Experimental and theoretical investigation of the mechanisms of drying during CO2 injection into saline reservoirs

Abstract

A viable CO2 storage resource must have sufficient storage capacity, reliable containment efficiency and adequate well injectivity. Deep saline formations stand out in terms of storage capacity and containment efficiency. However, formation brine dry-out and salt precipitation in the near well region could impair CO2 injectivity in deep saline reservoirs, thus reducing their potential for CO2 storage. Core-flood experiments and analytical modelling were used to investigate various mechanisms of external and internal salt precipitation. Particularly, the impact of the extension of the dry-out region on CO2 injectivity was investigated. It was found that, for high permeability rocks, injection of CO2 at relatively low injection rates could result in salt cake deposition at the injection inlet especially under high salinity conditions. It was also found that extension of the dry-out region does not have significant impact on CO2 injectivity. Although the magnitude of CO2 injectivity impairment increased more than two-fold when initial brine salinity was doubled, real-time changes in CO2 injectivity during the drying process was found to be independent of initial brine salinity. We have shown that the bundle-of-tubes model could provide useful insight into the process of brine vaporization and salt deposition in the dry-out region during CO2 injection. This work provides vital understanding of the effect of salt precipitation on CO2 injectivity.

Carbonated Water Injection for Enhanced Oil Recovery and CO2 Geosequestration in Different CO2 Repositories: A Review of Physicochemical Processes and Recent Advances

“…However, further reservoir and geological characterizations are necessary to ensure the integrity of reservoir seals, understand net-to-gross ratios, identify faults, define reservoir boundaries, and determine fracture gradients . Numerous studies have investigated CO 2 storage in saline aquifers, chiefly by injecting supercritical CO 2 . ,, However, past and recent assessments have failed to extensively investigate the CO 2 storage potential of CWI in saline aquifers. Rather, the studies largely examined the geochemical interactions between injected CW, formation brine, and rock minerals (discussed in section ).…”

“…For the past seven decades, extensive research has focused on utilizing CO 2 injection techniques for EOR and CO 2 geosequestration (CGS) to address energy demand and environmental challenges. CO 2 injection techniques encompass a range of approaches, including direct/continuous CO 2 injection, 11 alternate injection of water and CO 2 (CO 2 WAG), 12 and carbonated water injection (CWI). 2,13 Each technique possesses advantages and challenges regarding displacement efficiency, sweep efficiency, and gas breakthrough.…”

“…For the past seven decades, extensive research has focused on utilizing CO 2 injection techniques for EOR and CO 2 geosequestration (CGS) to address energy demand and environmental challenges. CO 2 injection techniques encompass a range of approaches, including direct/continuous CO 2 injection, alternate injection of water and CO 2 (CO 2 WAG), and carbonated water injection (CWI). , Each technique possesses advantages and challenges regarding displacement efficiency, sweep efficiency, and gas breakthrough. Direct CO 2 injection exhibits excellent pore-scale displacement efficiency but encounters problems such as leakages, poor sweep efficiency, gravity segregation, gas channeling, and gas fingering. ,, Conversely, CO 2 WAG improves sweep efficiency, but the technique experiences an early gas breakthrough and adverse water shielding effect that compromises oil production and CO 2 storage. − Injecting CO 2 as a dissolved phase (carbonated water (CW)) effectively mitigates these challenges.…”

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

“…14 These precipitated salts formed can obstruct the flow of CO 2 within the porous rock matrix, thereby impairing the CO 2 injectivity. 15,16 More so, these salt formations can serve as nucleation sites for further precipitation, 10 creating a cycle of injection obstructions and operational disturbances. In extreme cases, the extensive salt buildup can completely block the injection well, rendering the well inoperable and jeopardizing the entire CCS operation.…”

“…During CO 2 injection in saline aquifers, the dry scCO 2 stream interacts with the resident brine, leading to the evaporation of water. ,, This evaporation process results in the precipitation of salts, a phenomenon referred to as the drying effect . These precipitated salts formed can obstruct the flow of CO 2 within the porous rock matrix, thereby impairing the CO 2 injectivity. , More so, these salt formations can serve as nucleation sites for further precipitation, creating a cycle of injection obstructions and operational disturbances. In extreme cases, the extensive salt buildup can completely block the injection well, rendering the well inoperable and jeopardizing the entire CCS operation.…”