Optimizing CO2 storage in deep saline formations: a comprehensive review of enhancing pore space utilization through simultaneous or alternate aquifer injection

Stella I. Eyitayo, Nachiket Arbad, Oladoyin Kolawole, Marshall C. Watson

Research output: Contribution to journalReview articlepeer-review

1 Scopus citations


Deep Saline Formations (DSFs) are increasingly recognized for their significant role in geological carbon dioxide (CO2) storage, a crucial part of Carbon Capture and Storage (CCS) strategies aimed at mitigating climate change. Nevertheless, formation overpressure, capillary breakthrough pressure, and injectivity impairment often compromise the actual CO2 Storage Efficiency (CSE) in these formations, potentially reducing storage efficiency by up to 22%. However, comprehensive knowledge of Pore Space Utilization (PSU) in CO2 storage in deep saline formation must be improved to address this inefficiency. This study presents a first-of-its-kind work combining a comprehensive review with a proposed innovative concept on the viability and effectiveness of the Simultaneous or Alternate Aquifer Injection (SAI) method to enhance CO2 storage within DSFs. Further, a conceptual future direction for optimizing CO2 storage in deep saline formations was proposed. We introduced the Simultaneous or Alternate Aquifer Injection (SAI) as a useful approach to optimizing PSU and CSE in DSFs. This method is similar in principle to Water Alternating Gas (WAG) used in CO2-EOR. While there is a lack of data on the SAI process, WAG data shows that incremental CO2 is stored in a reservoir when water is introduced in a CO2-EOR, thereby increasing the oil recovery and CO2 storage. This incremental ranges from 3–100% CO2 stored in a formation. The SAI method can enhance CSE by approximately 25% on average compared to traditional injection methods when using this as an analog. Our study further highlights the complexities of the SAI method and its potential to enhance storage efficiency and capacity, which is crucial for large-scale CCS implementation. We compared various trapping mechanisms, their impacts on CSE, and how they can be potentially augmented through the SAI to increase PSU in saline aquifers to mitigate climate change. The SAI method, involving simultaneous or alternate injection of CO2 and brine, may yield a novel approach to managing the movement of the CO2 plume in the aquifer reservoir, thereby maximizing storage efficiency and minimizing leakage risks. While our review of the SAI method shows promise, it still poses technical, regulatory, and economic challenges. Our review findings emphasize the need for more integrated dynamic modeling, numerical simulations, and sensitivity analyses for successful implementation. With adequate experimental and simulation support, the SAI approach has the potential to revolutionize CO2 storage operations in DSFs, contributing significantly to global net-zero carbon emission goals.

Original languageEnglish (US)
Pages (from-to)6513-6536
Number of pages24
JournalEnergy Sources, Part A: Recovery, Utilization and Environmental Effects
Issue number1
StatePublished - 2024

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Nuclear Energy and Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology


  • CO storage efficiency
  • deep saline aquifers
  • geologic carbon storage
  • pore space utilization
  • simultaneous or alternate aquifer injection


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