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Abstract

Carbon capture and storage is one of the technologies that could help reduce CO2 concentration in the atmosphere. Depleted oil and gas fields are favorable targets for CO2 storage because existing wells can be readily used as injection wells. Wellbore cement is very important in wellbore systems that serve as a barrier between different zones in the subsurface. The fractures inside wellbore cement sheath, one of the possible pathways for CO2 leakage to surface and/ or fresh water aquifers, impair the effective sealing of the wellbore cement. The existence of fractures poses a risk for Carbon capture and storage. The purpose of this experimental study is to examine the effect of CO2 saturated acidic brine on the behavior of cement fracture and porosity. Flow-through experiments were performed atmospheric and high pressure conditions, using CO2 saturated brine. Fracture widening was observed in CT images of the atmospheric pressure experiment. The atmospheric pressure experiment resulted in the reduction of porosity. The porosity reduction was caused by calcite deposition which was confirmed by mineralogical analysis and ESEM images. The alteration of density along the fracture was observed by Helical CT analysis. There were 2 mechanisms working simultaneously: leaching and precipitation (carbonation). Leaching resulted in an increase in porosity whereas carbonation resulted in a reduction of porosity. In a possible leakage scenario, acidic brine exposure may result in a variation on fracture aperture and porosity.

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/content/papers/10.3997/2214-4609-pdb.377.61
2011-05-11
2024-03-29
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http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.377.61
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