Characteristics and genetic mechanisms of reservoirs of Wenchang Formation in the HZ26 area of Huizhou sag,Pearl River Mouth basin
Huizhou sag of the Pearl River Mouth basin is rich in oil and gas resources,and the exploration of Wenchang Formation is limited by reservoirs.Taken sand reservoirs of Wenchang Formation in the HZ26 area of Huizhou sag as research object,researches focusing on reservoir characteristics,mechanism of pore increase and preservation,process of diagenesis and reservoir-forming were conducted through applying thin section identification,scanning electron microscopy,inclusion temperature measurement,etc..The results show that:①The reservoirs of Wenchang Formation are dominated by litharenites and lithic quartz sandstones,and tuffaceous matrix is pervasively distributed among grains.②Meteoric fresh water dissolution in eodiagenesis A stage and organic acid dissolution in eodiagenesis B and mesodiagenesis A stage are the most important pore increasing mechanisms.The poikilitic laumontites deposited in eodiagenesis stage can effectively resist compaction and protect the intergranular pores,and the early hydrocarbon charging can also protect the intergranular pores by inhibiting cementation.③ The diagenesis and reservoir-forming processes of WC41,WC42,and WC43 sand groups in Wenchang Formation are remarkably different.The primary pore development zone of WC41 sand group has a low content of matrix and a simple diagenetic evolution process.Oil and gas migrated along the faults and accumulated under the overlying unconformity.Tuffaceous matrix is widely distributed within WC42 sand group and tuffaceous alteration was generally developed,with laumontites,which are able to improve the resistance to compaction of rock,precipitated.After the dissolution of laumontites by acid,a large number of intergranular dissolution pores were formed.The laumontite dissolution zone is another favorable place for oil and gas accumulation in the study area.For WC43 sand group,both the mud and matrix-rich zone proximal to crater and the volcanic breccia buildup zone distal to crater suffered from intense compaction,and the reservoir quality is poor.The research results can provide a reference for oil and gas exploration of Wenchang Formation in the HZ26 area.
Pearl River Mouth basinHuizhou saghigh-quality reservoirWenchang Formationdiagenetic evolutionpore increase and preservation
万方数据
维普
