CO₂ Mineralization in Basalts: In-situ mineralization of CO₂ in basaltic geologic formations is a promising technology to remove anthropogenic CO₂ emissions on a large scale. However, the physics and chemistry of basalt/water/CO₂ system under high-pressure high temperature (HPHT) geologic conditions are far from well-understood. In this project we investigate how water-saturated basaltic rock interacts and reacts with supercritical CO₂ under controlled HPHT conditions. Advanced techniques, such as NMR, confocal imaging, SEM-EDS, and µ-CT, will be utilized to quantify the change in basalt structures, surfaces, and mineralogy due to reactions. As supercritical CO₂ percolates into the rock, it contacts, displaces, and acidifies resident water, which then dissolves silicate minerals, releasing divalent cations, such as Ca²⁺, Mg²⁺, Fe²⁺, to precipitate the carbonate ions in water. This dissolution/precipitation process couples with fluid transport and surface processes confined in the micro/nanopores of the rock, leading to evolving pore geometry/topology and precipitate distribution/morphology/mineralogy. In addition, production of noncarbonate secondary minerals competes for reactive surfaces and slows the carbonation rates. Our research may help establish how these micro- and nano-scale processes map to overall carbonation rates under HPHT conditions, which is critical for successful future projects of CO₂ storage in basalts. Jianping Xu, Yiqiao Song, Negar Nazari, Wenyun Wang

Compression Induced Syneresis of Fibrous Oil-In-Hydrogel Emulsions: Fibrous hydrogels are highly porous and have a large capacity to deform when strained due to the poor retention of water within the gel. When compressed, gels such as sodium myristate (SM) and fibrin can lose up to 95% of their mass due to syneresis. SM gels that are supplemented with a silicone oil (SO) emulsion display a maximum in the stress-strain curve (Πm) that occurs at ϵ=1-ϕ0, where ϕ0 is the initial volume fraction of oil. At this strain, almost all the water has been squeezed out of the gel, and the oil droplets coalesce to form a quasi-continuous phase that can then synerese from the gel after further compression. This may have important consequences for the material toughness. The height of the maxima depends on ϕ0, the radius of the oil droplets rd, and the pore size of the SM network rp. There is evidence that the scaling behavior of Πm is due to rearrangements of the droplets inside the pore. Smaller pores (or larger droplets) isolate the droplets, leading to jamming behavior and large stresses on some of the droplets. Larger pores (or smaller droplets) allow the droplets to rearrange under compression leading to more distributed stresses on the droplets and a large Πm. Benjamin, Thorne

Fluid expansion-driven hydraulic fracture: Fluid-driven fractures occur ubiquitously in subsurface rocks in natural and engineering processes, such as earthquakes and hydraulic fracturing. Hydraulic fracturing involves injecting a high-pressure mixture of water, sand, and chemicals into a wellbore, fracturing the rock, and increasing the flow capacity within the rock. We visualize the hydraulic fracturing process using a high-speed camera at a temporal resolution of micron-seconds. In the experiments, fracking fluid is injected by a high-pressure syringe pump into a small, vertical hole at the center of a 3D-printed, transparent PMMA cylinder sample. A penny-shaped fracture is induced from the notch at the bottom of the small hole and moves toward the cylinder edge. A continuous video is recorded by a high-speed camera from the bottom of the cylinder. The fracture propagates in a stick-break pattern. In a break event, nucleation initiates at one or more locations near the crack tip and propagates in the tangential direction until covers the entire circle. The fluid front lags the crack front and the lag length increases with fracturing fluid viscosity when Newtonian fluid is used. However, when a high molecular weight polymer is used, the lag length is small regardless of fluid viscosity. For different polymers, the lag length increases as the polymer molecular weight decreases. Yujing Du

Enhancing Oil Recovery by Controlling Velocity Distribution in Heterogeneous Porous Media: Heterogeneity within porous media structures is a common feature across various natural applications. In the field of petroleum engineering, for instance, oil fields often consist of rocks with diverse permeabilities, randomly interconnected with rocks of varying sizes and shapes. The challenge arises when water, used to displace oil, consistently follows paths of least resistance through high-permeability areas, limiting oil recovery. To gain control over water flow within these porous structures, we devised a two-layer transparent 3D glass capillary device. This innovative system employs glass beads to accurately mimic the natural heterogeneity of porous media, allowing us to visualize the process through confocal microscopy. Additionally, we introduced a polymer gel to selectively block high-permeability regions, autonomously adjusting the overall permeability. This adjustment in flow dynamics enables us to control flow velocity, facilitating uniform water distribution throughout the device. Consequently, we are empowered to study and understand the intricate flow behaviors and mechanics within heterogeneous porous media structures. Tianlei He

Microfluidic Experiments for Hydrogen Storage in Porous Media: Hydrogen is considered as a clean energy carrier for the future, characterised by its lack of carbon emissions. To foster the development of the hydrogen economy and address the intermittent nature of renewable energy resources, substantial storage capacity for hydrogen is crucial. Porous subsurface geological formations, such as depleted gas reservoirs and aquifers, offer significant storage potential for hydrogen. However, our current understanding of how hydrogen flows within these porous media and how it interacts with rocks and fluids, especially during cycles of injection and withdrawal, remains limited. Microfluidic experiments play a fundamental role in elucidating the underlying mechanisms governing hydrogen flow at the pore scale and the hysteresis observed in trapping and reconnection during cyclic injections. Our research involves a series of drainage-imbibition experiments, which allow us to visualize and analyse the multiphase flow of hydrogen and water within the porous medium, including variations in residual phases throughout these cycles. P. Mostaghimi, N. Nazari, D.A. Weitz

Hydraulic Fracture of Brittle Gels: Hydraulic fracture of oil and natural gas bearing rocks has rapidly grown over the last two decades into an integral tool for the extraction of these resources.  It has proven to be both very economically favorable as while also being cited as responsible for significant ecological damage.  In order to address both its efficacy and safety, one must understand more about the factors that control the growth of these hydraulic fractures that cannot be observed in nature.  Our goal is to study the behavior and control mechanisms of fractures produced in tough hydrogels where we can observe with far greater spatial and temporal accuracy than similar experiments performed on rocks.  By measuring the basic physics that governs hydraulic fracture propagation we hope to make oil and natural gas exploration both safer and more efficient. Will Steinhardt

Flow of multiple immiscible fluids in porous media: I study the dynamics of flow of multiple immiscible fluids in a 3D model porous medium. Using confocal microscopy we are able to visualize multiphase flow within the porous media. I am interested in understanding the underlying physical phenomenon that results in enhanced imbibition of the non-wetting phase due to flow of  Non-Newtonian wetting phase, a shear thinning polymer solution. Shima Parsa