Abstract: Oilfield A in Enping sag was located in the ancient Pearl River delta front in the Neogene period. The sand bodies were generally thin, which made it difficult to predict the reservoir. The alternating of fluvial and oceanic processes also complicated the sedimentary microfacies transformation. These factors affect the increase of reserves and production in the future. Concerning the above problems, based on fine layer correlation and logging interpretation results, the average sandstone volume fraction in sand sets is used to characterize the relative sea level changes according to the characteristics of flat terrain and fewer changes in stratum thickness of ancient delta. Research shows that the average sandstone volume fraction of Zhujiang Formation and Hanjiang Formation in the study area can better represent the relative sea level changes and accurately describe the fifth order relative sea level change. By analyzing the sedimentary microfacies of sand sets, it revealed a good correspondence between relative sea level changes and the sedimentary microfacies evolution of deltas. The feasibility of characterizing relative sea level changes based on the average sandstone volume fraction of sand layers was verified, which can be used to predict the evolution of deltas and the superposition relationship of sand bodies.

Key words: sea level change； Pearl River delta, sedimentary microfacies, sandstone volume fraction, Neogene, Enping sag