Modeling of transient evolution of uplift and subsidence during CO2 storage operation at In Salah, Algeria
Abstract
The Krechba gas field, at In Salah Algeria is currently utilized for a large CO2 storage demonstration project. In the last 6 years, 0.5 to 1.0 million tons of CO2 per year have been injected, through a horizontal well, into a 20 m thick storage formation with a relatively low permeability. The injected mass of carbon dioxide at one of the injection wells (KB-502) produces a measurable ground displacement of about 5 mm/yr. A double-lobe uplift pattern has been observed at KB-502 through satellite based measurements, and both semi-analytical inverse deformation analysis (Vasco et al., 2010) and coupled numerical modeling of fluid flow and geomechanics (Rutqvist et al., 2011) have shown that this pattern of displacement can be explained by injection-induced deformation in a deep vertical fracture zone of fault (few hundred meters up to a depth below 1600 m) intersecting the well of injection. The presence of such a fault has been also confirmed by recent 3D seismic survey (Gibson-Poole et al., 2010). Here we present modeling results of forward analysis using the coupled fluid flow and geomechanical simulator TOUGH-FLAC (Rutqvist et al. 2002). Starting from the results obtained by Rutqvist et al. (2011), here we implement a new, finer meshgrid within a larger domain (20 by 20 km, centered at the horizontal well) to account for a detailed analysis of deformation in the fault region and of the double-lobe uplift. Earlier model describes the deformation at In Salah using an overall average rate of injection. Here we studied the transient evolution of uplift and subsidence using the observed injection rate. Evolution has been analyzed for both the case of fracturing and opening at the fault with the aim of explaining any field observations. Effects of irreversible permeability increase during the re-injection have been also studied.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H33B1306R
- Keywords:
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- 1822 HYDROLOGY / Geomechanics;
- 1847 HYDROLOGY / Modeling