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
- 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