The use of air to provide an aid by which holes could be drilled has been an interesting and sometimes complex series of events. The bulk of what has happenedpertaining to oil well drilling has been accomplished from approximately 1950 to date. Characteristically, this work has been a series of "Ups and downs". The most significant step has been in the development of foam to extend the application of the air techniques in locales where water influx and hole enlargement, would otherwise preclude the. use or air. It has taken application of the sciences, time, sweat, and more than a little faith to reach our present plateau.
The interest in drilling using air has probably had as many "ups and downs" as the stock markets. The lows are associated with seemingly insurmountable problems; the highs associated with apparent solutions to these problems. Sometimes the very solutionsto a major problem have resulted in a new problems to solve. The fact that the problems have been and are being solved accounts for the continuing interest in drilling with air after a, decade and a half of experience in drilling with this technique.
Air drilling as a practical technique in the oilfield came of age in the early 1950's. The obvious attraction lay in the Potentially high drilling rates. The establishmentof air compressor rental companies in the mid 1950's, in West Texas and the Rocky Mountains was an indication that the use of air and gas had become an economic reality. The increasing cost per foot of hole for the operators gave impetus to the development of techniques which would increase penetration rates, thereby reducing the total cost of drilling a hole. In the absence of water invasion air drilling usually produced significant increases in penetration rates over that obtained with a liquid.
Initially, air drilling was accomplished with small construction-type compressors which could only delivered in volumes of approximately 600 CPM at pressures to 150 psi. It was soon recognized that larger volumes and pressures were required and larger compressors which facilitated proper use of technology and engineering toward the drilling of oil wells with air and gas were introduced.
Through practical experience, a general rule of thumb was developed that an annular velocity of 3000 fpm (feet per minute) was necessary to properly clean the cuttings from the hole. Numerous companies and engineers made studies of air capacities requiredfor drilling operations. Of all the studies, one that gained considerable acceptance and popularity in general was published in 1957 by R. R. Angel as a guide to volume requirements for air or gas drilling.
Problems associated with the influx of formation water into the air or gas-drilled holes suppressed potentially high drilling rates and in some instances made continueddrilling with air impossible. A number of materials and techniques to shut off waterwere attempted with limited success.
