Abstract: By analysing the conditions of reef forming petroleum in upper Per-
mian Changxin series of Beibei，it is thought that Changxin reef reservoir
rocks in West part of Eastern Sichuan mainly consist of intererystally and
eroSively porous crystalline dolomite and dolomitic reef limestone, the deve-
lopment degree of which is related to the diagenetic circumstances of reef,
The oil and gas primarily come from the Upper Permian Nongtan series, and
secondly from Changxin series, Although there is a small point-reef area
inside the platform, it is distriduted in it in groups and in complex form,
So oil forming conditions are very favorable and it is promising to contain
oil and gas, Reef distribution may be controlled by the paleostructure pro-
duced by the activities of buried basement faults,