Study On Geological Features For Lithologic Deposit Of The First Member Of Dainan Formation In Zhouzhuang Oil-field,Gaoyou Sag

Historical producers obtained high oil productivity from the lithologic reservoir in E₂d₁ of Zhouzhuang field,which lies in Gaoyou sag,even the reported oil reserve is not impressive.E.g.Zhou15?E₂d₁2?: the cumulative oil production is about 5.99×104t while the reported reserve?recalculated in 2012?is only about 12.0×104t,which means the current recovery factor is close to 50%.In recent years,the problems for both exploration and development of this area could be concluded as: the characterization of the updip pinch-out boundaries,the potential of the higher positions,the accumulation possibility of the area around discovered fields such as Zhou15 and Zhou22.This study tried to explore the reasons of the explicit contradictions,then find the potential by solve the problems,in order to make a breakthrough on the exploration and development status,new ideas and strict verifications were used.After the study,the following 5 results were concluded:1.The integrated study result by seismic interpretation,strata correlation and well performance analysis indicated that: there're secondary developed pinnate faults with throw from 20 meters to 40 meters oblique crossing the Wu?1?fault and form the whole structure.2.The former study results said the E₂d₁ sediments are from the lower uplift in eastern Wubao,and this could not explain the pinch out in the east part of E₂d₁2-9 sand;in this study,it was assumed that there might be “dual sources”.After the core observation and synthetic analysis on the experimental data,it was recognized that the sediments of lower E₂d₁2 come from Huazhuang area in the northwest,mainly delta front deposit,relatively further source and stable facies,the thickness of single sand could be about 7 meters to 8meters.3.The characteristic on sand horizontal distribution of E₂d₁2-9 have been finished by proceeded analysis on drilling and mud logging data and cross section analysis on lower E₂d₁2,then predict sand architecture with seismic inversion.4.After the drilling data and performance data analysis,using single sand micro facies and reservoir characteristic results,the updip pinch out boundary of E₂d₁2-9 was confirmed.5.After the statistics on reservoir scale and the relationship with the master faults throw around the Zhouzhuang field,the elements of the lithologic reservoir accumulation were concluded and some interests have been predicted,the recommended appraisals Zhou22-7 and Zhou22-8 were all succeeded.