Evaluation of Potential of CO2-Enhanced Oil Recovery (EOR) and Assessment of Capacity for Geological Storage in a Mature Oil Reservoir within Upper Assam Basin, India

After over seven decades of production, most reservoirs in the Upper Assam Sedimentary Basin, India, have reached intermediate or late development stages, rendering them suitable for the adoption of enhanced oil recovery (EOR) techniques. Lighter nature of crude oil and favorable mobility ratio in most of these reservoirs opens up avenues for assessment of CO2-EOR, which also offers the added benefit of carbon storage, aligning with global climate change mitigation efforts in addition to incremental oil production. This research aims to evaluate the viability of CO2-EOR and potential for permanent storage within the reservoir, as well as to conduct an in-depth analysis of various mechanisms. The subject reservoir ABC001 is located in the Upper Assam Basin, India, which meets the screening criteria for CO2-EOR evaluation. Various CO2injection strategies have been evaluated in this research, along with the effect of impurities and quantification of trapping mechanisms. The CO2-EOR has the potential to enhance recovery from the reservoir to 43.3%, compared to 39.3% from water flood. Even though the recovery is lesser (42.3%) than CO2injection, CO2water-alternating-gas (WAG) is projected to result in the greatest retention of CO2within the reservoir. A total of 306.7 MM m3and 153.4 MM m3of CO2is injected into the reservoir corresponding to CO2injection and CO2WAG scenarios, out of which around 194.9 MM m3and 68.4 MM m3are produced, leaving behind around 36.5% and 55.4% of CO2in the reservoir, respectively. The CO2-EOR and storage studies conducted in this project will enhance the learning curve, facilitating the development of a knowledge base that can be utilized to broaden CCUS initiatives in India.