Annular BOP

1. Application

    Used in conjunction with hydraulic control system, the annular BOP seals off the annulus of different sizes when pipes are in use in the hole. An annular BOP can also seal off the hole when no pipe is in it. When used in conjunction with the pressure-regulating valve and accumulator, the annular BOP allows snubbing service.

 

2. Working Principles

    A hydraulic control system is used to close or open the 

annular preventer. when it is closed, high pressure oil is directed to the closing chamber positioned in the lower side of the piston, causing the piston to move upward. The packing unit is compressed by the moving piston. Because the annular BOP has a cap, the packing unit can not move upward and only can move toward the center of the well to pack off a string or seal off the well.

 

3. Operating Requirements

    (1) The annular BOP can be used to seal off a well where the drill pipe is in use if the well blowout. However, the annular BOP cannot be closed for a long time, because the packing unit is easy to be damaged and the BOP itself has no locking mechanism.

    (2) It is necessary to use a drilling tool with 18°bevel when running/retrieving drill of operation with BOP, running/retrieving drill should be slow pass through the nipple and all the rubber protecting collar on the drilling tool should be discharged off.

    (3) With the annular BOP in the closed position and shut-in pressure kept below 5MPa, the string can be moved either up or down, but mustn’t be rotated.

(4) It is forbidden to open the annular BOP to relieve the pressure out of the well to avoid rubber core damage.

    (5)Be sure to check whether the annular BOP is in the full open position or not every time after opened in order to prevent damage to the packing unit.

    (6) Clean the inside of the BOP after well cementing operation is completed in order to keep its closings and openings flexible.

    (7) More attention shall be paid to ring gaskets and gasket grooves during installation of the BOP or its removal from the service.

    (8) After entering the destination layer, running/retrieving drill once should be accompanied with test of well-enclosed with drilling tool once, and inspect the effect of well enclosed with rubber core, if beyond the requirement, it should be replaced.

(9) Periodically perform pressure test on the annular BOP in accordance with applicable standards.