HELIUM TRACER STUDIES TO CHARACTERIZE UNDERGROUND FLOW PATHS.

Helium tracer data was outlined at the LETC Hanna IV UCG site in Wyoming during reverse burn linking and throughout the gasification phase. Void volumes are compared to those obtained from material balance calculations as well as from other tracer test data. A qualitative description of the flow path and how it changes during the UCG test is presented. Helium tracer studies were also made at the Rock Springs in situ oil shale retort site in order to determine the flow distribution in LETC's six-spot well pattern prior to ignition. The tracer test system hardware and data interpretation techniques are discussed.