| dc.description.abstract | Climate change induced global warming is a major issue facing the planet, as increased levels of Carbon Dioxide (CO2) and other potent greenhouse gases been released in the atmosphere have resulted in the rapid rise in sea levels and the frequent occurrence of abnormal weather conditions. This urgent problem calls for immediate action to be taken, and one of the most effective solutions to this issue is finding ways for taking out of circulation and reducing the levels of greenhouse gas emission from industrial processes. As a result, significant attention is nowadays been given by the petroleum industry to research focused on the potential of the broader application of CO2 injection for Enhanced Oil Recovery (EOR), and its long-term storage by means of sequestration in geological formations deep beneath the Earth as a means to help save the planet.
This thesis work presents a comprehensive study of CO2 injection for EOR purposes, a detailed literature review and a compositional simulation study. Based on previous work done and published in various literature on this topic, CO2 injection as an EOR method can aid in the recovery of additional oil from reservoirs by means of reservoir pressure maintenance, oil swelling, reduction of oil viscosity and density, as well as the vaporisation of the hydrocarbons present in reservoir oil.
For the implementation of the study presented in thesis, a synthetic 3-Dimensional reservoir model was used to implement water, continuous CO2 and Water-Alternating Gas (WAG) injection compositional simulations using ECLIPSE 300 module of the ECLIPSE reservoir simulator for the sole purpose of examining the effect of CO2 injection on improving the recovery factor and cumulative volume of oil production from the reservoir. Sensitivity simulations to test for the effect of different surface target rates for both the produced water and CO2 gas, and WAG cycle ratio were also performed.
Findings after the continuous injection of pure CO2 showed the best results with a 65% oil recovery factor when compared to the 55% obtained from the base case simulation involving only water injection. During the continuous injection of pure CO2 gas, oil production generally exhibits increasing trends with increasing CO2 injection rate and volume. The WAG injection case simulation results yielded a 62,3% recovery factor. Compared to other factors, the water injection rate during the WAG injection process creates the minimum influence on oil recovery and production. In the WAG injection process, oil recovery and cumulative production showed an increase with a cycle ratio of 1:2 for water and CO2 gas respectively. Additionally, observations made during the implementation of this work showed that increasing surface target rates for CO2 and water during the injection process proved to have no effect on the improvement of the oil recovery factor from the reservoir model. | |