IMPROVED GLASS MICROMODEL METHODS FOR STUDIES OF FLOW AND TRANSPORT IN FRACTURED POROUS-MEDIA

Microscale experiments can provide mechanistic insights into larger-sc ale flow and transport phenomena. Studies of the microscale mechanics involved in preferential how in general, and unsaturated fast flow pat hs in particular, require the development of new experimental techniqu es. A new method for constructing glass micromodels has been developed which permits direct visualization and quantification of flow and tra nsport phenomena in fractured porous media. In the fracture-matrix mic romodels a sequential etching procedure was developed in order to prov ide the necessary contrast of depths between matrix pores and fracture apertures. This high contrast in etching depths ensures that very dif ferent capillary properties are associated with micromodel ''fractures '' and ''matrix'' blocks. Improved techniques were also developed for reducing the pore sizes of the matrix to a natural fine-grained sandst one pore scale, The improved micromodel pattern designs allow for prev iously unachievable control of boundary conditions. Various saturated and unsaturated fracture flow and transport processes can be visually and quantitatively studied with these micromodels, A method for direct ly measuring pore-scale flow velocity distribution through tracing tra jectories of suspended fluorescent microspheres was also developed, Ex amples of applications include measurements of velocity profiles in fr actures, imbibition, fracture-matrix transient flow, and matrix diffus ion. In general, the improved micromodel method provides a unique tool for exploring some of the previously unrecognized flow and transport processes in fractured porous media. This research is directed at prov iding microscale explanations to some currently unresolved flow and tr ansport issues important in predicting the larger-scale flow processes .