@6afit&i 36 



DRILLING WITH 

 GAS AND AIR 



i. M. Brantly 



As early as 1938, gas was used as a circulating medium in the Texas Pan- 

 handle in an effort to speed up the cleaning out of gas wells after shooting with 

 glycerin. The rotary equipment at that time did not efficiently clean the hole of 

 the larger fragments that remained after shooting. By the use of gas, which was 

 readily available in the field, it was possible to obtain a sufficiently high ascend- 

 ing velocity in the annulus to bring out many of the fragments. To what extent 

 this method was used or perfected is not known, but it was probably used only 

 a short time and in relatively few instances. From that time until the late 

 1940's, very little if any attention was given to the use of gas or air in drilling or 

 completion operations. 



The next records of the application of air or gas show that it was used in 

 an attempt to lighten the mud column being circulated in a hole, thereby de- 

 creasing the hydrostatic pressure on weak or porous formations which would 

 have otherwise become thief zones. This is still the primary reason for using 

 air or gas in drilling programs. More recently other reasons have developed. 



GENERAL PRINCIPLES In so-called conventional drilling, mud or 



water is circulated down the drill pipe and 

 up the annulus in order to cool the bit and carry the cuttings to the surface. 

 Basically air and gas function in the same manner. Air is compressed on the 



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