Note: Descriptions are shown in the official language in which they were submitted.
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DIAGNOSTIC TOOL FOR WELL ABANDONMENT TOOL
FIELD
[0001] The current disclosure is directed to a tool for diagnosing gas
leakage
prior to implementing abandonment procedures for plugging wellbores.
BACKGROUND
[0002] Wells access subterranean hydrocarbon formations for the recovery of
oil
and gas. Once the well is exhausted or other failures, procedures are in place
to
abandon the well while protecting other resources including the prevention of
the
contamination of potable water sources and preclusion of surface leakage.
Abandonment procedures have been developed in the oil and gas industry
including
steps to prevent underground interzonal communication and fluid migration up
the
well and into shallow drinking water aquifers or to surface.
[0003] The Alberta Energy Regulator, Alberta Canada, currently requires
that a
"bridge plug" be installed in the well, ostensibly above any source of fluids,
as the
first step in well abandonment. The bridge plug comprises a mechanical tool
having
a body carrying slips and an expandable, elastomeric seal ring. The tool can
be
operated by a tubing string extending down from ground surface. The slips are
expanded to engage the casing and secure the tool in place. The seal ring is
expanded to seal against the casing's inner surface. The body and seal ring
thereby
combine to close and seal the cased bore.
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[0004] During the
conventional abandonment procedure the bridge plug is
positioned and set at a pre-determined depth in the casing bore. A hydraulic
pressure test is then carried out to determine if the bridge plug and well
casing are
competent to hold pressure. The pressure test is currently performed by
filling the
casing bore with water and applying pressure at 1000 psi (6900 kPa) for 10
minutes.
After it has been determined that both the bridge plug and the casing above
the
bridge plug are competent, a column of cement (typically 40 feet in length) is
deposited in the bore immediately above the bridge plug. Finally, the top end
of the
steel casing is cut off at a point below ground level and a vented cap is
welded on
the upper end of the casing.
[0005] However,
problems can commonly arise over time with this system for
plugging and abandoning wells. For example, the elastomeric element of the
bridge
plug may develop surface cracks or otherwise deteriorate and allow fluid to
leak past
it. Minute cracks may also develop in the cement column where the cement abuts
the inside surface of the casing. Further, the cement sheath in the annulus,
around
the outside of the casing, can shrink and develop cracks. One or more of these
defects can result in natural gas or other fluid leaking either up through the
cased
bore or along the outside surface of the casing. Such leakage indicates that
the
abandonment process has failed. This failure is commonly identified when
vegetation surrounding the well at ground surface begins to die. A further
remediation is required, but the problem is to determine where along the well
is the
fluid leaking.
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[0006] Current detection of the location of leaks, using logging systems,
is
expensive and circumstantial, measuring parameters of the cased wellbore that
are
indicative of the potential for a leak, but not determinative. Logging systems
in use
include acoustic, video, caliper, neutron, gamma and the like. Often the tools
are
used on combination. Logs are sometimes run under pressure to heighten
resolution in some circumstances. Accordingly the current logging systems
result in
diagnostic costs in the order of 25 to 75 thousand dollars.
[0007] Presently there are tens of thousands of wells in Alberta, Canada
that
have been abandoned. However, many have been identified as leaking fluid to
ground surface. Therefore, there is a need in the industry for a means to
economically and more accurately locate the source of a leak for proper
abandonment plug procedures under the regulations.
[0008] If plug procedures are not successful, remedial work is required and
retesting completed for packer isolation, all of which adds significantly to
well
abandonment costs.
SUMMARY
[0009] A diagnostic method is provided and described herein for testing
Surface
Casing Vent Flow (SCVF), the flow of fluid, such as gas and/or liquid or any
combination thereof, out of the surface casing/casing annulus. Leaks from the
annulus are often referred to as internal migration.
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[0010] Leaks can also flow from the bore of the casing, the annulus between
the
casing and surface casing or both. The bore of the casing can be effectively
remediated with repair or replacement of the bridge plug. Location of internal
migration is more challenging. The regulator requires the annulus between the
main
casing and surrounding surface casing to be left open to atmosphere. The
surface
casing must be tested for a vent flow or gas migration and if SCVF or gas
migration
problem is detected, remedial repair is required.
[0011] Generally, a resettable, retrievable diagnostic tool is provided
that can is
placed in the cased wellbore and is effective to temporarily seal micro-leaks
in
annular cement about the casing. The tool effects an elastic expansion of the
casing
for affecting annular cement integrity.
[0012] The diagnostic tool is conveyed upon a tubular string of pipe
lowered into
the casing bore of a well. In an embodiment, the tool comprises a central
tubular
mandrel having a longitudinal bore and connected to the pipe string, an
expansion
packer such as a stack of pleated rings slidably mounted on the mandrel, and
first
compression plate mounted on the mandrel at one end of the stack and a second
compression plate slidably mounted on the mandrel at the other end of the
stack;
and a releaseable slip assembly having a slip assembly for actuating the
releasable
slip assembly for releasable compression of the stack of pleated rings.
[0013] The tool can be positioned downhole and is actuated by means such as
the tubular pipe string extending from a rig at ground surface.
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[0014] The tool utilizes the slip assembly for locking the stack of pleated
rings in
the casing. The slip assembly is actuated between a run-in-hole (RIH), pull-
out-of-
hole (POOH) and SET position. Typically the slip assembly and first
compression
plate are positioned at an uphole end of the ring stack and the second
compression
plate is located at the lower end. An actuator housing is axially slidable
over the
mandrel and supports the slip assembly and one complementary portion of the J-
Slot mechanism, in this case the pin. The other complementary portion, the J-
Slot
profile, is located on the mandrel. The lower, second compression plate is
fixed to
the mandrel.
[0015] As illustrated, and picking up at one stage of the slip assembly's
continuous cycle, a pull up on the tubing string and mandrel to an extreme up
position engages an uphole ramp surface of the first compression plate to set
the
slip assembly and fix the actuator housing in the casing. Drag blocks
associated
with the actuator housing ensure operation of the slip assembly. Uphole pull
on the
mandrel and downhole compression plate affixed thereto to compress the stack
against the now-fixed upper compression plate, compressing the rings. The
axially
compressed stack of rings expands radially, engage and expand the casing for
subsequent diagnostics of the annulus outside the casing.
[0016] Thereafter, a set down of the mandrel shifts the slip assembly to
release
the slips to a run in mode or a pull out mode
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[0017] The mandrel and rings are formed of steel, the rings expanding the
casing
within its elastic range. The stack of pleated rings, held in a compressed
expanded
state, continue to interlock with and press against the surrounding casing
wall,
thereby maintaining the wall in an expanded condition.
[0018] In another aspect of the invention, a component assembly is provided
having a stack of pleated steel rings, separated or bracketed by flat annular
washers, which is slidably mounted on a mandrel between flat compression
plates.
The washers serve to distribute compressive force evenly to the pleated rings.
[0019] The rings are preferably dimensioned and configured so that they are
insertable in the casing bore and yet, when compressed a suitable amount (e.g.
50%), they are operative to expand radially sufficiently to press against the
casing
wall and provide a circumferential frictional interlock or engagement with the
casing.
[0020] In a further preferred feature, compression ¨ resistant spacers may
be
positioned in varying amounts between the washers, so as to provide a
characteristic of increasing resistance to radial expansion of the independent
pleated
rings whereby they expand in sequence from the first compression plate to the
second compression plate.
[0021] In a further feature, a sleeve or shield surrounds the stack for
minimizing
interference with casing during the run in and pull out modes and for aiding
in
uniformity of compression of the pleated rings along the stack between the
first
compression plate to the second compression plate.
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[0022] In summary, the diagnostic tool is characterized by metal-to-metal
circumferential radial force application and frictional engagement of the
rings with
the well casing for affecting micro annular flow.
[0023] In still another aspect a method for diagnostic testing is provided
by
temporarily establishing a casing expander for influencing annular cement
sealing in
the course of establishing the success of a prior well abandonment and
identifying
the source of leaks in unsuccessful abandonments.
[0024] A method for identifying a source of surface casing vent flow
comprises
conveying a tool to traverse the well downhole to a specified location along
the
cemented portion of the casing and expanding the casing at the specified
location
for diminishing micro-leaks in the cemented annulus. Thereafter, one
determines a
change in the surface casing vent flow, such as through measurements of any
flow
at surface compared to flow prior to the testing. One can expand the casing by
releasably locking the tool to the casing, and actuating the tool to expand
into the
casing for diminishing micro-leaks in the annulus about the casing.
[0025] The change in the surface casing vent flow can determined by, prior
to
actuating the tool, determining a first baseline surface casing vent flow,
then after
actuating the tool, determining a second surface casing vent flow; and
comparing
the difference in the first and second surface casing vent flows.
[0026] The tool can be conveyed on a string of tubing, traversing the well
to the
specified location. One shifts the tool from a run-in-hole (RIH) position to a
SET
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position and actuates the tool in the SET position to lock a first end of the
stack of
pleated rings to the casing at the specified location and pulling on the
string of tubing
to compress the stack of pleated rings against the first end of the stack,
expanding
the pleated rings for expanding the casing. If the measured surface casing
vent flow
does not represent a change, then one shifts the tool from the SET position to
a pull-
out-of-hole (POOH) position to release the stack of pleated rings and traverse
the
well to an subsequent specified location uphole from the specified location;
and
repeat the, actuating of the tool and then measuring the surface casing vent
flow.
BRIEF DESCRIPTION OF THE FIGURES
[0027] Figure 1A is a one-quarter section, side view of one embodiment of
the
diagnostic tool in the downhole manipulation, run-in-hole (RIH) mode;
[0028] Figure 1B is a one-quarter section, side view of the tool of Fig.
1A, after an
intermediate downhole shift, then shown in an uphole manipulation to shift the
tool
for the next stage or to pull-out-of-hole (POOH), the profile preventing
actuation of
the slip assembly;
[0029] Figure 1C is a one-quarter section, side view of the tool of Fig.
1A, after an
intermediate downhole shift then shown in an uphole manipulation to engage the
cone and set the slip assembly to engage the casing;
[0030] Figure 2 is a rolled out plan view of a J-Profile of one embodiment
of the J-
Slot mechanism;
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[0031] Figure 2A is a partial, enlarged view of the slip assembly,
including
mandrel and actuator housing according to Fig. 1A, the slip assembly in a RIH
position;
[0032] Figure 2B is a partial, enlarged view of the slip assembly, mandrel
and
actuator housing according to Fig. 1B, the slip assembly in the POOH position;
[0033]
[0034] Figure 2C is a partial, enlarged view of the slip assembly, mandrel
and
actuator housing according to Fig. 1C, the slip assembly in a SET position;
[0035] Figure 3 is a flow chart of a diagnostic procedure according to one
embodiment;
[0036] Figure 4A is a partial, enlarged view of the stack of pleated rings
fit with a
running shield, the tool in the POOH position;
[0037] Figure 4B is a partial, enlarged view of the stack of pleated rings
fit with
the running shield of Fig. 5A, the tool in the POOH position with the shield
engaged
between the expanded rings and the expanded casing; and
[0038] Figure 5 is a partial, enlarged view of the stack of pleated rings
fit with a
running shield, one discontinuous shield extending about the full
circumference and
split axially.
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[0039] Figure 6A is a side view of the rings of a portion of the tool in a
cross-
section of casing, and in one embodiment the stack of pleated rings having an
increasing density of compression modifiers closer to the actuating end of the
stack;
[0040] Figure 6B is a close up view of adjacent pleated rings, such as
those
shown in Fig. 6A, the stack cut away above and below to illustrate the pleated
rings
separated by flat washers, having adjacent peaks and troughs misaligned, one
spacer being illustrated in exploded view separate from the pleated rings, and
a
mandrel passing therethrough;
[0041] Figure 6C is a close up view of adjacent pleated rings, according to
Fig. 6B, with adjacent pleat peaks and troughs aligned;
DESCRIPTION OF THE EMBODIMENTS
[0042] Having reference to Fig. 1A, a diagnostic tool for manipulating the
annulus
about well casing is provided, typically used in a methodology for confirming
integrity
of an abandoned well or well to be abandoned or identifying the downhole
location of
annular fluid migration or leak path. The tool is sized for a cased well, such
as that
typically extending through a surface casing or other outer casing, forming an
annulus that has been cemented and may not have retained its integrity,
resulting in
an internal leak path.
[0043] The tool 10 comprises a central tubular mandrel 14 attached and
conveyed downhole of the bore 50 of the casing 54 on a string of tubing, such
as
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jointed pipe or coiled tubing. A stack 16 of pleated metal pleated rings 18 is
positioned on the mandrel 14. The rings 18 are separated and spaced apart by
flat,
annular washers 20. First and second annular compression plates 22, 24, having
facing perpendicular shoulders, straddle or bracket the stack 16 at its
upper/uphole
and lower/downhole ends respectively. The stack of pleated rings is also
described
in companion international application PCT/CA2016/051429 filed Monday, Dec. 5,
. 2016 and claiming priority of CA 2,913,933 filed Dec. 4,2015.
[0044] The second or downhole compression plate 24 is secured or fixed to
the
mandrel 14. Plate 24 can be secured with shear screws or other releasable
fasteners as required for retrievability if the tool becomes stuck. The uphole
compression plate 22 is axially slidable along the mandrel 14 and axially
delimited
on the mandrel by a shoulder 26 to pre-determine the uphole location thereon.
The
washers 20 and pleated rings 18 are slidably mounted on the mandrel 14 between
the uphole and downhole compression plates 22,23.
[0045] Best shown in Figs. 2A to 2C, an uphole slip assembly 30 is
mounted to
the mandrel 14 uphole of the stack of pleated rings 16. The slip assembly 30
determines the operation and release of slips 44 to lock the tool 10 against
the
casing 54. Generally, the slip assembly is releasably engageable with the
inside
wall 52 of the casing 54 and comprises a housing 32 slidable over the mandrel
14
for alternately releasing and compressing the stack of rings. A drag block 46
and
slips 44 are supported by the housing 32. A pin 42 and slot assembly is
located
between the housing 32 and the mandrel 14, the slot has a J-Profile 40 having
at
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least a run-in-hole (RIH) position for spacing the slips from a slip cone 34,
a pull-out-
of-hole (POOH) position for spacing the slips from the slip cone, and a slip
set (SET)
position for engaging slips 44 with the slip cone 34 for axially compressing
the
pleated rings 18 between the first and second compression rings 22,24 for
radially
expanding the pleated rings.
[0046] The actuator housing 32 is axially slidable on the mandrel, all of
which is
uphole of the uphole compression plate 22. The uphole face of the upper
compression plate 22 is a ramp-like surface or cone 34 compatible with the
slips 44.
[0047] The actuator housing 32 is axially movable along the mandrel 14 as
part
of the slip assembly 30, variably delimited by cooperation of the pin 42
configured to
follow the J-Profile 40. Drag blocks 46 are fixed axially within the housing
32, and
are biased radially outwardly to the casing to enable shifting of the J-
Profile with
mere uphole and downhole manipulation of the mandrel.
[0048] The J-profile 40 and pin 42 alternately space the slip 44 from the
cone 34
for free running in and out of the casing, or to enable axial engagement of
the slips
44 with the cone 34 for slip actuation. As shown in this embodiment, the J-
Profile 40
is formed in the mandrel 14 and the pin 42 is fixed to the housing 32
[0049] With reference to Fig. 2, the slot of the J-Profile 40 sequences
four stages
of operation or positions: in Fig. 2C, an uphole manipulation of the mandrel
to pull
the cone 34 into engagement with the slips (SET) at position C; in Fig. 2A, an
downhole shift to position A to release the slips or run-in-hole RIH, in Fig.
2B an
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uphole pull of the mandrel to pull-out-of¨hole POOH at position B with the
slips
spaced from the cone; and an intermediate downhole shift (A') before the cycle
repeats.
[0050] As shown in Fig. 6, the pleated rings 18 are formed of
corrosion¨resistant
material, such as stainless steel. Each pleated ring 16 is sized for a sliding
fit on the
mandrel 14 and are dimensioned and configured so that they are insertable in
the
bore 50 of the casing 54 in their normal, pleated condition but, when
compressed
axially, for example partly compressed to about 1/2 of their axial height,
they are
capable of extending out radially sufficiently so as to reach the inside
surface 52 of
the bore 50 and to press firmly against it, thereby frictionally engaging it
and slightly
expanding the wall of casing 54, including the outer diameter of the casing
into the
annulus and any cement 56 therein.. Simply, the uncompressed pleated rings
have
a first diameter less than that of the casing and when in the compressed
position,
the pleated rings have a second diameter adapted to engage the casing.
[0051] With reference to Figs. 6A, the stack 24 comprises flat annular
washers 20
positioned between each adjacent pair of pleated rings 18. As shown in Fig. 6B
and
6C, the rings 18 can be oriented with their facing peaks 80 misaligned or
aligned.
As shown in Fig. 6B, if the peaks 80 of adjacent, facing pleated rings are
misaligned,
the intermediate flat washer is unsupported, and can be subject to
deformation. As
shown in Fig. 60, if the peaks 80 of adjacent, facing pleated rings 18 are
aligned, the
intermediate flat washer 20 is supported between acting peaks and all the
axially
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compressive force is transferred through the pleated rings. The flat washer
can be
steel or an elastomeric including Durometer 90 nitrile rubber.
[0052] Table 1 sets forth the relevant dimensional, material and
compression
data from a test in which a stack 16 of pleated rings 18 was mounted on a
mandrel
14 and axially compressed within a 60" (152cm) length of oilfield 4.5"
(11.4cm) steel
casing 27 using a press.
Table 1
mandrel outside diameter - 2.5" (64mnn) Each ring pleat height - 0.375"
(9.5mm)
casing inside diameter - 3.826" (97.2mm) ring material - 410 stainless
steel
casing wall thickness - 0.337" (8.6mm) ring wall thickness - 0.025" (0.6mm)
casing outside diameter - 4.5" (114mm) Pleat spacers (copper tubing),
0.375"-
(9.5mm)
diameter and wall thickness - 0.0625"
(1.6mm)
number of pleated rings - 10" (254mm) flat steel washer thickness - 0.125"
(3.2mm)
inside ring diameter - 2.5" (64nnm) compressive force applied - -27,000
lb/ft
outside ring diameter prior to compression - extent of stack length reduction -
about 40%
3.750" (95mm)
outside ring diameter (unconstrained) after Result: Casing expansion - about
0.008"
compression - 3.834" (97.4mm) (40.084") (0.2mm).
(A0.2mm)
[0053] The test showed that the stack of rings outwardly bulged the
adjacent
casing wall by about 0.008" (0.2mm). Testing confirms that suggests the
stacked-
ring packer can be set and released multiple times in a single run.
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OPERATION
[0054] A method is provided for identifying a source of surface casing vent
flow
from an abandoned well. Typically the wells are completed with casing and have
a
cemented annulus about at least a portion thereof.
[0055] The method comprises conveying a tool to traverse the well downhole
to a
specified location along the cemented portion of the casing, expanding the
casing at
the specified location for diminishing micro-leaks in the cemented annulus;
and then
determining a change in the surface casing vent flow. The tool can be conveyed
on
a string of tubing for traversing the well to the specified location and for
shifting the
tool from a run-in-hole (RIFI) position to a SET position; actuating the tool
in the SET
position to lock a first end of a stack of pleated rings to the casing at the
specified
location; pulling the string of tubing to compress the stack of pleated rings
against
the first end of the stack, expanding the pleated rings for expanding the
casing; and
then thereafter measuring the surface casing vent flow.
[0056] As above, the expanding the casing comprises adjusting the tool from
a
traversing the well mode to a setting the tool mode for releasable locking the
tool to
the casing; and actuating the tool to expand into the casing for diminishing
the
micro-leaks.
[0057] One can determine a change in the surface casing vent flow by, prior
to
actuating the tool, determining a first baseline surface casing vent flow.
Then, after
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actuating the tool, determining a second surface casing vent flow and
comparing the
difference in the first and second surface casing vent flows.
[0058] In greater detail, tubing conveys the tool downhole; the mandrel
connected in the string of tubing, typically adjacent the downhole end
thereof. The
mandrel 14 serves to support the stack 16 of pleated rings 18. Actuation of
the tool
is carried out by manipulating the tubing string from surface which
manipulates
the mandrel 14. Simply, the tool is RIH to a specified location, actuated to
expand
the casing, surface casing vent flow is monitored and if the flow is not
significantly
altered, the tool would be too low in the well to have intercepted the leak.
The tool
can be moved further uphole and the test is repeated.
[0059] Again, and with reference to Fig. 2 and Figs. 2A, 2B and 20, the
mandrel
is manipulated downhole and the tool is RIH (A') to the specified location in
the well
casing. The mandrel is pulled up to SET (C) and pulled up further at a tension
sufficient to expand the casing and affect the cement the annulus. Once the
surface
casing vent flow test is complete, which can be hours, days or weeks, the
mandrel is
set down again to the intermediate shift position A to continue downhole RIH,
or
merely to shift to pull up again (B) and POOH.
[0060] In order to ascertain the magnitude of the leak and determine if the
diagnostic tool has identified a well location of interest, a baseline SCVF
can be
obtained. This can include a quantitative test, using a vent testing device
including a
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meter, for measuring the SCVF such as in cubic meters per day. Such a test can
take place over days or weeks.
[0061] Using a
plan for tool locations, a first specified position is identified, the
slip assembly is shifted to the RIH position and the diagnostic tool is run
downhole to
the selected, specified, pre-determined depth. The conveyance tubing is
shifted to
the SET position. The conveyance tubing is pulled up to set the slips, locking
the
uphole compression plate to the casing. The mandrel is pulled uphole to pull
the
cone against the slips and set the tool in the casing. One continues to pull
the
mandrel uphole and, as the uphole compression plate is arrested axially in the
casing, the mandrel pulls the downhole compression plate against the stack
against
the uphole compression plate, compressing the pleated rings. The
axially-
compressed stack of rings expands radially, engages and expands the casing for
subsequent diagnostics. As
discussed, the rings expand the casing within its
elastic range. The
slip, uphole compression plate and moving downhole
compression plate, compress the stack sufficiently so as to cause the pleated
rings
to partly flatten, expand radially, press against the adjacent casing wall and
effect a
metal¨to¨metal circumferential frictional engagement with the casing. The
stack of
pleated rings, held in a compressed expanded state, continue to interlock with
and
press against the surrounding casing wall, thereby maintaining the wall in an
expanded condition.
[0062] The
casing is expanded into the annular cement. Micro leak paths
typically occur in the cemented annulus between the casing exterior and the
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wellbore. By expanding the casing, once can compress and aid the sealing of
these
micro-annular leak paths, uphole leakage therethrough to surface being
temporarily
reduced or blocked.
[0063] The stacked-ring packer has a myriad of interstitial spaces that
will allow
flow on the inside of the casing. If the upper compression plate includes an
elastomeric packer, such as that between cone and the compression ring, casing
bore sealing could similarly be effected in addition to annular sealing.
Elastomeric
packer compression could be delimited by stops along the mandrel to avoid over
compression when actuating the more robust stack.
[0064] One maintains uphole tension on the conveyance string and mandrel to
hold the stack in place and expansion of the rings. If the selected location
in the well
is at or above the leakage along the annulus, the leakage should be lessened,
reducing the flow.
[0065] At surface, the SCVF leakage is measured over time. In general
confirmation, any SCVF issues are usually visible at surface with a simple
bubble
test. As there can be a lag between restriction of any leaks and the flow at
surface,
the operator will wait a commensurate period of time before conduction this
qualification test. Water is poured around the casing and bubbles can be seen
or
alternately the casing vent valve is opened and a hose from the line fed into
a water
bath and bubbles observed.
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[0066] Alternatively a more quantitative test can be performed, using a
vent
testing device including a meter, for measuring the SCVF such as in cubic
meters
per day. Electronic detection equipment may be used, including sophisticated
detection equipment coupled with analysis to compare gas chemistry to identify
production zones to determine the source of the gas. Tests can take place over
days to weeks.
[0067] If one determines a reduction in SCVF has been achieved, the leak
has
been identified and remediation could be applied. However, the testing has
determined that the leak is at or even lower than the selected test location.
Depending on regulations in place for the well location, including
consideration of the
identified location relative to the depth of ground water, and other
considerations,
one may need to run deeper in hole. One could then shift the tool to RIH, move
the
tool the a subsequent, lower selected location and repeat the testing.
[0068] If the identified location was at acceptable depth, remediation
could occur,
using one of the established methods for re-abandonment including Applicant's
co-
pending application PCT/CA2016/051429 utilizing a tool in combination with an
elastomer applied through ports formed in the casing or more conventional
cement
squeezes through perforations, abrasajet cuts or section milling of casing.
[0069] If, at the selected location, the testing did not reduce the SCVF
below a
threshold, then the leak is uphole of the selected location
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[0070] In this instance, the tool is shifted to POOH and moved uphole. In
releasing the tool, the conveyance tubing is manipulated downhole, driving the
lower
compression plate downhole, decompressing and lengthening the stack and
shrinking the pleated rings in diameter. Shortly thereafter, the cone pulls
away from
the slips and the tool is released from the casing.
[0071] If the stack of pleated rings are at all damaged, such as by a bore
pressure test when set, the tool could be tripped out for repair or
replacement. If
moved, the tool could be located at the subsequent selected location and the
set,
test and surface measurement repeated again.
[0072] The tool is run to higher location if necessary, and repeat the
setting,
testing and releasing as necessary. When the tool is actuated, and SCVF
continues, then the diagnostic tool is deemed to below the source of the leak
as it
was ineffective in blocking or restricting the leak path. The tool is
successively
moved uphole and set and SCVF measured until the source is located. The
location
and relocation of the diagnostic tool can be made on an incremental stepwise
basis,
or more informed or substantive moves can be made based on well logs or other
known well characteristics.
[0073] Once complete, or for tool recovery, one pulls up on conveyance
tubing to
shift the slip assembly for POOH.
[0074] Release of tension on the conveyance tubing, permits the lower
compression plate to release the stack, the upper cone to release from the
slip and
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tool to be released from the well. The ring stack lengthens and reduces in
diameter,
releasing from the casing wall.
[0075] In short, and with reference to the flow chart of Fig. 3, and with
reference
to the tool positions as shown in Figs. 1A through 2C, a baseline of the SCVF
for the
leaking well is established, typically using a vent metering device. This
could take
days to establish a base rate. Thereafter, the diagnostic tool is first
located in the
lower wellbore, surface flow tested, and if the leak was not already located,
then the
operator sequentially moves the tool upward, targeting likely areas such as
shallow
gas zones that were not ever produced, or where previous well data may suggest
likely areas of sources. Depending on the nature of the leak the tool may be
left in
position for minutes, hours or days.
[0076] Operation of the stack of pleated rings can be optimized to minimize
hang-
up on casing interfaces and assist with uniform actuation of the rings along
the
stack.
[0077] In one embodiment, as shown in Figs. 4A and 4B, one or more sleeves
or
shields can be wrapped circumferentially about the stack 16.
[0078] Two or more elongate leaves 60 can be secured at a first end at the
first
compression plate 22 and extend axially along the stack of pleated rings to a
second
end adjacent the second compression plate 24. Each leaf being arcuate and
extending circumferentially about a portion of the circumference of the stack
of
pleated rings. Each leaf further comprises a guide extending axially from the
second
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end; and a bracket at the second compression plate through which the guide
extends slidably and restraining the guide radially to the second compression
plate.
[0079] As stated, and in more detail with reference to the figures, axially
elongate
leaves 50 are secured at a first end at the first compression plate 22 and
extend
axially along the stack of pleated rings to a second end adjacent the second
compression plate 24, each leaf 60 being arcuate and extending
circumferentially
about at least a portion of the circumference of the stack 16 of pleated
rings.
[0080] As shown in Fig. 5, a single leaf can be typically split
longitudinally, such
as encompassing about a 340 degree wrap or full wrap, to enable
circumferential
expansion with the stack is actuated.
[0081] In the case of two or more independent leaves 60,60 .... The
material is
are inherently expandable circumferentially and with respect to each other
when
expanded radially with the pleated rings. Each leaf 60 further comprises a
guide or
leg 64 extending axially from the second end and a bracket 66 located at the
second
compression plate 24 through which the leg extends slidably for restraining
the guide
radially to the second compression plate 24. The leaves 60 aid the movement of
the
pleated rings 15 within the stack 16 and also the entirety of the stack of
pleated rings
of the tool along the casing 54, where otherwise the rings or spacers are
otherwise
prone to catch on inner casing features including collar interfaces.
[0082] When the stack is actuated to expand the casing, the leaves 60 are
sandwiched between the pleated rings 18 and the casing 54.
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[0083]
Similarly, on this or other downhole tools using a compressive stack of
pleated rings for casing sealing or expansion, a leaf 60 or leaves 60,60 ...
can also
be provided for improved traversing and uniformity in actuation.
[0084] In
another embodiment, as shown in Figs. 6B and 6C, the stack 24 can
further includes compression-modifying or resistant spacers 82 positioned
between
pleats and the flat washers 7. The
spacers 82 are distributed in varying
concentrations or density that diminishes upwardly from the downhole
compression
plate 24 to the uphole compression plate 22. The uphole compression plate
becomes locked or fixed to the casing when the slips are set, and stack
actuation
occurs from the downhole compression plate up towards the uphole plate. The
concentrations and distributions are selected so as to facilitate the desired
sequential compression of the rings 18 from the stack's fixed end 24. The
spacers
82 can be formed of short lengths of copper tubing 82T. The compression
spacers
82 provide a characteristic of increasing resistance to compression of the
individual
pleated rings from the uphole compression plate 22 to the actuated compression
plate 24. Thus the pleated rings 18 that are sliding along the mandrel 14, at
the
uphole end in this case, and relative to the casing 54, from the actuated
compression plate 24 towards the fixed compression plate 22, are the last to
be
compressed. The pleated rings 18 of the stack 16 therefore expand in sequence
to
control the drag of the expanding rings as they are axially compressed.
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