True in situ methods to process oil shale, which by definition require no mining and depend on wellbores for access to the underground formation, will be successful only if technique are available to transform the normally very tight oil shale seems into rubble beds that are sufficiently porous and permeable and composed of suitably sized fragments to permit effective retorting operations to be conducted. Prior experimental efforts to create such beds in comparatively deep formations, where significant void cannot be introduced by explosively lifting the overburden, have in nearly all cases employed either the wellbore springing of hydraulic/explosive fracturing concept. Only very limited success has ever been achieved in these efforts, In this paper, reasons for the lack of success are identified. For the wellbore springing concept, the inherent cylindrical geometry is the primary difficulty in that it leads to small fractured zones because of rapid stress pulse attenuation, and also to regions of residual compressive stress around the wellbore, which restrict fluid flow and hinder void redistribution. Major difficulties with the hydraulic/explosive fracturing concepts are that many important operations cannot be controlled and that regions of enhanced permeability are formed only in the immediate vicinity of explosive filled hydro fractures. The future success of true in situ processing depends on the introduction of void prior to the blasting operation and development of explosive in a geometry that will ensure distribution of the void.