Temperature and pH Effect on the Contact Angle in Quartz/Water/N-decane System
Open Access
- Author:
- Li, Jiaxi
- Graduate Program:
- Energy and Mineral Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 22, 2021
- Committee Members:
- Mort D Webster, Program Head/Chair
Serguei Lvov, Thesis Advisor/Co-Advisor
Randy Lee Vander Wal, Committee Member
Arash Dahi Taleghani, Committee Member - Keywords:
- Quartz
Contact Angle
Temperature
pH
Wettability - Abstract:
- We have developed a capillary-based system that is able to measure the contact angle in a quartz/water/n-decane system at different temperatures up to 200 ℃ in a pH range of 2-12 under elevated pressures up to 69 bar. Wettability of the reservoir rock is correlated to oil recovery and contact angle in a three-phase system, and the contact angle is an important scale of the system wettability. The obtained data indicate a strong temperature dependence of the contact angle from 25 ℃ to 200 ℃ at the neutral pH (increases 1.1°per +5 ℃). This positive linear trend cannot be sufficiently explained neither by the viscous force influencing the dynamic contact angle nor by the interfacial tension on the water/n-decane interface. Instead, the variation of the interfacial tension on the solid/liquid interfaces should be considered as well. With the increase of temperature, pH of the same solution decreases due to a significant change of the ionization constant of water. The contact angle shows a parabolic trend from the acidic pH to the basic pH at the same temperature, and the maximum contact angle was observed at the isoelectric point of quartz. The pH dependence of the contact angle can be explained via the Zeta potential of quartz, which indicates the degree of electrostatic repulsion between the quartz surface and n-decane. We used a general correlation to empirically describe the contact angle under different temperatures and pH. The isoelectric point obtained from the general equation is in good agreement with data reported in other literature based on the same solid material and method. To verify our experimental results, we employed the surface tension component (STC) method, which divides the surface energy into the polar part and the non-polar part, respectively. The calculated results based on the STC method show a good agreement with our experimentally-measured contact angle. The STC method suggests that the temperature influences both polar and non-polar interactions between quartz and water, while pH only changes the polar interaction.