Production of shale oil by in-situ retorting of oil shale

A method of producing shale oil from an in-situ retort in an underground oil shale deposit comprising:

• (a) excavating a room in the shale deposit, said room conforming in cross section to the retort and having a volume at least as large as the minimum void space in a mass of rubblized oil shale blasted from the oil shale deposit and random free falling to fill open volume the size of the desired retort;
• (b) drilling a plurality of substantially vertical shot holes through the oil shale overlying the room, said shot holes extending upwardly through the shale overlying the room at least to approximately the upper end of the desired retort;
• (c) after completion of step (a), initiating rubblization of the shale by detonating an explosive charge in the shot holes near the lower end thereof to fragment oil shale overlying and adjacent the room and cause random free fall of the fragments into the room to form a random-filled rubblized mass of oil shale therein with an open space between the rubble and overlying unfragmented shale;
• (d) repeating the detonation of explosive charges at successively higher levels in the shot holes to fragment the shale adjacent the open space and cause random free fall of fragments of oil shale formed by each detonation through open space onto rubblized oil shale in the room underlying the unfragmented oil shale until a random-filled rubblized in-situ retort of the desired height is formed, the time between successive detonations being adequate to allow movement of shale broken by a detonation sufficiently to avoid interference by particles of shale broken by a later or earlier detonation whereby there is random free fall of the shale particles onto the upper surface of the shale in the room;
• (e) passing a retorting gas downwardly through the in-situ retort to heat oil shale in the retort and release shale oil therefrom;
• and
• (f) delivering shale oil from the in-situ retort to the surface.