The role of advection and dispersion in the rock matrix on the transport of leaking CO2-saturated brine along a fractured zone
(English)Manuscript (preprint) (Other academic)
CO2 that is injected into a storage reservoir can leak in dissolved form because of brine displacement from the reservoir, which is caused by large-scale groundwater motion. Simulations of the reactive transport of leaking CO2aq along a conducting fracture in a clay-rich caprock are conducted to analyze the effect of various physical and geochemical processes. Whilst several modelling transport studies along rock fractures have considered diffusion as the only transport process in the surrounding rock matrix (diffusive transport), this study analyzes the combined role of advection and dispersion in the rock matrix in addition to diffusion (advection-dominated transport) on the migration of CO2aq along a leakage pathway and its conversion in geochemical reactions. A sensitivity analysis is performed to quantify the effect of fluid velocity and dispersivity. Variations in the porosity and permeability of the medium are observed in response to calcite dissolution and precipitation along the leakage pathway. We observe that advection and dispersion in the rock matrix play a significant role in the overall transport process. For the parameters that were used in this study, advection-dominated transport increased the leakage of CO2aq from the reservoir by nearly 305%, caused faster transport and increased the mass conversion of CO2aq in geochemical reactions along the transport pathway by approximately 12.20% compared to diffusive transport.
Reactive transport, Advection dominated transport, Diffusive transport, CO2-saturated brine leakage, Transport in fractures, Rock matrix, Calcite kinetic reaction
Mineral and Mine Engineering
Research subject Civil and Architectural Engineering; Chemical Engineering; Applied and Computational Mathematics; Land and Water Resources Engineering
IdentifiersURN: urn:nbn:se:kth:diva-184616OAI: oai:DiVA.org:kth-184616DiVA: diva2:916390
This manuscript is under review in the journal of Advances in Water Resources. The main funder for this study has been “Higher Education Commission (HEC) of Pakistan”. The study was also partly supported by Lars Erik Lundberg Scholarship Foundation, Sweden.2016-04-012016-04-012016-04-04Bibliographically approved