To cover the methods of well control for fixed rigs, cover the special considerations for subsea rigs (Types of drilling rigs), and look at step-down graphs for deviated and horizontal wells.
General Well Control Methods
The objective of the various kill methods is to circulate out any invading fluid and circulate a satisfactory weight of kill mud into the well without allowing further fluid into the hole. Ideally, this should be done with the minimum of damage to the well.
If this can be done, then once the kill mud has been fully circulated around the well, it is possible to open up the well and restart normal operations. Generally, a kill mud that just provides hydrostatic balance for formation pressure is circulated.
This allows approximately constant bottom hole pressure which is slightly greater than formation pressure to be maintained as the kill circulation proceeds because of the additional small circulating friction pressure loss.
After circulation, the well is opened up again and the mud weight may be further increased to provide a safety or trip margin (Check also: Kill Mud Weight)
Constant Bottom Hole Pressure Kill Methods
There are three constant bottom-hole pressure kill methods in common use today which are: