Develpoment Mechanism Of Dolomite Reservoir Of Evaporate Platform In The Central Uplift,tarim Basin

Based on the previous study,taking Lower-Middle Cambrian Formation in the Central Uplift Belt,Tarim Basin,as the study object,via various data such as outcrops and well cores,well logging,geochemical data and seismic data,the dissertation is focused on the sedimentary environment and diagenetic environment of dolomiteevaporate system,characteristics and controlling factors of dolomite reservoir in evaporative platform to predict the distribution of dolomite reservoir.According to the structure mainly reflecting the genetic mechanism,dolomite in evaporative platform could be divided into residual dolomite and crystalline dolomite.Furthermore residual dolomite is subdivided into(residual)doloarenite-dolorudite and microbial dolomite.During early-middle Cambrian,the facies of Central Uplift Belt is mainly evaporate platform,with restricted platform ocassionally.Twelve microfacies and five microfacies associations are identified in dolomite-evaporite sedimentary system.The sedimentary evolution and sedimentary pattern of the evaporate platform are summarized via well data.Distribution of sedimentary microfacies of each formation of low-middle Cambrian in the central uplift belt is drawn via well and seismic data.High frequency cycles are identified by the application of wavelet transform of natural gamma ray curve,for the proportion of evaporite and dolomite is affected by frequent fluctuation of sea level in evaporatic environment.Comprehensively,diagenesis environment of dolomite in evaporate platform is studied through thin section,cathodoluminescence,carbon and oxygen isotopes and X-ray diffraction techniques,After initially formed in the evaporitic seawater environment,supratidal zone micritic dolomite is further transformed in the meteoric freshwater environment or extremely shallow burial environment.And after initially formed in the evaporitic seawater environment,intertidal zone dolomite may gradually transform into fine-crystalline dolomite during shallow burial period.And microbial dolomite and fine-crystalline dolomite could be dissolved in the deep burial period.During shallow burial period,cement of(residual)dolarenite-dolorudite is transformed by dolomitization.Dolomite reservoir of evaporate platform is classified by sedimentary facies into gypsum-dolomite flat dolomite reservoir,gypsum breccia dolomite reservoir,microbial mat/mound dolomite reservoir and psammitic bank dolomite reservoir.On the ground of sedimentary facies,sequence boundaries,diagenesis and tectonic movement,the controlled factors of the dolomite reservoir are discussed and advantageous reservoir distribution is predicted.The optimal microbial mat/mound dolomite reservoir is in the Xiaoerblak Formation,while the optimal gypsum-dolomite flat dolomite reservoir and gypsum breccia dolomite reservoir are in the Awatag Formation and Wusonger Formation.