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

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