Investigation of the factors causing the coalbed methane production differences in Shizhuangnan Block, Southern Qinshui Basin, North China

Abstract

The geology and engineering characteristics are investigated in the Zaoyuan area of the Shizhuangnan Block, Southern Qinshui Basin to determine variations in the water/gas production not only amongst regions, but wells within the same region. Using geophysical logging, hydraulic fracturing and production data, it appears that a roof/floor with low shale content may be the cause of excessive water production when a coal reservoir predominantly develops horizontal fractures due to hydraulic fracturing. Maintaining a slowly bottom hole pressure decline rate before gas production and stable after producing gas is favourable for the extension of the pressure drop funnel. This is also more likely to help wells have high gas production over their lifetime. Whether or not a coal reservoir depressurises fully is crucial for gas production in both north and south regions. [Received: October 19, 2017; Accepted: July 5, 2018]