Reservoir characteristics and genetic differences between the second and fourth members of Sinian Dengying Formation in northern Sichuan Basin and its surrounding areas

Yong LI,Xingzhi WANG,Mingyou FENG,Deming ZENG,Shengyang XIE,Rui FAN,Liangjun WANG,Tao ZENG,Xuefei YANG

Table 1 Features and main control factors of Deng-2 and Deng-4 reservoirs in the ROI.

Layer Rock type Pore space and interstitial materials Petrophysical property and connectivity Reservoir distribution Control factors Deng-2 Thrombolitic dolostone, stromatolitic dolostone, and dolomitic karst breccia with grape lace-shaped cement Isolated dissolved pores and dissolved cavities extended parallel to the layer among algal frame, and cavities in grape lace-shaped cement in dolomitic karst breccia, often partially filled with multi- phase dolosparite, with no bitumen observed. Poor connectivity, low porosity, and low permeability Middle and upper Deng-2 Mound-shoal complexes + supergene karstification Deng-4 Thrombolitic dolostone, stromatolitic dolostone, crystalline powder-scale dolostone, and dolarenite Dissolved pores, dissolved cavities, intercrystalline pores, intercrystalline dissolved pores, and intergranular dissolved pores among algal frame, partially filled with bitumen and some quartz. There is hardly dolomite filled in pore space. Good connectivity, low to moderate porosity, and low permeability. High porosity and moderate permeability locally. Middle, upper and top Deng-4 Mound-shoal complexes + burial dissolution