Abstract:

Biyang Depression is a secondary structural unit in Nanxiang Basin. The depression is in half-graben shape which faulted in the south part and overlapped in the north part. The depositional stage of Hetaoyuan Formation was the major fault-subsided stage of the depression, source-reservoir-cap rock assemblage with great thickness and three types and nine subtypes of oil-gas pods formed in the deep depressed area. The discovered oil and gas pools are distributed in circularity around the depression. From shallow to deep of the depression, the oil pools change from dense oil gas to normal and then condensed oil pools. The inherited depression in the north part of the slope is the major oil-gas enriching area, the two sets of fractures within the area are favourable for the formation of fault-noze and fault-block oil pools. The thick mudstone of the third member of Hetaoyuan Formation is regional cap rock of the pools.

Key words: oil-gas pool, formation condition, type, enrichment, Hetaoyuan Formation, Biyang Depression