Study Of Hydrocarbon Accumulation Conditions About Dengying Formation Of Sinian In Southwest Of Shunan Area

Based on the study of strata and sedimentary facies from Sinian to lower Cambrian,by using core,thin sections,reservoir quality,drilling,logging,seismic datum and taking the scanning electron microscope,cathode luminescence,TOC test and basin simulation technologies,we analyzed petroleum geological conditions ranging from Sinian to lower Cambrian in Shunan area through the hydrocarbon source rock,reservoir,seal,trap,source-reservoir-seal combination,tectonic evolution and hydrocarbon migration,preservation factors,and figured out zones favorable for hydrocarbon.Studies suggest that Qiongzhusi Formation is the source rock of Dengying Formation hydrocarbon and it covers the whole area by thickness of 140-450 m.Samples TOC > 1.0% take 71.4 percents.Organic matter type is type I.Ro is generally greater than 2.0%.Hydrocarbon generation intensity ranges from 60 to 120×108m3/ km2.Member Two and Member Four are the reservoirs of Dengying Formation.Dissolved pores and caves,fractures are main reservoir space of Dengying Formation.The development of reservoir is controlled by lithology facies and karstification.Porosity of algal dolomite(2.4%)is greater than crystal powder dolomite(1.65%)in Member Two.Porosity and permeability of karst platform is greater than karst slope and karst depression.Qiongzhusi Formation also is the seal of the whole area with the thickness of 200-500 m,and its porosity(<1.02%)and permeability(<0.0126mD)are very low.Trap types include stratigraphic unconformity trap and stratigraphic unconformity-structure composite trap.Hydrocarbon source rock of Qiongzhusi Formation and reservoir of Dengying Formation combined as source-reservoir-seal combination.Different regions with different denudation extent of Member Four,configuration elements differ.Primary migration of hydrocarbon happened from Cambrian to Early Silurian and Permian.Ages after Triassic including Triassic are hydrocarbon adjustment and redistribution period.During Jurassic and Cretaceous oil accumulated in deposit cracked into gas.Paleogene and neogene are hydrocarbon reservoirs damage and adjustment period.Favorable districts of hydrocarbon have characteristics of high hydrocarbon generation intensity,developed karstification,inherited palaeo-uplift,shale distribution of Maidiping Formation,no faults.Class ? areas consist of Gaomuding district,Datachang-Yibin district and Xinglongchang-Dengjingguan-Qingshanling district.The only one class ? area is Maliuchang-Wuzhishan-Tiangongtang district.The only one class ? area is Naxi-Lianhuasi-Changning-Yujiaba district.