Semi-Analytical Solution to Assess CO2 Leakage in the Subsurface through Abandoned Wells
KAUST DepartmentEnergy Resources & Petroleum Engineering
Physical Science and Engineering (PSE) Division
Energy Resources and Petroleum Engineering Program
Ali I. Al-Naimi Petroleum Engineering Research Center (ANPERC)
Permanent link to this recordhttp://hdl.handle.net/10754/669047
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AbstractGeological carbon storage is an effective method capable of reducing carbon dioxide (CO2) emissions at significant scales. Subsurface reservoirs with sealing caprocks can provide long-term containment for the injected fluid. Nevertheless, CO2 leakage is a major concern. The presence of abandoned wells penetrating the reservoir caprock may cause leakage flow-paths for CO2 to the overburden. Assessment of time-varying leaky wells is a need. In this paper, we propose a new semi-analytical approach based on pressure-transient analysis to model the behavior of CO2 leakage and corresponding pressure distribution within the storage site and the overburden. Current methods assume instantaneous leakage of CO2 occurring with injection, which is not realistic. In this work, we employ the superposition in time and space to solve the diffusivity equation in 2D radial flow to approximate the transient pressure in the reservoirs. Fluid and rock compressibilities are taken into consideration, which allow calculating the breakthrough time and the leakage rate of CO2 to the overburden accurately. We use numerical simulations to verify the proposed time-dependent semi-analytical solution. The results show good agreement in both pressure and leakage rates. Sensitivity analysis is then conducted to assess different CO2 leakage scenarios to the overburden. The developed semi-analytical solution provides a new simple and practical approach to assess the potential of CO2 leakage outside the storage site. This approach is an alternative to numerical methods when detailed simulations are not feasible. Furthermore, the proposed solution can also be used to verify numerical codes, which often exhibit numerical artifacts.
CitationQiao, T., Hoteit, H., & Fahs, M. (2021). Semi-Analytical Solution to Assess CO2 Leakage in the Subsurface through Abandoned Wells. Energies, 14(9), 2452. doi:10.3390/en14092452
SponsorsThe authors thank Computer Modelling Group (CMG) Ltd. for providing the academic license of CMG simulators to the King Abdullah University of Science and Technology (KAUST).