516 Subsurface Geologic Methods 



occasions a considerable saving in rig time. Rock-type bits and reamers 

 are used in hard formations. 



The Eastman spudding bit (fig. 246) is a semipercussion-type deflect- 

 ing tool for use in soft formations. It is constructed with a chisel point 

 on the bottom and a single circulating hole in the center of the cutting 

 edge. It is not designed to be rotated as are the other deflecting tools 

 described above. In a number of cases it has been found to do very satis- 

 factory work in soft formations. 



The spudding bit is made up on the bottom of the drill pipe and, 

 at the bottom of the hole, is faced in the direction desired. While circu- 





Figure 246. Spudding bit. 



lation is carried at a fairly high pressure, the drill pipe is spudded up 

 and down. The combination of the cutting action of the chisel point and 

 the jet action of the drilling fluid makes a small amount of deflected hole. 

 From one to four feet of hole is made in this manner. Then a follow-up 

 run of fifteen to twenty feet of small gauge "rathole" is made with a small 

 diameter bit to continue the deflection. This "'rathole" is reamed in the 

 same manner as described for the removable whipstock and knuckle joint. 

 The amount of hole made with the spudding bit and the weight carried 

 on the follow-up bit have a very great influence on the amount of deflection 

 made in the well. This tool often is used to assist in sidetracking a cement 

 plug in soft formations. A spudding bit is run and six inches to one foot 

 of hole made. Then a removable whipstock is faced so that the chisel 

 point of the whipstock sets down into the wedge-shaped hole made by the 



