Abstract

Wagon Wheel is a project planned to stimulate gas reservoirs of the Pinedale Anticline by means of nuclear explosives. The Pinedale Field, located in the northern portion of the Green River basin of southwest Wyoming, is potentially productive from nearly 10,000 feet of lower Fort Union, Lance-Lewis, and Mesaverde equivalent sandstones. Attempts to produce the field conventionally have proved uneconomical due to low permeability.

The first nuclear stimulation experiment was Gasbuggy, in northwest New Mexico, detonated in 1967 using a 29 kiloton explosive. Technical questions answered by Gasbuggy resulted in the program at Wagon Wheel, which is an actual attempt at economic use of nuclear energy.

Wagon Wheel No. 1 was drilled to 19,000 feet to evaluate the entire Mesaverde section. Gas was detected on mud logging equipment throughout the basal Fort Union, Lance-Lewis and Mesaverde, below the top of the gas reservoir at 7,972 feet. The well has been plugged back to 11,700 feet as a possible emplacement hole in which five 100 kiloton explosives will produce a chimney from 9,000 to 11,650 feet. Reserves in this interval are calculated at 207 billion cubic feet of gas in place per square mile.

Extensive logging, coring and testing have been carried out in the program, including special logs for rock mechanics study. Cores were compared to Gasbuggy with regard to rock strength, shear behavior and potential fracture formation.

Two special wells in addition to the Wagon Wheel No. 1 were drilled for the primary purpose of evaluating the aquifers above the gas reservoir. Potable water extends to a depth of 3,730 feet. Salt water occurs from 3,730 to 5,630 feet. Low quality subpotable water extends from 5,630 to 7,140 feet. The salt water zone is interpreted to be a tongue of Wasatch extending from the west into Eocene arkoses derived from the Wind River Range to the east.

Plans call for sequential detonation of five explosives spaced at intervals from 9,220 to 11,570 feet, to produce a more or less continuous chimney from 9,000 to 11,650 feet. There will be a safety margin of 1,600 feet between the top of fractures and the bottom of the known aquifers.