COUPLED SEISMIC AND TRACER TEST INVERSION FOR AQUIFER PROPERTY CHARACTERIZATION

Seismic and tracer test data can be combined to estimate the spatial p atterns of aquifer properties. We present an algorithm that estimates the geometry of large-scale lithologic zones, the effective hydraulic conductivities and seismic velocities for these zones, and the effecti ve small-scale dispersivity. The heart of this algorithm is our split inversion method, which extracts the geometry of lithologic zones from an estimated seismic velocity field. This method determines the zonat ion that best matches multiple types of data, such as seismic travel t imes and tracer concentrations. Although the current implementation of the algorithm uses only cross-well seismic travel times and tracer co ncentrations, the algorithm could incorporate other data types that ar e sensitive to changes in large-scale lithology. We demonstrate the ap proach for two synthetic sandy aquifers, one with interbedded clay len ses and another with interbedded silt and gravel lenses. These example s differ in the uniqueness of the relationship between seismic velocit ies and hydraulic conductivities. For these examples our algorithm suc cessfully maps interwell heterogeneities and accurately estimates hydr aulic and seismic parameters.