Based on high resolution seismic data and wireline logs, we have identified several long-term sequences (the third order of Exxon cycle chart) in the Neogene succession of the Pearl River Mouth Basin, the South China Sea. These sequences have a time duration usually less than 1 MA and can be further divided into numerous parasequences. These third-order sequences are bounded by sharp surfaces caused by large relative eustatic sea level falls and rises. They are the most favorable targets for hydrocarbon exploration in the basin because they always form excellent reservoir-seal systems. Exploration practices showed that majority pay zones of the fields and discoveries in the basin were immediately underlying the maximum flooding surfaces within these sequences.

Within the third-order sequences are nested parasequences. The parasequence boundaries play an important role in correlation of time and facies. Each parasequence is considered as a relatively independent fluid unit at a reservoir scale. Sandstones in a same parasequence are generally communicated with each other to form an unified pay zone while sandstones in the adjacent parasequences are separated by flooding surfaces.

The pay zone K22 in Block 16/08 was previously interpreted as a single zone with 3 sub-zones. It was studied in details in this paper and turned out to be 5 parasequences and 1 sequence boundary (SB17.5). Recent drilling and testing results proved the existence of the parasequences and also indicated that parasequences have different oil-water contacts. Facies changes in the parasequences control the reservoir heterogeneties.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah