Sedimentary Facies and Reservoir Characteristics of the Meligan Formation in Lawas, Sarawak: Elucidating Pore Imaging Using the J-Por Method
MUHD NUR ISMAIL ABDUL RAHMAN, DONY ADRIANSYAH NAZARUDDIN, MOHAMAD AQIL AZMI BIN MOHD RASEDI

Faculty of Science and Marine Environment,
Universiti Malaysia Terengganu,
21030, Kuala Nerus,
Terengganu, Malaysia.

Abstract

The research area is situated in the Lawas region of northern Sarawak, Malaysia. Our observations were primarily focused on selected outcrops along road cuts and exposed hills. These outcrops are widely distributed in several localities within the Lawas region. We identified sedimentary sequences by examining facies variations, indicating a shoreline environment based on the sedimentary structures. Additionally, we processed thin sections of rock samples using Image-J software to determine the porosity of the sampled rocks and predict their reservoir potential. In our study area, we successfully identified and characterized five distinct facies namely, Facies 1: Planar Cross-Stratified Sandstone (PcS), Facies 2: Swaley Cross-Stratified Sandstone (ScS), Facies 3: Hummocky Cross-Stratified Sandstone (HcS), Facies 4: Parallel Laminated Sandstone (Pl), Facies 5: Heterolithic Rock (He). Our facies evaluation revealed that these sedimentation settings corresponded to foreshore, upper shoreface, middle shoreface, lower shoreface, and tidal environments (with minor occurrences). Furthermore, the petrographic analysis of thin sections of facies 1, 2 and 3 demonstrated good to very good porosity values, ranging from 14.324% to 25.920%. This porosity range suggests a promising reservoir potential for hydrocarbon accumulation in the Meligan Formation. The stratigraphic units of the paralic system in Sarawak, which may potentially host hydrocarbon reservoirs, have been shaped by a wide range of depositional processes. These processes reflect the distribution of sediment, the characteristics of the receptacle basin, and the dynamics of depositional systems. As a result, a thick Miocene paralic sequence has formed, with abundant evidence of wave-dominated facies, indicating the probable presence of hydrocarbon reservoir potential.

Keywords: Facies, Meligan Formation, porosity, hydrocarbon

Topic: Marine Science