Publications Details
Petrographic and X-ray diffraction analyses of selected samples from Marker Bed 139 at the Waste Isolation Pilot Plant
The Waste Isolation Pilot Plant (WIPP) is located 660 m underground in the Salado Formation which consists of thick, horizontally bedded pure and impure salt and thin, laterally continuous clay and anhydrite interbeds. The Salado Two-Phase Flow Laboratory Program was established to provide site-specific-two-phase flow and other related rock properties to support performance assessment modeling of the WIPP repository. Owing to their potentially significant role in the hydrologic response of the repository, the program initially focused on the anhydrite interbeds, and in particular, on Marker Bed 139 (MB 139), which lies approximately 1 m below the planned waste storage rooms. This report synthesizes petrographic and X-ray powder diffraction studies performed to support the Salado Two-Phase Flow Laboratory Program. Experimental scoping activities in this area were performed in FY 1993 by three independent laboratories in order to: (1) quantify the mineral composition to support laboratory studies of hydrologic properties and facilitate correlation of transport properties with composition; (2) describe textures, including grain size; and (3) describe observed porosity. Samples from various depths were prepared from six 6-inch diameter cores which were obtained by drilling into the marker bed from the floor of two separate rooms. The petrographic analyses are augmented here with additional study of the original thin sections, and the pore structure observations are also examined in relation to an independent observational study of microcracks in Marker Bed 139 core samples performed in FY 1994 by the Geomechanics Department at Sandia National Laboratories.