Estimating Dynamical Mineral Dissolution for Co2 Injection Into Saline Aquifers Utilizing Deep Learning in the Ahuroa Saline Aquifer

Abstract

The geological carbon storage (GCS) in subsurface environments, such as deep permeable saline formations, is one of the achievable methods for carbon dioxide storage. There are several commercial projects such as the Sleipner field in Norway, and in Salah in Algeria have demonstrated that carbon dioxide can be safely stored in these reservoirs. The natural environments are capable to store CO2 on geologic time scales, that is mostly caused by solubility trapping. While the geological, physical and chemical conditions for the escape of CO2 are still in the research phase and how CO2 can be efficiently stored, there are several important features that represent prerequisites for the efficient storage (Xu, et al. 2017). A core prerequisite is the availability of sufficient porosity in order to accommodate the desired volumes of carbon dioxide, and the presence of a continuous cap rock that is impermeable to CO2. Deep saline reservoirs are attractive candidates for the geological storage and based on the deep geologic storage temperature and pressure, the CO2 is typically in a supercritical but stable state. The challenge is that the introduction of CO2 into the reservoir may lead to a geochemical process which acidifies the brine via CO2 dissolution. Furthermore, the mineral surfaces are dehydrated by the dispersing CO2 phase. Experimental and field studies indicate that the geochemical reactions caused by the injection of CO2 may vary significantly between different rock types and brine compositions (Michael, et al. 2010). The low permeability of the cap rock, such as shale, have demonstrated to be reactive for higher temperature ranges, which poses additional challenges for the CO2 storage process. The dissolution and re-precipitation of carbonate minerals, and the dissolution of feldspars are generally observed for these CO2 storage reservoir sites that additionally encounter challenges related to the precipitation of clay minerals. This implies that the dissolution and secondary mineral precipitation caused by the injection of CO2 have a major impact on the porosity and permeability of the reservoir environment as well as impact the cap rock integrity (Jiang, et al. 2014).