The peridotite section of the Samail Ophiolite in the Sultanate of Oman offers insight into the feasibility of mineral carbonation for engineered, in situ geological CO 2 storage in mantle peridotites. Naturally occurring CO 2 sequestration via mineral carbonation is well-developed in the peridotite; however, the natural process captures and sequesters CO 2 too slowly to significantly impact the concentration of CO 2 in the atmosphere. A reaction path model was developed to simulate in situ CO 2 mineralization through carbonation of fresh peridotite, with its composition based on that of mantle peridotite in the Samail Ophiolite and including dissolution kinetics for primary minerals. The model employs a two-stage technique, beginning with an open system and progressing to three different closed system scenarios- a natural system at 30°C, an engineered CO 2 injection scenario at 30°C, and an engineered CO 2 injection scenario at 90°C. The natural system model reproduces measured aqueous solute concentrations in the target water, signifying the model is a close approximation of the natural process. Natural system model results suggest that the open system achieves steady state within a few decades, while the closed system may take up to 6,500years to reach observed fluid compositions. The model also identifies the supply of dissolved inorganic carbon as the limiting factor for natural CO 2 mineralization in the deep subsurface. Engineered system models indicate that injecting CO 2 at depth could enhance the rate of CO 2 mineralization by a factor of over 16,000. CO 2 injection could also increase mineralization efficiency - kilograms of CO 2 sequestered per kilogram of peridotite - by a factor of over 350. These model estimates do not include the effects of precipitation kinetics or changes in permeability and reactive surface area due to secondary mineral precipitation. Nonetheless, the faster rate of mineralization in the CO 2 injection models implies that enhanced in situ peridotite carbonation could be a significant sink for atmospheric CO 2.
Bibliographical noteFunding Information:
We would like to extend special thanks for their generosity to everyone at the Ministry of Regional Municipalities and Water Resources, Sultanate of Oman, particularly Salim Al Khanbashi and Dr. Abdulaziz Ali-AL-Mashikhi, and everyone at the Geological Survey of Oman and the Directorate General of Minerals in the Ministry of Commerce and Industry, particularly Dr. Ali Al Rajhi and Dr. Salim Al Busaidi. We thank Lisa Streit, Peter Canovas, Evelyn Mervine, and Alison Keimowitz for help during the 2009–2011 field seasons, and Martin Stute for advice in the lab. This work was supported through the NSF Graduate Research Fellowship Program , Columbia Research Initiative in Science and Engineering , Lamont-Doherty Earth Observatory , Petroleum Development Oman , NSF Research Grant MGG-1059175 , and Kelemen's Arthur D. Storke Chair at Columbia University . Kelemen's contribution was supported by NSF Research Grant EAR-1049905 and the Storke Chair.
- CO -water-rock interaction
- Geochemical modeling
- Geologic CO storage
- In situ CO mineralization
- Mineral carbonation