The Main Structure Of The Blowout Preventer 

Blowout preventer is an important well control device, which plays an important role in drilling, especially underbalanced drilling. The purpose of designing the blowout preventer is to close the well bore under pressure, maintain continuous control of the well, and circulate the formation fluid that enters the well.

The hydraulic blowout preventer mainly has two forms: ram blowout preventer and annular blowout preventer. The ram blowout preventer is mainly composed of shell, side door, oil cylinder, cylinder head, piston, piston rod, locking shaft, seal, ram, etc. Its working process is to use hydraulic pressure to push the piston to drive the gate to close or open, thereby closing or opening the well head, achieving the purpose of closing and opening the well.

The ram of the ram blowout preventer can be divided into four types of rams: full-sealed, half-sealed, variable diameter and shearing, to realize the well-sealing under different conditions and the semi-sealed ram can close the corresponding pipes such as drill pipes and tubing. If necessary, the drilling tool can be suspended. When there is no pipe tool in the well, the fully sealed ram can fully seal the wellhead. Under special circumstances, the shear ram can cut off the drilling tool. In addition, the flange outlet on the side of the shell can be used for drilling fluid circulation and choke-killing operations.

The type of annular blowout preventer can be divided into cone annular blowout preventer and spherical annular blowout preventer according to the shape of its sealing rubber core. Its structure is mainly composed of the shell, the top cover, the rubber core and the piston. When there are drilling tools, tubing or casing in the well, the annular blowout preventer can use a rubber core to close the annular space of various sizes. When there is no drilling tool in the well, it can completely seal the wellhead during drilling, coring and testing During operations such as wells, the annular space formed by the kelly, coring tools, cables and steel wires and the wellbore can also be closed. Under the condition of using a pressure reducing and regulating valve, the drilling tool can be forcibly lifted off by the drill pipe.

The two types of annular blowout preventers have similar working principles. When it is found that the well surge needs to be closed, the high-pressure oil from the control system enters the lower closing cavity of the piston from the lower oil port to push the piston upwards, and the spherical rubber core follows the spherical surface. Moving upward, the cone-shaped rubber core moves closer to the center under the restriction of the top cover and the squeeze of the inner cone surface of the piston, tightening and encircling the drilling tool to realize the sealing of the drilling tool or the fully sealed wellhead when the well is opened, the piston descends, and the rubber core Reset under the action of its own elastic force to open the wellhead.