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Measurements of Capillary Pressure-Saturation Relationships for Silica Sands Using Light Transmission Visualization and a Rapid Pseudo Static Methods
Citation:
BOB, M., M. BROOKS, L. Chen, T. Kibbey, AND A. L. WOOD. Measurements of Capillary Pressure-Saturation Relationships for Silica Sands Using Light Transmission Visualization and a Rapid Pseudo Static Methods. Presented at 2008 Fall Meeting of the american Geophysical Union, San Francisco, CA, December 15 - 19, 2008.
Impact/Purpose:
The objective of this research was to implement the innovative technique of light transmission visualization (LTV) to investigate the Pc-S relationships for porous media, and compare the results to an independent technique
Description:
Measurement of water saturation in porous media is essential for many types of studies including subsurface water flow, subsurface colloids transport and contaminant remediation to name a few. Water saturation (S) in porous media is dependent on the capillary pressure (Pc) which, in turn, depends on the interfacial tension between wetting and non-wetting phases, the pore size distribution of the porous material as well as the contact angle between fluids and porous media. Traditionally, measurements of the Pc-S relationship were carried out using pressure cells but these methods can be very time consuming. The objective of this research was to implement the innovative technique of light transmission visualization (LTV) to investigate the Pc-S relationships for porous media, and compare the results to an independent technique, namely a rapid pseudo-static automated method that was recently developed by Chen et al. Two dimensional (2-D) chambers constructed of two glass plates were packed with either 20/30 or 40/60 silica sand and then fully saturated with water. Images of the entire 2-D chambers were captured using a charge-coupled device (CCD) camera and analyzed pixel by pixel to determine air and water saturation in the porous media. Variable saturation of water and air across the height of the chamber was dictated by controlling the capillary pressure of the fluids. The primary drainage curve, main imbibition curve and secondary drainage curve were all measured, for the first time, using LTV and the results were compared to the results obtained by the rapid pseudo-static method. Overall, there was good agreement between the results of the two methods and variation in air entry pressure that was calculated based on Brooks-Cory model was within 2 cm for the sand sizes tested. Both techniques are capable of providing high spatial resolution data for the Pc-S relationships.
