Note: Descriptions are shown in the official language in which they were submitted.
CA 02759606 2015-02-06
1051P004CA01
Rotatable and Bendable Casing Connection
Field of the Invention
The present invention relates to a rotatable and bendable
casing connection for use in downhole wellbores.
Background of the Invention
In oil and gas wells where the casing is subject to
movement down hole, failures can occur in the casing or in
the casing connection. The movement of the casing can be
caused by many factors such as shifting formations,
formation pressures, overburden pressures, and thermal
expansion and contraction from steam injection operations.
Stresses induced to the casing from factors such as these,
can buckle the casing wall, or cause connections to part
or leak. In some cases, the casing is cemented into the
well bore, however movements have still been observed and
failures still occur. In other cases, where the casing is
in an open hole with no cement, movement of the casing
liner is often even more severe. Thus, movement from
thermal expansion has been seen to affect both cemented
and non cemented casings.
Fluids and sands produced from the formations tend to
create void spaces in the formation and results in
formation pressure decreases. This often causes higher
overburden pressures to collapse the formations below,
causing further formation movement. When casings reside
in these voided formations, they are subject to various
loads from the formations and are forced to move with the
formations. Any restrictions of movement due to rigidity
of the casing can cause buckling or separation of the
casing. Casings are most likely to fail at their threaded
E2312385.DOC;1 1
CA 02759606 2015-02-06
1051P004CA01
connections, which tend to be the weakest link in the
casing string.
Casing that is subject to thermal expansion and
contraction from steam injection often sees larger
movements than those created from formation movements.
When a casing is cemented in the well, it is held rigidly
in the formation. Thermal expansion of the steel casing,
even when cemented, is difficult to eliminate. The casing
tends to contract or expand within the cement and cause
casing damage, damage to the cementing bonds and even
damage the formations. In the case of a casing in an open
hole, especially in unconsolidated formations such as tar
sands, the formation often sloughs off or collapses around
the casing. Even though these liners are not cemented,
the formation sands collected around the casings can hold
the casing in a rigid state like cement. Since these
casings are in open holes, they are subject to more
formation movement than those that are cemented. Thermal
loads experienced by the casings eventually damage them.
Horizontal well drilling is increasingly becoming a
popular method of producing oil and gas from formations.
Some of these horizontal wells have a shallow vertical
depth, and require large degree build angles to hit the
target. Casing connections have had to be redesigned in
order to handle the severe doglegs from drilling and to
place the casing in the wellbore without bending failures.
When there is a casing failure in a well bore, often, the
well is lost. A number of scenarios have commonly been
observed. The failure of a casing cemented to the surface
can often lead to formation pressures or fluids migrating
to the surface without having any well control. Casings
cemented to the surface that have been crimped can
eventually damage completion equipment, and decrease the
E2312385.DOC;1 2
CA 02759606 2015-02-06
1051P004CA01
entry size of the casing to deploy standard size
equipment. A failure to produce a casing in open holes
can also result in a loss of wells. In a situation where
sand control liners are in place and fail due to movement
or connection failures, the sand control features of that
liner can be lost. Production of sands can make a well
uneconomical to operate. A pinched or crimped sand
control liner can eliminate passage of other tubing or
equipment through the liner, resulting in loss of
production or loss of well. Movement of the production
liner that is hung from the bottom of an intermediate
string can apply side loads to liner hangers and packers,
causing them to leak. When cement bonds are damaged in a
cemented casing, unwanted communication between formations
and between the casing and the formation can occur. When
running a rigid casing string through a build section of a
horizontal well, often the casing is unable to pass
through, or casing connections are damaged due to bending.
All casing connections can withstand bending to some
degree, but in most cases, the connection will leak or
part when bent. Most connections rely on the threads to
deliver a seal, as well as the torque and tensile strength
of the connection. Once the thread has a bending load
applied to it, the integrity of the connection is
drastically reduced or lost completely.
It is therefore desirable to develop a casing connection
that can allow bending and rotation of the casing during
installation and operation. It is further desirable to
provide flexibility to standard, stiff casing so that it
can be deployed in more severe doglegs, or bends, without
the use of slant drilling rigs.
Summary of the Invention
E2312385.D0C4 3
CA 02759606 2015-02-06
1051P004CA01
The present invention thus provides a casing connection
comprising a top face sub, a bottom face sub, an adjusting
collar threadably connecting said top face sub to said
bottom face sub and three sealing areas formed at
connections between the top face sub, the bottom face sub
and the adjusting collar for leak prevention. A degree of
bending and rotation of the casing connection is
controllable by tightening or loosening said threadable
connection of said adjustable collar.
Brief Description of the Drawings
The present invention will now be described in further
detail with reference to the following drawings in which:
Figure 1 depicts one embodiment of the top face sub
portion of the present casing connection;
Figure 2 depicts one embodiment of the bottom face sub
portion of the present casing connection;
Figure 3 depicts one embodiment of a threaded coupling for
use in the present casing connection; and
Figure 4 depicts one embodiment an assembled casing
connection of the present invention.
Detailed Description
The present invention provides a casing connection that
can allow bending and also bending under rotation. Such a
connection must built in a manner that it equals or
exceeds the standard connection specifications, so that it
can either replace standard connections or work in
conjunction with them. The present connection allows
bending from any side loads, to allow casing movement
without connection failure. The present connection
further allows bending in the connection, while the casing
E2312385.DOCO. 4
CA 02759606 2015-02-06
1051P004CA01
is rotated. This allows stiff casing strings to be run
through severe well doglegs. When a well is drilled, the
location and degree of bending of each dog leg is known
from the drilling information. Accordingly, the present
connection can be set along a length of casing to align
with the downhole dog legs, when the casing is in its
final resting position or depth.
The present connection preferably allows for controlled
degrees of bending as well as set loads to allow bending
to happen. The present connection further preferably acts
to seal pressure, withstand applied torque, compression
and tensile loads when running casing into the well. It
must also seal pressure while loads are applied to the
connection during the production phase of the well. These
loads would be applied from thermal applications, and
formation movements.
In a further embodiment, the present connection allows
standard, stiff casing to be deployed into more severe
doglegs or bend, in the build section than typically
possible. For example, the present connection can allow
standard casing to be deployed in bends of up to 15
versus a typical 7 dogleg limit. This allows the forming
builds through shallow vertical depths, without the aid of
slant drilling rigs.
Typical connections in the art consist of a pin and box
connection consisting of a male pin end and a female box
end. The box end can be of two styles, the first of which
is a coupling connection. The coupling is a short x/o sub
with two box ends on it. The coupling is connected to the
pin end of the casing and the other end of the casing is
also a pin end. Once the coupling is connected to the
joint, the joint now becomes a pin x box joint. In the
second style, the box end is machined directly to the
E2312385.DOC;1 5
CA 02759606 2015-02-06
1051P004CA01
casing joint body as a flush connection. Flush
connections are often weaker due to the lesser cross
sectional area of material at the box end, compared to a
coupling cross sectional area. The coupling joint has a
larger outside diameter than the flush joint, at the box
ends of the joint. Coupling connections are usually
stronger than flush connections since they are made from
more material. In some connections, the coupling
connection delivers better sealing than some flush
connections.
Typical thread types used on either a coupling or flush
connection can vary. There are several different profiles
of threads on the market, each delivering a specific
quality. Quality varies to deliver better torque,
tensile, compressive, bending, and sealing capabilities.
All connections rely on the thread profiles to deliver
these qualities.
By contrast, the present connection does not depend on the
thread type to deliver seal, torque and compressive
strengths. Instead, the thread is used only to control
maximum tensile loading.
The new connection does not rely on a thread profile to
deliver its seal, torque, compressive, or bending
qualities. It will rely on threads, only for its tensile
load.
The new connection will consist of three major components:
a top face sub, a bottom face sub and an adjusting collar.
A preferred embodiment of the top face sub 2 is depicted
in Figure 1. The top face sub 2 includes a bored-through
inside diameter that is preferably consistent with the
nominal inside diameter of the casing that it will be used
with. An outside surface of the top face sub 2 includes a
first circular radius face 4 to mate with an internal face
E2312385.D0C4 6
CA 02759606 2015-02-06
1051P004CA01
of the adjusting collar. The top face sub 2 further has a
first end 6 which can be preferably machined, welded or
threaded to match the casing that it will be run with.
Most preferably, the first end 6 is threaded. A second
circular radius face 9 is provided with one or more torque
preventing means, preferably in the form of milled with
torque cogs 8 along an exterior surface of the second
circular radius face 9.
A preferred embodiment of the bottom face sub 10 is
depicted in Figure 2. The bottom face sub 10 includes a
bored-through inside diameter to match the nominal inside
diameter of the casing that will be used with it. An
outside surface of the bottom face sub 10 preferably has a
threaded portion 12 to mate to and thread into the
adjusting collar. The bottom face sub 10 further includes
a machined third circular radius face 14, having one or
more torque preventing means, preferably in the form of
torque cogs 16 milled to an exterior surface of the third
circular radius face 14. The bottom sub face 10 mates
with the top face sub 2 by bringing together the second
circular radius face 9 and associated torque cogs 8 with
the third circular radius face 14 and associated torque
cogs 16 such that the sets of torque cogs 8, 16 interlock.
The bottom face sub 10 further has a second end 18. The
second end 18 can be preferably machined, welded or
threaded to match the casing that it will be run with.
Most preferably, the second end 18 is threaded.
One embodiment of the adjusting collar 20 is depicted in
Figure 3. The adjusting collar 20 has a bore through
inside diameter in which an upper portion of the inside
diameter is larger than the outside diameter of the first
end 6 of the top face sub 2. A center portion of the
inside diameter of the adjusting collar 20 preferably
E2312385.DOC;1 7
CA 02759606 2015-02-06
1051P004CA01
consists of a machined fourth circular radius face 22,
which will mate to the first circular radius face 4 of the
top face sub 2. A lower portion of the inside diameter
includes a threaded connection 24, which mates to the
threaded portion 12 of the bottom face sub 10. In a
preferred embodiment the threaded connection 24 of the
adjusting collar 20 is a female threaded connection and
the threaded portion 12 of the bottom face sub 10 is a
male threaded connection. The outside diameter of the
adjusting collar 20 preferably resembles the coupling of
the casing being used. The adjusting collar 20 can
optionally contain one of more set screws 32 to secure
against any additional movement or makeup to the
connection after initial makeup.
The present connection 30 can be assembled prior to being
run in downhole along with the casings. One embodiment of
the assembled connection 30 of the present invention is
depicted in Figure 4. To assemble the connection 30, the
adjusting collar 20 is first slid over the first end 6
portion of the top face sub 2. The top face sub 2 is then
positioned with the bottom face sub 10, such that their
mating circular radius faces 9, 14 and torque cogs 8, 16
mate with one another. The adjusting collar 20 is then
lowered until the threaded connection 24 of the adjusting
collar 20 mates with the thread portion 12 of the bottom
face sub 10. The adjusting collar 20 is then rotated to
engage the threaded connection 24 with the threaded
portion 12 of the bottom face sub 10. The rotation acts to
tighten the adjusting collar 20 until the internal fourth
circular radius face 22 of the adjusting collar 20 mates
to the first circular face 4 of the top face sub 2.
A dust seal 28 and 0-ring 26 can be added between the
adjusting collar 20 and the top face sub 2 at the
E2312385.00C;1 8
CA 02759606 2015-02-06
1051P004CA01
interface of the first and fourth circular radius faces 4,
22, to prevent sand from entering the connection 30 and
potentially wearing out the connection 30.
A further optional "0" ring can be inserted within each
pair of circular radius faces 4, 22 and 9, 14 to provide
additional sealing.
The amount of torque applied to the threaded connections
12, 24 will determine the amount of force required to bend
or rotate the top and bottom face subs 2, 10 away from
each other along their mating circular radius faces 9, 14
and 4, 22. The amount of force required can be
predetermined and set before running the connection 30
downhole, by the extent of tightening applied to the
threaded connections 12, 24. The one or more torque
preventing means, preferably in the form of mating torque
cogs 8, 16 act to prevent over-torque or unscrewing of the
connection 30 during rotation and bending downhole.
Optionally, any number of known means in the art can be
additionally used to prevent against over-torque, or
loosening of the connections, including but not limited to
set screws or spot welds.
After the present connection30 is assembled, it is
attached to the casing to be used. The present connection
provides three separate sealing areas. The first
25 sealing area consists of the seal created by top face sub
2 and bottom face sub 10 circular radius faces 9, 14. The
second sealing area consists of the seal created by the
top face sub 2 and adjusting collar 20 circular radius
faces 4, 22. Finally, the third sealing area consists of
30 the seal created by the adjusting collar 20 and bottom
face sub 10 threaded connections 12, 24. In the present
connection, a leak path from well annulus to casing
interior or vice versa can only develop if two of the
E2312385.1)0C4 9
CA 02759606 2015-02-06
1051P004CA01
three sealing areas fail. That is, a failure of a
combination of circular radius faces 9, 14, circular
radius faces 4, 22, or circular radius faces 9,14
together with threaded connections 12, 24 would be
required to cause a leak. Typical casing connections
have only one sealing area, the threaded connection and
bending of this threaded connection most commonly
contributes to the formation of a leak path in known
casing connections.
When the casing and the present connections 30 are run
into the downhole well, they will encounter dog legs
located in the well as a result of drilling. As the
casing is run through these dog legs, the stiffness of the
casing can cause the casing to become stuck within the dog
leg. In such cases, the present connection 30 allows some
bending when induced with bending forces, allowing the
casing to conform better to the direction of the bends in
the well. If casing has to be rotated through these
bends, the present connection 30 can be rotated at the
same time it is bending to conform to the wellbore. If
the depths or location of the dog legs are predetermined,
the present connections 30 can be positioned at
predetermined lengths along the casing string that
correspond with the depths or locations of the dog legs.
This reduces the amount of stress on the casing lengths
themselves after the casing has been installed.
In wells where thermal expansion and contraction is
evident, the present connection can absorb some of these
thermal loads which would otherwise be placed on the
threaded portion of typical connections. Most thermal
movement observed in the casing is located in the open
hole sections of the wells, where casing is allowed to
move most freely. In many of these open holes, sand
E2312385.DOC;1 10
CA 02759606 2015-02-06
1051P004CA01
production, fluid production, and formation movements are
evident. As voids are created from displaced solids and
fluids, formations will shift and create unwanted casing
movement.
The movement of a casing within the open hole also affects
the forces acting on the casing liner hangers. Most wells
will produce closer to the heel of the well than at its
toe. Most formation movements are noticed at the heel as
well. The increased movement of the casing at the heel
area tends to offset the position of the casing liner
hanger relative to the cemented intermediate casing by
causing a bending load. This typically results in a
failure to the seal. By placing the present connection 30
directly after the liner hanger and through the heel area,
bending movements are absorbed, placing less stress on the
casing liner hanger and the casing connections in the heel
area.
In thermal wells where the intermediate casing is cemented
to the surface, undesirable loads on the casing have also
been observed. In cemented wells, the casing is acted
upon by the stresses of thermal expansion and contraction,
but is prevented from movement by the cement bond. Since
the intermediate casing typically runs through the build
section of the well, any casing connections used in this
section are already under the strain of bending through
the build section and thermal expansion or contraction
adds to this stress. The result is often connection seal
failures and casing collapse. By placing the present
connections 30 in predetermined areas of the cemented
intermediate casing, bending is allowed and stresses from
the build section and thermal movement can be absorbed
thus protecting the casing bodies and casing connections
from failure.
E2312385.DOC;1 11
CA 02759606 2015-02-06
1051P004CA01
The present connections 30 can also be used in a number of
different applications such as mining or producing salt
caverns or any circumstance where casing are subject to
bending for any number of reasons.
The present connection 30 can be optionally manufactured
directly onto plain end casings and used as a total casing
connection, or it can be assembled to existing threaded
casings and specifically placed throughout the casing
string as required.
There are no elastomeric elements used for sealing in the
present connection. All seals are preferably made of
metal, and more preferably made from steel, and can thus
withstand extreme temperatures and pressures.
In the foregoing specification, the invention has been
described with a specific embodiment thereof; however, it
will be evident that various modifications and changes may
be made thereto without departing from the scope of the
invention.
E2312385.DOC;1 12
