MULTISCALE IMAGING OF WETTABILITY USING IN SITU X-RAY MICROSCOPY (Invited Presentation)

Over the last 20 years, the development of high resolution pore scale imaging techniques has transformed our ability to characterize the tiny tortuous pathways which dominate the nature and character of the flow of fluids through the subsurface. What was principally a tool for academic research into the fundamental science of flow displacement has now developed into an increasingly used service sector for the Oil and Gas industry, and has much (and significant) application in fields as wide as nuclear energy storage and geologic carbon storage. While much progress has been made, significant challenges remain, principal of these challenges are those of process and scale.

Pore scale problems involve complex multiphysical processes which direct imaging and modelling cannot always simply address. Their investigation frequently requires direct experimental in situ investigation to acquire fundamental petrophysical properties inaccessible to any other technique – one such property not directly accessible through other techniques is that of wettability and contact angle. We will showcase the capability of such in situ techniques to characterize the distribution in wettability in a complex mixed wet carbonate system, showcasing how wettability, and so local microfluidic behavior is modulated by macroscopic lithological heterogeneity. First the sample is imaged at low resolutions, before being classified into multiple lithologies using supervised machine learning techniques, which was then used to define locations for mechanical sample extraction. These samples were then loaded into an in situ flow rig, where oil and brine were injected in phases of drainage and imbibition respectively. Samples taken from the high porosity lithology oolitic packstone were shown to be oil wet, whereas samples taken from the low porosity oo-bio wackestone were shown to be water wet. This modulation of local microfluidic behavior by macroscopic geological heterogeneity show both how complex subsurface behavior can be, and also how, by using state of the art multiscale imaging techniques, we can understand and characterize such behavior.