Geomechanical Characterization of Rock Core from the Proposed FORGE Laboratory on the Eastern Snake River Plain, Idaho

Abstract

This paper presents the results of an experimental program for characterization of cores from two wells drilled in the Eastern Snake River Plain, Idaho, near a proposed FORGE EGS Laboratory location on the Idaho National Laboratory. The geological and geothermics features of the area make the Eastern Snake River Plain a promising target for an EGS system. The cores tested were obtained from varying depths ranging from 1,000 - 3,150 m. Rock types present are mainly low permeability rhyolite tuffs, rhyodacites, basalts and lava deposits. The tuffs have been hydrothermally altered in places and both the tuffs and lava deposits have been found to decrease in permeability with increasing stress (depth). The retrieved cores from three wells were plugged to obtain core plugs of varying diameters which were then used for geomechanical characterization including velocity data, elastic modulus, Poisson’s ratio, permeability (with and without fractures), tensile strength, Mohr-Coulomb envelope, etc. These as well as other tests help develop a drilling and stimulation program.