The Wenchang Formation in the Lufeng Sag

Pearl River Mouth Basin

is sedimentary fill deposited in the rifting stage.High quality reservoir was developed in the 5

th

Member of Wenchang Formation which was deposited during the early stage of rifting.To uncover the genetic mechanisms of high quality reservoir

various data including seismic

drilling

core

thin section

scanning electron microscope (SEM) images and mercury experiments were integrated to analyze the sedimentary facies

reservoir characteristics and diagenesis of the 5

th

Member of Wenchang Formation in the LF-A Sub-sag

Southern Lufeng Sag.The research results indicate that the 5

th

Member of Wenchang Formation is dominated by deposits of braid river delta front subfacies.Lithic quartz sandstones and feldspathic quartz sandstone are the dominatant rock types.The remnant primary intergranular pores are the main reservoir spaces.The 5

th

Member of Wenchang Formation is characterized by low porosity

low-medium permeability

and low-medium displacement pressure.High quality reservoirs mainly present in thick channel sandstones with low lithic content and high maturity

reflecting the control of high energy environment on reservoir formation.The cementation and compaction processes in the early stages of diagenesis decreased porosity

while the dissolution process in the late stages of diagenesis enhanced reservoir property.Structural uplifting process in the early stages prohibited strong compaction by the overburden

making it possible for the preservation of large amount of primary pores

thus was the crucial factor for the formation of high quality reservoirs.