Challenges associated with Quartz Crystal Microbalance with Dissipation (QCM-D) as a wettability screening tool

Abstract

Wettability is an indispensable parameter in multiphase flow due to its profound effect in fluid phase distribution and flow properties in the oil reservoirs. One approach of unravelling the enigma associated with wettability characterization is to investigate oil adhesion onto reservoir rock surface during crude oil accumulation. This was accomplished using Quartz Crystal Microbalance with Dissipation (QCM-D) device. The QCM-D is a microbalance device that hinges on the changes in the frequency of a resonating crystal due to changes in the mass on sensor surface, precipitation, adsorption and desorption. However, this technique was confronted with numerous challenges during its early try-out. The objective of this study is to enumerate these challenges and how they were resolved. The piston-cell, valves, flow-lines and most of the experimental set-up were made from stainless steel. Hence, the high temperature coupled with high salinity brine resulted in the formation and deposition of corroded materials on the sensor. Due to the high sensitivity of the QCM-D technique, these corrosion deposits were detected via the high attenuation of the frequency signal as time elapsed during Formation Water (FW) injection. The second challenge was related to the dissolution of the thin sensor coatings (sensor etching) depicted by the relatively high increase in frequency signal with negligible changes in Dissipation (D). The third challenge was related to the trapping of fluids such as Stock Tank Oil (STO) inside the flow-cell. Finally, salt precipitation resulting from temperature variation during the initial experimental set-up was also observed. To resolve the corrosion challenge, all the stainless-steel components in the experimental set-up were replaced with titanium and non-metallic component such as peek materials. The sensor etching was also averted by injecting the brine through a packed column filled with similar mineral as the coatings on the sensor to attain equilibrium prior to injecting it onto the sensor. Geochemical simulation of the sensor etching was also confirmed using the geochemical simulator PHREEQ-C. Furthermore, the trapping of fluids inside the flow-cell was overcome by rotating the flow-cell to optimize the fluid displacement via capitalizing on their density contrast. Finally, the salt precipitation was avoided by conducting the experiment in a constant temperature experimental set-up. The QCM-D technique can be employed to estimate wettability by evaluating the tendency of the various minerals to adhere oil. The beauty of the QCM-D technique is that the surface interactions can be monitored on a real-time.