Rod lock for ram blowout preventers

Abstract

A blowout preventer to hydraulically seal a wellbore includes a housing configured to be positioned above a wellhead and to surround a drillstring, a plurality of rams positioned perpendicular to an axis of the drillstring to engage the drillstring and hydraulically isolate an annulus between the wellbore and the drillstring when in a closed position, and a roller lock positioned about a thrust rod of each ram configured to maintain the rams in the closed position.

Description

BACKGROUND OF INVENTION [0001] 1. Field of the Invention [0002] The invention relates generally to locking mechanisms for a blowout preventer as deployed in the petroleum exploration and recovery industry. More particularly, the invention relates to a roller lock mechanism to prevent the undesirable reversal of a thrust rod for a ram-type blowout preventer. [0003] 2. Background Art [0004] Wellbores are drilled deep into the earth's crust to recover oil and gas deposits trapped in the formations below. Typically, these wellbores are drilled by an apparatus that rotates a drill bit at the end of a long collection, or string, of threaded pipes known as a drillstring. Because of the energy and friction involved in such an operation, a drilling fluid, commonly referred to as drilling mud, is used to lubricate and cool the drill bit as it cuts the rock formations below. Furthermore, the drilling mud is capable of performing the secondary function of removing the drill cuttings from the bo...

AI Technical Summary

Problems solved by technology

Absent any flow control schemes, fluids from such ruptured formations can blow out of the wellbore like a geyser and spew hydrocarbons and other undesirable fluids into the atmosphere.

However, under certain unforeseen circumstances, the drill bit will encounter pockets of pressurized formations and will cause the wellbore to “kick” or experience a rapid increase in pressure.

Because formation kicks are unpredictable and would otherwise result in disaster, flow control devices known as blowout preventers (“BOP's”), are mandatory on most drilling rigs in use today.

Furthermore, if wellbore is to be shut-in for an extended period of time, maintaining hydraulic pressure over that time period is not always reliable or prudent.

However, accessibility concerns make such a solution less than optimal.

As such, engaging and disengaging the locking screws takes considerable time, time that is not always available in the event of an emergency.

While promising, each of these solutions are considered by many to be less than optimal in that they exhibit a slight amount of slip or “play” in the reverse direction known as backlash before they engage and lock the thrust rods 126 in place.

In the event of a high pressure “kick” to a wellbore, even infinitesimal displacements in rams 120 connected to thrust rods 126 can result in a catastrophic release of wellbore fluids.

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