A Blow Out Prevention (BOP) stack is installed on a wellhead to control the removal of an influx from the wellbore.
All pressure contained components of the BOP stack and related equipment shall be constructed of material which meets the standards of NACE MR-01-75 and API RP-53.
BOP stack configuration should ensure that the following objectives can be met:
- It must be capable of closing in on open hole and all tubulars programmed to be run through the BOP.
- It must allow for circulating out a kick with the drillpipe hung-off.
- On re-entry, it must allow the well to be monitored for pressure and circulated, if required, prior to the blind/shear rams being opened and the drill string recovered.
- It must allow for stripping operations to be conducted.
Annular Preventers
Annular preventers shall have the capability of sealing around smooth surface objects of all sizes, including drill collars, kellys, drillpipe, casing, wireline and open hole. They shall also allow drillpipe and tool joints to be stripped through the preventer under pressure.
Ram Preventers
The ram preventer shall seal only around a pre-designated shape, e.g. round objects (pipe and casing rams) or open hole (blind rams).
In offshore operations an additional ram preventer shall be equipped with shear blades which may cut drillpipe or casing and also have the ability to seal open hole (shear/blind rams)