Research On Reservoir Evaluation For Dainan Formation In Zhenwu-Caozhuang Area,Gaoyou Sag

The Zhenwu-Caozhuang area lies in the deep depression zone of Gaoyou Sag,Subei Basin.There are some problems such as complexities in structure and uncertainties in reservoir distribution in Dainan formation,a formation of the Paleogene and the primary contributive zone of this area.This paper intends to introduce a research on reservoir evaluation for the Dainan formation in Zhenwu-Caozhuang area.Guided by theories from sedimentary petrography,reservoir geology,oil-gas geology and other relative theories,a fine stratigraphic framework had been built after strata classification and correlation based on both markerbed and cycle correlation methods;the fine interpretation had been proceeded and finished by structure analysis,3D visual seismic interpretation,attribute analysis and other relative methods;the sedimentary micro-facies in this area had been described with facies indicator recognized from core observation;the reservoir distribution had been predicted by using seismic inversion,forward,attribute analysis and other methods.Finally,a synthetic evaluation of the potential AOI had been finished.Acquisitions from the research:(1)There are some clear cycle features in Dainan formation,and the black shale with low resistivity is the primary marker-bed in correlation for lower Dainan.The whole Dainan formation could be divided into12 sand sets.(2)This area is dominated by north-dip faults while some south-dip faults still grow in local regions(Zhen 84 block and Zhen 2 block);the structure of this area consists of two anticlines—Zhenwu anticline and Caozhuang anticline,and the depth in Zhenwu is higher than that in Caozhuang.(3)The deposit environment here is fan delta and nearshore subaqueous fan,the reservoir mainly distributed in subaqueous distributary channel and fan channel;nearshore subaqueous fan only grows in Caozhuang area while fan delta is widely distributed in the entire area.(4)Good results from prediction work on sands with different features after synthetic provenance analysis,seismic forward and inversion.(5)Results of the synthetic evaluation on this area indicates four potential AOIs: north Zhen24,east Zhen 29,Zhen 63 and Cao 4.