SETTABLE COMPOSITIONS CONTAINING METAKAOLIN HAVING
REDUCED PORTLAND CEMENT CONTENT
BACKGROUND
[0001] The present invention relates to cementing operations, and more
specifically, to cementing operations in subterranean formations that contain corrosive
components.
[0002] Hydraulic cement compositions are commonly used in subterranean
operations, particularly completion and remedial operations. For example, hydraulic cement
compositions may be used in primary cementing operations whereby pipe strings, such as
casings and liners, are cemented in wellbores. Hydraulic cement compositions may also be
used in remedial cementing operations such as plugging highly permeable zones or fractures
in wellbores, plugging cracks and holes in pipe strings, and the like.
[0003] A variety of hydraulic cement compositions have been used in
conventional subterranean cementing operations with the most common cement
compositions comprising Portland cement. However, Portland cement has drawbacks in its
method of preparation, methods of implementation, and final set compositions. Portland
cement is generally prepared by heating a mixture of raw materials comprising calcium
oxide, silicon oxide, aluminum oxide, ferric oxide, and magnesium oxide in a kiln to
approximately 1500 °C. Thus, the energy requirements to produce Portland cement are
quite high, and heat loss during production can further cause actual energy requirements to
be even greater. In addition, Portland cement manufacturing process produces about 5% of
the total global anthropogenic C0 2. This makes for an expensive production method with a
high carbon footprint. The manufacturing process of Portland cements also has batch-tobatch
variations that may yield unpredictable results when applied in a wellbore.
[0004] In addition to manufacturing drawbacks, the implementation of Portland
cements in subterranean formations also has drawbacks. Salts, particularly multivalent salts,
often cause issues during the pumping and installation of a Portland cement. For example,
when exposed to magnesium or calcium salts, Portland cement slurries are known to rapidly
viscosity to a point that the cement is no longer pumpable. In subterranean formations,
magnesium and calcium salts may be encountered in brines, evaporite minerals, and salt
domes. To mitigate this effect, engineers may add scale inhibitors, chelating agents, or other
additives to a treatment fluid containing Portland cement. However, this method is typically
restricted because of very high material and installation costs.
[0005] Further, once the Portland cements are set within a wellbore, corrosive
components, like salts, carbonic acid, and hydrogen sulfide, found within some subterranean
formations may cause failure of Portland cement structure. As used herein, the term
"corrosive" refers to a substance that destroys or irreversibly damages another surface or
substance with which it comes into contact. For example, loss of metal due to chemical or
electrochemical reactions is a commonly known form of corrosion. Corrosion rates may
vary depending on the time, temperature, corrosive component, pH, and other physical and
chemical variable. For example as shown in the chemical reaction below, dissolved carbon
dioxide and carbonic acid can attack Portland cements by converting calcium hydroxide to
the more stable calcium carbonate and/or calcium bicarbonate. First, dissolved carbon
dioxide converts to carbonic acid thereby lowering the local pH. The rate of conversion
may depend on temperature, partial pressure of carbon dioxide, and salt concentration.
Second, carbonation of the Portland cement occurs which may cause (a) densification
leading to increased hardness and reduced permeability thereby decreasing C0 2 diffusion
and (b) volume expansion of up to 6%, which may lead to development of micro to macro
cracks in extreme cases. Both of these results may be due to an increase in mass (from
chemical consumption of C0 2) within the volume defined by the solid set cement matrix.
Finally, the long-term phenomenon of dissolution of CaC0 may occur when the cement is
surrounded by water containing dissolved C0 2 for extended periods of time. Dissolution of
CaC0 may increase porosity and/or permeability thereby decreasing overall mechanical
strength. Decreased cement integrity may lead to inefficient zonal isolation and in extreme
cases complete failure of the cement composition.
1) Formation of carbonic acid:
C0 2 + H 0 -» H2C0 3
2) Carbonation of Portlandite and/or cement hydrates:
Ca(OH) + ¾C0 3 - CaC0 + 2 H20
C-S-H and/or crystalline phases + H C0 - Si0 2 (gel) +CaC0 +H20
3) Dissolution of CaC0 (long-term effect):
CaC0 3 + H C0 3 -» Ca(HC0 )2
[0006] Carbon dioxide and/or carbonic acid corrosion may, through the above
mechanisms, lead to decreased strength of a Portland cement composition ultimately causing
cracking and failure of a subterranean cement structure. This corrosion may be of greater
concern depending on the characteristics of the subterranean cement structure. For example,
increased surface area and/or increased permeability of the cement structure to water, as
may be the case in a foamed cement structure, may dramatically increase the rate at which
the structure corrodes causing a shorter usable life.
[0007] By a similar mechanism, sulfuric acid may cause Portland cement
corrosion. Sulfuric acid corrosion may be magnified if the wellbore contains sulfate salts
and/or bacteria that metabolize hydrogen sulfide and/or sulfur to sulfuric acid.
[0008] Additionally, hydrogen sulfide may cause significant Portland cement
deterioration. Hydrogen sulfide in the presence of water converts to HS and/or S2 that
reacts with the calcium hydroxide and transition metal oxide containing components in
Portland cement to form calcium sulfide and transition metal sulfide. For example, iron
containing components, such as calcium ferroaluminate (C AF) (generally present from 8-
13% Portland cement), may react with hydrogen sulfide by the reaction:
C4AF or FexOy + H2S - FeS2 + ¾ (gas)
[0009] To mitigate the corrosive damage, engineers use other cementitious
compositions to replace at least some of the Portland cement in subterranean operations.
This can be effective for formation with moderate corrosive capacity. However, it would be
advantageous to have a cementitious composition essentially free of Portland cement for use
in subterranean formations with high corrosive capacity or compounding corrosive
components.
SUMMARY OF THE INVENTION
[0010] In a first aspect, the present invention provides a method of cementing, the
method comprising: providing a settable fluid that comprises an aqueous-based medium, a
lime composition, and a cementitious blend that comprises metakaolin particulates and
aluminosilicate particulates, wherein the cementitious blend is essentially free of Portland
cement; introducing the settable fluid into a wellbore penetrating a subterranean formation
that comprises a corrosive component; and allowing the settable fluid to set therein.
[0011] The corrosive component may be selected from the group consisting of an
acid; dissolved carbon dioxide; a monovalent salt; a multivalent salt; a sulfur containing
compound; a microorganism and a byproduct thereof; and any combination thereof. The
settable fluid may further comprise an additive selected from the group consisting of a set
retarder, a set accelerator, a viscosifier, a gas, a surfactant, a fluid loss control additive, a
suspending aid, a mechanical properties modifier, a density modifier, a gas migration control
aid, and any combination thereof. The metakaolin particulates may comprise high-reactive
metakaolin particulates. The metakaolin particulates may be present in the settable fluid at
about 5% to about 85% by weight of total cementitious blend. At least some of the
aluminosilicate particulates may be selected from the group consisting of a Class F fly ash
particulate, a Class C fly ash particulate, a cement kiln dust particulate, a biowaste ash
particulate, a zeolite particulate, a slag particulate, and any combination thereof. The
aluminosilicate particulates may be present in the settable fluid at about 15% to about 95%
by weight of total cementitious blend. The lime composition may be present in the settable
fluid in an amount of about 5% to about 50% by weight of total cementitious blend. The
settable fluid may be foamed. The settable fluid may be included in a treatment fluid
selected from the group consisting of a spotting fluid, a flush fluid, a spacer fluid, a cement
slurry, a squeeze fluid, a drilling fluid, and a consolidation fluid. The subterranean
formation may include a cementitious composition that was placed therein prior to
introducing the settable fluid into the wellbore. The subterranean formation may have a
bottom-hole temperature of about 30 °F (-1 °C) to about 230 °F (110 °C). The settable fluid
may have a thickening time of about 3 hours to about 5 days as measured by hightemperature
and high-pressure consistometer at a desired bottom hole circulating
temperature within the range of about 80 °F (27 °C) to about 650 °F (343 °C). The settable
fluid may have a density greater than about 13.5 pounds per gallon (1620 kg/m ). The
settable fluid may have a density less than about 13.5 pounds per gallon (1620 kg m3) . The
settable fluid may be provided as a drilling fluid, wherein said drilling fluid further comprises a
set retarder present at about 2% to about 15% by weight of cementitious blend and is
essentially free of Portland cement, and said drilling fluid may be used to drill at least a portion
of a wellbore penetrating the subterranean formation to introducing it into the formation.
[0012] In a second aspect, the present invention provides a method comprising:
providing a drilling fluid that comprises an aqueous-based medium, a lime composition, a
set retarder, and a cementitious blend that comprises metakaolin particulates and
aluminosilicate particulates, wherein the drilling fluid is essentially free of Portland cement,
and wherein the set retarder is present at about 2% to about 15% by weight of cementitious
blend; and drilling at least a portion of a wellbore penetrating a subterranean formation with
the drilling fluid.
[0013] The drilling fluid may not set for at least about 72 hours after introduction
into the wellbore. The drilling fluid may further comprise an additive selected from the
group consisting of a set retarder, a set accelerator, a viscosifier, a gas, a surfactant, a fluid
loss control additive, a suspending aid, a mechanical properties modifier, a density modifier,
a gas migration control aid, and any combination thereof. The portion of the wellbore being
drilled may contain a corrosive component selected from the group consisting of carbonic
acid; dissolved carbon dioxide; a monovalent salt; a multivalent salt; sulfur containing
compounds; and any combination thereof.
[0014] In a third aspect, the present invention provides a settable fluid comprising: an
aqueous-based medium; a cementitious blend comprising: metakaolin particulates at a
concentration of about 5% to about 85% by weight of the cementitious blend and a fly ash at
a concentration of about 15% to about 95% by weight of the cementitious blend; and a lime
composition at a concentration of about 5% to about 25% by weight of the cementitious
blend, wherein the settable fluid does not include a Portland cement.
[0015] The settable fluid may further comprise an additive selected from the group
consisting of a set retarder, a set accelerator, a viscosifier, a gas, a surfactant, a fluid loss
control additive, a suspending aid, a mechanical properties modifier, a density modifier, a
gas migration control aid, and any combination thereof. The metakaolin particulates may
comprise high-reactive metakaolin particulates. The settable fluid may be foamed. The
settable fluid may be included in a treatment fluid selected from the group consisting of a
spotting fluid, a flush fluid, a spacer fluid, a cement slurry, a squeeze fluid, a drilling fluid,
and a consolidation fluid. The settable fluid may have a density greater than about 13.5
pounds per gallon (1620 kg/m3). The settable fluid may have a density less than about 13.5
pounds per gallon (1620 kg/m3) . The settable fluid may be provided as a drilling fluid,
wherein said drilling fluid further comprises a set retarder present at about 2% to about 15% by
weight of cementitious blend and is essentially free of Portland cement.
[0016] In a fourth aspect, the present invention provides a settable fluid comprising:
an aqueous-based medium; a cementitious blend comprising: metakaolin particulates at a
concentration of about 5% to about 85% by weight of the cementitious blend and a fly ash at
a concentration of about 15% to about 95% by weight of the cementitious blend; and a lime
composition at a concentration of about 5% to about 25% by weight of the cementitious
blend, wherein the settable fluid is essentially free of Portland cement.
[00171 The settable fluid may further comprise an additive selected from the group
consisting of a set retarder, a set accelerator, a viscosifier, a gas, a surfactant, a fluid loss
control additive, a suspending aid, a mechanical properties modifier, a density modifier, a
gas migration control aid, and any combination thereof. The metakaolin particulates may
comprise high-reactive metakaolin particulates. The settable fluid may be foamed. The
settable fluid may be included in a treatment fluid selected from the group consisting of a
spotting fluid, a flush fluid, a spacer fluid, a cement slurry, a squeeze fluid, a drilling fluid,
and a consolidation fluid. The settable fluid may have a density greater than about 13.5
pounds per gallon (1620 kg/m 3) . The settable fluid may have a density less than about 13.5
pounds per gallon (1620 kg/m3) . The settable fluid may be provided as a drilling fluid,
wherein said drilling fluid further comprises a set retarder present at about 2% to about 15% by
weight of cementitious blend and is essentially free of Portland cement.
[0018] The present invention relates to cementing operations, and more
specifically, to cementing operations in subterranean formations that contain corrosive
components.
[0019] In one embodiment, the present invention provides a method comprising:
providing a settable fluid that comprises an aqueous-based medium, a lime composition, and
a cementitious blend that comprises metakaolin particulates and aluminosilicate particulates,
wherein the cementitious blend is essentially free of Portland cement; introducing the
settable fluid into a wellbore penetrating a subterranean formation that comprises a corrosive
component; and allowing the settable fluid to set therein.
[0020] In one embodiment, the present invention provides a method comprising:
providing a drilling fluid that comprises an aqueous-based medium, a lime composition, a
set retarder, and a cementitious blend that comprises metakaolin particulates and
aluminosilicate particulates, wherein the drilling fluid is essentially free of Portland cement,
and wherein the set retarder is present at about 2% to about 10% by weight of settable blend;
and drilling at least a portion of a wellbore penetrating a subterranean formation with the
drilling fluid.
[0021] In one embodiment, the present invention provides a settable fluid
comprising: an aqueous-based medium; a settable blend comprising metakaolin particulates
at a concentration of about 5% to about 85% by weight of the settable blend and a fly ash at
a concentration of about 15% to about 95% by weight of the settable blend; and a lime
5 composition at a concentration of about 5% to about 25% by weight of the settable blend,
wherein the settable fluid does not include a Portland cement.
[0022] The features and advantages of the present invention will be readily
apparent to those skilled in the art upon a reading of the description of the preferred
embodiments that follows.
[0 BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The following figures are included to illustrate certain aspects of the
present invention, and should not be viewed as exclusive embodiments. The subject matter
disclosed is capable of considerable modification, alteration, and equivalents in form and
function, as will occur to those skilled in the art and having the benefit of this disclosure.
[5 [0024] Figure 1 depicts a cross-section of a drill rig and a wellbore for recovering
oil or gas from a subterranean formation penetrated by the wellbore.
[0025] Figure 2 depicts a cross-section of a wellbore penetrating a subterranean
formation, within which reside two hydrocarbon-bearing zones.
DETAILED DESCRIPTION
0 [0026] The present invention relates to cementing operations, and more
specifically, to cementing operations in subterranean formations that contain corrosive
components.
[0027] Of the many advantages of the present invention, the present invention
provides cementitious blends and settable fluids that are essentially Portland cement free.
5 The cementitious blends and settable fluids may be suitable for subterranean uses where
Portland cement compositions fall short. More specifically the cementitious blends and
settable fluids may be used in conjunction with brine-base treatment fluids, which may be
incompatible with Portland cement, and in subterranean formations with corrosive
components like salts, carbonic acid, and hydrogen sulfide that corrode set Portland cement
O compositions. The cementitious blends of the present invention include metakaolin. In
addition to the compatibility with brines and corrosive subterranean formations, metakaolin
production methods are less energy intensive than Portland cement production methods,
thereby decreasing the cost and carbon footprint of cementing operations. Additionally,
metakaolin production has less batch-to-batch variability than Portland cement, which may
reduce unpredictable or inconsistent results when employed in a wellbore. Inconsistent
results may be further mitigated with the use of metakaolin because the mineral phases of
metakaolin, and other aluminosilicates, are stable at high temperature. Whereas Portland
cement mineral phases at temperatures greater than about 230 °F (about 0 °C) may display
strength retrogression.
[0028] Furthermore, the settable fluids provided herein may be produced at
variable densities and may be compatible with known foaming agents, fluid loss control
agents, and other common additives. The cementitious blends and settable fluids may also
have strength and pumping characteristics similar to that of Portland cement compositions.
Therefore, the cementitious blends and settable fluids of the present invention may be
available for easy and cost effective integration into existing wellbore operations and
methods.
[0029] It should be noted that when "about" is provided at the beginning of a
numerical list, "about" modifies each number of the numerical list. In addition, in some
numerical listings of ranges, some lower limits listed may be greater than some upper limits
listed. One skilled in the art will recognize that the selected subset will require the selection
of an upper limit in excess of the selected lower limit. Whenever a range of values is given,
any subset of that range (between the highest and lowest point) is an acceptable alternative
range in the embodiments of the present invention.
[0030] In some embodiments, a cementitious blend of the present invention
may comprise metakaolin particulates and aluminosilicate particulates. It should be
understood that the term "particulate" or "particle," as used in this disclosure, includes all
known shapes of materials, including, but not limited to, spherical materials, substantially
spherical materials, low to high aspect ratio materials, fibrous materials, polygonal materials
(such as cubic materials), and mixtures thereof. Generally, metakaolin is a white pozzolana
that may be prepared by heating kaolin clay, for example, to temperatures in the range from
500 °C to about 900 °C. In some embodiments, metakaolin particulates may comprise highreactive
metakaolin. Generally, high-reactive metakaolin is metakaolin that had been
processed to temperatures in excess of 650 °C. In some embodiments, metakaolin may be
present in the cementitious blend in a concentration ranging from a lower limit of about 5%,
10%, 15%, 25%, or 50% by weight of settable blend to an upper limit of about 85%, 75%,
65%, or 50% by weight of cementitious blend, and wherein the concentration may range
from any lower limit to any upper limit and encompass any subset between the upper and
lower limits.
[0031] Suitable aluminosilicate particulates may be any known pozzolans
comprised of aluminum oxides and silicon oxides. Examples of aluminosilicate particulates
include, but are not limited to, fly ash including Class F and Class C; cement kiln dust;
biowaste ash; zeolite; slag cement; shale particulates; pumice (including pumicite); and any
combination thereof. Suitable examples of fly ash include, but are not limited to,
POZMIX®A (cement additive, available from Halliburton Energy Services, Inc., Duncan,
OK) and Micro Fly Ash® (cement additive, available from Halliburton Energy Services,
Inc., Duncan, OK). In some embodiments, aluminosilicate may be present in the settable
blend in a concentration ranging from a lower limit of about 15%, 25%, 35%, 50%, or 60%
by weight of cementitious blend to an upper limit of about 95%, 85%, 75%, 65%, or 50% by
weight of cementitious blend, and wherein the concentration may range from any lower
limit to any upper limit and encompass any subset between the upper and lower limits.
[0032] In some embodiments, a cementitious blend of the present invention
may be essentially Portland cement free. As used herein, the term "essentially free" should
be taken to mean less than about 1% by weight of cementitious blend. In some
embodiments, the cementitious blend may contain Portland cement in an amount less than
about 0.1%, 0.05%, or 0.01% by weight of cementitious blend. By way of nonlimiting
example, the cementitious blend may be free of Portland cement, i.e., the cementitious blend
contains no Portland cement. Suitable Portland cements may include, but are not limited to,
those classified as American Petroleum Institute Classes A, C, G, and H; ASTM Type I, II,
and III; and any combination thereof.
[0033] In some embodiments, a settable fluid of the present invention may
comprise a cementitious blend, an aqueous-based medium, and a lime composition. As used
herein, the term "settable fluid" should be taken to mean a composition that over time sets to
form a hardened mass. Suitable aqueous-based medium for use in the present invention may
comprise fresh water, saltwater (e.g., water containing one or more salts dissolved therein),
brine {e.g., saturated salt water), seawater, and any combination thereof. Generally, the
water may be from any source, provided that it does not contain components that might
adversely affect the stability and/or performance of the compositions or methods of the
present invention. In some embodiments, an aqueous-based medium may comprise a salt.
Suitable salts may be any mono- or multivalent salts including, but not limited to, sodium
salts, potassium salts, magnesium salts, calcium salts, chloride salts, bromide salts, sulfate
salts, carbonate salts, phosphate salts, and any combination thereof. In some embodiments,
salts may be present in an aqueous-based medium in concentration up to its saturated
concentration limit at bottom hole pressure and temperature, for example, about 37% by
weight of water at ambient conditions.
[0034] As used hereinafter, the term "lime composition" should be taken to
mean a composition comprising alkali metal oxides such as calcium oxide, calcium
hydroxide, magnesium oxide, or any combination thereof. In some embodiments, the lime
composition may comprise hydrated lime. In some embodiments, a lime composition may
be present in a settable fluid in an amount ranging from a lower limit of about 5%, 10%,
15%, or 25% to an upper limit of about 50%, 40%, 30%, 25%, or 15% by weight of
cementitious blend, and wherein the concentration may range from any lower limit to any
upper limit and encompass any subset between the upper and lower limits.
[0035] In some embodiments, a settable fluid of the present invention is
introduced into a wellbore and/or a subterranean formation and allowed to set therein.
Suitable subterranean formations include all subterranean formations including, but not
limited to, formations containing corrosive components; low-temperature formations, i.e.,
about 30 °F (about - 1 °C) to about 80 °F (about 27 °C) bottom hole circulating temperature;
formations with a salt dome, sheet, pillar, or other structure; evaporite formations;
unconsolidated formations; shale formations; and any combination thereof. Corrosive
components may include, but not be limited to, acids including carbonic acid, hydrochloric
acid, hydrofluoric acid, acetic acid, sulfuric acid, formic acid, and the like; dissolved carbon
dioxide; salts including mono- and multivalent salts, e.g., sodium chloride and magnesium
chloride; sulfur containing compounds including hydrogen sulfide, sulfuric acid, and sulfur;
microorganisms and their byproducts; and any combination thereof. By way of nonlimiting
example, a settable fluid may be introduced into a wellbore penetrating a subterranean
formation with a salt dome and high levels of carbonic acid. The cementitious blends and
settable fluids provided herein may be particularly well-suited for use in corrosive
formations. By way of nonlimiting example, the Singa formation in Indonesia, which
comprises about 30% C0 2 and 1 % H2S, may be well-suited for the cementitious blends and
settable fluids provided herein.
[0036] In some embodiments, a settable fluid may be used for primary
cementing operations or remedial cementing operations. By way of nonlimiting example of
primary cementing, a settable fluid may be introduced into an annulus between a pipe string
located in a subterranean formation and the subterranean formation and then allowed to set
therein. By way of nonlimiting example of remedial cementing, a settable fluid may be used
in squeeze cementing operations or in the placement of cement plugs. Additional examples
may include using a settable fluid to plug a void or crack in a conduit in a wellbore; to plug
a void or crack in a cement sheath disposed in an annulus of the wellbore; to plug an
opening between the cement sheath and a conduit; to prevent the loss of aqueous or non¬
aqueous drilling fluids into loss circulation zones such as a void, vugular zone, or fracture;
to be used as a fluid in front of cement slurry in cementing operations; to seal an annulus
between the wellbore and an expandable pipe or pipe string; or combinations thereof.
Figure 2 illustrates a nonlimiting example of using a settable fluid described herein to
provide lost circulation control in a partially unconsolidated subterranean formation. Figure
2 illustrates a wellbore 500 and a casing 510 with an annulus 520 therebetween that
penetrates as subterranean formation with hydrocarbon-bearing zones 100 and 200, wherein
hydrocarbon-bearing zone 100 is an unconsolidated zone. Zonal isolation of the
unconsolidated hydrocarbon-bearing zone 100 is provided by a set composition 405
produced from a settable fluid provided herein.
[0037] In some embodiments, the settable fluid may be included in another
treatment fluid including, but not limited to, a spotting fluid, a flush fluid, a spacer fluid, a
cement slurry, a squeeze fluid, a drilling fluid, and a consolidation fluid. In some
embodiments, the settable fluid may be foamed.
[0038] In some embodiments, the settable fluid of the present invention may be
used in conjunction with specific wellbore operations including, but not limited to, casing
operations, plugging operations, drilling operations, lost circulation operations, filter cake
operations, sand control operations, fracturing operations, completion operations, waterblocking
operations, clay stabilizer operations, and wellbore strengthening operations. The
methods and compositions of the present invention may be used in full-scale operations or
pills. As used herein, a "pill" is a type of relatively small volume of specially prepared
treatment fluid placed or circulated in the wellbore.
[0039] In some embodiments, a settable fluid of the present invention may be
introduced into a wellbore that has a cementitious composition already present therein. In
some embodiments, a settable fluid of the present invention may be used in remedial
operations to strengthen an existing cementitious composition within a wellbore and/or
subterranean formation.
[0040] Based on the wellbore operation and other factors, one skilled in the art
would understand additives that may be added to a settable fluid including, but not limited
to, set retarders, set accelerators, viscosifiers, gases, surfactants, fluid loss control additives,
suspending aids, mechanical properties modifiers, density modifiers, gas migration control
aids, and any combination thereof. One skilled in the art would understand the plurality of
available additive that may be added to a settable fluid and in what concentrations to achieve
a desired fluid property.
[0041] Suitable set retarders may be any known set retarder applicable in
subterranean formations including, but not limited to, HR-5® (sodium salt of lignosulfonate,
available from Halliburton Energy Services, Inc., Duncan, OK), HR-6L® (lignosulfonate
retarder, available from Halliburton Energy Services, Inc., Duncan, OK), HR-25® (tartaric
acid, available from Halliburton Energy Services, Inc., Duncan, OK), HR-15® (mixture of
lignosulfonate and tartaric acid, available from Halliburton Energy Services, Inc., Duncan,
OK), HR-800® (non-lignin cement retarder, available from Halliburton Energy Services,
Inc., Duncan, OK), HR-817® (non-lignin cement, high-temperature retarder, available from
Halliburton Energy Services, Inc., Duncan, OK), SCR- 100® (a copolymer of 2-acrylamide-
2-methylpropane sulfonic acid and acrylic acid, available from Halliburton Energy Services,
Inc., Duncan, OK), FDP 601™ (lignosulfonate retarder, available from Halliburton Energy
Services, Inc., Duncan, OK), SCR-500™ (a copolymer of 2-acrylamido-2-methylpropane
sulfonic acid and itaconic acid, available from Halliburton Energy Services, Inc., Duncan,
OK) and any combination thereof. Set retarders may be included in a settable fluid in a
concentration ranging from a lower limit of about 0.05%, 0.1%, 0.25%, 0.5%, 1%, 2%, or
3% to an upper limit of about 10%, 5%, 3%, 2%, 1%, or 0.5% by weight of cementitious
blend, and wherein the concentration may range from any lower limit to any upper limit and
encompass any subset between the upper and lower limits. By way of nonlimiting example,
a settable fluid with the addition of a retarder in sufficient quantity, e.g., about 2% to about
15%, may be used as a drilling fluid. As such, the retarder may provide for the fluid to not
set for at least 7 days, 4 days, 72 hours, or 48 hours after introduction into the wellbore.
[0042] Figure 1 illustrates a nonlimiting example of using a settable fluid
comprising a set retarder described herein. An oil rig 40 may be positioned near the surface
of the earth 42 for later recovering oil from a subterranean formation (not shown). A
wellbore 44 may be drilled in the earth such that it penetrates the subterranean formation. A
pipe 52, e.g., a casing, may extend down through wellbore 44 for delivering fluid to and/or
from the wellbore. In a primary cementing process, the settable fluid may be pumped down
through pipe 52 and up through the annulus of wellbore 44 as indicated by arrows 46 using
one or more pumps 54. The settable fluid may be allowed to set within the annulus, thereby
sealing wellbore 44. Due to the presence of the set retarder in the settable fluid, the
thickening time is desirably sufficient to allow the settable fluid to be pumped into the
annulus such that it substantially fills the annulus before setting. Any secondary cementing
operations known in the art may also be performed using the cement composition. For
example, a squeeze cementing technique may be employed to plug permeable areas or voids
in the cement sheath or the pipe 52. Again, the thickening time of the cement composition is
sufficient to ensure that the cement composition remains pumpable until it has been placed
in its desired location.
[0043] Suitable set accelerators may be any known set accelerator applicable in
subterranean formations including, but not limited to, calcium hydroxide, sodium hydroxide,
sodium sulfate, sodium carbonate, sodium silicate, nanomaterials, and any combination
thereof. Set accelerators may be included in a settable fluid in a concentration ranging from
a lower limit of about 0.01%, 0.05%, 0.1%, 0.25%, 0.5%, 1%, 2%, or 3% to an upper limit
of about 15%, 10%, 5%, 3%, 2%, 1%, or 0.5% by weight of cementitious blend, and
wherein the concentration may range from any lower limit to any upper limit and encompass
any subset between the upper and lower limits. By way of nonlimiting example, a settable
fluid with the addition of an accelerator in sufficient quantity, e.g., about 0.02% to about
15%, may be used as a drilling fluid.
[0044] Suitable fluid loss control agents may be any known fluid loss control
agent applicable in subterranean formations including, but not limited to, HALAD®-413
(causticized lignite grafted with 2-acrylamido-2-methylpropane sulfonic acid, N,Ndimethylformamide
and acrylonitrile, available from Halliburton Energy Services, Inc.,
Duncan, OK), HALAD®-344 (a copolymer of N,N-dimethylformamide and 2-acrylamido-2-
methylpropane sulfonic acid, available from Halliburton Energy Services, Inc., Duncan,
OK), HALAD®-862 (cement additive, available from Halliburton Energy Services, Inc.,
Duncan, OK), HALAD®-567 (synthetic polymer, available from Halliburton Energy
Services, Inc., Duncan, OK), carboxy methyl hydroxyethyl cellulose, acrylomorpholine and
vinyl phosphonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and any
combination thereof. One skilled in the art would understand the plurality of other
components and additives that may also function to some degree as fluid loss control agents
including, but not limited to, fillers or extenders such as gilsonite, diatomaceous earth,
ground coal, sand, and the like. Fluid loss control agents may optionally be included in a
settable fluid in a concentration ranging from a lower limit of about 0.05%, 0.1%, 0.25%,
0.5%, 1%, 5%, or 1 % to an upper limit of about 25%, 15%, 10%, 5%, or 1% by weight of
cementitious blend, and wherein the concentration may range from any lower limit to any
upper limit and encompass any subset between the upper and lower limits.
[0045] In some embodiments, a settable fluid of the present invention may
comprise a density modifier to assist in achieving a high-density fluid, i.e., greater than
about 13.5 pounds per gallon (ppg) [about 1620 kg/m3], or a low-density fluid, i.e., less than
about 13.5 pounds per gallon (ppg) [about 1620 kg/m3]. Suitable high-density modifiers
may be any known high-density modifier including, but not limited to, MICROMAX ®
(ground hausmannite ore, available from Halliburton Energy Services, Inc., Duncan, OK),
barite, HI-DENSE ® #3&4 (hematite ore, available from Halliburton Energy Services, Inc.,
Duncan, OK), and any combination thereof. Suitable low-density modifiers may be any
known low-density modifier including, but not limited to, hollow glass beads, foaming by a
gas, elastomers, perlites, cenospheres, hollow polymeric beads, and any combination
thereof. One skilled in the art would understand the concentration of a density modifier to
add to a settable fluid to achieve a desired density.
[0046] In some embodiments, a settable fluid may comprise a cementitious
composition that thickens in greater than about 3 hours as measured by high-temperature
and high-pressure consistometer at a desired bottom hole circulating temperature within the
range of about 30 °F (about - 1 °C) to about 650 °F (about 343 °C). In some embodiments, a
settable fluid may comprise an additive such that the settable fluid thickens in greater than
about 3 hours as measured by high-temperature and high-pressure consistometer at a desired
bottom hole circulating temperature within the range of about 80 °F (27 °C) to about 650 °F
(343 °C). As used herein, the "thickening time" refers to the time required for the cement
composition to achieve 70 Bearden units of Consistency (Be), as described in API
Recommended Practice for Testing Well Cements 10B, 23rd edition, April 2002. At about
70 Be, the slurry undergoes a conversion from a pumpable fluid state to a non-pumpable
paste. In some embodiments, the settable fluid with or without an additive may have a
thickening time from a lower limit of about 3 hours, 6 hours, 12 hours, 24 hours, 48 hours,
72 hours, or 5 days to an upper limit of about 2 weeks, 1 week, 5 days, or 72 hours, and
wherein the thickening time may range from any lower limit to any upper limit and
encompass any subset between the upper and lower limits. In some embodiments, the
settable fluid with or without an additive may remain pumpable, i.e., not thicken, for about 3
hours after introduction into the wellbore.
[0047] Suitable bottom hole circulating temperatures (BHCT) of a wellbore
and/or subterranean formation may be any BHCT suitable for the use of a predominantly
Portland cement composition. One skilled in the art would understand the necessary
additives, concentrations, and/or processing adjustments needed for using a cementitious
blend of the present invention with a given BHCT. Generally, the BHCT may range from a
lower limit of about 30 °F (-1 °C), 100 °F (38 °C), 150 °F (66 °C), 200 °F (93 °C), or 250 °F
(121 °C) to an upper limit of about 650 °F (343 °C), 600 °F (316 °C), 550 °F (288 °C), 500
°F (260 C), 450 °F (232 °C), 400 °F (204 °C), 350 °F (177 °C), 300 °F (149 °C), 250 °F
(121 °C), 200 °F (93 °C), 150 °F (66 °C), or 100 °F (38 °C), and wherein the temperature
may range from any lower limit to any upper limit and encompass any subset between the
upper and lower limits.
[0048] In some embodiments, a method comprises providing a settable fluid
that comprises an aqueous-based medium, a lime composition, and a cementitious blend that
comprises metakaolin particulates and aluminosilicate particulates, wherein the cementitious
blend is essentially free of Portland cement; introducing the settable fluid into a wellbore
penetrating a subterranean formation that comprises a corrosive component; and allowing
the settable fluid to set therein.
[0049] In some embodiments, a method comprises providing a drilling fluid that
comprises an aqueous-based medium, a lime composition, a set retarder, and a cementitious
blend that comprises metakaolin particulates and aluminosilicate particulates, wherein the
drilling fluid is essentially free of Portland cement, and wherein the set retarder is greater
than about 2% by weight of settable blend; and drilling at least a portion of a wellbore
penetrating a subterranean formation with the drilling fluid.
[0050] In some embodiments, a settable fluid comprises an aqueous-based
medium; a settable blend comprising metakaolin particulates at a concentration of about 5%
to about 85% by weight of the settable blend and a fly ash at a concentration of about 15%
to about 95% by weight of the settable blend; and a lime composition at a concentration of
about 5% to about 25% by weight of the settable blend, wherein the settable fluid does not
include a Portland cement.
[0051] To facilitate a better understanding of the present invention, the
following examples of preferred embodiments are given. In no way should the following
examples be read to limit, or to define, the scope of the invention.
EXAMPLES
[0052] Settable Fluids Tested. Table 1 below provides density and composition
data for five settable fluid slurries comprising cementitious blends of the present invention
and one slurry of Portland cement for comparison. The cementitious blends contain
POZMX ® A and metakaolin. All other components of the slurry were added at
concentration measured in percent by weight cementitious blend (% bwc) unless otherwise
specified.
[0053] Compressive Strength Development. Ultrasonic cement analyzer (UCA)
used to monitor compressive strength development on each slurry. About 120 mL of a
slurry was added to the sample container. The slurry was heated to 200 °F (93 °C) at 3000
psi (21 MPa) while monitoring the compressive strength and acoustic transient time (a
measure of apparent strength, i.e., shorter transient times indicate higher strength). An
ultrasonic cement analyzer ("UCA") available from FANN Instrument Company, UCA
autoclave (controller model 304) was used to determine the compressive strength of the
slurries after twenty-four hours. The UCA tests were performed in accordance with API
Recommended Practice 10B-2 (ISO 10426-2), First edition, July, 2005, "Recommended
Practice for Testing Well Cements." Compressive strength predicted my UCA was
calibrated to obtain a real compressive strength after evaluating and calibrating with the
UCA cured sample using Tenious Olsen device, as shown below in Table 2.
[0054] The settable fluids display the expected response in changes to the
composition. For example, the addition of the accelerator (2% Na2S0 ) in Sample #3
relative to Sample #4 speeds the setting process as expected thereby reaching higher
compressive strengths sooner. Additionally, a cementitious blend of the present invention
can be optimally accelerated (Sample #3) to achieve comparable compressive strengths to a
Portland cement composition (Comparative Sample #6).
[0055] Comparison between Sample #3 and Comparative Sample #6,
demonstrate, once accelerated {i.e., properly optimized), the settable composition of the
present invention exhibits comparable compressive strength after 48 hrs to a Portland
cement.
[0056] Thickening Retardation. Sample #2 was further altered with different
retardant compositions and concentrations, as shown in Table 3 below. The thickening time
was measured in accordance with API Recommended Practice 10B-2. As used herein,
"thickening time" refers to the time required for the cement composition to achieve 70
Bearden units of Consistency (Be), as described in API Recommended Practice for Testing
Well Cements 10B, 23rd edition, April 2002. At about 70 Be, the slurry undergoes a
conversion from a pumpable fluid state to a non-pumpable paste. As demonstrated, the
cementitious blends of the present invention may be used with a variety of set retarders at
varying concentrations to achieve a desired thickening time. For standard cementing
operations it may be desirable to have thickening times of greater than about 3 hours. One
skilled in the art would understand the utility of adjusting the thickening time of a settable
fluid.
[0057] Compatibility with Salts containing MgC^- Sample #2 with 1% bwc
R®-15 retarder was conditioned at 190 °F (88 °C) using an atmospheric consistometer for
two hours. Rheology values were taken immediately after conditioning. Then 3% bwc salt
(MgCl2.6H20:KCl:NaCl of 0.71:0.26:0.03) was mixed with the conditioned Example #2
using a blender followed by 10 minutes further conditioning in the atmospheric
consistometer at 190 °F (88 °C). Rheology values provided below were taken with a Fann
Model 35. As used herein, the "viscosity" is measured according to API RP 10B-2/ISO
10426-2 as follows. The material to be tested, such as a liquid concentrate, is prepared. The
material is placed into the test cell of a rotational viscometer, such as a Fann Model 35.
Viscosity can be calculated using the following equation, expressed in units of centipoise:
k3 N
where ki is the torsion constant in dyne*cm/degree deflection; k2 is the shear stress constant
in cm3; (100) is the conversion constant from Poise to centipoise; Qis the dial reading on the
viscometer; k is the shear rate constant in 1/sec per revolutions per minute (rpm); and N is
the rpm.
[0058] Viscosity after addition of salt increases, but the settable fluid remains
pumpable as measured by atmospheric consistometer. Before salt addition, the settable fluid
displayed a consistency of 10 Be. After salt addition, the consistency of the settable fluid
increased to 15 Be which is well below the 70 Be threshold below which a fluid is
pumpable. The results are shown in Table 4, below.
[0059] Therefore, the present invention is 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 invention may be modified
and practiced in different but equivalent manners apparent to those skilled in the art having
the benefit of the teachings herein. Furthermore, no limitations are intended to the details of
construction or design herein shown, other than as described in the claims below. It is
therefore evident that the particular illustrative embodiments disclosed above may be
altered, combined, or modified and all such variations are considered within the scope and
spirit of the present invention. While compositions and methods are described in terms of
"comprising," "containing," or "including" various components or steps, the compositions
and methods can also "consist essentially of or "consist of the various components and
steps. All numbers and ranges disclosed above may vary by some amount. Whenever a
numerical range with a lower limit and an upper limit is disclosed, any number and any
included range falling within the range is specifically disclosed. In particular, every range
of values (of the form, "from about a to about b," or, equivalently, "from approximately a to
b," 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. Also, the
terms in the claims have their plain, ordinary meaning unless otherwise explicitly and
clearly defined by the patentee. 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. If
there is any conflict in the usages of a word or term in this specification and one or more
patent or other documents that may be incorporated herein by reference, the definitions that
are consistent with this specification should be adopted.

CLAIMS:
1. A method of cementing, the method comprising:
providing a settable fluid that comprises an aqueous-based medium, a lime
composition, and a cementitious blend that comprises metakaolin particulates and
aluminosilicate particulates,
wherein the cementitious blend is essentially free of Portland cement;
introducing the settable fluid into a wellbore penetrating a subterranean
formation that comprises a corrosive component; and
allowing the settable fluid to set therein.
2. A method according to claim 1, wherein the corrosive component is selected
from the group consisting of an acid; dissolved carbon dioxide; a monovalent salt; a
multivalent salt; a sulfur containing compound; a microorganism and a byproduct thereof;
and any combination thereof.
3. A method according to claim 1 or 2, wherein the settable fluid further
comprises an additive selected from the group consisting of a set retarder, a set accelerator, a
viscosifier, a gas, a surfactant, a fluid loss control additive, a suspending aid, a mechanical
properties modifier, a density modifier, a gas migration control aid, and any combination
thereof.
4. A method according to claim 1, 2 or 3, wherein the metakaolin particulates
comprise high-reactive metakaolin particulates.
5. A method according to any preceding claim, wherein the metakaolin
particulates are present in the settable fluid at about 5% to about 85% by weight of total
cementitious blend.
6. A method according to any preceding claim, wherein at least some of the
aluminosilicate particulates are selected from the group consisting of a Class F fly ash
particulate, a Class C fly ash particulate, a cement kiln dust particulate, a biowaste ash
particulate, a zeolite particulate, a slag particulate, and any combination thereof.
7. A method according to any preceding claim, wherein the aluminosilicate
particulates are present in the settable fluid at about 15% to about 95% by weight of total
cementitious blend.
8. A method according to any preceding claim, wherein the lime composition is
present in the settable fluid in an amount of about 5% to about 50% by weight of total
cementitious blend.
9. A method according to any preceding claim, wherein the settable fluid is
foamed.
10. A method according to any preceding claim, wherein the settable fluid is
included in a treatment fluid selected from the group consisting of a spotting fluid, a flush
fluid, a spacer fluid, a cement slurry, a squeeze fluid, a drilling fluid, and a consolidation
fluid.
11. A method according to any preceding claim, wherein the subterranean
formation includes a cementitious composition that was placed therein prior to introducing
the settable fluid into the wellbore.
12. A method according to any preceding claim, wherein the subterranean
formation has a bottom-hole temperature of about 30 °F (-1 °C) to about 230 °F ( 1 0 °C).
13. A method according to any preceding claim, wherein the settable fluid has a
thickening time of about 3 hours to about 5 days as measured by high-temperature and highpressure
consistometer at a desired bottom hole circulating temperature within the range of
about 80 °F (27 °C) to about 650 °F (343 °C).
14. A method according to any preceding claim, wherein the settable fluid has a
density greater than about 13.5 pounds per gallon ( 620 kg m3).
15. A method according to any one of claims 1 to 13, wherein the settable fluid
has a density less than about 13.5 pounds per gallon (1620 kg m3).
16. A method comprising:
providing a drilling fluid that comprises an aqueous-based medium, a lime
composition, a set retarder, and a cementitious blend that comprises metakaolin particulates
and aluminosilicate particulates,
wherein the drilling fluid is essentially free of Portland cement, and
wherein the set retarder is present at about 2% to about 15% by weight
of cementitious blend; and
drilling at least a portion of a wellbore penetrating a subterranean formation
with the drilling fluid.
17. A method according to claim 16, wherein the drilling fluid does not set for at
least about 72 hours after introduction into the wellbore.
18. A method according to claim 16 or 17, wherein the drilling fluid further
comprises an additive selected from the group consisting of a set retarder, a set accelerator, a
viscosifier, a gas, a surfactant, a fluid loss control additive, a suspending aid, a mechanical
properties modifier, a density modifier, a gas migration control aid, and any combination
thereof.
19. A method according to claim 16, 17 or 18 wherein the portion of the wellbore
being drilled contains a corrosive component selected from the group consisting of carbonic
acid; dissolved carbon dioxide; a monovalent salt; a multivalent salt; sulfur containing
compounds; and any combination thereof.
20. A settable fluid comprising:
an aqueous-based medium;
a cementitious blend comprising:
metakaolin particulates at a concentration of about 5% to about 85%
by weight of the cementitious blend and
a fly ash at a concentration of about 15% to about 95% by weight of
the cementitious blend; and
a lime composition at a concentration of about 5% to about 25% by weight of
the cementitious blend,
wherein the settable fluid does not include a Portland cement.