Fifth Annual International High Level Radioactive Waste Management Conference
Las Vegas, Nevada, April 1994, pp. 2160-2167
American Nuclear Society, La Grange Park, Ill., 1994

Estimating two-phase hydraulic properties by inverse modeling

Stefan Finsterle and Karsten Pruess

Lawrence Berkeley National Laboratory, Earth Sciences Division
University of California, Berkeley, CA 94720


Abstract. Disposal of high-level nuclear waste in geologic formations requires characterizing the hydrogeologic conditions at the potential site. This involves extensive data inter-pretation from laboratory and field experi-ments which are being performed on different scales. Two-phase flow processes are relevant if the potential site is located in the unsaturated zone, but they are also studied for repositories beneath the water table if the waste packages generate significant amounts of free gas. Numerical models are used for predicting the system behavior under different hydrologic and thermal loads. Parameters appearing in the governing equations are usually difficult to measure and subject to systematic errors. The strategy chosen to obtain model-related formation parameters is to calibrate the numerical model using observations of the system response. The practical relevance of parameter estimation for site characterization and design of field and labo-ratory experiments motivated the development. The purpose of this paper is to present the concept of parameter estimation, and to demonstrate the use of the proposed method for the interpretation of hydraulic tests conducted under two-phase flow conditions.