WHAT IS BOP - KNOW EVERYTHING IN DETAIL Blowout preventers come in a variety of styles, sizes and pressure ratings. Several individual units serving various functions are combined to compose a blowout preventer stack. Multiple blowout preventers of the same type are frequently provided for redundancy, an essential factor in the effectiveness of protective devices. The Primary Functions Of Blowout Preventer system are to:● ● ● ● ● ● ● ● ●
Confine well fluid to the wellbore; Provide means to add fluid to the wellbore; Allow Control volumes of fluid to be withdrawn from the wellbore; Regulate and monitor Wellbore pressure; Centre and hanging of the drill string In the Well bore; Shut in the well (e.g. seal the void annulus, between drill pipe and casing); “Kill” the well (prevent the flow of formation fluid, influx, from the reservoir into the wellbore) ; Seal the wellhead (close off the wellbore); Sever the casing or drill pipe (in case of emergencies).
In drilling a typical high-pressure well, drill strings are routed through a blowout preventer stack toward the reservoir of oil and gas. As the well is drilled, drilling fluid, "mud", is fed through the drill string down to the drill bit, "blade", and returns up to the wellbore in the ring-shaped void, annulus, between the outside of the drill pipe and the casing (piping that lines the wellbore). The column of drilling mud exerts downward hydrostatic pressure to counter opposing force from the formation being drilled, allowing drilling to proceed. This is less desirable because of the higher surface pressures likely needed and the fact that much of the mud originally in the annulus must be forced into receptive formations in the open hole section beneath the most in-depth casing shoe.
Types Ram blowout preventer The Ram BOP was invented by James Smither Abercrombie and Harry S. Cameron in 1922 and was brought to market in 1924 by Cameron Iron Works. A ram-type BOP is similar in operation to a gate valve but uses a pair of opposing steel plungers, rams. The rams extend toward the centre of the wellbore to restrict flow or retract open in order to permit flow. The inner
and top faces of the rams are fitted with packers (elastomeric seals) that press against each other, against the wellbore, and around tubing running through the wellbore. Rams, or ram blocks, are of four common types: pipe, blind, shear, and blind shear.
Annular blowout preventer The Annular blowout preventer was invented by Granville Sloan Knox in 1946; a U.S. patent for it was awarded in 1952. Often around the rig, it is called the "Hydril", after the name of one of the BOP manufacturers. An annular-type blowout preventer can close around the drill string, casing or a non-cylindrical object, such as the kelly. Drill pipe including the larger-diameter tool joints (threaded connectors) can be "stripped" through an annular preventer by careful control of the hydraulic closing pressure. Annular blowout preventers are also effective at maintaining a seal around the drill pipe even as it rotates during drilling. Regulations typically require that an annular preventer be able to completely close a wellbore, but annular preventers are generally not as effective as ram preventers in maintaining a seal on an open hole.
Control Methods ● ● ● ●
Hydraulic Control Signal: sent from the surface through a hydraulic umbilical. Electrical Control Signal: sent from the surface through a control cable. Acoustical Control Signal: sent from the surface based on a modulated/encoded pulse of sound transmitted by an underwater transducer. ROV Intervention remotely operated vehicles (ROVs) mechanically control valves and provide hydraulic pressure to the stack (via “hot stab” panels).
Top Blowout Preventer manufacturers USA ● ● ● ● ●
Schlumberger National Oilwell Varco Baker Hughes Worldwide Oilfield Machine, Inc. Control Technology Inc.
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Conclusion Since BOPs are essential for the safety of the crew and natural environment, as well as the drilling rig and the wellbore itself, authorities recommend, and regulations require, that BOPs be
regularly inspected, tested and refurbished. Tests vary from daily analysis of functions on critical wells to monthly or less frequent testing on wells with a low likelihood of control problems. Exploitable reservoirs of oil and gas are increasingly rare and remote, leading to increased subsea deepwater well exploration and requiring BOPs to remain submerged for as long as a year in extreme conditions.