METHODS OF DEFLECTING A WELLBORE


Any number of directional tools can be used to deflect a wellbore or make the wellbore go where we want it to go
Methods of Deflection
  • Whipstocks
  • Jetting
  • Rotary BHA
  •  Rotary BHA with adjustable stabilizer
  • Motor
  •       Steerable motor
  • Rotary steerable assembly
  • Over time, the tools we have used to deviate a wellbore in the desired direction have changed

  • Newer and more efficient tools have been developed and will be developed in the future
Significant advances in directional drilling technology
 Whipstock
  •      One of the earliest tools used in the industry was the whipstock
  •  The whipstock is a metal wedge placed in the wellbore that causes the bit to deviate
  •     In the early years of the petroleum industry, they were used to sidetrack wells if a portion of the drill string became stuck
  •      As directional drilling started in the 1930’s, whipstocks were oriented and used to change the inclination and azimuth of the wellbore Whipstocks were not very efficient
  •      In order to use a whipstock, the drill string was pulled from the hole and a whipstock was run into the well
  •      On a retrievable whipstock, a pin was sheared and the bit drilled off the whipstock
  •  
  Retrievable whipstock

  •      Because the bit had to be run in with the whipstock, it was a smaller diameter than the hole
  •      A second trip was made to open the hole to full gage 
  •   In harder rock, a reaming trip may have been required
  •   Using the whipstock required a minimum of three trips, which was not cost effective
  •   Permanent whipstocks were no better even though a full sized bit could be used to drill off it
  •      Today, whipstocks are used frequently to sidetrack out of casing
  •      The majority of casing sidetracks are now performed with a whipstock 
 


METHODS OF DEFLECTING A WELLBORE con't