The goal of this project is to develop a systematic and cost-effective approach to the design and interpretation of Partitioning Interwell Tracer Tests (PITT) to infer hydrocarbon saturation distribution in highly heterogeneous and fractured reservoirs. The key elements of our approach are a very fast streamline-based flow simulation technique and a rapid and novel history matching technique that exploits an analogy between streamlines and seismic ray tracing. Our approach will be orders of magnitude faster than conventional history matching, resulting in significant savings in computation time and manpower. The integrated approach will take advantage of the dense spatial coverage of the seismic data for static modeling and the strong coupling of interwell saturation variations to partitioning tracer response. The outcome of this research will be a systematic approach to the design and interpretation of tracer data and practical, PC-based, software tools providing high-resolution saturation estimates in the interwell region by combining well log, seismic, and partitioning tracer data.