Experimental Investigation of the Mechanisms of Salt Precipitation during CO2 Injection in Sandstone

Abstract

Deep saline reservoirs have the highest volumetric CO2 storage potential, but drying and salt precipitation during CO2 injection could severely impair CO2 injectivity. The physical mechanisms and impact of salt precipitation, especially in the injection area, is still not fully understood. Core-flood experiments were conducted to investigate the mechanisms of external and internal salt precipitation in sandstone rocks. CO2 Low Salinity Alternating Gas (CO2-LSWAG) injection as a potential mitigation technique to reduce injectivity impairment induced by salt precipitation was also studied. We found that poor sweep and high brine salinity could increase salt deposition on the surface of the injection area. The results also indicate that the amount of salt precipitated in the dry-out zone does not change significantly during the drying process, as large portion of the precipitated salt accumulate in the injection vicinity. However, the distribution of salt in the dry-out zone was found to change markedly when more CO2 was injected after salt precipitation. This suggests that CO2 injectivity impairment induced by salt precipitation is probably dynamic rather than a static process. It was also found that CO2-LSWAG could improve CO2 injectivity after salt precipitation. However, below a critical diluent brine salinity, CO2-LSWAG did not improve injectivity. These findings provide vital understanding of core-scale physical mechanisms of the impact of salt precipitation on CO2 injectivity in saline reservoirs. The insight gained could be implemented in simulation models to improve the quantification of injectivity losses during CO2 injection into saline sandstone reservoirs.

Geophysical early warning of salt precipitation during geological carbon sequestration

“…Numerical simulations predict significant salt-induced pressure build-up around the CO 2 injection well, the preferential salt precipitation area 15 – 17 , even for high permeability rocks and low injection rates 18 , 19 . Experimental studies have confirmed CO 2 —induced salt precipitation in porous media from lab-on-chip experiments 6 , 20 and core scale flow-through tests 21 – 23 . Experimental observations show that the precipitation process starts after a transition period post—CO 2 injection, forming early pore scale crystals in the brine, followed by late polycrystalline aggregates at the CO 2 —brine interface 7 .…”

Assessment of Advanced Remediation Techniques for Enhanced CO2 Injectivity: Laboratory Investigations and Implications for Improved CO2 Flow in Saline Aquifers

“…This localized precipitation subsequently narrowed these pore spaces, restricting fluid flow. This phenomenon, observed in studies utilizing similar core flooding techniques, can significantly restrict fluid flow and contribute to the observed permeability reduction − …”

Evaluation of Potential of CO2-Enhanced Oil Recovery (EOR) and Assessment of Capacity for Geological Storage in a Mature Oil Reservoir within Upper Assam Basin, India

“…This phenomenon is particularly pronounced in and around the borehole, where substantial volumes of dry CO 2 traverse the rock formation. This effect is generally more common in CO 2 storage in saline aquifers, but this may also happen in CO 2 -EOR . In this work, an attempt has been made to capture the effect of halite precipitation and associated changes in porosity and permeability.…”

“…This effect is generally more common in CO 2 storage in saline aquifers, but this may also happen in CO 2 -EOR. 62 In this work, an attempt has been made to capture the effect of halite precipitation and associated changes in porosity and permeability.…”