Role of interfacial tension on wettability-controlled fluid displacement in porous rock: A capillary-dominated flow and how to control it

Oil displacement by spontaneous imbibition is a capillary-governed process, in which wettability controls fluid displacement direction. Capillarity is a driving force to enhance oil displacement in water-wet system, while in oil-wet system capillarity is a resisting one. To promote oil displacement, the former requires high capillarity, but the latter opposes. Such requisites are hypothesized to be alternatively achieved by manipulating an oilwater interfacial tension, without altering wetting character. In this study, spontaneous imbibition was conducted with a set of specifically designed imbibing fluids. Brines at different valencies were meticulously selected to attain desired wettabilities: monovalent brine establishes a water-wetting while divalent brine provides an oil-wet characteristics. A non-ionic surfactant, Triton X-100, was intentionally chosen to solely reduce interfacial tension, with negligible change in wettability. By mixing each brine with the surfactant, high-interfacial tension and low-interfacial tension imbibing fluids at the same wettability for the two wetting regions were obtained, and hence the hypothesis can be examined. For water-wet system, reduced interfacial tension attributed to a weakened driving capillary force to oil displacement, and hence lower oil displaced. On the contrary in oil-wet system, reduction in resisting capillary force as contributed from a reduced interfacial tension displaced greater oil. The results demonstrate how the capillary-driven fluid displacement can be manipulated by the interfacial tension change only, without a challenge of altering wettability. With results obtained from both wetting regions, a correlation between capillarity and ultimate oil displacement was also observed.Document Type: Original articleCited as: Tangparitkul, S., Sukee, A., Jiang, J., Tapanya, C., Fongkham, N., Yang, H. Role of interfacial tension on wettability-controlled fluid displacement in porous rock: A capillary-dominated flow and how to control it. Capillarity, 2023, 9(3): 55-64. https://doi.org/10.46690/capi.2023.12.0

Fabrication of an acetone gas sensor based on Si-doped WO3 nanorods prepared by reactive magnetron co-sputtering with OAD technique

Gas sensing technology is currently applied in a variety of applications. In medical applications, gas sensors can be used for the detection of the biomarker in various diseases, metabolic disorders, diabetes mellitus, asthma, renal, liver diseases, and lung cancer. In this study, we present acetone sensing characteristics of Si-doped WO _3 nanorods prepared by a DC reactive magnetron co-sputtering with an oblique-angle deposition (OAD) technique. The composition of Si-doped in WO _3 has been studied by varying the electrical input power applied to the Si sputtered target. The nanorods film was constructed at the glancing angle of 85°. After deposition, the films were annealed at 400 °C for 4 h in the air. The microstructures and phases of the materials were characterized by x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM). The results showed that 1.43 wt% Si-doped WO _3 thin film exhibited the maximum response of 5.92 towards 100 ppm of acetone at performing temperature (350 °C), purifying dry air carrier. The process exposed in this work demonstrated the potential of high sensitivity acetone gas sensor at low concentration and may be used as an effective tool for diabetes non-invasive monitoring