Modeling of Contact Angle versus pH and Derivation of Contact Angle versus Pressure in Deep Saline Aquifers under Geological Carbon Storage

Abstract

Geological storage of anthropogenic carbon dioxide is regarded as a technically and economically viable strategy for mitigating carbon dioxide induced climate warming. 
 
 Central to geological storage of anthropogenic carbon dioxide is the water rock interaction, which has a direct bearing on pH induced wettability evolution in saline aquifers. Consequently, understanding contact angle trend versus injected gas pressure is useful, considering its relationship to pH evolution in formation brine due to dissolved gas at prevailing temperatures and salinities. Several research works have published experimental data on contact angle versus pressure pertaining to geological conditions of anthropogenic carbon storage. In the present study, we have used thermodynamic theories relating to a surface charge model, contact angle and the classical Nernst equation to derive a logarithmic pH dependent contact angle equation. Considering the relationship between carbon dioxide solubility and pressure for a given temperature and salinity as well as the link between pH and the extent of solubility, we have plotted calculated contact angles versus corresponding pressures. Results of the plots obtained compare well with literature values. Therefore, given the lack of theoretical approach regarding contact angle versus pressure, our research work fills the knowledge gap considering the novelty in the derivation of the pH dependent contact angle equation.

Applicability of the Linearized Poisson-Boltzmann Theory to Contact Angle problems and Application to the Carbon Dioxide-Brine-Solid Systems

“…In line with the dissolution of carbon dioxide in brine and its subsequent hydration into carbonic acid, the dissociation of the acid will produce hydrogen ions to cause pH evolution with pressure at a given salinity of aqueous solution (Li et al, 2018). Following Miadonye and Amadu (2020), the relationship between pH of aqueous brine containing dissolved d carbon dioxide at a given pressure at a given constant temperature is calculated as: The temperature and salinity dependent ionization constant is given as (Aissa et al, 2015): (33) In this equation, γ is the ionic strength [M]. Bahadori et al, (2009) have developed a correlation for predicting the solubility of carbon dioxide in pure water as well as the aqueous sodium chloride solutions based on reduced ( )…”