The Research of Sedimentary Facies and Prediction of Favorable Reservoir of the Upper Carboniferous Carbonates in North Tluwa Oilfield,Pre-Caspian Basin

The North Tluwa Oilfield is a big oilfield which was discovered in the eastern Pre-Caspian Basin in recent years,the carboniferous carbonate is the most important oil-bearing series. Through the analysis of core,logging data,and the micro-observation of many sections and SEM,the upper-carboniferous carbonate was considered belongs to carbonate platform facies,and could be divided into 3 subfacies and 7 microfacies,which including cream rock terrace,dolomite terrace,lagoon microfacies and so on. The analysis of sedimentary evolution of profiles and planes indicates that,it was in a process of falling of sea level,in the period of Б2,the area was open platform subfacies,but in the period of A2,most of it was evaporate platform and restricted platform subfacies. Through concluding the distributary regular of every microfacies in the plane,the sedimentary model of area was build.Through the analysis of the type and patterns of micro-core,combined the research of microfacies,the dolomite terrace was found in the restricted platform and platform beach microfacies in the open platform have the best reservoir physical property,the silt-crystalline bioclastic dolostone,crystal grain dolostone,and sparry grain limestone and biological framework limestone are the best reservoir. The upper research will offer a new geological basis to the subsequent evaluation and development.