Geological problems, as well as location problems, create situations where 

 directional drilling is the best solution. Faulting in an oil field is a continual 

 challenge to the geologist assigned the task of selecting well locations. Figure 

 32-8 illustrates one of the many situations involving faulting that may be solved 

 by directional wells. In this field the petroleum reservoir is in steeply dipping 

 sands that are below a reverse fault. The fault itself is the seal for the reservoir. 

 Because of the steepness of the beds, a vertical well, such as well B, would have 

 to be located with extreme accuracy or it would penetrate only a very small 

 portion of the reservoir. Such a well might conceivably miss the productive sands 

 entirely if the sands are not thick. In any case, even a well-placed hole would 

 penetrate only a small portion of the entire thickness of the sand above the oil- 

 water contact. A directionally drilled well such as A, however, would have a far 

 greater chance of penetrating a maximum productive section because of the 

 greater vertical extent of the reservoir as compared to the horizontal extent. 

 Furthermore such a well, even if poorly located because of scanty information 

 about the reservoir, would have a greater chance of penetrating more of the 

 effective thickness of the sand above the oil-water contact. A directional well in 

 the reverse direction, such as C, might penetrate an even greater thickness of 



Figure 32-8. Controlled directional drilling for solving fault problems. 



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