The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 17, 1984
Filed:
Jul. 09, 1981
Thomas E Ricketts, Grand Junction, CO (US);
Occidental Oil Shale, Inc., Grand Junction, CO (US);
Abstract
An in situ oil shale retort is formed by excavating a lower level void adjacent the bottom boundary of a retort site in a subterranean formation, leaving a zone of unfragmented formation within side boundaries of the retort overlying the void. At least a portion of the overlying zone is explosively expanded downwardly towards the void in a plurality of lifts. Vertical columnar explosive charges are placed in each lift and detonated in a single round with a time delay between successive lifts sufficient for formation of the first lift to move out of the way and not interfere with initial explosive expansion of formation in the next successive lift. Preferably, the explosive charges in a second lift are detonated after detonation of explosive charges in a first lift with a time delay in the range of from about five to thirty milliseconds per foot of burden distance of the charges in the second lift. When plural lifts above the first lift are explosively expanded, it is preferred that the time delays progressively increase from the bottom up.