Carboniferous system of east Sichuan are dominantly a suit of intertidalsupratidal dolomites

breccia dolomites intercalated with limestones. They had locally developed into porous zones due to pre-Permian erosion. In recent years

several gas fields were found there

but failures often appeared in exploration. The author suggests that the key point of gas enrichment depend upon reserve and trap conditions

the frequent movements of the earth crust and the abundant rifts there played an important role in controlling the migration and accumulation of gas. It is believed that various traps formed at two sides of wide synclines which are interrupted by upthrow faults of related high anticlines are the most potential parts for gas enrichment

and Chixi and Mennan fault-traps are favourable ones.