Review of Air and Gas Drilling

Abstract

Abstract Experimental work with compressed air or gas as drilling fluid has been carried on by Humble in West Texas, South Texas, North Texas, and New Mexico with beneficial results in nearly all instances. During the past three years, gas has been used at certain stages in drilling seven wells and air in nine wells. Penetration of lost returns sections has been facilitated by this method of drilling and, in addition, drilling rates have been greatly increased. Air or gas may be used to advantage with rotary drilling in areas where formation water is limited, the formation does not slough, and where pressures of fluids which may be encountered are sufficiently low to snake safe operation possible. An injection pressure as low as 65 psi is sufficient when the hole is dry, much higher pressure being required for handling formation water influx, however. Although its application is limited, as mentioned, progress is being made in developing techniques for handling formation water encountered in conjunction with air or gas drilling. Introduction The drilling industry in the United States during the past five years has effected a remarkable improvement in footage drilled with no basic or revolutionary changes in method of operation; average footage per rig year has risen from 35,369 ft to 45,200 ft. The average well cost and average footage cost have not been reduced, however, because of increased costs of materials and services. A possibility for reducing over-all costs lies in the further development of new techniques. It is the purpose of this paper to set forth benefits which have been possible through the use of air or gas as a circulating medium in rotary drilling, a technique which is creating considerable interest throughout the industry. Rotary drilling with air or gas can greatly facilitate operations in wells penetrating sections in which drilling mud would be lost, by effecting reductions in rig time, mud, and casing costs, in many cases being more effective than cable tools. Damage to producing formations can be averted by eliminating contact with drilling mud. Great benefit is also derived, however, from markedly increased penetration rates and bit life as compared to drilling with mud. The following discussion is limited to Humble's experience with air and gas drilling.