Accumulation conditions of shale gas in Sujiatun Sub-depression, Lishu Fault Depression, Songliao Basin

The geologic features of the Sujiatun Sub-depression in the Lishu Fault Depression indicated that during the heyday of fault depression development,a large set of mudstone interbedded with sandstone generated stably in the first member of the Yingcheng Formation.This set of shale is characterized by rich organic content,various organic types and is mature and high-mature for gas generation.The average porosity is 3.52% and a mass of fractures can be observed,providing room for free gas accumulation.In addition,the content of brittle minerals is relatively higher,with an average value of 41.1%.The content of quartz ranges from 15.1% to 23.4%.The shale is easy to crack.Field works have shown that the highest gas content in the shale may amount to 3.09 m³/t.The abnormity in total hydrocarbon measuring also predicts the existence of shale gas,indicating for good potential.