Quantitatively classifying and evaluating carbonate reservoirs based on main controls on reservoir development:An example from Dengying 4 Member in the intra-platform zone,Anyue gasfield,Sichuan Basin
As an essential task for well demonstration and reserve submission,reservoir classification and evaluation are indicative significance to size the reservoir quality and type.Conditioned by karstification,fracture growth,and acid fracturing,most carbon-ate reservoirs exhibit strong heterogeneity.However,there is no relationship among these factors which are unclear in their priority and impact,bringing about more complex in quantitative evaluation and uncertainty in this evaluation.It is essential for quantitative reservior evaluation under main controls.Thus,the carbonate reservoirs in the fourth member of the Upper Sinian Dengying Forma-tion(Dengying 4 Member)in the intra-platform zone of Anyue gasfield were taken as examples to identify main controls on reservoir development using static and dynamic data such as core,well logging,tracer,and testing.Furthermore,six parameters,including res-ervoir thickness,shoal-to-formation ratio,acoustic wave,porosity,fracture density,and acid intensity,were selected as reservoir char-acterization.And each weight was calculated through grey relation analysis to determine a comprehensive evaluation indicator.Results show that,(i)in the light of this indicator(IREI),the reservoirs can be divided into four types,such as type I(IREI≥36),II(30≤IREI<36),III(24≤IREI＜30),and IV(IREI<24),among them both type I and II reservoirs account for 57.1%,as high-quality ones,while type III of 28.6%,respectively;and(ii)the proposed quantitative evaluation method has been applied to verifying this classification in a single well,achieving a coincidence of above 90%with the measured production from each reservoir.The evaluation is believed reliable to a certain extent,and can provide a basis for subsequent exploration and development decision-making.
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