Reservoir Characterization of Lahat Outcrop for the Application of Chemical Flooding in Air Benakat Sandstone Reservoir, Center of Sumatera

Abstract

The Enhanced Oil Recovery (EOR) method is a widely used for increasing oil recovery, one of which is by injecting ionic surfactants in sandstone reservoirs. The Sandstone Reservoir in Benakat Air Formation is composed of grains with dominant quartz, and cement with dominant calcite and silica. Brown clay (montmorillonite) fill in the rock matrix. The mineral montmorillonite is highly reactive to water, so that the sodium in montmorillonite will be hydrated with surfactant solution and result in swelling which can result in shrinking of the pore size of the rock and decrease the permeability so that the surfactant injection results are not optimum. Clay minerals and calcite have a positive surface charge at the fluid pH conditions in the reservoir so that it will affect the degree of adsorption and or precipitation of the anionic surfactant. Such adsorption and precipitation may affect the incremental oil recovery by injection of surfactant solution in the Sandstone reservoir, Air Benakat formation, either positively or negatively. Reservoir characterization has been done by examining the mineral content of sandstones reservoir on thin section. Two types of outcrops were analyzed in this study which consist of two thin section (L1 and L2). The mineral content of L1 outcrop consists of quartz, Potassium feldspar, plagioclase, gluconite and fossils, where matrix is composed of quartz, potassium feldspar and clay with dominant calcite cement. The L2 outcrop consists of grains filled with quartz, glauconite, plagioclase, biotite and fossil, where matrix is dominated by quartz and then clay, with calcite cement. The objectives of this study are to characterize the minerals contents in the sandstone core of Lahat outcrop for consideration of surfactant injection in Air Benakat Sandstone reservoir.