Gas-water differentiation characteristics of CBM reservoirs in Xiadian block, Qinshui basin

The coalbed methane reservoirs at Xiadian block of Qinshui basin are of low porosity and low permeability. In order to define the gas-water distribution rule in the study area, CBM geological conditions, fracturing and production performance data in the pilot mining district of Xiadian block were analyzed to illuminate the gas-water distribution characteristics and discusses the control factors of gas water distribution differences. The results show that the difference of gas and water in the study area occurs mainly in two cases, one is the difference of the gravity, gas occurs in higher part, water occurs in lower part; the second is that locally affected by the fault, and the gas-water inversion phenomenon occurs, water appears in the higher part and gas appears in the low part. According to the characteristics of gas-water distribution, with structural form as skeleton, combined with reservoir fracturing and production performance data, five patterns of gas and water distribution, were set up, that is, closed fault fold, gas-like cap, open fault control, micro structure control, lithologic control of roof and floor, it was defined that gas and water distribution in this area was mainly affected by structure and fracturing, at the same time differentiated well placement was suggested, which can guide the further exploration and development of CBM.