Understanding Fluid Flow in Rocks

November 19th (Tuesday), 6 p.m., Teton Co. Library Auditorium – Open to Public. Presentation: Understanding Fluid Flow in Rocks , Presented by Saman Aryana, University of Wyoming

Fluid flows in subsurface formations, e.g., rocks, occurs mainly at the scale of the pore spaces. These flow pathways are often micrometer in size and have complex geometries depending on the type and nature of the rock. Understanding these flow processes and developing accurate descriptions for them figure prominently in a wide range of applications, including underground CO2 storage, groundwater contaminant remediation, and petroleum reservoir engineering. In this talk, I will focus on visualization techniques, such as microfluidics, that enable researchers to better observe flow in permeable media.

Microfluidics is a platform to study fluids at the scale of micrometers. It enables precise control with applications in biomedical and chemical engineering, fluid dynamics and interfacial science. In this talk, we will discuss microfluidics in the context of subsurface applications such as Improved Oil Recovery and Carbon Capture Utilization and Storage. Specifically, we will examine fabrication of microfluidic devices and their contribution to an improved understanding of nanoparticle-stabilized CO2 foam, the impact of heterogeneities on flow dynamics, the evolution of flow instabilities, and flow regime as a function of viscosity ratio and capillary number.

Our microfluidic devices feature a porous medium that is a two-dimensional representation of a sandstone. The mask of the porous medium used in the fabrication process is developed based on a mosaic of Scanning Electron Microscopy images of a thin section of the target formation. Pore spaces are connected based on throat size distribution data obtained from a mercury intrusion experiment. The resulting complex network of channels is representative of the geometries and connections of the three-dimensional sample of the formation. The map of the medium is then etched onto a borosilicate substrate using a photo lithography technique, and the etched substrate was thermally bonded to a blank wafer to create the microfluidic device.  Such glass microfluidic devices enable visual observation of fluid flow under high-pressure conditions without using a pressure cell. Unlike microfluidic devices made from PDMS (which is a silicon-based organic compound) the pore structure of the glass chip does not change during fluid flow due to pressure and parameters such as flow rate and fluid properties, and contact angles may be investigated reliably. This platform is coupled with a high-resolution monochromatic camera, enabling the capture of images of the entire porous medium, with approximate dimensions of 1.5 to 3 inches in both length and width, while preserving the resolution required to discern features as small as 10 micrometers.

My research group and other researchers at the University of Wyoming are using visualization techniques to study physical systems relevant to energy, water and climate change, which will continue to become more critical as we move into the future.