Injection of CO2‑Saturated Water through a Siliceous Sandstone Plug from the Hontomin Test Site (Spain): Experiment and Modeling

• Published in: Environmental science & technology 2013-01, Vol.47 (1), p.159-167
• Main Authors: Canal, J, Delgado, J, Falcón, I, Yang, Q, Juncosa, R, Barrientos, V
• Format: Article
• Language: English
• Subjects: Carbon Dioxide - chemistry; Carbon Sequestration; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; Minerals - chemistry; Models, Theoretical; Spain; Water - chemistry
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es3012222

Massive chemical reactions are not expected when injecting CO2 in siliceous sandstone reservoirs, but their performance can be challenged by small-scale reactions and other processes affecting their transport properties. We have conducted a core flooding test with a quartzarenite plug of Lower Cretaceous age representative of the secondary reservoir of the Hontomín test site. The sample, confined at high pressure, was successively injected with DIW and CO2-saturated DIW for 49 days while monitoring geophysical, chemical, and hydrodynamic parameters. The plug experienced little change, without evidence of secondary carbonation. However, permeability increased by a factor of 4 (0.022–0.085 mD), and the V P/V S ratio, whose change is related with microcracking, rose from ∼1.68 to ∼1.8. Porosity also increased (7.33–8.1%) from the beginning to the end of the experiment. Fluid/rock reactions were modeled with PHREEQC-2, and they are dominated by the dissolution of Mg-calcite. Mass balances show that ∼4% of the initial carbonate was consumed. The results suggest that mineral dissolution and microcracking may have acted in a synergistic way at the beginning of the acidic flooding. However, dissolution processes concentrated in pore throats can better explain the permeability enhancement observed over longer periods of time.