Study On Logging Evaluation Method Of Reservoir In High Water Consumption Zone

The 8th sand formation of 2nd sand group in Southern Tuo 11 has entered an extremely high water-cut stage and has a high water consumption zone.The existence of high water consumption zones has an important impact on the production and development of oilfields,which reduces the efficiency of water injection and oil recovery.Through data investigation and analysis of high water consumption zones,it is clear that the high water consumption zones of the 8th sand formation of 2nd sand group in Southern Tuo 11 have the characteristics of"inflection point"in the phase permeability curve and"inflection point"and upward warping in the type A water drive curve during the ultra-high water cut period of reservoir.Based on the analysis of formation mechanism of high water consumption zone,the main controlling factors and characterization parameters of high water consumption zone are determined from three aspects of reservoir lithofacies,reservoir heterogeneity and reservoir fluid.Based on the systematic analysis of core data and geological data,and according to the combination of lithology and bedding,the lithofacies classification system of the 8th sand formation of 2nd sand group in Southern Tuo 11 is established.On the basis of single lithofacies division and under the control of sedimentary microfacies,the reservoirs in the study area are divided into eight lithofacies combination types,including dam body I,dam body II,dam upper river and distant bar.Through sensitivity analysis of logging response,conventional logging data is not sensitive to single lithofacies,but natural gamma ray,acoustic time difference,resistivity and other logging responses are sensitive to lithofacies association.Four types of lithofacies Association of dam body are identified and interpreted by gray correlation analysis method.By means of multivariate regression modeling method,the interpretation model of grain size median logging is established,and the quantitative interpretation of various lithofacies assemblages is carried out.The interpretation results show that there are differences in shale content and grain size median among different types of lithofacies assemblages.The analysis results of the relationship between lithofacies and reservoir show that the main body of core analysis data in high water consumption zone is the type of lithofacies combination of dam body II.Based on lithofacies analysis,acoustic porosity model,porosity-permeability model and multiple regression permeability model are established to improve interpretation accuracy.Logging interpretation of reservoir fluid in high water-consuming zone based on lithofacies is carried out.The difference of fluid characteristics of reservoirs with different lithofacies combination types is analyzed.The reservoir with lithofacies type II has the highest water-phase permeability,the lowest residual oil saturation and the best permeability of reservoir,which is easy to form high water-consuming zone.Modeling and single well interpretation of fluid parameters such as water saturation,water content and pore sweep coefficient in high water consumption zones according to different lithofacies types can provide a basis for identification and prediction of high water consumption zones.The high-water-bearing zone facies logging evaluation,the reservoir physical property parameter logging evaluation,and the reservoir fluid parameter logging evaluation were carried out.The lower limit of physical properties of the high water consumption zone is determined by different rock facies combination types,and the lower limit of the fluid parameters of the high water consumption zone with water saturation less than 65%,pore wave coefficient greater than 0.87 and water content greater than 92%is determined.The distribution pattern of high water consumption zone is predicted.It is found that the high water consumption zone is more developed in the direction of the source,and is not developed in the direction of the cutting source.The high water consumption zone is preferentially developed in the lithology body II lithofacies combination;Among the three small layers,8₃ formation units have the highest proportion of high water consumption,8₂ formation units and 8₁ formation units are similar;8₃ formation units are mainly developmental high water consumption,while the proportion of potential high water consumption belts and developmental high water consumption belts in 8₂ formation units and 8₁ formation units are similar.