Formation uplift analysis during geological CO₂-Storage using the Gaussian pressure transient method: Krechba (Algeria) validation and South Korean case studies

The Paris Climate Agreement of 2015, along with the commitments in the South Korean 2050 Carbon-Neutral Scenario, highlights the importance of carbon capture and storage (CCS) to counter advancing global warming. During CCS, carbon-dioxide enriched fluid is injected into a geological formation, which causes pore pressure increases. The CCS must occur safe and stable, which requires geomechanical modeling to analyze the effects of formation uplift and subsidence. In this study, surface uplift and subsidence were predicted with a recently developed Gaussian pressure transient (GPT) method, in advance of the anticipated CO₂-injection schemes to ensure a secure storage process. The GPT-results were first validated against field observations obtained from the In Salah CCS-site (Algeria). Next, the GPT-method was applied to two potential CCS target locations in South Korea: (1) the Pohang basin, and (2) the Donghae gas reservoir. Maximum uplifts of 25.42 and 32.55 mm, respectively, were estimated for each location. In addition, the effect of installing a relief well to mitigate the uplift was studied. Subsidence was estimated around the relief well due to production. The presence of the relief well aided the mitigation of both uplift and subsidence. Our study shows that preliminary analysis of uplift and subsidence of potential CCS-sites is possible with the GPT-method. In addition, it was shown that installing (one or more) relief well(s) for the purpose of mitigating the severe uplift caused by injection is feasible.