Ring segments of blood vessels were isolated from the lungs of rabbits, cats, and monkeys. After constriction with norepinephrine, electrical field stimulation caused smooth muscle relaxation in these segments. Mechanical removal of the endothelial layer, verified by scanning electron microscopy, abolished or greatly attenuated the relaxation. The response could be restored in part by apposing the endothelial surface of another vessel segment and the denuded inner surface of the constricted vessel segment. Incubation with tetrodotoxin, procaine hydrochloride, guanethidine, propranolol, atropine, metiamide, indomethacin, quinacrine hydrochloride, 5,8,11,14-eicosatetraynoic acid, aminophylline, and verapamil failed to block or enhance the relaxation response to field stimulation. We conclude that the vascular endothelium in the larger pulmonary arteries and veins studied contains a diffusible substance that inhibits smooth muscle contraction. Its release by electrical field stimulation in vitro does not involve classic neuronal transmitter release or metabolism of arachidonic acid by cyclooxygenase or lipooxygenase.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Project Rulison was designed to use underground nuclear technology to determine the potential of this technique for commercial development of the Mesa-verde 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 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 then 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 production will be sufficient if costs can be controlled. Costs of nuclear stimulation must be drastically reduced for a commercial process. The total Project Rulison cost will be approximately $5.9 million. At such prices, nothing can possibly be prices, nothing can possibly be commercial; however, as outlined in the paper, these costs can come down in a paper, these costs can come down in a logical step-wise fashion to an economic number. A nuclear explosive with a design yield of 40 kilotons was emplaced and detonated in a 10-3/4" casing at a depth of 8426' below ground surface and detonated on September 10, 1969. A preliminary appraisal of the data taken at shot time indicate that the explosive behaved as predicted. The explosion was completely 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. Introduction The greatest challenge to the oil industry has always been how to make available oil and gas at an economic rate. The increasing costs of exploration and the impending shortage of natural gas have made the economic development of marginal resources not only attractive, but necessary.

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