Numerical Study of the Permeability Change Induced by Hot Water Injection in Deep Subsurface Thermal Energy Storage

Abstract

Seasonal storage of excess energy in deep subsurface is an essential technology for the efficient usage and management of the energy resources. Recently, the deep subsurface thermal energy storage is rising as an important topic and keeps attracting the attention of the researchers. Permeability plays a key role for successful thermal storage, particularly in the vicinity of the wells. In the course of the subsurface thermal energy storage, the chemical fluid-rock equilibrium of a geothermal reservoir may become disturbed induced by the injection of hot water. Consequently, dissolution and precipitation reactions as well as the fines transport might result in the permeability damage. Understanding the permeability and porosity alteration is critical in predicting fluid migration in the subsurface and long-term operation efficiency of the thermal storage system. Here, we present a novel continuum non-isothermal reactive transport model that captures and predicts the spatial pattern of permeability and porosity evolution in a sandstone reservoir. The model considers mineral dissolution and precipitation under the influence of the temperature change, and tracks the potential feedbacks between flow, heat transfer, chemical reactions and fines transport. The developed model is validated by replicating the existing core flooding experimental measurements(Rosenbrand et al., 2014) of the porosity reduction and the evolving silica and calcite concentration. Subsequently, by simulating the thermal storage in the deep subsurface at the field scale, the long-term evolution of the rock permeability is predicted. Reference Rosenbrand, E., Haugwitz, C., Sally, P., Jacobsen, M., Kjøller, C. and Lykke, I.: Geothermics The effect of hot water injection on sandstone permeability, Geothermics, 50, 155–166, doi:10.1016/j.geothermics.2013.09.006, 2014.