Derivation of a Petrophysical Model for Contact Angle Based on PURCELL’S Equation and CO2-Sandstone Brine System Calculation for Core flooding Wettability Preservation

Abstract

In the petroleum industry, core flooding intended to study the relative permeability of the carbon dioxide–brine–rock system is carried out using predetermined wettability states where carbon dioxide saturated brine is injected to displace carbonated brine. This prevents mutual solubility and acidity generation to influence wettability during gas flooding stage. However, no one has yet found out if these systems retain their ambient wettability states despite the availability of relevant petrophysical models that are useful for developing suitable modes for contact angle calculation. The motivation of this study stems from this knowledge gap in issues related to wettability preservation in multiphase flow in porous media. In this paper, we have used published data on carbon dioxide–brine–rock systems to show that core plugs do retain their predetermined wettabilities. The basis for this inference is the calculation of a wettability dependent parameter and contact angle, using a derived petrophysical model based on Purcell’s original equation. In addition to acid gas systems, a similar approach has also been applied to an oil–water system, which generally retains its predetermined wettability. Trends in contact vs. water saturation for both systems are found to be similar, indicating wettability preservation during core flooding. Consequently, we have demonstrated for the first time, the feasibility of contact angle calculation using our derived equation.