U.S. patent application number 11/484427 was filed with the patent office on 2008-01-17 for methods for coating particulates with tackifying compounds.
This patent application is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to Bobby K. Bowles, Philip D. Nguyen, Billy F. Slabaugh, Jimmie D. Weaver.
Application Number | 20080011476 11/484427 |
Document ID | / |
Family ID | 38573328 |
Filed Date | 2008-01-17 |
United States Patent
Application |
20080011476 |
Kind Code |
A1 |
Nguyen; Philip D. ; et
al. |
January 17, 2008 |
Methods for coating particulates with tackifying compounds
Abstract
At least one method is provided comprising: providing a
tackifying compound and at least one surfactant; mixing the
surfactant with the tackifying compound to form a tackifying
compound surfactant mixture; coating the tackifying compound
surfactant mixture onto particulates to form coated particulates;
mixing the coated particulates into a treatment fluid; and placing
the treatment fluid into a subterranean formation.
Inventors: |
Nguyen; Philip D.; (Duncan,
OK) ; Weaver; Jimmie D.; (Duncan, OK) ;
Bowles; Bobby K.; (Comanche, OK) ; Slabaugh; Billy
F.; (Duncan, OK) |
Correspondence
Address: |
ROBERT A. KENT
P.O. BOX 1431
DUNCAN
OK
73536
US
|
Assignee: |
Halliburton Energy Services,
Inc.
|
Family ID: |
38573328 |
Appl. No.: |
11/484427 |
Filed: |
July 11, 2006 |
Current U.S.
Class: |
166/276 ;
166/280.2; 166/281; 166/295; 427/221; 507/924 |
Current CPC
Class: |
C09K 8/805 20130101;
C09K 8/68 20130101 |
Class at
Publication: |
166/276 ;
166/281; 166/280.2; 507/924; 427/221; 166/295 |
International
Class: |
E21B 43/02 20060101
E21B043/02; E21B 43/267 20060101 E21B043/267 |
Claims
1. A method comprising: providing a tackifying compound having a
tackiness and at least one surfactant; mixing the surfactant with
the tackifying compound to form a tackifying compound surfactant
mixture, wherein the tackiness of the tackifying compound in the
tackifying compound surfactant mixture is at least temporarily
reduced; coating the tackifying compound surfactant mixture onto
particulates to form coated particulates; mixing the coated
particulates into a treatment fluid; and placing the treatment
fluid into a subterranean formation.
2. The method of claim 1 wherein the tackifying compound is a
non-aqueous tackifying compound.
3. The method of claim 2 wherein the non-aqueous tackifying
compound comprises polyamides that are liquids or in solution at
the temperature of the subterranean formation.
4. The method of claim 2 wherein the non-aqueous tackifying
compound is selected from the group consisting of: a polyester, a
polycarbonate, polycarbamate, a natural resin, and shellac.
5. The method of claim 2 wherein the non-aqueous tackifying
compound comprises a multifunctional material capable of reacting
with the non-aqueous tackifying compound to form a hardened
coating.
6. The method of claim 5 wherein the multifunctional material is
selected from the group consisting of: an aldehyde; a dialdehyde; a
glutaraldehyde; a hemiacetal releasing compound; an aldehyde
releasing compound; a diacid halide; a dihalide; a dichloride; a
dibromide; a polyacid anhydride; citric acid; an epoxide; a
furfuraldehyde; a glutaraldehyde; an aldehyde condensate; a
silyl-modified polyamide compound; and combinations thereof.
7. The method of claim 5 wherein the multifunctional material is
mixed with the tackifying compound in an amount of from about 0.01%
to about 50% by weight of the tackifying compound.
8. The method of claim 1 wherein the surfactant is capable of
binding active sites in the tackifying compound so as to reduce the
tackiness of the tackifying compound.
9. The method of claim 1 wherein the surfactant is selected from
the group consisting of: an ethyoxylated lauryl alcohol; an
ethoxylated nonylphenol; an ethoxylated nonylphenol phosphate
ester; a cationic surfactant; a nonionic surfactant; an alkyl
phosphonate surfactant; an alkylamidobetaine; cocoamidopropyl
betaine; alpha-olefin sulfonate; trimethyltallowammonium chloride;
C.sub.8 to C.sub.22 alkylethoxylate sulfate; trimethylcocoammonium
chloride; and combinations thereof.
10. The method of claim 1 wherein the surfactant is selected from
the group consisting of: an alcohol oxyalkylate; an alkyl phenol
oxyalkylate; a nonionic ester; a sorbitan ester; an alkoxylate of a
sorbitan ester; a castor oil alkoxylate; a fatty acid alkoxylate; a
lauryl alcohol alkoxylate; a nonylphenol alkoxylate; an octylphenol
alkoxylate; a tridecyl alcohol alkoxylate; mannide monooleate;
sorbitan isostearate; sorbitan laurate; sorbitan monoisostearate;
sorbitan monolaurate; sorbitan monooleate; sorbitan monopalmitate;
sorbitan monostearate; sorbitan oleate; sorbitan palmitate;
sorbitan sesquioleate; sorbitan stearate; sorbitan trioleate;
sorbitan tristearate; and sorbitan monooleate.
11. The method of claim 1 wherein the surfactant is present in an
amount in the range from about 0.1% to 10% by weight.
12. A method comprising: providing a tackifying compound surfactant
mixture comprising a tackifying compound having a tackiness and a
surfactant, wherein the tackiness of the tackifying compound is at
least temporarily reduced; and coating at least a plurality of
particulates with the tackifying compound surfactant mixture to
produce a plurality of coated particulates.
13. The method of claim 12 wherein the tackifying compound
comprises polyamides that are liquids or in solution at the
temperature of the subterranean formation.
14. The method of claim 12 wherein the tackifying compound is
selected from the group consisting of: a polyester, a
polycarbonate, polycarbamate, a natural resin, and shellac.
15. The method of claim 12 wherein the tackifying compound
comprises a multifunctional material capable of reacting with the
non-aqueous tackifying compound to form a hardened coating.
16. The method of claim 15 wherein the multifunctional material is
selected from the group consisting of: an aldehyde; a dialdehyde;
glutaraldehyde; a hemiacetal releasing compound; an aldehyde
releasing compound; a diacid halide; a dihalide; a dichloride; a
dibromide; a polyacid anhydride; citric acid; an epoxide; a
furfuraldehyde; a glutaraldehyde; an aldehyde condensate; a
silyl-modified polyamide compound; and combinations thereof.
17. The method of claim 12 wherein the surfactant is selected from
the group consisting of: an ethyoxylated lauryl alcohol; an
ethoxylated nonylphenol; an ethoxylated nonylphenol phosphate
ester; a cationic surfactant; a nonionic surfactant; an alkyl
phosphonate surfactant; an alkylamidobetaine; cocoamidopropyl
betaine; alpha-olefin sulfonate; trimethyltallowammonium chloride;
C.sub.8 to C.sub.22 alkylethoxylate sulfate; trimethylcocoammonium
chloride; and combinations thereof.
18. The method of claim 12 wherein the surfactant is selected from
the group consisting of: an alcohol oxyalkylate; an alkyl phenol
oxyalkylate; a nonionic ester; a sorbitan ester; an alkoxylate of a
sorbitan ester; a castor oil alkoxylate; a fatty acid alkoxylate; a
lauryl alcohol alkoxylate; a nonylphenol alkoxylate; an octylphenol
alkoxylate; a tridecyl alcohol alkoxylate; mannide monooleate;
sorbitan isostearate; sorbitan laurate; sorbitan monoisostearate;
sorbitan monolaurate; sorbitan monooleate; sorbitan monopalmitate;
sorbitan monostearate; sorbitan oleate; sorbitan palmitate;
sorbitan sesquioleate; sorbitan stearate; sorbitan trioleate;
sorbitan tristearate; and sorbitan monooleate.
19. A method comprising: providing at least a plurality of
particulates that have been coated with a tackifying compound
surfactant mixture comprising a tackifying compound having a
tackiness and a surfactant, wherein the tackiness of the tackifying
compound is at least temporarily reduced, to produce a plurality of
coated particulates; suspending the coated particulates in a
fracturing fluid or a gravel pack fluid; placing the fracturing
fluid or the gravel pack fluid in a subterranean formation; and
performing a fracturing or a gravel packing operation.
20. The method of claim 19 wherein: the tackifying compound is
selected from the group consisting of: a polyamide; a polyester; a
polycarbonate; polycarbamate; a natural resin; shellac; a
tackifying compound that comprises a multifunctional material that
is selected from the following group: an aldehyde; a dialdehyde;
glutaraldehyde; a hemiacetal releasing compound; an aldehyde
releasing compound; a diacid halide; a dihalide; a dichloride; a
dibromide; a polyacid anhydride; citric acid; an epoxide; a
furfuraldehyde; a glutaraldehyde; an aldehyde condensate; a
silyl-modified polyamide compound; and combinations thereof; and
the surfactant is selected from the group consisting of: an
ethyoxylated lauryl alcohol; an ethoxylated nonylphenol; an
ethoxylated nonylphenol phosphate ester; a cationic surfactant; a
nonionic surfactant; an alkyl phosphonate surfactant; an
alkylamidobetaine; cocoamidopropyl betaine; alpha-olefin sulfonate;
trimethyltallowammonium chloride; C.sub.8 to C.sub.22
alkylethoxylate sulfate; trimethylcocoammonium chloride; an alcohol
oxyalkylate; an alkyl phenol oxyalkylate; a nonionic ester; a
sorbitan ester; an alkoxylate of a sorbitan ester; a castor oil
alkoxylate; a fatty acid alkoxylate; a lauryl alcohol alkoxylate; a
nonylphenol alkoxylate; an octylphenol alkoxylate; a tridecyl
alcohol alkoxylate; mannide monooleate; sorbitan isostearate;
sorbitan laurate; sorbitan monoisostearate; sorbitan monolaurate;
sorbitan monooleate; sorbitan monopalmitate; sorbitan monostearate;
sorbitan oleate; sorbitan palmitate; sorbitan sesquioleate;
sorbitan stearate; sorbitan trioleate; sorbitan tristearate;
sorbitan monooleate; and combinations thereof.
Description
BACKGROUND
[0001] The present invention relates to methods and compositions
useful in treating subterranean formations, and more particularly,
to improved methods for coating particulates with tackifying
compounds for use in downhole applications, such as for
consolidating relatively unconsolidated portions of subterranean
formations and minimizing the flow back of unconsolidated
particulate material (referred to collectively herein as
"particulate migration").
[0002] In the production of hydrocarbons from a subterranean
formation, the subterranean formation preferably should be
sufficiently conductive to permit desirable fluids, such as oil and
gas, to flow to a well bore that penetrates the formation. One type
of treatment that may be used 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 pressure to
create or enhance one or more fractures in the subterranean
formation. The fluid used in the treatment may comprise
particulates, often referred to as "proppant particulates" or
"proppant," that are deposited in the resultant fractures. These
proppant particulates are thought to prevent the fractures from
fully closing upon the release of hydraulic pressure, forming
conductive channels through which fluids may flow to a well bore.
The term "propped fracture" as used herein refers to a fracture
(naturally-occurring or otherwise) in a portion of a subterranean
formation that contains at least a plurality of proppant
particulates. The term "proppant pack" refers to a collection of
proppant particulates within a fracture.
[0003] A type of particulate migration that may affect fluid
conductivity in the formation is the flow back of unconsolidated
particulate material (e.g., formation fines, proppant particulates,
etc.) 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. There are
several known techniques used to control particulate migration,
some of which may involve the use of consolidating agents. The term
"consolidating agent" as used herein includes any compound that is
capable of minimizing particulate migration in a subterranean
formation and/or modifying the stress-activated reactivity of
subterranean fracture faces and other surfaces in subterranean
formations.
[0004] One well-known technique used to control particulate
migration in subterranean formations is commonly referred to as
"gravel packing," which involves the placement of a filtration bed
of gravel particulates in the subterranean formation, which acts as
a barrier to prevent particulates from flowing into the well bore.
These gravel packing operations may involve the use of
consolidating agents to bind the gravel particulates together in
order to form a porous matrix through which formation fluids can
pass.
[0005] Another technique that may be used to control particulate
migration involves coating proppant particulates with a
consolidating agent (such as a tackifying compound) to facilitate
their consolidation within the formation and to prevent their
subsequent flow-back through the conductive channels in the
subterranean formation. The term "consolidating agent" as used
herein implies no particular mechanism or mode of consolidation or
stabilization. Consolidating agents may provide adhesive bonding
between formation particulates to alter the distribution of the
particulates within the formation in an effort to reduce their
potential negative impact on permeability and/or fracture
conductivity. Consolidating agents also may cause formation
particulates to become involved in collective stabilized masses
and/or stabilize the formation particulates in place to prevent
their migration that might negatively impact permeability and/or
fracture conductivity. The term "tackifying compound" as used
herein refers to a chemical compound capable of developing or
enhancing the capability/strength of adhesion of particulates in a
subterranean formation, and refers to both aqueous and nonaqueous
tackifying compounds.
[0006] Although tackifying compounds are used frequently, they may
be difficult to handle, transport and clean-up due to their
inherent tendency to stick to equipment or anything else with which
they may come into contact. Therefore, it would be desirable to
provide compositions and methods that would, among other things,
help ease the handling, transport and clean up operations
associated with using consolidating agents.
SUMMARY
[0007] The present invention relates to methods and compositions
useful in treating subterranean formations, and more particularly,
to improved methods for coating particulates with tackifying
compounds for use in downhole applications, such as for combating
particulate migration.
[0008] In one embodiment, the present invention provides a method
comprising: providing a tackifying compound and at least one
surfactant; mixing the surfactant with the tackifying compound to
form a tackifying compound surfactant mixture; coating the
tackifying compound surfactant mixture onto particulates to form
coated particulates; mixing the coated particulates into a
treatment fluid; and placing the treatment fluid into a
subterranean formation.
[0009] In one embodiment, the present invention provides a method
comprising: providing a tackifying compound surfactant mixture; and
coating at least a plurality of particulates with the tackifying
compound surfactant mixture to produce a plurality of coated
particulates.
[0010] In one embodiment, the present invention provides a method
comprising: providing at least a plurality of particulates that
have been coated with a tackifying compound surfactant mixture to
produce a plurality of coated particulates; suspending the coated
particulates in a fracturing fluid or a gravel pack fluid; placing
the fracturing fluid or the gravel pack fluid in a subterranean
formation; and performing a fracturing or a gravel packing
operation.
[0011] The features and advantages of the present invention will be
readily 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
[0012] The present invention relates to methods and compositions
useful in treating subterranean formations, and more particularly,
to improved methods for coating particulates with tackifying
compounds for use in downhole applications, such as for combating
particulate migration. The methods of the present invention may be
used in conjunction with the use of a tackifying compound in any
suitable well treatment in which it is desirable to control
particulate migration and/or modify the stress-activated reactivity
of subterranean fracture faces and other surfaces in subterranean
formations. These methods can be performed at any time during the
life of the well.
[0013] One of the many advantages of the methods of the present
invention is that they may enhance the efficiency and ease of using
tackifying compounds by allowing for, inter alia, relatively easy
clean up of equipment and reduced job failure due to the buildup of
the tackifying compounds on the equipment. The methods of the
invention provide for treating proppant particulates with
tackifying compounds with their tackiness temporarily "switched
off" during coating to help minimize potential handling problems,
such as proppant bridging and lock-up of coating equipment. The
term "switched off" as used herein refers to the relative tackiness
of the tackifying compound. When "switched off," the tackifying
compound has a lesser degree of tackiness.
[0014] In some embodiments, the present invention provides methods
comprising the steps of: providing a tackifying compound and at
least one surfactant; mixing the surfactant with the tackifying
compound to form a tackifying compound surfactant mixture; coating
the tackifying compound surfactant mixture onto particulates to
form coated particulates; mixing the coated particulates into a
treatment fluid; and placing the treatment fluid into a
subterranean formation. The treatment fluid may be used in
fracturing, gravel packing, and frac-packing applications.
[0015] It is believed that the surfactant binds with sites of the
tackifying compound to make those sites unavailable, causing the
tackiness of the tackifying compound to reduce and perhaps
disappear. It is possible that a charged species of the surfactant
participates in this phenomenon, possibly by saturating these
binding sites with water molecules. This appears reversible,
however, and once the surfactant is removed (or its concentration
is sufficiently reduced, e.g., as the water molecules are removed
from the binding sites), that the tackiness of the tackifying
compound may be restored and beneficially used as contemplated.
[0016] 1. Suitable Non-aqueous Tackifying Compounds
[0017] In some embodiments of the present invention, non-aqueous
tackifying compounds may be used. A particularly preferred group of
non-aqueous tackifying compounds comprises polyamides that are
liquids or in solution at the temperature of the subterranean
formation such that they are, by themselves, non-hardening when
introduced into the subterranean formation. A particularly
preferred product 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.
[0018] Additional compounds which may be used as non-aqueous
tackifying compounds include liquids and solutions of, for example,
polyesters, polycarbonates and polycarbamates, natural resins such
as shellac and the like.
[0019] Other suitable non-aqueous tackifying compounds are
described in U.S. Pat. No. 5,853,048 issued to Weaver, et al. and
U.S. Pat. No. 5,833,000 issued to Weaver, et al., the relevant
disclosures of which are herein incorporated by reference.
[0020] Non-aqueous tackifying compounds suitable for use in the
present invention may either be 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 compound 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 compound may function similarly to a
hardenable resin.
[0021] Multifunctional materials suitable for use in the present
invention include, but are not limited to, aldehydes, 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, aldehyde condensates, and
silyl-modified polyamide compounds and the like, and combinations
thereof. Suitable silyl-modified polyamide compounds that may be
used in the present invention are those that are substantially
self-hardening compositions capable of at least partially adhering
to particulates in the unhardened state, and that are further
capable of self-hardening themselves to a substantially non-tacky
state to which individual particulates such as formation fines 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.
[0022] 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
other embodiments, the compound is present in an amount of from
about 0.5% to about 1% by weight of the tackifying compound.
Suitable multifunctional 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.
[0023] 2. Suitable Types of Surfactants
[0024] Surfactants suitable for use in the present invention are
those capable of binding the active sites in the tackifying
compound so as to reduce the tackiness of the tackifying compound.
In some embodiments, the surfactant may comprise an ethyoxylated
lauryl alcohol, an ethoxylated nonylphenol, an ethoxylated
nonylphenol phosphate ester, a cationic surfactant, a nonionic
surfactant, an alkyl phosphonate surfactant, or a combination
thereof.
[0025] In some embodiments, the surfactant may comprise a cationic
surfactant. Examples of suitable cationic surfactants include, but
are not limited to, alkylamidobetaines such as cocoamidopropyl
betaine, alpha-olefin sulfonate, trimethyltallowammonium chloride,
C.sub.8 to C.sub.22 alkylethoxylate sulfate and
trimethylcocoammonium chloride. Cocoamidopropyl betaine is
especially preferred. Other suitable surfactants available from
Halliburton Energy Services include: "19NTM," "G-Sperse
Dispersant," "Morflo III.RTM." surfactant, "Hyflo.RTM. IV M"
surfactant, "Pen-88MTM" surfactant, "HC-2TM Agent," "Pen-88 HTTM"
surfactant, "SEM-7 TM" emulsifier, "Howco-Suds TM" foaming agent,
"Howco Sticks TM" surfactant, "A-Sperse TM" Dispersing aid for acid
additives, "SSO-21E" surfactant, and "SSO-21MW TM" surfactant.
[0026] In some embodiments, the surfactant may comprise a nonionic
surfactant. Such preferred nonionic surfactants include, but are
not limited to, alcohol oxyalkylates, alkyl phenol oxyalkylates,
nonionic esters such as sorbitan esters and alkoxylates of sorbitan
esters. Examples of suitable surfactants include but are not
limited to, castor oil alkoxylates, fatty acid alkoxylates, lauryl
alcohol alkoxylates, nonylphenol alkoxylates, octylphenol
alkoxylates, tridecyl alcohol alkoxylates, such as POE-10
nonylphenol ethoxylate, POE-100 nonylphenol ethoxylate, POE-12
nonylphenol ethoxylate, POE-12 octylphenol ethoxylate, POE-12
tridecyl alcohol ethoxylate, POE-14 nonylphenol ethoxylate, POE-15
nonylphenol ethoxylate, POE-18 tridecyl alcohol ethoxylate, POE-20
nonylphenol ethoxylate, POE-20 oleyl alcohol ethoxylate, POE-20
stearic acid ethoxylate, POE-3 tridecyl alcohol ethoxylate, POE-30
nonylphenol ethoxylate, POE-30 octylphenol ethoxylate, POE-34
nonylphenol ethoxylate, POE-4 nonylphenol ethoxylate, POE-40 castor
oil ethoxylate, POE-40 nonylphenol ethoxylate, POE-40 octylphenol
ethoxylate, POE-50 nonylphenol ethoxylate, POE-50 tridecyl alcohol
ethoxylate, POE-6 nonylphenol ethoxylate, POE-6 tridecyl alcohol
ethoxylate, POE-8 nonylphenol ethoxylate, POE-9 octylphenol
ethoxylate, mannide monooleate, sorbitan isostearate, sorbitan
laurate, sorbitan monoisostearate, sorbitan monolaurate, sorbitan
monooleate, sorbitan monopalmitate, sorbitan monostearate, sorbitan
oleate, sorbitan palmitate, sorbitan sesquioleate, sorbitan
stearate, sorbitan trioleate, sorbitan tristearate, POE-20 sorbitan
monoisostearate ethoxylate, POE-20 sorbitan monolaurate ethoxylate,
POE-20 sorbitan monooleate ethoxylate, POE-20 sorbitan
monopalmitate ethoxylate, POE-20 sorbitan monostearate ethoxylate,
POE-20 sorbitan trioleate ethoxylate, POE-20 sorbitan tristearate
ethoxylate, POE-30 sorbitan tetraoleate ethoxylate, POE-40 sorbitan
tetraoleate ethoxylate, POE-6 sorbitan hexastearate ethoxylate,
POE-6 sorbitan monstearate ethoxylate, POE-6 sorbitan tetraoleate
ethoxylate, and/or POE-60 sorbitan tetrastearate ethoxylate.
Preferred nonionic surfactants include alcohol oxyalkyalates such
as POE-23 lauryl alcohol and alkyl phenol ethoxylates such as POE
(20) nonyl phenyl ether. Other applicable nonionic surfactants are
esters such as sorbitan monooleate.
[0027] The surfactant may be used in an amount sufficient to
counterattack the tackiness of the tackifying compound to the
desired degree. The surfactant is preferably present in the
tackifying compound surfactant mixture in an amount in the range
from about 0.1% to 10% by weight.
[0028] 3. Suitable Particulates
[0029] A wide variety of particulate materials may be used (e.g.,
as proppant or gravel) in accordance with the present invention,
including, but not limited to, sand; bauxite; ceramic materials;
glass materials; resin pre-coated proppant (e.g., commercially
available from Borden Chemicals and Santrol, for example, both from
Houston, Tex.); polymer materials; "TEFLON".TM.
(tetrafluoroethylene) materials; nut shells; ground or crushed nut
shells; seed shells; ground or crushed seed shells; fruit pit
pieces; ground or crushed fruit pits; processed wood; composite
particulates prepared from a binder with filler particulate
including silica, alumina, fumed carbon, carbon black, graphite,
mica, titanium dioxide, meta-silicate, calcium silicate, kaolin,
talc, zirconia, boron, fly ash, hollow glass microspheres, and
solid glass; or mixtures thereof. The particulates used may have a
particle size in the range of from about 2 to about 400 mesh, U.S.
Sieve Series. Preferably, the particulates are graded sand having a
particle size in the range of from about 10 to about 70 mesh, U.S.
Sieve Series. Preferred sand particle size distribution ranges are
one or more of 10-20 mesh, 20-40 mesh, 40-60 mesh or 50-70 mesh,
depending on the particle size and distribution of the formation
particulates to be screened out by the proppant. For high stress
applications (e.g., those involving about 6000 psi or more),
preferred particulates are likely ceramic particles and sintered
bauxite since these materials have relatively high crush
resistance.
B. Description of Some Methods of the Present Invention
[0030] In some embodiments, the present invention provides methods
comprising the steps of: providing a tackifying compound and at
least one surfactant; mixing the surfactant with the tackifying
compound to form a tackifying compound surfactant mixture; coating
the tackifying compound surfactant mixture onto particulates to
form coated particulates; mixing the coated particulates into a
treatment fluid; and placing the treatment fluid into a
subterranean formation. Preferably the treatment fluids used in the
present invention are aqueous-based fluids. Suitable aqueous-based
fluids that may be used in the present invention include fresh
water, salt water, brine, seawater, or any other aqueous fluid
that, preferably, does not adversely react with the other
components used in accordance with this invention or with the
subterranean formation. The aqueous fluid preferably is present in
the treatment fluids of the present invention in an amount in the
range from about 40% to 80% by weight of the tackifying compound
surfactant mixture.
[0031] The treatment fluid may be used in fracturing, gravel
packing, and frac-packing applications. The term "coated
particulate" as used herein means particulates that have been at
least partially coated with a process comprising a tackifying
compound surfactant mixture of the present invention. The
particulates may be coated by any suitable method as recognized by
one skilled in the art with the benefit of this disclosure, e.g.,
using a method comprising a sand screw. The term "coated" does not
imply any particular degree of coverage of the particulates with
the tackifying compound surfactant mixture.
[0032] One example of a method of the present invention comprises
the steps of: providing a tackifying compound surfactant mixture;
and coating at least a plurality of particulates with the
tackifying compound surfactant mixture to produce a plurality of
coated particulates. These coated particulates may then be used
downhole, for example, in a fracturing or a gravel packing
operation.
[0033] In some embodiments, the methods of the present invention
may be used, inter alia, in primary, remedial, or proactive
methods. Whether a particular method of this invention is
"primary," "remedial," or "proactive" is determined relative to the
timing of a fracturing treatment or a gravel packing treatment. A
primary method of the present invention may involve using the
methods of the present invention in conjunction with a fracturing
fluid or a gravel pack fluid. The remedial methods may be used in
wells wherein a portion of the well has been fractured and propped.
The remedial methods also may be used in a gravel packing
situation, for example where there has been a screen problem or
failure. The proactive methods may be used in wells that have not
yet been fractured or gravel packed. The proactive methods can be
performed in conjunction with a fracturing treatment, for example,
as a pre-pad to the fracturing treatment or in any diagnostic
pumping stage performed before a fracturing, gravel packing, or
acidizing procedure.
[0034] In accordance with the methods and compositions of the
present invention, all or part of the particulate transported into
the fractures is coated (preferably on-the-fly) with a tackifying
compound surfactant mixture and may then be suspended in a
fracturing fluid or used as part of a gravel packing process. The
amount of tackifying compound surfactant mixture coated on the
particulates is in the range from about 0.1% to about 20% by weight
of the particulate, with about 1 to about 5% being preferred. The
term "on-the-fly" is used herein to mean that a flowing stream is
continuously introduced into another flowing stream so that the
streams are combined and mixed while continuing to flow as a single
stream. The coating of the dry particulates with the tackifying
compound surfactant mixtures and any mixing of the coated
particulates with a fracturing fluid or treatment fluid are all
preferably accomplished on-the-fly. Preferably the particulates are
coated using a sand screw. The methods of the present invention
should allow less torque to be used in conjunction with the sand
screw, which may be beneficial.
[0035] As is well understood by those skilled in the art, such
mixing can also be accomplished by batch mixing or partial batch
mixing.
[0036] To facilitate a better understanding of the present
invention, the following examples of certain aspects of some
embodiments are given. In no way should the following examples be
read to limit, or define, the entire scope of the invention.
EXAMPLE 1
[0037] First, a mixture of a tackifying compound was prepared by
mixing 10 cc of "SANDWEDGE NT" (available from Halliburton Energy
Services in Duncan, Okla.) with 0.1 cc of "SSO-21" (a cationic
surfactant also available from Halliburton Energy Services). From
this mixture, 1.5 cc was obtained to dry coat onto 100 gram of
20/40 mesh Brady sand in a 4 ounce cup. It was observed that there
was a lack of tackiness between sand grains as compared to a normal
coating with "SANDWEDGE NT," although the mixture was coated well
on the sand. After coating thoroughly with a spatula, the coated
sand was mixed with warm tap water and rinsed off. After rinsing
the coated sand twice with water, about 100 cc each time, the
tackiness began to come back.
[0038] 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 or modified
and all such variations are considered within the scope and spirit
of the present invention. 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 as referring to the power set
(the set of all subsets) of the respective range of values, and set
forth every 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.
* * * * *