Verification of TRANSPORT Simulation Environment coupling with PHREEQC for reactive transport modelling

Abstract

Abstract. Many types of geologic subsurface utilisation are associated with fluid and heat flow as well as simultaneously occurring chemical reactions. For that reason, reactive transport models are required to understand and reproduce the governing processes. In this regard, reactive transport codes must be highly flexible to cover a wide range of applications, while being applicable by users without extensive programming skills at the same time. In this context, we present an extension of the Open Source and Open Access TRANSPORT Simulation Environment, which has been coupled with the geochemical reaction module PHREEQC, and thus provides multiple new features that make it applicable to complex reactive transport problems in various geoscientific fields. Code readability is ensured by the applied high-level programming language Python which is relatively easy to learn compared to low-level programming languages such as C, C++ and FORTRAN. Thus, also users with limited software development knowledge can benefit from the presented simulation environment due to the low entry-level programming skill requirements. In the present study, common geochemical benchmarks are used to verify the numerical code implementation. Currently, the coupled simulator can be used to investigate 3D single-phase fluid and heat flow as well as multicomponent solute transport in porous media. In addition to that, a wide range of equilibrium and nonequilibrium reactions can be considered. Chemical feedback on fluid flow is provided by adapting porosity and permeability of the porous media as well as fluid properties. Thereby, users are in full control of the underlying functions in terms of fluid and rock equations of state, coupled geochemical modules used for reactive transport, dynamic boundary conditions and mass balance calculations. Both, the solution of the system of partial differential equations and the PHREEQC module, can be easily parallelised to increase computational efficiency. The benchmarks used in the present study include density-driven flow as well as advective, diffusive and dispersive reactive transport of solutes. Furthermore, porosity and permeability changes caused by kinetically controlled dissolution-precipitation reactions are considered to verify the main features of our reactive transport code. In future, the code implementation can be used to quantify processes encountered in different types of subsurface utilisation, such as water resource management as well as geothermal energy production, as well as geological energy, CO2 and nuclear waste storage.

Geographic Information System (GIS) as a basis for the next generation of hydrogeological models to manage the geothermal area Waiwera (New Zealand)

“…The SHEMAT model by Kühn and Stöfen (2005) was revisited and reworked to provide an updated, geospatially accurate and referenced 3D geological model of Waiwera. The new model, which implements geospatial data for the distribution of hydrogeological units at the surface, was suc-cessfully plugged into the numerical solver TRANSPORTSE (Kempka et al, 2022), in which coupled processes for fluid flow and heat transport were simulated. While five wells were successfully modelled, simulations revealed to re-assess the extent and geothermal relevance for three wells.…”

“…Code and data availability. The code is available via Kempka et al (2022). All input data is given within the paper.…”

“…The TRANSPORT Simulation Environment (TRANS-PORTSE) was used to carry out the numerical simulations in the present study to reproduce the models of Kühn and Stöfen (2005), because the previously used version of the SHEMAT software package (Clauser, 2003) is not maintained anymore and lacks features that support computational efficiency. TRANSPORTSE is a density-driven flow and transport simulator, considering convective and conductive heat as well as advective, diffusive and dispersive species transport (Kempka et al, 2022). The following model of Waiwera's geothermal field expands on the concept with the main components and mechanisms of heat and mass transport taking place in the hydrothermal reservoir underlying the township as illustrated above (Fig.…”

Geologic controls on the genesis of the Arctic permafrost and sub-permafrost methane hydrate-bearing system in the Beaufort–Mackenzie Delta

“…A framework of equations of state for equilibrium CH 4 hydrate formation and the reversible processes describing permafrost aggrading/degrading, i.e., water-freezing and ice-melting (Mottaghy and Rath, 2006), has been coupled with the open-source flow and transport simulator (TRANSPORTSE) developed by Kempka (2020) and verified for complex reactive transport problems (Kempka et al, 2022). This coupling was referred to as T plus H (TRANSPORTSE + Hydrate) in our previous studies (Li et al, 2022a;.…”

Numerical Analysis of Potential Contaminant Migration from Abandoned In Situ Coal Conversion Reactors

“…Groundwater flow and contaminant transport simulations were performed by means of the fluid flow and transport code TRANSPORT Simulation Environment (TRANSPORTSE) (Kempka, 2020;Kempka et al, 2022). It considers pressureand density-driven fluid flow, convective and conductive heat transport, as well as advective, diffusive and dispersive chemical species transport.…”