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The effects of velocity and gas type on foam flow through porous media have yet to be completely elucidated. Pressure drop and capillary pressure measurements were made at ambient conditions during a series of foam quality scan experiments in a homogenous sandpack while foam texture was simultaneously visualized. New insights into foam-flow behavior in porous media were discovered. Previously accepted "limiting" capillary pressure theory is challenged by the findings in this work, and the "limiting" terminology is replaced with the word "plateau" to reflect these novel observations. Plateau capillary pressure [Formula: see text] and transition foam quality were found to increase with velocity. Transition foam quality was found to depend mostly on liquid velocity rather than gas velocity and is physically linked to foam type (continuous vs. discontinuous) and texture (fine vs. coarse). Distinct rheological behaviors also arose in the low- and high-quality foam regimes as a function of velocity. Foam flow was found to be strongly shear thinning in the low-quality regime where foam texture was fine and discontinuous. In the high-quality regime, the rheology was weakly shear thinning to Newtonian for coarsely textured foam and continuous-gas flow respectively. When all other variables were held constant, at ambient conditions, CO 2 foam was found to be weaker with also lower capillary pressures than N 2 foam and the differences in gas solubility is a likely explanation., (© 2023. The Author(s).)

The apparent viscosity of viscous heavy oil emulsions in water can be less than that of the bulk oil. Microfluidic flooding experiments were conducted to evaluate how alkali-surfactant-foam enhanced oil recovery (ASF EOR) of heavy oil is affected by emulsion formation. A novel phase-behavior viscosity map-a plot of added salinity vs. soap fraction combining phase behavior and bulk apparent viscosity information-is proposed as a rapid and convenient method for identifying suitable injection compositions. The characteristic soap fraction, [Formula: see text], is shown to be an effective benchmark for relating information from the phase-viscosity map to expected ASF flood test performance in micromodels. Characteristically more hydrophilic cases were found to be favorable for recovering oil, despite greater interfacial tensions, due to wettability alteration towards water-wet conditions and the formation of low apparent-viscosity oil-in-water (O/W) macroemulsions. Wettability alteration and bubble-oil pinch-off were identified as contributing mechanisms to the formation of these macroemulsions. Conversely, characteristically less hydrophilic cases were accompanied by a large increase in apparent viscosity due to the formation of water-in-oil (W/O) macroemulsions.

The injection of low-salinity brine enhances oil recovery by altering the mineral wettability in carbonate reservoirs. However, the reported effectiveness of low-salinity water varies significantly in the literature, and the underlying mechanism of wettability alteration is controversial. In this work, we investigate the relationships between characteristics of crude oils and the oils' response to low-salinity water in a spontaneous imbibition test, aiming (1) to identify suitable indicators of the effectiveness of low-salinity water and (2) to evaluate possible mechanisms of low-salinity-induced wettability alteration, including rock/oil charge repulsion and microdispersion formation. Seven oils are tested by spontaneous imbibition and fully characterized in terms of their acidity, zeta potential, interfacial tension, microdispersion propensity, water-soluble organics content and saturate-aromatic-resin-asphaltene fractionation. For the first time, the effectiveness of low-salinity water is found to positively correlate with the oil interfacial tension in low-salinity water. Oils with higher interfacial activity are found to respond more positively to low-salinity water. Moreover, cryogenic transmission electron microscopy images suggest that microdispersion is essentially macroemulsion, and its formation is an effective indicator - but not the root cause - of wettability alteration. The repulsive zeta potential for the rock and the oil in low-salinity water is found to be an insufficient condition for wettability alteration in carbonate minerals.

One of the most exciting areas in lithium ion batteries is engineering structured silicon anodes. These new materials promise to lead the next generation of batteries with significantly higher reversible charge capacity than current technologies. One drawback of these materials is that their production involves costly processing steps, limiting their application in commercial lithium ion batteries. In this report we present an inexpensive method for synthesizing macroporous silicon particulates (MPSPs). After being mixed with polyacrylonitrile (PAN) and pyrolyzed, MPSPs can alloy with lithium, resulting in capacities of 1000 mAhg(-1) for over 600+ cycles. These sponge-like MPSPs with pyrolyzed PAN (PPAN) can accommodate the large volume expansion associated with silicon lithiation. This performance combined with low cost processing yields a competitive anode material that will have an immediate and direct application in lithium ion batteries.