Note: Descriptions are shown in the official language in which they were submitted.
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- INJECTION MANDREL
BACKGROUND OF THE INVENTION
The invention relates generally to subsurface well
treating apparatus and operations. In particular, the invention
relates to an injectlon mandrel and method for circulating well
treating fluids into subsurface wells to treat produced fluids
from subsurface earth formations.
In order to complete oil and gas wells, subsurface
earth formations are perforated to bring the wells into
production. The fluids produced may subject the subsurface and
surface equipment to corrosion from a variety of chemical agents
present in the fluids~ To combat this corrosion, a number of
`~ 15 well-known corrosion inhibitors may be circulated through the
wellbore to reduce or prevent the undesirable effects of the
corrosive agents.
Produced fluids also may contain salts and other
dissolved and undissolved solids which can precipitate and
deposit on the surface of the production tubing or in the
perforations in the subsurface earth formation. As deposits
build, production flow becomes restricted. To combat this
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problem, one or more of a number of well-known solvents may be
circulated~through the well to dissolve any flow restricting
deposits and to prevent deposits from recurring. `
Apparatus and methods are known to circulate such
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treatiDg fluids through wells at various depths in the wells.
Side-pocket mandrels may be utilized for this purpose. A
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treating fluid is injected into the annulus of a well above a
packer assembly, through ports in the side-pocket of the
mandrel, through a chemical injection valve set in the
side-pocket, and into contact with the produced fluids flowing
out of the well. Once the fluids have been treated, they flow
through the mandrel and production tubing to the surface for
recovery.
Side-pocket mandrels suffer from several shortcomings
when used for the above purpose. First, side-pocket mandrels
require complicated kickover tools to set and retrieve chemical
injection valves in their side valve pocket. Current kickover
tools require involved wireline operations which are typically
not practical at depths below about 15,000 feet. Second, the
construction of a side-pocket mandrel does not permit
`~ 15 circulation of the treating fluid below the packer assembly
because the mandrel does not extend below the packer. Third,
side-pocket mandrels allow untreated, often corrosive, produced
fluids into the upper annulus of the well above the packer
assembly when the chemical injection valve is not in place. In
the annulus, such produced fluids could damage the tubing,
casing and other equipment, such as a subsurface safety valve.
Other designs have also been proposed, but these
designs suffer from the same or other shortcomings. The other
shortcomings include limitations on the ability to circulate
treating fluids at any desired depth in a well, limitations on
conduc.lng periorating, logging or other oper6tion6 without
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having to pull the mandrel from the well, and limitaticns on
flow through the mandrel, which may cause pressure losses and
erosion problems.
Ideally, an apparatus for treating produced fluids in a
wellbore will have the following characteristics. The annulus,
the space between the production tubing and the casing, above
the packer should be effectively isolated from produced fluids.
The apparatus should be capable of circulating treating fluids
across the perforations or at any other preselected depth. The
apparatus should be capable of being routinely set and operated
at total depths in excess of 15,000 ft. There should be a
capability for conducting workover operations through the
apparatus. Restrictions to flow should be minimized.
SUMMARY OF THE INVENTION
The present invention is a mandrel and method for
` circulating a treating fluid in a well. Preferably, the mandrel
is a center-pocket mandrel.
The injection mandrel preferably comprises a body
having a longitudinal flow conduit therethrough, a valve pocket
in the body substantially axially aligned with the bore of the
well and the production tubing and adapted to receive a
removable chemical injection valve, a check valve mounted on the
body, and a conduit for permitting fluid communication between
the check valve and ~he chemical injection valve. The body is
adapted to be attached to a production tubing string. It may be
put in the well through and engaging a packer assembly.
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With a chemical injection valve set in the valve
pocket, treating fluid is injected into the annulus of the well
above the packer assembly. This treating fluid flows from the
annulus, through the check valve into the va]ve pocket, through
the chemical injection valve and into contact with the formation
fluid from the lower interval of the well. The treated
formation fluid flows upwardly through the mandrel and the
tubing string to the surface for recovery. The check valve
- prevents formation fluids from entering the annulus.
The chemical injection valve may be removed using
standard wireline tools and workover operations can be conducted
through the valve pocket, since it is substantially aligned with
the well tubing bore.
In order to inject treating fluids at any preselected
depth below the mandrel~ a dip tube may be connected to the
lower end of the injection valve housing. Treating fluids from
the annulus may then be pumped through the dip tube to the
desired depth for injection into the formation fluids.
The present invention allows chemical injection valves
to be routinely set and retrieved at depths much greater than
15,000 feet and precludes entry of the untreated producing
fluids into the upper annulus above the packer assembly.
Treating fluids may be circulated in the well at any desired
depth, and allows a variety of workover and loggin& tools to be
run through the apparatus when the chemical injection valve is
removed, so that other downhole operations may be conducted
without removing the tubing from the well.
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Embodiments of the inventlon will now be described with reference to
the accompanying drawings, wherein:
Figs. 1, lA and lB are schematic elevational views of a first
embodiment of an injection mandrel embodying the present invention.
Fig. 2 is a longitudinal section of the first embodiment of the
injection mandrel embodying the present invention.
Fig. 3 is a longitudinal section of the first embodiment of the
injection mandrel embodying the present invention, includlng a dip tube.
Fig. 4 is a detailed longitudinal section of a second embodiment of
an injection mandrel embodying the present invention; Fig. 4A illustrates the
upper hal~ of an injection mandrel; and, Figure 4B illustrates the lower half
of the same injection mandrel.
Fig. 5 is a horizontal section of the second embodiment of the
injection mandrel taking along line 5-5 of Fig. 4B.
Fig. 6 is a horizontal sectlonal view of the first embodiment of the
injection mandrel taken along line 6-6 of Figs. 2 and 3.
Fig, 7 is a horizontal sectional view of the first embodiment of the
injection mandrel taken along line 7-7 of Fig. 2,
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DETAILED DESCRIPTION
Referring now to the drawings in more detail,
particularly to Figs. 1, lA and lB, there is illustrated a
schematic elevational view of an injection mandrel in accordance
with the present invention. Preferably, the mandrel is a center
pocket mandrel. A well 10 is shown in which a casing 11 has
been cemented, indicated at 12, and perforated in a producing
sone 13. At the surface a Christmas tree 14 is mounted on a
wellhead 15 on top of the casing 11. A tubing string 20 is
suspended from the wellhead 15. A valved conduit 21 is
connected to the upper end of the tubing string 20 and a second
valved conduit 22 is connected into the wellhead 15 to
communicate with the annulus between the inside of the casing
and the outside of the tubing string. A center pocket mandrel,
24a in Fig. lA and 24b in Fig. lB, is connected to the tubing
string 20. A packer assembly 26 seals off and divides the
well 10 into an annulus 14 between the casing ll and the tubing
string 20 (and between the casing ll and center pocket
mandrels 24a and 24b) and a lower interval 23 below the packer
assembly 26.
Fluids from the producing zone 13 may contain corrosive
agents such~as hydrogeD sulfide, carbon dioxide or water which
can damagq the casing string 11, tubing 20 and other subsurface
` 25 and surEace equipment. To combat this corrosion problem, a
suitable corrosion inhibitor may be injected into the well.
Sui tble corrosion inhibitors are vel: know~ in the ~rt.
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The fluids from the producing zone 13 may also contain
salts or other dissolved and undissolved solids which can
precipitate and deposit in the perforations or tubing string 20,
reducing production. To combat this problem, a suitable solvent
may be injected into the well to dissolve the deposits. Such
solvents are also well known in the art.
As illustrated in Figs. lA and lB, the center pocket
mandrels 24a and 24b are provided for these and for other
operations in which;it is desired to circulate a treating fluid
from the annulus 14 of the well 10 into contact with the
formation fluid in the lower interval 23. The present invention
is, therefore, not limited in scope solely to the use of
corrosion inhibitors or solvents.
Referring to Figs. 1 and lA, a suitable treating fluid
is pumped through the valved conduit 22 and injected into the
annulus 14. From the annulus 14, the treating fluid enters the
center pocket mandrel 24a through a check valve, described
hereinaEter, flows into the valve pocket in the valve housing of
the center pocket mandrel 24a and into the bore of the mandrel
to contact the formation fluids from lower interval 23. The
treated formation fluld is circulated upward through the flow
conduit 25 and to the tubing string 20 and the surface for
recovery through the valved conduit 21.
If it is desired to treat formation fluids at a depth
below the packer assembly 26, for example at the depth of
producing zone 13, the modified center pocket mandrel 24b of
Fi~. IB may b- u.ilized. The Elow of tre=tin~ Eluid is tùe eame
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as described above1with the following exception. A dip tube 25
is connected to the valve pocket. The dip tube extends below
the mandrel into the producing zone 13.
Specific embodiments of injection mandrels in
accordance with the present invention are show~ in greater
detail in Figs. 2-7. It should be noted that the embodiments
comprise many common elements, some identical in construction
and others similar but modified for the specific embodiment.
The identical elements of the various specific embodiments have
common numbering throughout this detailed discussion. The
similar but non-identical elements will also have common
numbering including a letter identifier for the particular
embodiment.
Referring to Fig. 2, there is illustrated in detail a
center pocket mandrel in accordance with the invention and
corresponding to the embodiment depicted in Fig. lA. The center
pocket mandrel 30 comprises a tubular body 32, an exterior check
valve 34, a conduit 36 for fluid communication between the check
valve 34 and a valve housing 33 defining a valve pocket 38 in
the body 32. A removable chemical injection valve 40 is set in
the valve pocket 38 for permitting fluid communication from the
valve pocket 38 into the formation fluid. The lower end of the
chemical injection valve is preferably recessed in, or enclosed
by, the valve housing to create a dead space to thereby reduce
wear and corrosion of the injection valve by the produced fluids
flowing upwardly through the mandrel. A longitudinal flow
conduit 42 through the mandrel body 32 transmits treated
formation fluid through the mandrel 30 and tubing string 20
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(Fig. lA) Eor collection at the surface. The flow conduit 42 is
defined by the inner surface of the body 32 and the outer
surface of the valve housing 33 that is attached to the ;nner
surface of the mandrel body 32.
The body 32 has threaded ends 44, 94 for connection to
the tubing string 20, a lower section 46 for the chemical
injection valve 40, and a tapered upper section 48 between the
lower section 46 of the body and the upper threadéd end 44. The
tapered upper section of the body reduces turbulence in the
produced fluid flow to minimize wear on the mandrel at this
point.
A mounting lug 58 having a slanted upper surface 60 is
connected to the inside surface of the body 32 and the exterior
of the valve housing 33, with the slanted upper surface 60 above
the top of the valve housing 33. The lug 58 provides additional
support for the valve housing 33 and the slanted upper
surface 60 directs chemical injection valves 40 (or downhole
tools) into or through the valve pocket 38. The valve
housing 33 has an inwardly beveled upper edge 62 for the same
purpose.
The treating fluid conduit 36 is moun~ed to the
exterior wall of the lower body section 46. The conduit 36
comprises a flow passage from the check valve 34, through a
fluid port 66 through the mandrel body, and into,the valve
pocket 38.; Referring to Figs. 2 and 7, it can be seen that the
conduit 36 may comprise a tube welded or otherwise mounted to
the exterior wall of the lower body section 46 on the side
adjacent the valve housing 33.
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The check valve 34 allows fluid to flow from the
amlulus 14 of the well 10 through the conduit 36 and into the
valve pocket 38, but precludes fluid flow in the opposite
direction. The check valve 34 may be any of the well known
one-way or check valves commonly used in injection operations.
The preferred choice is a unit consisting of two ball and seat
check valves in series. Ball and seat valves will allow fluid
flow when the pressure in annulus 14 rises to a preselected
value in excess of the fluid pressure in the valve pocket 38.
Spring loaded check valves may also be used. Such one-way
valves and valve arrangements are well-known to those skilled in
the art. The set point of the check valve will need to be
selected so that the check valve will permit flow into the
mandrel when there is a preselected differential pressure
between the fluid in the annulus and the fluid in the mandrel.
The check valve 34 is connected to one end of the
conduit on the exterior wall of the lower body section 46 at a
point below the fluid port 66. Alternatively, at least a part
of the conduit should be below the port 66. These arrangements
will form a gas trap in the conduit 36, preventing produced
fluids, such as corrosive gases, from entering the conduit and
minimizing the chances of damage to the check valve 34.
Once the treating fluid has entered the valve
pocket 38, it flows through ports 70 into a longitudinal bore 68
in the chemical injection valve 40. The longitudinal bore 68
houses one or more one-way or check valves 72 which allow the
treating fluid to flow through an opening 73 in the end of the
chemical injection valve 40 and into contact with the formation
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fluids. The check valves 72 may be of any of the types cor~nonly
used in injection operations and fam;liar to those skilled in
the art. The preferred choice is again a ball and seat
arrangement which may be used singly or in series plurality.
The injection valve 40 is inserted and removed from the
valve housing 33 by standard wireline operations. The injection
valve 40 is provided with a fishing neck 74 for attachment to a
wireline and a locking assembly 76 which is used to secure
chemical injection valve 40 in place in the valve housing 33.
10 The fishing neck 74 and locking assembly 76 may be any one of
the number of well known arrangements familiar to those skilled
in the art. The locking assembty 76 is provided with dogs 78
which, when inserted into inner tube 52, rest on shoulders 80
thereof to secure the valve 40 in place in the valve housing 33.
Above and below ports 70, the chemical injection
valve 40 is provided with fluid seals 82, which may comprise any
of the number of well known fluid seals such as, for example,
chevron seals or o-rings. As the chemical injection valve 40 is
inserted into the valve pocket 38, fluid seals 82 contact
20 shoulders 84 on the interior wall of the valve housing to form a
fluid seal. This seal insures treating fluid will flow through
the ports 70 and out of the chemical injection valve 40.
Deflector lugs 92 are provided on the e~terior wall of
lower body section 46 aligned with the check valve 34 to prevent
25 the valve from contacting the casing 11 or any obstructions in
the well 10 when the injection mandrel is run into the well.
Similar deflector surfaces 93 are provided adjacent the upper
and lower ends of the conduit.
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The end of the lower hody 46 has threads 94 for
engaging a packer assembly 26 or for connection to tubing or
other downhole tools (not shown) which may be attached to the
center pocket mandrel 30.
Referring now to Fig. 1, lA and 2, in the operation of
the apparatus of Fig. 2, the center pocket mandrel 30 is
inserted into a well 10 connected to the end of tubing string 20
and engaging the packer assembly 26. The check valve 34 is
positioned above the packer assembly 26.
The chemical injection valve 40 may be in place when
the mandrel is run into the well 10. Alternatively a wireline
(not shown) may be attached to the fishing neck 74 and the
chemical injection valve 40 lowered into the well through the
tubing string 20.
The chemical injection valve 40 is then set in the
valve housing using standard wireline methods. The chemical
injection valve 40 is preferably constructed so that when
dogs 78 are seated, the injection valve ports 70 will be
adjacent the treating fluid port 66. Once the chemical
injection valve 40 is in place and secured within the valve
pocket 38, the wireline is removed in the usual manner.
The desired treating fluid is then introduced into the
annulus 14 of the well. The fluid pressure in the annulus may
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then be increased until it is at the,preselected value in excess
of the Eluid pressure in the valve pocket 38. The treating
fluid from the annulus then flows through the check valve 34,
the conduit 36 and the fluid port 66 into the valve pocket 38.
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As the fluid pressure rises above the ~luid pressure in
the lower interval 23, the treating flu;d in the valve pocket
flows through the ports 70, the longitudinal bore 68 and the
check valves 72 of the chemical injection valve 40 and into
contact with the formation fluid. The check valves 72 in the
chemical injection valve 40 prevent flow in the opposite
direction.
Formation fluid from lower interval enters the center
pocket mandrel 30 through the end 96 of the lower body 46 and
contacts the treating fluid exiting the chemical injection
valve 40. The treated formation fluid then flows upwardly
through flow conduit 42 and the tubing string 20 to the surface
for recovery.
A modification of the center pocket mandrel described
above is illustrated in Fig. 3 and corresponds to the embodiment
depicted in Fig. lB. The center pocket mandrel 30a illustrated
in Fig. 3 and the center pocket mandrel 30 illustrated in Fig. 2
are nearly identical in construction. The difference is the
construction of the valve housings 38a. The operation of the
center pocket mandrels 30a and 30 is also nearly identical. The
following discussion will cover the differences between the two
embodiments, and reference may be had to the prior discussion of
the center pocket mandrel for other details.
Referring to Fig. 3, the valve housing 33a is connected
to dip tube 98 by threads, welding or any suitable means. The
; dip tube 98 is threaded 100 for connection to additional joints
of dip tubing to extend the dip tube 98 to any preselected
depth. This allows treating fluid to be injected directly into
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the lower intervat 14 at any point below the packer assernbly 26
(Fig. lB~ such as at the depth of the perforations in the
producing zone 13.
The treated formation fluid enters the flow conduit 42a
of center pocket mandrel 30a through the opening 96 at the base
of the lower body 46. Upon entering center pocket mandrel 30a,
this fluid flows upwardly through flow conduit ~2 and tubing
string 20 to the surface for recovery.
A second embodiment of a center pocket mandrel in
accordance with the present invention is illustrated in Fig. 4.
This embodiment is useful in operations where the diameter of
the casing 11 (Fig. lA) is such that a center pocket mandrel
with a smaller outside diameter should be used.
The center pocket mandrel 30b in Fig. 4 and 7, and the
center pocket mandrel in Figs. 2 and 6 are nearly identical in
construction except for the placement of their conduits 36
and 36b. The operation of the center pocket mandrels 30b and 30
is also essentially identical. The discussion below will
therefore relate only the differences between the two
embodiments, and reference may be had to the prior discussion
for other construction and operation details.
The mandrel of this embodiment requires a special lower
body section 46b. The lower body section is preferably attached
to the mandrel housing 46 by welding 47. A port 49 is machined
through the lower body to connect the conduit 36 and a check
valve manlfold 51. The manifold is threaded or otherwise
adapted to accept a check valve 34.
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Referring to Fig. ~, conduit 3~b is mounted inside the
lower body section ~6 between the outer surface of the valve
housing 33 of the inside surface of the body ~6. The check
valve 34 is in fluid communication with the conduit and is
5 mounted on the outer surface of the mandrel body 46. Referring
to Figs. 4 and 5, the conduit 36b extends through the flow
conduit 42b and into the valve pocket 38 through the fluid
port 66b. The rest of the details of this embodiment are the
same as in the embodiment described above. By routing the
10 treating fluid conduit through the inside of the mandrel, a
smaller diameter mandrel is possible.
; The mandrels of the present invention provide effective
tools for injecting treating fluids into wells to treat fluids
from producing formations. The ability to insert and remove
5 chemical injection valves by standard wireline procedures allows
the center pocket mandrel to be set at depths where side-pocket
and other mandrels could not practically be used. ~se of a dip
tube allows the center pocket mandrel to be set at a selected
depth while permitting injection of treating fluid into the well
20 at any depth below the center pocket mandrel.
The exterior check valve (and the chemical injection
valve)~prevent formation fluid from entering the annulus of the
well above the packer assembly. This is important to maintain
the integrity of any subsurface safety valves in the tubing
25 string and to minimize potential problems due to pressure
leakage.
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The center pocket mandrels of the present lnvent;on
permit other downhole operations to be conducted below the
mandrel by removing the chemical injection valve from the valve
housing. A number of downhole tools such as well logging or
perforating guns can be lowered through the valve pocket to
conduct operations below the mandrel.
Many modifications and variations may be made in the
techniques and structures described herein and depicted in the
accompanying drawings without departing substantially Erom the
concept of the present invention. In particular, it is
recognized it is possible to modify a side pocket mandrel to
include the check valve and certain other features of the
invention and thereby practice the invention. Accordingly, it
should be understood that the form of the invention described
and illustrated herein is exemplary only, and is not intended as
a limitation on the scope thereof.
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