1. Working principle of the annular blowout preventer

The annular blowout preventer is operated by a hydraulic control system. When closed, high-pressure oil enters the lower closing chamber of the piston from the oil port in the middle of the shell, pushing the piston upward. The conical surface of the piston squeezes the rubber core. Due to the limitation of the top cover, the rubber core cannot move upward but can only be squeezed towards the center of the wellhead until it embraces the drilling tool tightly or fully seals the wellhead, achieving the purpose of well sealing. When it is necessary to open a well, operate the reversing valve of the hydraulic control system to make high-pressure oil enter the opening chamber at the upper part of the piston from the upper oil port of the shell, push the piston downward, close the chamber to relieve pressure, and the squeezing force acting on the conical surface of the rubber core is eliminated. Under the action of its own elastic force, the rubber core gradually returns to its original position, opening the well opening.

2. Usage Requirements

When a blowout occurs in a well with drilling tools inside, a ring-shaped blowout preventer can be used to control the wellhead first. However, it is advisable not to keep it closed for a long time. Firstly, the rubber core is prone to damage, and secondly, there is no locking device. Under normal circumstances, it is not used to seal empty Wells.

(2) When using a circular blowout preventer for drilling operations without well pressure, drilling tools with an 18-degree slope must be used. When passing through the joint, the speed of lifting and lowering the drill should be slow, and all rubber hoops on the drilling tools should be completely removed.

(3) When the annular blowout preventer is in the off state and the well closure pressure is below 5MPa, the drill string can be moved up and down, but rotation of the drill string is prohibited.

(4) It is strictly prohibited to release the pressure inside the well by opening the annular blowout preventer to prevent the rubber core from being punctured.

(5) After each well opening, it is necessary to check whether it is fully opened to prevent the rubber core from being damaged by hanging.

(6) After cementing, leak sealing and other operations, the inner cavity should be thoroughly flushed and the switches should be kept flexible.

(7) When installing or removing the annular blowout preventer, special attention must be paid to the sealing gasket ring and the steel ring groove. It is not allowed to damage or scratch them.

(8) After entering the target layer, each time the drill is pulled down, a test well closure with drilling tools should be conducted to check the sealing effect of the rubber core. It does not meet the requirements and should be replaced immediately.

(9) According to relevant standards, the pressure test of the wellhead annular blowout preventer should be conducted regularly.