Study on Reservoir Diversity Controlled by Multiple Factors:Anexample from Liushagangzu 3rd member of Northern Steep SlopeZone in Weixinan Depression ,Beibuwan Basin, South China Sea

Combined with a series of analysis and test data such as seismic, core, drilling, logging and carbon oxygen isotope, this paper analyzes the reservoir differences of the East Zone, middle zone and West zone of the third member of Liushagangzu in the steep slope zone of Weixinan Sag, Beibuwan Basin, analyzes the main reservoir controlling factors of the three zones, and summarizes the reservoir development model. In the study area , reservoir diversity is mainly affected by five factors; 1) Structural factors: structural factors control trap types. In the study area , West zone and middle zone fans mainly develop glutenite deposits controlled by linear provenance, and structural traps are developed; The East zone mainly develop glutenite deposits controlled by point provenance, and lithologic traps are developed. 2) Sedimentary facies factors: sedimentary facies types control reservoir characteristics. Fan delta sedimentary system is developed in the three zones in the study area. The main dominant sedimentary microfacies are underwater distributary channel, with large sand body thickness, low matrix and cement content The main characteristics are the development of primary and secondary pores. 3) Sand thickness factors: sandstone thickness mainly controls the oil and gas bearing property of the reservoir. Taking the oil and gas bearing property of 50% as the boundary, the sand thickness of the West Zone in the study area is 3m; The sand thickness of the middle zone is 5m; The sand thickness of the East Zone is 8m; 4) Physical factors: physical factors mainly control reservoir classification. In the study area ,type I conventional reservoirs (porosity > 12%, permeability > 10md) are mainly developed in the West Zone; middle zone mainly develops type II low permeability reservoir (porosity 6-12%, permeability 1-10md); West Zone mainly develops type III tight reservoir (porosity < 6%, permeability < 1md) 5) Diagenetic facies factors: diagenetic facies factors control the reservoir type. In the study area, West Zone mainly develops weakly compacted and weakly cemented diagenetic facies (type I diagenetic facies); middle zone mainly develops medium compaction medium dissolution and strong compaction medium strong dissolution diagenetic facies; East Zone mainly develops strong compaction medium strong dissolution diagenetic facies. Combined with reservoir control factors and reservoir differences in steep slope zone, two types of multi-factor control reservoir prediction models are summarized: steep slope zone prediction model and conversion zone prediction model. The high-quality reservoir in the steep slope zone is mainly in the middle of the sand body, mainly medium coarse sandstone. The organic acid + atmospheric fresh water two-stage acid fluid is active, the dissolution is strong, and the dissolved substances migrate out of the system. The intergranular dissolved pores, intragranular dissolved pores and matrix dissolved pores are developed, and the physical properties are the best. The high-quality reservoirs in the conversion zone are mainly located in the middle of the sand body, mainly medium coarse sandstone, dissolved by organic acid fluid, developed intergranular dissolved pores, intragranular dissolved pores and matrix dissolved pores, and have the best physical properties.