Performance Evaluation of an Inter-Well CO2 Injection Test in the Sukowati Field in Indonesia

Abstract An inter-well CO2 injection field test was conducted in the Sukowati field, a mature onshore field in Indonesia. The objective of the field test was to evaluate the efficiency of CO2 enhanced oil recovery (EOR) in the main carbonate reservoir of the Sukowati field, where the reservoir pressure is below the minimum miscibility pressure for CO2 but remains within near-miscible conditions. The field test was performed using existing wells in the field. A total of 2,600 tonnes of high purity CO2 were transported from the industrial gas sources via trucks and injected from an injection well which was surrounded by three primary monitoring producers. Various monitoring techniques, including real-time downhole pressure and temperature monitoring, saturation logging, gas tracers, and production testing, were used to evaluate the effectiveness of the test and to address key uncertainties prior to full field application. In addition, a reservoir simulation study was also performed to provide an integrated interpretation of the observed data. This paper presents the results of the field tests and an evaluation through the reservoir simulation study. The test results show a significant increase in oil production, a decrease in water cut, and tracer breakthrough at the primary monitoring producers. The simulation study validated the observed performance and indicated that highly efficient oil displacement was achieved by the CO2 injection. The study identified key parameters and investigated their impact on the CO2 EOR performance. The paper also discusses the challenges and key lessons learned throughout the project. In the Southeast Asia region, many oil fields have reservoir pressures below the minimum miscibility pressure due to high geothermal gradients in the region and/or relatively shallow reservoir depths. The results and insights from this field test provide valuable guidance for future CO2 EOR projects in the region.