Experimental Approach of Percolation in Porous Rocks: Threshold and First Infinite Cluster
Abstract
Wood's metal is used as an alternative to mercury in rock pore network invasion. Despite the necessity of heating for invasion (melting point circa 70°C), it presents the advantage to be frozen at any step of the invasion process. Preliminary works (Darot and Reuschle, 2000, 2001 submitted) on Wood's metal wettability were performed to determine the product γx cos θ (γ is the surface energy and θ the interfacial contact angle) and study the influence of solid-liquid relative velocity, solid nature, and surface roughness on this product. At low velocities, in the quasi-static domain, the following value is used : γ x cos θ = 0.440+/-0.030 N/m. A special cell was designed to perform step by step drainages with increasing pore pressures. 50 mbar pressure increments were used to reach percolation threshold. Wood's metal pressure was recorded when the first drop appeared to the unaided eye, on top of the specimen. This breakthrough pressure (percolation threshold) is used to derive the corresponding percolation throat diameter. Next Wood's metal temperature was dropped, allowing it to freeze into the invaded network. Then the connected network at the percolation threshold can easily be visualized through X-ray radiography. The morphology of the resulting shadowgraph provides a rapid diagnosis of the sample homogeneity. Our results on various rocks, including Berea sandstone and Indiana limestone, are encouraging and in fair agreement with published data.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFM.H51D0352D
- Keywords:
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- 5100 PHYSICAL PROPERTIES OF ROCKS;
- 5112 Microstructure;
- 5114 Permeability and porosity;
- 5139 Transport properties