| abstract |
A processing zone advances through a fragmented permeable mass of particles containing oil shale in an in situ oil shale retort in a subterranean formation containing oil shale. The retort has an effluent gas passing therefrom. The effluent gas contains a constituent which is formed, by advancement of the processing zone through the fragmented mass, from a precursor contained in the formation. To determine the locus of the processing zone, formation is assayed at selected locations in the retort for content of the precursor before processing the selected locations, and effluent gas from the retort is monitored for concentration of the selected constituent. n For example, kerogen can be the precursor and effluent gas from the retort can be monitored for the concentration of methane produced by retorting of kerogen in the oil shale. |