Impact of rock fabric on flow unit characteristics in selected reservoir sandstones from West Baram Delta Offshore, Sarawak

The successful application of enhance oil recovery (EOR) technology requires an accurate understanding of the internal architecture of reservoirs and complex distribution of flow unit characteristics within different lithofacies. However, flow unit characteristics in the reservoir lithofacies of West Baram Delta Offshore, Sarawak, remain unexplored. Therefore, this paper investigates potential hydraulic flow units (HFUs) present within the five (5) identified sandstone lithofacies using thin sections, scanning electron microscopy (SEM), two-dimensional (2D) petrographic image analysis and helium porosimetery. The identified lithofacies include massive coarse-grained sandstone (MCGS), massive medium-grained sandstone (MMGS), massive fine-grained sandstone (MFGS), massive friable fine sandstone (MFFS) and massive very fine grained sandstone lithofacies (MVFGS). A plot of reservoir quality index (RQI) against normalized porosity (фz) showed five main hydraulic flow units (HFUs) within the identified lithofacies. The MFGS, MFFS and MVFGS lithofacies exhibited moderate to high matrix fractions and moderate to poor sorting, suggesting high tortuosity and hence characterized by low flow zone indicator (FZI). On the other hand, the MCGS and MMGS lithofacies exhibit very low to low matrix fractions, medium to coarse grain sizes and moderate to well sorting, signifying lower tortuosity, and hence characterized by relatively higher flow zone indicator (FZI). Thus, a hydraulic flow unit (HFU) can be formed by more than one lithofacies that exhibit similar fluid characteristic attributes, regardless of the difference in depositional environment and diagenetic processes undergone. This study concludes that HFU scattered plot can serve as a qualitative model for the characterization of flow unit characteristics in a well-comprising different lithofacies, particularly for field development plans in the West Baram Delta.