Swelling/ Extraction Test of Carbon Dioxide Injection on Dead Oil Field Structure X for Phase Behavior Study

Abstract

At present, most of Indonesia's oil field production has decreased significantly. Carbon dioxide (CO₂) is one of the EOR gas injection method that has been proven to improve oil recovery factor especially in sub-tropical countries such as America and Canada whose average reservoir has low temperature at the highest temperature range of 135^oF. On the other hand, Indonesia is a country with abundant sources of CO₂, especially from the oil and gas industry and the Steam Power Plant (PLTU) with fuel oil/ coal, has not been optimally utilized. In this study we studied the phase behavior of CO₂ injection effect on Indonesian oil which has a high average temperature reaching 275^oF (135^oC). Basically it is known that CO₂ is increasingly difficult to mix with oil at higher temperatures. If CO₂ is injected below the minimum miscible pressure (MMP) at the reservoir temperature, the oil recovery efficiency will decrease as the miscibility is not achieved. It is expected that the process of oil recovery may occur under conditions between immiscible and miscible processes. The CO₂ injection experiments were carried out on X field stock tank oil, which according to the EOR screening results were suitable using CO₂ EOR. The experiment was conducted using PERTAMINA’s Visual PVT & Swelling Test equipment on various of CO₂ injection and pressure on stock tank oil at 135^oC. The experimental results show the swelling of oil on various CO₂ injections and pressures but extraction has not been reached yet. This showed that only CO₂ is miscible into the oil phase and changes the properties of the oil. The miscibility process of CO₂ into the oil phase can decrease the viscosity of the oil, impacting on oil mobility to improve the oil recovery factor. However CO₂ is not able to extract the oil into the gas phase due to technical difficulties thus it may not be defined at this point.