Impact of Chemical and Mechanical Processes on Leakage from Damaged Wells in CO₂ Storage Sites

Abstract

The perceived risk of CO2 leakage through wells has been considered a potential limitation to commercial scale deployment of geologic CO2 storage. However, chemical and mechanical alteration of cement can reduce the permeability of leakage pathways. We conducted 100s of simulations spanning realistic operating conditions and well-damage characteristics to understand (1) under what conditions and time frames do fractures seal and (2) for fractures that do not seal, how quickly and to what extent is the permeability reduced. For the conditions simulated, fractures with apertures in the tens of microns seal while those greater than hundreds of microns may exhibit long-term leakage. Fractures with apertures between 10 and 500 μm took a few days to a couple of years to seal. For non-sealing fractures mechanical deformation of altered asperities can rapidly reduce permeability. A sealing criterion was developed to relate fracture aperture with the cemented length required for self-sealing. Longer cemented intervals can seal large fractures; however, they take longer to seal and leak larger volumes before sealing. While the results presented here are subject to uncertainties, the manuscript provides a framework in which a model can be used to quantitatively answer questions regarding well integrity to facilitate decision making.

Chemical‐Mechanical Impacts of CO2 Intrusion Into Heterogeneous Caprock

“…Research on long-term coupled chemical-mechanical simulations in the caprock is very recent, with emphasis on coupled processes in GCS reservoirs and wellbores (Carroll et al, 2017;Iyer et al, 2020;R. Zhang et al, 2016).…”

“…Research on long‐term coupled chemical‐mechanical simulations in the caprock is very recent, with emphasis on coupled processes in GCS reservoirs and wellbores (Carroll et al, 2017; Iyer et al, 2020; R. Zhang et al, 2016). A limited number of experimental studies assess coupled chemical‐mechanical behavior of caprock with CO 2 intrusion (Bakker et al, 2019; Ilgen et al, 2018; Spokas et al, 2018; Y. Zhang et al, 2019).…”