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2. Bullheading
This procedure is recommended in very special cases and should only be used when normal circulation method for kick control is thought to be too dangerous (large influx, excessive surface pressures/gas volumes if influx circulated out, unable to strip to bottom It is to be noted that in certain cases bull heading could possibly create worst problems (i.e. severe lost circulation) than what it might solve.
One of the following hole conditions must exist for successfully accomplishing a kill operation by using a Bull heading Technique:
- Very small amount of open hole exists or the second weakest point in the open hole has a fracture/injection pressure higher than the reservoir where the kick originated.
- Influx is above the weakest point in the open hole and hardly any open hole exists.
- All of the other following conditions must exist:
- Operations have been comprehensively planned and no problems are foreseen.
- All equipment (surface and down hole) must have a higher pressure rating than the maximum anticipated Bullhead pressure (allowing for relevant fluid gradients).
- Casing Burst must exceed surface bull heading pressure plus any hydrostatic difference between Mud Hydrostatic Inside casing and Mud Hydrostatic outside casing
- Surface Mud Volumes must be at least equal to double the amount required to bullhead influx back into zone. (Generally bull heading will not be started until surface mud volume is equal to twice the entire hole volume. If this is not possible due to Rig Mud System, additional volume will be built and placed on a liquid mud supply vessel).
- In extremely critical cases, seawater may be used. Seawater will not kill well but will probably reduce surface pressures.
- Bull heading will not create severe lost circulation (i.e. Total loss of fluid column in the annulus).
- Usually it will be necessary to pump more than the calculated volume due to poor displacement of influx.