COMPREHENSIVE CHARACTERIZATION OF RESERVOIR VARIABILITY WITH THE ROCK TYPING METHODOLOGY: A CASE STUDY OF FIELD F-A, BREDASDORP BASIN, OFFSHORE SOUTH AFRICA

This research categorizes the sandstone reservoir rock type (PRT) and flow units (FU) by the inaugural effort to amalgamate Winland and MLP studies for the classification of flow units in the Bredasdorp Basin, Offshore South Africa. Within a system of structural and stratigraphic traps lies the upper shallow marine sandstone reservoir, which is the primary target. Shelf and fluvial sandstones are the secondary targets. Shallow marine and shelf sandstones compose quartz-rich, mature reservoirs featuring stable, laterally extensive flow units, whereas fluvial sandstones are classified as less mature lithic types with more heterogeneous flow units influenced by geometry and diagenesis. This study used cores and well logs data from five different wells provided by the Petroleum Company of South Africa (PetroSA). The quantitative identification and classification of rock types and flow units within the reservoir are accomplished by integrating standard and specialized core analysis with a comprehensive core description. The reservoir rocks mostly comprise shale, lithic, siltstone, and sandstone, varying from very fine to medium grain size. Windland R35 analysis. Modified Lorenz plotting, statistical clustering, lithofacies identification, flow capacity evaluation, and storage capacity evaluation was used to classify the rock types and five flow units in the Bredasdorp reservoir. Low quality reservoir is represented by the first group, which includes PRT5 and Nano-port types. Intermediate qualities reservoirs are represented by PRT4 and PRT3, Micro-Meso port types, which include shale, siltstone, and very fine to fine sandstones. High quality reservoirs, including PRT1 and PRT2, Meso-Mega port types, also composed of fine to medium sandstones. The litho-facies (SM4) demonstrate the largest porosity exceeding 17.5 %, permeability surpassing 200 mD, and superior flow unit characteristics with pore throat size more than 20 µm in comparison to the other petrofacies. The litho-facies (SM3) demonstrate relatively high porosity and permeability, while litho-facies (SM2) demonstrate moderate values when compared to litho-facies (SM3). Conversely, the lithofacies of shallow marine (SM1) and fluvial (F) environments demonstrate the lowest porosity, below 13%, permeability under 1.5 mD, and a minimal pore throat of 1 µm among the four litho-petrofacies found in the deposits.