RIO-BLANCO EXPERIMENT - ITS OBJECTIVES, DESIGN, AND EXECUTION

Project Rio Blanco is a joint government-industry experiment utilizing nuclear explosives to stimulate gas production from thick, relatively impermeable, gas-bearing lenticular sand and shale sequences. Three 30-kt explosives spaced vertically in a single wellbore at intervals of 390 and 460 ft. were detonated simultaneously on May 17, 1973. No significant adverse effects were experienced, and damage resulting from ground motion was as predicted. The initial re-entry into the upper explosive region indicates that coalescence of the top cavity and fracture region with the lower ones did not occur as expected. Re-entry into the bottom cavity indicated that similarly, communication does not exist between the lower two chimneys. All indications are that yields were as predicted, and to date there is no valid explanation as to the lack of intercommunication between the fracture regions of the three explosives. Production test data from the top chimney indicated a reservoir capacity of only 0. 73 md-ft, which is 6 to 10 times lower than expected. Subsequent testing lends further evidence that, although significant stimulation most surely occurred, the gas contained in the sandstones was much less than had been originally anticipated.