Abstract
In terms of storage capacity and containment efficiency, deep saline aquifers are among the best candidates for CO2 storage. However, salt precipitation in the wellbore vicinity and fines mobilization ensued from in situ mineral dissolution could impair CO2 injectivity and reduce the quality and capacity of deep saline reservoirs for CO2 storage. The mechanisms of salt precipitation and its impact on CO2 injectivity have been studied, but the effects of fines mobilization have not been properly investigated. We conducted core-flood experiments and theoretical studies to investigate the impact of fines mobilization on CO2 injectivity, the relative contribution of fines mobilization and salt precipitation to injectivity impairment, and the coupled effect of salt precipitation and fines mobilization. We found that, mineral dissolution and transport effects could induce up to about 26% injectivity impairment. The findings also suggest that about 0.3 wt % particle concentration in the pore fluid could induce over twofold injectivity impairment compared to about 10 wt % of total dissolved salt in the formation water. Salt precipitation was also found to compound injectivity impairment induced by fines mobilization. The present study provides important insight, and could serve as a foundation to inspire further experimental and theoretical investigation into the effects of mineral dissolution and fines mobilization in the context of CO2 injectivity.
Highlights
CO2 Capture, Utilization, and Storage (CCUS) has potential to reduce the concentration of CO2 in the atmosphere and prevent climate change
Lombard et al [2] classified CO2 injectivity impairment mechanisms into three main groups: transport effects such as fines mobilization, geochemical effects such as mineral dissolution, and salt precipitation and geomechanical processes. Among these injectivity impairment challenges, salt precipitation effects have attracted the highest attention over the past years [3,4,5,6,7]
The effect of fines mobilization on CO2 injectivity has not been given its deserved attention, probably because of available evidence of massive injectivity impairment induced by salt precipitation
Summary
CO2 Capture, Utilization, and Storage (CCUS) has potential to reduce the concentration of CO2 in the atmosphere and prevent climate change. Lombard et al [2] classified CO2 injectivity impairment mechanisms into three main groups: transport effects such as fines mobilization, geochemical effects such as mineral dissolution, and salt precipitation and geomechanical processes. Among these injectivity impairment challenges, salt precipitation effects have attracted the highest attention over the past years [3,4,5,6,7]. A dimensionless dry-out length, ld = LL1 , defined as the ratio of the length of the dry-out region to the total length of the core, was introduced to track the development of the dry-out zone and characterize the distribution of precipitated salt.
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