BAKER HUGHES - Drilling Fluids Reference Manual

PRESSURE PREDICTION AND CONTROL
PRESSURE CONTROL METHODS
Pressure control is normally a field level activity. The methods of killing well kicks which are
presented here have been developed for rig site personnel. The procedures for killing a
threatened blowout must be kept simple, but not oversimplified to the extent of losing their
effectiveness.
The three basic, most common well-control methods employ procedures to maintain a constant
bottomhole pressure on the wellbore while formation fluids are circulated to the surface. This
is accomplished by using an adjustable choke which can be opened or closed to control
wellbore pressures. Three variations of the balanced bottom hole pressure are as follows:
• Building fluid density in the pits before circulating (Wait and Weight).
• Begin circulating out the bubble and weighting up simultaneously (Concurrent Method).
• Circulate well clean of formation fluids, shut pumps down and close well in. Then build fluid
density in pits before circulating heavy fluid (Driller's Method).
Note: When a kick cannot be circulated out, or there is no way to
communicate with the bottomhole pressure, the only way to
control bottomhole pressure is by use of the volumetric method.
Of these three methods, the Wait and Weight Method is the most commonly used. It is
discussed below and a sample problem with a completed kill sheet is included to illustrate the
use of this technique.
The Wait and Weight Method of Well Control
The Wait and Weight Method of Well Control is the most satisfactory method of well control
since it causes the lowest annular pressures and is the quickest way of reducing the pressures
on the wellbore. It does require a period of shut-in time while the fluid weight is being
increased, so there is some danger of the pipe becoming stuck.
If the rig does not have adequate fluid mixing equipment, one of the other constant bottomhole
pressure methods may be more satisfactory. On most large rigs, marine rigs, and rigs with subsea
stacks, the Wait and Weight Method is the preferred method.
In the Wait and Weight Method, the well is shut in until the fluid weight is increased in the pits
and the well is killed according to a completed worksheet.
As an example, the well is shut in after a kick and the following information is recorded.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 12-31