Impact of Capillary Pressure, Salinity and In situ Conditions on CO2 Injection into Saline Aquifers

Abstract

This article presents a numerical investigation of the combined effects of capillary pressure, salinity and in situ thermodynamic conditions on CO 2 -brine-rock interactions in a saline aquifer. We demonstrate that the interrelations between capillary pressure, salinity, dissolution and drying-out affect CO 2 injectivity and storage capacity of a saline aquifer. High capillary forces require a high injection pressure for a given injection rate. Depending on salinity, the increase in injection pressure due to capillary forces can be offset by the dissolution of CO 2 in formation water and its compressibility. Higher capillary forces also reduce gravity segregation, and this gives a more homogeneous CO 2 plume which improves the dissolution of CO 2 . The solubility of CO 2 in formation water decreases with increasing salinity which requires an increased injection pressure. Higher salinity and capillary pressure can even block the pores, causing an increased salt precipitation. Simulations with various pressure-temperature conditions and modified salinity and capillary pressure curves demonstrate that, with the injection pressures similar for both cold and warm basins at a given injection rate, CO 2 dissolves about 10% more in the warm basin water than in the cold basin. The increase in dissolution lowers the injection pressure compensating the disadvantage of low CO 2 density and compressibility for storage in warm basins.

Dynamic Behavior of CO2 in a Wellbore and Storage Formation: Wellbore-Coupled and Salt-Precipitation Processes during Geologic CO2 Sequestration

“…In regard to the salt-precipitation process occurring adjacent to the injection well, a number of previous studies have been conducted with TOUGH2/ECO2N [34,[38][39][40][41][42]. However, only a few studies considered the influence of salinity on both wellbore and reservoir flow [25,58].…”

“…is calculated by two independent geometric parameters such as fraction of original porosity ( = / 0 ) and fractional length of pore body (Γ). According to few previous studies, both and Γ were set to be 0.8 [38,39].…”

“…Subsequently, the dry-out zone would be developed in the vicinity of the injection well where residual brine evaporated to dry-CO 2 while precipitating the solid salt [33,34]. Previously, numerous studies including both experimental [35][36][37] and numerical studies [34,[38][39][40][41] evaluated development of dry-out zone and associated saltprecipitation. Among them, Oh et al [36] conducted coreflooding experiments and captured the salt-precipitation at the core-inlet by using SEM images.…”

Reactive transport modeling for CO2 geological sequestration

“…The combined effects of capillary pressure, salinity and in situ conditions on CO2-brine-rock interactions in saline aquifers have been discussed in detail by Alkan et al (2010). A fraction of CO 2 gas, which is dependent on residual gas saturation (a value of 0.05 was used in the current simulation), is trapped in the porous rock as residual gas after injection.…”

Capillary-Driven Transport of Dissolved Salt to the Drying Zone During $$\hbox {CO}_{2}$$ CO 2 Injection in Homogeneous and Layered Porous Media

“…In case viscous forces dominate over capillary forces, salt precipitates locally, and the decrease in soil permeability due to salt precipitation can be counteracted by the increase in relative permeability caused by the increase in CO 2 saturation (Ott et al 2011;Roels et al 2014). When capillary forces are dominant over viscous forces, complete clogging can occur by accumulation of salt via continuous transport of brine by capillary forces toward to the dry zone around the injection well (Alkan et al 2010;Peysson 2012).…”