mechanical possibilities of this new tool were quickly demonstrated, but the 

 unit failed to meet commercial expectations. In this early construction, metallic 

 bearings were used to carry both the radial and thrust loads of the turbine. As 

 a result of the abrasive action of the drilling fluid, seals that were designed to 

 exclude fluid from the bearings always leaked. 



Because of this failure, a joint development program with the A. 0. Smith 

 Corporation was undertaken on the Scharpenberg drilling turbine from 1935 

 to 1941 and again from 1949 to 1950. Progress was realized in the early phase 

 of this development stage when rubber journal bearings were developed to 

 replace the metallic radial bearings. Some progress was also made toward 

 the development of adequate thrust bearings. However, bearing difficulties still 

 occurred, and further development of the Scharpenberg drill was abandoned in 

 1950 after units failed to show sufficient improvement over rotary methods. 



From about 1925 to the present, the Russians have spent considerable effort 

 to develop an efficient, workable turbodrill. In 1948 they substituted mud- 

 lubricated, multi-disk rubber thrust bearings for the steel ball bearings that had 

 been used up to that time. This innovation contributed greatly to the successful 

 development of a practical turbodrill. At present, Russia is reported to be drill- 

 ing more than 80 percent of its wells with the turbodrill. Considerable develop- 

 ment has also been made in France on the turbrodrill. The French turbine is 

 essentially an adaptation of the Russian design. 



In 1956 Dresser Industries, Inc., acquired 40 of the Russian turbodrills 

 (fig. 31-1) for field testing and entered into an agreement with the French to 

 work closely on future developments in turbine drilling. These turbodrills are 

 being tested in several oil areas in the United States. 



COMPARISON OF In many instances, the turbodrill appears to 



TURBODRILLING be an extremely promising substitute for the 



WITH ROTARY conventional rotary, especially when drilling 



below 6000 or 7000 feet. The turbine method 

 may permit drillers to penetrate deeper than is possible with the rotary system 

 because the turbodrill is not limited by the mechanical characteristics of the drill 

 string. 



With the present rotary, the drill stem is a long, limber power shaft that 

 is influenced by vibrations, wear, and both dynamic and static torque. The 

 great losses in transmitting power characteristic of this system result mainly 

 from the friction between the pipe and hole and the viscosity of the drilling 

 fluid. Rotating speed is limited due to whipping of the drill string; torque is 

 limited to the dynamic torsional strength of the drill pipe. 



It is estimated that less than 10 percent of the power delivered to the 

 rotary table reaches the bit because of the power losses incurred in rotating the 



667 



