A Sustainable Approach to Decision-Making in CCUS Systems

This study proposes a methodology for operational decision-making leading to the sustainability CO2-EOR systems. The methodology is a simple, yet comprehensive, integration of environmental and economic carbon capture, utilization and storage (CCUS) performance. Understanding the interplay between the environmental and economic conditions allows the EOR operator to manage the CO2-EOR flood so it remains within the limits of carbon balance neutrality and favorable economics under given prices and costs. The environmental performance and the main operational inputs (fluid production, CO2 injection, and purchase requirements) were taken from a dynamic carbon Life Cycle Assessment (LCA) study previously performed for a CO2-EOR site in Cranfield, Mississippi. The LCA study accounts for greenhouse gases (GHG) emissions within a gate-to-grave CCUS system boundary, considering four different CO2 injection strategies and four gas separation processes.The economic performance assessment was made through a marginalist analysis (Marginalist Production Theory), which determines important technical and economic relations through basic differential calculus derived from production, cost, and income functions. This method allows to define the operational economic optimum (optimum profit). The assessment considers four CO2 price scenarios and uses World Bank estimated oil prices. In a first step of the proposed methodology, environmental limits of the operation are estimated. These limits are then compared with operative maximum productivity as well as with the economic optimum. According to the methodology, the EOR operation is sustainable as long as the environmental optimum is greater, or lasts longer, than the economic optimum along the project’s life. Results show that for this operation and assumed parameters, CO2-EOR could be classified as a sustainable activity depending on the operator’s strategic decision-making. In the case study, all injection strategies reach the environmental optimum after maximum productivity is reached. However, only two strategies (continuous gas injection and water alternating gas) find their economic optimum within the environmental limits, fulfilling the defined necessary and sufficient condition for CCUS sustainability