Analysis On The Diagenesis Of The Ordovician Dolomite Reservoir In The Gucheng Area Of The Tarim Basin

Some research institutions have made a breakthrough in Oil and gas industry of Ordovician Dolomite Reservoir in the Gucheng area in recent years,therefore,this area has become an important exploration area in the eastern Tarim Basin.Due to the poor exploration degree,few wells and poor basic geological study,especially the formation of dolomite reservoir space,poor study of the diagenetic evolution and developmental pattern of dolomite reservoir,the exploration is restricted.In this paper,a systematic analysis of carbonate reservoirs is developed to study the diagenesis of the Ordovician carbonate reservoir in the Gucheng area and its influence on the formation of the effective reservoir.The following four aspects of achievements have been obtained:The lithology and geochemical identification marks of dolomitization in the Gucheng area is established.Five types of dolomitization are identificated: dolomite formed by evaporative pump in penecontemporaneous stage,dolomite formed by seepage reflux in penecontemporaneous stage,dolomite formed in shallow burial stage,dolomite formed by recrystallization in deep burial stage,dolomite formed by the hydrothermal.The fine-intermediate grain and the intermediate-coarse grain dolomite is the high quality reservoir rock.The formation of the dolomite reservoir is the result of dolomitization and hydrothermal dissolution,this conclusion is gained by restoring the formation and evolution history of reservoir space at different diagenetic stages in the study area.Dolomitization in early diagenetic stage and hydrothermal dissolution in late diagenetic stage can form effective reservoir of oil and gas.