Note: Descriptions are shown in the official language in which they were submitted.
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PLUGGING AND ABANDONING A WELL USING A SET-DELAYED CEMENT
COMPOSITION COMPRISING PUMICE
BACKGROUND
[0001] Embodiments relate to subterranean cementing operations and, in certain
embodiments, to set-delayed cement compositions and methods of using set-
delayed cement
compositions in subterranean formations.
[0002] Cement compositions may be used in a variety of subterranean
operations. For
example, in subterranean well construction, a pipe string (e.g., casing,
liners, expandable
tubulars, etc.) may be run into a wellbore and cemented in place. The process
of cementing
the pipe string in place is commonly referred to as "primary cementing." In a
typical primary
cementing method, a cement composition may be pumped into an annulus between
the walls
of the wellbore and the exterior surface of the pipe string disposed therein.
The cement
composition may set in the annular space, thereby forming an annular sheath of
hardened,
substantially impermeable cement (i.e., a cement sheath) that may support and
position the
pipe string in the wellbore and may bond the exterior surface of the pipe
string to the
subterranean formation. Among other things, the cement sheath surrounding the
pipe string
functions to prevent the migration of fluids in the annulus, as well as
protecting the pipe string
from corrosion. Cement compositions also may be used in remedial cementing
methods, for
example, to seal cracks or holes in pipe strings or cement sheaths, to seal
highly permeable
formation zones or fractures, to place a cement plug, and the like.
[0003] A broad variety of cement compositions have been used in subterranean
cementing operations. In some instances, set-delayed cement compositions have
been used.
Set-delayed cement compositions are characterized by remaining in a pumpable
fluid state for
about one day or longer (e.g., about 7 days, about 2 weeks, about 2 years or
more) at room
temperature (e.g., about 80 F) in quiescent storage. When desired for use,
the set-delayed
cement compositions should be capable of being activated whereby reasonable
compressive
strengths are developed. For example, a cement set activator may be added to a
set-delayed
cement composition whereby the composition sets into a hardened mass. Among
other things,
the set-delayed cement composition may be suitable for use in wellbore
applications, for
example, where it is desired to prepare the cement composition in advance.
This may allow,
for example, the cement composition to be stored prior to its use. In
addition, this may allow,
for example, the cement composition to be prepared at a convenient location
and then
transported to the job site. Accordingly, capital expenditures may be reduced
due to a
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reduction in the need for on-site bulk storage and mixing equipment. This may
be particularly
useful for offshore cementing operations where space onboard the vessels may
be limited.
[0004] In cementing methods, such as plug-and-abandon operations, a plug is
formed
in a wellbore to seal off the wellbore for abandonment. In performing plug-and-
abandon
operations, a plugging composition may be placed in the wellbore at a desired
depth. The
plugging composition should set in the wellbore, forming a hardened mass
(e.g., a plug) that
seals off selected intervals of the wellbore. The plug should prevent and/or
reduce zonal
communication and migration of fluids that may contaminate water-containing
formations. It
may desirable in certain instances to form one or more plugs in the wellbore
adjacent to
hydrocarbon-producing formations and water-containing formations.
[0005] While set-delayed cement compositions have been developed heretofore,
challenges exist with their successful use in subterranean cementing
operations. For example,
set-delayed cement compositions prepared with Portland cement may have
undesired gelation
issues which can limit their use and effectiveness in cementing operations.
Other set-delayed
compositions that have been developed, for example, those comprising hydrated
lime and
quartz, may be effective in some operations but may have limited use at lower
temperatures
as they may not develop sufficient compressive strength when used in
subterranean formations
having lower bottom hole static temperatures.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0006] These drawings illustrate certain aspects of some of the embodiments of
the
present method, and should not be used to limit or define the method.
[0007] FIG. 1 illustrates a system for the preparation and delivery of a set-
delayed
cement composition into a wellbore in accordance with certain embodiments.
[0008] FIG. 2A illustrates a liquid storage vessel that may be used in the
delivery of
a set-delayed cement composition into a wellbore in accordance with certain
embodiments.
[0009] FIG. 2B illustrates a self-contained delivery system that may be used
in the
delivery of a set-delayed cement composition into a wellbore in accordance
with certain
embodiments.
[0010] FIG. 3 illustrates an example embodiment of surface equipment that may
be
used in the placement of a set-delayed cement composition in accordance with
certain
embodiments.
[0011] FIG. 4 illustrates an embodiment for the placement of a set-delayed
cement
composition across a set of open perforations and/or a casing leak in
accordance with certain
embodiments.
[0012] FIG. 5 illustrates an embodiment for the placement of a set-delayed
cement
composition within an openhole section in accordance with certain embodiments.
[0013] FIG. 6 illustrates an embodiment for the placement of a set-delayed
cement
composition across the top of a fish and/or casing stub in accordance with
certain
embodiments.
[0014] FIG. 7 illustrates an embodiment for the placement of a set-delayed
cement
composition utilizing a wireline deployed dump bailer in accordance with
certain
embodiments.
[0015] FIG. 8 illustrates an example of surface equipment that may be used in
embodiments comprising a wireline dump bailer for placement of a set-delayed
cement
composition in accordance with certain embodiments.
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DESCRIPTION OF PREFERRED EMBODIMENTS
[00161 Embodiments relate to subterranean cementing operations and, in certain
embodiments, to set-delayed cement compositions and methods of using set-
delayed cement
compositions in subterranean formations. In particular embodiments, set-
delayed cement
compositions are described for use in plug and abandon operations.
[0017] Embodiments of the set-delayed cement compositions may generally
comprise
water, pumice, hydrated lime, and a set retarder. Optionally, the set-delayed
cement
compositions may further comprise a dispersant and/or a viscosifier.
Embodiments of the set-
delayed cement compositions may be foamed. Advantageously, embodiments of the
set-
delayed cement compositions may be capable of remaining in a pumpable fluid
state for an
extended period of time. For example, the set-delayed cement compositions may
remain in a
pumpable fluid state for about I day, about 2 weeks, about 2 years, or longer.
Advantageously,
the set-delayed cement compositions may develop reasonable compressive
strengths after
activation at relatively low temperatures. While the set-delayed cement
compositions may be
suitable for a number of subterranean cementing operations, they may be
particularly suitable
for use in subterranean formations having relatively low bottom hole static
temperatures, e.g.,
temperatures less than about 200 F or ranging from about 100 F to about 200 F.
In alternative
embodiments, the set-delayed cement compositions may be used in subterranean
formations
having bottom hole static temperatures up to 450 F or higher.
[0018] The water used in embodiments of the set-delayed cement compositions
may
be from any source provided that it does not contain an excess of compounds
that may
undesirably affect other components in the set-delayed cement compositions.
For example, a
set-delayed cement composition may comprise fresh water or salt water. Salt
water generally
may include one or more dissolved salts therein and may be saturated or
unsaturated as desired
for a particular application. Seawater or brines may be suitable for use in
embodiments.
Further, the water may be present in an amount sufficient to form a pumpable
slurry. In certain
embodiments, the water may be present in the set-delayed cement composition in
an amount
in the range of from about 33% to about 200% by weight of the pumice. In
certain
embodiments, the water may be present in the set-delayed cement compositions
in an amount
in the range of from about 35% to about 70% by weight of the pumice. One of
ordinary skill
in the art with the benefit of this disclosure will recognize the appropriate
amount of water for
a chosen application.
[0019] Embodiments of the set-delayed cement compositions may comprise pumice.
Generally, pumice is a volcanic rock that can exhibit cementitious properties
in that it may set
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and harden in the presence of hydrated lime and water. The pumice may also be
ground.
Generally, the pumice may have any particle size distribution as desired for a
particular
application. In certain embodiments, the pumice may have a mean particle size
in a range of
from about 1 micron to about 200 microns. The mean particle size corresponds
to d50 values
as measured by particle size analyzers such as those manufactured by Malvern
Instruments,
Worcestershire, United Kingdom. In specific embodiments, the pumice may have a
mean
particle size in a range of from about 1 micron to about 200 microns, from
about 5 microns to
about 100 microns, or from about 10 microns to about 25 microns. In one
particular
embodiment, the pumice may have a mean particle size of less than about 15
microns. An
example of a suitable pumice is available from Hess Pumice Products, Inc.,
Malad, Idaho, as
DS-325 lightweight aggregate, having a particle size of less than about 15
microns. It should
be appreciated that particle sizes too small may have mixability problems
while particle sizes
too large may not be effectively suspended in the compositions. One of
ordinary skill in the
art, with the benefit of this disclosure, should be able to select a particle
size for the pumice
suitable for a chosen application.
[0020] Embodiments of the set-delayed cement compositions may comprise
hydrated
lime. As used herein, the term "hydrated lime" will be understood to mean
calcium hydroxide.
In some embodiments, the hydrated lime may be provided as quicklime (calcium
oxide) which
hydrates when mixed with water to form the hydrated lime. The hydrated lime
may be included
in embodiments of the set-delayed cement compositions, for example, to form a
hydraulic
composition with the pumice. For example, the hydrated lime may be included in
a pumice-
to-hydrated-lime weight ratio of about 10:1 to about 1:1 or 3:1 to about 5:1.
Where present,
the hydrated lime may be included in the set-delayed cement compositions in an
amount in the
range of from about 10% to about 100% by weight of the pumice, for example. In
some
embodiments, the hydrated lime may be present in an amount ranging between any
of and/or
including any of about 10%, about 20%, about 40%, about 60%, about 80%, or
about 100%
by weight of the pumice. In some embodiments, the cementitious components
present in the
set-delaycd cement composition may consist essentially of the pumice and the
hydrated lime.
For example, the cementitious components may primarily comprise the pumice and
the
hydrated lime without any additional components (e.g., Portland cement, fly
ash, slag cement)
that hydraulically set in the presence of water. One of ordinary skill in the
art, with the benefit
of this disclosure, will recognize the appropriate amount of the hydrated lime
to include for a
chosen application.
[0021] Embodiments of the set-delayed cement compositions may comprise a set
retarder. A broad variety of set retarders may be suitable for use in the set-
delayed cement
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compositions. For example, the set retarder may comprise phosphonic acids,
such as amino
tris(methylene phosphonic acid), ethylenediamine tetra(methylene phosphonic
acid),
diethylenetriamine penta(methylene phosphonic acid), etc.; lignosulfonates,
such as sodium
lignosulfonate, calcium lignosulfonate, etc.; salts such as stannous sulfate,
lead acetate,
monobasic calcium phosphate, organic acids, such as citric acid, tartaric
acid, etc.; cellulose
derivatives such as hydroxyl ethyl cellulose (HEC) and carboxymethyl
hydroxyethyl cellulose
(CMHEC); synthetic co- or ter-polymers comprising sulfonate and carboxylic
acid groups
such as sulfonate-functionalized acrylamide-acrylic acid co-polymers; borate
compounds such
as alkali borates, sodium metaborate, sodium tetraborate, potassium
pentaborate; derivatives
thereof, or mixtures thereof. Examples of suitable set retarders include,
among others,
phosphonic acid derivatives. One example of a suitable set retarder is Micro
Matrix cement
retarder, available from Halliburton Energy Services, Inc. Generally, the set
retarder may be
present in the set-delayed cement compositions in an amount sufficient to
delay the setting for
a desired time. In some embodiments, the set retarder may be present in the
set-delayed
cement compositions in an amount in the range of from about 0.01% to about 10%
by weight
of the pumice. In specific embodiments, the set retarder may be present in an
amount ranging
between any of and/or including any of about 0.01%, about 0,1%, about 1%,
about 2%, about
4%, about 6%, about 8%, or about 10% by weight of the pumice. One of ordinary
skill in the
art, with the benefit of this disclosure, will recognize the appropriate
amount of the set retarder
to include for a chosen application.
[0022] As previously mentioned, embodiments of the set-delayed cement
compositions may optionally comprise a dispersant. Examples of suitable
dispersants include,
without limitation, sulfonated-formaldehyde-based dispersants (e.g.,
sulfonated acetone
formaldehyde condensate), examples of which may include Daxad 19 dispersant
available
from Geo Specialty Chemicals, Ambler, Pennsylvania. Other suitable dispersants
may be
polycarboxylated ether dispersants such as Liquiment 558IF and Liquiment
514L
dispersants available from BASF Corporation Houston, Texas; or Ethaerylim G
dispersant
available from Coatex, Genay, France. An additional example of a suitable
commercially
available dispersant is CF12r"-3 dispersant, available from Halliburton Energy
Services, Inc,
Houston, Texas. The Liquiment 514L dispersant may comprise 36% by weight of
the
polycarboxylated ether in water. While a variety of dispersants may be used in
accordance
with embodiments, polycarboxylated ether dispersants may be particularly
suitable for use in
some embodiments. Without being limited by theory, it is believed that
polycarboxylated
ether dispersants may synergistically interact with other components of the
set-delayed cement
composition. For example, it is believed that the polycarboxylated ether
dispersants may react
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with certain set retarders (e.g., phosphonic acid derivatives) resulting in
formation of a gel that
suspends the pumice and hydrated lime in the composition for an extended
period of time.
[0023] In some embodiments, the dispersant may be included in the set-delayed
cement compositions in an amount in the range of from about 0.01% to about 5%
by weight
of the pumice. In specific embodiments, the dispersant may be present in an
amount ranging
between any of and/or including any of about 0.01%, about 0.1%, about 0.5%,
about 1%, about
2%, about 3%, about 4%, or about 5% by weight of the pumice. One of ordinary
skill in the
art, with the benefit of this disclosure, will recognize the appropriate
amount of the dispersant
to include for a chosen application.
[0024] In some embodiments, a viscosifier may be included in the set-delayed
cement
compositions. The viscosifier may be included to optimize fluid rheology and
to stabilize the
suspension. Without limitation, examples of viscosifiers include swellable
clays such as
bentonite or biopolymers such as cellulose derivatives (e.g., hydroxyethyl
cellulose,
carboxymethyl cellulose, carboxymethyl hydroxyethyl cellulose). An example of
a
commercially available viscosifier is SA-IOISTM available from Halliburton
Energy Services,
Inc., Houston, TX. The viscosifier may be included in the set-delayed cement
compositions
in an amount in the range of from about 0.01% to about 0.5% by weight of the
pumice. In
specific embodiments, the viscosifier may be present in an amount ranging
between any of
and/or including any of about 0.01%, about 0.05%, about 0.1%, about 0.2%,
about 0.3%, about
0.4%, or about 0.5% by weight of the pumice. One of ordinary skill in the art,
with the benefit
of this disclosure, will recognize the appropriate amount of viscosifier to
include for a chosen
application.
[0025] Other additives suitable for use in subterranean cementing operations
also may
be included in embodiments of the set-delayed cement compositions. Examples of
such
additives include, but are not limited to: weighting agents, lightweight
additives, gas-
generating additives, mechanical-property-enhancing additives, lost-
circulation materials,
filtration-control additives, fluid-loss-control additives, defoaming agents,
foaming agents,
thixotropic additives, and combinations thereof. Examples of suitable
weighting agents
include, for example, materials having a specific gravity of 3 or greater,
such as barite. In
embodiments, one or more of these additives may be added to the set-delayed
cement
compositions after storing but prior to the placement of a set-delayed cement
composition into
a subterranean formation. A person having ordinary skill in the art, with the
benefit of this
disclosure, should readily be able to determine the type and amount of
additive useful for a
particular application and desired result.
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[0026] Those of ordinary skill in the art will appreciate that embodiments of
the set-
delayed cement compositions generally should have a density suitable for a
particular
application. By way of example, the set-delayed cement compositions may have a
density in
the range of from about 4 pounds per gallon ("lb/gal") to about 20 lb/gal. In
certain
embodiments, the set-delayed cement compositions may have a density in the
range of from
about 8 lb/gal to about 17 lb/gal. Embodiments of the set-delayed cement
compositions may
be foamed or unfoamed or may comprise other means to reduce their densities,
such as hollow
microspheres, low-density elastic beads, or other density-reducing additives
known in the art.
In embodiments, the density may be reduced after storing the composition, but
prior to
placement in a subterranean formation. Those of ordinary skill in the art,
with the benefit of
this disclosure, will recognize the appropriate density for a particular
application.
[0027] As previously mentioned, the set-delayed cement compositions may have a
delayed set in that they remain in a pumpable fluid state for one day or
longer (e.g., about 1
day, about 2 weeks, about 2 years or more) at room temperature (e.g., about 80
F) in quiescent
storage. For example, the set-delayed cement compositions may remain in a
pumpable fluid
state for a period of time from about 1 day to about 7 days or more. In some
embodiments, the
set-delayed cement compositions may remain in a pumpable fluid state for about
1 day, about
7 days, about 10 days, about 20 days, about 30 days, about 40 days, about 50
days, about 60
days, or longer. A fluid is considered to be in a pumpable fluid state where
the fluid has a
consistency of less than 70 Bearden units of consistency ("Bc"), as measured
on a pressurized
consistometer in accordance with the procedure for determining cement
thickening times set
forth in API RP Practice 10B-2, Recommended Practice for Testing Well Cements,
First
Edition, July 2005.
[0028] When desired for use, embodiments of the set-delayed cement
compositions
may be activated (e.g., by combination with an activator) to set into a
hardened mass. The
term "cement set activator" or "activator", as used herein, refers to an
additive that activates a
set-delayed or heavily retarded cement composition and may also accelerate the
setting of the
set-delayed, heavily retarded, or other cement composition. By way of example,
embodiments
of the set-delayed cement compositions may be activated to form a hardened
mass in a time
period in the range of from about 1 hour to about 12 hours. For example,
embodiments of the
set-delayed cement compositions may set to form a hardened mass in a time
period ranging
between any of and/or including any of about 1 hour, about 2 hours, about 4
hours, about 6
hours, about 8 hours, about 10 hours, or about 12 hours.
[0029] in some embodiments, the set-delayed cement compositions may set to
have a
desirable compressive strength after activation. Compressive strength is
generally the capacity
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of a material or structure to withstand axially directed pushing forces. The
compressive
strength may be measured at a specified time after the set-delayed cement
composition has
been activated and the resultant composition is maintained under specified
temperature and
pressure conditions. Compressive strength can be measured by either
destructive or non-
destructive methods. The destructive method physically tests the strength of
treatment fluid
samples at various points in time by crushing the samples in a compression-
testing machine.
The compressive strength is calculated from the failure load divided by the
cross-sectional
area resisting the load and is reported in units of pound-force per square
inch (psi). Non-
destructive methods may employ a UCA"' ultrasonic cement analyzer, available
from Fann
Instrument Company, Houston, TX. Compressive strength values may be determined
in
accordance with API RP 1013-2, Recommended Practice for Testing Well Cements,
First
Edition, July 2005.
[0030] By way of example, the set-delayed cement compositions may develop a 24-
hour compressive strength in the range of from about 50 psi to about 5000 psi,
alternatively,
from about 100 psi to about 4500 psi, or alternatively from about 500 psi to
about 4000 psi. In
some embodiments, the set-delayed cement compositions may develop a
compressive strength
in 24 hours of at least about 50 psi, at least about 100 psi, at least about
500 psi, or more. In
some embodiments, the compressive strength values may be determined using
destructive or
non-destructive methods at a temperature ranging from 100 F to 200 F.
[00311 In some embodiments, the set-delayed cement compositions may have
desirable thickening times after activation. Thickening time typically refers
to the time a fluid,
such as a set-delayed cement composition, remains in a fluid state capable of
being pumped.
A number of different laboratory techniques may be used to measure thickening
time. A
pressurized consistometer, operated in accordance with the procedure set forth
in the
aforementioned API RP Practice 10B-2, may be used to measure whether a fluid
is in a
pumpable fluid state. The thickening time may be the time for the treatment
fluid to reach 70
Bc and may be reported as the time to reach 70 Bc. In some embodiments, the
cement
compositions may have a thickening time of greater than about 1 hour,
alternatively, greater
than about 2 hours, alternatively greater than about 5 hours at 3,000 psi and
temperatures in a
range of from about 50 F to about 400 F, alternatively, in a range of from
about 80 F to about
250 F, and alternatively at a temperature of about 140 F.
[0032] Embodiments may include the addition of a cement set activator to the
set-
delayed cement compositions. Examples of suitable cement set activators
include, but are not
limited to: zeolites, amines such as triethanolamine, diethanolamine;
silicates such as sodium
silicate; zinc formate; calcium acetate; Groups IA and IIA hydroxides such as
sodium
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hydroxide, magnesium hydroxide, and calcium hydroxide; monovalent salts such
as sodium
chloride; divalent salts such as calcium chloride; nanosilica (i.e., silica
having a particle size
of less than or equal to about 100 nanometers); polyphosphates; and
combinations thereof. In
some embodiments, a combination of the polyphosphate and a monovalent salt may
be used
for activation. The monovalent salt may be any salt that dissociates to form a
monovalent
cation, such as sodium and potassium salts. Specific examples of suitable
monovalent salts
include potassium sulfate, and sodium sulfate. A variety of different
polyphosphates may be
used in combination with the monovalent salt for activation of the set-delayed
cement
compositions, including polymeric metaphosphate salts, phosphate salts, and
combinations
thereof. Specific examples of polymeric metaphosphate salts that may be used
include sodium
hexametaphosphate, sodium trimetaphosphate, sodium tetrametaphosphate, sodium
pentametaphosphate, sodium heptametaphosphate, sodium octametaphosphate, and
combinations thereof. A specific example of a suitable cement set activator
comprises a
combination of sodium sulfate and sodium hexametaphosphate. In particular
embodiments,
the activator may be provided and added to the set-delayed cement composition
as a liquid
additive, for example, a liquid additive comprising a monovalent salt, a
polyphosphate, and
optionally a dispersant.
[0033] Some embodiments may include a cement set activator comprising a
combination of a monovalent salt and a polyphosphate. The monovalent salt and
the
polyphosphate may be combined prior to addition to the set-delayed cement
composition or
may be separately added to the set-delayed cement composition. The monovalent
salt may be
any salt that dissociates to form a monovalent cation, such as sodium and
potassium salts.
Specific examples of suitable monovalent salts include potassium sulfate and
sodium sulfate.
A variety of different polyphosphates may be used in combination with the
monovalent salt
for activation of the set-delayed cement compositions, including polymeric
metaphosphate
salts, phosphate salts, and combinations thereof, for example. Specific
examples of polymeric
metaphosphate salts that may be used include sodium hexametaphosphate, sodium
trimetaphosphate, sodium tetrametaphosphate, sodium pentametaphosphate, sodium
heptametaphosphate, sodium octametaphosphate, and combinations thereof A
specific
example of a suitable cement set activator comprises a combination of sodium
sulfate and
sodium hexametaphosphate. Interestingly, sodium hexametaphosphate is also
known in the art
to be a strong retarder of Portland cements. Because of the unique chemistry
of
polyphosphates, polyphosphates may be used as a cement set activator for
embodiments of the
set-delayed cement compositions disclosed herein. The ratio of the monovalent
salt to the
polyphosphate may range, for example, from about 5:1 to about 1:25 or from
about 1:1 to
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about 1:10. Embodiments of the cement set activator may comprise the
monovalent salt and
the polyphosphate salt in a ratio (monovalent salt to polyphosphate) ranging
between any of
and/or including any of about 5:1,2:1, about 1:1, about 1:2, about 1:5, about
1:10, about 1:20,
or about 1:25.
[0034] In some embodiments, the combination of the monovalent salt and the
polyphosphate may be mixed with a dispersant and water to form a liquid
additive for
activation of a set-delayed cement composition. Examples of suitable
dispersants include,
without limitation, the previously described dispersants, such as sulfonated-
formaldehyde-
based dispersants and polycarboxylated ether dispersants. One example of a
commercial
dispersant is CFR-r dispersant, available from Halliburton Energy Services,
Inc. One
example of a suitable polycarboxylated ether dispersant is Liquiment 514L or
5581F
= dispersants, available from BASF Corporation, Houston, Texas.
[0035] The liquid additive may function as a cement set activator. As
discussed above,
a cement set activator may also accelerate the setting of the set-delayed or
heavily retarded
cement. The use of a liquid additive to accelerate a set-delayed OT heavily
retarded cement is
dependent upon the compositional makeup of the liquid additive as well as the
compositional
makeup of the set-delayed or heavily retarded cement. With the benefit of this
disclosure, one
of ordinary skill in the art should be able to formulate a liquid additive to
activate and/or
accelerate a set-delayed or heavily retarded cement composition.
[0036] The cement set activator may be added to embodiments of the set-delayed
cement composition in an amount sufficient to induce the set-delayed cement
composition to
set into a hardened mass. In certain embodiments, the cement set activator may
be added to
the set-delayed cement composition in an amount in the range of about 0.1% to
about 20% by
weight of the pumice. In specific embodiments, the cement set activator may be
present in an
amount ranging between any of and/or including any of about 0.1%, about 1%,
about 5%,
about 10%, about 15%, or about 20% by weight of the pumice. One of ordinary
skill in the art,
with the benefit of this disclosure, will recognize the appropriate amount of
cement set
activator to include for a chosen application.
[0037] As will be appreciated by those of ordinary skill in the art,
embodiments of the
set-delayed cement compositions may be used in a variety of subterranean
operations,
including primary and remedial cementing. In some embodiments, a set-delayed
cement
composition may be provided that comprises water, pumice, hydrated lime, a set
retarder, and
optionally a dispersant. The set-delayed cement composition may be introduced
into a
subterranean formation and allowed to set therein. As used herein, introducing
the set-delayed
cement composition into a subterranean formation includes introduction into
any portion of
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the subterranean formation, including, without limitation, into a wellbore
drilled into the
subterranean formation, into a near wellbore region surrounding the wellbore,
or into both.
Embodiments may further include activation of the set-delayed cement
composition. The
activation of the set-delayed cement composition may comprise, for example,
the addition of
a cement set activator to the set-delayed cement composition.
[0038] In some embodiments, a set-delayed cement composition may be provided
that
comprises water, pumice, hydrated lime, a set retarder, and optionally a
dispersant. The set-
delayed cement composition may be stored, for example, in a vessel or other
suitable container.
The set-delayed cement composition may be permitted to remain in storage for a
desired time
30 period. For example, the set-delayed cement composition may remain in
storage for a time
period of about 1 day or longer. For example, the set-delayed cement
composition may remain
in storage for a time period of about 1 day, about 2 days, about 5 days, about
7 days, about 10
days, about 20 days, about 30 days, about 40 days, about 50 days, about 60
days, or longer. In
some embodiments, the set-delayed cement composition may remain in storage for
a time
period in a range of from about 1 day to about 7 days or longer. Thereafter,
the set-delayed
cement composition may be activated, for example, by addition of a cement set
activator,
introduced into a subterranean formation, and allowed to set therein.
[0039] In primary cementing embodiments, for example, embodiments of the set-
delayed cement composition may be introduced into an annular space between a
conduit
located in a wellbore and the walls of a wellbore (and/or a larger conduit in
the wellbore),
wherein the wellbore penetrates the subterranean formation. The set-delayed
cement
composition may be allowed to set in the annular space to form an annular
sheath of hardened
cement. The set-delayed cement composition may form a barrier that prevents
the migration
of fluids in the wellbore. The set-delayed cement composition may also, for
example, support
the conduit in the wellbore.
[0040] In remedial cementing embodiments, a set-delayed cement composition may
be used, for example, in squeeze-cementing operations or in the placement of
cement plugs.
By way of example, the set-delayed composition may be placed in a wellbore to
plug an
opening (e.g., a void or crack) in the formation, in a gravel pack, in the
conduit, in the cement
sheath, and/or between the cement sheath and the conduit (e.g., a
microannulus).
[0041] As will be appreciated by those of ordinary skill in the art,
embodiments of the
set-delayed cement compositions may be used as plugging compositions for
forming a seal in
plug-and-abandon operations. Embodiments of the set-delayed cement plugging
compositions
may be used onshore or offshore. Set -delayed cement plugging compositions may
be preferred
over traditional plugging compositions in certain applications (e.g., offshore
applications)
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because a set-delayed cement plugging composition may require less equipment
and personnel
to use, which may be particularly advantageous in operations where space is
limited. An
example of a method for plugging and abandoning a well comprises placing a
plugging
composition in a selected plug location in a wellbore and allowing the
plugging composition
to set to form a plug. The plug location may be selected so that the wellbore
can be sealed off
for abandonment. For example, the plug location may be selected so that a
selected interval
of the wellbore may be sealed. In an embodiment, the selected location may be
adjacent to a
hydrocarbon-containing formation or a water-containing formation. In an
embodiment, the
plugging and abandoning operation may include the formation of two or more
plugs in the
wellbore. For example, a method may further include the placement of a second
plugging
composition in another selected plug location in the wellbore. Additionally,
the plugging
technique may comprise any such pump that is sufficient for a given
application. Moreover
certain applications may comprise wireline operated dump bailers.
[0042] Embodiments comprise the formation of a cement plug in a wellbore with
low
permeability. Low permeability is defined as a plug with a permeability of
less than about 0.1
millidarcy. A cement plug with low permeability prevents the migration of
fluids and gas.
[0043] An embodiment comprises A method of plugging a wellbore, comprising:
providing a set-delayed cement composition comprising pumice, hydrated lime, a
cement set
retarder, and water; activating the set-delayed cement composition to produce
an activated set-
delayed cement composition; introducing the activated set-delayed cement
composition into
the wellbore; and allowing the activated set-delayed cement composition to
form a plug in the
wellbore that has a permeability of less than 0.1 millidarcy. The set-delayed
cement
composition may comprise one or more of the additional additives described
herein.
[0044] An embodiment comprises a method of plugging a wellbore, comprising:
providing a cement composition comprising water, pumice, hydrated lime, a
dispersant, a
viscosifier, a weighting agent, and a cement set retarder; storing the cement
composition for a
period of about I day or longer; activating the cement composition to produce
an activated
cement composition; introducing the activated cement composition into the
wellbore; and
allowing the cement composition to form a plug in the wellbore that has a
permeability of less
than 0.1 millidarcy. The cement composition may comprise one or more of the
additional
additives described herein.
[0045] An embodiment comprises a set-delayed cementing system for plugging a
wellbore comprising: a set-delayed cement composition comprising: water,
pumice, hydrated
lime, and a cement set retarder; a cement set activator for activating the set-
delayed cement
composition, mixing equipment for mixing the set-delayed cement composition
and the
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cement set activator to produce an activated set-delayed cement composition,
and equipment
for delivering the activated set-delayed cement composition to a wellbore. The
set-delayed
cement composition may further comprise one or more of the additional
additives described
herein.
[00461 Referring now to FIG. 1, the preparation of a set-delayed cement
composition
in accordance with example embodiments will now be described for applications
in which the
set-delayed cement composition is pumped downbole. FIG. 1 illustrates a system
2 for the
preparation of a set-delayed cement composition and subsequent delivery of the
composition
to a wellbore in accordance with certain embodiments. As shown, the set-
delayed cement
composition may be mixed in mixing equipment 4, such as a jet mixer, re-
circulating mixer,
or a batch mixer, for example, and then pumped via pumping equipment 6 to the
wellbore. In
some embodiments, the mixing equipment 4 and the pumping equipment 6 may be
disposed
on one or more cement trucks as will be apparent to those of ordinary skill in
the art. In some
embodiments, a jet mixer may be used, for example, to continuously mix the
lime/settable
material with the water as it is being pumped to the wellbore. In set-delayed
embodiments, a
re-circulating mixer and/or a batch mixer may be used to mix the set-delayed
cement
composition, and the activator may be added to the mixer as a powder prior to
pumping the
cement composition downhole.
[0047] In offshore operations where rig space may be limited, the set-delayed
cement
composition may be prepared onshore and delivered to the well site in fit-for-
purpose delivery
tanks. In some embodiments the mixing equipment may be the same as described
in the
description of FIG. 1 above.
[0048] Referring now to FIG. 2A, the delivery system for some embodiments may
includea liquid storage vessel 10 with a detached circulating pump 12,
additive skid 14, and
additive tank 16. The detached circulating pump 12 may be used to re-circulate
the set-delayed
cement composition in the liquid storage vessel 10. The additive skid 14
(which may include
a pump, for example) may be used to deliver additives from additive tank 16 to
the set-delayed
cement composition in the liquid storage vessel 10.
[0049] Referring now to FIG. 2B, the delivery system for some embodiments may
include a self-contained delivery system 18 which comprises a storage tank 20,
circulating
pump 22, liquid additive system 24, and additive tank 26. The circulating pump
22 may be
used to re-circulate the set-delayed cement composition in the storage tank
20. The liquid
additive system 24 (which may include a pump, for example) may be used to
deliver additives
from additive tank 26 to the set-delayed cement composition in the storage
tank 20.
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10050] FIG. 3 illustrates surface equipment 28, which may be used in the
placement
of a set-delayed cement composition in accordance with certain embodiments. It
should be
noted that while FIG. 3 generally depicts a land-based operation, those
skilled in the art will
readily recognize that the principles described herein are equally applicable
to subsea
operations that employ floating or sea-based platforms and rigs, without
departing from the
scope of the disclosure. As illustrated by FIG. 3, the surface equipment 28
may include a
cementing unit 30, which may include one or more cement trucks. The cementing
unit 30 may
include mixing equipment 4 and pumping equipment 6 (e.g., FIG. 1) as will be
apparent to
those of ordinary skill in the art. The cementing unit 30 may pump a set-
delayed cement
composition 32 through a feed pipe 34 and to a tubing connection 36 which
conveys the set-
delayed cement composition 32 downhole.
[0051] An example embodiment for placing a set-delayed cement composition
across
a set of open perforations and/or a casing leak will be described with
reference to FIG. 4. The
set-delayed cement composition 32 may be placed across the perforations and/or
easing leak
38 in accordance with example embodiments. As illustrated, a cement retainer
or squeeze
packer 40 may be ran to a depth above the open perforations and/or casing leak
38 and set on
either wireline or tubing 42. While wellbore 44 is shown extending generally
vertically into
the subterranean formation 46, the principles described herein are also
applicable to wellbores
that extend at an angle through the subterranean formation 46, such as
horizontal and slanted
wellbores. As illustrated, the wellbore 44 comprises walls 48. In the
illustrated embodiment,
a casing 50 has been inserted into the wellbore 44. The casing 50 may be
cemented to the walls
48 of the wellbore 44 by cement sheath 52.
[0052] With continued reference to FIG. 4, the set-delayed cement composition
32
may be pumped down the interior of the tubing 42. The set-delayed cement
composition 32
may be allowed to flow down the interior of the tubing 42 through the cement
retainer or
squeeze packer 40 at the bottom of the tubing 42 and down across and into the
open
perforations and/or casing leak 38. The set-delayed cement composition 32 may
be allowed to
set inside the casing 50, for example, to form a plug that seals the open
perforations and/or
casing leak 38 in the wellbore 44. While not illustrated, other techniques may
also be utilized
for introduction of the set-delayed cement composition 32. By way of example,
open ended
tubing and/or drill pipe may be used to place the set-delayed cement
composition 32 across
the open perforations and/or casing leak 38.
[0053] FIG. 5 illustrates an additional embodiment comprising the placement of
the
set-delayed cement composition 32 within an openhole section 54 to isolate the
formation 46
below. FIG. 5 shows the set-delayed cement composition 32 inside the openhole
section 54,
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but the set-delayed cement composition 32 may at times enter into the casing
50 above. As
with the embodiment described in FIG. 4, the set-delayed cement composition 32
may be
pumped through the drillpipe and/or tubing 42 and a cement retainer or squeeze
packer 40.1n
some embodiments the drillpipe and/or tubing 42 may be open ended.
[0054] FIG. 6 illustrates an embodiment comprising the placement of a cement
plug
across the top of well equipment, such as a fish and/or casing stub 56. The
set-delayed cement
composition 32 may be spotted through an open ended drillpipe or tubing 42.
The bottom of
the set-delayed cement composition 32 may be placed at a predetermined
distance into the
casing 50 and back up into the openhole section 54 above the casing stub 56.
[0055] FIG. 7 illustrates an embodiment comprising the setting of a cementing
plug
utilizing a wireline 58 deployed dump bailer 60. In this embodiment, the set-
delayed cement
composition 32 may be placed above either a fish or bridge plug 62. The set-
delayed cement
composition 32 may be pre-mixed and placed inside the dump bailer 60. The dump
bailer 60
may then be ran to the necessary depth via wireline 58 and either dumped via a
remotely
operated valve located at the bottom of the dump bailer 60 or a class of
ceramic disk may be
broken by bumping it against the bottom of the hole. Once the set-delayed
cement composition
32 is removed from the dump bailer 60, the dump bailer 60 may be pulled back
to the surface
and additional runs may be performed if necessary.
[0056] FIG. 8 illustrates an embodiment of a standard surface rig up for a
dump bailer
60 operation. As illustrated, a wireline truck 64 or skid may be utilized to
lower the dump
bailer 60 through the tubing connection 36 via either electric wireline 58 or
slickline.
[0057] In alternative embodiments, the set-delayed cement composition may be
placed utilizing coiled tubing as the means of conveyance instead of sectioned
tubing. This
means of conveyance can be utilized to perform any of the job types as
described above.
[0058] The exemplary set-delayed cement compositions disclosed herein may
directly
or indirectly affect one or more components or pieces of equipment associated
with the
preparation, delivery, recapture, recycling, reuse, and/or disposal of the
disclosed set-delayed
cement compositions. For example, the disclosed set-delayed cement
compositions may
directly or indirectly affect one or more mixers, related mixing equipment,
mud pits, storage
facilities or units, composition separators, heat exchangers, sensors, gauges,
pumps,
compressors, and the like used generate, store, monitor, regulate, and/or
recondition the
exemplary set-delayed cement compositions. The disclosed set-delayed cement
compositions
may also directly or indirectly affect any transport or delivery equipment
used to convey the
set-delayed cement compositions to a well site or downhole such as, for
example, any transport
vessels, conduits, pipelines, trucks, tubulars, and/or pipes used to
compositionally move the
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set-delayed cement compositions from one location to another, any pumps,
compressors, or
motors (e.g., topside or downhole) used to drive the set-delayed cement
compositions into
motion, any valves or related joints used to regulate the pressure or flow
rate of the set-delayed
cement compositions, and any sensors (i.e., pressure and temperature), gauges,
and/or
combinations thereof, and the like. The disclosed set-delayed cement
compositions may also
directly or indirectly affect the various downhole equipment and tools that
may come into
contact with the set-delayed cement compositions such as, but not limited to,
wellbore casing,
wellbore liner, completion string, insert strings, drill string, coiled
tubing, slickline, wireline,
drill pipe, drill collars, mud motors, downhole motors and/or pumps, cement
pumps, surface-
mounted motors and/or pumps, centralizers, turbolizers, scratchers, floats
(e.g., shoes, collars,
valves, etc.), logging tools and related telemetry equipment, actuators (e.g.,
electromechanical
devices, hydromechanical devices, etc.), sliding sleeves, production sleeves,
plugs, screens,
filters, flow control devices (e.g., inflow control devices, autonomous inflow
control devices,
outflow control devices, etc.), couplings (e.g., electro-hydraulic wet
connect, dry connect,
inductive coupler, etc.), control lines (e.g., electrical, fiber optic,
hydraulic, etc.), surveillance
lines, drill bits and reamers, sensors or distributed sensors, downhole heat
exchangers, valves
and corresponding actuation devices, tool seals, packers, cement plugs, bridge
plugs, and other
wellbore isolation devices, or components, and the like.
[0059] To facilitate a better understanding of the present embodiments, the
following
examples of certain aspects of some embodiments are given. In no way should
the following
examples be read to limit, or define, the entire scope of the embodiments.
EXAMPLES
Example 1
[00601 The following example describes a set-delayed cement plugging
composition
comprising the following components:
Table 1
Compositional Makeup
Component Amount Unit*
Water 60 % bwoP
Pumice 100 % bwoP
Lime 20 % bwoP
Weighting Agent 2 % bwoP -
Retarder 0.06 Gallsk
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Dispersant 0.6 % bwoP
Viscositier 0.035 % bwoP
*% bwoP = by weight of pumice; Gal/sk = gallons per 46 lb. sack of pumice
[00611 The composition had a density of 13.6 pounds per gallon. The weighting
agent
was Micromax FF weight additive available from Halliburton Energy Services,
Inc.,
Houston, TX. The cement retarder was Micro Matrix's' Cement Retarder available
from
Halliburton Energy Services, Inc., Houston, TX. The dispersant was Liquiment
5581F
dispersant available from BASF, Florham Park, New Jersey. The viscosifier was
SA-1015.`"
suspending agent available from Halliburton Energy Services, Inc., Houston,
TX. After
preparation, the rheological properties of the sample was measured using a
Model 35A Fann
Viscometer and a No. 2 spring with a Fann Yield Stress Adapter (FYSA), in
accordance with
the procedure set forth in API RP Practice 10B-2, Recommended Practice for
Testing Well
Cements. The results are presented in Table 2 below. The apparent viscosities
were calculated
using the torque dial readings and the calibrated factors that convert RPM to
shear rate and
dial readings to shear stress. The 3D and 6D Decay readings were dial readings
15 seconds
after stopping the Model 35A Fann Viscometer after it was operating at 3 RPM
and 6 RPM
respectively.
Table 2
Apparent Viscosities (cP) and Decay Readings
RPM Decay
Age 3 6 30 60 100 200
300 600 3D 6D
Day
2 19947 11560 2720 1949
1102 802 703 573 28 30
Day
3 29467 14733 3309 1904
1224 816 680 476 40 42
Day
3* 15867 9067 2221 1269
870 612 526 408 25 42
Day
7 20627 10540 2312 1383 986 673 576 471 8 6
Day
8 24933 12467 2629 1519
1047 639 539 444 12 10
Day
10 22213 10880 2267 1292 870 605 517 424 8 7
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Day
11 16230 8387 1995 1179 816 578 485 422 6 6
Day
12 13600 7027 1768 1043 721 503 440 408 5 5
Day
13 12240 6327 1723 1043 830 551 453 408 3 4
Day
14 16320 8387 1904 1111 789 578 503 453 6 5
Day
15 9520 4760 1133 680 476 367 340 311 3 3
Day
16 9520 5213 1405 884 694 530 481 390 3 2
Day
17 9973 5213 1405 839 612 476 417 385 3 3
Day
18 7523 4307 1224 771 598 456 413 413 I 2
Day
20 8160 4307 1179 748 598 456 417 383 2 2
Day
21 8160 4533 1224 793 612 462 413 374 3 2
Day
22 10427 5213 1269 839 653 503 458 408 4 4
Day
24 8613 4760 1315 839 612 483 422 381 3 3
Day
27 9067 4533 1451 907 666 510 449 397 4 4
Day
31 11787 5893 1451 907 653 469 417 381 6 5
*After addition of 26 gallons of water, lowering the slurry density from 13.8
ppg to 13.6
PPg=
[0062] Table 3 tabulates the apparent viscosity of the composition at 100 rpm
versus
the composition age. The results are presented below.
Table 3
Apparent Viscosity at 100 RPM
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Age Apparent Viscosity
(Centipoise)
Day 2 1102
Day 3 1224
Day 3* 870
Day 7 986
Day 8 1047
Day 10 870
Day 11 816
Day 12 721
Day 13 830
Day 14 789
Day 15 476
Day 16 694
Day 17 612
Day 18 598
Day 20 598
Day 21 612
Day 22 653
Day 24 612
Day 27 666
Day 28 639
Day 29 639
Day 30 666
Day 31 653
*After addition of 26 gallons of water, lowering the slurry density from 13.8
ppg to 13.6
PPg=
[0063] The data shows a gradual decrease in viscosity from day 2 through day
14,
after which time the viscosity of the composition begins to stabilize around
an average of 625
cP through day 31. This decline in apparent viscosity in the early going and
subsequent
stabilization may be advantageous for storing, mixing, and pumping the set-
delayed cement
composition and presents a distinctive feature in that it avoids the need for
post-prep treatments
such as additional dispersant or water to mitigate increasing viscosity.
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[0064] The destructive 24-hour compressive strength of the sample was measured
after the addition of a 2% active liquid additive cement set activator
comprising sodium sulfate,
sodium hexametaphosphate, a polycarboxylated ether dispersant, and water. The
destructive
compressive strength was measured by allowing the samples to cure in a 2" by
4" plastic
cylinder that was placed in a water bath at 134 F to form set cylinders.
Immediately after
removal from the water bath, destructive compressive strengths were determined
using a
mechanical press in accordance with API RP I OB-2, Recommended Practice for
Testing Well
Cements. The results of this test are set forth below in Table 4. The reported
compressive
strengths are an average for two cylinders of each sample.
Table 4
Compressive Strength
24-Hr. Compressive Strength at 134 F (psi)
Activator Day 0 Day I Day 2 Day 7 Day 14 Day 21
Day 28 Day 35
2% Liquid Additive 108 381 552 485 705 513 899 440
[0065] The results show that the 24-hour strength development becomes more
rapid
as the slurry ages from the initial preparation, and then stabilizes
throughout the remainder of
the time.
[0066] The destructive 24-hour compressive strength of the sample was further
measured at the 21-day mark after further curing the sample for I day, 3 days,
or 7 days. The
sample was activated either with the addition of a 2% active liquid additive
cement set
activator comprising sodium sulfate, sodium hexametaphosphate, a
polycarboxylated ether
dispersant, and water; or a 10% CaC12 solution. The destructive compressive
strength was
measured by allowing the samples to cure in a 2" by 4" plastic cylinder that
was placed in a
water bath at 134 F (140 F for the 7 day sample) to form set cylinders.
Immediately after
removal from the water bath, destructive compressive strengths were determined
using a
mechanical press in accordance with API RP 10B-2, Recommended Practice for
Testing Well
Cements. The results of this test are set forth below in Table 5. The reported
compressive
strengths are an average for two cylinders of each sample.
Table 5
Compressive Strength
Compressive Strength at Day 21 (psi)
Activator Cured 1 Day Cured 3 Days Cured 7 Days
2% Liquid Additive 513 1678 2245
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10% CaCl2 35 961 1450
[0067] The results show that, as expected, the compressive strengths increase
alongside increasing curing time.
Example 2
[0068] Table 6 below provides two other formulations of set-delayed cement
plugging
compositions and their corresponding 30-day compressive strengths (psi) and 5-
day
permeability (md) measurements. Composition A had a density of 13.5 pounds per
gallon.
Composition B had a density of 16.3 pounds per gallon. The cement retarder was
Micro
Matrix Cement Retarder available from I lalliburton Energy Services, Inc.,
Houston, TX. The
dispersant was Liquiment 5581F dispersant available from BASF, Florham Park,
New Jersey.
The viscosifier was V_Mar 3 concrete rheology-modifying admixture available
from W. R.
Grace & Co., Cambridge, MA. The weighting agent was Micromax FF weight
additive
available from Halliburton Energy Services, Inc., Houston, TX.
Sample A Sample B
Material Amount Unit Material Amount Unit
Water 60 % bwoP Water 49 % bwoP
Pumice 100 % bwoP Pumice 100 % bwoP
Lime 20 % bwoP Lime 20 % bwoP
Retarder 0.06 Gal/sk Retarder 0.06 Gal/sk
Dispersant 0.6 % bwoP Dispersant 1.1 % bwoP
Viscosifier 0.05 Gal/sk Viscosifier 0.05 Gal/sk
Weighting 45 % bwoP
Agent
30-Day Compressive 3170 30-Day Compressive 4430
Strength (psi) Strength (psi)
5-Day Permeability (ind) 0.00056 5-Day Permeability (md) 0.00030
[0069] Both samples had high long-term compressive strengths (>3000 psi) and
low
permeability results (< 0.001 md). These results indicate that the set-delayed
cement
compositions are plugging compositions that are suitable for sealing off wells
and maintain
seal integrity over the course of well abandonment, i.e. preventing the
passage of fluids.
[0070] It should be understood that the compositions and methods are described
in
terms of "comprising," "containing," or "including" various components or
steps, the
22
compositions and methods can also "consist essentially of' or "consist of' the
various
components and steps. Moreover, the indefinite articles "a" or "an," as used
in the claims, are
defined herein to mean one or more than one of the element that it introduces.
[0071] For the sake of brevity, only certain ranges are explicitly disclosed
herein.
However, ranges from any lower limit may be combined with any upper limit to
recite a range
not explicitly recited, as well as, ranges from any lower limit may be
combined with any other
lower limit to recite a range not explicitly recited, in the same way, ranges
from any upper limit
may be combined with any other upper limit to recite a range not explicitly
recited. Additionally,
whenever a numerical range with a lower limit and an upper limit is disclosed,
any number and
any included range falling within the range are specifically disclosed. In
particular, every range
of values (of the form, -from about a to about b," or, equivalently, "from
approximately a to
or, equivalently, "from approximately a-b") disclosed herein is to be
understood to set forth
every number and range encompassed within the broader range of values even if
not explicitly
recited. Thus, every point or individual value may serve as its own lower or
upper limit
combined with any other point or individual value or any other lower or upper
limit, to recite a
range not explicitly recited.
[0072] Therefore, the present embodiments are well adapted to attain the ends
and
advantages mentioned as well as those that are inherent therein. The
particular embodiments
disclosed above are illustrative only, as the present embodiments may be
modified and practiced
in different but equivalent manners apparent to those skilled in the art
having the benefit of the
teachings herein. Although individual embodiments are discussed, all
combinations of each
embodiment are contemplated and covered by the disclosure. Furthermore, no
limitations are
intended to the details of construction or design herein shown, other than as
described in the
claims below. Also, the terms in the claims have their plain, ordinary meaning
unless otherwise
explicitly and clearly defined by the patentee. It is therefore evident that
the particular
illustrative embodiments disclosed above may be altered or modified and all
such variations are
considered within the scope and spirit of the present disclosure. If there is
any conflict in the
usages of a word or term in this specification and one or more patent(s) or
other documents that
may be referred to herein, the definitions that are consistent with this
specification should be
adopted.
23
CA 2928206 2017-06-01
