Geomechanical Evaluation of CO₂ Storage in a Coal Seam with a Secondary Barrier

Geomechanical evaluation of CO₂ underground disposal is complex and can be even more challenging in coal reservoirs due to natural fractures and combined effects of multi-component transport. The objective of the research work presented in this paper is to investigate the geomechanical response of the geologic system due to large-scale CO₂ injection in a targeted coal reservoir. Field-scale geomechanical models were constructed to capture overall geologic response at an active site due to injection, and the results were compared with long-term field monitoring work. Coupled multiphase fluid flow and geomechanical models developed for the project site are capable to understand the CO₂ transport behavior within the targeted reservoir and geologic layers above the targeted reservoir. Additionally, modeling efforts were carried out to investigate CO₂ transport behavior and geomechanical response, if CO₂ were to break through the seal layer into overburden formations. The combined results of geomechanical modeling and tiltmeter monitoring provide useful information on the migration of CO₂. Modeling results show that a secondary coal seam above the targeted coal reservoir could potentially acts as a barrier in the presence of a CO₂ leakage.