Reactive Transport Modelling for Chemical Engineering and Environmental Science Applications Across Different Scales

Abstract

Reactive transport in porous media is ubiquitous in nature and industry, with applications ranging from geothermal energy, enhanced oil recovery, soil contamination, to carbon storage, etc. A long-lasting issue in this field is reactive transport parametrizations and linking the experimental data to continuum-scale models. For this purpose, pore-scale modelling can be used as a valuable tool for upscaling purposes to decrease the existing uncertainties. In this thesis, we performed reactive transport modelling across different scales, namely pore-scale and continuum-scale for different applications of geothermal energy, low salinity waterflooding and CO2 convective mixing during carbon storage in saline aquifers. Moreover, we have experimentally studied solute transport upscaling from pore- to REV-scale. Using coupling PHREEQC geochemical module and pore-network modelling under single-phase condition, we showed how averaging over the domain to predict mineral reaction rates can lead to erroneous results, in some cases even the dominant reaction path (dissolution/precipitation) could not be determined accurately. We have also coupled oil-brine and rock-brine (sandstone) surface complexation models with multicomponent solute transport under the steady-state two-phase quasi-static condition in pore network to study the effect of hydrodynamic condition on low salinity effect. We showed that under two-phase condition the advancing fluid is divided into two flowing and stagnant zones. The contribution of stagnant zones at different injection fluid saturation can cause a delay in the low salinity effect in the continuum-scale as the low salinity water penetration in these zones is diffusion-controlled. Moreover, we experimentally showed that upscaling the solute transport from pore-scale to REV-scale depends on the process (i.e., solute loading or unloading scenarios). The unloading process usually results in a higher dispersion coefficient, while the difference diminishes in high injection flow rates. Using continuum-scale reactive transport modelling, we have studied the role of geochemistry on CO2 convective mixing during carbon storage in saline aquifers. Firstly, we investigated the signature of geochemical interactions on the process in sandstone aquifers. We coupled a representative set of fluid-fluid and sandstone-fluid reactions with an in-house convection-diffusion transport model and showed that geochemical interplay can result in earlier onset of convection and higher total stored carbon due to mineralization mechanism. We highlighted how CO2 storage may change the mineralogy of the sandstone aquifers. Next, we looked into the dynamics of the convective mixing and how the hydrodynamic dispersion and geochemistry can change it over a wide range of Rayleigh numbers. We showed that ignoring the geochemical interactions in carbonate aquifers can lead to underestimation of stored CO2 into the simulation domain. Lastly, we revisited the convective mixing scaling relations and showed how they can be modified to take into account the effects of hydrodynamic dispersion, permeability anisotropy and geochemistry. The results of these studies provide a broad perspective on how geochemistry can contribute to a wide range of environmental and chemical engineering applications. We have shown how pore-scale reactive transport simulations can work as a bridge to upscale the experimental data related to reaction rates, to be fed into the continuum-scale models. We have also investigated the crucial importance of geochemistry on solutal convective mixing in the porous media, which provided important implications for field-scale CO2 storage.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Constantinos Theodoropoulos (Supervisor) & Vahid Joekar-Niasar (Supervisor)