Abstract The San Juan Basin of Northwestern New Mexico gave the impetus to the drilling industry to extend the use of gas drilling. This in turn brought about extended use of compressed air as a drilling medium, especially in wildcatting. Many new drilling problems have developed with the advent of this type of drilling. Air drilling experiences have reached a point where problems such as water entry, crooked hole conditions, and the shortage of suitable air compressor equipment have at least partially been solved. Air drilling has opened an entirely new field for design and invention. Introduction and Review of the San Juan Operations The San Juan Basin of Northwestern New Mexico gave the oil and gas industry its first practical application for air drilling. This might be compared with the start the Rangely field in Colorado gave to the diamond bit. Since 1951, the El Paso Natural Gas Co. has completed 400 wells in this Basin using gas as a circulating medium. It is estimated that there are between 800 and 1,000 wells that have been gas-completed in this area. These wells were completed principally in the Mesa Verde formation of Cretaceous Age, which consists of 800 ft of interbedded sand, shales, and coal at an average depth of 5,000 ft. This gas formation has a very low porosity, low permeability, and a reservoir pressure of approximately 1,250 psi. This field would have been impossible to develop without gas drilling. Drilling mud completely blocked the producing formation and the only alternative, prior to gas drilling, had been cable tool operations. It often took five to eight weeks to drill the 800-ft Mesa Verde section. After shooting this section with as much as 2,300 qt of solidified nitroglycerin, the cleaning out process further increased the hazards of cable tool operations. Cable tool drilling in this formation brought about seemingly endless fishing jobs. It was not uncommon to have as many as three strings of tools in the hole at one time, and in a number of cases from one to two of these were left in the hole. Rarely was a Mesa Verde well completed without at least one fishing job.