Abstract: With the deepening of the degree of exploration，and the expansion of the Sichuan Basin natural gas exploration
field，and to look for new exploration replacement area，Sichuan Basin exploration area extends from the basin to the basin
margin. In this context，successive new exploration results are obtained in the second section of the upper Triassic Xujiahe
Formation，but many problems gradually arose in the process of exploration and development，such as gas well productivity
differences，clastic components，thickness and property differences of reservoir between blocks. In response to these problems，
based on the core observation，core analysis data and log interpretation results，and starting from the analysis of deposition and
diagenesis，we make a comparative analysis with reservoir differences and its causes of Member 2 of the upper Triassic Xujiahe
Formation between Longgang and Yingshan Area. We think that far away distance from the source area and repeated washing
by high-energy water are the primary factors causing reservoir differences；strong compaction and multistage quartz overgrowth
are the key factors caused by the reservoir differences，and antigenic chlorite rim cementation and feldspar selective dissolution
are the ultimate factors causing the reservoir differences. The research results explain many of the problems encountered in the
exploration and development of gas reservoirs，and provide effective guidance for the next step of exploration and development
work.

Key words: northeast area in Sichuan Basin, reservoir differences, high energy water, authigenic chlorite rim cementation