Page 145 - Well Control for Completions and Interventions

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CHAPTER FOUR

Well Control Surface Equipment

4.1 INTRODUCTION

During most completion and workover operations an overbalanced
fluid column forms the primary well control barrier; overbalance pressure
prevents an influx of reservoir fluid. If the primary barrier fails and reser-
voir fluids enter the wellbore, surface well control equipment is used to
secure the well. Since surface equipment is classified as the secondary well
control barrier, it must be able to close in and secure the well at all the
different stages of a completion or workover operation. It must also be
configured in a way that allows the primary barrier to be restored.
During drilling operations, restoration of the primary fluid barrier is nor-
mally achieved by circulating heavy (overbalanced) fluid into the well and
circulating out the formation fluid. During completion and workover
operations the primary barrier might be restored by circulation of kill
fluid, but it is equally as likely to be a bullhead or lubricate and bleed kill.
Properly configured, the well control equipment will allow shut-in
with and without pipe in the well. It will also allow drill pipe and com-
pletion tubulars to be cut, allowing the drill string or completion to be
hung off in the rams and stripping of pipe into the well if a kick occurs
off the bottom.
In the event of a kick with pipe in the well, it is secured using the fol-
lowing barriers:
Inside pipe barriers:
• Full opening safety valve (FOSV).
• One-way valve (internal blow out preventer (BOP) or dart sub).
• Check valves (drill pipe float valve).
Annulus (outside pipe) barriers. BOP equipped with:
• Annular preventer.
• Pipe ram (fixed diameter or variable bore).

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