Study On Sedimentary Characteristics Of Braided Delta In Upper 8th Member Of Shihezi Formation, Sourthern Sulige

The area of southern Sulige is about 9000km2, the reservoirs are the sandstone lithologic traps gas reservoirs of fluvial -delta system,which is 8th member of Shihezi Formation and 1th member of Shanxi Formation of upper Paleozoic Permian. Southern Sulige and Sulige gas field have roughly the same sedimental systems and depositional background, their reservoir attribution parameters are also basically the same, southern Sulige has huge exploitational potential. the main targets are 8th member of Shihezi Formation and 1th member of Shanxi Formation.In 2008, the workers of Changqing Oilfield increase exploration efforts in southern Sulige to find the favorable areas. they have drilled 104 exploration wells and 42 development wells,28 of which reach industrial oil and gas flow, southern Sulige has large reserves potential, reaching the scale conditions of development. Therefore,on base of the preliminary exploration datas, I carry out the study of depositional systems, facies,reservoirs evaluation and favorable reservoirs prediction in upper 8th member of Shihezi Formation. The research results will play a guiding and reference role in selection of development block and establishment of development programs.The achievements of this paper were as follows:1, Upper 8th member of Shihezi Formation was divided into two medium-term cyclic sequences and five short term cyclic sequences applying the theory of high-resolution stratgraphy. H8s2 is a whole medium-term cyclic sequence, H8s1 is a ascending half medium-term cyclic sequence.2, Facies of 8th member of Shihezi Formation were dominated by Braided delta by observation of 15 well cores,the facies are divided into 8 microfacies,Braided- delta plain is divided into 4 microfacies:Channel,Channel bar,Flooding sand,Flooding mud. Braided- delta front is divided into 4 microfacies:Subaqueous distributary channel,Subaqueous inter-distributary,Distributary mouth bar Subaqueous flooding sand. Upper 8th member of Shihezi Formation is dominated by Braided delta plain,Channel and Channel bar are more.3, Making the flat and profile distributions of facies by Using the datas of sand thickness and sand content, combinating the predicting channel width.Making plane distribution of gas saturation by being determined by facise. Predicte the gas areas via constraint of sand thickness parameter.4, Establishing multi-parameter comprehensive quantitative evaluation method, which is suitable for the area.There are nine evaluation parameters (thickness, depth, facies, porosity, permeability, net gross ratio, effective thickness, gas saturation, impedance difference), making a comprehensive quantitative evaluation of reservoir using four main factors (facies, permeability, effective thickness, gas saturation), the favored aere is the biggest by using gas saturation factor in evaluating reservoir,however,by using permeability factor, the favored aere is the smallest.