Carbonate Rocks Grouping Using Critical Porosity Approach in Miocene Rocks, Banggai Basin

Abstract Reservoir is the trapped location of hydrocarbons with diverse physical rock properties or high heterogeneity. The characteristics of rock heterogeneity significantly influence the rock’s ability to flow fluids, especially hydrocarbons contained within the reservoir rock. Several methods have been developed to classify the heterogeneity of reservoir rocks, such as the Amaful, Wibowo and Permadi methods, among others. These methods are developed based on experiments using sandstone rocks, although in some studies, they are also frequently employed in categorizing carbonate reservoir rocks. However, these commonly used methods still face challenges in rock classification when actual rock samples are unavailable. In this study, the classification of carbonate reservoir rocks is conducted using a critical porosity approach compared to the classification using the Wibowo and Permadi methods, as well as the hydraulic flow unit method employed in previous research. The data utilized in this study consists of experimental 43 rock samples from the Miocene era of the Banggai Basin. The analysis results reveal that using the Wibowo and Permadi method, 10 rock classifications are obtained, whereas employing the critical porosity approach results in 6 rock groups. Both methods demonstrate a correlation between rock pore structure and rock geometry, where rocks categorized under RT-10 in the Wibowo and Permadi method and RT-6 in the critical porosity method exhibit the smallest pore geometry values compared to other rock groups. Each rock classification signifies the rock’s fluid flow capability, with rocks categorized under RT-1 indicating better fluid flow capability as they possess finer geometries.