U.S. patent application number 09/749467 was filed with the patent office on 2002-07-04 for separation string for the separation of hydrocarbon from contaminants in a wellbore and method of assembling same.
Invention is credited to Hampton, John, Underdown, David.
Application Number | 20020084073 09/749467 |
Document ID | / |
Family ID | 25013867 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020084073 |
Kind Code |
A1 |
Underdown, David ; et
al. |
July 4, 2002 |
Separation string for the separation of hydrocarbon from
contaminants in a wellbore and method of assembling same
Abstract
A separation string includes an outer pre-drilled liner and an
inner assembly disposed within the outer pre-drilled liner. The
inner assembly includes a shear-out member and a filter assembly
for separating hydrocarbons from contaminants. A swivel slack joint
is connected to an upper end of the inner assembly to facilitate
mounting of a top sub to the inner assembly and to the outer
pre-drilled liner without producing rotation of the inner assembly.
The swivel slack joint includes an outer sleeve connected to the
inner assembly, and a tube connected to the top sub. The tube is
freely rotatable and vertically slidable relative to the sleeve.
The shear-out member is designed to shear at a load less than a
load which would cause other components of the inner assembly to
shear, and to present, upon shearing, a portion configured to be
grasped by a retrieval tool.
Inventors: |
Underdown, David; (Conroe,
TX) ; Hampton, John; (Houston, TX) |
Correspondence
Address: |
CHEVRON TEXACO CORPORATION
LAW DEPARTMENT-INTELLECTUAL PROPERTY UNIT
2613 CAMINO RAMON
SAN RAMON
CA
94583
US
|
Family ID: |
25013867 |
Appl. No.: |
09/749467 |
Filed: |
December 28, 2000 |
Current U.S.
Class: |
166/265 ;
166/227; 166/380 |
Current CPC
Class: |
E21B 17/07 20130101;
E21B 17/021 20130101; E21B 43/38 20130101 |
Class at
Publication: |
166/265 ;
166/380; 166/227 |
International
Class: |
E21B 043/38 |
Claims
What is claimed is:
1. A separation string for separating hydrocarbons from
contaminants in a wellbore, comprising: an outer pre-drilled liner
including bottom and top ends spaced apart along a vertical axis of
the casing; an inner assembly disposed inside of the pre-drilled
liner and comprising a filter assembly including at least one
membrane unit adapted to separate at least one hydrocarbon from at
least one contaminant; a top sub threadedly attached to the top end
of the outer pre-drilled liner; and a swivel slack joint
interconnecting the top sub and the inner assembly, the swivel
slack joint including first and second telescopingly arranged
elements, a bottom and of the first element attached to a top end
of the inner assembly, and a top end of the second element
threadedly attached to the top sub, the second element being
mounted to the first element for vertical sliding movement relative
thereto, and being rotatable relative to the first element about
the longitudinal axis, to permit the top sub to be screwed to the
outer pre-drilled liner without rotating the inner assembly.
2. The separation string according to claim 1 wherein the first
element of the swivel slack joint comprises a sleeve having a screw
thread at its bottom end; the second element comprising a tube
slidably mounted inside the sleeve and having a screw thread at its
top rear end.
3. The separation string according to claim 2 wherein the swivel
slack joint further includes an insert attached to a top end of the
sleeve and defining a shoulder for limiting rearward movement of
the tube relative to the sleeve.
4. The separation string according to claim 3 wherein the insert is
threadedly secured to the top end of the sleeve and further
attached thereto by set screws for preventing unscrewing of the
insert.
5. The separation string according to claim 3 wherein one of the
sleeve and the tube carries seals bearing against the other of the
sleeve and the tube.
6. The separation string according to claim 5 wherein the seals
comprise O-rings mounted on an outer periphery of a front portion
of the tube.
7. The separation string according to claim 1 wherein the inner
assembly further includes a shear-out member having a shearing
portion which shears at a predetermined load less than a load at
which other components of the inner assembly would shear, the
shear-out member including a portion which is exposed in response
to a shearing of the shearing portion and which is configured to be
grasped by a retrieval tool.
8. The separation string according to claim 1 wherein the membrane
unit comprises an outer pre-drilled tube, and a pair of end caps
screwed to opposite ends of the tube to retain a membrane inside of
the tube.
9. The separation string according to claim 8 wherein the membrane
unit further comprises an inner pre-drilled tube disposed inside of
the membrane.
10. The separation string according to claim 1 wherein the inner
assembly further includes a latch assembly for latching the inner
assembly to the outer pre-drilled liner.
11. A separation string for separating hydrocarbons from
contaminants in a wellbore, comprising: an outer pre-drilled liner
including bottom and top ends spaced apart along a vertical axis of
the pre-drilled liner; an inner assembly disposed inside of the
casing and comprising: a latch member for latching the inner
assembly to the outer pre-drilled liner casing; a filter assembly
comprising at least one membrane adapted to separate at least one
hydrocarbon from at least one contaminant, and a shear-out member
for shearing at a predetermined load less than a load which would
fracture the other components of the inner assembly and including a
portion which becomes exposed in response to a shearing of the
shear-out member and configured for being grasped by a retrieval
tool; and a swivel slack joint interconnecting the top sub and the
inner assembly, the swivel slack joint including first and second
telescopingly arranged elements, a bottom end of the first element
attached to a top end of the inner assembly, and a top end of the
second element threadedly attached to the top sub, the second
element being mounted to the first element for vertical sliding
movement relative thereto, and being rotatable relative to the
first element about the longitudinal axis, to permit the top sub to
be screwed to the outer casing without rotating the inner
assembly.
12. A method of assembling a separation string, the separation
string including an outer pre-drilled liner and an inner assembly
disposed within the outer pre-drilled liner, the pre-drilled liner
including bottom and top ends spaced apart along a longitudinal
axis of the pre-drilled liner, the inner assembly comprising a
filter assembly including at least one membrane unit for separating
at least one hydrocarbon from at least one contaminant, the method
comprising the steps of: A. providing a swivel slack joint in the
casing at a top end of the inner assembly, the swivel slack joint
including first and second telescopingly arranged elements, the
second element being slidable relative to the first element along
the vertical axis, and rotatable relative to the first element
about that axis; B. attaching a bottom end of the first element to
a top end of the inner assembly; C. screwing a top sub to a top end
of the second element; and D. screwing the top sub to a top end of
the outer pre-drilled liner while causing the first sub to rotate
the second element relative to both the first element and the inner
assembly about the longitudinal axis, to prevent rotation of the
inner assembly.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a separation string for the
separation of contaminants from hydrocarbons in a wellbore and to a
method of assembling such a separation string.
BACKGROUND OF THE INVENTION AND BRIEF DESCRIPTION OF THE RELATED
ART
[0002] Hydrocarbon gases and liquids have been recovered from
underground wellbores for over a hundred years. The recovery
technology generally involves drilling a wellbore into a
hydrocarbon gas or liquid formation and withdrawing the materials
under reservoir pressure or by artificial lifting.
[0003] The current recovery technology involves removing, from the
wellbore, the hydrocarbon together with any contaminants which are
present, and then separating the contaminants from the hydrocarbon
above ground. This above ground separation is costly. Disposal of
the removed contaminants may also present environmental problems.
The contaminants which may be produced include gases, such as
carbon dioxide, nitrogen, water vapor, hydrogen sulfide, helium,
and other trace gases, and liquids such as water, and others.
[0004] The contaminants which are brought to the surface and
separated from the hydrocarbon must be released to the atmosphere
or otherwise disposed of, adding expense to the process. Due to
environmental concerns about the release of greenhouse gases, many
countries are placing greater limitations on emission of byproduct
gases to the atmosphere. For example, some countries now assess a
tax on carbon dioxide emissions. Other contaminants are highly
corrosive or poisonous and require special handling. For example,
hydrogen sulfide must be reacted and converted to molten sulfur
before disposal.
[0005] Accordingly, it would be highly desirable to maintain some
or all of the contaminant materials within the wellbore and/or
selectively separate the contaminants in the wellbore for
reinjection, removal, or other processing.
[0006] Membrane technology has been developed which allows the
selective passage of materials. This technology has heretofore been
used as an above ground, technology for separating hydrocarbons
from contaminants after recovery. Although its use in a downhole
situation has been proposed, that technology has not actually been
used downhole, despite the obvious economic and environmental
benefits that could be achieved therefrom. Furthermore, in offshore
applications, downhole separation would reduce the amount of heavy
and space-consuming equipment present on the offshore deck.
[0007] It has previously been proposed to suspend membrane-carrying
tubing in a wellbore for separating hydrocarbon from contaminants
(e.g., see U.S. Pat. No. 6,015,011). However, such tubing is
lengthy and quite flexible, making it both difficult to control and
susceptible to damage while being inserted into a wellbore. In that
regard, the membrane filters can be quite brittle and susceptible
to breakage in response to the string impacting against the side of
the wellbore. Also, due to the manner in which membranes function,
even the smallest break or tear can have a significant adverse
effect on the performance of the membrane. Moreover, it would be
difficult and costly to make such a string having interconnecting
thread joints that are rugged enough to withstand the weight and
torquing of the string.
[0008] Thus, it would be desirable to provide an apparatus and
method for downhole separation and selective recovery to maximize
the production of a desired hydrocarbon while minimizing the
production of contaminants, utilizing membrane technology.
[0009] It would also be desirable to provide a separation structure
which is economical to produce and assemble, as well as being
easier to control and less susceptible to damage.
SUMMARY OF THE INVENTION
[0010] One aspect of the present invention involves a separation
string for separating hydrocarbons from contaminants in a wellbore.
The separation string includes an outer housing, i.e., pre-drilled
liner including bottom and top ends spaced apart along a vertical
axis of the pre-drilled liner, and an inner assembly disposed
inside of the pre-drilled liner. The inner assembly comprises a
filter assembly which includes at least one membrane unit adapted
to separate at least one hydrocarbon from at least one contaminant.
A top sub is threadedly attached to a top end of the outer
pre-drilled liner. A swivel slack joint interconnects the top sub
and the inner assembly. The swivel slack joint includes first and
second telescopingly arranged elements. A bottom end of the first
element is attached to a top end of the inner assembly, and a rear
end of the second element is threadedly attached to the top sub.
The second element is mounted to the first element for vertical
sliding movement relative thereto, and being rotatable relative to
the first element about a longitudinal axis of the outer
pre-drilled liner, to permit the top sub to be screwed to the outer
pre-drilled liner without rotating the inner assembly.
[0011] The invention also relates to the method of coupling the
pre-drilled liner and the inner assembly to the top sub. The method
includes attaching the bottom end of the first element to the top
end of the inner assembly. Then, the top sub is screwed to the top
end of the second element. Thereafter, the top sub is screwed to
the rear end of the outer pre-drilled liner while causing the top
sub to rotate the second element relative to both the first element
and the inner assembly about the longitudinal axis, to prevent
rotation of the inner assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The objects and advantages of the invention will become
apparent from the following detailed description of a preferred
embodiment thereof in connection with the accompanying drawings in
which like numerals designate like elements and in which:
[0013] FIG. 1 is a vertical sectional view taken through an inner
assembly of a separation string according to the present
invention;
[0014] FIG. 2 is a view similar to FIG. 1 showing the inner
assembly being lowered into an outer pre-drilled liner of the
separation string;
[0015] FIG. 3 is a view similar to FIG. 2 after a latch-in seal
mechanism of the inner assembly has been latched to the bottom of
the outer pre-drilled liner;
[0016] FIG. 4 is a view similar to FIG. 3 after the inner assembly
has been raised to confirm that latching has occurred;
[0017] FIG. 4A is a fragmentary view of FIG. 4 showing a tubing
string being fitted with a top sub;
[0018] FIG. 4B is a view similar to FIG. 4A showing the top sub
being screwed onto a pup joint;
[0019] FIG. 4C is a view similar to FIG. 4B showing the top sub
being screwed onto the outer pre-drilled liner FIG. 5 is a view
similar to FIG. 4 after the top sub has been attached to the outer
pre-drilled liner;
[0020] FIG. 6A is a vertical sectional view taken through a swivel
slack joint according to the present invention, with a tube element
of the joint in an extended state;
[0021] FIG. 6B is a view similar to FIG. 3 with the tube element in
a retracted state;
[0022] FIG. 7A is a vertical sectional view taken through a
shear-out member prior to shearing;
[0023] FIG. 7B is a view similar to FIG. 7A with the shear-out
member in a sheared state;
[0024] FIG. 8 is a vertical sectional view taken through a membrane
unit;
[0025] FIG. 9 is a vertical sectional view taken through a prior
art latch-in seal mechanism; and
[0026] FIG. 10 is a fragmentary view of FIG. 9.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0027] A fully assembled separation string 10 depicted in FIG. 5
includes an outer pre-drilled liner or outer assembly 12, and an
inner assembly 11 disposed inside of the pre-drilled liner. The
outer pre-drilled liner 12 has lower and upper ends spaced apart
along a vertical axis of the pre-drilled liner. The separation
system is comprised of a cylindrical pre-drilled liner 14, a
cylindrical latch-in seal housing 16 screwed onto the bottom of the
liner 14, and a cylindrical bottom sub 18 screwed onto the bottom
of the latch-in seal housing 1 6.
[0028] The inner assembly 11, also shown in FIG. 1, includes a
conventional anchor latch-in seal mechanism 28 for latching into
the latch-in seal housing 16 (see also FIGS. 9-10), and a shear-out
safety joint 30 screwed into the top end of the latch-in seal
mechanism 28. That shear-out safety joint includes first and second
sections 30A, 30B (see FIGS. 7A, 7B). Section 30A telescopes within
section 30B and is held therein by shear pins 30C. O-ring seals 30D
are mounted on the outer periphery of the first section 30A. The
first and second sections 30A, 30B include internal and external
screw threads 30E, 30F, respectively. The screw thread 30F screws
onto the latch-in seal mechanism 28. The shear pins 30C are
designed to shear at a predetermined load which is lower than that
at which other elements of separation string (including membranes
as will be explained) will break. Upon shearing of the shear pins,
as shown in FIG. 7B, a portion 30G of the second section 30B
becomes exposed, which is configured to be readily grasped by a
conventional retrieval tool.
[0029] Thus, in the event that the separation string, while being
raised, encounters a resistance to travel, e.g., as caused by a
sharp curvature in the wellbore, for example, it is assured that
the separation string will shear at a location making it readily
possible to retrieve the part of the separation string remaining in
the wellbore.
[0030] A filter assembly is screwed into the top end of the
shear-out safety joint 30 (see also FIG. 8). That filter assembly
could comprise various types of filter devices, but preferably
comprises one or more hollow tube membrane units 32 of the type
described in U.S. Ser. No. 09/640,623, filed Aug. 17, 2000, the
disclosure of which is incorporated by reference herein. Each
membrane unit 32 (see FIG. 8) includes a pre-drilled tube 32B and
bottom and top end caps 32C, 32D, each end cap having screw threads
at both ends. Thus, the bottom end cap 32C has an external screw
thread 32E at a bottom end thereof, and an internal screw thread
32F at a top end thereof. The screw thread 32E is to be screwed to
another internal element of the separation string, e.g. to another
membrane unit, or to the top section 30A of a shear-out safety
joint for example. The screw thread 32F attaches to an external
screw thread of the pre-drilled tube 32B. The top end cap 32D
includes an internal screw thread 32G and an internal screw thread
32H. The screw thread 32G screws into an adjacent internal element
of the separation string, such as another membrane unit. The screw
thread 32H is secured to the pre-drilled tube 32B. At least one
cylindrical membrane 321 is disposed within the pre-drilled tube
32B, and an inner perforated tube 32J is positioned inside of the
membrane 32I. Thus, the membrane 32I is protected and reinforced on
its inner and outer sides.
[0031] The membranes 32I function to separate one or more
hydrocarbons from one or more contaminant. Some contaminants which
may be removed are gases including carbon dioxide, nitrogen, water
vapor, hydrogen sulfide, helium, and other trace gases, and liquids
including water, heavy hydrocarbons, and other liquids. The
hydrocarbon from which the contaminants are separated may be oil,
methane, ethane, propane, or others.
[0032] Screwed into the top of the filter assembly 32 is a swivel
slack joint 36 which facilitates assembly of the unit 10, as will
be explained. The swivel slack joint 36, best shown in FIGS. 6A and
6B, includes two telescopingly arranged elements, i.e., an outer
sleeve 50, and an inner or upper tube 52 which is slidable up and
down within the sleeve 50. The sleeve includes an internal screw
thread 54 at its lower end and an internal screw thread 56 at its
upper end. Threadedly secured to the upper thread 56 is an insert
58 which forms a downwardly facing radial stop shoulder 60 at its
lower end. Set screws 62 are screwed radially through an upper end
of the sleeve and against the insert 58 to prevent unscrewing of
the insert 58.
[0033] The lower end of the inner tube 52 includes a radially
enlarged portion 64 which carries seals in the form of O-rings 66
that engage an inner surface of the sleeve 50. The inner tube 52 is
freely rotatable relative to the sleeve 50 about a longitudinal
axis A of the pre-drilled liner, and is slidable vertically within
the sleeve 50 between the shoulder 60 and an upwardly facing ledge
68 formed by the sleeve 50. An upper end of the tube 52 includes an
external screw thread 69 adapted to be attached to a top sub
70.
[0034] The conventional latch-in seal mechanism 28, depicted in
FIGS. 9 and 10, includes first and second segments 80, 82 screwed
together. The top segment 80 is threadedly secured to the shear-out
safety joint 30. The second segment 82 carries external teeth 86
that are engageable with corresponding teeth 88 formed on an inner
bore of the latch-in seal housing 16 in response to downward
movement of the first segment 80 within the latch-in seal housing
16.
[0035] In practice, the separation string 10 can be assembled while
suspended in a wellbore B. The pre-drilled assembly 14, 16, 18,
having already been formed, is suspended in the wellbore B by a
gripping mechanism G, as shown in FIG. 2. The anchor latch-in seal
mechanism 28 is inserted, and then the shear-out safety joint 30 is
screwed into the anchor latch-in seal mechanism 28. The tubular
membrane units 32 of the filter assembly are screwed together, with
the lowest membrane unit being screwed into the top of the
shear-out safety joint 30. In practice, there will likely be many
membrane units provided, and a number of shear-out safety joints
30.
[0036] A top sub is to be attached to upper ends of both the outer
assembly and the inner assembly. Ideally, that should be done
without rotating the inner assembly relative to the outer assembly,
because such rotation could overtorque and damage the internal
components, and/or tear the various seals. The function of the
swivel slack joint 36 is to enable such rotation of the inner
assembly to be avoided.
[0037] The lower end of the sleeve 50 of the swivel slack joint is
next screwed onto the top of a pup joint 71, the lower end of which
is secured to the filter assembly. Then, with the tube 52 in its
upwardly slid state shown in FIGS. 1, 2 and 6A, a pup joint 73 is
screwed into engagement with the upper end of the tube 52 (see FIG.
2). The pup-joint 73 and the inner assembly are lowered into the
pre-drilled liner on a tubing string 72 until the anchor latch-in
mechanism 28 lands on a locating shoulder 88 formed in the latch-in
seal housing 16. A small amount of tension is then applied by the
tubing string 72 to the inner assembly by lifting the tubing string
(see FIG. 4), to give a positive indication that the anchor
latch-in mechanism 28 is properly latched into the latch-in seal
housing 16. At this point, the upper tube 52 of the swivel slack
joint is fully extended (as shown in FIGS. 4 and 6A), and the upper
facing ledge 68 of the upper tube 52 is supporting the downward
facing shoulder 60 of insert 58. The tubing string 72 is then
separated from the pup joint 73 and the top sub 70 is attached to
the tubing string (see FIG. 4A). The tubing string 72 is then
lowered to position the top sub on the upper end of the upper tube
52. By then rotating the tubing string 72, and thus the top sub 70,
the top sub becomes screwed onto the pup joint 73 (see FIG. 4B).
Then, the tubing string 72 is lowered, and the fully extended upper
tube 52 of the swivel slack joint starts to slide toward the bottom
of the sleeve 50 of the swivel slack joint. At some point before
the bottom of the tube 52 reaches the ledge 68 of the sleeve 50,
the outer threads 70A of the bottom of the top sub 70 will engage
the inner threaded portion of the pre-drilled liner 14. Further
rotation of the tubing string 72 and the top sub 70 causes the top
sub to be screwed onto the pre-drilled 14. As this occurs, the tube
52 is rotated by the top sub. However, since the tube 52 can rotate
relative to the sleeve 50 about a longitudinal axis of the casing,
the inner assembly 28, 30, 32 is not rotated, so no damage occurs
to the inner assembly. Relative longitudinal movement between the
inner and outer assemblies is accommodated by the ability of the
tube 52 to retract downwardly within the sleeve 50.
[0038] After the top sub 70 has been fully screwed down, the
separation string 10 appears as shown in FIG. 1 and can be lowered
within the wellbore, to enable the bottom sub 18 to be connected to
any suitable downhole element, such as a packer for example.
[0039] If desired, one or more conventional pack-off (seal)
assemblies could be provided as part of the separation string, to
bear against an inner surface of the casing, in order to stabilize
the separation string within the pre-drilled.
[0040] The filter membrane 321 is protected on its inner and outer
sides by pre-drilled structures 32B and 32J and thus is less likely
to fracture or otherwise be damaged while being run into and out of
the wellbore.
[0041] The membrane units of the filter assembly have a tubular
configuration and form part of an open central passageway of the
separation string. This tubular configuration allows conventional
oil field tools to be run through the separation string. The
ability to run tools through the separation string provides the
advantage that the separation string does not have to be removed
for many well work processes to be performed. For example, gas lift
valves, setting and pulling tools, impression blocks, chemical
injection valves, tubing stops, packers, tubing plugs, memory logs,
production logs, dump bailers, perforation guns, or the like can be
run through the separation string.
[0042] The operation of the present invention has been described
with respect to a vertical well, however, it should be understood
that the invention may be employed in horizontal wells and other
non-vertical wells.
[0043] During a production operation, the hydrocarbon and
contaminants enter the wellbore and pass upward through the central
passageway of the separation string. As the hydrocarbon passes
through the filter assembly 32, one or more contaminants permeate
out through the membrane units and enter a surrounding containment
collection zone. The hydrocarbon, plus any remaining contaminants
that were not removed, continue out the top of the separation
string. The hydrocarbon with reduced contaminants is passed to the
surface or to another separation system. The contaminants which
have been collected in the collection zone may be disposed of by
directing the contaminants to an underground disposal formation.
Alternatively, the contaminants may be removed from the collection
zone to the surface.
[0044] It will be apparent that the swivel slack joint 36 of the
present invention permits a top sub to be screwed onto an inner
assembly which include membrane filters without producing rotation
of the inner assembly, and thereby minimizes chances that the inner
assembly will be damaged during attachment of the top sub.
[0045] Although the present invention has been described in
connection with preferred embodiments thereof, it will be
appreciated by those skilled in the art that additions, deletions,
modifications, and substitutions not specifically described may be
made without departing from the spirit and scope of the invention
as defined in the appended claims.
* * * * *