The role of advection and dispersion in the rock matrix on the transport of leaking CO2-saturated brine along a fractured zone

Abstract

CO 2 that is injected into a storage reservoir can leak in dissolved form because of 18 brine displacement from the reservoir, which is caused by large-scale groundwater motion. 19Simulations of the reactive transport of leaking CO 2aq along a conducting fracture in a clay-20rich caprock are conducted to analyze the effect of various physical and geochemical 21 processes. Whilst several modelling transport studies along rock fractures have considered 22 diffusion as the only transport process in the surrounding rock matrix (diffusive transport), 23 this study analyzes the combined role of advection and dispersion in the rock matrix in 24 addition to diffusion (advection-dominated transport) on the migration of CO 2aq along a 25 leakage pathway and its conversion in geochemical reactions. A sensitivity analysis is 26 performed to quantify the effect of fluid velocity and dispersivity. Variations in the porosity 27 and permeability of the medium are observed in response to calcite dissolution and 28 precipitation along the leakage pathway. We observe that advection and dispersion in the rock 29 matrix play a significant role in the overall transport process. For the parameters that were 30 used in this study, advection-dominated transport increased the leakage of CO 2aq from the 31 reservoir by nearly 305%, caused faster transport and increased the mass conversion of CO 2aq 32 in geochemical reactions along the transport pathway by approximately 12.20% compared to 33 diffusive transport. 34 2

Convective‐Reactive CO2 Dissolution in Aquifers With Mass Transfer With Immobile Water

“…Elsewhere, other values have been used. Pau et al () and Farajzadeh et al () used 2 × 10 −9 m 2 ·s −1 , and Ahmad et al () used 3 × 10 −9 m 2 ·s −1 . The absolute permeability K is set to 4 × 10 −13 m 2 , total porosity ϕ is 0.2, viscosity μ is 1 × 10 −3 kg·m −1 ·s −1 , acceleration due to gravity g is 9.8 m·s −2 , and the initial density ρ O is 1,000 kg·m −3 .…”

“…Based on the calculations of mineral reactive surface area of Ahmad et al (), section 2.5, the initial mineral reactive surface area values are 3.52 and 38.67 m 2 /(kg water) in the fracture and rock matrix, for a clay‐rich caprock. Therefore, we assume a v , m = 0.1 a v , im .…”

Parameter Estimation on Two-Dimensional Advection-Dispersion Model of Biological Oxygen Demand in Facultative Waste Water Stabilization Pond: Case Study at Sewon Wastewater Treatment Facility

“…There were many pieces of researches conducted to solve and to apply the advection-dispersion model. For examples, an advectiondispersion rule was applied for analyzing of transport of leaking CO2-saturated brine along a fractured zone [8], a fractional advection-dispersion model was applied for hillslope tracer analysis, and a 3D advection-dispersion model was used to analyze the distribution of dissolved oxygen in a facultative pond [9]. The analytical solution of a partial differential equation is commonly not easy to find.…”