U.S. patent application number 11/133697 was filed with the patent office on 2006-11-23 for methods of treating particulates and use in subterranean formations.
Invention is credited to Matthew E. Blauch, Robert E. JR. Hanes, Philip D. Nguyen, Mark A. Parker, Billy F. Slabaugh, Neil A. Stegent, Diederik van Batenburg, Jim D. Weaver, Thomas D. Welton.
Application Number | 20060260808 11/133697 |
Document ID | / |
Family ID | 37447270 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060260808 |
Kind Code |
A1 |
Weaver; Jim D. ; et
al. |
November 23, 2006 |
Methods of treating particulates and use in subterranean
formations
Abstract
Provided are methods of modifying the surface stress-activated
reactivity of proppant particulates used in subterranean
operations. In one embodiment, the methods comprise: providing a
plurality of particulates, at least one of which comprises a
mineral surface; providing a surface-treating reagent capable of
modifying the stress-activated reactivity of a mineral surface of a
particulate; and allowing the surface-treating reagent modify the
stress-activated reactivity of at least a portion of the mineral
surface of at least one particulate. In other embodiments, the
methods comprise the use of particulates comprising a modified
mineral surface in fluids introduced into subterranean
formations.
Inventors: |
Weaver; Jim D.; (Duncan,
OK) ; Slabaugh; Billy F.; (Duncan, OK) ;
Hanes; Robert E. JR.; (Oklahoma City, OK) ; van
Batenburg; Diederik; (Delft, NL) ; Parker; Mark
A.; (Marlow, OK) ; Blauch; Matthew E.;
(Duncan, OK) ; Stegent; Neil A.; (Cypress, TX)
; Nguyen; Philip D.; (Duncan, OK) ; Welton; Thomas
D.; (Duncan, OK) |
Correspondence
Address: |
Robert A. Kent
2600 S. 2nd Street
Duncan
OK
73536-0440
US
|
Family ID: |
37447270 |
Appl. No.: |
11/133697 |
Filed: |
May 20, 2005 |
Current U.S.
Class: |
166/276 ;
166/278; 166/297; 166/308.2; 166/308.3; 175/72; 507/127; 507/140;
507/234; 507/269; 507/904 |
Current CPC
Class: |
C09K 8/80 20130101; C09K
8/68 20130101; Y10S 507/924 20130101 |
Class at
Publication: |
166/276 ;
166/278; 166/297; 175/072; 166/308.2; 166/308.3; 507/140; 507/127;
507/234; 507/269; 507/904 |
International
Class: |
E21B 43/04 20060101
E21B043/04; C09K 7/02 20060101 C09K007/02; E21B 43/26 20060101
E21B043/26; E21B 21/00 20060101 E21B021/00 |
Claims
1. A method comprising: providing a plurality of particulates, at
least one of which comprises a mineral surface; providing a
surface-treating reagent capable of modifying the stress-activated
reactivity of a mineral surface of a particulate; and allowing the
surface-treating reagent to modify the stress-activated reactivity
of at least a portion of the mineral surface of at least one
particulate.
2. The method of claim 1 wherein the surface-treating reagent
comprises a stress-activated reactivity-reducing reagent.
3. The method of claim 1 wherein the surface-treating reagent
comprises a stress-activated reactivity-increasing reagent.
4. The method of claim 1 wherein the surface-treating reagent
comprises a reagent for subsequent reactivity.
5. The method of claim 1 wherein the surface-treating reagent
comprises at least one of the following: a vinyl monomer; a diene;
a keto ester; an amine; a substituted amine hydrochloride; an
amide; an alcohol; an organosilane; an organotitaniate; an
organozirconate; a divalent metal cation; a trivalent metal cation;
a tetravalent metal cation; an ammonium halide; a quaternary
ammonium halide; an ammonium salt of an inorganic acid; an ammonium
salt of a carboxylic acid; an oligomeric material; a monomeric
material; an oil-wetting compound; a hydrolysable ester; or a
derivative thereof.
6. The method of claim 1 wherein the surface-treating reagent
comprises a resin and/or tackifying agent.
7. The method of claim 1 wherein the surface-treating reagent
comprises one or more polyamides.
8. The method of claim 1 wherein the surface-treating reagent
comprises a surfactant.
9. The method of claim 1 wherein the surface-treating reagent is
present in an amount in the range of from about 0.003 pounds to
about 0.5 pounds per square foot of surface area of the portion of
mineral surface of the particulates.
10. The method of claim 1 wherein the particulates comprise at
least one of the following: sand; bauxite; a fibrous material; a
ceramic material; a glass material; a polymer material; a
Teflon.RTM. material; nut shell pieces; seed shell pieces; fruit
pit pieces; wood; composite particulates; or a derivative
thereof.
11. A method of treating a subterranean formation comprising:
providing a treatment fluid that comprises a base fluid, a
plurality of particulates, at least one of which comprises a
mineral surface, and a surface-treating reagent capable of
modifying the stress-activated reactivity of a mineral surface of a
particulate; allowing the surface-treating reagent to modify the
stress-activated reactivity of at least a portion of the mineral
surface of at least one particulate; and introducing the treatment
fluid into the subterranean formation.
12. The method of claim 11 wherein the surface-treating reagent
comprises a stress-activated reactivity-reducing reagent.
13. The method of claim 11 wherein the surface-treating reagent
comprises a stress-activated reactivity-increasing reagent.
14. The method of claim 11 wherein the surface-treating reagent
comprises a reagent for subsequent reactivity.
15. The method of claim 11 wherein allowing the surface-treating
reagent to modify the stress-activated reactivity of at least a
portion of the mineral surface of at least one particulate occurs
prior to, during, or subsequent to introducing the treatment fluid
into the subterranean formation.
16. The method of claim 11 wherein introducing the treatment fluid
into the subterranean formation comprises introducing the treatment
fluid into the subterreanean formation at or above a pressure
sufficient to create or enhance one or more fractures in a portion
of the subterranean formation.
17. The method of claim 11 wherein introducing the treatment fluid
into the subterranean formation is part of a drilling
operation.
18. The method of claim 11 wherein introducing the treatment fluid
into the subterranean formation is part of a gravel-packing
operation.
19. The method of claim 11 wherein introducing the treatment fluid
into the subterranean formation is part of a perforating
operation.
20. The method of claim 11 wherein the surface-treating reagent
comprises a resin and/or tackifying agent.
21. The method of claim 11 wherein the surface-treating reagent
comprises one or more polyamides.
22. The method of claim 11 wherein the surface-treating reagent
comprises a surfactant.
23. A method of treating a subterranean formation comprising:
providing a treatment fluid that comprises a base fluid, and a
plurality of particulates, at least one of which comprises a
modified mineral surface; and introducing the treatment fluid into
the subterranean formation.
24. The method of claim 23 wherein at least a portion of the
mineral surface has been modified by a surface-treating reagent so
as to increase the tendency of the minerals resident on that
surface to undergo one or more chemical reactions.
25. The method of claim 23 wherein introducing the treatment fluid
into the subterranean formation comprises introducing the treatment
fluid into the subterreanean formation at or above a pressure
sufficient to create or enhance one or more fractures in a portion
of the subterranean formation.
26. The method of claim 23 wherein the surface-treating reagent
comprises a resin and/or tackifying agent.
27. The method of claim 23 wherein the surface-treating reagent
comprises one or more polyamides.
28. The method of claim 23 wherein the surface-treating reagent
comprises a surfactant.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to co-pending U.S. patent
application Ser. No. ______, Attorney Docket Number HES
2005-IP-017362U1, entitled "Methods of Modifying Fracture Faces and
other Surfaces in Subterranean Formations," filed on the same day,
the entirety of which is herein incorporated by reference.
BACKGROUND
[0002] The present invention relates to treatments useful in
subterranean operations, and more particularly, to methods of
modifying the surface stress-activated reactivity of proppant
particulates used in subterranean operations.
[0003] In the production of hydrocarbons from a subterranean
formation, the subterranean formation should be sufficiently
conductive to permit the flow of desirable fluids to a well bore
penetrating the formation. One type of treatment used in the art to
increase the conductivity of a subterranean formation is hydraulic
fracturing. Hydraulic fracturing operations generally involve
pumping a treatment fluid (e.g., a fracturing fluid or a "pad
fluid") into a well bore that penetrates a subterranean formation
at a sufficient hydraulic pressure to create or enhance one or more
pathways, or "fractures," in the subterranean formation. These
cracks generally increase the permeability of that portion of the
formation. The fluid may comprise particulates, often referred to
as "proppant particulates," that are deposited in the resultant
fractures. The proppant particulates are thought to help prevent
the fractures from fully closing upon the release of the hydraulic
pressure, forming conductive channels through which fluids may flow
to a well bore.
[0004] One problem that may affect fluid conductivity in the
formation after a fracturing treatment is the tendency for
particulates (e.g., formation fines, proppant particulates, etc.)
to flow back through the conductive channels in the subterranean
formation, which can, for example, clog the conductive channels
and/or damage the interior of the formation or equipment placed in
the formation. One well-known technique to prevent these problems
is to treat the associated portions of a subterranean formation
with a hardenable resin to hopefully consolidate any loose
particulates therein and to prevent their flow-back. Another
technique used to prevent flow-back problems, commonly referred to
as "gravel packing," involves the placement of a gravel screen in
the subterranean formation, which acts as a barrier that prevents
particulates from flowing into the well bore.
[0005] The surfaces of proppant particulates generally comprise one
or more minerals, which may react with other substances (e.g.,
water, minerals, treatment fluids, and the like) that reside in the
subterranean formation in chemical reactions caused, at least in
part, by conditions created by mechanical stresses on those
minerals (e.g., fracturing of mineral surfaces, compaction of
mineral particulates). These reactions are herein referred to as
"stress-activated reactions" or "stress-activated reactivity." One
type of these stress-activated reactions is diageneous reactions.
As used herein, the terms "diageneous reactions," "diageneous
reactivity," and "diagenesis" are defined to include chemical and
physical processes that move a portion of the mineral in a proppant
particulate and/or convert a portion of the mineral in a proppant
particulate into some other form in the presence of water. A
mineral that has been so moved or converted is herein referred to
as a "diageneous product." Any proppant particulate comprising a
mineral may be susceptible to these diageneous reactions, including
natural silicate minerals (e.g., quartz), man-made silicates and
glass materials, metal oxide minerals (both natural and man-made),
and the like.
[0006] Two of the principle mechanisms that diagenesis reactions
are thought to involve are pressure solution and precipitation
processes. Where two water-wetted mineral surfaces are in contact
with each other at a point under strain, the localized mineral
solubility near that point increases, causing the minerals to
dissolve. Minerals in solution may diffuse through the water film
outside of the region where the mineral surfaces are in contact
(e.g., the pore spaces of a proppant pack), where they may
precipitate out of solution. The dissolution and precipitation of
minerals in the course of these reactions may reduce the
conductivity of the proppant pack by, inter alia, clogging the pore
spaces in the proppant pack with mineral precipitate and/or
collapsing the pore spaces by dissolving solid minerals in the
"walls" of those pore spaces. In other instances, minerals on the
surface of a proppant particulate also may exhibit a tendency to
react with substances in formation fluids and/or treatment fluids
that are in contact with the particulates, such as water, gelling
agents (e.g., polysaccharides, biopolymers, etc.), and other
substances commonly found in these fluids, whose molecules may
become anchored to the mineral surface of the particulate. These
types of reactivity may, inter alia, further decrease the
conductivity of a subterranean formation through, inter alia, the
obstruction of conductive fractures in the formation by any
molecules that have become anchored to the proppant particulates
resident within those fractures.
[0007] Another problem that may affect the conductivity of a
formation arises as a result of the proppant particulates being
under pressure while in contact with the surfaces of the
subterranean formation, which can cause them to become embedded in
the surfaces of the formation. This may damage the formation by
forming "craters" therein. Among other things, these "craters" may
be a source of damage to the formation and/or reduce the
conductivity of the formation by reducing the width of fractures in
which the proppant particulates reside. It is a known practice in
the art to coat proppant particulates with resins and/or other
substances to increase the ability of the proppant to withstand the
pressure in a subterranean formation without becoming embedded in
the surfaces of the formation.
SUMMARY
[0008] The present invention relates to treatments useful in
subterranean operations, and more particularly, to methods of
modifying the surface stress-activated reactivity of proppant
particulates used in subterranean operations.
[0009] In one embodiment, the present invention provides a method
comprising: providing a plurality of particulates, at least one of
which comprises a mineral surface; providing a surface-treating
reagent capable of modifying the stress-activated reactivity of a
mineral surface of a particulate; and allowing the surface-treating
reagent to modify the stress-activated reactivity of at least a
portion of the mineral surface of at least one particulate.
[0010] In another embodiment, the present invention provides a
method of treating a subterranean formation comprising: providing a
treatment fluid that comprises a base fluid, a plurality of
particulates, at least one of which comprises a mineral surface,
and a surface-treating reagent capable of modifying the
stress-activated reactivity of a mineral surface of a particulate;
allowing the surface-treating reagent to modify the
stress-activated reactivity of at least a portion of the mineral
surface of at least one particulate; and introducing the treatment
fluid into the subterranean formation.
[0011] In another embodiment, the present invention provides a
method of treating a subterranean formation comprising: providing a
treatment fluid that comprises a base fluid and a plurality of
particulates, at least one of which comprises a modified mineral
surface; and introducing the treatment fluid into the subterranean
formation.
[0012] The features and advantages of the present invention will be
apparent to those skilled in the art. While numerous changes may be
made by those skilled in the art, such changes are within the
spirit of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] The present invention relates to treatments useful in
subterranean operations, and more particularly, to methods of
modifying the surface stress-activated reactivity of proppant
particulates used in subterranean operations. The methods of the
present invention are directed to modifying the surface
stress-activated reactivity of proppant particulates having a
mineral surface that are used in subterranean operations, and the
use of particulates having mineral surfaces that have been so
modified.
[0014] The term "mineral surface" as used herein refers to a
surface of a particulate that comprises one or more minerals and/or
has one or more minerals resident on at least a portion of its
outer surfaces. The minerals on the mineral surface of the
particulates treated herein may include, for example, natural
silicate minerals (e.g., quartz), man-made silicates and glass
materials, metal oxide minerals (both natural and man-made), and
the like. The mineral surfaces of particulates may interact with
each other, fluids resident in the subterranean formation (e.g.,
formation fluids, treatment fluids, etc.), and/or surfaces of the
subterranean formation (e.g., internal surfaces or "walls" of a
fracture, herein referred to as "fracture faces") in such a way
that affects conductivity of a subterranean formation. For example,
the mineral surfaces of particulates in a proppant pack may undergo
diageneous reactions that produce a product (e.g., a mineral
precipitate) that is capable of, inter alia, clogging the pore
spaces in the proppant pack. Thus, one object of the present
invention is to preserve and enhance conductivity within a
subterranean formation so that the maximum value of a fracturing
treatment with respect to increased conductivity may be realized.
Other objects of the present invention include, but are not limited
to, preventing build-up of filter cake and/or gel residue in
conductive channels (e.g., fractures) within a subterranean
formation, and preventing the embedment of particulates into the
surfaces of a subterranean formation.
[0015] The term "modifying the stress-activated reactivity of a
mineral surface" and its derivatives as used herein refer to
increasing or decreasing the tendency of a mineral surface to
undergo one or more stress-activated reactions, or attaching a
compound to the mineral surface that is capable of participating in
one or more subsequent reactions with a second compound. In some
embodiments, modifying the stress-activated reactivity of a mineral
surface may comprise increasing or decreasing the tendency of a
mineral surface to undergo diageneous reactions, or increasing or
decreasing the tendency of a mineral surface to chemically react
with one or more compounds (e.g., a gelling agent) in a fluid in
contact with the mineral surface. A mineral surface whose
reactivity has been modified according to this definition is herein
referred to as "a modified mineral surface." In certain embodiments
of the present invention, modifying the stress-activated reactivity
of a mineral surface may comprise depositing one or more compounds
on the mineral surface of a particulate that are capable of
affecting the ability of the mineral surface to interact with any
aqueous fluid that may be present in a subterranean formation, for
example, by hindering or preventing the water-wetting of that
mineral surface. Such compounds may be hydrophobic or hydrophilic
in nature. In certain embodiments, the one or more compounds may be
deposited so as to form an insulating film on the mineral
surface.
[0016] The methods of the present invention generally comprise
providing a plurality of particulates that comprise a modified
mineral surface, or providing a plurality of particulates and a
surface-treating reagent capable of modifying the stress-activated
reactivity of the mineral surface of the particulates. In some
embodiments, the modification may increase the tendency of a
mineral surface to undergo stress-activated reactions; in other
embodiments, the modification may lessen the tendency of a mineral
surface to undergo stress-activated reactions.
[0017] 1. Particulates
[0018] The particulates suitable for use in the present invention
comprise any particulate that comprises a mineral surface. It
should be understood that the term "particulate," as used in this
disclosure, includes all known shapes of materials including
substantially spherical materials, fibrous materials, polygonal
materials (such as cubic materials) and mixtures thereof. Suitable
particulates include, but are not limited to, sand, bauxite,
ceramic materials, glass materials (e.g., glass beads), polymer
materials, Teflon.RTM. materials, nut shell pieces, seed shell
pieces, cured resinous particulates comprising nut shell pieces,
cured resinous particulates comprising seed shell pieces, fruit pit
pieces, cured resinous particulates comprising fruit pit pieces,
wood, composite particulates and combinations thereof. Composite
particulates may also be suitable, suitable composite materials may
comprise a binder and a filler material wherein suitable filler
materials include silica, alumina, filmed carbon, carbon black,
graphite, mica, titanium dioxide, meta-silicate, calcium silicate,
kaolin, talc, zirconia, boron, fly ash, hollow glass microspheres,
solid glass, ground nut/seed shells or husks, saw dust, ground
cellulose fiber, and combinations thereof. The particulates may
have a size in the range of from about 2 to about 400 mesh, U.S.
Sieve Series. In particular embodiments, preferred particulates
size distribution ranges are one or more of 6/12 mesh, 8/16, 12/20,
16/30, 20/40, 30/50, 40/60, 40/70, or 50/70 mesh. Moreover, fibrous
materials that may or may not be used to bear the pressure of a
closed fracture, are often included in proppant and gravel
treatments.
[0019] 2. Suitable Surface-Treating Reagents
[0020] The surface-treating reagents utilized in the methods of the
present invention generally comprise any compound that is capable
of modifying the stress-activated reactivity of a mineral surface
(as defined above). The surface-treating reagent may comprise a
compound that increases or decreases the tendency of a mineral
surface to undergo one or more stress-activated reactions (e.g.,
diagenous reactions, reactions with gelling agent molecules, etc.),
or a compound that may is capable of undergoing a subsequent
reaction with another compound. The surface-treating reagent may
modify the stress-activated reactivity of a mineral surface in any
number of ways, depending on the type of reagent used. For example,
molecules of the surface-treating reagent may form covalent bonds
with molecules on the mineral surface, or interact with molecules
on the mineral surface via ionic interactions and/or van der Waals
interactions. In certain embodiments, the surface-treating reagent
may be present in an amount in the range of from about 0.003 pounds
to about 0.5 pounds per square foot of surface area of mineral
surface treated on the particulates. In certain embodiments, the
surface-treating reagent may be present in an amount in the range
of from about 0.03 pounds to about 0.12 pounds per square foot of
surface area of mineral surface treated on the particulates. The
type and amount of surface-treating reagents included in a
particular method of the present invention may depend upon, among
other factors, the chemical composition of formation fluids where
the particulates are to be placed, flow rate of those formation
fluids, the existing reactivity of the mineral surface, the desired
resultant reactivity of the mineral surface, temperature, and the
like.
[0021] a. Stress-Activated Reactivity-Reducing Reagents
[0022] In some embodiments, the surface-treating reagent may
comprise compounds that are capable of decreasing the tendency of a
mineral surface of a particulate to undergo one or more
stress-activated reactions (e.g., diagenous reactions, reactions
with gelling agent molecules, etc.). Such reagents are herein
referred to as "stress-activated reactivity-reducing reagents."
Suitable stress-activated reactivity-reducing reagents include, but
are not limited to, resins, tackifying agents, and other substances
that are capable of hindering or preventing the water-wetting of
the mineral surface. Stress-activated reactivity-reducing reagents
suitable for use in the present invention may be capable of
increasing the water contact angle of a surface by at least about
20 degrees. These stress-activated reactivity-reducing reagents may
be capable of performing these functions in any number of ways. In
certain embodiments, the reagent may react with the minerals on the
surfaces being treated to make them less susceptible to diagenous
reactions. In certain embodiments, the reagent may react with the
minerals on the surfaces being treated to make them less likely to
chemically react with one or more compounds (e.g., a gelling agent)
in a fluid in contact with the mineral surface. In certain
embodiments, the reagent may be deposited on the mineral surface to
form a barrier or film that hinders or prevents the mineral surface
from interacting with any aqueous fluid that may be present in the
subterranean formation.
[0023] i. Tackifying Agents
[0024] Tackifying agents suitable for use in the present invention
include non-aqueous tackifying agents, aqueous tackifying agents,
and silyl-modified polyamides. Certain such tackifying agents
suitable for use in the present invention may be capable of
increasing the water contact angle of a surface by at least about
20 degrees. One group of non-aqueous tackifying agents suitable for
use in the present invention comprises polyamides that are liquids
or in solution at the temperature of the particulates such that
they are, by themselves, non-hardening when placed in contact with
the particulates. An example of one such tackifying agent is a
condensation reaction product comprised of commercially available
polyacids and a polyamine. Such commercial products include
compounds such as mixtures of C.sub.36 dibasic acids containing
some trimer and higher oligomers and also small amounts of monomer
acids that are reacted with polyamines. Other polyacids include
trimer acids, synthetic acids produced from fatty acids, maleic
anhydride, acrylic acid, and the like. Such acid compounds are
commercially available from companies such as Witco Corporation,
Union Camp, Chemtall, and Emery Industries. The reaction products
are available from, for example, Champion Technologies, Inc. and
Witco Corporation. In certain embodiments, a non-aqueous tackifying
agent may comprise an isopropyl alcohol solution of about 3%
polyamides by volume of the solution. Additional compounds which
may be used as non-aqueous tackifying compounds include liquids and
solutions of, for example, polyesters, polycarbonates,
polycarbamates, natural resins such as shellac, and the like. Other
suitable non-aqueous tackifying agents are described in U.S. Pat.
No. 5,853,048 issued to Weaver, et al., U.S. Pat. No. 5,833,000
issued to Weaver, et al., U.S. Pat. No. 5,582,249 issued to Weaver,
et al., U.S. Pat. No. 5,775,425 issued to Weaver, et al., and U.S.
Pat. No. 5,787,986 issued to Weaver, et al., the relevant
disclosures of which are herein incorporated by reference. In
certain embodiments, the non-aqueous tackifying agent may be
present in an amount in the range of from about 0.003 pounds to
about 0.5 pounds per square foot of surface area of mineral surface
treated on the particulates. In certain embodiments, the
non-aqueous tackifying agent may be present in an amount in the
range of from about 0.03 pounds to about 0.12 pounds per square
foot of surface area of mineral surface treated on the
particulates.
[0025] Non-aqueous tackifying agents suitable for use in the
present invention may be either used such that they form a
non-hardening coating, or they may be combined with a
multifunctional material capable of reacting with the non-aqueous
tackifying agent to form a hardened coating. A "hardened coating"
as used herein means that the reaction of the tackifying compound
with the multifunctional material will result in a substantially
non-flowable reaction product that exhibits a higher compressive
strength in a consolidated agglomerate than the tackifying compound
alone with the particulates. In this instance, the non-aqueous
tackifying agent may function similarly to a hardenable resin.
Multifunctional materials suitable for use in the present invention
include, but are not limited to, aldehydes such as formaldehyde,
dialdehydes such as glutaraldehyde, hemiacetals or aldehyde
releasing compounds, diacid halides, dihalides such as dichlorides
and dibromides, polyacid anhydrides such as citric acid, epoxides,
furfuraldehyde, glutaraldehyde or aldehyde condensates and the
like, and combinations thereof. In some embodiments of the present
invention, the multifunctional material may be mixed with the
tackifying compound in an amount of from about 0.01% to about 50%
by weight of the tackifying compound to effect formation of the
reaction product. In some preferable embodiments, the compound is
present in an amount of from about 0.5% to about 1% by weight of
the tackifying compound. Suitable multifinctional materials are
described in U.S. Pat. No. 5,839,510 issued to Weaver, et al., the
relevant disclosure of which is herein incorporated by
reference.
[0026] Solvents suitable for use with the non-aqueous tackifying
agents of the present invention include any solvent that is
compatible with the non-aqueous tackifying agent and achieves the
desired viscosity effect. The solvents that can be used in the
present invention preferably include those having high flash points
(most preferably above about 125.degree. F.). Examples of solvents
suitable for use in the present invention include, but are not
limited to, butylglycidyl ether, dipropylene glycol methyl ether,
butyl bottom alcohol, dipropylene glycol dimethyl ether,
diethyleneglycol methyl ether, ethyleneglycol butyl ether,
methanol, butyl alcohol, isopropyl alcohol, diethyleneglycol butyl
ether, propylene carbonate, d'limonene, 2-butoxy ethanol, butyl
acetate, furfuryl acetate, butyl lactate, dimethyl sulfoxide,
dimethyl formamide, fatty acid methyl esters, and combinations
thereof.
[0027] Aqueous tackifying agents suitable for use in the present
invention are not significantly tacky when placed onto a mineral
surface, but are capable of being "activated" (that is
destabilized, coalesced and/or reacted) to transform the compound
into a sticky, tackifying compound at a desirable time. In some
embodiments, a pretreatment may be first contacted with the mineral
surface to prepare it to be coated with an aqueous tackifying
agent. Suitable aqueous tackifying agents are generally charged
polymers that comprise compounds that, when in an aqueous solvent
or solution, will form a non-hardening coating (by itself or with
an activator) and, when placed on a particulate, will increase the
continuous critical resuspension velocity of the particulate when
contacted by a stream of water. The aqueous tackifying agent, inter
alia, may enhance the grain-to-grain contact between individual
particulates (be they proppant particulates, formation fines, or
other particulates) and/or helping bring about the consolidation of
the particulates into a cohesive, flexible, and permeable mass. In
certain embodiments, the aqueous tackifying agent may be present in
an amount in the range of from about 0.003 pounds to about 0.5
pounds per square foot of surface area of mineral surface treated
on the particulates. In certain embodiments, the aqueous tackifying
agent may be present in an amount in the range of from about 0.03
pounds to about 0.12 pounds per square foot of surface area of
mineral surface treated on the particulates.
[0028] Examples of aqueous tackifying agents suitable for use in
the present invention include, but are not limited to, acrylic acid
polymers, acrylic acid ester polymers, acrylic acid derivative
polymers, acrylic acid homopolymers, acrylic acid ester
homopolymers (such as poly(methyl acrylate), poly (butyl acrylate),
and poly(2-ethylhexyl acrylate)), acrylic acid ester co-polymers,
methacrylic acid derivative polymers, methacrylic acid
homopolymers, methacrylic acid ester homopolymers (such as
poly(methyl methacrylate), poly(butyl methacrylate), and
poly(2-ethylhexyl methacryate)), acrylamido-methyl-propane
sulfonate polymers, acrylamido-methyl-propane sulfonate derivative
polymers, acrylamido-methyl-propane sulfonate co-polymers, and
acrylic acid/acrylamido-methyl-propane sulfonate co-polymers and
combinations thereof. Methods of determining suitable aqueous
tackifying agents and additional disclosure on aqueous tackifying
agents can be found in U.S. patent application Ser. No. 10/864,061,
filed Jun. 9, 2004, and U.S. patent application Ser. No.
10/864,618, filed Jun. 9, 2004, the relevant disclosures of which
are hereby incorporated by reference.
[0029] Silyl-modified polyamide compounds suitable for use as a
surface-treating reagent in the methods of the present invention
may be described as substantially self-hardening compositions that
are capable of at least partially adhering to surfaces in the
unhardened state, and that are further capable of self-hardening
themselves to a substantially non-tacky state to which individual
particulates will not adhere to, for example, in formation or
proppant pack pore throats. Such silyl-modified polyamides may be
based, for example, on the reaction product of a silating compound
with a polyamide or a mixture of polyamides. The polyamide or
mixture of polyamides may be one or more polyamide intermediate
compounds obtained, for example, from the reaction of a polyacid
(e.g., diacid or higher) with a polyamine (e.g., diamine or higher)
to form a polyamide polymer with the elimination of water. Other
suitable silyl-modified polyamides and methods of making such
compounds are described in U.S. Pat. No. 6,439,309 issued to
Matherly, et al., the relevant disclosure of which is herein
incorporated by reference. In certain embodiments, the
silyl-modified polyamide compound may be present in an amount in
the range of from about 0.003 pounds to about 0.5 pounds per square
foot of surface area of mineral surface treated on the
particulates. In certain embodiments, the silyl-modified polyamide
compound may be present in an amount in the range of from about
0.03 pounds to about 0.12 pounds per square foot of surface area of
mineral surface treated on the particulates.
[0030] ii. Suitable Resins
[0031] In some embodiments, the surface-treating reagent may
comprise a resin. Resins suitable for use in the present invention
include all resins known and used in the art. Certain resins
suitable for use in the present invention may be capable of
increasing the water contact angle of a surface by at least about
20 degrees. Many such resins are commonly used in subterranean
operations.
[0032] One resin-type coating material suitable for use in the
methods of the present invention is a two-component epoxy based
resin comprising a hardenable resin component and a hardening agent
component. The hardenable resin component is comprised of a
hardenable resin and an optional solvent. The solvent may be added
to the resin to reduce its viscosity for ease of handling, mixing
and transferring. Factors that may affect the decision to include a
solvent include geographic location of the well and the surrounding
weather conditions. An alternate way to reduce the viscosity of the
liquid hardenable resin is to heat it. This method avoids the use
of a solvent altogether, which may be desirable in certain
circumstances. The second component is the liquid hardening agent
component, which is comprised of a hardening agent, a silane
coupling agent, a surfactant, an optional hydrolyzable ester for,
among other things, breaking gelled fracturing fluid films on the
proppant particles, and an optional liquid carrier fluid for, among
other things, reducing the viscosity of the liquid hardening agent
component.
[0033] Examples of hardenable resins that can be used in the
hardenable resin component include, but are not limited to, organic
resins such as bisphenol A-diglycidyl ether resins, butoxymethyl
butyl glycidyl ether resins, bisphenol A-epichlorohydrin resins,
polyepoxide resins, novolak resins, polyester resins,
phenol-aldehyde resins, urea-aldehyde resins, furan resins,
urethane resins, glycidyl ether resins, and combinations thereof.
The hardenable resin used may be included in the hardenable resin
component in an amount in the range of from about 60% to about 100%
by weight of the hardenable resin component. In some embodiments,
the hardenable resin used may be included in the hardenable resin
component in an amount of about 70% to about 90% by weight of the
hardenable resin component.
[0034] Any solvent that is compatible with the hardenable resin and
achieves the desired viscosity effect is suitable for use in the
hardenable resin component in certain embodiments of the present
invention. Some preferred solvents are those having high flash
points (e.g., about 125.degree. F.) because of, among other things,
environmental and safety concerns; such solvents include butyl
lactate, butylglycidyl ether, dipropylene glycol methyl ether,
dipropylene glycol dimethyl ether, dimethyl formamide,
diethyleneglycol methyl ether, ethyleneglycol butyl ether,
diethyleneglycol butyl ether, propylene carbonate, methanol, butyl
alcohol, d'limonene, fatty acid methyl esters, and combinations
thereof. Other preferred solvents include aqueous dissolvable
solvents such as, methanol, isopropanol, butanol, glycol ether
solvents, and combinations thereof. Suitable glycol ether solvents
include, but are not limited to, diethylene glycol methyl ether,
dipropylene glycol methyl ether, 2-butoxy ethanol, ethers of a
C.sub.2 to C.sub.6 dihydric alkanol containing at least one C.sub.1
to C.sub.6 alkyl group, mono ethers of dihydric alkanols,
methoxypropanol, butoxyethanol, hexoxyethanol, and isomers thereof.
Aqueous solvents also may be used in the methods of the present
invention. In certain embodiments wherein an aqueous solvent is
used, certain additives may be used, among other purposes, to aid
in dispersing the resin in the aqueous solution. Selection of an
appropriate solvent is dependent on, inter alia, the resin
composition chosen.
[0035] As described above, use of a solvent in the hardenable resin
component is optional but may be desirable to reduce the viscosity
of the hardenable resin component for ease of handling, mixing, and
transferring. In some embodiments, the amount of the solvent used
in the hardenable resin component is in the range of from about
0.1% to about 30% by weight of the hardenable resin component.
Optionally, the hardenable resin component may be heated to reduce
its viscosity, in place of, or in addition to, using a solvent.
[0036] Examples of the hardening agents that can be used in the
liquid hardening agent component in certain embodiments of the
present invention include, but are not limited to, piperazine,
derivatives of piperazine (e.g., aminoethylpiperazine), 2H-pyrrole,
pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyrimidine,
pyridazine, indolizine, isoindole, 3H-indole, indole, 1H-indazole,
purine, 4H-quinolizine, quinoline, isoquinoline, phthalazine,
naphthyridine, quinoxaline, quinazoline, 4H-carbazole, carbazole,
.beta.-carboline, phenanthridine, acridine, phenathroline,
phenazine, imidazolidine, phenoxazine, cinnoline, pyrrolidine,
pyrroline, imidazoline, piperidine, indoline, isoindoline,
quinuclindine, morpholine, azocine, azepine, 2H-azepine,
1,3,5-triazine, thiazole, pteridine, dihydroquinoline, hexa
methylene imine, indazole, amines, aromatic amines, polyamines,
aliphatic amines, cyclo-aliphatic amines, amides, polyamides,
2-ethyl-4-methyl imidazole, 1,1,3-trichlorotrifluoroacetone, and
combinations thereof. The chosen hardening agent often effects the
range of temperatures over which a hardenable resin is able to
cure. By way of example and not of limitation, in subterranean
formations having a temperature from about 60.degree. F. to about
250.degree. F., amines and cyclo-aliphatic amines such as
piperidine, triethylamine, N,N-dimethylaminopyridine,
benzyldimethylamine, tris(dimethylaminomethyl) phenol, and
2-(N.sub.2N-dimethylaminomethyl)phenol may be used. In subterranean
formations having higher temperatures, 4,4'-diaminodiphenyl sulfone
may be a suitable hardening agent. Hardening agents that comprise
piperazine or a derivative of piperazine have been shown capable of
curing various hardenable resins from temperatures as low as about
70.degree. F. to as high as about 350.degree. F. The hardening
agent used may be included in the liquid hardening agent component
in an amount sufficient to consolidate the coated particulates. In
some embodiments of the present invention, the hardening agent used
may be included in the liquid hardenable resin component in the
range of from about 40% to about 60% by weight of the liquid
hardening agent component. In some embodiments, the hardenable
resin used may be included in the hardenable resin component in an
amount of about 45% to about 55% by weight of the liquid hardening
agent component.
[0037] The silane coupling agent may be used, among other things,
to act as a mediator to help bond the resin to formation
particulates and/or proppant. Examples of suitable silane coupling
agents include, but are not limited to,
N-.beta.-(aminoethyl)-.gamma.-aminopropyl trimethoxysilane,
N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,
3-glycidoxypropyltrimethoxysilane, and combinations thereof. The
silane coupling agent used may be included in the liquid hardening
agent component in an amount capable of sufficiently bonding the
resin to the mineral surface. In some embodiments of the present
invention, the silane coupling agent used may be included in the
liquid hardenable resin component in the range of from about 0.1%
to about 3% by weight of the liquid hardening agent component.
[0038] Any surfactant compatible with the hardening agent and
capable of facilitating the contacting of the resin onto mineral
surfaces of the particulates may be used in the hardening agent
component in certain embodiments of the present invention. Such
surfactants include, but are not limited to, an alkyl phosphonate
surfactant (e.g., a C.sub.12-C.sub.22 alkyl phosphonate
surfactant), an ethoxylated nonyl phenol phosphate ester, one or
more cationic surfactants, and one or more nonionic surfactants.
Mixtures of one or more cationic and nonionic surfactants also may
be suitable. Examples of such surfactant mixtures are described in
U.S. Pat. No. 6,311,773 issued to Todd et al. on Nov. 6, 2001, the
relevant disclosure of which is incorporated herein by reference.
The surfactant or surfactants used may be included in the liquid
hardening agent component in an amount in the range of from about
1% to about 10% by weight of the liquid hardening agent
component.
[0039] While not required, examples of hydrolysable esters that can
be used in the hardening agent component in certain embodiments of
the present invention include, but are not limited to, a mixture of
dimethylglutarate, dimethyladipate, dimethylsuccinate, sorbitol,
catechol, dimethylthiolate, methyl salicylate, dimethyl salicylate,
dimethylsuccinate, terbutylhydroperoxide, and combinations thereof.
When used, a hydrolyzable ester may be included in the hardening
agent component in an amount in the range of from about 0.1% to
about 3% by weight of the hardening agent component. In some
embodiments a hydrolysable ester is included in the hardening agent
component in an amount in the range of from about 1% to about 2.5%
by weight of the hardening agent component.
[0040] Use of a diluent or liquid carrier fluid in the hardenable
resin composition is optional and may be used to reduce the
viscosity of the hardenable resin component for ease of handling,
mixing and transferring. Any suitable carrier fluid that is
compatible with the hardenable resin and achieves the desired
viscosity effects is suitable for use in the present invention.
Some suitable liquid carrier fluids are those having high flash
points (e.g., about 125.degree. F.) because of, among other things,
environmental and safety concerns; such solvents include butyl
lactate, butylglycidyl ether, dipropylene glycol methyl ether,
dipropylene glycol dimethyl ether, dimethyl formamide,
diethyleneglycol methyl ether, ethyleneglycol butyl ether,
diethyleneglycol butyl ether, propylene carbonate, methanol, butyl
alcohol, d'limonene, fatty acid methyl esters, and combinations
thereof. Other suitable liquid carrier fluids include aqueous
dissolvable solvents such as, methanol, isopropanol, butanol,
glycol ether solvents, and combinations thereof. Suitable glycol
ether liquid carrier fluids include, but are not limited to,
diethylene glycol methyl ether, dipropylene glycol methyl ether,
2-butoxy ethanol, ethers of a C.sub.2 to C.sub.6 dihydric alkanol
containing at least one C.sub.1 to C.sub.6 alkyl group, mono ethers
of dihydric alkanols, methoxypropanol, butoxyethanol,
hexoxyethanol, and isomers thereof. Selection of an appropriate
liquid carrier fluid is dependent on, inter alia, the resin
composition chosen.
[0041] Another resin suitable for use in the methods of the present
invention are furan-based resins. Suitable furan-based resins
include, but are not limited to, furfuryl alcohol resins, mixtures
furfuryl alcohol resins and aldehydes, and a mixture of furan
resins and phenolic resins. A furan-based resin may be combined
with a solvent to control viscosity if desired. Suitable solvents
for use with furan-based resins include, but are not limited to
2-butoxy ethanol, butyl lactate, butyl acetate, tetrahydrofurfuryl
methacrylate, tetrahydrofurfuryl acrylate, esters of oxalic, maleic
and succinic acids, and furfuryl acetate.
[0042] Another resin suitable for use in the methods of the present
invention is a phenolic-based resin. Suitable phenolic-based resins
include, but are not limited to, terpolymers of phenol, phenolic
formaldehyde resins, and a mixture of phenolic and furan resins. A
phenolic-based resin may be combined with a solvent to control
viscosity if desired. Suitable solvents for use in the
phenolic-based consolidation fluids of the present invention
include, but are not limited to butyl acetate, butyl lactate,
furfuryl acetate, and 2-butoxy ethanol.
[0043] Another resin suitable for use in the methods of the present
invention is a HT epoxy-based resin. Suitable HT epoxy-based
components include, but are not limited to, bisphenol
A-epichlorohydrin resins, polyepoxide resins, novolac resins,
polyester resins, glycidyl ethers and mixtures thereof. An HT
epoxy-based resin may be combined with a solvent to control
viscosity if desired. Suitable solvents for use with the HT
epoxy-based resins of the present invention are those solvents
capable of substantially dissolving the HT epoxy-resin chosen for
use in the consolidation fluid. Such solvents include, but are not
limited to, dimethyl sulfoxide and dimethyl formamide. A co-solvent
such as a dipropylene glycol methyl ether, dipropylene glycol
dimethyl ether, dimethyl formamide, diethylene glycol methyl ether,
ethylene glycol butyl ether, diethylene glycol butyl ether,
propylene carbonate, d'limonene and fatty acid methyl esters, may
also be used in combination with the solvent.
[0044] Another resin-type coating material suitable for use in the
methods of the present invention is a phenol/phenol
formaldehyde/furfuryl alcohol resin comprising from about 5% to
about 30% phenol, from about 40% to about 70% phenol formaldehyde,
from about 10 to about 40% furfuryl alcohol, from about 0.1% to
about 3% of a silane coupling agent, and from about 1% to about 15%
of a surfactant. In the phenol/phenol formaldehyde/furfuryl alcohol
resins suitable for use in the methods of the present invention,
suitable silane coupling agents include, but are not limited to,
N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,
3-glycidoxypropyltrimethoxysilane, and
n-.beta.-(aminoethyl)-.gamma.-aminopropyl trimethoxysilane.
Suitable surfactants include, but are not limited to, an
ethoxylated nonyl phenol phosphate ester, mixtures of one or more
cationic surfactants, and one or more non-ionic surfactants and an
alkyl phosphonate surfactant.
[0045] In certain embodiments, the resin may be present in an
amount in the range of from about 0.003 pounds to about 0.5 pounds
per square foot of surface area of mineral surface treated on the
particulates. In certain embodiments, the resin may be present in
an amount in the range of from about 0.03 pounds to about 0.12
pounds per square foot of surface area of mineral surface treated
on the particulates.
[0046] iii. Surfactants
[0047] In some embodiments of the present invention, the
surface-treating reagent may comprise a surfactant. The selection
of an appropriate surfactant to hinder or prevent stress-activated
reactions on a mineral surface may depend on, among other factors,
the type of minerals present on that surface and/or the composition
of any fluids resident in a subterranean formation where the
particulates are to be placed. For example, in certain embodiments,
suitable surfactants may comprise long-chain alkyl sulfates wherein
the alkyl chain comprises from about 6 carbon atoms to about 21
carbon atoms. An example of one suitable long-chain alkyl sulfate
is lauryl sulfate. Other suitable surfactants may comprise one or
more degradable surfactants, wherein the surfactant molecules are
derived from degradable polymers and contain a backbone with
repeating units of degradable groups, such as esters or other
derivatives, for example, such as polycarbonates, polyacetals,
poly(orthoesters), or polyesteramides as the degradable hydrophobic
block or tail in the surfactant molecule attached to the
hydrophilic polymeric block or head group. Other suitable
surfactants may include reactive surfactants, such as non-migratory
surfactants or "surfmers," which comprise surfactants that carry
one or more polymerizable functional groups. Examples of reactive
surfactants suitable for use in the present invention are described
in U.S. Patent Application Publication Number 2005/0070679, filed
Aug. 30, 2004, the relevant disclosure of which is hereby
incorporated by reference. The surfactant may be present in a
treatment fluid utilized in the present invention in any amount
that does not adversely affect the properties of the particulates.
In certain embodiments, the surfactant may be present in an amount
in the range of from about 0.01% to about 10% by volume of a
treatment fluid comprising the particulates being treated. In
certain embodiments, the surfactant may be present in an amount in
the range of from about 2% to about 5% by volume of a treatment
fluid comprising the particulates being treated.
[0048] iv. Other Reagents
[0049] In some embodiments, the surface-treating reagent may
comprise other compounds that are capable of hindering or
preventing the water-wetting of a mineral surface. Examples of
suitable compounds include, but are not limited to, vinyl monomers,
dienes, keto esters, amines, substituted amine hydrochlorides,
amides, alcohols, organosilanes, organotitaniates,
organozirconates, trivalent metal cations, tetravalent metal
cations, ammonium halides, quaternary ammonium halides, ammonium
salts of inorganic acids, ammonium salts of carboxylic acids,
oligomeric materials, monomeric materials, oil-wetting compounds,
and derivatives thereof. In some embodiments, the surface-treating
reagent may comprise lecithin. In some embodiments, the
surface-treating reagent may comprise a chlorosilyl group
containing compound and an alkylsilane, or the reaction products
thereof. In some embodiments, the surface-treating reagent may
comprise an organofunctional silane and an aryl acid halide, or the
reaction products thereof. Examples of suitable organofunctional
silanes for these embodiments include, but are not limited to,
aminofunctional silanes, ureidofunctional silanes, and
epoxyfunctional silanes. Examples of suitable aryl acid halides for
these embodiments include, but are not limited to, phthaloyl
chloride, isophthaloyl chloride, and terphthaloyl chloride. In some
embodiments, the surface-treating reagent may comprise one or more
polymers of a fluoroalkyl group containing silane compound wherein
the polymers include one or more dimmers or trimers. In certain
embodiments, the reagent may be present in an amount in the range
of from about 0.003 pounds to about 0.5 pounds per square foot of
surface area of mineral surface treated on the particulates. In
certain embodiments, the reagent may be present in an amount in the
range of from about 0.03 pounds to about 0.12 pounds per square
foot of surface area of mineral surface treated on the
particulates.
[0050] b. Stress-Activated Reactivity-Increasing Reagents
[0051] In some embodiments, the surface-treating reagent may
comprise compounds that are capable of increasing the tendency of a
mineral surface of a particulate to undergo one or more
stress-activated reactions (e.g., diagenous reactions, reactions
with gelling agent molecules, etc.). Such reagents are herein
referred to as "stress-activated reactivity-increasing reagents."
Stress-activated reactivity-increasing reagents may comprise
compounds that exhibit a tendency to be hydrolyzed in the presence
of water under stress at low temperatures. Examples of such
compounds may include, but are not limited to, hydrolysable esters
(e.g., ceramics), polyolefins, unsaturated fats, surfactants, vinyl
monomers, dienes, keto esters, amines, substituted amine
hydrochlorides, amides, alcohols, organosilanes, organotitaniates,
organozirconates, divalent metal cations, trivalent metal cations,
tetravalent metal cations, ammonium halides, quaternary ammonium
halides, ammonium salts of inorganic acids, ammonium salts of
carboxylic acids, oligomeric materials, monomeric materials, and
derivatives thereof. These stress-activated reactivity-increasing
reagents may be capable of increasing chemical reactions in any
number of ways. In certain embodiments, the reagent may react with
the minerals on the surface being treated to make them more
susceptible to stress-activated reactions. In other embodiments,
the reagent may be deposited on the mineral surface to form a
barrier or film that itself is more likely to participate in
stress-activated reactions. In some embodiments of the present
invention, these compounds may be placed in contact with the
mineral surface of the proppant material so as to encourage
subsequent chemical reactions that will generate a product (e.g., a
diageneous product), which may be used for some subsequent purpose
downhole. For example, a diageneous product (e.g., a mineral
precipitate) may be capable of consolidating proppant or formation
fines, or forming a plug that is capable of diverting and/or
isolating the flow of formation fluids (e.g., water) or other
treatment fluids in a portion of the subterranean formation. In
certain embodiments, the reactivity-increasing reagent may be
present in an amount in the range of from about 0.003 pounds to
about 0.5 pounds per square foot of surface area of mineral surface
treated on the particulates. In certain embodiments, the
reactivity-increasing reagent may be present in an amount in the
range of from about 0.03 pounds to about 0.12 pounds per square
foot of surface area of mineral surface treated on the
particulates.
[0052] C. Reagents for Subsequent Reactivity
[0053] In some embodiments, the surface-treating reagent may
comprise a compound that may be attached to the mineral surface for
participation in one or more subsequent reactions with a second
compound, or a reagent that reacts to form a product compound that
may be so attached to the mineral surface. Such reagents are herein
referred to as "reagents for subsequent reactivity." One example of
a subsequent reaction in which these attached compounds may
participate is depolymerization. Examples of compounds that may be
attached to the mineral surface to participate in subsequent
reactions include, but are not limited to, catalysts, guar gums,
polyolefins, unsaturated fats, surfactants, one or more vinyl
monomers, dienes, keto esters, amines, substituted amine
hydrochlorides, amides, alcohols, organosilanes, organotitaniates,
organozirconates, divalent metal cations, trivalent metal cations,
tetravalent metal cations, ammonium halides, quaternary ammonium
halides, ammonium salts of inorganic acids, ammonium salts of
carboxylic acids, oligomeric materials, monomeric materials,
oil-wetting compounds, and derivatives thereof. Any of these
attached compounds may contain one or more functional groups, which
may be independently reactive prior to, during, or subsequent to
their use in the methods of the present invention. In certain
embodiments, the reagent for subsequent reactivity may be present
in an amount in the range of from about 0.003 pounds to about 0.5
pounds per square foot of surface area of mineral surface treated
on the particulates. In certain embodiments, the reagent for
subsequent reactivity may be present in an amount in the range of
from about 0.03 pounds to about 0.12 pounds per square foot of
surface area of mineral surface treated on the particulates.
[0054] In certain embodiments of the present invention, the
surface-treating reagent may be encapsulated with various
materials, which, among other things, delays its reaction with the
mineral surface and/or other substances present. Solid
surface-treating reagents can be encapsulated by spray coating a
variety of materials thereon. Such coating materials include, but
are not limited to, waxes, drying oils such as tung oil and linseed
oil, polyurethanes and cross-linked partially hydrolyzed
polyacrylics. The surface-treating reagent may also be encapsulated
in the form of an aqueous solution contained within a particulate
porous solid material which remains dry and free flowing after
absorbing an aqueous solution and through which the aqueous
solution slowly diffuses. Examples of such particulate porous solid
materials include, but are not limited to, diatomaceous earth,
zeolites, silica, alumina, metal salts of alumino-silicates, clays,
hydrotalcite, styrene-divinylbenzene based materials, cross-linked
polyalkylacrylate esters and cross-linked modified starches. To
provide additional delay to the surface-treating reagents
encapsulated in a particulate porous solid material described
above, an external coating of a polymeric material through which an
aqueous solution slowly diffuses can be placed on the porous solid
material. Examples of such polymeric materials include, but are not
limited to, EDPM rubber, polyvinyldichloride (PVDC), nylon, waxes,
polyurethanes and cross-linked partially hydrolyzed acrylics.
[0055] 3. Methods of Treating and Use
[0056] In practicing certain embodiments of the present invention,
the surface-treating reagent may be allowed to modify the
stress-activated reactivity of the mineral surface of a plurality
of particulates using any method known in the art. This may be
accomplished in treatments performed prior to transporting the
particulates to a job site, or in a treatment performed
"on-the-fly." The term "on-the-fly" is used herein to mean that one
flowing stream comprising particulates is continuously introduced
into another flowing stream comprising the surface-treating reagent
so that the streams are combined and mixed while continuing to flow
as a single stream as part of the on-going treatment at the job
site. Such mixing can also be described as "real-time" mixing. One
such on-the-fly mixing method would involve continuously conveying
the particulates and the surface-treating reagent to a mixing
vessel, for example, using a sand screw. Once inside the mixing
vessel, the particulates would be contacted with the
surface-treating reagent and continuously removed from the mixing
vessel. In that situation, the sand screw could be used both to aid
in mixing the particulates, be they gravel, proppant, or some other
particulates, with the surface-treating reagent and to remove the
surface-treating reagent from the mixing tank. As is well
understood by those skilled in the art, batch or partial batch
mixing may also be used to accomplish such coating at a well site
just prior to introducing the particulates into a subterranean
formation.
[0057] In some embodiments, the surface-treating reagent may be
allowed to modify the stress-activated reactivity of the mineral
surface of a particulate by placing it in a solution and/or
treatment fluid that comprises the particulate, which may may be
done prior to, during, or subsequent to introducing that solution
and/or fluid into a subterranean formation or well bore. Other
suitable methods for allowing the surface-treating reagent to
modify the stress-activated reactivity of the mineral surface of a
particulate include, but are not limited to, methods utilizing a
dry mixer and solvent extraction methods. In an embodiment of the
present invention involving a solvent extraction technique, the
surface-treating reagent is diluted into a solvent or blend of
solvents to provide certain fluid properties (e.g., viscosity) that
facilitate transfer, metering, and mixing of the surface-treating
reagent with the particulates being treated. However, the solvents
are chosen from those that are very water soluble, with water being
preferred in certain embodiments. Another example of a suitable
water-soluble solvent is isopropyl alcohol. In certain embodiments,
a mixture of a fatty polyamide may be diluted in the solution,
among other purposes, to reduce viscosity. The solution comprising
the surface-treating reagent then may be coated onto the mineral
surface of the particulates by adding the solution to the
particulates and stirring (or mulling) until the mixture is
uniform. The treated particulates then may be introduced to a
water-based fluid that extracts the solvent from the treated
particulates, leaving behind an insoluble material that, among
other things, may enhance the modification of the stress-activated
reactivity of the treated mineral surface (e.g., further decrease
the tendency of the mineral surface to undergo chemical reactions).
In some embodiments of the present invention, it may be desirable
to perform some additional treatment or action on the particulate
prior to, during, or subsequent to allowing the surface-treating
reagent to modify the stress-activated reactivity of at least a
portion of a mineral surface of the particulate. For example, the
mineral surface of the particulate may be heated, inter alia, in
order to permit the surface-treating reagent to modify the
stress-activated reactivity of the mineral surface of the
particulate. In certain embodiments, at least a portion of the
particulates utilized in the methods of the present invention may
comprise a modified mineral surface, i.e., a mineral surface that
has been modified in one or more prior treatments.
[0058] The methods of the present invention may be utilized in a
variety of subterranean operations known in the art. Suitable
subterreanean operations include drilling operations, pre-pad
treatments, fracturing operations, gravel-packing operations,
frac-packing operations, perforation operations, and the like. In
certain embodiments, particulates treated utilizing the methods of
the present invention may be introduced into the subterranean
formation as a component of a treatment fluid (e.g., a fracturing
fluid). These treatment fluids generally comprise a base fluid,
which may be aqueous or non-aqueous, or a mixture thereof. Where
the base fluid is aqueous, it may comprise fresh water, salt water
(e.g., water containing one or more salts dissolved therein), brine
(e.g., saturated salt water), or seawater. The water can be from
any source, provided that it does not contain an excess of
compounds that may adversely affect other components in the
treatment fluid. Where the base fluid is non-aqueous, the base
fluid may comprise any number of organic liquids. Examples of
suitable organic liquids include, but are not limited to, mineral
oils, synthetic oils, esters, and the like. Any organic liquid in
which a water solution of salts can be emulsified also may be
suitable for use as a base fluid in the methods of the present
invention.
[0059] Suitable treatment fluids may take on a variety of physical
forms, including aqueous gels, viscoelastic surfactant gels, oil
gels, foamed gels, and emulsions. Suitable aqueous gels are
generally comprised of water and one or more gelling agents.
Suitable emulsions can be comprised of two immiscible liquids such
as an aqueous liquid or gelled liquid and a hydrocarbon. Foams can
be created by the addition of a gas, such as carbon dioxide or
nitrogen. In certain embodiments of the present invention, the
treatment fluids are aqueous gels comprised of water, a gelling
agent for gelling the water and increasing its viscosity, and,
optionally, a crosslinking agent for crosslinking the gel and
further increasing the viscosity of the treatment fluid. The
increased viscosity of the gelled, or gelled and cross-linked,
treatment fluid, inter alia, may reduce fluid loss and/or allow the
treatment fluid to transport increased quantities of proppant
particulates.
[0060] The treatment fluids utilized in some embodiments of the
present invention also may comprise one or more of a variety of
well-known additives, such as gel stabilizers, breakers, fluid loss
control additives, acids, corrosion inhibitors, catalysts, clay
stabilizers, biocides, salts, friction reducers, surfactants,
solubilizers, pH adjusting agents, additives for preventing gas
hydrates (e.g., ethylene glycol, methanol), and the like. In those
embodiments utilizing a treatment fluid, the particulates may be
present in the treatment fluid in any amount that the treatment
fluid is capable of suspending. In certain embodiments, the
particulates may be present in a treatment fluid in an amount in
the range of from about 0.5 ppg to about 18 ppg by volume of the
treatment fluid.
[0061] The present invention is well adapted to attain the ends and
advantages mentioned as well as those that are inherent therein.
While numerous changes may be made by those skilled in the art,
such changes are encompassed within the spirit of this invention as
defined by the appended claims. The terms in the claims have their
plain, ordinary meaning unless otherwise explicitly and clearly
defined by the patentee.
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