Saturation Interpretation Model And Quantitative Evaluation Of Water-flooded Zone In P Block

P block reservoir is a layered sandstone reservoir with certain natural water energy,in the process of oilfield development,there are some phenomena,such as edge water advancing,bottom water coning and injection water flooding,at present,it has entered the middle and high water-flooded stage.The resistivity of water-flooded zone decreases obviously,and there is low resistivity zone in this area.The resistivity range of low resistivity zone and water-flooded zone overlaps,so it is difficult to distinguish low resistivity zone from water-flooded zone.Therefore,it is necessary to study the influencing factors of low resistivity zone and water-flooded zone,and take these factors into account in saturation evaluation,so as to improve the coincidence rate of logging quantitative interpretation of water-flooded zones.According to the geological characteristics of reservoir in P block,combined with core data,logging data and dynamic production data,the relationship between reservoir lithology,physical property,oil-bearing property and electrical property is studied.It is concluded that high shale content and complex pore structure are the main factors causing low resistivity zone,and high water saturation is the main factor causing low resistivity of water-flooded zone.Quantitative interpretation methods of shale content,porosity,permeability and irreducible water saturation parameters are established based on actual logging data and core analysis data.Based on the analysis results of factors causing low resistivity of low resistivity zone and water-flooded zone,the equivalent rock element model and pore geometric conduction theory are selected to describe the influence of pore structure on rock conduction law,and the general Archie equation and parallel conduction theory are used to describe the influence of shale on rock conduction law.Three saturation interpretation models are established based on equivalent rock element model and general Archie equation,equivalent rock element model and parallel conduction theory,general Archie equation and pore geometric conduction theory.The theoretical and experimental validation of the three saturation interpretation models show that the three saturation interpretation models established in this paper are correct.The theoretical analysis and practical application results show that the saturation interpretation model based on equivalent rock element model and general Archie equation is the best.The oil-water splitting coefficient is established by product of thickness,porosity,permeability,resistivity or conductivity,and the production of composite zone is splitted and the relationship between water production rate and oil displacement efficiency is established,and the criterion for dividing water-flooded level by oil displacement efficiency is determined.21 water-flooded wells in P block have been processed by using the established quantitative interpretation method.Among them,there are 12 water-flooded wells are interpreted.8 strong water-flooded zones,20 medium water-flooded zones,34 weak water-flooded zones and 238 oil zones are determined.Comparing quantitative interpretation results with dynamic production data,it is found that the interpretation coincidence rate of water-flooded zone is 90.0%.It shows that the established quantitative interpretation method can distinguish low resistivity zone from water-flooded zone,and is suitable for the interpretation of water-flooded zone in P block.