Abstract:

In the early Eocene,Jianghan Basin was a shallow saline lake fed by rivers.Three types of sands were formed within this lake: deltaic sands,nearshore beach sands and offshore beach sands.Among them,the more important are Hougang deltaic sands which are composite,overlapped ones,and which were developed during the desalinating period.The principle features of the saline lacustrine and deltaic sediments are the antithetic and complementary to each other.Because of slight subsiding,lower rate of sedimentation,shallow water body and higher salinity at earlier Eocene,the basin studied was not favorable for organism breeding.Therefore,the abundance of organic matters in the basin was poor,with sapropel predominantion,and conditions for oil generation was less favorable.Though sands exist in this lacustrine basin which are favorable for oil accumulation,oil and gas reservoirs could be rarely formed.It seems that the potential region for searching small oil and gas fields might be to the cast where offshore lacustrine beach sands exist,and to the west where front deltaic sands exist.