Simulation of rock salt dissolution and its impact on land subsidence

Abstract

Abstract. Extensive land subsidence can occur due to subsurface dissolution of evaporites such as halite and gypsum. This paper explores techniques to simulate the salt dissolution forming an intrastratal karst, which is embedded in a sequence of carbonates, marls, anhydrite and gypsum. A numerical model is developed to simulate laminar flow in a subhorizontal void, which corresponds to an opening intrastratal karst. The numerical model is based on the laminar steady-state Stokes flow equation, and the advection dispersion transport equation coupled with the dissolution equation. The flow equation is solved using the nonconforming Crouzeix-Raviart (CR) finite element approximation for the Stokes equation. For the transport equation, a combination between discontinuous Galerkin method and multipoint flux approximation method is proposed. The numerical effect of the dissolution is considered by using a dynamic mesh variation that increases the size of the mesh based on the amount of dissolved salt. The numerical method is applied to a 2-D geological cross section representing a Horst and Graben structure in the Tabular Jura of northwestern Switzerland. The model simulates salt dissolution within the geological section and predicts the amount of vertical dissolution as an indicator of potential subsidence that could occur. Simulation results showed that the highest dissolution amount is observed near the normal fault zones, and, therefore, the highest subsidence rates are expected above normal fault zones.

Experimental study of geophysical and transport properties of salt rocks in the context of underground energy storage

“…The process of solution mining and cavern formation at shallow depths (where halite is not in a plastic deformation regime) involves (i) injecting water using injection tubing to dissolve the underground salt and form brine and (ii) extracting the brine solution to surface with a production tubing set, sufficiently below the injection point to extract the higher density brine flowing downwards (Fokker, 1995). Salt cavern selection and development requires assessing potential salt damage, fracturing and containment risks from cyclic loading related to short-term seasonal fluctuations in energy demand, or land subsidence due to subsurface dissolution (Fokker, 1995;Zheng et al, 2017;Zidane et al, 2014).…”

Multi-Scale Analysis of Surface Building Density and Land Subsidence Using a Combination of Wavelet Transform and Spatial Autocorrelation in the Plains of Beijing

“…The effects of subsidence can be far-reaching and include changes in the landscape, disruption of surface water drainage, and destruction of buildings and infrastructure. It can be caused by natural factors such as soil compaction, tectonic movements, dissolution processes, and subsurface water removal, or by human activities such as mining and construction [3][4][5][6][7][8]. The impacts and extents of the various contributing elements can vary significantly from one geological setting to the next and can have a significant impact on the overall scale of the process.…”

Spatial and Temporal Evolution of Leaching Zones within Potash Seams Reproduced by Reactive Transport Simulations

“…Accordingly, a sequential coupling of transport and chemistry as described in Steefel et al [8] does not suffice but an additional approach to describe the process interaction at the solid/liquid interface is required. Reactive transport models dealing with rock salt often use a mass transfer rate to overcome this limitation [9][10][11]. Laouafa et al [12,13] introduced a local non-equilibrium diffuse interface model to describe the dissolution of halite and gypsum at the interface.…”