Applicability of Analytical Models to Single-Well Permeability Tests in Deep and Hydraulically Tight Geological Formations

In situ permeability tests are crucial in hydraulic characterizations of geological formations for the disposal of radioactive nuclear waste. As has been done in most countries where geological disposal of high-level radioactive wastes has been discussed, single-well permeability tests are generally conducted in a preliminary stage of selecting a site where groundwater exists. To determine accurately hydraulic parameters, specifically hydraulic conductivity and specific storage, from single-well permeability tests, it is worth reexamining analytical solutions for modeling test data derived from deep and hydraulically tight (hydraulic conductivity is typically less than 10(-8) m/s) formations. In hydraulically tight formations, the radius of influence due to a single-well permeability test is not expected to be large, which should be taken into consideration when using the test results. The present paper revisits three major single-well permeability tests, i.e., the pressure pulse, constant head, and constant flow rate tests, and examines the features of natural formations incorporated into the analytical models, such as hydrogeological boundaries, property alterations around a borehole and anisotropy. The radius of influence in a hydraulically tight formation is examined for the three major single-well permeability tests by a numerical approach.