3661423 is referenced by 350 patents and cites 3 patents.

Subterranean carbonaceous deposits, such as oil shale, are conditioned for in-situ recovery of carbonaceous values by limited undercutting over a large area to leave an overlaying deposit supported by a multiplicity of pillars, if necessary, then removing the pillars and expanding the overlaying deposit to fill the entire void with particles of a uniform size, porosity and permeability. Communication is then established with the upper level of the expanded deposit and a high temperature gaseous media which will liquify or vaporize the carbonaceous values is introduced in a manner which causes the released values to flow downward for collection at the base of the expanded deposit. Convenient media are hot flue gases created by igniting the upper level of the expanded carbonaceous deposit and forcing a flow of hot gases downward through the expanded deposit.

Title
In situ process for recovery of carbonaceous materials from subterranean deposits
Application Number
05/010,871
Publication Number
3661423
Application Date
February 12, 1970
Publication Date
May 9, 1972
Inventor
Garret Donald E
Assignee
Occidental Petroleum Corporation
IPC
E21b 43/26
E21B 43/247
E21B 43/16
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