Techno-Economic Analysis of CO2 Storage in Depleted Oil and Gas Reservoirs, Saline Aquifers, and EOR
Authors: Enab Khaled , Alokla Kassem , Samak Ayman , Elizondo Thomas , Owusu-Peprah Nana Twum 
Published: September 2024

Abstract
Addressing climate change urgently requires effective carbon capture and storage (CCS) strategies to lower atmospheric carbon dioxide (CO2) levels. Depleted oil and gas reservoirs and saline aquifers are promising for CO2 geological sequestration due to their significant storage capacities. Furthermore, CO2 injection for Enhanced Oil Recovery (EOR) is a potential storage option for CO2 when CO2 flow back is controlled. Therefore, this study provides a techno-economic analysis to evaluate the feasibility, efficiency, and economic analysis of these different geological storage options for CO2 storage. The economic evaluations were conducted in compliance with Section 45Q tax credits for financial viability.
The analysis employs a multidisciplinary methodology combining geological assessments, engineering principles, and economic models. It focuses on the long-term impact of injecting CO2. Additionally, it evaluates supercritical CO2 behavior to estimate potential trapping mechanisms and identify factors affecting sequestration efficiency and safety. Economic analysis is central to this study, detailing the costs associated with CO2 capture, compression, transportation, injection, and monitoring. The study also considers the influence of policies, regulations, and market conditions on CCS project economics, identifying incentives and barriers.
The findings of this study affirm the potential of depleted oil and gas reservoirs and saline aquifers as viable CO2 storage solutions, offering a nuanced understanding of their role in global carbon mitigation efforts. The results show the economic superiority of the depleted oil and gas reservoirs in storing CO2 if the storage capacity is ignored (i.e., if all storing options are capable of storing the desired CO2 — 1 MM metric tons in this study).
The results highlight that storing CO2 in depleted oil and gas reservoirs exhibits the highest financial viability, particularly when used in conjunction with Direct Air Capture (DAC) technologies. These options demonstrate the greatest Net Present Values (NPVs), making them attractive for large-scale CO2 storage projects. Compliant DAC facilities, particularly those utilizing depleted oil and gas reservoirs, achieve NPVs upwards of $27 million, underscoring their economic superiority. While saline aquifers and EOR present viable options due to higher storing capacity, their financial performance is generally lower compared to depleted oil and gas reservoirs if uniform stored volume is considered. The study also notes the significant cost variations influenced by factors such as CO2 capture, transportation, and storage technologies, alongside the availability of financial incentives.
By outlining the challenges and opportunities, the study provides essential insights for stakeholders in CCS projects, suggesting a pathway through the complexities of CO2 sequestration towards sustainable climate action. Compliance with regulatory standards, particularly the Section 45Q tax credits, is emphasized as crucial for achieving positive financial outcomes and ensuring the success of CCS initiatives.