Fracturing of Oil Shale by Treatment with Liquid Sulfur Dioxide

Development of oil shale deposits as sources of fuels, lubricants, and chemical feedstocks is being considered as an alternative to present reliance on conventional petroleum reserves. Procedures, advantages, and disadvantages for mining/surface processing and for in situ retorting have been widely discussed ( 1, 2, 3 ). In the former approach, crushing of the shale is essential for efficient oil recovery. As a result of tests with a variety of mechanical crushers ( 4 ), it is apparent that the effectiveness of mechanical crushing is limited by the characteristics of the shale. A slab-forming tendency allows large pieces to pass through many conventional crushers. The resilience and slippery nature of the shale limits the effectiveness of mechanical impact. Furthermore, shale abrasiveness and a tendency for the shale to adhere to crusher surfaces causes maintenance problems with crushers. In situ retorting is enhanced by fracturing with explosive charges or expansion of existing fractures with fluids