Sedimentary diagenetic characteristics and controlling factors of reservoir physical properties of Wenchang Formation in Lufeng Sag,Pearl River Mouth Basin,South China Sea
In order to study the characteristics and genetic mechanism of deep reservoirs in Lufeng sag.Thin section identification,FE-SEM observation,XRD analysis and physical property measurement were carried out on the core samples of Wenchang Formation from 7 wells in the southern part of the de-pression.The results show that the rock types of the Wenchang Formation are feldspar quartz sand-stone,lithic quartz sandstone,lithic sandstone and a small amount of quartz sandstone.The complex base is mainly argillaceous and tuffaceous.The cement is mainly authigenic quartz,micrite carbonate and authigenic kaolinite.The physical properties of the reservoir are complex and varied,with porosity ranging from 2.2％to 21.6％,with an average value of 12.0％.It is dominated by secondary pores.The permeability of less than 10×10-3 pm2 accounted for 95％,forming the characteristics of ultra-low-low-medium porosity and ultra-low permeability.The Wenchang Formation mainly develops three sed-imentary facies:delta,braided river delta and fan delta,including three subfacies of delta front,braided river delta front and fan delta front and six sedimentary microfacies.The reservoir porosity of braided river delta is relatively high,and the permeability is relatively medium.The reservoir porosity of fan delta is in the middle,and the permeability is relatively high.The reservoir porosity of normal delta is similar to that of fan delta,and the permeability is relatively the lowest.The underwater distributary channel sand bodies are more conducive to the development of high-quality reservoirs in the braided river delta.The sandstone of Wenchang Formation has experienced early diagenesis stage A and B,middle di-agenesis stage A and B in the study area.The strong compaction-pressure solution leads to the undevel-oped primary pores.Different types and different stages of cementation inhibit reservoir physical proper-ties.The dissolution of feldspar,tuff and debris forms secondary pores and secondary minerals and in-creases porosity,but does not significantly increase permeability.This result provides basic support for the subsequent exploration and development of Wenchang Formation in Lufeng Sag.
Pearl River Mouth BasinLufeng SagWenchang Formationsedimentary diagenetic char-acteristicsreservoir physical propertiecontrolling factors
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维普
