Where Are Blowout Preventers Used?

The blowout preventer is used to close the wellhead during oil testing, workover, and completion to prevent blowout. It combines the functions of full seal and half seal. It has the characteristics of simple structure, easy operation, and high pressure resistance. It is a safety sealing wellhead device commonly used in oil fields to prevent blowout.

The blowout preventer is the most important well control device, which plays an important role in drilling, especially underbalanced drilling. BOPs are designed to close the wellbore under pressure, maintain continuous control of the well, and circulate formation fluids entering the well.

There are two types of hydraulic blowout preventers: ram blowout preventer and annular blowout preventer. Ram blowout preventer is mainly composed of shell, side door, oil cylinder, cylinder head, piston, piston rod, locking shaft, seals, ram and so on. Its working process is to use hydraulic pressure to push the piston to drive the ram to close or open, so as to close or open the wellhead, so as to achieve the purpose of sealing and opening the well.

The ram of the ram BOP can be divided into four types: full sealing, semi sealing, variable diameter and shearing ram, which are used to realize well sealing under different conditions. The semi sealing ram can seal the corresponding drill pipe and tubing When there is no pipe in the well, the fully sealed ram can completely seal the wellhead, and the shear ram can cut off the drilling tool under special circumstances. In addition, the flange outlet on the side of the casing can be used for drilling fluid circulation and throttling and killing operations.

According to the shape of the sealing rubber core, the annular BOP can be divided into conical annular BOP and spherical annular BOP. Its structure is mainly composed of four parts: shell, top cover, rubber core and piston. When there are drilling tools, tubing or casing in the well, the annular blowout preventer can use a rubber core to seal various annular spaces of different sizes. When there is no drilling tool in the well, it can fully seal the wellhead for drilling, coring and testing. During well operations, it can also close the annular space formed by the kelly, coring tools, cables, steel wires, etc.

The two types of annular blowout preventers have similar working principles. When a well kick is found and the well needs to be sealed, the high-pressure oil from the control system enters the closed chamber at the lower part of the piston from the lower oil port to push the piston upward, and the spherical rubber core moves along the spherical surface. Moving upwards, the cone-shaped rubber core moves closer to the center under the restriction of the top cover and the extrusion of the inner cone surface of the piston, tightens and surrounds the drilling tool, and realizes the sealing of the drilling tool or fully sealing the wellhead. Reset under the action of its own elastic force to open the wellhead.