4. No-circulation possible
This procedure is recommended when circulation cannot be established (i.e. string, choke lines plugged) and when the string is completely out of the hole and when stripping operation cannot be followed. The basic principle of this technique is to maintain the BHP constant with the well closed, this will be achieved by bleeding off a certain volume of mud in order to allow and control the gas expansion/migration.
4.1 Outline Procedure
1. After shutting the well in allow the shut in SICP to build to SICP2 where:
SICP2= SICP + S + Pressure step
Where:
- . SICP= Initial Shut-in Casing Pressure
- . S = Safety margin pressure increment
- . Pressure step= Working pressure Increment
Convenient values of S and Pressure step are between 50 and 150psi (5 and 10 bars)
2. Calculate the Volume of mud V1 where:
V1= allowance for loss of hydrostatic corresponding to Pressure step
Example: For 6.75” hole (capacity: 23.09 litre/m) Mud weight= 2.32 SG
and Pressure step= 5 bars, Volume V1 will be:
V1= (5 x 10.2 / 2.32)23.09 = 507 litres
3. Bleed off Volume V1 to the trip tank keeping SICP2 constant
4. Allow the new shut in annulus pressure SICP2 to build to SICP3 where:
SICP3= SICP2 + Pressure step
5.Bleed off Volume V1 to the trip tank keeping SICP3 constant
6.Follow the same procedure for SICP4, SICP5….etc