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Application of Tough2/ewasg to the Modelling of Salt Water Injection into a Depleted Geothermal Reservoir: Preliminary Results.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Calore, C. Battistelli, Alfredo Cnr, Ricerca |
| Copyright Year | 2003 |
| Abstract | The TOUGH2/EWASG code is being applied to a numerical study of salt water injection into depleted vapour-dominated geothermal reservoirs. Our study investigates whether the injection of water with a sodium chloride content of 3.3% by weight (similar to that of seawater) for periods of 30 years would lead to conditions of permanent reduction of reservoir permeability, with the consequent negative effects on the recovery of injected fluid as steam. We neglect the effects of water-rock interactions and, in particular, the precipitation of mineral species other than halite, as these are not handled by EWASG. A few test cases were run to investigate the ability of the EWASG V.4 module to solve this type of problem. Numerical experiments have been performed using two-dimensional radial, homogeneous and isotropic porous medium systems with a radius and height of 2 km. Initial conditions were assumed similar to those of some depleted zones of the Larderello and The Geysers reservoirs, which, neglecting the effects of vapour pressure lowering in our models, correspond to single -gas phase conditions. The simulated injection time was 30 years. In this paper we present the preliminary results of one of these models, in which halite precipitation occurs at the vaporization front, and is then followed by dissolution processes taking place when liquid conditions with lower salinity prevail, because of the advancement of the injection plume. Reduction in permeability or sealing of the formation occurs where the injection plume stops propagating, with boiling at its front. Thus, stopping injection would lead to the extension of the zones of the reservoir with reduced permeability or sealed formation all along its final vaporization area. In the model discussed here and throughout the simulated time, there are apparently no evident, negative effects on the recovery of injected brine as steam, because the plume can propagate more or less as if there were no precipitation processes, with about 85% of the injected brine vaporized throughout the simulated 30 years of injection. The results obtained so far have demonstrated the efficacy of the EWASG V.4 module in simulating complex phenomena of coupled mass and heat transport in geothermal reservoirs whose thermodynamic conditions are strongly affected by compositional processes. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://tough.lbl.gov/assets/files/02/documentation/proceedings/2003-CaloreBattistelli.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
