CO2 Sequestration in the Arbuckle Group: Flow Simulation in Osage County, Oklahoma

Abstract

Abstract This paper provides a valuable foundation for the potential establishment of a carbon dioxide (CO2) sequestration project in Osage County, Oklahoma. Given the current global climate crisis and the resultant efforts to reduce atmospheric CO2 levels, these types of initiatives are expected to increase in frequency and scale. This study focuses on the Arbuckle Group, a saline aquifer and carbonate rocks that has been identified as a potential large-scale CO2 storage reservoir in a previous publication by Milad et al. (2023). A 3D geological model was constructed integrating core and well log data, allowing for the estimation of stratigraphic and petrophysical properties of the Arbuckle Group in Osage County. A 30-year injection period of over 50 million metric tons of CO2 was then simulated, incorporating the permeabilities and porosities from the geological model. This process involved building a compositional simulation model with one injection well, with the formation divided into 10 layers and injections occurring in the bottom four. These layers were chosen based on the depth of existing injection wells, as well as the existence of natural fractures that enhance the permeability distribution, thus supporting large-scale CO2 injection at low pressure. A subsequent 50-year post-injection study was also conducted to monitor pressure buildup and CO2 plume evolution. The formation was found to have an average porosity of 6%, variable permeability distribution, and an average reservoir thickness of about 940 ft. These properties make the Arbuckle saline aquifer an ideal candidate for CO2 sequestration, with ample storage capacity. We discovered significant potential for large-scale CO2 sequestration, owing to the natural fractures in the Arbuckle's lower section, and determined that a single well could feasibly store tens of millions of metric tons of CO2. This capacity could be significantly augmented by increasing the number of injection wells. We observed a positive correlation between the formation's permeability, particularly in the lower Arbuckle, and the volume of CO2 that can be stored. The study confirms the potential feasibility of safe and efficient carbon sequestration in the formation, with potentially minimal risks risking fracture or contamination of underground potable water sources, particularly if CO2 is injected deep in the formation. The less permeable upper Arbuckle, ranging from 0.0001mD to 2.5mD, could offer an additional protective layer. The dominant CO2 trapping mechanism was structural trapping in 3 of 4 simulation cases considered, with an increase in residual trapping at the end of the injection period. The results of this study can serve as a valuable resource in the potential deployment of CO2 injection in the Arbuckle Group. Moreover, this study could aid decision making during field development in this formation and contribute to efforts to promote a sustainable future.