Carbonate Reservoir Geologic Characteristic Of The Third Member Of Shahejie Formation In Dawangzhuang Area In Raoyang Sag

It is proved that lacustrine carbonate rock is one of the most important oil/gas reservoirs through the practice of oil and gas exploration。Sedimentary characteristics,sedimentary model and reservoir characteristics of the lacustrine carbonate rock in the upper third member of Shahejie Formation in Raoyang sag are systematically studied in this paper on the basis of geology, logging and chemical analysis data.It is suggested that there are mass lacustrine carbonates rocks in the upper third member of Shahejie formation in Raoyang Sag through the comprehensive analysis of core and microcospic dentification. It can be divided into sand-clastic dolomite, oolitic dolomite, chondruie dolomite, algal-gobbet dolomite, algal dolomite, bioclast dolomite,grain-bearing micritic dolomite,micritic dolomite and terrrigenous clastic-bearing dolomite.Algal- sand-clastic dolomite and oolitic dolomiteare the most important rock in the researth area.According to their lithology-electric characteristics and single-well facies, the sedimentary facies are determined. They consist of algal beach, oolitic beach, micritic beach and terrestrial grain beach. According to the comprehensive analysis of sedeimentary characteristics, a comprehensive sedimentary model is established in this area.The comprehensive analysis shows that in the upper third member of Shahejie Formation, the peripheral relief of Raoyang sag becoming flattish and the lake level rosing rapidly, the wave action strengthened and the delta faded;the river's ability of loading muddy sand became small and the supply of detrital material of terrigenous origin was stagnate and inadequate.As a result, the reserve of carbonate solution gradually became oversaturated causing a lot of lacustrine carbonate rocks to develop.The diagenesis of the area includes compaction, pressure-solution, cementation, dolomitization, solution, recrystallization and silicification. It is proved that lacustrine carbonate rock in the upper third member of Shahejie Formation have two type of reservoir space pore and crack, the secondary intergranular dissolved pore is the most important reservoir space.Based on the analysis of petrology characteristics, types of reservoir space , pore microgeometrical and oil of lacustrine carbonate,the carbonate reservoir in the upper third member in Dawangzhuang area is divided into four categories: algal beach and oolitic beach are mainlyⅠ,Ⅱcategory reservoir; terrestrial grain beach isⅢcategory reservoir and the reservoir of micritic beach isⅣcategory non-reservoir.Studying mechanism and distribution of macro and micro remaining oil in carbonate reservoir of the study area in the upper third member of Shahejie Formaion, the paper put forward that the remaining oil enriched mainly in margin facies of algal beach, oolitic beach, terrestrial grain beach from sedimentology; The interlayer dist ribution of remaining oil mainly enriched in up side and downside of the reservoir. Micro remaining oil has five shape types, such as network, speckle, attached, trickle and conf use of oil and water.Moreover, network and speckle remaining oils are active oils being able to improved by water flood.