Towards Low Carbon Oil – A Comprehensive Portfolio Analysis for CO2 EOR/CCUS Opportunities in Oil Reservoirs in the Sultanate of Oman

Abstract

Abstract It is evident that there is an urgent need to lower the Green-House-Gas (GHG) emissions in all industrial sectors, including oil and gas. One of the solutions to produce low-carbon oil is the utilization of CO2 for Enhanced Oil Recovery. Injection of CO2 for EOR leads to retention of a considerable amount of the injected CO2 in the reservoir, which ultimately results in CO2 storage. Therefore, in efforts of Petroleum Development Oman Company (PDO) to lower GHG from its own operations and produce low-carbon oil, a portfolio review study was conducted to identify, assess, and rank the candidate fields for CO2 EOR. This paper describes the workflow and outcome of this portfolio analysis of oil reservoirs in PDO's portfolio. First, all the oil fields were screened to identify the technically feasible fields for gas EOR. Second, the best injection strategy was selected for each field based on the reservoir and fluid properties. Third, incremental oil recovery for each field was estimated using analytical methods. Fourth, net CO2 utilization was estimated as potential storage capacity for all the candidates. Finally, high level economic screening in terms of the unit technical cost (UTC) was performed for each field to rank the different opportunities considering the facilities and wells requirements for gas EOR. Different injection strategies were considered in this study including water-alternating-gas (WAG) and continuous-gas-injection (CGI), at immiscible or miscible conditions. The modified Koval method was used to generate type curves for each injection strategy and different reservoir heterogeneities. Based on these type curves and the optimized pore volume injected, the incremental oil recovery was estimated for each field. The net utilization amount of CO2 was estimated based on the net utilization factor from industry experience, hence the storage capacity of each field was calculated. CO2 EOR development concept was established to enable the calculation of the UTC of the different opportunities. The outcome of this portfolio analysis shows that many fields could be potential candidates for WAG and CGI. Some of the fields show attractive UTC with the capacity to store more than 1 Mtpa of CO2. Moreover, the UTCs of most CGI projects are more economically attractive than WAG projects due to the higher incremental oil by secondary CGI. The CO2 price, including the capture and transportation costs, is a major component of the overall cost of CO2 EOR. Furthermore, the concept of enriching CO2 to lower MMP and enable miscible flood is more commercial than injecting pure CO2 under immiscible conditions. Additionally, the paper provides a detailed fit-for-purpose approach to screen and rank oil fields for CO2 EOR. It also gives insights on selecting and optimizing the CO2 injection strategy for EOR.

Topics & Concepts