Evaluation of Bioclastic Limestone Reservoir Heterogeneity Based on Degree Coefficient Method

Abstract The complex pore structures and diverse pore types lead to strong heterogeneity and complex oil-water relationship in bioclastic limestone reservoirs. Accurately understanding the characteristics of reservoir heterogeneity is of great significance to the overall development and deployment of the block and the improvement of oil and gas recovery. Taking M layer bioclastic limestone reservoir in H oilfield as the main research object, firstly, the main controlling factors of reservoir heterogeneity are defined. On this basis, the characterization parameters of reservoir heterogeneity based on degree coefficient method are constructed. Then a multi-scale (intra-layer, plane and interlayer) quantitative evaluation method of reservoir heterogeneity is formed, through which the three-dimensional evaluation of heterogeneity combining vertical and horizontal directions is realized. The results show that the secondary effects such as dissolution lead to the diverse pore structure of bioclastic limestone reservoirs, which is the main reason for the large difference of reservoir quality and strong heterogeneity. Reservoirs with strong heterogeneity are seriously transformed, which corresponds to high-quality reservoirs with high yield. The heterogeneity evaluation method established in this paper has a good application effect in the study area, and plays an important guiding role in correctly evaluating reservoir performance and exploitation value.