An important fraction of world supplies of hydrocarbons and fresh groundwater occurs in geologic formations with fractures cutting through a tight matrix. It is understandable that considerable effort has been put into efforts to understand how these fluids are stored and transmitted through the pore spaces along fractures. Although commonly viewed as rigid conduits, fractures in rock are actually somewhat compliant, gapping open in response to even modest increases in pressure and shrinking closed when pressure drops. Measuring and interpreting both displacement and pressure while pumping is the essence of a hydromechanical well test. Measurements of both pressure and displacement can be used to determine the storativity of an aquifer using data from a pumping well alone; conventional methods require using an observation well to estimate storativity. The purpose of this project is to develop and refine field techniques for conducting and analyzing hydromechanical well tests. The project is motivated by efforts to address aquifer characterization, well performance, joint formation, and Earth tides. The intellectual merit of the proposed project includes advances in three primary arenas: a) theoretical analyses of fracture hydromechanics, b) field techniques and instrumentation, c) field applications and hypothesis testing at sites underlain by fractured rock aquifers. The project will produce innovations in portable extensometers that can be used during well tests, and new theoretical analyses will be developed for predicting and inverting displacement and pressure signals obtained during hydromechanical well tests. It is possible to invert an axisymmetric model of coupled fluid flow and deformation in fractures to estimate heterogeneities at some distance from the pumping well. Hydromechanical well tests offer promise, both as a technique that stands alone and as one that is integrated with other methods in the characterization of fracture rock aquifers. This project will provide insights that cut across fields related to groundwater production and remediation, geothermal energy, oil and gas production, disposal of hazardous wastes by deep well injection, disposal of nuclear wastes in repositories, earthquake and tsunami prediction, landslide mechanics, rock mechanics, and a variety of other disciplines concerned with fluid flow and deformation in fractured rock. The project will initiate an innovative educational partnership between Clemson and Georgia Tech that will provide unique opportunities for training students at all levels in geomechanics and hydrogeology. Furthermore, we will initiate a program to enable middle school earth science teachers each summer to learn about well testing and bring well testing exercises to their students.
