Numerical investigation of thermohaline convection in fractured-porous media near salt domes: the fractured salt chimney problem

Salt domes are considered as host rocks for long-term nuclear waste disposal. Groundwater flow in the near salt domes may lead to the transport of radionuclides into the biosphere. The following key factors that influence groundwater dynamics are the presence of brine as a result of salt dissolution, heat generation from radioactive waste and the "salt chimney effect"-a phenomenon in which the geothermal heat flux and high thermal conductivity of salt rock induce elevated temperatures around salt domes. The resulting temperature and salinity variations affect groundwater density (and viscosity), driving thermohaline convection in adjacent rock layers of the salt dome. Variable density and viscosity lead to coupled processes due to the highly nonlinear nature of the problem, which is challenging to model numerically. This study defines the fractured salt chimney problem and investigates for the first time the effect of fractures in the surrounding rock layers of a salt dome on thermohaline convection in these layers. Results show that the presence of fractures can have a strong impact on salt transport rates and the thermohaline convection patterns near salt domes.