Oil shale retorting from a high porosity cavern

A method of producing hydrocarbonaceous liquids from subterranean kerogen-containing oil shale formations covered by an overburden comprising sequentially (a) penetrating the oil shale deposits with at least two well bores, designating a first well bore and at least one second well bore;

• (b) fracturing the oil shale deposits so as to provide communication between the first well bore and the second well bores in a lower vertical portion thereof:
• (c) igniting the hydrocarbonaceous deposit at a point near the first well bore in the presence of a free oxygen-containing gas;
• (d) introducing through the first well bore a free oxygen-containing gas to the ignited point of the oil shale deposit to effect thermal decomposition of the hydrocarbonaceous material therein and to propagate a combustion zone through the fractured communication area between the first well bore and the second well bore, thereby forming a region of combusted shale between the first well bore and the second well bore;
• (e) allowing the combustion to continue until a sufficient volume of combusted shale has been formed between the two well bores;
• (f) then jetting an aqueous liquid into and through the combusted and spent shale zone to remove the mineral residue remaining from the combustion of the kerogen in the oil shale;
• (g) positioning conventional explosives in the oil shale deposit in the vicinity of the washed out cavity formed in step (g) such that the energy generated upon detonation of the explosive interacts with and extends into the cavity;
• (h) detonating the explosives thereby causing the oil shale deposit to be fragmented and to collapse into the cavity creating a rubblized zone of relatively high permeability and porosity;
• (i) then igniting the oil shale by heating and introducing a free-oxygen-containing gas at the top of the rubblized zone by way of one of the well bores to combust and retort the rubblized carbonaceous deposit.