Annular BOP is an important part of well-control equipment. It mainly applies to control wellheadpressure during drilling workover operations and formation testing etc to prevent well blowout effectively and realize safe construction. Annular BOP shall be equipped with hydraulic control system.It is usually used with ram BOP and also independently.

Principle of Annular Blowout Preventer

Annular BOP is controlled by hydraulic system. When BOP is close, high-pressure oil enter lower closing cavity of piston from the central oil orifice of shell, which push the piston coming up. The piston conical surface compress the packing element. As the limit of the bonnet, packing element can not be pushed up, so it has to be squeezed towards the wellhead center until hold fast or total closure of wells, to achieve its purpose of sealing the well.

When opening the well, hydraulic control system inject high-pressure oil to opening cavity of piston, which push piston going down to close pressure relief cavity. Extrusion force on packing element eliminate, and packing element gradual recover because if force of flexibility. Then the well is opened.

Application of Annular Blowout Preventer

It can be used for following operation:

It can seal any size of annular space with a kind of rubber if there is a drilling tool, tubing or casing in hole.
When there is no drilling tool in hole, it can seal the wellhead completely.
When the well blowout and overflow happens during drilling, coring or well logging, it can seal the annular spaces between Kelly, coring tools, cable, wireline and wellbore.
Under the control of the hydraulic control system which is equipped with a depressuring pressure regulating valve or a cushion accumulator, it can force stripping with 18° tool joint.

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