is the amount of additional equipment needed to cool and dehumidify the engine 

 exhaust and to remove acids from the gas. 



GEOLOGICAL From the standpoint of the geologist evaluat- 



CONSI DERATION ing a well being drilled with air, there are 



one or two new aspects that must be consider- 

 ed. In the first place, the cuttings arrive at the surface as a fine powder, and 

 the conventional methods of sample identification generally will be ineffective. 

 It takes some practice to identify the cuttings accurately. In a known area the 

 color of the powdered material is almost as reliable a means of identification as 

 can be obtained with the microscope. 



A decided advantage to air drilling is that there is practically no lag, and 

 the contamination of samples from different formations is reduced considerably. 



It should also be remembered that the conditions are very similar to those 

 which exist during a drill-stem test. It would be extremely difficult to by-pass 

 any zone containing even a show of oil or gas. 



In the preceding section several advantages and disadvantages relating to 

 air drilling have been discussed. In the first place, where it is applicable, air 

 drilling can reduce drilling costs greatly by increasing penetration rates and 

 prolonging bit life. On the other hand, in some instances the cost of attempting 

 to combat formation water may be excessive. 



In a wildcat operation there is an increasing chance of blowouts in addition 

 to fire and explosion hazards. Before attempting an air-drilling operation, an 

 appraisal based on all known facts should be carefully made. 



With the constantly increasing cost of drilling wells and the decreasing 

 percentage of successful wildcats, it is becoming more important to take full 

 advantage of any opportunity for lowering drilling costs. Air and gas drilling 

 may be one answer. In several parts of the country it has already become an 

 accepted method and will undoubtedly become popular in many other areas as 

 soon as reliable water-shutoff methods are developed. 



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