The development of alternatives to production of shale oil by the conventional mining/retorting approach has been a focus for considerable research by industry and government for a number of years. One of these, namely the production of oil from oil shale "in situ" or in place, offers many attractive features. The potential benefits to be derived from the commercialization of an in situ process are both economic and aesthetic. The most significant of these is the absence of the costly and unavoidably disfiguring mining and waste disposal functions associated with a mining/retorting operation. Other potential benefits include: lower research and development costs; lower capital cost of the initial operation; the use of conventional oil field equipment; and lower labor cost per unit of production.