Types of Blow-Out Preventers
Blowout preventers, also known as BOPs, are crucial for the safety of your crew, rig and the environment as they provide a fail-safe to the systems in use. There are several categories of blowout preventers: ram, and annular. In many cases, BOP stacks often use both types.
A ram BOP uses a set of opposing steel plungers, or rams. The rams stretch to the center of the wellbore restricting flow or retracting open to permit flow. The top and inner faces of the rams and lined with elastomeric seals the push against each other, the wellbore and around the tubing through the wellbore. The outlets along the sides of the BOP body are used for connection to choke lines. Essentially, the ram BOP’s main function is to prevent any unwanted materials from combusting within the system.
Rams are broken down into four types: blind, pipe, shear, and blind shear.
Blind rams are known as sealing rams. They do not have any openings for tubing and can close off well and seal it when there is no drill string or other tubing.
Pipe rams work by closing around the drill pipe and restricting the flow in the annulus between the outside of the drill pipe and wellbore while still allowing flow within the drill pipe.
Shear rams have steel blades to shear the pipe and seals to seal the wellbore after shearing.
Blind shear rams, or shear seal rams, seal a wellbore, even while occupied by a drill string. The drill string is cut through as the rams close the well. The upper part of the drill string is released from the ram, and the lower portion is folded to hang the drill string off the BOP.
Annular blowout preventers work by closing around the drill string. Annual BOPs maintain the seal around the drill pipe as it rotates during drilling. While regulations generally require annular BOPs to be able to close a wellbore, they are typically not as effective at maintaining a seal as ram BOPs.
Annular blowout preventers have two moving parts: the piston, and the packing unit. Comparatively, they are simpler than ram blowout preventers and are generally easier to maintain.
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