Simulation study on co2 enhanced oil recovery for offshore area in Thailand

Abstract

Fossil fuels are widely used all over the world. It generates carbon dioxide (CO2) which is one of the main causes for climate change and global warming. One practical technology to reduce CO2 emission is carbon capture, utilization, and storage (CCUS) which includes the use of CO2 for enhanced oil recovery (CO2EOR) and storage in the geological reservoir. In Thailand, there are some potential geological reservoirs for CO2EOR due to crude properties, depth of the reservoir and oil saturation, especially in the Gulf of Thailand. However, the high temperatures gradient in the Gulf of Thailand can lead to higher minimum miscibility pressure (MMP). Consequently, this study becomes partial CO2 miscible process. Previous studies on this issue in Thailand are rarely available and it becomes more difficult to determine appropriates parameters including injection rate and operating pressure for the CO2EOR processes. This study aims to evaluate the possibility of CO2EOR in the presuming light oil reservoir in the offshore area by applying the real data from the area, a 3-D heterogeneous reservoir model is created and used in the CO2EOR simulations. This study uses two CO2EOR technologies which are CO2 flooding and water alternating gas (WAG) within 24 years of production. The fracture pressure is calculated and considered to prevent the reservoir fracture whilst injecting displacing fluid. The two main parameters studied are the injection rate and operating pressure.

The results present that WAG method with the highest injection rate of both CO2 at 0.8 MMSCF/day and water at 500 STB/day as well as operating pressure at 90% of fracture pressure can produce oil with the highest recovery factor at 48.1% and total oil production at 550,497 STB. However, the highest total oil production comes with the high amount of produced water. On the other hands, CO2 flooding with the highest CO2 injection rate at 0.8 MMSCF/day and the highest operating pressure at 90% of fracture pressure produces oil with lower recovery factor at 43.1% and total oil production at 492,893 STB but the produced water declines along with the production rate. Lastly, although this study area has high temperature which causes the process to be partially CO2 miscible, the results of the study can contribute to utilize CO2 from the source for more oil production and to store carbon for the potential site to reach Thailand's carbon neutrality in the future.