In situ retorting of oil shale with air, steam, and recycle gas

摘要

A flame front is ignited and passed through an underground oil shale retort to produce shale oil. The flame front is supported by a specially blended feed gas consisting essentially of air, steam and retort off gases. Product yield and quality are increased by varying the volumetric ratio of air, steam and retort off gases in the feed gas during retorting in proportion to the oil yield, or the relative richness, leanness and kerogen content of the oil shale being heated by the flame front, or in proportion to the amount of carbon residue on the retorted shale being combusted.