Note: Descriptions are shown in the official language in which they were submitted.
CA 02366096 2002-12-17
1 CASING HEAD CONNECTOR WITH LANDING BASE
2 FIELD OF THE INVENTION
3 This invention provides a means of connecting a casing head, or other
attachment, to string
4 of tubular body such as a casing pipe, and in addition provides a means of
transferring a portion of
the load of that attachment onto a conductor pipe or other tubular body.
6 BACKGROUND OF THE INVENTION
7 The typical fashion in which a well is drilled in the ground, for example
for oil and gas, is to
8 first drive or drill a shallow large diameter pipe, comrnonly called the
eonductor pipe, into the
9 ground and to then drill a smaller and deeper hole inside the boundary
defined by the conductor
pipe so that a smaller diameter and longer pipe, commonly called the surface
casing or casing pipe,
11 can be placed into the hole. The annular space between the surface casing
and the conductor pipe
12 is then be filled with cement. Further drilling beyond the depth of the
surface casing is done to a
13 sufficient depth that geological formations encountered may cause
pressurized fluid to escape into
14 the hole and travel the surface. To control this fluid, and to prevent its
escape into the atmosphere,
the drilling is done through a sealed pressure vessel at the surface that is
known as the blowout
16 preventer stack. In addition, drilling at these depths require the use of a
weighted column of fluid,
17 known as drilling mud, to control the well and to aid drilling by cooling
the drilling bit and to remove
18 cut rock. A pressure vessel known as the casina head, attaches to and seals
on around the surface
19 casing to provide a means of hooking up the blowout pi-eventer stack and
the drilling mud lines.
This casing head is commonly attached to the surface casing by either
threading it onto the casing
21 pipe or by welding it to the casing pipe. The problems with these methods
of attaching the casin~
22 head are that they require time, are often expensive and create the
possibility of installation errors.
23 A third method is to attach the casing head using a means for gripping the
casing pipe with
24 mechanically activated teeth. A seal between the casing head and the casing
pipe is then provided
separately, usually in the form of an elastomeric or metal seal ring located
in the casing head above
26 the mechanical gripping mechanism. Such an assembly is well known in the
industry and commonly
27 used but is described adequately in U.S. Patents 4,799,714 issued to
Collet, 5,332,043 issued to
CA 02366096 2002-12-17
1 Ferguson, and Canadian Patent 2,01 5,966 issued to Anderson et al. Each of
these patents
2 describes a common method for mechanically attaching the casing head to the
surface casing. They
3 disclose the use of conical slip segments which surround the casing pipe,
each slip segment being
4 provided with a plurality of grooves on their straight inside surface
(casina pipe-contacting surface)
that act as teeth that bite into the surface casing. A housing, or actuation
sleeve, with a reverse
6 conical mating surface to the conical surface on the outside of the slip
segments, is then driven
7 against the slip segments (or the slip segments are driven against the
sleeve/housing). This forces the
8 slip segments against the surface casing pipe causing the grooves to
frictionally grip (or the teeth to
9 bite into) the casing pipe, and thus to secure the casing pipe to the casing
head. These slip segments
are commonly referred to as "slips" and the system is commonly described as a
slip lock casina
11 connector.
12 This slip lock casing connector has advantages over the previously
described casing
13 connectors. These include the reduced installation time, the ability to
ensure that a seal between the
14 casing pipe and the casing head has been achieved, and the ability to
remove the casina head if
drilling is abandoned.
16 Once the casing head has been attached, by any of the three means described
above,
17 drilling is continued to a deeper depth. An additional, smaller, string of
pipe is then set in the hole
18 and the weight of this pipe is supported by the casing head. Further
drilling steps could include
19 setting of additional strings of pipe within the casing pipe, and
installing additional heads above the
casing head. The weight from the additional strings and heads can prove to be
too large for the
21 surface casing string to support alone, so some means of transferring this
load onto the conductor
22 pipe may be required. The equipment that transfers this load is known as
the landing base. The
23 landing base usually consists of a landing plate set on top of the
conductor pipe, together with a
24 means for setting the casing head on, or securing the casing head to, this
landing plate. It can be
extremely difficult to supply a landing base with a casing head using a slip
lock connector as
26 described above because the landing base interferes with the operator's
access to the mechanical
27 actuation means of the casing connector. In addition, the casing head
normally requires a special
28 means of attachment to the landing base, and as such, the landing base
cannot be fitted onto a
29 standard slip lock casing head. The solution to these problems often leads
to an awkward and
complex system that can be extremely costly.
CA 02366096 2002-12-17
Commonly, the mechanical actuation means of the slip lock casing connector
consists of
2 studs or bolts that pull the actuation sleeve against the slip segments or
push the slip segments
3 against the actuation sleeve. In order to reduce the size of the entire
assembly, these bolts or studs
4 normally extend out below the bottom of the casing head. The use of a
landing base interferes with
access to the bolts of the mechanical actuation means, which requires the
bolts to extend out of the
6 top face of the bottom casing head (i.e., upwards out of the top face of a
flange on the bottom of
7 the casing head). This in turn requires the casino connector parts to be
larger so that the bolts or
8 studs clear the outside diameter of the casing head leading to a redesign of
the slip lock casing head
9 and an increased cost.
SUMMARY OF THE INVENTION
11 An objective of this invention is to establish a mechanical means of
attaching a casing head
12 or other attachment onto a piece of surface casing pipe or other pipe. The
invention allows a
13 landing base to be easily attached to the casing head. This invention
reduces manufacturing costs of
14 this combined casing head and landing base when compared to other available
designs. Preferably,
the invention allows the operator to establish and adjust the portion of load
transferred from the
16 surface casing onto the conductor pipe. Finally, the invention is easy to
use and less awkward then
17 available designs.
18 Broadly stated, the invention provides a connector head for connecting an
inner tubular
19 body within an outer, concentric tubular body, and for transferring at
least a portion of the load from
the inner tubular body onto the outer tubular body. The connector head of the
invention comprises:
21 a generally tubular connector head formed with a central bore through which
the inner
22 tubular body extends, the connector head having an inwardly extending stop
shoulder formed in the
23 central bore to allow the connector head to rest on the upper end of the
inner tubular body;
24 slip connecting means in the connector head for gripping the outer wall of
the innei- tubular
body;
26 a base plate formed with a central bore throuah which the inner tubular
body extends, the
27 base plate being located below the connector head and adapted to rest on
the upper end of the
28 outer tubular body, the base plate being formed with a plui-ality of
radially spaced holes;
3
CA 02366096 2002-12-17
1 a plurality of threaded stud members connected to and extending radially
downwardly from
2 the lower end of the connector head, for mating arrangement with the
radially spaced holes of the
3 base plate;
4 a retainer ring formed with a central bore through which the inner tubular
body extends, the
retainer ring being located between the connector head and the base place, and
beinc, connected to
6 or in contact with the slip connecting means such that, upward movement of
the retainer ring engaQes
7 the slip connecting means into a gripping mode with the inner tubular body,
the retainer rin- being
8 formed with a plurality of radially spaced holes through which the threaded
stud members extend,
9 allowing the retainer ring to slide upwardly and downwardly on the threaded
stud members; and
an upper and lower nut threaded onto each of the threaded stud members between
the
11 retainer ring and the base plate, such that tightening of the upper nuts
against the retainer ring pushes
12 the retainer ring upwardly to engage the slip connecting means into the
gripping mode with the inner
13 tubular body, and downward tightening of the lower nuts against the base
plate transfers at least a
14 portion of the load from the inner tubular body through the threaded stud
members and lower nuts
onto the base plate and the outer tubular body.
16 In a preferred embodiment, the connector head of the invention is a casing
head device for
17 use in a well bore, wherein the inner tubular body is a casing pipe and
wherein the outer tubular
18 body is a conductor pipe. In this embodiment the invention provides a
casing head device for
19 connecting and sealing to a casing pipe and for transferring at least a
portion of the load from the
casing pipe to an outer, concentric conductor pipe.
21 BRIEF DESCRIPTION OF THE DRAWINGS
22 Figure 1 is a front view of the assernbly of the present invention
including a casing head with
23 the slip lock retention bottom connection attached to the adjustable
landing base. This figure shows
24 the components in their positions just after the ca.sing head has been
placed over the casing pipe and
before the slip lock connector and the landing base have been energized so as
to grip the casing
26 pipe and transfer load to the landing base plate and to the conductor pipe.
The view is a half and
27 partial section in order to illustrate the components. It should be noted
that for clarity some
28 components might be shown out of plane; and
4
CA 02366096 2002-12-17
1 Figure 2 is a front view (in the same oricntation as in Figure 1) of the
described invention
2 installed in a typical wellhead stack with equilmlent typically used in
drilling operations. The
3 wellhead equipment is shown in half section with the blowout preventer stack
unsectioned.
4 DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention is described with reference to Figure 1, so as to describe the
installation of the
6 casing connector, landing base assembly of this invention, and its operation
in subsequent drilling
7 operations. After a conductor pipe 1 and surface casing pipe 2 is drilled
for and set in the drill hole,
8 a base plate 3 is picked up using the lifting eyes 4 and centered over the
surface casing pipe 2 and
9 conductor pipe 1. The base plate 3 has a hole 5 (or central bore) through
its center beina slightly
larger in diameter than the surface casing pipe 2. The base plate 3 is placed
onto the top of the
1 1 conductor pipe 1 with the surface casing pipe 2 protruding through its
center hole 5. The base plate
12 3 thus acts as a landing base. A casing head 6 is then placed over the
surface casing pipe 2 such
13 that a stop shoulder 7 in the casing head 6 rests on the top of the surface
casing pipe 2. Threaded
14 studs 8, which are threaded into the bottom of the casing head 6, are lined
up with, and fit into, the
radial holes 9 which are formed in the base plate 3. Upper nuts 10 and lower
nuts 11 are threaded
16 to move upwardly and downwardly respectively on studs 8 between the base
plate 3 and a
17 retaining ring 16 located at the bottom of the casing head 6. These nuts
10, 11 are initially in a high
18 enough vertical position to ensure that the casing head 6 does not yet rest
on the base plate 3.
19 The casing head 6 has seal means for sealing the casing head 6 against the
casing pipe 2.
The seal means preferably include at least two seals 12 located in sealing
grooves 13 below the
21 stop shoulder 7 which seal against the casing pipe 2. These seals 12 can
consist of elastomeric
22 seals, metal-to-metal seals or a combination of the two. The seals 12 may
or may not require
23 external energization to achieve a seal. A pressure test is preferably then
performed on the seals 12
24 to ensure the casing head 6 is sealing on the surface casing pipe 2. For
that purpose, one or more
pressure test ports 14 are provided, which can be accessed from ttie outside
of the casing head 6.
26 After the pressure integrity of the seals 12 has been verified the outer
capscrews 15 in the retainer
27 ring 16 are backed off so they no longer extend above the top face of the
retainer ring 16. These
28 capscrews 15 are used to ensure an initial proper gap between the top face
of the retainer ring 16
5
CA 02366096 2002-12-17
1 during installation and to aid in removing the casing head 6. The upper set
of nuts 10 are tightened
2 so that as they move tip the studs 8, they engage the retainer ring 16 and
push it upwardly. The
3 retainer ring 16 in turn engages the actuation sleeve 17 and pushes it
upwardly.
4 In Figure 1, the retainer ring 16 and actuation sleeve 17 are shown as
separate parts joined
by capscrews 18. This is for ease of manufacture, but they may form a single
component in
6 alternate embodiments of the invention. The need for the capscrews 18 wouid
then be eliminated.
7 As the actuation sleeve 17 is pushed upwardly, its inner conical surface 19
engages on the matina
8 outer conical surface 20 of the slip segments 21. These slip segments 21
(preferably four) are
9 attached to the casing head 6 by the horizontal capscrews 22. The slip
segments 21 are restrained
from vertical movement by the slip stop 23 in the casing head 6. Thus, as the
nuts 10 are tightened
11 against the retainer ring 16, the upward vertical movement of the actuation
sleeve 17 pushes the slip
12 segments 21 inwardly. This upward movement caused the strai-ht grooves 24
(or teeth) of the slip
13 segments 21 to be pushed against the surface casing pipe 2 and to
frictionally grip the casina pipe 2
14 or bite into it.
As the slip segments move inwardly, they pull the head 25 of the horizontal
capscrews 22
16 against the outer washer 26, which compresses the rubber washer 27 as it is
pushed against the
17 inner washer 28. This allows the slip segment 21 to move inwardly without
looseninQ the horizontal
18 capscrews 22. After the slip segments 21 have fully compressed the rubber
washer 27, the
19 horizontal capscrews 22 are partially loosened before continuing tightening
of the upper set of nuts
10. After the upper set of nuts 10 have been tightened to the desired torque
the casing head 6 is
21 secured to the surface casing pipe 2 and any vertical force applied to the
casing head 6 will not
22 remove it from the surface casing pipe 2. This vertical force can result in
the event that well
23 pressure is present in the hole during subsequent drilling operations. Any
applied vertical force will
24 pull the casing head 6 upwardly, thereby pulling the studs 8, upper set of
nuts 10, the retainer ring
16 and actuation sleeve 17 upwardly. As described above, this causes the slip
segments 21 to grip
26 the surface casing pipe 2 with greater force so any vertical force
attempting to separate the casing
27 head from the surface casing pipe 2 will only secure it more tightly. Once
the casing head 6 has
28 been secured to the surface casing pipe 2, the lower set of nuts 1 1 are
tightened so that they move
29 down on the studs 8 and engage on the base plate 3.
Figure 2 shows the casing head connector, landing base assembly of this
invention in use
6
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1 with subsequent drilling operations underway. A portion of the load placed
on the casing head 6 is
2 now transferred onto the conductor pipe 1 rather than resting entirelv on
the surface casing pipe 2.
3 This load may be the result of additional strings of pipe 29 landed on the
load shoulder 30 of the
4 casing head 6, or from the blowout preventer stack 3 1 and additional heads
32 landed onto the
upper face 33 of the casing head 6. The amount of load transferred to the
conductor pipe 1 is a
6 function of the relative elasticities of the surface casinQ pipe 2 and the
conductor pipe 1. While this
7 load is usually unknown, the assembly of this invention allows the
apportioning of the load to be
8 adjusted. The load carried by the conductor pipe 1 can be measured by
measuring the torque on
9 the lower set of nuts 11, and can be controlled or adjusted by changing the
torque applied. The
relationship between the torque of a nut and the resulting vertical load is a
commonly used
11 engineering formula known to all skilled in the art.
12 Referring again to Figure 1, load can be transferred from the surface
casing pipe 2 to the
13 conductor pipe 1 by two methods. In the first method, load can be
transferred from the casing
14 head 6 onto the conductor pipe I through the studs 8, onto the lower set of
nuts 11, onto the base
plate 3 and onto the conductor pipe 1. The second method allows the load to be
transferred onto
16 the slip segments 21 which act against the surface casing pipe 2 and
transfer the load to the
17 actuation sleeve 17. This actuation sleeve then transfers the load to the
retainer ring 16, which
18 transfers the load to the upper set of nuts 10. This load is then
transferred onto the conductor pipe
19 1 by means of the first method described above. The amount of load
transferred by each method
can be determined by calculating the relative elasticities of each system. The
stiffer the system
21 governing one of the two methods the more load will be transferred by that
method. It is important
22 to make the system of load transfer through the first method much stiffer
than the second. This is
23 because the amount of additional load placed on the surface casing pipe 2
by the slip segments 21
24 should be limited so the casing pipe 2 is not crushed excessively.
The casing head 6 may be removed by loosening the lower set of nuts 11 and
then
26 loosening the upper set of nuts 10. If necessary the outer capscrews 15 on
the bottom of the
27 retainer ring 16 can be tightened in order to pull the retainer ring 16 and
actuation sleeve 17,
28 attached by capscrews 18, downwardly. The slip segnients 21 then release
the surface casing pipe
29 2, and the casing head 6 and the base plate 3 can be removed and reused.
It should be understood that the wellhead embodiment of the invention shown in
Figure 2 is
7
CA 02366096 2002-12-17
1 merely a preferred embodiment, and that the assembly of this invention can
be used in any
2 application where a component (attachment) needs to be securely attached to
a tubular body, and
3 the load resulting from this attached component needs to be transferred, in
whole or in part, to a
4 second tubular body.
All publications mentioned in this specification are indicative of the level
of skill in the art of
6 this invention. All publications are herein incorporated by reference to the
same extent as if each
7 publication was specifically and individually indicated to be incoiporated
by reference.
8 The terms and expressions used are, unless otherwise defined herein, used as
terms of
9 description and not limitation. There is no intention, in using such terms
and expressions, of
excluding equivalents of the features illustrated and described.
8
