Diagenetic analysis of the Lower Paleozoic dolomite reservoirs on the western side of the Xuefeng Mountain

Based on an analysis and discussion on the diagenesis of Lower Paleozoic marine dolomite reservoirs in the study area, the authors acquired a better understanding of the characteristics of these reservoirs. On the basis of oil and gas geological data obtained through the analysis of the Sinian Dengying Formation and the regional distribution characteristics of the Cambrian Wuling - Furongian marine dolomite reservoirs, in combination with ordinary thin section, casting thin sections, carbon and oxygen isotopes, major elements, electron microprobe analyses and other data, the authors conducted comprehensive quantitative researches on the types of diagenetic types that played a constructive role in reservoir development, and explored their differences in vertical and horizontal directions. The results show that the distribution characteristics of the dolomite in the study area are significantly affected and controlled by facies change; Sinian Dengying Formation consists mainly grained dolomite, residual particles of dolomite and algal dolomite, whereas Wuling - Furongian System comprises chiefly calcite dolomite, grained dolomite and residual grained dolomite. Dolomite of Dengying Formation and Wuling-Furongian System experienced such diagenetic actions as compaction and dissolution of cement and mineral filling, recrystallization, dolomitization, silicification, dissolution and rupturing, which all played positive roles in the formation of favorable reservoir space, with dolomitization, dissolution and rupturing being most important. Regional correlation shows that dolomite reservoirs in Wuling-Furongian System and in Dengying Formation are somewhat different in vertical and horizontal directions and assume heterogeneity in regional distribution. The results obtained by the authors provide the basis for further regional block optimization.