Page 315 - Well Control for Completions and Interventions

306 Well Control for Completions and Interventions

annulus pressure of 0 psi complete evacuation. This very stringent
approach can be revised if verifiable data on casing fluid density and
casing fluid level is available.
Clearly the pressure method is not suitable for wells where the condition
of the completion is suspect, where losses are likely to occur or where fracture
pressure is low. The pressure method should only used where the condition of
the tubing is known to be good and where there is a plug above the reservoir.

7.7.3.1 Procedure for the constant pressure method (lubricate and bleed)
1. Calculate the gas gradient in the tubing.

BHP 2 SICHP
Gas gradient psi=ft: 5
reservoir depth TVD
2. Calculate pipe capacity and volume.
3. Calculate the kill weight requirement.
Plugged well: Calculated kill weight to the plug. Assumed a column
of gas from the plug to the reservoir.
No plug: Calculate kill weight to the top of the reservoir.
4. Calculate the maximum volume that can be pumped without
exceeding the maximum allowable surface pressure using Boyle’s law.
If no plug is installed, formation fracture pressure is likely to deter-
mine the maximum pressure that can be applied at surface.
P 1 V 1
V 2 5
P 2
5. Pump fluid until the wellhead pressure reaches the maximum allow-
able pressure (or the calculated amount has been pumped).
6. Allow time for fluid to drop into the well.
7. Record the volume of fluid pumped.
8. Bleed dry gas from choke to reduce casing pressure to the previous
recorded wellhead pressure plus the calculated hydrostatic pressure
increase. Allow the well to stabilize.
9. Pump fluid until the wellhead pressure reaches the maximum allow-
able pressure.
10. Allow time for the fluid to fall in to the well.
11. Bleed dry gas from choke to reduce casing pressure to the recorded
wellhead pressure at the start of the stage, plus the calculated hydro-
static pressure increase. Allow the well to stabilize.
12. Repeat steps 9 11 until the well is dead.