Ahmed Saad Successfully Defended His Ph.D. Dissertation

25 October, 2022

Congratulations to EGG group member, Ahmed Saad, who successfully defended his Ph.D. dissertation on October 25th, 2022. The title of his Ph.D. dissertation is "Interfacial phenomena in mixed-wet oil reservoirs: two-phase fluid dynamics and chemo-rheology at pore-scale", under the supervision of Professor Tadeusz Patzek. Dr. Saad's Ph.D. dissertation was remarked as novel and one of its kind by the Ph.D. defense committee.

The abstract of his Ph.D. dissertation is the following.

Crude oil is a complex fluid containing various components with widely different chemical properties. When it comes in contact with water, its polar components adsorb at the oil/water interface, reducing the interfacial tension and eventually developing viscoelastic films. The interfacial films impact emulsion stability and, in some cases, adhere to the oil-bearing reservoir rocks, altering their wettability and thus hindering oil mobilization. Despite the substantial research conducted in this area, the underlying mechanisms relating the physicochemical properties of the interfacial films to the composition of the bulk phases are still unclear. Here, we investigate the formation of crude oil/water interfacial films. We measure both the time-dependent shear and extensional interfacial rheology moduli, and we relate it to the chemical composition of the films.

To study the rock/fluid interaction, we present experimental verification of a capillarity-driven pore invasion mechanism that can potentially recover bypassed asphaltenic oil from reservoir formations. First, we fabricate mixed-wet capillaries with angular cross-sections inspired by the naturally occurring primary drainage of pore-filling brine by invading crude oil. We validate our proposed procedure by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and contact angle measurements. After employing our novel coating procedure, we experimentally investigate the invasion in mixed-wet square capillaries and compare it with the predictions of dynamic and quasi-static (Mayer-Stowe-Princen (MSP)) meniscus-invasion models dynamic models.

To our knowledge, this is the first direct experimental validation of MSP theory under mixed-wet conditions in such a controlled manner. We confirm the possibility of spontaneous piston-type imbibition with high (> 90◦) advancing contact angles into mixed-wet pores, given that the contact angle is lowered below a critical value that is a function of the pore geometry and residual water saturation. In oil reservoirs, injection of specific brines would be required to change the contact angle to values below the imbibition threshold. Finally, we extend our study by performing 3D high-speed laser imaging of dynamic fluid flow in angular capillaries.