Flexible Connection For Rotating Blowout Preventer

Abstract

A rotating blowout preventer or wellhead mounted on and above but not rigidly attached to a blowout preventer stack. The attachment between the blowout preventer and the blowout preventer stack is flexible but pressuretight. The attachment allows lateral movement of the blowout preventer or rotating head and the drill string or kelly so that stresses resulting from a crooked or nonaligned kelly or eccentric location of a drill string are not created in the rotating blowout preventer or head while stationary or while rotating.

Description

BACKGROUND OF THE INVENTION

When drilling oil and/or gas wells on shore the kelly may be at times crooked or nonaligned or the position of the drill string may be eccentric and when drilling such wells offshore from a floating vessel the drill string must be permitted lateral movement to accommodate lateral movement of the floating vessel caused by wave and wind action. The present invention meets the requirements of a nonrigid, connected, pressure tight, rotating blowout preventer. The blowout preventer is installed on top of the rigid blowout preventer stack and has the capacity for lateral movement to compensate for any noncentered position of the drill string (or kelly) or lateral movement of the drill string in offshore operations. Vertical movement of the drill string in offshore operations may be accommodated for in conventional ways.

SUMMARY OF THE INVENTION

In accordance with the teachings of the invention, the apparatus for use in conducting drilling operations comprises a rigid blowout preventer stack and a laterally movable rotating blowout preventer and a flexible joint arranged between said blowout preventer stack and said rotating blowout preventer to permit lateral movement of said rotating blowout preventer with respect to said rigid blowout preventer stack. In offshore operations the laterally movable rotating blowout preventer permits lateral movement of the drill string and on land operations such lateral movement compensates for a crooked or nonaligned kelly or an eccentrically located drill string.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view illustrating the features of the invention;

FIG. 2 is an elevational view showing the apparatus of the invention positioned subsea for offshore operations; and

FIG. 3 illustrates a rotating head for use in subsea operations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

There is shown in FIG. 1 a rigid ram-type blowout preventer stack 10 mounted on a wellhead 11. A flexible connector 12 forms a pressuretight connection between blowout preventer stack 10 and a rotating blowout preventer 13.

Flexible connector 12 may be a thick sleeve of high-strength rubber, reinforced if necessary. The sleeve is bonded to flanges on the BOP stack 10 and rotating blowout preventer 13. The size of the sleeve depends on the working pressure required and the type rubber used. Preferably, the flexibility of the sleeve allows about 5.degree. lateral movement of the rotating blowout preventer 13 in any lateral direction without reducing the strength of the sleeve below the working pressure required. No torque is applied to the sleeve. Alternatively, the flexible connector may be a knuckle joint or ball and socket joint. Such type connector permits limited deviation from a centerline axis of the blowout preventer stack and does not expose any of the flexible joint to wear nor does it restrict the size opening over that maintained with no deviation.

The kelly or drill string indicated at 14 may be crooked or nonaligned or eccentric as it extends through rotating blowout preventer 13, flexible connector 12, BOP stack 10 and wellhead 11. No stresses caused by such nonalignment or eccentricity position are created or transmitted to the rigid blowout preventer.

A subsea arrangement of a rotating head, flexible joint and BOP stack combination is illustrated in FIG. 2. In that figure, a drill pipe 20 is shown suspended from a floating drilling barge 21 and extending to and through subsea well apparatus which includes a rotating head 22, a flexible joint or connection 23, a subsea connector 24, a BOP stack 25, another subsea connector 26 and a wellhead 27. The subsea well apparatus is lowered into position on guidelines 30 (other known guide means could be used instead) which connect wellhead 27 to drilling barge 21. The subsea apparatus is provided with guide arms 31, connected to guide sleeves 32 through which the guidelines extend. A flexible mud return line 35 connects into the subsea apparatus below rotating head 22 and above flexible joint 23 and extends to drilling barge 21. Rotating head 22 is provided with hydraulic control lines 36 and 37 and a lubrication line 38, all of which extend to drilling barge 21. Additional control lines, not shown, may be provided to control operation of the blowout preventers in the BOP stack 25 and in the subsea connectors 24 and 26.

For a more detailed description, of rotating head 22, reference is made to FIG. 3. As shown in that figure, a sealing element 40, formed of resilient materials similar to that used in bag-type blowout preventers, fits inside of and is retained in and rotates with a bearing element 41 to which it is attached. Bearing element 41 is contained within a housing 42 and is covered by an upper retainer plate 43. A number of roller (and/or thrust) bearings 44 are arranged between the interior walls of housing 42 and bearing element 41 and retainer plate 43 is in contact with bearing element 41 by way of roller bearings 44a. A number of seals 45 are also arranged between the inner walls of housing 42 and retainer plate 43 and the outer walls of bearing element 41. A conduit 50 formed in bearing element 41 fluidly communicates the interior of scaling element 40 and a passageway 51 formed in the walled housing 42, which in turn connects to hydraulic control line 36. Another conduit or passageway 52 is formed in bearing element 41 and fluidly communicates the lower end of bearing element 41 exposed to well pressures and the interior of sealing element 40. Another passageway 53 formed in the wall of housing 42 connects to lubrication line 38 at one end and the space between the inner wall of housing 42 and the outer wall of bearing element 41. A hydraulically operated latch member 55 includes a hydraulically driven lug member 56 which is movable into and out of a recess 57 formed in retainer plate 43 and is supplied with hydraulic fluid through hydraulic line 37. A flange (or hub or other type connection) 60 formed in the lower end of housing 42 connects to mud return line 35.

In operation, wellhead 27 is lowered through the water from drilling barge 21 on guidelines 30 and secured to the land underlying the water, in accordance with conventional practice. Then BOP stack 25, together with subsea connector 26, subsea connector 24, flexible joint 23 and rotating head 22, including housing 42, sealing element 40, bearing element 41, and retainer plate 43 may be lowered on drill pipe 20 and guidelines 30 with the mud return line 35 connected to the subsea apparatus. Sealing of sealing element 40 against drill pipe 20 or other tool is achieved by applying fluid pressure through hydraulic line 36 and passageways 51 and 50 or alternatively pressure from the well bore acting on sealing element 40 through passageway 52 may be used. Rotation of drill pipe 20 rotates sealing element 40 and bearing element 41 against which sealing element 40 is sealed. Bearing surfaces between bearing element 41 and housing 42 are lubricated by a liquid similar to water-soluble oil which is supplied from drilling barge 21 through lubricating line 38 and passageway 53. The retainer plate or cap 43 may be released by withdrawing lug 56 from recess 57 by hydraulic operation of the latch 55 through hydraulic lines 37 to permit replacing sealing element 40. Sealing element 40, bearing element 41 and retaining plate 43 are run and retrieved on drill pipe 20. When in subsea position, sealing element 40 permits passage of tool joints. Drill collars on drill pipe 20 raise sealing element 40 and bearing element 41 out of housing 42 when coming out of the hole with drill pipe 20.

The rotating element may have grooves which spiral along its outer surface to carry away solids or other foreign material.

Claims

Having fully described the apparatus, operation, objects and advantages of our invention, we claim:

1. Apparatus for use in conducting drilling operations comprising a rigid blowout preventer stack;

a rotating laterally movable blowout preventer arranged above said blowout preventer stack;

a flexible joint arranged between said blowout preventer stack and said rotating blowout preventer to permit lateral movement of said rotating blowout preventer relative to said rigid blowout preventer stack; and

drill pipe extending through said rotating blowout preventer, said flexible joint and said blowout preventer stack, said rotating blowout preventer preventing flow of fluid through the space surrounding said drill pipe.

2. Apparatus as recited in claim 1 in which said rotating blowout preventer, flexible joint and blowout preventer stack are located subsea.

3. Apparatus as recited in claim 1 in which said flexible joint permits about 5.degree. lateral movement of said rotating head in any lateral direction.

4. Apparatus as recited in claim 3, in which said flexible joint comprises a sleeve member.

5. Apparatus as recited in claim 4 in which said blowout preventer stack is connected to a subsea wellhead.

6. Apparatus as recited in claim 5, in which said sleeve member comprises rubber.

7. Apparatus for use in conducting drilling operations comprising:

a rigid blowout preventer stack;

a rotating head arranged above said blowout preventer stack;

a rubber sleeve member arranged between said blowout preventer stack and said rotating head permitting lateral movement of about 5.degree. of said rotating head in any lateral direction relative to said rigid blowout preventer stack; and

a subsea wellhead, said blowout preventer stack being connected to said subsea wellhead.