Two large cavities, one in each of two conventional well bores, were created in two wells at a depth of 1330 feet in Antrim oil shale on Dow's property in Sanilac County. Ten and one-half tons of a modified Dow MS-80 explosive were loaded in each well and detonated. The resulting blast created fractures cut at least two hundred feet from the center of the well system. Whether this fracturing is sufficient to be able to carry out in situ partial combustion is as yet unproven.