Full-scale borehole sealing test in anhydrite under simulated downhole conditions. Volume 1

A full-scale borehole sealing test was conducted in anhydrite. The test was performed under the simulated in situ stress (4.83 MPa [700 psi] and temperature (300C) of a theoretical deposit overlying a nuclear waste repository. The borehole sealing material was an expansive grout formulated by the US Army Engineer Waterways Experiment Station, Vicksburg, Mississippi, under contract to the US Department of Energy. To evaluate and better understand the expansive nature of the grout, in situ pressure and temperature versus time histories were measured during the 29-day curing period and subsequent full-scale flow tests. Post-test microscopic and laboratory permeability tests were conducted on the grout and anhydrite. Data indicate the grout exothermic reaction was low (60C), with the expansive stresses approaching 2.55 MPa (370 psi) near the center, and 3.8 MPa (551 psi) at the interface, prior to transducer failure on day 17. The full-scale flow test conducted at the conclusion of the 29-day curing period resulted in large-scale flow. Megascopic post-test examination of the grout revealed channeling and apparent dissolution at the grout-anhydrite interface. Microscopic examination revealed voids within the grout, with laboratory tests showing a permeability of 10-6 darcys. Numerous fractures were evident in the anhydrite