A caprock integrity assessment to optimize CO2 storage using coupled geomechanics: A case study of the Angostura Field
Adrian Ross*, David Alexander
Deep Resources Engineering. 2026, 3(3): 100252. 
doi.org10.1016j.deepre.2026.100252.pdf
Abstract: Long-term storage of carbon dioxide (CO2) in depleted hydrocarbon reservoirs or deep saline aquifers heavily depends on the sealing performance of the caprock. Therefore, it is crucial to evaluate the geomechanical integrity of the caprock since the injected CO2 can alter the stress regime acting on the rock, potentially leading to rock failure and loss of containment. In this study, we modelled the impact of changes in normal effective stress under a strike-slip stress regime. We tested the sealing performance of the caprock and a sealing shale located approximately 409 m below the caprock under various injection scenarios using the modified Barton-Bandis model. To accomplish this, we constructed a two-dimensional cross-sectional flow model of an offshore depleted gas reservoir and coupled it with the geomechanical module of the CMG-GEM compositional simulator. The primary focus of this research was to conceptually assess the operational and geomechanical parameters, along with the trapping mechanisms that could affect the sealing integrity of the caprock. Simulation results indicated that the caprock would not fail at injection rates below 4531 m3/d. However, only the lower sections of the sealing shale were fractured under the various injection scenarios. Over a simulation period of 1000 years, the average quantified CO2 leakage volumes for worst-case flux leakage scenarios were approximately 8137 m3 (3804,000 kg). Our sensitivity analysis for Young’s modulus and Poisson’s ratio of the caprock revealed that higher values of Poisson’s ratio led to increased lateral expansion. In contrast, a higher Young’s modulus resulted in the caprock fracturing more quickly at elevated injection rates. Results also showed that CO2 injection at lower rates significantly delayed the onset of rock failure. The evaluation of both residual and solubility trapping mechanisms produced similar results. Ultimately, both the caprock and the sealing shale are likely to fail due to shear stress rather than tensile stress. These preliminary results have important implications for evaluating and enhancing CO2 storage performance.
Highlights:
• Assessed caprock integrity for long-term CO2 storage under strike-slip stress regime.
• Developed a coupled 2D flow-geomechanical model using the modified Barton Bandis approach.
• Identified injection rates below 4531 m3/d as safe for caprock stability.
• Revealed shear-induced failure as the dominant mechanism in both caprock and sealing shale.
• Estimated worst case CO2 leakage at 8137 m3 (∼3.8 x 106 kg) over a 1000-year simulation period.
Keywords: Caprock integrity; Sealing performance; Barton-Bandis model; CO2 trapping mechanism
Cite: Ross, A.; Alexander, D., A caprock integrity assessment to optimize CO2 storage using coupled geomechanics: A case study of the Angostura Field, Deep Resources Engineering 2026, 3 (3), 100252. https://doi.org/10.1016/j.deepre.2026.100252
Citations: ……
