actual setting of the whipstock, the hole is prepared by the use of a flat-bottomed 

 bit that provides a firm base for the whipstock. The whipstock is run into the 

 hole on a string of drill pipe, and orientation of the tool is accomplished by 

 measuring the rotation of the drill pipe as it is lowered into the hole or by using 

 a special drill sub with oriented magnetic plugs. Orientation of the whipstock 

 by measuring the rotation of the drill pipe is identical to the procedure outlined 

 under the use of multiple-shot instruments in a cased hole. 



The bottom-hole-orientation system is used in holes which have more than 

 2 degrees of angle at the point a whipstock is to be set. Before this method is 

 used, a single-shot or multiple-shot survey must be made to determine the drift 

 and direction of the well at the point in question. The two opposite-pole 

 magnets in the special drill sub are placed in exact alignment with the face of 

 the whipstock before the tool is run into the hole. A special bottom-hole- 

 orientation instrument is run into the hole when the whipstock has reached 

 bottom, and a reading is taken. The orientation instrument is similar to a drift 

 indicator, except that the recording disc is placed in a cup which is free to move 

 and which is magnetized. The bottom-hole reading is taken when the instrument 

 is between the magnets of the sub, and the instrument is read on the surface 

 when it is placed between two magnets that have exactly the same relation as 

 those on the sub. The angular relation between the face of the whipstock and 

 the low side of the hole, as indicated by the plumb-bob image on the recording 

 disc, is obtained; and the drill pipe is rotated the required amount to correctly 

 face the whipstock. After the rotation of the drill pipe, the bottom-hole orienta- 

 tion instrument is run again to check the facing of the whipstock. 



Once the orientation of the whipstock is known and the drill string has 

 been rotated until it is facing in the desired direction, the whipstock is seated 

 by gentle spudding (i.e., raising the drill string slightly, then allowing it to fall) 

 which forces the chisel point into the bottom of the hole. When the whipstock is 

 firmly seated, weight is applied to the drill bit, and rotation is started to shear 

 the pins holding the bit to the whipstock. Drilling is continued with care until 

 the taper of the whipstock forces the bit to one side and the well takes its new 

 course. 



After about 20 feet of new hole has been drilled, the drill string and whip- 

 stock are removed. Because the bit itself is larger than the opening in the upper 

 collar of the whipstock, removing the bit also removes the whipstock. Care is 

 taken in going back into the newly deflected hole, but once the round trip past 

 the kick-off point has been made several times, there is very little tendency for 

 the bit to miss the new hole. Figure 32-3 shows a whipstock that has been 

 removed from the hole after successful deflection of the well. 



The procedure for setting a removable whipstock outlined above is similar 

 to that followed in drilling most directional wells; however, modifications of 

 the above procedure sometimes are used. Some whipstocks are designed to 



685 



