Abstract

AbstractCO2 geological sequestration has been proposed as a climate change mitigation strategy that can contribute towards meeting the Paris Agreement. A key process on which successful injection of CO2 into deep saline aquifer relies on is the dissolution of CO2 in brine. CO2 dissolution improves storage security and reduces risk of leakage by (i) removing the CO2 from a highly mobile fluid phase and (ii) triggering gravity-induced convective instability which accelerates the downward migration of dissolved CO2. Our understanding of CO2 density-driven convection in geologic media is limited. Studies on transient convective instability are mostly in homogeneous systems or in systems with heterogeneity in the form of random permeability distribution or dispersed impermeable barriers. However, layering which exist naturally in sedimentary geological formations has not received much research attention on transient convection. Therefore, we investigate the role of layering on the onset time of convective instability and on the flow pattern beyond the onset time during CO2 storage. We find that while layering has no significant effect on the onset time, it has an impact on the CO2 flux. Our findings suggest that detailed reservoir characterisation is required to forecast the ability of a formation to sequester CO2.

Highlights

  • The behaviour of CO2 in a brine-saturated porous medium during CO2 geological storage involves several processes

  • ∂u + ∂v = 0 (1.1) ∂x ∂z u = − k ∂p (1.2) μ ∂x. This problem of density driven convection in a brine saturated porous medium is modelled in single phase comprising the flow of brine and the transport of CO2 dissolved in brine

  • We investigate the effect of the layered heterogeneity on the onset time of convective instability and on the subsequent flow pattern

Read more

Summary

Introduction

The behaviour of CO2 in a brine-saturated porous medium during CO2 geological storage involves several processes. (structural trap), the imbibing resident fluid can cut-off and immobilize trailing CO2 plume within formation pores (residual trap), the dissolution of CO2 in resident fluid removes CO2 from a highly mobile phase (solubility trap), and the reaction of CO2 saturated brine with formation rock securely stores CO2 (mineralization trap). CO2 dissolution rate, which measures solubility trapping, has been estimated for Sleipner field in Norway [6] while downwelling convective fingers are visually observed in experimental studies on convection in Hele-Shaw cells [7]. Previous studies of convection in homogeneous systems use the onset time when the instability commences and the critical wavelength of the convective fingers to characterise convection [2, 3]. The flow pattern after the onset time can be described in several regimes: diffusive, flux growth when the convective instabilities grow, constant flux when the fingers progress towards the bottom of the domain, and final period (when flux gradually declines) [4]. We use numerical simulations with perturbations from numerical artefacts to show that layered systems can alter CO2 flux beyond the onset time

Governing Equations and Model
Numerical Simulations
Results and Discussion
Conclusions
Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call