The rapid development of this field is credited entirely to the use of the turbo- 

 drill. The Russians drilled wells in 8 days that would require 36 days by rotary ; 

 wells in this field are from 5400 to 5600 feet deep, and it is hard drilling practi- 

 cally all the way. An average of 61 bits per well and 100 feet per hour 

 penetration rate is reported. A breakdown of the time spent on the average 

 well is as follows: 



Actual drilling time 54 hours 



Adding Pipe 22 hours 



Pulling pipe 126 hours 



Total 202 hours 



On some wells the Russians use from 20 to 27 tons of weight on a bit that 

 runs at 400 to 900 revolutions per minute. Two 400-horsepower mud pumps 

 operate at 1470 to 1760 pounds per square inch. With this rig and a 6%-inch 

 turbine, they have drilled to depths of 15,000 feet. 



Another operation witnessed in Russia was at a well drilling in dolomite 

 at 1200 feet. A rotary system was run at 250 revolutions per minute, which is 

 high for this formation. The weight on the bit was 20 tons, and the maximum 

 rate of penetration was 414 feet per hour. In the same formation a turbodrill 

 with 20 to 24 tons on the bit drilled at the rate of 57 to 75 feet per hour. In both 

 tests the mud pressure was 1470 to 1760 pounds per square inch, and the 

 circulation rate was 950 gallons per minute. 



In a Siberian well, the following comparison of turbodrilling performance 

 with that of rotary was made: 



Rotary Turbodrill 



Penetration rate 15 ft per hr 48 ft per hr at 8 tons 



57 ft per hr at 10 tons 

 75 ft per hr at 24 tons 

 Weight on bit 22-24 tons 8-24 tons 



Bit speed 225 rpm. 900 rpm 



Turbodrilling economies are obtained primarily because of an ability to 

 afford faster penetration rates and lower drill-pipe costs. The lighter service 

 imposed on drill pipe permits the use of lighter drilling strings, which reduces 

 replacement costs. Although increased pump capacity is sometime required by 

 the turbodrill, savings on overall drilling costs can be made through lower costs 

 for drill pipe and other rig components. 



The turbodrill promises to offer the oil industry a remarkably efficient 

 drilling method. To what extent it will actually replace rotary drilling in America 

 will be determined only after it has been used for considerable time in various 

 domestic oil fields. The future for the turbodrill does, however, appear tremend- 



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