Research On Reservoir Characteristics And Controlling Factors Of Cambrian Longwangmiao Formation In South Central Sichuan

Cambrian Longwangmiao carbonate gas reservoir is an important discovery of oil and gas exploration in the south of central Sichuan Basin in recent years,which is an important gas production capacity replacement area for Sichuan Basin as its huge exploration and development potential.Guided by sedimentary petrology,reservoir geology,logging geology,applying core,thin section,logging,analytic and test data combined with advanced experimental analysis techniques,Reservoir characteristics such as reservoir lithology,space types,pore structure,are comprehensive studied in the area.Then the controlling factors of reservoirs are summarized.Finally,the classification and evaluation of reservoirs are made,The main research results are as follows:(1)Reservoir characteristics of Longwangmiao formation are studied by the core,thin section,analytic and test data,Reservoir lithology is mainly residual dolarenite,dolarenite;reservoir space types are karst cave,pore and fracture;it is low porosity and low permeability reservoir,The first section is better than the second section of Longwangmiao formation;The reservoir quality is better and the pore geometry is characterized by low-middle porosity and small-middle throat;The capillary pressure curve can be divided into four types and the I is the best.(2)On the basis of the mineralogy and geochemistry of the reservoir,reservoir diagenesis types and characteristics of Longwangmiao formation are studied,which is divided into construction,preservation and destruction,Four stages of reservoir pore evolution are determined which are(quasi)syngenetic diagenetic stage,early diagenesis stage,supergene karstification stage and middle-late diagenesis stage.(3)The formation and distribution of the reservoirs are controlled by the sedimentary facies,the early burial dissolution,the supergene karstification and the hydrocarbon filling.Sedimentary microfacies controlled the distribution of reservoir development;the early burial dissolution and supergene karstification generated a large amount of reservoir space;The hydrocarbon filling effect not only forms a part of buried dissolution pores,but also plays an important role in protecting the reservoir space.(4)According to the characteristics of reservoir physical properties,pore structure and capillary curve,the reservoir is divided into four types:type ? with the porosity is more than 7%and permeability is>0.5mD;type ? is 4%-7%and 0.05-0.5mD;type ? is 2%-4%and 0.02-0.05mD;the porosity of type ? is less than 2%and permeability is less than 0.02mD;better reservoir of ? and ? are about 52%in the area.