Annular BOP is an important part of well-control equipment. It mainly applies to

control wellhead pressure during drilling, work over 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.

1, It can seal any size of annular space with a kind of rubber if there is a

drilling tool, tubing or casing in hole.

2, When there is no drilling tool in hole, it can seal the well head completely.

3, When the well blowout and overflow happens during drilling, coring or well

logging, it can seal the annular spaces between Kelly, coring tools,  cable,

wire line and well bore.

4, 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.