Miscellaneous Subsurface Methods 533 



provide for eventualities that might occur as the well is deepened. Thus, 

 they set deflecting tools in such a manner that if an unexpectedly large 

 "dog leg" results, it will be of benefit in the long range program. In a 

 way it might be said that the successful directional-drilling engineer is 

 planning 300 to 400 feet ahead of the bit. 



When the directional drilling has been finished, a completion report 

 is submitted to the operator for which the work was done. This report 

 shows a plan and vertical section of the well, together with a time-penetra- 

 tion curve as illustrated in figure 257. The course of the well as it was 

 actually drilled within the cylinder is plotted on the plan and section. 

 The time-penetration curve is drawn alongside the vertical section. The 

 horizontal axis represents days on the job, and the vertical axis repre- 

 sents depth. Time lost due to repairs, waiting on orders, waiting on ce- 

 ment, logging, weather, etc., are noted at the appropriate depths as they 

 occurred. A summary tabulation gives the number of hours lost due to 

 the causes mentioned above as well as the number of hours drilling. From 

 this information, an average footage of hole drilled per day is derived. 

 The information on this completion report has been found to be of con- 

 siderable value to the operator concerned, especially in estimating subse- 

 quent directional-drilling operations. In a number of cases where com- 

 parisons could be made, it has been found that a directional well was 

 drilled at a faster rate than a straight hole could have been probably be- 

 cause of the fact that, after a directional well has attained maximum drift 

 and correct direction, more weight is applied to the bit than in a straight 

 well. Therefore, the rate of penetration is increased. 



Applications 



The applications of directional drilling are numerous and varied. Its 

 first use was to explore productive zones off the California coast by drill- 

 ing wells from shore to the subsea formations. Since that time many ap- 

 plications of directional drilling have been made throughout domestic oil 

 fields as well as in foreign countries. The discovery of oil-bearing forma- 

 tions in the Gulf of Mexico recently has given added impetus to direc- 

 tional-drilling operations. 



Undoubtedly the greatest amount of directional-drilling work is done 

 in deflecting wells from convenient and accessible surface locations to 

 bottom directly beneath a location where it is impossible or expensive to 

 set up derricks. Much oil has been produced under such conditions that 

 never could have been obtained without directional drilling. 



Since 1933 and to the present time, an ofi"shore structure in the tide- 

 land area seaward from Huntington Beach, California (fig. 262), has 

 been explored and produced by wells drilled from shore. The old field at 

 this location saw the first extensive application of directed drilling. Some 

 60 or 80 slant holes were drilled from surface locations in the town- 

 lot field bordering the shore to subsea bottom locations nearly half a mile 



