Malaysia oilfield especially in Malay basin has currently show sign of maturity phase which involving high water-cut and also pressure declining. In recent event, Malaysia through Petroliam Nasional Berhad (PETRONAS) will be first implemented an enhanced oil recovery (EOR) project at the Tapis oilfield and is scheduled to start operations in 2014. In this project, techniques utilizing water-alternating-gas (WAG) injection which is a type of gas flooding method in EOR are expected to improve oil recovery to the field. However, application of gas flooding in EOR process has a few flaws which including poor sweep efficiency due to high mobility ratio of oil and gas that promotes an early breakthrough. Therefore, a concept of carbonated water injection (CWI) in which utilizing CO2, has ability to dissolve in water prior to injection was applied. This study is carried out to assess the suitability of CWI to be implemented in improving oil recovery in simulated sandstone reservoir. A series of displacement test to investigate the range of recovery improvement at different CO2 concentrations was carried out with different recovery mode stages. Wettability alteration properties of CWI also become one of the focuses of the study. The outcome of this study has shown a promising result in recovered residual oil by alternating the wettability characteristic of porous media becomes more water-wet.
Experimental and numerical evaluation of the potential of improving oil recovery from shale plugs by nitrogen gas flooding