CHAPTER 6 



MISCELLANEOUS SUBSURFACE METHODS 



CONTROLLED DIRECTIONAL DRILLING 

 J. B. MURDOCH, JR. 



Probably the first directional-drilling work ever done was to side- 

 track tools lost in a well. When the driller considered that the churn- 

 drill bit was irretrievably lost, he went into the nearby forest and cut 

 down a tree of slightly smaller diameter than the hole that was being 

 drilled. Starting at the top of this log he cut a long, tapered face on one 

 side. This crude whipstock was forced down the hole until it lodged on 

 top of the fish. He ran the tools back into the hole and drilled care- 

 fully, until he had sidetracked the lost equipment. It is interesting to 

 note that this same hand-hewn whipstock is used today by water-well 

 drillers in many parts of the country. The art of controlled directional 

 drilling has advanced greatly from this first primitive sidetracking opera- 

 tion. Today, with the assistance of service companies specializing in this 

 work, operators are able to do what would have been considered impos- 

 sible twenty years ago. One exploratory well has been forced to deviate 

 at drift angles as great as 80 degrees and to bottom over 9,000 feet (nearly 

 two miles) horizontally from its surface location. 



To a certain extent it might be considered that directional drilling 

 is a logical outgrowth of well surveying. Operators had discovered that 

 many wells deviated great distances underground by natural means. They 

 considered that it might be possible to control this deviation to their 

 advantage, forcing the well to bottom at almost any predetermined point 

 at a desired vertical depth. Certain ingenious individuals set about build- 

 ing experimental tools and devising practical methods for carrying on 

 such operations. 



A number of different types and sizes of deflecting tools have been 

 constructed and are in general use wherever directional drilling is re- 

 quired. Primarily, they must be able to alter the course of the hole either 

 in drift or direction or in a combination of both. This deflection must 

 be within practical limits of angle so that the well has no "dog legs" in 

 its course toward the objective. The design of these tools must be such 

 that they can be used in conjunction with standard rotary-drilling equip- 

 ment. They must be safe to run in the well. They should not require 

 that cement or other foreign material remain in the well after they are 

 used. Owing to the increased cost of drilling wells, tools of this type 

 must occasion the loss of as little rig time as possible. Simplicity in 

 design of such tools is desirable, as it is with any other oil tool used on 

 the drilling string. The deflecting tools described below have been de- 

 signed and constructed with these considerations in mind. 



