Study of the effects of hydraulic fracturing at different dip angles for the development of coalbed methane: a case study in the southeast part of Qinshui Basin, China

Considering the negative relationship between the production of gas and water, we should minimise water production. The dip angle of hydraulic fracturing can control not only the hydraulic connectivity between the roof and floor aquifers and the coal seam, but also the gas flow direction in the coal seam. Permeability test results show that, under the circumstances of natural fractures and cleats fewer impacts, the permeability of coal samples along the direction of the coal seam is obviously higher than that in the direction perpendicular to the coal seam (accounting for 79.2% of the samples). According to the dip angle of hydraulic fracturing, combined with the thickness of coal seam and the development status of natural fractures and cleats, hydraulic fracturing will be divided into three types: vertical dip angle of fracturing, horizontal dip angle of fracturing and inclined dip angle of fracturing. The optimal fracture dip angle: α = arcsin (H/Lmax). [Received: July 6, 2015; Accepted: June 4, 2016]