U.S. patent application number 14/323830 was filed with the patent office on 2014-10-30 for drag-reducing copolymer compositions.
The applicant listed for this patent is CESI Chemical, Inc.. Invention is credited to Lakia Champagne, Gydeon Gilzow, Marlin Holtmyer, Earl Parnell, David Philpot, Todd Sanner, Thomas Sifferman, Andrei Zelenev.
Application Number | 20140323366 14/323830 |
Document ID | / |
Family ID | 45556566 |
Filed Date | 2014-10-30 |
United States Patent
Application |
20140323366 |
Kind Code |
A1 |
Parnell; Earl ; et
al. |
October 30, 2014 |
DRAG-REDUCING COPOLYMER COMPOSITIONS
Abstract
A method of preparing and using a drag-reducing composition in a
well treatment operation includes the step of preparing the
drag-reducing composition by mixing a polymer emulsion that
includes a first surfactant and a first solvent, with a second
surfactant and a second solvent. The method continues with the step
of combining the drag-reducing composition with an aqueous
treatment fluid. The method further includes the step of injecting
the drag-reducing composition and aqueous treatment fluid into a
subterranean formation, a pipeline or a gathering line.
Inventors: |
Parnell; Earl; (Longview,
TX) ; Sanner; Todd; (Duncan, OK) ; Holtmyer;
Marlin; (Duncan, OK) ; Philpot; David;
(Marlow, OK) ; Zelenev; Andrei; (The Woodlands,
TX) ; Gilzow; Gydeon; (Beaumont, TX) ;
Sifferman; Thomas; (Carrollton, TX) ; Champagne;
Lakia; (Spring, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CESI Chemical, Inc. |
Marlow |
OK |
US |
|
|
Family ID: |
45556566 |
Appl. No.: |
14/323830 |
Filed: |
July 3, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12268408 |
Nov 10, 2008 |
|
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14323830 |
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Current U.S.
Class: |
507/222 ;
507/225 |
Current CPC
Class: |
C09K 8/528 20130101;
C09K 2208/28 20130101; C09K 8/64 20130101; E21B 43/20 20130101;
C09K 8/82 20130101; C09K 8/512 20130101; C09K 8/68 20130101; C09K
8/588 20130101; C09K 8/604 20130101; C09K 8/584 20130101; C09K
8/608 20130101 |
Class at
Publication: |
507/222 ;
507/225 |
International
Class: |
C09K 8/584 20060101
C09K008/584; C09K 8/588 20060101 C09K008/588 |
Claims
1. A drag-reducing additive for use in a well, pipeline, or
gathering line, the drag-reducing additive comprising: 40-85% by
weight of a dispersion polymer, wherein the dispersion polymer
comprises a polymer in an aqueous mixture; 10-35% by weight of a
surfactant with an HLB greater than 8; and 5-30% by weight of a
solvent.
2. The drag-reducing additive of claim 1, wherein the polymer is a
copolymer.
3. The drag-reducing additive of claim 2, wherein the copolymer
comprises acrylamide and acrylic acid.
4. The drag-reducing additive of claim 3, wherein the copolymer
comprises polyacrylamide and a monomer selected from the group
consisting of acrylic acid, sodium acrylate,
methylacrylamidopropyltrimethylammonium chloride,
diallyldimethylammonium chloride, and dimethylaminoethylacrylate
methyl chloride quaternary salt.
5. The drag-reducing additive of claim 1, wherein the polymer is a
water-soluble homopolymer.
6. The drag-reducing additive of claim 1, wherein the solvent
comprises a terpene.
7. The drag-reducing additive of claim 1, wherein the solvent
comprises a terpenoid.
8. The drag-reducing additive of claim 1, wherein the solvent
comprises d-limonene.
9. The drag-reducing additive of claim 1, wherein the solvent
comprises a plant-derived terpene.
10. The drag-reducing additive of claim 1, wherein the surfactant
is selected from the group consisting of ethoxylated alcohols,
ethoxylated castor oils, and ethoxylated sorbitan monooleates.
11. An additive for use in a well, pipeline, or gathering line
comprising: about 50-99% by weight of a polymer emulsion, wherein
the polymer emulsion comprises a polymer, a first surfactant, and a
first solvent; about 1-50% by weight of a second surfactant with an
HLB greater than 8; less than about 5% by weight of a second
solvent; and wherein the additive comprises a paste-like, highly
viscous material.
12. The additive of claim 11, wherein the polymer is a
copolymer.
13. The additive of claim 12, wherein the copolymer comprises
acrylamide and acrylic acid.
14. The additive of claim 12, wherein the second surfactant is
selected from the group consisting of alcohol ether sulfate,
ethoxylated castor oil, and ethoxylated sorbitan monooleate.
15. The additive of claim 12, wherein the polymer is a
water-soluble homopolymer.
16. A drag-reducing additive for use with an aqueous treatment
fluid in a well, pipeline, or gathering line, the drag-reducing
additive comprising: 40-85% by weight of a dispersion polymer,
wherein the dispersion polymer comprises dry polymer dissolved in
an aqueous mixture; 10-35% by weight of a surfactant with an HLB
greater than 8; and 5-30% by weight of a solvent.
17. The drag-reducing additive of claim 16, wherein the solvent
comprises a terpene.
18. The drag-reducing additive of claim 16, wherein the solvent
comprises a terpenoid.
19. The drag-reducing additive of claim 16, wherein the solvent
comprises d-limonene.
20. The drag-reducing additive of claim 16, wherein the solvent
comprises a plant-derived terpene.
21. The drag-reducing additive of claim 16, wherein the surfactant
is selected from the group consisting of alcohol ether sulfate,
ethoxylated castor oil, and ethoxylated sorbitan monooleate.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/268,408, entitled "Drag-Reducing Copolymer
Compositions," filed Nov. 10, 2008.
FIELD OF THE INVENTION
[0002] The present invention is generally related to the treatment
of oil and gas wells and/or gathering lines and pipelines, and more
particularly related to a composition and process for reducing the
drag, or fluid friction, caused by the injection of aqueous
treatment fluids into subterranean geological formations.
BACKGROUND OF THE INVENTION
[0003] Crude oil and natural gas are typically recovered from
subterranean reservoirs through the use of drilled wells and
production equipment. After the wells are drilled, cased and
cemented, it is often necessary to stimulate the reservoir by means
of hydraulic fracturing or acidizing to achieve economical flow of
gas and oil. This typically requires pumping an aqueous treatment
fluid into the well at high rates, so that the fluid will build up
pressure and cause the formation to fracture.
[0004] In the process of pumping, substantial fluid friction
pressure, or drag, is observed between the treatment fluid and the
tubing or casing as the fluid reaches turbulent flow, thus causing
a substantial energy loss. As a result of the energy loss, a higher
pumping pressure is needed to achieve the desired flow rate and
pressure. It is therefore common to include drag-reducing additives
in the aqueous treatment fluids to suppress the turbulence and
realize lower pumping pressures. Common drag-reducing additives
include oil-external emulsions of polymers with oil-based solvents
and an emulsion-stabilizing surfactant. The emulsions may include
guar-based or polyacrylamide-acrylic acid (PAM-AA) copolymers.
Typically these prior art emulsions consist of an aqueous phase
dispersed in a non-aqueous phase, in a weight ratio of from about
5:1 to about 10:1 aqueous phase to non-aqueous phase.
[0005] The surfactants in known drag reduction emulsions are
typically emulsifying surfactants that stabilize the emulsions. The
emulsifying surfactants have low HLB values, generally between 4
and 8. The transfer of the polymer from inside the aqueous phase of
the oil-external emulsion into an aqueous treatment fluid is
achieved by the inversion of an emulsion. A common way to achieve
this inversion is to use an inverting surfactant, which is
typically water-soluble and has an HLB of greater than about 7.
Inverting surfactants may be a part of polymer emulsion
formulations or may be added to a solution into which the emulsion
is to be inverted.
[0006] The problem encountered with these known treatments,
however, is that inverting surfactants may adversely interact with
the emulsifier or emulsion and destroy it prior to use. Thus,
commercially available polymer emulsions generally contain less
than 5% of inverting surfactant. Polymer emulsions with this low
amount of inverting surfactant, however, may not provide the
desired reduction in friction because the polymer emulsion either
does not invert completely or is not brine or acid tolerant.
[0007] In the event that acid or high salt contents are
encountered, emulsion copolymers of 2-Acrylamido-2-methyl propane
sulfonic acid (AMPS) are commonly used. These AMPS copolymers,
however, may be cost prohibitive. In either case, the high
molecular weight polymers may also cause substantial damage to the
formation permeability. Thus, there is a continued need for more
effective compounds that are more efficient, more salt tolerant,
and less damaging.
SUMMARY OF THE INVENTION
[0008] The present invention includes a method of preparing and
using a drag-reducing composition in a well treatment operation. In
a preferred embodiment, the method includes the step of preparing
the drag-reducing composition by mixing a polymer emulsion that
includes a first surfactant and a first solvent, with a second
surfactant and a second solvent. The method continues with the step
of combining the drag-reducing composition with an aqueous
treatment fluid. The method further includes the step of injecting
the drag-reducing composition and aqueous treatment fluid into a
subterranean formation, a pipeline or a gathering line.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0009] The present invention relates to the preparation and use of
a polymer composition that can be used as a drag-reducing additive.
Unlike prior art drag reducers, the additives of the preferred
embodiments are formed by the combination of polymer with
relatively high amount of surfactant. In a first embodiment, a
three-component additive is formed upon the combination of a
polymer and a surfactant with a solvent. In an alternate
embodiment, a two-component additive is formed upon a combination
of a polymer and a surfactant. It is understood that the
compositions of these embodiments have a variety of uses, one of
which is drag reduction. The solvent is preferably a terpene. The
additives can be added to an appropriate treatment fluid to form a
well treatment composition or a composition for treatment of
gathering lines or pipelines.
[0010] In a preferred embodiment, the polymer component of the
additive is in the form of a commercially-available polymer
emulsion, which typically already includes some solvent and
emulsion surfactant. However, polymer emulsion could be
synthesized, instead of purchased. It will be understood that the
term "polymer" includes both homopolymers and copolymers. Upon
addition to the treatment fluid, the components of the
drag-reducing additive form an oil-in-water emulsion that reduces
the friction between the turbulent flow of the treatment fluid and
the walls of the well tubing or casing, or the walls of a pipeline
or gathering line. In a preferred embodiment, the treatment fluid
is water-based. Upon dilution, the additive may form a
microemulsion, a miniemulsion, a nanoemulsion or an emulsion.
[0011] By adding a relatively large amount of surfactant to the
additive, compared to surfactant levels in prior art friction
reducers, the hydrophilicity and dispersibility of the polymer is
increased, thus increasing the stability of the system in aqueous
downhole fluid or in a pipeline or gathering lines. Furthermore,
the increased surfactant level increases the inversion rate of the
additive, even under low energy conditions. As a result, less
polymer is needed to achieve the desired friction-reducing
performance, which results in less damage downhole. Another benefit
of the increased surfactant level in the additive is improved
performance in brine.
[0012] The first component in the system, the polymer, may be
nonionic, zwitterionic, anionic, or cationic. The polymer may
further be a dispersion polymer or an emulsion polymer. Such
polymer preferably consists of acrylamide present in the amount
between 1 and 100 mole % and cationic, anionic, zwitterionic, or
nonionic monomers present in the amount between 0 and 99 mole
%.
[0013] When the copolymer includes acrylamide and an anionic
monomer, the anionic monomer may be acrylamidopropanesulfonic acid,
acrylic acid, methacrylic acid, monoacryloxyethyl phosphate, or
their alkali metal salts. When the copolymer includes acrylamide
and a cationic monomer, the cationic monomer may be
dimethylaminoethylacrylate methyl chloride quarternary salt,
diallyldimethylammonium chloride (DADMAC),
(3-acrylamidopropyl)trimethylammonium chloride (MAPTAC),
(3-methacrylamido)propyltrimethylammonium chloride, dimethylamino
ethyl-methacrylate methyl chloride quarternary salt, or
dimethylaminoethylacrylate benzylchloride quarternary salt.
[0014] When the copolymer includes acrylamide and a nonionic
monomer, the nonionic monomer may be acrylamide, methacrylamide,
N-methylacrylamide, N,N-dimethyl(meth)acrylamide, octyl acrylamide,
N(2-hydroxypropyl)methacrylamide, N-methylolacrylamide,
N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide,
poly(ethylene glycol)(meth)acrylate, poly(ethylene
glycol)monomethyl ether mono(meth)acrylate, N-vinyl-2-pyrrolidone,
glycerol mono((meth)acrylate, 2-hydroxyethyl(meth)acrylate, vinyl
methylsulfone, or vinyl acetate.
[0015] When the copolymer includes acrylamide and a zwitterionic
monomer, the zwitterionic monomer may be selected from those
described in U.S. Pat. No. 6,709,551 or be selected from
N,N-dimethyl-N-acryloyloxyethynyl-N-(3-sulfopropyl)-ammonium
betaine,
N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium
betaine,
N,N-dimethyl-N-methacrylcryloyloxyethynyl-N-(3-sulfopropyl)-ammonium
betaine,
N,N-dimethyl-N-methacrylcryloyloxyethynyl-N-(3-sulfopropyl)-sulf-
oneum betaine, 2-(methylthio)ethyl
methacryloyl-S-(sulfopropyl)-sulfonium betaine,
2-[(2-acryloylethyl)dimethylammonio]ethyl 2-methyl phosphate,
2-(acryloyloxyethyl)-2'-(trimethylammonium)ethyl phosphate, or
[(2-acryloylethyl)dimethylammonio]methyl phosphonic acid. It will
be understood that the lists of potential monomers are not
limiting, and the use of other monomers may also be
appropriate.
[0016] From testing of various polymers in the three-component
additive embodiment, it was determined that the use of a copolymer
made up of polyacrylamide and an anionic monomer additive resulted
in increased permeability restoration when compared to copolymers
with nonionic or cationic monomers. Thus, it is preferred to use a
copolymer of acrylamide and an anionic monomer, such as acrylic
acid. In a presently preferred embodiment, the copolymer is a
polyacrylamide-acrylic acid (PAM-AA) copolymer having a molecular
weight from about 4 million to 20 million amu, with a percentage of
acrylamide in the range of 60-99% by weight and a percentage of
acrylic acid from 1 to 40% by weight.
[0017] The second component in the three component additive
embodiment, the surfactant, may have a hydrophile-lipophile balance
(HLB) of above about 7, and preferably has an HLB of between 11 and
15. It will be understood that the surfactant component may be made
up of one surfactant or a blend of surfactants. Highly preferred
nonionic surfactants have an HLB of 12 to 13. These surfactants aid
in the inversion of the polymer when the additive comes into
contact with aqueous treatment fluid, and are sometimes referred to
as inverting surfactants. Preferred surfactants are liquids chosen
from ethoxylated glycerides, ethoxylated sorbitan esters,
ethoxylated alkyl phenols, ethoxylated alcohols, castor oil
ethoxylates, cocoamide ethoxylates, and sorbitan monooleates such
as polyoxyethylene 20 sorbitan monooleate (Tween.RTM. 80). In a
particularly preferred embodiment, the surfactant is a castor oil
ethoxylate with 30 moles of ethylene oxide (EO) per 1 mole of
castor oil ethoxylate. In an alternate particularity preferred
embodiment, the surfactant component is a surfactant mixture of:
(i) alcohol ethoxylate C8-C18 with 5-20 moles EO; and (ii)
ethoxylated castor oil with 25-45 moles of EO.
[0018] The third component in the three-component additive
embodiment, the solvent, is preferably a blend of naturally
occurring plant terpenes. Terpenes often consist of units of
isoprene and have the formula (C.sub.5H.sub.8).sub.n, where n is
the number of linked isoprene units. Other terpenes, such as those
found in eucalyptus and peppermint oils, may include compounds
containing oxygen. A complex plant-derived terpene typically
includes a variety of compounds, including monoterpenes
(C.sub.10H.sub.16), d-limonene, dipentene, 1-limonene,
d,l-limonene, myrcene, and .alpha.-pinene. Additional terpenes
include terpinolene, .beta.-pinene, eucalyptol, .alpha.-terpineol,
.beta.-terpineol, sabinene, menthofurane, 1,8-cineole, citronellal,
cintronellol, menthol, mentohone, and alcohols and aldehydes of the
same composition and mixtures thereof.
[0019] The terpene blend may be further combined with other
solvents such as other plant-derived alcohols or esters, or
aromatic hydrocarbons. Plant-derived alcohols in the solvent may
include terpenoids and straight chain alcohols with the formula
CH.sub.3(CH.sub.2).sub.nOH, where n.gtoreq.9 or 11. Plant-derived
esters include methyl and ethyl esters of naturally-occurring oils
such as cottonseed or soybean oil. It should be noted that
synthetic solvents can also be used as the solvent phase.
[0020] In a preferred embodiment, the solvent has a KB
(Kauri-butanol) value of greater than about 60. Preferred terpenes
are those derived from citrus fruits, eucalyptus, or mint. In a
particularly preferred embodiment, the solvent is a biodegradable
solvent blend primarily made up of d-limonene.
[0021] Emulsion polymers that comprise a component of the present
additive can be either obtained from commercial suppliers or be
synthesized. In a preferred embodiment, a drag-reducing additive is
made by mixing about 40 to 85% by weight of a commercially
available polymer emulsion, such as the type available from Hychem,
Inc., with about 5 to 30% by weight additional solvent and about 5
to 35% by weight of additional surfactant. The commercially
available polymer emulsion may include a polymer and small amounts
of an emulsion surfactant, a solvent, and possibly an inverting
surfactant. Thus, the additional solvent that is added to the
polymer emulsion will be referred to as the second solvent, and the
additional surfactant that is added to the polymer emulsion will be
referred to as the second surfactant.
[0022] In a particularly preferred embodiment, the three-component
drag-reducing additive is prepared by blending about 55 to 65% by
weight of a commercially available polymer emulsion with about 10
to 30% by weight of a second terpene solvent and about 20% to 35%
by weight of a second nonionic surfactant. In this preferred
embodiment, the second nonionic surfactant is made up primarily of
a surfactant with an HLB of 12 to 13, such as a castor oil
ethoxylate with 30 moles of ethylene oxide. The commercially
available polymer emulsion preferably includes acrylamide in the
range of 60 to 90% by weight and acrylic acid in the range of 5 to
30% by weight. It is preferred to mix the additional surfactant and
solvent before adding the polymer emulsion, but order of mixing is
not critical. In other preferred embodiments, the drag-reducing
additive includes other additives such as acids, bases, corrosion
inhibitors, proppants, biocides, oxygen scavengers, asphaltene
inhibitors, and oils.
[0023] In another embodiment, three-component drag-reducing
additive is formed by synthesizing a polymer emulsion that is
combined with the second terpene solvent and second surfactant,
instead of using a commercially available polymer emulsion. The
synthesized polymer emulsion is combined with the second solvent
and second surfactant in the amounts described above. Methods
suitable for preparation of emulsion polymers are well known to
those skilled in the art. For example, such methods are described
in U.S. Pat. Nos. 3,284,393; 3,734,873; 6,605,674; and 6,753,388.
Suitable emulsion polymers can be prepared by a process that
typically involves preparing an oil phase containing suitable
surfactants, preparing an aqueous monomer phase containing the
monomers, preparing a water-in-oil emulsion of the aqueous phase in
the oil phase, and performing polymerization of monomers, usually
by means of free radical polymerization. In certain instances
structural modifiers or crosslinking agents can be added at various
stages of the process. Suitable such agents and means of their
addition would be known to those skilled in the art. Polymer solids
in the prepared emulsion polymers typically comprise from about 5
to about 60% by weight. It should be understood, however, that
there may be other methods of preparing the suitable polymer
emulsion.
[0024] Friction reducing polymers suitable to practice the present
invention may also be chosen from a class of dispersion polymers,
such as those described in U.S. Pat. Nos. 4,929,655; 5,605,970;
5,837,776; 5,597,858; 6,217,778; 6,365,052; 7,323,510; and European
patent EP630,909. Use of dispersion polymers for reducing friction
has been disclosed in U.S. Pat. No. 6,787,506. Dispersion polymers
may either be acquired from a commercial source or synthesized.
Typical synthesis of dispersion polymers involves polymerizing one
or more water-soluble monomers in an aqueous reaction mixture,
wherein the aqueous reaction mixture contains a water soluble salt,
at least one polymeric dispersant, optionally contains an organic
alcohol, optionally contains a pre-formed polymer seed. The water
soluble polymer formed as a result of polymerization is insoluble
in the aqueous reaction mixture at the concentration thereof formed
during the polymerization. Polymer solids in the prepared
dispersion are typically from about 5% to about 60% by weight.
[0025] Dry (powder) polymers may be used as part of this additive
if they are first dissolved in a treatment fluid miscible with
water or as a dispersion. Other drag reducing polymers such as
guar, xanthan, and other natural polymers along with synthetics can
also be used in the practice of this invention.
[0026] When combined, the blend of the copolymer, solvent, and
surfactant becomes a one phase system that may remain stable for
more than 24 hours and may be adapted for use in a broad
temperature range. Thus, each of the selected components in the
drag-reducing additive may be mixed together before delivery to the
well.
[0027] A two-component embodiment of the additive is preferably
made by combining about 50-99% of a polymer emulsion with about
1-50% of a surfactant with an HLB above about 7. Having more than
50% surfactant may also yield suitable friction reducing
formulations, but such systems may be unstable, not as effective
and efficient in friction reduction, and not as cost-advantageous,
as systems with less than 50% surfactant. The two-component
additive becomes highly viscous when about 75-99% of the polymer
emulsion is combined with about 1-25% of the surfactant. Addition
of less than 5% of a solvent may result in producing high viscosity
embodiment of the additive. Addition of a small amount of solvent
may actually increase the viscosity of the additive, but upon
addition of larger amounts of solvent, the viscosity will be
decreased. In another embodiment, less than about 30% of the
polymer emulsion is combined with about 70-99% of the surfactant
with an HLB of above about 7. In a preferred embodiment, the
two-component additive may be made by using a commercially
available polymer emulsion, and the surfactant with an HLB of
greater than about 7, and most preferably with an HLB of 12 to 13.
The highly viscous form of the two-component additive may be
delivered to a solution by a pump, extruding device or any other
suitable means. The highly viscous form of the two-component
additive may generally have a complex viscosity magnitude of
greater than about 40 Pascal-sec (Pa s).
[0028] The additives described above have multiple uses. The uses
may include, without limitation, drag reduction, flocculation,
water clarification, solids/liquids separation, sludge dewatering,
mining, and papermaking.
[0029] More specifically, compositions described above may be
suitable as flocculation-promoting agents in solids-liquid
separation, water treatment, papermaking, mining, and other
applications. They can be used alone, or in a combination with
various other additives typically used to promote flocculation.
These other additives include but not limited to high molecular
weight polymers bearing anionic and cationic charge or no charge at
all. Some non-limiting examples of such polymers include various
co-polymers of polyacrylamide, cross-linked, linear or branched, as
well as polyethylene oxide and poly naphthalene sulfonate. Other
known additives in the flocculation process that can be used in
combination with the compositions of the present invention include
chemically modified and unmodified polysaccharides, such as
starches, coagulants, such as aluminum sulfate, poly aluminium
chloride, poly-diallyl dimethyl ammonium chloride (DADMAC),
poly-epichlorohydrine dimethyl ammonium chloride,
3-trimethylammonium propyl methacrylamide chloride (MAPTAC), or
other similar substances. Other suitable additives can be chosen
from a class of colloidal materials, such as colloidal silica,
colloidal borosilicate, colloidal zirconium oxide, colloidal
aluminum oxide and hydroxide, colloidal alumosilicate, or clays,
both naturally occurring and synthetic, such as bentonite,
laponite, saponite. Microgels, such as polysilicate microgel and
polyalumosilicate microgel, are also suitable colloidal products.
Structurally rigid polymers and polymer microbeads also may be used
in combination with compositions of the present invention.
[0030] At the well site or in the pipelines or gathering lines, the
drag-reducing additive is added to a water-based treatment fluid to
be pumped downhole or through the piping system. In a preferred
embodiment, the drag-reducing additive comprises about 0.05 to 2
gallons of solution per 1000 gallons of water (gpt).
[0031] In a presently preferred embodiment, the drag-reducing
additive is delivered downhole or into a pipeline or gathering line
by continuously adding it to the water-based treatment fluid as the
treatment fluid is pumped, at rates of 0.05 to 5 gallons
drag-reducing additive per 1000 gallons fracturing fluid. The
drag-reducing additive is preferably added to the treatment fluid
at or near the blending device and before the high pressure pumps
in a fracturing treatment. In a friction-reducing application, the
emulsion inverts rapidly as the fracturing fluid proceeds down the
tubulars, allowing the copolymer solution to solubilize in the
aqueous phase. The drag-reducing additive suppresses turbulence and
lowers the necessary pumping pressure.
[0032] The following examples describe tests performed on various
embodiments of the additive, as well as prior art drag-reducing
systems. It will be understood that these examples are merely
illustrative and are not to be considered limiting.
Testing
[0033] Friction loop devices to evaluate friction/drag reduction
are known in the art. The device used to for the following tests
consists of a 15 gallon tank from which fluid is pumped at a
maximum flow rate of 12 gallons per minute (gpm) through a series
of pipes. The first pipe is a 10 feet long with a 0.75 inch outer
diameter (OD) and a 0.62 inch inner diameter (ID). The first pipe
is connected to a 25 foot long, 0.50 inch OD, 0.40 inch ID
stainless steel test pipe. Differential pressure is measured by
means of pressure transducers across a 10 foot section of the test
pipe called the "Test Section." The Test Section begins at a point
10 feet along the test pipe. After the fluid flows through the Test
Section, it is looped back into the pump. The output of the
differential pressure measurements is registered by a computer
running LabVIEW automation software available from the National
Instruments Corporation. It will be understood that other methods
of testing drag reduction may be used.
[0034] In a typical experiment a 15 gallon reservoir is filled with
8 gallons of base fluid comprising either tap water or brine, which
will provide a baseline and to verify proper operation of the flow
loop. The base fluid can also be produced water from a well or
other process water. One suitable brine consists of 7% by weight
potassium chloride solution. The base fluid is recirculated for 2
minutes at a flow rate of 10 gpm, the baseline point is recorded,
and the flow loop is then stopped. The drag-reducing additive or
prior art drag reducer is then injected using a 60 ml syringe at
doses between 0.05 to 2 gpt. The fluid is then recirculated in the
loop. The flow rate initially is set at 12 gpm and then ramped down
to 2 gpm in 2 gpm increments. At each flow rate the fluid is
recirculated for 60 seconds. After 2 gpm flow rate has been
reached, the flow rate is ramped back to 12 gpm in 2 gpm
increments. This part of test is referred to as "ramping." After
the last 12 gpm setting is reached, the flow rate is reduced to 10
gpm and the liquid is allowed to further recirculate in the loop
for 10 minutes. This part of experiment is referred to as
"recirculation." During recirculation differential pressure is
measured at the beginning (t=0) and at the end (t=10 min) of the
process. Performing the drag reduction experiment in such way
allows one to simulate situations of changing flow rate gradients
typically encountered in the oilfield, such as in performing
hydraulic fracturing jobs. The percent friction reduction (% FR) is
calculated at each flow rate as follows:
% FR = DP BL - DP S DP BL .times. 100 % ##EQU00001##
where DP.sub.BL and DP.sub.S are the differential pressures
obtained without and with drag reducing system, respectively. The
value of DP.sub.BL represents 100% friction baseline for water or
brine.
[0035] At each flow rate, the value of DP.sub.BL is calculated
using the following set of equations:
.DELTA. P BL = L .times. v .times. .rho. .times. f 25.8 .times. D
##EQU00002## v = Q 2.45 .times. D 2 ##EQU00002.2## f = 0.3164 4
.times. Re 0.25 ##EQU00002.3## Re = 928 .times. D .times. v .times.
.rho. .mu. ##EQU00002.4##
where L is the length of the test section measured in inches, v is
fluid velocity in ft/sec, .rho. is the fluid density in lb/gal, D
is the internal diameter of the pipe measured in inches, Q is
volumetric flow in gals/min, f is the Fanning friction factor, Re
is Reynolds number, and .mu. is dynamic viscosity of the liquid in
cP. The units for differential pressures are psi.
Core Permeability Testing
[0036] The impact of samples on core permeability was evaluated
with a Formation Response Tester (FRT) using the following method.
First, a 2 inch long, 1 inch diameter section is cut out of an Ohio
sandstone core with a permeability around 1 milliDarcy (mD) using a
lapidary trim saw. The cut core is then washed with water and dried
overnight at 230.degree. F. The wash water is preferably around
2.0% KCl so as to not damage clays that may be present in the core.
Diameter and length of the core are measured with a caliper. The
core is then deaerated under vacuum at 28-30 inches of mercury (in
Hg) for 2 hours and saturated with 7% KCl brine overnight. The
saturated core is then placed in the core holder chamber of the FRT
instrument, at room temperature. The core chamber is subjected to
1500 psi confining pressure and 500 psi back pressure. Permeability
of the core is measured in production this permeability is taken as
the initial permeability value, After production flow has been
stopped, 1 gallon of 0.166 volume % solution of the drag-reducing
additive in 7% KCl brine is flowed across the end of the core at a
flow rate of 0.8 L/min for 30 minutes under the applied 100 psi
pressure gradient. After the solution containing the drag-reducing
additive has been pumped for 30 minutes, the core is again flooded
in production direction using the same conditions as used in
determining initial permeability. Final permeability of the core,
K.sub.f, is determined. The percentage of permeability regained due
to the use of the samples is then calculated as
K f K j .times. 100 % . ##EQU00003##
Rheology Measurements
[0037] Rheological measurements were performed to characterize
materials of the present invention using the AR-G2 rheometer with
40 mm 2.degree. cone-and-plate geometry from TA instruments. In a
typical experiment a sinusoidal oscillating strain was applied to a
sample at a frequency of 1 Hz (.omega.=6.283 radians per s), and
stress varied between 0.05 and 150 Pa. Details of rheological
measurements and meaning of principal rheological parameters are
known to those skilled in the art. Materials of the present
invention, as well as the emulsion polymers of the prior art, can
be characterized by a combination of elastic (G') and viscous (G'')
modulus. The magnitude of complex viscosity, .eta.*, can be
calculated as
.eta. * = [ ( G '' .omega. ) 2 + ( G ' .omega. ) 2 ] 1 / 2
##EQU00004##
Example 1
[0038] In a beaker, 22.5 grams of an ethoxylated castor oil
surfactant such as Stepantex CO-30, available from Stepan
Corporation, are mixed with 17.5 grams of d-limonene. The mixture
is stirred until clear amber-colored solution is obtained. To this
mixture is added 60 grams of the polymer described in Samples 1-1
through 1-3 below. The resulting mixture is then stirred at 300 rpm
until a homogeneous, flowable formulation is obtained. Friction
reducing performance and effect on core permeability are then
evaluated as described above. Within the teachings of this example,
the following samples were prepared:
[0039] Sample 1-1: Drag-reducing additive in which the polymer is
the anionic copolymer emulsion of acrylamide sodium acrylate, such
as Hychem AE853, available from Hychem, Inc. This sample had an
elastic modulus G'=9.6 Pa, viscous modulus G''=8.8 Pa, complex
viscosity of 2.1 Pa s, and did flow easily. Both of these values
were much lower than the corresponding values established for AE853
polymer, which had G'=237.4 Pa, G''=70 Pa, and |.eta.*|=39.4 Pa
s.
[0040] Sample 1-2: Drag-reducing additive in which the polymer is a
nonionic polyacrylamide emulsion. In a preferred embodiment, the
polymer is Hychem NE823, available from Hychem, Inc.
[0041] Sample 1-3: Drag-reducing additive in which the polymer is a
cationic copolymer emulsion of acrylamide and
dimethylaminoethylacrylate methyl chloride quarternary salt (DMAEA
MCQ), such as Hychem CE335, available from Hychem, Inc.
[0042] Table 1 summarizes the drag reduction performance of Samples
1-1 through 1-3, as well as the performance of constituent
conventional polymer emulsions used alone. The dosing of both the
Samples and the conventional polymer emulsions is 1 gpt of the
conventional polymer emulsion.
TABLE-US-00001 TABLE 1 % Friction % Friction Reduction in Reduction
in 7% Sample Flow rate (gpm) Water KCl Brine Sample 1-1 Ramping 12
77 77 6 71 72 12 77 77 Recirculation 10 (t = 0 min) 76 74 10 (t =
10 min) 76 76 Sample 1-2 Ramping 12 78 77 6 55 68 12 61 67
Recirculation 10 (t = 0 min) 55 61 10 (t = 10 min) 48 54 Sample 1-3
Ramping 12 77 79 6 72 74 12 78 77 Recirculation 10 (t = 1 min) 77
75 10 (t = 10 min) 77 69 AE853 Ramping 12 75 70 6 69 60 12 75 66
Recirculation 10 (t = 0 min) 76 64 10 (t = 10 min) 76 62 NE823
Ramping 12 78 77 6 63 52 12 64 62 Recirculation 10 (t = 0 min) 58
57 10 (t = 10 min) 50 51 CE335 Ramping 12 78 62 6 73 64 12 79 75
Recirculation 10 (t = 0 min) 77 72 10 (t = 10 min) 77 60
[0043] Table 1 illustrates that although all Samples are effective
drag reducers, some are more preferable than others. As such,
microemulsified polymer systems made with anionic polymers are
preferred over those made with a nonionic or cationic polymers.
Table 1 also illustrates the benefit of using the Samples over
conventional polymers. Table 1 indicates a rapid decrease in the
percent friction reduction achieved with conventional drag reducing
polymer emulsions upon transition from water to 7% KCl brine, while
this is not the case with the Samples. Also, under equivalent
conditions, the Samples yielded consistently higher values of
friction reduction than the corresponding polymer emulsions alone.
The data in Table 1 also indicates that in brine, cationic drag
reducing polymer Hychem CE335 had to be recirculated in the loop
for a substantial period of time until the optimum drag reduction
of 75% was achieved, while the system of the present invention
based on the same polymer achieved this high level of drag
reduction immediately.
Example 2
[0044] In a beaker, 20 grams of ethoxylated castor oil are mixed
with 20 grams of terpene. The mixture is stirred until clear
amber-colored solution is obtained. To this mixture is added 60
grams of the copolymer described in Sample 2-1, 2-2, or 2-3 below.
The resulting mixture is then stirred at 300 rpm until a
homogeneous, flowable formulation is obtained. Friction reducing
performance and effect on core permeability are then evaluated as
described above. Within the teachings of this example, the
following samples were prepared:
[0045] Sample 2-1: A copolymer emulsion of acrylamide and sodium
acrylate is combined with ethoxylated castor oil surfactant and
peppermint oil terpenes according to the procedure in Example 2
above. In a preferred embodiment, the copolymer emulsion is Hychem
AE853, available from Hychem, Inc., and the ethoxylated castor oil
surfactant is Stepantex CO-30, available from Stepan Corporation.
The peppermint oil terpene is available from GreenTerpene.com.
[0046] Sample 2-2: A copolymer emulsion of acrylamide and sodium
acrylate is combined with ethoxylated castor oil surfactant and
eucalyptus oil terpenes according to the procedure in Example 2
above. In a preferred embodiment, the copolymer emulsion is Hychem
AE853, available from Hychem, Inc., and the ethoxylated castor oil
surfactant is Stepantex CO-30, available from Stepan Corporation.
The eucalyptus oil terpene is available from GreenTerpene.com.
[0047] Sample 2-3: A copolymer emulsion of and sodium acrylate is
combined with a sorbitan monooleate surfactant and a terpene
comprising d-limonene according to the procedure in Example 2
above. In a preferred embodiment, the copolymer emulsion is Hychem
AE853, available from Hychem, Inc., and the surfactant is TWEEN 80.
The d-limonene is available from Florida Chemical Company.
[0048] Drag reduction performance of Samples 2-1 through 2-3 in 7%
KCl brine is summarized in Table 2. The dosing of both the Samples
and the conventional polymer emulsions is 1 gpt of the conventional
polymer emulsion.
TABLE-US-00002 TABLE 2 % Friction Reduction in Sample Flow rate 7%
KCl Brine Sample 2-1 Ramping 12 77 6 73 12 77 Recirculation 10 (t =
0 min) 75 10 (t = 10 min) 74 Sample 2-2 Ramping 12 77 6 73 12 77
Recirculation 10 (t = 0 min) 76 10 (t = 10 min) 74 Sample 2-3
Ramping 12 77 6 72 12 77 Recirculation 10 (t = 0 min) 75 10 (t = 10
min) 74
[0049] Table 2 shows that Samples 2-1 through 2-3 caused a
reduction in friction by more than 70% and were superior to drag
reducing polymer AE853 used alone (Table 1).
[0050] The results of core permeability evaluation with systems of
the invention indicated that samples from both Table 1 and Table 2
yielded regained permeability of greater than 74%. Sample 1-1,
which is a particularly preferred embodiment, yielded regained
permeability of 97%.
Example 3
[0051] To 27.3 g of ethoxylated castor oil surfactant (Stepantex
CO-30), 72.7 g of Hychem AE853 copolymer emulsion was added, and
the mixture was stirred to form Sample 3. Formulation of a
paste-like, highly viscous material was observed. The paste was
loaded into a syringe and extruded into the base liquid to achieve
a dose of 1 gpt based on polymer actives. This sample had an
elastic modulus G'=234 Pa, viscous modulus G''=87 Pa, and complex
viscosity |.eta.*|=42 Pa s. This material was much less flowable
than both material of example 1-1 and prior art friction reducer
Hychem AE853, as indicated by significantly higher values of G' and
|.eta.*|.
TABLE-US-00003 TABLE 3 % Friction Reduction in Sample Flow rate 7%
KCl Brine Sample 3 Ramping 12 76 6 71 12 76 Recirculation 10 (t = 0
min) 75 10 (t = 10 min) 75
[0052] The compositions of the present invention can be used for
aiding in the recovery of crude oil and natural gas from
subterranean formations. It is possible to use these compositions
by a variety of means. For example, in one suitable embodiment,
compositions of the present invention may be delivered to the use
site as a single formulation. To make such formulation, it is
possible to mix the components in any order. In the other suitable
unlimited embodiment, the individual components making compositions
of this invention can be mixed "on the fly". Other means of using
the systems of this invention may include, but are not limited to
pre-dissolving one or more components in the treatment fluid or
pre-blending two or more components prior to the addition of a
third one. In preferred embodiments, acceptable treatment ranges
may include adding from about 0.01 gallons to 50 gallons of
drag-reducing additive per 1,000 gallons of the aqueous treatment
fluid.
[0053] It is clear that the present invention is well adapted to
carry out its objectives and attain the ends and advantages
mentioned above as well as those inherent therein. While presently
preferred embodiments of the invention have been described in
varying detail for purposes of disclosure, it will be understood
that numerous changes may be made which will readily suggest
themselves to those skilled in the art and which are encompassed
within the spirit of the invention disclosed and claimed
herein.
* * * * *