Cfafiten, 32 



DIRECTIONAL 

 DRILLING 



Harry C. Kent 



Since the time of Titusville, crooked holes have been drilled in the search 

 for petroleum. The early holes which deviated from the vertical were not 

 intentionally drilled so, for we know today that many factors over which the 

 early driller had no control contribute to the crookedness of wells. Such 

 conditions as the pressure placed on the rotary bit, the dip of the formations, 

 and the flexibility of the drill string must be considered by the well driller in 

 order to make sure that the well is drilled as planned. 



The older oil fields of the United States have many holes which trend far 

 from the course intended. In fact, a number of early wells have later been 

 found to have crossed lease boundaries in the subsurface and to have bottomed 

 and produced under property not leased or owned by the well owners. With 

 the advent of more modern well-drilling and surveying methods, it is now 

 easy to see why earlier oil exploration was a hit or miss affair, and why so 

 many wells apparently drilled to tap the most favorable part of the reservoir 

 were poor producers or completely dry. 



For a number of geological and engineering reasons, many exploratory 

 and development oil wells are drilled at present with some deviation from the 

 vertical. The application of techniques to control the deviation and direction 

 of a well is known as controlled directional drilling. An understanding of this 

 procedure has become of prime importance to both the petroleum geologist and 

 the petroleum engineer. 



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