Key technology on co-exploitation of coalbed methane and tight sandstone in south area of Yanchuan

The test data show that the southern block of Yanchuan is rich in tight sandstone gas resources. In order to increase gas production in single well and exploit the benefit of unconventional natural gas resources in the study area, based on the analysis of the characteristics and development conditions of the coalbed gas-sandstone gas,the identifica- tion characteristics of the sandstone gas are summarized. Then,from the perspective of formation pressure,the geolog- ical feasibility of deep coalbed methane and tight sandstone gas production is demonstrated,and the suitability produc- tion technology of coal series gas is discussed. The results show that the sandstone gas is mainly located in the Upper Paleozoic Shanxi formation and Lower Shihezi Formation,characterized by long lithic quartz sandstone with low porosi- ty and low permeability. The high yield gas area has the logging response characteristics of low GR,low DEN,low CNL,high RT and high AC,which is located on the upper right part of RT -AC intersection diagram. The upper limit of interlayer span for sandstone gas and coalbed methane combined mining is between 155-180 m. The co-exploitation is suitable for the interlayer span is