Note: Descriptions are shown in the official language in which they were submitted.
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SUBTERRANEAN TREATMENT g'I.,UIIDS COMEPRISIlwTG SUBSTANTIALLY
KYDRATEI) CEMENT PARTICULATES
BACKGROUND
The present invention relates to substantially hydrated cement particulates.
More
particularly, the present invention relates to subterranean treatinent fluids
comprising
substantially hydrated cement particulates and associated methods of use in
subterranean
applications.
Hydraulic fracturing is a process cominonly used to increase the flow of
desirable
fluids, such as oil and gas, from a portion of a subterranean formation.
Hydraulic fracturing
operations generally involve introducing a fracturing fluid into a
subterranean formation at or
above a pressure sufficient to create or enhance one or more fractures in the
fonnation.
Enhancing a fracture includes enlarging a pre-existing fracture in the
fonnation. The
fracturing fluid inay comprise particulates, often referred to as "proppant"
that are deposited
in the fractures. The proppant fimctions to prevent the fractures from fully
closing upon the
release of pressure, fonning conductive channels through which fluids may flow
to (or froin)
the well bore.
Another process that involves the use of particulates is gravel packing. A
"gravel
pack" is a tenn cominonly used to refer to a voh.une of particulate materials
(such as sand)
placed into a well bore to at least partially reduce the migration of
unconsolidated fonnation
particulates into the well bore. Gravel packing operations coininonly involve
placing a gravel
pack screen in the well bore neighboring a desired portion of the subterranean
fonnation, and
packing the surrounding annulus between the screen and the subterranean
fonnation with
particulate materials that are sized to prevent and inhibit the passage of
fonnation solids
through the gravel pack with produced fluids. In some instances, a screenless
gravel packing
operation may be perfonned.
Conventional particulates included as proppant and/or gravel in subterranean
trea.tinent fluids include, but are not liinited to: sand; bauxite; ceramic
materials; glass
lnaterials; polymer materials; Teflon"" inaterials; nut shell pieces; seed
shell pieces; fruit pit
pieces; wood; composite particulates; cured resinous particulates coinprising
nut shell pieces,
seed shell pieces, inorganic fillers, and/or fruit pit pieces; and
coinbinations thereof.
Conventionally, composite particulates that may be used comprise a binder and
a filler
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material wherein suitable filler inaterials include silica, alumina, fumed
carbon, carbon black,
graphite, mica, titanium dioxide, meta-silicate, calcium silicate, kaolin,
talc, zirconia, boron,
fly ash, hollow glass microspheres, solid glass, and coinbinations thereof
Sand is a common
particulate utilized in subterranean treatrnent fluids as either proppant or
gravel, but there
may be issues related to supply and cost associated with using sand.
To modify one or more properties of a subterranean treatnlent fluid, various
admixtures may be incl-Lided in the subterranean treatment fluid. As used
herein, the term
"admixture" refers to materials, other than the base fluid used for inalcing
the subterranean
treaftnent fl_uid, which may be added to the subterranean treatinent fluid
before or during its
mixing. Admixtures oftentimes are provided in the fonn of liquids or soluble
solids (e.g.,
powders). Atternpts have been inade to counteract the problems that may be
associated with
the delivery of adinixtures in solid and liquid fonn. For instance, an adniix-
ture provided in
powdered form may become dry compacted, or the adinixture, in another
instance, may be
coated onto a carrier particle. However, iinprovelnents are needed for the
delivery of
adinixtures into subterranean treatinent fluids.
SU1VCVLARY
The present invention relates to substantially hydrated cement particulates.
More
particularly, the present invention relates to subterranean treatinent fluids
comprising
substantially hydrated cement particulates and associated methods of use in
subterranean
applications.
An embodiment of the present invention provides a fracturing fluid that
comprises a
base fluid, and substantially hydrated ceinent particulates.
Anotlier embodiinent of the present invention provides a gravel packing fluid
that
comprises a base flliid, and gravel comprising substantially hydrated cement
particulates.
An embodiment of the present invention provides a method of fracturing a
subterranean forination that comprises fracturing the subterranean fonnation
so as to create or
enhance one or more fractures in the subterranean fonnation; introducing a
fracturing fluid
coinprising a base fluid and substantially hydrated ceinent particulates into
the one or more
fractures; and depositing at least a portion of the substantially hydrated
cenient particulates in
the one or more fractures in the subterranean fonnation.
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Another einbodiment of the present invention provides a method of gravel
packing
that comprises providing a gravel packing fluid coinprising a base fluid and
substantially
hydrated cement particulates, introducing the gravel packing fluid into a
subterranean
formation, and depositing at least a portion of the substantially hydrated
cement particLilates
in the subterranean formation so as to form, a gravel pack.
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 exainple
embodiinents, which
follows.
DESCRIPTION OF PREFERRED FM-BODI1.VIENTS
The present invention relates to substantially hydrated cement particulates.
More
particularly, the present invention relates to subterranean treatinent fluids
colnprising
substantially hydrated cement particulates and associated methods of use in
subterranean
applications. While the substantially hydrated cement particulates of the
present invention
are useful in a variety of applications, they may be particularly useful when
included in
fractLiring fluids as proppant or in gravel paclcing fluids as gravel.
The subterranean treatment fluids of the present invention generally colnprise
a base
fluid and substantially hydrated cement particulates. In some embodiments, the
substantially
hydrated cement particulates may colnprise an admixture. The substantially
hydrated cement
particulates may be included in the subterranean treatment fluid as proppant,
gravel, lost
circulati on inaterials, carriers for admixtures, or combinations thereof.
The base fluids utilized in the subterranean treatment fluids of the present
invention
can be any fhiid suitable for use as a base fluid in fracturing or gravel
packing operations.
Suitable base fluids include, but are not limited to, water, aqueous gels,
viscoelastic
surfactant gels, oil gels, gases, liquefied gases, liquefied hyrdocarbons,
einulsions, and
coinbinations thereof Suitable aqueous gels are generally comprised of water
and one or
more gelling or viscosifying agents. Optionally, the aqueous gel further may
comprise a
crosslinking agent for crosslinking the gelling agent and further increasing
the viscosity of
the fluid. Suitable viscoelastic surfactant gels may coinprise a viscoelastic
surfactant and
water. Suitable emulsions can be colnprised of two immiscible liquids such as
an aqueous
liquid or gelled liquid and a hydrocarbon. Suitable water used in the base
fluids can be fresh
water, salt water (e.g.,, water containing one or lnore salts dissolved
therein), brine (e.g.,
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saturated salt water), seawater, or any other aqueous liquid that does not
adversely affect
other coinponents in the subterranean treatment fluid. The base fluid may also
be foained or
unfoained as desired for a particular application and may include, for
exainple, air, carbon
dioxide, and/or nitrogen.
The subterranean treatinent fluids of the present invention further coinprise
substantially hydrated cement particulates. The substantially hydrated cement
particulates
may be forined in any suitable manner. In certain einbodiments of the present
invention, the
substantially hydrated cement particulates present in the subterranean
treatment fluids of the
present invention are formed by providing a settable co?nposition coinprising
a hydraulic
cementitious material and water; allowing the settable coinposition to set
into a substantially
hydrated mass; and comminuting the substantially hydrated mass into smaller
particles so as
to form the substantially hydrated cement particulates used in the methods of
the present
invention. In another einbodiment, the settable coinposition further may
coznprise an
admixture. By including an admixture in the settable composition, the
substantially hydrated
cement particulates fonned using this settable cornposition should comprise
the admixture.
In another embodiment, after colnminution of the substantially hydrated mass
into the
substantially hydrated celnent particulates, the substantially hydrated cement
particulates may
be coated with at least one admixture. This permits the coinbination of
adtnixtures that may
not be coinpatible when used in solution. An example method for producing the
substantially
hydrated cement particulates andlor intermixing the admixtures therein is
described in U.S.
Patent No. 6,648,962, the disclosLU-e of which is incorporated herein by
reference.
Comminution of the substantially hydrated mass to fonn the substantially
hydrated
cement particulates may be accomplished by any of a variety of suitable
metllods. For
exalnple, corruninution may be achieved by subjecting the substantially
hydrated mass to
colnpressive or grinding forces, such as by using a jaw crusher, a roller
crusher (e.g., opposed
steel rollers), a ball mill, a disk inill, or a grinder. After cornininution,
the substantially
hydrated cement particulates inay be highly granulate with a high surface
area, thereby
providing a high loading surface.
The size of the substantially hydrated cement particulates may vary based upon
the
desired application. In certain embodiments, the substantially hydrated cement
particulates
may have an average diameter in the range of from about 5 micrometers to about
2.5
milliineters. However, it should be understood that, in other embodiinents,
the substantially
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hydrated ceinent particulates may have an average diaineter of greater than
about 2.5
millimeters or of less than about 5inicrometers as desired. One of ordinary
skill in the art
with the benefit of this disclosure will know the appropriate size, of
particulates for a
particular application.
Generally, the hydraulic ceinentitious material used to form the substantially
hydrated
cement particulates may be any hydraulic ceinentitious material that is
suitable for use in
cementing operations. A variety of hydraulic ceinentitious materials are
suitable for use,
including those colnprised of calciuin, aluminuin, silicon, oxygen, and/or
sulfur, which set
and harden by reaction with water. Such hydraulic cementitious materials
include, but are
not limited to, Portland ceinents, pozzolanic celnents, gypsum ceinents, soil
cements, calciurn
phosphate cements, high-alumina content cements, silica ceinents, high-
alkalinity cements,
slag cements, ceinent lciln dust, or mixtures thereof. "Cement kiln dust," as
that terin is used
herein, refers to a partially calcined kiln feed which is typically relnoved
from the gas stream
and collected in a dust collector during the inanufacture of cement. The
chemical analysis of
cement kiln dust from various celnent manufactures varies depending on a
number of factors,
including the particular kiln feed, the efficiencies of the cement production
operation, and the
associated dust collection systeins. Cenzent kiln dust generally may comprise
a variety of
oxides, such as Si02, A1203, Fe203, CaO, MgO, SO3, Na20, and K20.
Vitrified shale also may be used to fonn the substantially hydrated cement
particulates. Among other things, in some embodilnents, vitrified shale inay
be included in
the settable coinpositions used to fonrn the substantially hydrated cement
particulates. Such
vitrified shale may react with lime present in, or added to, the settable
coinposition to fonn a
suitable cementing material, for exanple, calcium silicate hydrate. A variety
of vitrified
shales are suitable, including those comprising silicon, aluminum, calcitiun,
and/or
magnesium. Suitable exanples of vitrified shale include, but are not limited
to, PRESSUR-
SEAL`g' FINE LCM material and PRESSUR-SEAL' COARSE LCM inaterial, which are
comniercially available froin TXI Energy Services, Inc., Houston, Texas.
The water utilized to fonn the substantially liydrated cement particulates can
be fresh
water, salt water (e.g., water containing one or more salts dissolved
therein), brine (e.g.,
saturated salt water), or seawater. Generally, the water can be from any
source, provided that
it does not adversely affect other coinponents in the settable composition.
The water may be
present in an ainount sufficient to forin a puinpable slurry. In certain
exeinplary
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elnbodiments, the water is present in the settable compositions of the present
invention in an
amount in the range of from about 30% to about 180% by weight of the hydraulic
cementitious material. In certain einbodirnents, the water may be added to the
hydraulic
ceinentitious material, a.d.mixture(s), or both. In another ernbodiment, the
water may be
incorporated in an aqueous dispersion, emulsion, or solution containing the
admixture(s).
In certain embodiments of the present invention, the substantially hydrated
cement
particulates ftirther may coinprise a zeolite. Zeolites generally are porous
ahunino-silicate
minerals that may be either a natural or synthetic material. Synthetic
zeolites are based on
the same type of structural cell as natural zeolites, and may comprise
aluminosilicate
hydrates. As used herein, the tenn "zeolite" refers to all natural and
synthetic fonns of
zeolite.
In certain embodilnents of the present invention, the substantially hydrated
cement
particulates further inay coinprise an admixture. Among other things, this
provides for the
delivery of admixture(s) into a subterranean treatment fluid, for exalnple,
when the
substantially hydrated cement particulates coinprising an adinixture are added
to a settable
composition. The adznixture(s) may be provided as soluble solids (e.g.,
powders) or liquids.
Any admixture commonly used in fracturing or gravel packing flLUds may be
included in the
settable compositions. A wide variety of adinixtures may be included in the
subterranean
treatinent fluid, including, but not limited to, fluid loss control additives,
surfactants, salts,
defoa.mers, fonnation conditioning agents, expanding additives, flow enhancing
additives,
acids, corrosion inhibitors, breakers, crosslinking agents, viscoelastic
surfactants, friction
reducers, gelling agents, biocides, algicides, coinbinations thereof, and the
like. One skilled
in the art with the benefit of this disclosure will know the type of admixture
to include for a
particular application.
In certain einbodilnents of the present invention, after coinminution of the
substantially hydrated mass into the substantially hydrated ceinent
particulates, the
substantially hydrated cement particulates may be coated with at least one
admixture. The
coating of the adinixture(s) onto the substantially hydrated ceinent
particulates may be
applied using any suitable coating method.
The ainount of admixture or admixtures to include in the settable
coinpositions, coat
onto the substantially hydrated cement particulates, or both, should depend,
iwer alia, on the
desired ainount of the admixture(s) to incorporate into the subterranean
treatinent fluid. The
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desired ainount of the admixture(s) to incorporate into the subterranean
treatment fluid may
depend, inter alia, on the type of admixture(s) employed. Generally, the
adrnixture(s) may be
included in the settable coinposition in an adinixture(s)-to-hydraulic
cementitious material
weight ratio in the range of from about 5:95 to about 95:5. One of ordinary
skill in the art
with the benefit of this disclosure will know the appropriate a.inount of the
adinixti.ire(s) to
include in the settable composition for a particular application.
Ainong other things, the methods of the present invention may provide for the
accurate measurement of the amount of the adinixture(s) added to subterranean
treatinent
fluids as well as avoiding time-consuming labor, energy costs, and processing
complexity
that may be associated with conventional methods for the delivery of admixtLU-
es into
subterranean treatinent fluids. An accurate measurement of the amount of
adinixture(s) in the
subterranean treatment fluid may be obtained whether the admixture(s) is added
to a settable
composition, coated onto the substantially hydrated ceinent particulates, or
both. For
example, the alnount of the ad.inixture(s) introduced into the subterranean
treatinent fluid inay
be obtained by measuring the bulk weight of the substantially hydrated cement
particulates
and the relative amount of admixtures.
Typically, the substantially hydrated cement particulates may be included in a
subterranean treatment fluid of the present invention in an amount sufficient
for a particular
application. In some embodiments, the substantially hydrated cement
particulates are present
in an ainount up to about 30 pounds per gallon (ppg). In some embodiments, the
substantially hydrated cement particulates are present in an amount up to
about 23. ppg. In
some embodiments, the substantially hydrated ceinent particulates are present
in an amount
up to about 12 ppg. One of ordinary skill in the art, with the benefit of this
disclosure, will
recognize the appropriate substantially hydrated cement particulates
concentration of the
subterranean treatinent fluids for a chosen application.
Furtllerinore, additional additives may be added to the subterranean treatment
fluids
of the present invention as deein.ed appropriate by one skilled in the art.
Examples of such
additives include, but are not limited to, fluid loss control additives, lost
circulation materials,
surfactants, salts, fonnation conditioning agents, defoainers, acids,
corrosion inhibitors,
breakers, biocides, algicides, crosslinlcing agents, gelling agents,
viscoelastic surfactants,
friction reducers, expanding additives, flow enhancing additives,
coinbinations thereof, and
the lilce.
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In one einbodiment, the present invention provides a inethod of using a
fracturing
fluid in a subterranean formation colnprising: fracturing the subterranean
forma.tion so as to
create or enhance one or more fractures in the subterranean fon.nation;
introducing a
fracturing fluid comprising a base fluid and substantially hydrated cement
particulates into
the one or more fractures; and depositing at least a portion of the
substantially hydrated
ceinent particulates in the one or more fractures in the subterranean
fonnation. The
substantially hydrated ceinent particulates deposited in the one or more
fractures should prop
the fractures so as to prevent thein from fully closing. In some
embodi.inents, hydrocarbons
ina.y be produced froln the subterranean formation through the one or more
fractures.
In one elnbodiment, the present invention provides a method of gravel packing
coinprising: providing a gravel packing fluid comprising a base fluid and
substantially
hydrated cement particulates; introducing the gravel packing fluid into a
subterranean
formation; and depositing at least a portion of the substantially hydrated
cement particulates
in the subterranean formation so as to form a gravel pack. In soine embodiment
the gravel
packing fluid may be introduced into an annulus between a screen and the
subterranean
formation. In some embodiments, hydrocarbons may be produced from the
subterranean
formation through the gravel pack.
Therefore, the present invention is well adapted to carry out the objects and
attain the
ends and advantages mentioned as well as those which are inherent therein.
While nuinerous
changes inay be made by those skilled in the art, such changes are encompassed
within the
spirit of this invention as defined by the appended claims.
