock effect and coal slag blockage in coal body is effectively solved, and the smooth passage of borehole gas extraction is guaranteed, and the effect of borehole gas extraction is significantly improved.

Keywords

Downward borehole, Gas Desorption, Drainage technology, Porous parallel connection, Extraction effect