Project Rulison was designed to determine the potential of underground nuclear stimulation for commercial development of the Mesaverde Formation of the Rulison field in Garfield County, Colorado. A method of stimulation far greater in magnitude and efficiency than conventional hydraulic fracturing is needed to recover the gas at economic rates.

Detailed testing of the Project Rulison exploratory well, R-EX, provided data on geology, hydrology, and reservoir characteristics. The data obtained from the testing have been used to determine the flow capacity of the Mesaverde reservoir. The reservoir characteristics were used as input data to make predictions of post-shot reservoir performance in the nuclear-stimulated well, using a radial, unsteady-state gas-flow computer model. The calculations show that rates of production will be sufficient if costs can be controlled. Costs of nuclear stimulation must be reduced drastically for commercial use. Project Rulison will cost approximately $3.7 million, excluding lease costs, preliminary tests, and well costs. At such a price, it can not possibly be commercial; however, these costs c n be lowered in a logical stepwise fashion.

A nuclear explosive with a design yield of 40 kilotons was emplaced in a 10 3/4-in. hole at a depth of 8,426 ft below ground surface and detonated on September 10, 1969. A preliminary appraisal of the data taken at shot time indicates that the explosive behaved as predicted. The explosion was contained underground as predicted and no major seismic damage occurred. The post-shot reentry program, in the spring of 1970, will include reservoir testing to determine the degree of stimulation achieved.

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