Note: Descriptions are shown in the official language in which they were submitted.
CA 02636949 2014-12-17
INDEPENDENT WELLHEAD DRILLING ADAPTER
Field of the Invention
[00021 This invention relates in general to oil and gas well drilling, and, in
particular to
an adapter for connecting a blowout preventer to an independent wellhead.
Background
[00031 Conventional adaptors for coupling devices such as, for example, a blow
out
preventer ("BOP") to a wellhead typically require a threaded connection. As a
result, such
adaptors require rotation of the BOP relative to the wellhead during
installation. This
connection requiring rotation is time consuming and requires a large well bay
to allow the
BOP to rotate and connect to such a threaded connector. Since many new oil
rigs have small
well bays this creates logistical problems. Other conventional adaptors for
coupling devices
to a wellhead require that the wellhead threads must be non-standard thereby
adding cost and
complexity. The present exemplary embodiments are directed to overcoming some
of the
limitations of conventional adaptors used to couple devices to wellheads.
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10003A] In one broad aspect, the invention pertains to a wellhead
assembly, comprising a wellhead
having an external threaded end portion, a drilling adapter that lands on the
end portion of the wellhead,
a connection ring mounted to the drilling adapter and encircling the end
portion of the wellhead, and a
plurality of segments carried by and circumferentially positioned around the
connection ring. Each
segment has an internal threaded portion and is movable between inner and
outer positions. While the
segments are in the outer position, the adapter is able to be lowered onto the
wellhead with the segments
out of engagement with the end portion of the wellhead. Thee are a plurality
of screws, each operably
coupled to the connection ring and a corresponding one of the segments, for
moving the segments to the
inner position with the internal threaded portions of the segments into
engagement with the external
threaded end portion of the wellhead.
[0003131 In a further aspect, the invention provides an assembly for
connecting a blow out
preventer to a wellhead having an external threaded end portion, comprising a
drilling adapter adapted
to be coupled to an end of the blow out preventer, a connection ring coupled
to the drilling adapter
adapted to receive the end portion of the wellhead, and a plurality of
segments carried by and
circumferentially positioned around the connection ring, each segment having
an inner end containing an
internal threaded portion and being movable between inner and outer positions.
While the segments are
in the outer position, the adapter is able to be lowered onto the wellhead
with the segments out of
engagement with the end portion of the wellhead. A plurality of screws are
secured to an outer wall of
the connection ring. Each screw is coupled to one of the segments for moving
the segments an inward
radial direction to the inner position, with the internal threaded portions in
engagement with the external
threaded end portion of the wellhead.
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[0003C] In a still further aspect, the invention comprehends a method of
connecting a drilling
adapter to a wellhead having an external threaded end portion, comprising
mounting a connector assembly
to the drilling adapter, the connector assembly comprising a plurality of
segments each segment having
an inward facing threaded portion and being movable between inner and outer
positions, while the
segments are in the outer position, landing the adapter on the end portion of
the wellhead and positioning
the connector assembly around the end portion of the wellhead, the segments
being out of engagement
with the threaded end portion of the wellhead while in the outer position, and
moving the segments to
the inner position and causing the inward facing threaded portions to engage
the external threaded end
portion of the wellhead.
[0003D] Yet further, there is provided a method of drilling a well,
comprising forming the well
to a first depth and installing a string of outer casing, connecting a
wellhead to the string of outer casing,
the wellhead having an external threaded end portion, and mounting a
connection ring to a drilling
adapter. The connection ring contains a plurality of segments spaced
circumferentially around the
connection ring, each of the segments being movable between outer and inner
positions and having an
internal threaded portion. Each of the segments is in engagement with a screw
extending through an
outer wall of the connection ring and, with the segments in the outer
position, landing the adapter on the
wellhead with the connection ring encircling the threaded end portion of the
wellhead and the internal
threaded portions of the segments out of engagement with the threaded end
portion of the wellhead. The
screws are rotated to move the segments in an inward radial direction to the
inner position, with the
internal threaded portions of the segments in engagement with the threaded end
portion of the wellhead.
A wear bushing is placed in a bore of the adapter and mounts a blow out
preventer to an upper end of
the adapter. Drill pipe is lowered through the blow out preventer, the adapter
and the wellhead, and the
well is drilled to a total depth. A string of production casing is installed
within the outer casing.
The screws are rotated to move the segments to the outer position and remove
the adapter. A packoff
is installed in the bore of the wellhead, and a top connector ring with an
internal threaded portion is
placed on the wellhead over the packoff, and rotates the top connector ring to
secure internal threaded
portion of the top connector ring to the threaded end portion of the wellhead.
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Brief Description of the Drawings:
[0004] Figure 1 is a sectional view illustrating an adapter connecting a
blowout preventer to an
independent wellhead, in an exemplary embodiment of the present technique.
[0005] Figure 2 is a view of the wellhead of Figure 1, shown with the adapter
and the blowout
preventer removed and casing installed, in an exemplary embodiment of the
present technique.
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Detailed Description of the Invention:
[0006] In the drawings and description that follows, like parts are marked
throughout the
specification and drawings with the same reference numerals, respectively. The
drawings are not
necessarily to scale. Certain features of the invention may be shown
exaggerated in scale or in
somewhat schematic form and some details of conventional elements may not be
shown in the
interest of clarity and conciseness. The present invention is susceptible to
embodiments of different
forms. Specific embodiments are described in detail and are shown in the
drawings, with the
understanding that the present disclosure is to be considered an
exemplification of the principles of
the invention, and is not intended to limit the invention to that illustrated
and described herein. It is
to be fully recognized that the different teachings of the embodiments
discussed below may be
employed separately or in any suitable combination to produce desired results.
The various
characteristics mentioned above, as well as other features and characteristics
described in more detail
below, will be readily apparent to those skilled in the art upon reading the
following detailed
description of the embodiments, and by referring to the accompanying drawings.
[0007] Referring to Figure 1, a first casing 11 extends into the well for a
first distance and has an
upper end landing ring illustrated in Figure 1. A second casing 13 extends
into the well to a second
depth and has an upper end with a landing ring 15 that lands on the upper end
of first casing landing
ring 11. The upper end of casing 13 is threaded and in this example is
connected to a casing collar
17. Casing collar 17 has internal threads on its upper end.
[0008] A wellhead 19 has a lower set of external threads 21 that secure to the
internal threads in
casing collar 17. Wellhead 19 is preferably a type referred to as an
"independent wellhead", which
has specifications dictated by the American Petroleum Institute. Currently,
the specifications are
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governed by API Specification 11IW, June, 2000 "Specification for Independent
Wellhead
Equipment". Wellhead 19 may be a casing head or it may be a tubing head. Lower
threads 21 may
be external or internal and still fall within the specification. Wellhead 19
has one or more outlets 23,
25 extending through its sidewall. Outlet 23 is shown connected to a nipple 27
for connection to
additional equipment. Outlet 25 is shown connected to a valve 29. Wellhead 19
has an interior bowl
or profile 31 extending above outlets 23, 25. In this embodiment, profile 31
is a conical taper,
however other configurations for profile 31 are allowed within the API
specification. Wellhead 19
has an upper thread set 33 on its exterior extending downward from its rim.
Upper thread set 33 is
also governed by the API specification and comprises specified API pipe
threads.
[0009] In this embodiment, a drilling adapter 35 mounts to wellhead 19 during
drilling. Adapter
35 lands on the rim or upper end of wellhead 19. A seal 37 on the lower side
of adapter 35 seals
against the upper end of wellhead 19. Adapter 35 has a connector ring 39 that
is secured to it for
connecting adapter 35 to wellhead 19. In this example, connector ring 39 is
secured by threads 41 to
a threaded portion on the exterior of adapter 35. Lock pins 43 extend through
the sidewall of
connector ring 39 into engagement with vertical grooves formed below threads
41 to prevent lock
ring 39 from rotating relative to adapter 35. Connector ring 39 could be
connected to adapter 35 in
manners other than by threads, if desired.
[0010] Connector ring 39 has a lower portion 40 that extends below adapter 35.
Lower portion
40 extends inward under the lower end of adapter 35 and surrounds wellhead
threads 33. Lower
portion 40 has an internal annular recess 45 that has an open side facing
wellhead threads 33. A
plurality of segments 47 are carried in annular recess 45. Each segment 47 is
arcuate section of a
ring and has a portion of a thread set 49 on its inner face. Thread set 49 is
formed to match threads
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33 of wellhead 19. Each segment 47 is movable radially from the outer position
shown on the left
side of Figure 1 to the inner position shown on the right side. In the inner
position, segment threads
49 will be in engagement with wellhead threads 33. In an exemplary embodiment,
the profile of the
threads of the segments 47 are configured relative to the threads on the
wellhead 19 such that, as the
threads of the segments 47 are tightened against the threads on the wellhead
19, the connector ring
39 is pulled down, the seal 37 engages and thereby seals against the top of
the wellhead. When in
the inner position, the sides of segments 47 abut each other and the thread
sets 49 define a
continuous set of threads that mate with wellhead threads 33. Segments 47 may
be manufactured by
first cutting a set of threads on the inner diameter of a ring, then cutting
the ring into individual
segments. In the outer position, segment threads 49 will be spaced radially
outward from wellhead
threads 33.
[0011] The mechanism to move each segment 47 radially inward and outward in
this embodiment
comprises a screw 51 that extends through a threaded hole in connector ring 39
radially outward
from recess 45. Each screw 51 has an inner end 53 that engages a recess within
one of the segments
47 and is rotatable relative to the segment 47. Preferably each screw 51 has a
polygonal outer end
for receiving a wrench to rotate screw 51.
[0012] Adapter 35 also has a bore 55 that aligns with the upper end of
wellhead profile 31. Prior
to drilling through wellhead 19, the operator installs a drilling or wear
bushing 57, shown by dotted
lines. Wear bushing 57 slides down over profile 31 to protect profile 31 from
damage during
drilling. Wear bushing 57 has an upper end that is releasably retained with
adapter 35. In this
example, the retainer comprises a plurality of radially extending screws 59
extending through adapter
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35. Each screw 59 has a pointed end that engages an annular recess on the
exterior of wear bushing
57. Screws 59 extend radially through threaded holes in adapter 35.
[0013] A blowout preventer 61 mounts on top of adapter 35. Blowout preventer
61 may be a
variety of types and is shown by dotted lines. In this example, blowout
preventer 61 secures to a
flange portion of adapter 35 by means of bolts 63.
[0014] In
operation, the operator will initially drill the well and install casings 11
and/or 13. The
operator then installs wellhead 19 on casing 13 at the rig floor and run in
the wellhead 19, collar 17,
and landing ring 15 as illustrated in Figure 1. The operator places adapter 35
on wellhead 19 and
rotates screws 51 to cause segments 47 to move into mating engagement with
wellhead threads 33.
There is no need to rotate adapter 35 relative to wellhead 19. The operator
inserts well bushing 57
and rotates screws 59 inward to secure wear bushing 57. Adapter 35 may have
previously connected
to blowout preventer 61 prior to landing adapter 35 on wellhead 19. The
operator drills through
wellhead 19 to the total depth.
[0015] The operator removes wear bushing 57 and in this example, installs a
string of casing 65,
shown in Figure 2. Casing 65 may be run through BOP 61 (Figure 1). Casing 65
is cemented in
place and a hanger mechanism 67 supports casing 65. In this example, hanger 67
comprises tapered
slips that engage profile 31 in wellhead 19. BOP 61, adapter 35 and connector
ring 39 (Figure 1) are
removed as a unit and reused for drilling another well. The operator installs
a packoff 69 between an
upper portion of wellhead profile 31 and casing 65. A top connector 71 has an
inner portion that fits
over packoff 69 to retain packoff 69 and to deform it into sealing engagement
with wellhead profile
31. Top connector 71 has a lower portion with internal threads 73 that engage
upper threads 33 on
wellhead 19.
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[0016] Other types of completions after drilling are available, but these
completions would
also utilize wellhead upper threads 33. Furthermore, as mentioned, rather than
supporting
casing, wellhead 19 could support a string of tubing.
[0017] The
present exemplary embodiments provide an assembly for connecting a
component to a wellhead comprising external threads on an end portion thereof
in which the
assembly may be connected to the threaded portion of the wellhead without
having to rotate
the component.
[0018] It is understood that variations may be made in the above without
departing from
the scope of the invention. The embodiments as described are exemplary only
and are not
limiting. Many variations and modifications are possible and are within the
scope of the
invention. Accordingly, the scope of protection is not limited to the
embodiments described,
but is only limited by the claims that follow, the scope of which shall
include all equivalents
of the subject matter of the claims.
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