U.S. patent application number 13/488348 was filed with the patent office on 2013-12-05 for downhole safety joint.
This patent application is currently assigned to THRU TUBING SOLUTIONS, INC.. The applicant listed for this patent is Roger L. Schultz, Brock Watson. Invention is credited to Roger L. Schultz, Brock Watson.
Application Number | 20130319655 13/488348 |
Document ID | / |
Family ID | 48692645 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130319655 |
Kind Code |
A1 |
Schultz; Roger L. ; et
al. |
December 5, 2013 |
DOWNHOLE SAFETY JOINT
Abstract
A downhole safety joint for use in a wellbore, including an
upper tubular member having an upper threaded end and a lower
external threaded section; a lower tubular member having a lower
threaded end and an upper interior threaded section for engaging
with the lower external threaded section to form a break joint, the
break joint having one or more of a maximum compressive stress
limit and a tensile stress limit; and one or more circumferential
stress reliefs disposed into the outer diameter of at least one of
the upper tubular member and the lower tubular member for
transmitting a side load applied to the break joint to one or more
of the circumferential stress reliefs less than one or more of the
compressive stress limit and the tensile stress limit.
Inventors: |
Schultz; Roger L.;
(Ninnekah, OK) ; Watson; Brock; (Oklahoma City,
OK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schultz; Roger L.
Watson; Brock |
Ninnekah
Oklahoma City |
OK
OK |
US
US |
|
|
Assignee: |
THRU TUBING SOLUTIONS, INC.
Oklahoma City
OK
|
Family ID: |
48692645 |
Appl. No.: |
13/488348 |
Filed: |
June 4, 2012 |
Current U.S.
Class: |
166/242.6 |
Current CPC
Class: |
E21B 17/042 20130101;
E21B 17/06 20130101 |
Class at
Publication: |
166/242.6 |
International
Class: |
E21B 17/06 20060101
E21B017/06 |
Claims
1. A downhole safety joint for use in a wellbore, comprising: an
upper tubular member having an upper threaded end and a lower
external threaded section; a lower tubular member having a lower
threaded end and an upper interior threaded section for engaging
with the lower external threaded section to form a break joint, the
break joint having one or more of a maximum compressive stress
limit and a tensile stress limit; and one or more circumferential
stress reliefs disposed into the outer diameter of at least one of
the upper tubular member and the lower tubular member for
transmitting a side load applied to the break joint to one or more
of the circumferential stress reliefs less than one or more of the
compressive stress limit and the tensile stress limit.
2. The downhole safety joint as recited in claim 1 wherein the one
or more circumferential stress reliefs are circumferential recessed
areas in the outer diameter of the one of the upper tubular member
and the lower tubular member.
3. The downhole safety joint as recited in claim 1 wherein the one
or more circumferential stress reliefs is a circumferential
recessed area disposed between the upper threaded end and the lower
external threaded section of the upper tubular member.
4. The downhole safety joint as recited in claim 1 wherein the one
or more circumferential stress reliefs is a circumferential
recessed area disposed between the lower threaded end and the upper
internal threaded section of the upper tubular member.
5. The downhole safety joint as recited in claim 1 wherein the one
or more circumferential stress reliefs have an outer diameter less
than at least one of the upper tubular member and the lower tubular
member.
6. The downhole safety joint as recited in claim 1 wherein the one
or more circumferential stress reliefs flex or bend to transmit the
side load exceeding one or more of the maximum compressive stress
limit and tensile stress limit to the one or more circumferential
stress reliefs.
7. The downhole safety joint as recited in claim 1 wherein the one
or more circumferential stress reliefs flex or bend to transmit 90
percent of the side load exceeding one or more of the maximum
compressive stress limit and tensile stress limit to the one or
more circumferential stress reliefs.
8. A downhole safety joint for use in a wellbore, comprising: an
upper sub having an upper threaded end and a lower end having a
plurality of external threads; a lower sub having a lower threaded
end and an upper end having a plurality of internal threads for
engaging with the plurality of external threads to form a break
joint; and a channel formed by gaps between the sides of the
plurality of joined external and internal threads for transmitting
a fluid therebetween the gaps between the plurality of external and
internal threads.
9. The downhole safety joint as recited in claim 8 wherein the gaps
are formed by the plurality of external threads have a width less
than the width of the corresponding plurality of internal
threads.
10. The downhole safety joint as recited in claim 8 wherein the
gaps are formed by the plurality of internal threads have a width
less than the width of the corresponding plurality of external
threads.
11. The downhole safety joint as recited in claim 8 wherein the
channel extends along all of the plurality of external threads and
internal threads.
12. The downhole safety joint as recited in claim 8 wherein the
gaps are from about 0.10 inches to about 0.02 inches.
13. The downhole safety joint as recited in claim 8 wherein the
gaps are from about 0.08 inch to about 0.03 inch.
14. The downhole safety joint as recited in claim 8 wherein the
gaps are from about 0.06 inch to about 0.04 inch.
15. A downhole safety joint for use in a wellbore, comprising: an
upper sub having an upper threaded end and a lower section having a
plurality of external threads, the lower section having a
non-threaded section below the lower threaded section; a lower sub
having a lower threaded end and an upper end having a plurality of
internal threads for engaging with the plurality of external
threads to form a break joint; and a longitudinal slot disposed in
the outer diameter of the non-threaded section to provide a fluid
pathway to a central passageway of the downhole safety joint.
16. The downhole safety joint as recited in claim 15 wherein the
longitudinal slot is a groove formed into the non-threaded
section.
17. The downhole safety joint as recited in claim 15 further
comprising: a seal disposed about the non-threaded section, wherein
the longitudinal slot is disposed below the seal in the
non-threaded section.
18. The downhole safety joint as recited in claim 15 wherein the
non-threaded section terminates in a tapered end.
19. A downhole safety joint for use in a wellbore, comprising: an
upper tubular member having an upper threaded end and a lower
section having a plurality of external threads, the lower section
having a non-threaded section below the lower threaded section; a
lower tubular member having a lower threaded end and an upper end
having a plurality of internal threads for engaging with the
plurality of external threads to form a break joint, the break
joint having one or more of a maximum compressive stress limit and
a tensile stress limit; one or more circumferential stress reliefs
disposed into the outer diameter of at least one of the upper
tubular member and lower tubular member for transmitting a side
load applied to the break joint to one or more of the
circumferential stress reliefs less than one or more of the
compressive stress limit and the tensile stress limit; a channel
formed by gaps between the plurality of external and internal
threads for transmitting a fluid therebetween when engaging the
upper tubular member with the lower tubular member; and a
longitudinal groove disposed in the outer diameter of the
non-threaded section to provide a fluid pathway to a central
passageway of the downhole safety joint.
20. The downhole safety joint as recited in claim 19 wherein the
one or more circumferential stress reliefs are circumferential
recessed areas in the outer diameter of the one of the upper
tubular member and the lower tubular member.
21. The downhole safety joint as recited in claim 19 wherein the
one or more circumferential stress reliefs is a circumferential
recessed area disposed between the upper threaded end and the lower
external threaded section of the upper tubular member.
22. The downhole safety joint as recited in claim 19 wherein the
one or more circumferential stress reliefs is a circumferential
recessed area disposed between the lower threaded end and the upper
internal threaded section of the upper tubular member.
23. The downhole safety joint as recited in claim 19 wherein the
one or more circumferential stress reliefs have an outer diameter
less than at least one of the upper tubular member and the lower
tubular member.
24. The downhole safety joint as recited in claim 19 wherein the
gaps are formed by the plurality of internal threads have a width
less than the width of the corresponding plurality of external
threads.
25. The downhole safety joint as recited in claim 19 wherein the
one or more circumferential stress reliefs flex to transmit less
than the maximum tensile stress limit of the applied tensile stress
to the break joint.
26. The downhole safety joint as recited in claim 19 wherein the
gaps are from about 0.06 inch to about 0.04 inch.
27. The downhole safety joint as recited in claim 19 wherein the
one or more circumferential stress reliefs flex or bend to transmit
the side load exceeding one or more of the maximum compressive
stress limit and tensile stress limit to the one or more
circumferential stress reliefs.
28. The downhole safety joint as recited in claim 19 wherein the
one or more circumferential stress reliefs flex or bend to transmit
90 percent of the side load exceeding one or more of the maximum
compressive stress limit and tensile stress limit to the one or
more circumferential stress reliefs.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] This invention relates, in general, to a safety joint used
in a wellbore and, in particular, to a downhole safety joint used
with a work string in a wellbore that traverses a subterranean
hydrocarbon bearing formation.
BACKGROUND OF THE INVENTION
[0002] Without limiting the scope of the present invention, its
background will be described in relation to a downhole safety
joint, as an example.
[0003] There are many different operations involved in drilling and
completing an oil and/or gas well; some of these operation include
drilling, surveying, and completing a well. Oftentimes, these wells
are drilled at extreme depths and many times they are drilled
directionally such that one or more bends exist in the wellbore
that can cause a pipe string, drillstring, tool string, service
string, and the like ("work string") to become stuck deep in the
wellbore. Many times expensive tools, instruments, and the like are
located towards the lower end of these work strings. Thus, once
stuck, it oftentimes is desirable to retrieve as much of this
equipment and instruments as possible.
[0004] One method for recovering this equipment involves running a
string shot on a wireline down as far as possible through the inner
diameter of the stuck work string and firing an explosive to
separate the joint where it can be backed off. Typically, this
process includes putting left hand torque on the work string,
applying substantially neutral weight to the desired joint proximal
to the string shot, and then firing the string shot, which causes
the joint to break enabling the recovery of the work string and any
equipment and instruments above the joint to be recovered. One of
the problems associated with this procedure is that many times the
work string may include equipment, tools, instruments, and their
related components disposed in the inner diameter thus blocking the
downward passage of the string shot and wire line past that point
that would prevent locating and firing the string shot below that
point. Any expensive equipment and instruments located below that
point would not be able to be retrieved typically using this
method.
[0005] Another retrieval method is to include what is known as a
"safety joint" in the work string. A safety joint is typically a
tubular member consisting of an upper and lower sub that are
disconnectable from each by a variety of known means. In one such
means, coarse threads join the upper and lower sub, such that when
a string becomes stuck in a wellbore, left hand torque may be
applied to the work string which then uncouples (unscrews) the
upper sub from the lower sub, thus enabling the upper sub and the
work string above it to be retrieved leaving the lower sub and
parts of the work string below it in the wellbore. Typically, the
torque required to unscrew the safety joint is a fraction of the
torque required to break the threaded connections between the
joints of the work string, which the safety joint is connected,
thus unscrewing the safety joint but not any other tubular members
of the work string. Sometimes, these safety joints are placed lower
in the work string than expensive equipment and instruments, thus
ensuring that the equipment and instruments may be retrieved once
the safety joint has been disconnected.
[0006] Also, once retrieved at the surface and the expensive
equipment and instruments have been recovered, the upper sub may be
re-coupled to a work string having a substantially open inner
diameter, and run back into the wellbore for reconnecting with the
lower sub. Doing so then provides a substantially open inner
diameter all the way to the bottom hole assembly ("BHA") at or near
the bottom of the wellbore or distal end of the stuck work string.
This method may then include running a string shot in and shooting
it off to recover more of the stuck work string via a wireline or
other known means. In another method, a jar may be attached
upstring of the retrieved upper sub and run back into the wellbore
for reconnecting with the lower sub of the safety joint and jarring
the stuck work string.
[0007] One problem associated with these types of safety joints is
that the threaded sections of the subs making up a break joint may
include seals disposed about the ends of the threaded sections that
may trap fluids or mud within the safety joint when the upper sub
is being reconnected with the lower sub in the wellbore. The
trapped mud or fluid located within the upper and lower subs is
under extreme pressure and may cause the subs to become
hydraulically locked. Drilling mud is often designed to fill and
plug voids to prevent fluid loss into the formations being
penetrated by the wellbore. This characteristic can cause
difficulty in making up a safety joint downhole because the mud
tends to plug off and seal inside the threads as they are screwed
back together. This can further add to the problem of hydraulic
locking in the safety joint because the fluid is trapped inside the
threaded connection and cannot be exhausted through the safety
joint.
[0008] When hydraulically locked, operators may apply more torque
in response to the hydraulic lock in an attempt to reach a proper
seat of the upper and lower sub, which may damage the safety joint,
subs, and/or other equipment in the wellbore.
[0009] Another problem associated with hydraulically locked subs is
that when torque is backed off due to the operator's belief that
the threaded ends of the subs are properly engaged, it will in fact
mean that the safety joint is not properly made up and may become
disconnected when it is retrieved from the wellbore, thus causing
tubular members, equipment, instruments, and the like to be dropped
into the wellbore.
[0010] Additionally, conventional safety joints are oftentimes run
into wellbores having highly deviated, horizontal, or tortuous
trajectories to access substantially horizontal hydrocarbon bearing
formations. Under these situations, the safety joint experiences a
tensile load (e.g., pulling work string out of wellbore) or a
compressive load (e.g., adding weight to the work string) in the
axial direction of the safety joint while in the wellbore. In
addition, the safety joint will experience a bending or side load
when it is in these situations or environments. These bending loads
are caused by the distal ends of the safety joint being in contact
with a sidewall of the wellbore, casing, liner, etc., while
concurrently the substantially opposite side of the safety joint's
central section or break joint encounters a substantially opposite
linear side load. The side load creates a compressive stress on one
side of the break joint and a tensile stress on the opposite side
of the break joint.
[0011] Further, the stress caused by the axial loading will add to
or subtract from the stress caused by the bending load. If there is
a large enough positive or negative axial load, the safety joint
will remain completely or constantly in tensile or compressive
stress throughout the safety joint, but the sides or top/bottom
(substantially horizontal orientation) of the safety joint will
experience different stress levels due to the bending load or
stress. It is this cyclical variation in stress state caused by the
cyclic bending loads that causes break joints to tighten, loosen,
cause total failure of the break joint. Also, the shoulders of the
break joint may become damaged by the cyclical loading causing the
break joint to become looser than required, thus causing unreliable
break joint connections that are difficult to reliably make up or
break under desired torque ratings.
SUMMARY OF THE INVENTION
[0012] The present invention disclosed herein is directed to a
downhole safety joint that provides reduced wear to break joints of
safety joints while running into highly deviated wellbores,
improved coupling efficiency, and reduced chances of hydraulic lock
when reconnecting safety joint. It further provides for improved
fluid flow within the downhole safety joint during make up so as to
avoid hydraulic locking.
[0013] In one embodiment the present invention may be directed to a
downhole safety joint for use in a wellbore, including an upper
tubular member having an upper threaded end and a lower external
threaded section; a lower tubular member having a lower threaded
end and an upper interior threaded section for engaging with the
lower external threaded section to form a break joint, the break
joint having one or more of a maximum compressive stress limit and
a tensile stress limit; and one or more circumferential stress
reliefs disposed into the outer diameter of at least one of the
upper tubular member and the lower tubular member for transmitting
a side load applied to the break joint to one or more of the
circumferential stress reliefs less than one or more of the
compressive stress limit and the tensile stress limit.
[0014] In one aspect, the one or more circumferential stress
reliefs may be circumferential recessed areas in the outer diameter
of the one of the upper tubular member and the lower tubular
member. In another aspect, the one or more circumferential stress
reliefs may be a circumferential recessed area disposed between the
upper threaded end and the lower external threaded section of the
upper tubular member. I yet another aspect, one or more
circumferential stress reliefs may be a circumferential recessed
area disposed between the lower threaded end and the upper internal
threaded section of the upper tubular member.
[0015] In still yet another aspect, the one or more circumferential
stress reliefs may have an outer diameter less than at least one of
the upper tubular member and the lower tubular member. Preferably,
the one or more circumferential stress reliefs may flex or bend to
transmit the side load exceeding one or more of the maximum
compressive stress limit and tensile stress limit to the one or
more circumferential stress reliefs. Also preferably, the one or
more circumferential stress reliefs may flex or bend to transmit 90
percent of the side load exceeding one or more of the maximum
compressive stress limit and tensile stress limit to the one or
more circumferential stress reliefs.
[0016] In another embodiment, the present invention is directed to
a downhole safety joint for use in a wellbore, including an upper
sub having an upper threaded end and a lower end having a plurality
of external threads; a lower sub having a lower threaded end and an
upper end having a plurality of internal threads for engaging with
the plurality of external threads to form a break joint; and a
channel formed by gaps between the plurality of external and
internal threads for transmitting a fluid therebetween when
engaging the upper sub to the lower sub.
[0017] In one aspect, the gaps may be formed by the plurality of
external threads have a width less than the width of the
corresponding plurality of internal threads. In another aspect, the
gaps may be formed by the plurality of internal threads have a
width less than the width of the corresponding plurality of
external threads. In yet another aspect, the channel may extend
along all of the plurality of external threads and internal
threads. Preferably, the gaps may be from about 0.10 inches to
about 0.02 inches. Also preferably, the gaps may be from about 0.08
inch to about 0.03 inch. In another aspect, the gaps may be from
about 0.06 inch to about 0.04 inch.
[0018] In yet another embodiment, the present invention is directed
to a downhole safety joint for use in a wellbore, including an
upper sub having an upper threaded end and a lower section having a
plurality of external threads, the lower section having a
non-threaded section below the lower threaded section; a lower sub
having a lower threaded end and an upper end having a plurality of
internal threads for engaging with the plurality of external
threads to form a break joint; and a longitudinal slot disposed in
the outer diameter of the non-threaded section to provide a fluid
pathway to a central passageway of the downhole safety joint.
[0019] In one aspect, the longitudinal slot may be a groove formed
into the non-threaded section. In another aspect, the downhole
safety joint may further include a seal disposed about the
non-threaded section, wherein the longitudinal slot is disposed
below the seal in the non-threaded section. In still another
aspect, the non-threaded section may terminate in a tapered
end.
[0020] In still yet another embodiment, the present invention may
be directed to a downhole safety joint for use in a wellbore,
including an upper tubular member having an upper threaded end and
a lower section having a plurality of external threads, the lower
section having a non-threaded section below the lower threaded
section; a lower tubular member having a lower threaded end and an
upper end having a plurality of internal threads for engaging with
the plurality of external threads to form a break joint, the break
joint having one or more of a maximum compressive stress limit and
a tensile stress limit; one or more circumferential stress reliefs
disposed into the outer diameter of at least one of the upper
tubular member and lower tubular member for transmitting a side
load applied to the break joint to one or more of the
circumferential stress reliefs less than one or more of the
compressive stress limit and the tensile stress limit; a channel
formed by gaps between the plurality of external and internal
threads for transmitting a fluid therebetween when engaging the
upper tubular member with the lower tubular member; and a
longitudinal groove disposed in the outer diameter of the
non-threaded section to provide a fluid pathway to a central
passageway of the downhole safety joint.
[0021] In one aspect, the one or more circumferential stress
reliefs may have circumferential recessed areas in the outer
diameter of the one of the upper tubular member and the lower
tubular member. In another aspect, the one or more circumferential
stress reliefs may be a circumferential recessed area disposed
between the upper threaded end and the lower external threaded
section of the upper tubular member. In yet another aspect, the one
or more circumferential stress reliefs may be a circumferential
recessed area disposed between the lower threaded end and the upper
internal threaded section of the upper tubular member. In still yet
another aspect, the one or more circumferential stress reliefs may
have an outer diameter less than at least one of the upper tubular
member and the lower tubular member.
[0022] Preferably, the gaps may be formed by the plurality of
internal threads have a width less than the width of the
corresponding plurality of external threads. Also preferably, the
one or more circumferential stress reliefs may flex to transmit
less than the maximum tensile stress limit of the applied tensile
stress to the break joint. Additionally, the gaps may be from about
0.06 inch to about 0.04 inch. Also, the one or more circumferential
stress reliefs may flex or bend to transmit the side load exceeding
one or more of the maximum compressive stress limit and tensile
stress limit to the one or more circumferential stress reliefs.
Further, the one or more circumferential stress reliefs may flex or
bend to transmit 90 percent of the side load exceeding one or more
of the maximum compressive stress limit and tensile stress limit to
the one or more circumferential stress reliefs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] For a more complete understanding of the features and
advantages of the present invention, reference is now made to the
detailed description of the invention along with the accompanying
figures in which corresponding numerals in the different figures
refer to corresponding parts and in which:
[0024] FIG. 1A is a schematic illustration of an offshore platform
in operable communication with a downhole safety joint in a
connected work string according to an embodiment;
[0025] FIG. 1B is a schematic illustration of an offshore platform
in operable communication with a downhole safety joint in a
disconnected work string after operation of the downhole safety
joint according to an embodiment;
[0026] FIGS. 2A-2B are quarter-sectional views of a disconnected
upper sub and lower sub of downhole safety joint according to an
embodiment;
[0027] FIG. 3A is a cross-sectional view of a downhole safety joint
of FIGS. 2A-2B according to an embodiment;
[0028] FIG. 3B is a cross-sectional view of a downhole safety joint
of FIGS. 2A-2B under a bending load according to an embodiment;
[0029] FIG. 4 is a partial quarter-sectional perspective view of a
downhole safety joint of FIG. 3A according to an embodiment;
and
[0030] FIG. 5 is an enlarged view of a portion of a threaded
section of a break joint of the downhole safety joint of FIG. 3A
according to an embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0031] While the making and using of various embodiments of the
present invention are discussed in detail below, it should be
appreciated that the present invention provides many applicable
inventive concepts which can be embodied in a wide variety of
specific contexts. The specific embodiments discussed herein are
merely illustrative of specific ways to make and use the invention,
and do not delimit the scope of the present invention.
[0032] In the following description of the representative
embodiments of the invention, directional terms, such as "above,"
"below," "upper," "lower," etc., are used for convenience in
referring to the accompanying drawings. In general, "above",
"upper", "upward," and similar terms refer to a direction toward
the earth's surface along a wellbore, and "below," "lower,"
"downward," and similar terms refer to a direction away from the
earth's surface along the wellbore. Additionally, the term
"proximal" refers to a linear, non-linear, or curvilinear distance
or point nearer to a point of reference or direction that is closer
to a relative term or object, and the term "distal" refers to a
linear, non-linear, or curvilinear distance or point farther to a
point of reference or direction that is farther to a relative term
or object.
[0033] Referring to FIGS. 1A and 1B, a downhole safety joint 100 in
use with an offshore oil and gas drilling or production platform is
schematically illustrated and generally designated 50. A
semi-submersible platform 52 is located over a submerged oil and
gas formation 54 located below sea floor 56. Although downhole
safety joint 100 is discussed herein with reference to oil and gas
drilling or production platform 50, downhole safety joint 100 may
be used with any type of onshore or offshore oil and/or gas rig as
are commonly known to those skilled in the art. A subsea conduit or
marine riser 58 extends from deck 60 of platform 52 to a wellhead
62 that may include a blowout preventer 64 disposed above wellhead
62, in one embodiment.
[0034] Disposed above blowout preventer 64 may be a flexible or
ball joint (not shown) for providing a flexible sealing connection
between marine riser 58 and blowout preventer 64, in one
embodiment. Platform 52 may have a hoisting apparatus 68a-68c
(collectively hoisting apparatus 68), a derrick 68 for raising and
lowering a work string 70, and a rotary table 72 for rotating work
string 70, in one embodiment. A wellbore 74 extends through the
various earth strata including oil and gas formation 54. A casing
76 may be cemented within a substantially vertical section of
wellbore 76 by cement 78, in one embodiment.
[0035] Casing 76 and cement 78 are shown disposed about work string
70 to a particular depth of wellbore 74; however, casing 76 and
cement 78 may extend to any desirable depth of wellbore 74.
Further, in this specification, the term "casing" may also mean
"liner" and may be used interchangeably to describe tubular
materials, which are used to form protective casings and the like
in wellbore 74. Casing 76 may be made from any material such as
metals, plastics, composites, or the like, and may be expanded or
unexpanded as part of an installation procedure, and may be
segmented or continuous. Also, it is not necessary for casing 76
and/or line to be cemented in wellbore 74. Any type of casing 76 or
liner may be used in keeping with the principles of downhole safety
joint 100. Additionally, wellbore 74 may be lined by any other
casing types, liners, and the like as are commonly known to those
skilled in the art. Casing 76 may include additional tubular
members disposed below wellhead 62 having different diameters as is
commonly known to those skilled in the arts. Additionally, work
string 70 may include a bottom hole assembly ("BHA") 80. Generally,
BHA 80 may be a bit, bit sub, mud motor, stabilizers, drill
collars, drillpipe, jars, crossovers, instruments, equipment, and
the like.
[0036] Although FIGS. 1A-1B depict downhole safety joint 100 in a
substantially horizontal portion of wellbore 76, it should be
understood by those skilled in the art that downhole safety joint
100 may be equally well suited for use in wells having other
directional configurations including horizontal wells, deviated
wellbores, slanted wells, multilateral well, and the like.
[0037] FIG. 1A depicts downhole safety joint 100 in a coupled or
connected to work string 70. The location of downhole safety joint
100 in work string 70 may have any types of instruments, tubulars,
equipment and the like located above or below downhole safety joint
100 in work string 70. In one aspect, downhole safety joint 100 may
be placed below in work string 70 of instruments, tubulars,
equipment and the like that may be desired to be retrieved should
the part of work string 70 below downhole safety joint 100, such as
BHA 80 become stuck in wellbore 74. As shown in FIG. 1A, downhole
safety joint 100 is in its connected state in work string 70.
[0038] FIG. 1B depicts downhole safety joint 100 in a uncoupled or
disconnected operation. In FIG. 1B, downhole safety joint 100 has
been operated and an upper sub 102 (FIG. 2A) of downhole safety
joint 100 has been disconnected from a lower sub 104 (FIG. 2B) of
downhole safety joint 100 have been disconnected with each other
separated by a distance. Upper sub 102 is shown connected with the
upper part of work string 70 while lower sub 104 is shown connected
with the lower end of work string 70, including BHA 80.
[0039] Referring now to FIG. 2, upper sub 102 of downhole safety
joint 100 is shown. Upper sub 102 includes a substantially tubular
axially threaded end or connector 106 that is operable for coupling
to a lower end of a tubular member of work string 70 located above
upper sub 102. Upper sub 102 further includes a tubular body 108
that defines an inner central passageway 110 that extends through
upper sub 102 and allows the passage of fluids therethrough. An
upper section of tubular body 108 of has an outer diameter
(W.sub.1) extending a length (L.sub.1) from the upper end of
threaded connector 106 to substantially the beginning of a
circumferential stress relief section 112. Stress relief section
112 further extends a length (L.sub.2) that extends from the end of
length (L.sub.1). Preferably, the outer diameter of stress relief
section 112 has a reduced width (W.sub.2) than that of the width
(W.sub.1) of the outer diameter of tubular body 108.
[0040] Extending from the lower section of stress relief section
112 is tubular body 108 having an outer diameter substantially
similar to outer diameter (W.sub.1). Also, upper sub 102 includes a
male or pin end 116 that includes a plurality of coarse
right-handed exterior threads 118. Upper sub 102 may also include
one or more seals 114 for providing sealing relationship between
pin end 116 of upper sub 102 and box end 130 of lower sub 104 when
the two are engaged as described further below. Upper sub 102 may
further include a non-threaded section 120 below threads 118 that
may have a seal 123 disposed about it for providing a sealing
relationship with box end 130 of lower sub 104. Additionally, upper
sub 102 may include a nose or tapered end 122 for assisting
engaging pin end 116 in engaging box end 130 when downhole safety
joint 100 is being recoupled or reconnected in wellbore 74.
[0041] Upper sub 102 further includes one or more longitudinal
recesses, slots, or grooves 124 that are disposed into non-threaded
section 120 below seal 123 and that extend longitudinally to
tapered end 122 for providing a release channel for fluid trapped
between tapered end 122 and seal 123 and the interior of box end
130 when upper sub 102 is being re-coupled or reconnected with box
end 130 of lower sub 104 as further described below with reference
to FIG. 4.
[0042] Lower sub 104 includes a tubular body 126 that may have an
outer diameter that is substantially similar to the section of
tubular body 108 above seal 114 such that when upper sub 102 and
lower sub 104 are fully connected, tubular body 126 forms a
consistent outer diameter with tubular body 108, in one example.
Lower sub 104 includes an inner central passageway 128 that extends
through lower sub 104 and allows the passage of fluids
therethrough. When upper sub 102 and lower sub 104 are coupled
together, passageway 110 and passageway 128 form a common central
passageway for allowing fluids to pass through the entire length of
downhole safety joint 100 as best shown in FIG. 3A. Box end 130
includes a plurality of coarse right-handed interior threads 132
for matingly engaging with threads 118 of pin end 116.
[0043] As discussed above, seals 114, 123 provide a sealed section
or compartment for threads 118 and threads 132 when pin end 116 is
fully engaged with box end 130. This sealing arrangement prevents
fluids from entering the space between seals 114 and seal 123 when
downhole safety joint 100 is run into wellbore 74. This sealing
arrangement keeps threads 118 and threads 132 substantially free
from fluids that may be present during the running in of downhole
safety joint 100 that may deteriorate threads 118 and threads 132
if present for a prolonged period.
[0044] Lower sub 104 may further include a circumferential stress
relief section 134 that may begin at the lower portion of the upper
section of tubular body 126 and extend a length (L.sub.3) to the
upper portion of the lower section of tubular body 126 as shown in
FIG. 2B. Stress relief section 134 has an outer diameter having an
outer diameter having a width (W.sub.3). Preferably, width
(W.sub.3) of outer diameter of stress relief section 134 is less
than the width (W.sub.4) of the outer diameter of tubular body 126
as shown in FIG. 2B. In generally, lower sub 104 may have a section
of tubular body 126 that extends a length (L.sub.4) below stress
relief section 134. Lower sub 104 also includes a substantially
tubular axially threaded end or connector 136 that is operable for
coupling to an upper end of a tubular member of work string 70
located below lower sub 104.
[0045] Now turning to FIGS. 3A-3B, a completely coupled downhole
safety joint 100 is shown where upper sub 102 and lower sub 104
have been coupled together at a break joint 138 consisting of pin
end 116 fully engaged with box end 130. In one aspect, break joint
138 has a maximum tensile stress limit such that exceeding the
limit will cause damage to one or more of pin end 116, threads 118,
box end 130, and threads 132. The maximum tensile stress limit is
dependent upon the engineered dimensions and materials of these
elements and would be commonly known to those skilled in the
arts.
[0046] As shown, tubular body 126 and tubular body 108 may have a
substantially similar outer diameter such that they provide a
substantially uniform outer diameter. In one embodiment, downhole
safety joint 100 may include just stress relief section 112 and not
stress relief section 134. In another embodiment, downhole safety
joint 100 may include stress relief section 134 and not stress
relief section 112. In yet another embodiment, downhole safety
joint 100 may include both stress relief section 112 and stress
relief section 134.
[0047] In one embodiment, width (W.sub.2), length (L.sub.2), width
(W.sub.3), and length (L.sub.3) of stress relief sections 112, 134,
respectively, are of dimensions such that they reduce the tensile
loading or stress exerted on break joint 138 while running downhole
safety joint 100 in and out of wellbore 74. Stress relief sections
112, 134 allow downhole safety joint 100 to bend or flex at the
upper and lower ends of downhole safety joint 100 under bending or
tensile loading such as when operated in deviated, horizontal, or
tortuous trajectories or wellbores.
[0048] Stress relief sections 112, 134 reduce the excessive stress
and strain on break joint 138, thus reducing the likelihood of
failure of break joint 138. Stress relief sections 112, 134 protect
the threads 118 and threads 132 of break joint 138 from being
"worked" by the bending stress experienced on downhole safety joint
100 in work string 70 as it is being run in and out of deviated
wellbores. When downhole safety joint 100 is forced into a forced
deflection or stress such as when running in and out of a deviated
wellbore, stress relief sections 112, 134 balance the stress
encountered by downhole safety joint 100 such that they flex an
amount substantially equal to the amount of stress that would cause
the weakest component of break joint 138 of downhole safety joint
100 to fail or become damaged over period of usage.
[0049] As shown in FIG. 3B, downhole safety joint 100 is shown
experiencing a side load ("SL") caused by a highly deviated,
horizontal, or tortuous trajectory in wellbore 74 to access
substantially horizontal hydrocarbon bearing formations, in one
example. SL causes a compressive stress ("CS") on one side, top, or
bottom of downhole safety joint 100 and a tensile stress ("TS") on
the other side, bottom, or top of downhole safety joint 100. The
flex or bend shown at the distal ends of downhole safety joint 100
is caused by connector 106 and connector 136 being disposed against
a substantially opposing side of wellbore 74 than that exerted by
SL at or near break joint 138. Due to stress relief sections 112,
134, downhole safety joint 100 bends or flexes more at, near, or
towards their distal ends, connector 106 and connector 136, than at
break joint 138, thus decreasing the cyclical loading at break
joint 138 at described herein caused by fully or in part the axial
loading ("AL") along the longitudal axis of downhole safety joint
100 caused by weighting/unweighting work string 70 during operation
of work string 70 and downhole safety joint 100.
[0050] Because of the reduced outer diameter of stress relief
sections 112, 134, downhole safety joint 100 flexes or bends more
readily at the end sections of downhole safety joint 100. This
preferable flexing or bending may preferably occur along the
section of downhole safety joint 100 from connector 106 to the
lower sections of stress relief section 112, in one embodiment.
Additionally, this preferable flexing or bending may preferably
occur along the section of downhole safety joint 100 from connector
136 to the upper section of stress relief section 134, in one
embodiment. While providing such flexing/bending sections of
downhole safety joint 100 alleviates the CS and TS on break joint
138 thus preventing undesirable loosening and/or tightening of
break joint 138.
[0051] Turning now to FIGS. 4-5, upper sub 102 and lower sub 104
are shown substantially coupled together. Downhole safety joint 100
has two different sealing areas and/or diameters that relieve
and/or release fluid as upper sub 102 is coupled together with
lower sub 104 in the presence of fluid under pressure. A first
sealing diameter exists substantially between seals 114 and the
portion of box end 130 above seal 123. As upper sub 102 and lower
sub 104 are coupled or screwed together fluid under pressure in
this first sealing diameter or area flow through a channel created
by gaps 140, 142 of all of threads 118 and threads 132, as best
shown in FIG. 5, and flows via flow channel 143 created by the gap,
similar to gaps 140, 142, between the bottom set of threads. In one
embodiment, threads 118 may have a width or pitch less than
standard width relative to the width or pitch of threads 132. In
another embodiment, threads 132 may have a width or pitch less than
standard relative to the width or pitch of threads 118.
[0052] Most if not all of fluid flowing in flow direction 143 flow
over seal 123 before it enters the space of the second sealing area
created between the diameter or area between tapered end 122 and
the sealing engagement of seal 123 and the inner surface of tubular
body 126. Fluid in this space then flows through one ore more
grooves 124 as shown by flow path 145. Fluid flowing through
grooves 124 then flows into passageway 128. By allowing fluid in
these spaces to vent or flow out the bottom of upper sub 102 via
grooves 124 into passageway 128, enables upper sub 102 and lower
sub 104 to be coupled or screwed together without having issues
relating to hydraulic locking.
[0053] Any of gaps 140, 142 may be formed by forming or removing a
portion of one or both sides of one or more threads 118 and/or
threads 132. In one aspect, D.sub.1 of gaps 140, 142 may be from
about 0.10 inch to about 0.01 inch. In one aspect, D.sub.1 of gaps
140, 142 may be from about 0.06 inch to about 0.02 inch. In yet
another aspect, D.sub.1 of gaps 140, 142 may be approximately 0.04
inch.
[0054] Grooves 124 are preferably formed in non-threaded section
120 and extend from just below seal 123 to tapered end 122 to
provide flow path 145 for fluid to enter passageway 128. Grooves
124 may be substantially longitudinal recesses. Upper sub 102 and
lower sub 104 may be a tubular or tubular member having a
substantially cylindrical body with a central passageway
therethrough. Stress relief sections 112, 134 may be
circumferential recessed portions formed in partially or fully the
entire circumference of the outer diameter of stress relief
sections 112, 134 by any means commonly known to those skilled in
the arts. Stress relief sections 112, 134 may extend partially or
fully the entire length (L.sub.2) and length (L.sub.3) of stress
relief sections 112, 134, respectively.
[0055] Tubulars and/or tubular members as herein discussed may mean
a term pertaining to any type of oilfield pipe, such as drill pipe,
drill collars, pup joint, casing, production tubing, coiled tubing,
mandrels, etc.
[0056] Seals 114, 123 may consist of any suitable sealing element
or elements, such as a single O-ring, a plurality of O-rings,
and/or a combination of backup rings, O-rings, and the like. In
various embodiments, Seals 114, 123 may comprise AFLAS.RTM.,
o-rings with PEEK back-ups for severe downhole environments, Viton
O-rings for low temperature service, Nitrile or Hydrogenated
Nitrile O-rings for high pressure and temperature service, or a
combination thereof.
[0057] While this invention has been described with reference to
illustrative embodiments, this description is not intended to be
construed in a limiting sense. Various modifications and
combinations of the illustrative embodiments as well as other
embodiments of the invention, will be apparent to persons skilled
in the art upon reference to the description. It is, therefore,
intended that the appended claims encompass any such modifications
or embodiments.
* * * * *