Characteristics And Identification Of Chang 4+5 Low-resistance Oil Layer In Yanchi Area,Ordos Basin

The low resistivity reservoirs refer to the reservoirs with a resistivity increase rate of less than 2 compared with the adjacent water layer in the same oil-water system.With the increasing consumption of resource,the exploration and development of the low-resistance oil layers are becoming more and more deep.The formation of low-resistance oil layers is complicated,and the difference is large in different regions,and the conventional logging characteristics are not obvious.Therefore,it is extremely important to carry out research on low-resistance oil layers.Based on the geological characteristics of Chang 4+5 formation in Yanchi area,this paper comprehensively analyzed the static logging data,the dynamic oil test production data and the experimental analysis data,and studied the genesis and methods of identifying of Chang 4+5low-resistance oil layers.The results show that:(1)In this study area,the low-resistance oil layers of the Chang 4+5 were caused by the low structural amplitude,high irreducible water saturation,the influence of clay minerals,the high salinity of water,and so on;(2)There are four methods for identifying the Chang 4+5 low-resistance oil layer in the study area,such as the intersection plate method,the reservoir resistance increase rate method,the calculated natural potential method and the array induction logging identification method;the feasibility of the identification methods is confirmed by the test oil data;(3)The lower limit of the resistivity of the low-resistance oil layers in the study area is 3.75?·m,the acoustic is not less than 220?s/m,and the oil saturation is not less than 24.97%.According to the research results,it was predicted that the distribution range of the low-resistance oil layer of Chang 4+5 in the study area.