Permeability Estimation of Carbonate Reservoir Using Porosity Partitioning Method: A Case Study of Astaka Carbonate Build-Up, Offshore Sarawak

Carbonate reservoirs hold a significant portion of the world's hydrocarbon resources. However, carbonate reservoirs pose a significant challenge in determining reservoir permeability utilizing standard evaluation techniques. Hence, to correctly estimate the permeability of the carbonate reservoir, an evaluation method that includes pore size distribution information is required. Therefore, the primary aim of this study was to improve permeability estimation by incorporating pore size distribution-sensitive measurements into the conventional carbonate evaluation workflow in Astaka carbonate build-up. Herein standard resolution log data with pore size distribution sensitive log data was integrated and augmented by carbonate pore size distribution information from borehole resistivity images utilizing a porosity partitioning method. Thereafter, the porosity partitioning, and permeability analysis results were validated by comparing the calculated permeability with permeability data from modular formation dynamics tester (MDT) permeability. The results showed a good correlation between carbonate permeability and MDT permeability. Hence, the porosity partitioning method improved the permeability estimation in Well B, and a Pickett plot over the water zone provided the value of 0.097 at 102 °C for the formation water resistivity. As a result, the improved workflow offered a more accurate permeability estimation for Astaka carbonate than the conventional approach, which makes the assumption that porosity is inversely proportional to permeability. Therefore, it can be concluded that the improved carbonate evaluation workflow can provide a more reliable and accurate permeability estimate as compared to the conventional evaluation workflow for carbonate reservoirs.