Analytical Solution for Predicting Salt Precipitation During CO2 Injection Into Saline Aquifers in Presence of Capillary Pressure

Salt precipitation within pores of the reservoir is an important phenomenon occurring during CO2 injection into saline aquifers. The phenomenon results in permeability reduction and injectivity impairment. Salt precipitation mainly happens because of water vaporization inside the CO2‐saturated (dry‐...

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Bibliographic Details
Published in:Water resources research 2022-06, Vol.58 (6), p.n/a
Main Authors: Norouzi, A. M., Niasar, V., Gluyas, J. G., Babaei, M.
Format: Article
Language:English
Subjects:
analytical solution
Aquifers
Brines
Capillary pressure
Capillary waves
Carbon dioxide
Chemical precipitation
CO2 storage
Exact solutions
Flow theory
Impairment
Injection
Permeability
Precipitation
Pressure
Pressure effects
Reservoirs
salt precipitation
Salts
Saturation
Shock waves
Simulators
Vaporization
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Summary:Salt precipitation within pores of the reservoir is an important phenomenon occurring during CO2 injection into saline aquifers. The phenomenon results in permeability reduction and injectivity impairment. Salt precipitation mainly happens because of water vaporization inside the CO2‐saturated (dry‐out) region. For water‐wet systems, the capillary pressure acts toward the lower water saturation regions in the reservoir, thereby displacing a film of brine backward to the dry‐out region. This results in more precipitation. Overlooking this phenomenon, referred to as capillary‐driven backflow, results in over‐estimations of injectivity in the dried region. Here, we have developed an analytical solution based on fractional flow theory and shock waves for CO2‐brine systems considering the effect of capillary pressure. The validity of the solution is verified by comparing the outputs of our model with those of numerical results from a commercial numerical simulator for a hypothetical reservoir. An equation is derived to calculate the distance at which capillary pressure is most influential, and also the injectivity impairment at injection well due to salt precipitation was reasonably accurately estimated. The results emphasize that effects of capillary pressure should not be ignored. Key Points Effects of capillary pressure were included in an analytical solution of CO2 injection into saline aquifers Capillary backflow induced salt precipitation affects injectivity of the wells in the aquifer The area that is mostly affected by salt precipitation, near the injection, can be estimated through mass balance
ISSN:0043-1397
1944-7973
DOI:10.1029/2022WR032612