川中—川北地区下寒武统沧浪铺组一段沉积模式OA

Recently,natural gas exploration in the first member of Canglangpu Formation(Cang-1 member)from Cambrian Series 2 in Sichuan Basin reached a major breakthrough.However,conclusions regarding its sedimentary systems,and changes of the facies zones,are still unclear,which restricts the oil and gas exploration process in this region.In this paper,we clarify the distribution characteristics and sedimentary pattern of gas using outcrop section measurements,core description,thin section identification,and the interpretation of seismic data of the Cang-1 member.The following research results are obtained:Cang-1 in the central Sichuan Basin has a thickness of 70 to 90 m.Under the control of the Mianyang-Changning intracratonic sag and central Sichuan ancient uplift,shelf facies,slope facies,and carbonate platform margin facies with oolitic dolomite(with a relict texture),(sandy)oolitic limestone,calcareous siltstone,argillaceous siltstone,and calcareous mudstone as the main lithology developed.However Cang-1 in the northern Sichuan Basin has a thickness of 90 to 150 m.Under the control of the Han-Nan ancient continent,the Mianyang-Changning intracratonic sag,and the Jiange-Wangcang sag,shelf facies,slope facies,carbonate platform margin facies,and open platform facies with(silty)sandy oolitic dolomite,sandy dolomite,(sandy)oolitic limestone,biohermal limestone,sandy limestone,argillaceous limestone,and calcareous siltstone as the main lithology developed.Grain shoals developed under the joint influence of the Paleogeomorphic highlands,Mianyang-Changning intracratonic sag,Jiange-Wangcang sag,sea level,and a supply of mixed siliciclastic material.The distribution of the grain bank of Cang-1 developed horizontally along the margin of the Mianyang-Changning intracratonic sag and the Jiange-Wangcang sag.A sedimentary model of the central to northern Sichuan Basin was established,which shows the area was affected by the Mianyang-Changning intracratonic sag,the Jiange-Wangcang sag,two uplifts on either side of the Jiange-Wangcang sag,a grain bank along the Mianyang-Changning intracratonic sag,and a sag margin along the Jiange-Wangcang sag that formed a belt.