Integrating Sedimentology and Petrography With Rock Typing and Flow Units: Implications for Low Contrast and Low Resistivity Reservoir Characterization

The South Sumatra Basin is renowned as a prolific hydrocarbon area since the early era of oil. Resource discovery has declined since the early 21st century. The Talang Akar Formation (TAF) has been massively explored to seek new potential resources. There is an opportunity to look into more detail on the low contrast low resistivity (LCLR) part, which is included as the upper part of TAF. This study will provide an analogue model of the flow unit from outcropped TAF rocks in Air Batu regency. Field observations include outcrop modeling to capture sedimentation patterns, sampling on selected layers for petrographic purposes, facies characterization, geometry measurements from channel deposits, and flow unit modeling. We observed five facies’ associations, which are: transverse bar (Sp); overbank deposit (Fm); dunes (St); planar bed flow (Sh); ripples (Sr); and debris flow deposit (Gms). Petrographic analysis revealed that the samples have a laminar and dispersed shale distribution. The LCLR reservoir detects and controls porosity and pore size ranging from poor to excellent, as well as grain contact. The difference in the facies is any kind of porosity. The facies of transverse bar, dunes, and ripples show very good to excellent porosity with low shale content and are characterized as high-flow units. Yet, the other facies show medium percentage porosity but the interconnection between pores is poor to good, and these have medium to low-flow units.