"The Hanna II in situ coal gasification experiment was conducted by the Laramie Energy Research Center during 1975-76. As part of this experiment, Sandia Laboratories designed, fielded, and evaluated seven instrumentation techniques and several variations of them. These belonged to two general classes: (a) diagnostic techniques (thermal, in-seam gas sampling and pressure, and overburden tilt and displacement) to obtain data for process characterization and (b) remote monitoring techniques (electrical, passive acoustic, and induced seismic) which are being developed to provide a continuous, real-time map of the in situ process which would be used in a process control system. Assessments of these techniques have been made with respect to their feasibility, information obtainable and future development and applications; in general, very positive assessments were obtained. Extensive thermocouple arrays, which incorporated special branched circuitry for data validation, provided the most detailed characterization of in situ coal gasification yet obtained. The feasibility of in-seam gas sampling and pressure measurements was demonstrated and composition changes due to the advancing reaction front were detailed. The thermocouple circuits and gas sampling and pressure canisters are part of a diagnostic well specification now under development for general in situ applications. Promising results were obtained for the remote monitoring techniques. Two different electrical configurations were employed: direct excitation electrical potential (DEEP) and a modified Schlumberger (MS) technique. Contour maps of potential data from a surface array showed the location and movement of the reaction at 300 ft depth. Mapping the source of process-related acoustic signals was shown to be feasible. These signals originate in the overburden and are related to areas of extensive gasification and coal removal. Borehole-to-borehole induced seismic techniques were able to delineate the advance of the gasification process."