Optimizing CO2 storage efficiency using formic acid intervention for salt precipitation management: insights from static batch experiments and core flooding studies

Abstract. Geological CO2 storage is a vital technique to reduce the global carbon footprint. However, this technique is hindered by frequent salt precipitation due to the CO2 injection. This study experimentally evaluates the impact of formic acid as salt precipitation mitigation products to improve CO2 injectivity, through core flooding experiments on selected core samples, and static batch experiments. The main hypothesis is to verify the claim if formic acid can improve CO2 injectivity in salt-induced formation damage. The experiments were conducted in two stages using a 7wt% brine and 17wt% brine at conditions of 1600psi and 60 oC. The results were compared with freshwater, which is a conventional technique used to dissolve the salts. Also, SEM images were taken at each of the stages to understand the morphological and petrographical changes pre- and-post treatment. Results from this study showed salt precipitation led to a reduction in porosity and permeability. Specifically, porosity decreased by 25-30%, while permeability decreased by up to 72% across all tested scenarios post CO2 injection. Also, the salting-out effect was more pronounced in high salinity brine compared to low salinity brine. Injection of remediation fluids during tests effectively opened pore spaces and throats in core samples, resulting in increased permeability. After using reactive fluids, permeability improved by up to 16% compared to the sample’s initial permeability. Based on the SEM analysis of the core samples pre-and-post treatment, it was found that, salt precipitation not only blocked the pore spaces within the core matrix, but it also accumulated significantly around the rock grains, forming aggregates of salts. Also, after flooding with the treatment fluid, the SEM results reveal increased pore throats and salt dissolution. This observation shows the possibility of using formic acid as a treatment fluid for the reduction of salt precipitation occurring in both the pore spaces and pore throats. By understanding the intricate interplay between salt precipitation and rock behavior after using reactive fluids, the efficiency and sustainability of geological CO2 storage can be enhanced.