Hydrogeological feasibility of mine water deep geological storage in Baotashan coarse sandstone: A case study in Ordos Basin

Abstract

For the sake of mine water drainage and sustainable groundwater protection, the new approach of mine water deep geological storage (MWDGS) is highly necessary to save water resources in the semi-arid region of China. However, up to now, little academic research has been done on mine water geological storage. Given this situation, the hydrogeological feasibility of MWDGS was explored in Baotashan coarse sandstone (BCS) of Jurassic measure in Ordos Basin. The results show that the white-gray BCS with a fragile skeleton of quartz (41.4%), feldspar (21.1%), and clay minerals (16.4%) provides the potential variable-void for mine water; and its hydro-chemical type of BCS aquifer is CO₃-Na and Cl-Na. As the burial depth increases, the strong alkaline groundwater is in stagnant and poor recharge-runoff-discharge condition. The lab test shows that the pores whose diameter is over 10 μm could be treated as the main storage of mine water; and the effective porosity varies from 1.36% to 3.46%. When mine water is injected, the strong hydrodynamics of mine water storage would change the permeability significantly and about 0.201% soluble solids would be dissolved. Partial clay minerals obstruct the pores and induce the saturated phase of high permeability to evolve into steady phase of lower permeability. Under the condition of nonhydraulic fracturing during continuous storage, the heterogeneous anisotropic medium obtained by Transition PRObability GeoStatistics (TPROGS) shows that the capacity of BCS aquifer is 0.455 to 1.226 Mm³ for 1 km² in the study area. The simulation shows that the groundwater mound in well-scale and mine-scale would be formed. The groundwater quality characteristics of “Three Zone” would occur around and gradually drop to approximate the original brine within 10 years. The hydrogeological feasibility reveals that this approach is useful for the well design and groundwater environment management during the mine water deep geological storage project in the Ordos basin.