Miscellaneous Subsurface Methods 505 



The Eastman removable whipstock is used more than any other type 

 of deflecting tool. Run in open hole, it is a safe and easy tool to operate, 

 and can be depended upon for accurate and reliable results. Illustrated 

 in figure 238A, the removable whipstock is a cylindrical steel casting five 

 to twelve feet long, the length varying with the diameter. It is made with 

 a chisel point on the bottom, which, when imbedded in the formation, 

 prevents it from turning. It is cast with a ring at the top, by means 

 of which it may be lowered into and withdrawn from the well. The 

 back of the ring is provided with a tapped hole into which a shear bolt 

 can be screwed. A concave, inclined groove is formed on one side from 

 the bottom of the ring to the chisel point. Special spiral-type drag bits 

 are designed to be used with each size whipstock. The diameter of the 

 bit is too great to pass through the ring of the whipstock, and spiral fins 

 on the bit cause it to drill smoothly along the face. A tapped hole in the 

 shank of the whipstock bit accommodates the end of the shear pin. From 

 an inspection of table 25 it will be noted that removable whipstocks are 

 cast in diameters ranging from four inches to thirteen inches. They are 

 run in holes from one to two inches larger in diameter than the whip- 

 stock, according to the type of formation, the quality of the drilling mud, 

 and the depth of the well. Some of the larger tools are fluted or ribbed to 

 reduce their weights (fig. 238C and fig. 238D). 



The procedure for running a whipstock is outlined below. The tool 

 should be run after the use of a flat-bottomed bit. The removable whip- 

 stock is held vertically against the rotary table by the cat line, with its 

 face toward the hole, and the drill pipe is lowered through the ring from 

 above. The whipstock bit is made up tight on the end of the drill pipe. 

 The cat line is removed and the drill pipe picked up until the bit takes 

 the weight of the whipstock. It is lowered part of the way into the hole, 

 and the slips are set. The shear bolt is screwed through the back of the 

 whipstock and into the tapped hole provided in the whipstock bit. Thus, 

 the drill pipe and the tool turn as a unit as they are run into the well. 

 The slips are removed and the whipstock is lowered into the well by 

 adding the drill pipe stand by stand. Care should be used in running in 

 with a whipstock, since if the hole is bridged or under gauge, the whipstock 

 bolt is liable to shear before bottom is reached. When the whipstock is 

 near bottom, it is faced in the desired direction, and the drill pipe is 

 spudded lightly to force the chisel point into the formation. Part of the 

 weight of the drill pipe is then applied to the shear bolt. After the bolt has 

 sheared, the bit is turned slowly and very little weight is applied as it drills 

 down the tapered face of the whipstock. As shown in figure 239, the bit 

 enlarges one side of the original hole until it reaches the bottom of the 

 whipstock. At this point it starts making a new, small-gauge hole. More 

 weight is carried on the bit after it penetrates past the bottom of the 

 whipstock. Approximately twenty feet of this small "rathole" is drilled. 



The drill pipe is hoisted until the bit engages the whipstock ring. 



