1、 What is the function of annular BOP?

(1) When there is a pipe string in the well, a rubber core can be used to close the annular space formed by the pipe string and the wellhead;

(2) The wellhead can be completely sealed when the well is empty;

(3) In case of overflow and blowout during drilling, milling, casing grinding, logging and fishing of downhole falling objects, the space formed by Kelly, cable, steel wire rope, accident handling tools and wellhead can be sealed;

(4) With the cooperation of pressure reducing and regulating valve or small energy accumulator, the 18 ° butt welded pipe string joint without fine thread can be forcibly lifted; (5) in case of serious overflow or blowout, it is used to cooperate with RAM BOP and choke manifold to realize soft shut in.

2、Hat should be paid attention to when tripping the drilling tool when closing the well with annular BOP?

(1) Only 18 ° butt welded drill pipe joints without fine thread are allowed to be lifted and lowered. (2) During tripping, a small amount of leakage between the rubber core and the drill pipe is not only allowed, but also necessary. A small amount of leaked drilling fluid can lubricate and cool the rubber core and improve the service life of the rubber core. If necessary, add lubricant on the top of the rubber core to lubricate the rubber core. (3) The tripping speed must be slow, especially when crossing the joint.

3、Working principle of annular blowout preventer

1. Working principle of conical rubber core annular blowout preventer

When the conical rubber core annular blowout preventer is shut in, the pressure oil from the hydraulic control system enters the lower oil chamber (closing the oil chamber) to push the piston to move up quickly. The rubber core cannot move up due to the restriction of the top cover. Under the action of the inner conical surface of the piston, it is forced to squeeze and tighten the drilling tool towards the center of the wellbore and surround the drilling tool to close the annular space of the wellhead. When there is no drilling tool in the well, the rubber core shall be squeezed and tightened to the center until the hollow part of the rubber core is filled with rubber, so as to completely seal the wellhead. At the same time, the hydraulic oil in the upper oil chamber flows back to the oil tank through the hydraulic control system pipeline.

When the conical rubber core annular BOP is opened, the pressure oil from the hydraulic control system enters the upper oil chamber (open the oil chamber) to push the piston down quickly. The extrusion force of the inner cone of the piston against the rubber core disappears immediately. The rubber core extends outward by the elasticity of its own rubber, recovers to the original state, and the wellhead is fully opened. At the same time, the hydraulic oil in the lower oil chamber flows back to the oil tank through the hydraulic control system pipeline.