U.S. patent application number 14/087440 was filed with the patent office on 2014-05-29 for crosslinking of swellable polymer with pei.
This patent application is currently assigned to UNIVERSITY OF KANSAS. The applicant listed for this patent is CONOCOPHILLIPS COMPANY, UNIVERSITY OF KANSAS. Invention is credited to Cory BERKLAND, Min CHENG, Terry M. CHRISTIAN, Huili GUAN, James H. HEDGES, Jenn-Tai LIANG, Ahmad MORADI-ARAGHI, Riley B. NEEDHAM, Ramesh S. SARATHI, Faye L. SCULLY.
Application Number | 20140144628 14/087440 |
Document ID | / |
Family ID | 50772250 |
Filed Date | 2014-05-29 |
United States Patent
Application |
20140144628 |
Kind Code |
A1 |
MORADI-ARAGHI; Ahmad ; et
al. |
May 29, 2014 |
CROSSLINKING OF SWELLABLE POLYMER WITH PEI
Abstract
The invention is directed to stable and labile crosslinked water
swellable polymeric microparticles that can be further gelled,
methods for making same, and their various uses in the hygiene and
medical arts, gel electrophoresis, packaging, agriculture, the
cable industry, information technology, in the food industry,
papermaking, use as flocculation aids, and the like. More
particularly, the invention relates to a composition comprising
expandable polymeric microparticles having labile crosslinkers and
stable crosslinkers, said microparticle mixed with a fluid and an
unreacted tertiary crosslinker comprising PEI or other polyamine
based tertiary crosslinker that is capable of further crosslinking
the microparticle on degradation of the labile crosslinker and
swelling of the particle, so as to form a stable gel. A
particularly important use is as an injection fluid in petroleum
production, where the expandable polymeric microparticles are
injected into a well and when the heat and/or pH of the well cause
degradation of the labile crosslinker and when the microparticle
expands, the tertiary crosslinker crosslinks the polymer to form a
stable gel, thus diverting water to lower permeability regions and
improving oil recovery.
Inventors: |
MORADI-ARAGHI; Ahmad;
(Bixby, OK) ; CHENG; Min; (Bartlesville, OK)
; NEEDHAM; Riley B.; (Bartlesville, OK) ; HEDGES;
James H.; (Bartlesville, OK) ; SARATHI; Ramesh
S.; (Bartlesville, OK) ; SCULLY; Faye L.;
(Bartlesville, OK) ; CHRISTIAN; Terry M.;
(Bartlesville, OK) ; GUAN; Huili; (Lawrence,
KS) ; BERKLAND; Cory; (Lawrence, KS) ; LIANG;
Jenn-Tai; (Lawrence, KS) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNIVERSITY OF KANSAS
CONOCOPHILLIPS COMPANY |
LAWRENCE
HOUSTON |
KS
TX |
US
US |
|
|
Assignee: |
UNIVERSITY OF KANSAS
LAWRENCE
KS
CONOCOPHILLIPS COMPANY
HOUSTON
TX
|
Family ID: |
50772250 |
Appl. No.: |
14/087440 |
Filed: |
November 22, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61729682 |
Nov 26, 2012 |
|
|
|
Current U.S.
Class: |
166/275 ;
507/226 |
Current CPC
Class: |
C09K 8/588 20130101;
E21B 43/16 20130101; E21B 33/138 20130101 |
Class at
Publication: |
166/275 ;
507/226 |
International
Class: |
C09K 8/588 20060101
C09K008/588 |
Claims
1. A composition comprising expandable acrylamide-based polymeric
microparticles having labile crosslinkers and stable crosslinkers,
said microparticles combined with a fluid and an unreacted tertiary
crosslinker comprising polyethyleneimine ("PEI") that is capable of
further crosslinking the microparticles upon degradation of the
labile crosslinker so as to form a stable gel.
2. The composition of claim 1, wherein said microparticles comprise
polyacrylamide.
3. The composition of claim 1, wherein the microparticles comprise
a copolymer of an acrylamide and an acid or salt form of
2-acrylamido-2-methylpropane sulfonate.
4. The composition of claim 1, wherein the stable crosslinker is
methylene bisacrylamide and the labile crosslinker is a
polyethylene glycol diacrylate.
5. The composition of claim 1, wherein said microparticles comprise
a copolymer of acrylamide and 2-acrylamido-2-methylpropane
sulfonate, the stable crosslinker comprises methylene
bisacrylamide, and the labile crosslinker comprises a polyethylene
glycol diacrylate.
6. The composition of claim 1, wherein the expandable polymeric
microparticles comprises a copolymer of acrylamide and
2-acrylamido-2-methylpropane sulfonate, the stable crosslinker
comprises 1 to about 300 ppm methylene bisacrylamide, the labile
crosslinker comprises 9,000 to about 200,000 ppm polyethylene
glycol diacrylate, and the tertiary crosslinker comprises 200-2000
ppm PEI and a fluid containing water.
7. A composition comprising highly cross linked expandable
hydrophilic polymeric microparticles having an unexpanded volume
average particle size diameter of about 0.05-10 microns and a cross
linking agent content of about 10,000-250,000 ppm of labile
crosslinkers and about 1-500 ppm of stable cross linkers, combined
with about 200-2000 ppm of unreacted PEI and a fluid comprising
water.
8. The composition of claim 7, wherein said microparticles comprise
polyacrylamide or partially hydrolyzed polyacrylamide.
9. The composition of claim 7, wherein said microparticles comprise
a copolymer of acrylamide and 2-acrylamido-2-methylpropane
sulfonate.
10. The composition of claim 7, wherein the stable crosslinker is
methylene bisacrylamide and the labile crosslinker is a
diacrylate.
11. The composition of claim 8, wherein said microparticles
comprise a copolymer of acrylamide and 2-acrylamido-2-methylpropane
sulfonate, the stable crosslinker comprises methylene
bisacrylamide, and the labile crosslinker comprises a polyethylene
glycol diacrylate.
12. A composition comprising: a) a highly crosslinked expandable
hydrophilic polymeric microparticle; b) said microparticle having
an unexpanded average particle size diameter of 0.05-10 microns; c)
said hydrophilic polymer having amine/amide groups; d) said
hydrophilic polymer being internally crosslinked with
10,000-250,000 ppm of labile crosslinkers and 1-500 ppm of stable
crosslinkers; and e) said microparticle combined with 200-2000 ppm
of unreacted tertiary crosslinker that can further crosslink said
hydrophilic polymer, wherein said tertiary crosslinker is selected
from the group consisting of polyalkyleneimine, a
polyethyleneimine, a polyalkylenepolyamine, PEI, simple polyamines,
methylene diamine, ethylene diamine, hexamethylene diamine, and
hexamethylene triamine.
13. The composition of claim 12, said hydrophilic polymer
comprising polymers and copolymers of acrylamide and derivatives
thereof.
14. The composition of claim 12, wherein the stable crosslinker is
methylene bisacrylamide and the labile crosslinker is a
diacrylate.
15. The composition of claim 13, wherein the stable crosslinker is
methylene bisacrylamide and the labile crosslinker is a
diacrylate.
16. The composition of claim 12, further comprising a tertiary
crosslinker retarder.
17. The composition of claim 12, further comprising a carbonate
retarder.
18. A method of increasing the recovery of hydrocarbon fluids in a
subterranean formation, comprising injecting into the subterranean
formation a mixture comprising water and the composition of claim
1, aging said mixture until it gels, and then producing hydrocarbon
from said subterranean formation.
19. A method of increasing the recovery of hydrocarbon fluids in a
subterranean formation, comprising: a) injecting into the
subterranean formation a mixture comprising water and expandable
acrylamide-based polymeric microparticles having labile
crosslinkers and stable crosslinkers, and b) injecting an unreacted
tertiary crosslinker into the subterranean formation, wherein said
tertiary crosslinker is selected from the group consisting of
polyalkyleneimine, a polyethyleneimine, a polyalkylenepolyamine,
polyethyleneimine, simple polyamines, methylene diamine, ethylene
diamine, hexamethylene diamine, and hexamethylene triamine.
20. The method of claim 19, wherein steps a) and b) occur at
different times or the same time.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Ser. No.
61/729,682, filed Nov. 26, 2012, and expressly incorporated by
reference herein it its entirety.
FEDERALLY SPONSORED RESEARCH STATEMENT
[0002] Not applicable.
REFERENCE TO MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] The invention relates to stable crosslinking of swellable
polymers, methods for making same, and their various uses in the
hygiene and medical arts, gel electrophoresis, packaging,
agriculture, the cable industry, information technology, in the
food industry, papermaking, use as flocculation aids, and the like.
A particularly important use is as an injection fluid in petroleum
production, especially in enhanced oil recovery (EOR)
applications.
BACKGROUND OF THE INVENTION
[0005] Every day, oil and gas companies are challenged to produce
as much of their oil reserves as possible. During the primary
recovery stage, reservoir drive comes from a number of natural
mechanisms. These include: natural water pushing oil into the well,
expansion of the natural gas at the top of the reservoir, expansion
of gas initially dissolved in the crude oil, and gravity drainage
resulting from the movement of oil within the reservoir from the
upper to the lower parts where the wells are located. Recovery
factor during the primary recovery stage is typically 5-15%.
[0006] Over the lifetime of an oil well, however, the pressure will
fall, and at some point there will be insufficient underground
pressure to force the oil to the surface. After the natural
reservoir drive diminishes, secondary and tertiary recovery methods
are applied to further increase recovery.
[0007] Secondary recovery methods rely on the supply of external
energy into the reservoir in the form of injecting fluids to
increase reservoir pressure, hence replacing or increasing the
natural reservoir drive with an artificial drive. Sometimes pumps,
such as beam pumps and electrical submersible pumps (ESPs), are
used to bring the oil to the surface. Other secondary recovery
techniques increase the reservoir's pressure by water injection,
natural gas reinjection and gas lift, which injects air, carbon
dioxide or some other gas into the bottom of an active well,
reducing the overall density of fluid in the wellbore.
[0008] The water injection method used in oil production is where
water is injected into the reservoir for two reasons. First, the
water provides pressure support of the reservoir (also known as
voidage replacement). Second, the water functions to sweep or
displace the oil from the reservoir, and push it towards oil
production wells. Typical recovery factor from water-flood
operations is about 30%, depending on the properties of oil and the
characteristics of the reservoir rock. On average, the recovery
factor after primary and secondary oil recovery operations is
between 35 and 45%.
[0009] However, oil recovery is limited by the so-called "thief
zones," whereby water (or other injected fluid) preferentially
travels through the more porous regions of the reservoirs, thus
bypassing less porous zones and leaving oil behind. One way to
further improve oil recovery is to block the thief zones with a
polymer or other material, thus forcing injected fluid through the
less porous regions and causing a more effective sweep of the
reservoir.
[0010] Gels are used for a variety of reasons in drilling and
production applications. These fluids can be optimized for each
reservoir by controlling the gelation process and are often used to
block thief zones. U.S. Pat. No. 4,773,481, for example, describes
the injection of a water soluble polymer, such as polyacrylamide,
plus a gelling agent, such as PEI, into the thief zones, and thus
plugging the thief zones.
[0011] U.S. Pat. No. 6,454,003 et seq, describes what might be
called a "smart gel" since its properties change in response to
particular stimuli. This patent describes an expandable crosslinked
polymeric microparticle having an average particle diameter of
about 0.05 to 10 microns. The particle is highly crosslinked with
two crosslinkers--small amounts of one that is stable and a second
that is labile and present in great excess. The excess crosslinking
makes the initial particles quite small, allowing efficient
propagation through the pores of a reservoir. On heating to
reservoir temperature and/or at a predetermined pH or other
stimuli, the reversible (labile) internal crosslinks break,
allowing the particle to further expand by absorbing additional
injection fluid, usually water. The unique properties of this
particle allows it to fill the high permeability zones--commonly
called thief zones or streaks--and then be expanded so that the
swollen particle blocks the thief zones and subsequent injections
of fluid are forced to enter the remainder of the reservoir, more
effectively sweeping the reservoir.
[0012] One commercially available swellable polymer of this type is
BrightWater.RTM.. Conventional partially hydrolyzed polyacrylamide,
PHPAM, is quite viscous and requires a lot of horsepower for
injection. Further, the viscous polymers often shear as they enter
the formation. In contrast, the tiny BrightWater.RTM.
microparticles can easily be injected without the need for high
power pumps and the polymer thus avoids shear degradation during
pumping. The BrightWater.RTM. microparticles also shows improved
mobility control due to expansion ("popping") of the polymeric
microparticles as a result of exposure to heat or varying pH
values. However, the resulting "popped" polymers, which initially
exhibit good resistance factors, appear to washout of the porous
media with subsequent water injection. As a result, such treatments
are short lasting and might not payoff the somewhat expensive
treatment cost.
[0013] FIG. 2 shows the results of a 40' long slim tube (eight 5'
sections, i.d.=3/8'') packed with 1.0 Darcy sand treated with 0.5%
BrightWater.RTM. (NALCO CHEMICAL.TM., IL) in a field brine. Upon
exposure to heat at 190.degree. F., the microparticles started to
open up due to hydrolysis of the labile crosslinker bonds. As this
figure shows, the polymeric microparticles initially exhibit
acceptable resistance factor (RF) in the range of 25 to 30 in this
test. However, these values decrease with additional water
injection, eventually resulting in very small residual resistance
factors (RRF). FIG. 2 shows that the residual resistance factors
for all eight sections of the slim tubes dropped substantially
within one pore volume of brine injection. This and several other
experiments performed in our laboratories confirm that the benefit
of BrightWater.RTM. treatment is temporary.
[0014] The reason for the washout is not certain, but probably
relates to several factors. First, most swellable polymers are also
squeezable under pressure. Thus, when the reservoir pressure
increases on further injection of fluid, the swollen particles wash
out of the thief zone. Further, our own research suggests that the
swollen polymer is not in gel form, thus, although viscous, is a
liquid and can be washed out of the porous substrate.
[0015] What is needed in the art is a more stable "smart gel" that
is gel stabilized and less susceptible to loss of fluid or polymer
under the conditions of use. In particular, a swellable polymer
that is resistant to wash out by subsequent fluid injections is
needed in oil production, but the polymers will have utility in any
application where stable swellable smart gels are desired.
[0016] The ConocoPhillips Company and The University of Kansas have
already performed considerable research in the area of stabilizing
these swellable polymers to washout. See e.g., US2010234252,
US2010314115, US2010292109, and US2010314114.
[0017] However, further improvements could be made, in particular
by making such products more effective, less expensive, and/or
reducing environmental impact. For example, tertiary crosslinkers
such as phenol-formaldehyde have been used with BrightWater-type
swellable polymers, but they are toxic and have significant
environmental impact.
SUMMARY OF THE INVENTION
[0018] The invention generally relates to smart gels that have
stable and labile crosslinkers, allowing swelling in situ in
response to a particular stimulus. Further, the swelled polymer is
stabilized in situ by further crosslinking, thus forming a gel
structure. In preferred embodiments, the amide groups of the fully
hydrated acrylamide-based polymers are crosslinked with e.g.,
polyethyleneimine (PEI), to form a stable three dimensional gel
network, very resistant to washout, and yet being more
environmentally friendly than swellable polymers that were
crosslinked in situ using phenol and formaldehyde. The PEI
cross-linker has even been approved for food contact in the USA,
confirming its low toxicity. Furthermore, the PEI tertiary
crosslinker has applicability in high temperature reservoirs. Plus,
since the crosslinking is covalent, it is more stable than ionic
bonds.
[0019] PEI is well known to form thermally stable gels with
acrylamide based polymers, such as copolymers of acrylamide and
tert-butyl acrylate (PAtBA), copolymers of acrylamide and
acryamido-2-methylpropane sulfonic acid (AMSA), copolymers of
acrylamide and sodium 2-acryamido-2-methylpropane sulfonate
(NaAMPS), copolymers of acrylamide, AMSPA, and N,N,-dimethyl
acrylamide, as well as partially hydrolyzed polyacrylamide
(PHPAM).
[0020] These PEI crosslinked gel systems have been extensively
studied in porous media. The gelation time and strength of e.g., a
PEI and polymer gel system can be controlled by adjusting the
polymer concentration and molecular weight, the PEI concentration,
the total dissolved solids and salinity. The polymer concentration
and molecular weight affects not only the gelation time and the gel
strength, but also its stability. Among these factors the polymer
concentration is the most important factor affecting gel strength.
For the same polymer, adhesive force and final gel strength of the
higher MW gels are superior to gels made with lower MW polymers at
the same concentration. Further, the gelation time decreases and
gelation strength weakens with increasing the salinity of gelling
solution. Gelation time is largely dependent on temperature, but
can be accelerated or retarded with additives. For all of these
reasons, PEI was a good candidate for "popped" BrightWater.RTM.
stabilization by gelation.
[0021] Laboratory experiments performed with swellable polymers of
the BrightWater.RTM. type, but also containing 1000 ppm of PEI (2
KDa) resulted in the formation of a stable gel that could not be
washed out from porous media, even with pressures of up to 1000
psi.
[0022] The polymer of the invention has particular use in enhanced
oil recovery, as described above, and is preferably a hydrophilic
polymer for this application. However, a stable polymer would find
uses in all of the arts where swellable polymers are in current use
and fluid loss is not desired, including as filler for diapers and
other hygiene products, medical devices such as orthopedic insoles,
ocular devices, and biomimetic implants, wipe and spill control
agents, wire and cable water-blocking agents, ice shipping packs,
controlled drug release, agricultural uses (e.g., soil additive to
conserve water, plant root coating to increase water availability,
and seed coating to increase germination rates), industrial
thickeners, specialty packaging, tack reduction for natural rubber,
fine coal dewatering, and the like.
[0023] Preferably, the stable smart gels of the invention comprise
a highly crosslinked expandable polymeric particle having labile
crosslinkers and stable crosslinkers, plus an unreacted tertiary
PEI crosslinker that is added to the particles after they are made
or after the labile crosslinker degrades or any time there in
between.
[0024] In the example described below the tertiary crosslinker is
injected after swelling of the polymer, but it can also be combined
with the unexpanded kernel in the initial injection fluid, and if
necessary for the application, the rate of gelation can be delayed
by means known in the art in order to allow the particle to fully
swell before completing gelation. Furthermore, the dry
microparticle powders can be intimately mixed with unreacted
tertiary crosslinker powders, and thus sold as a mixed powder that
can be combined with fluid and other additives onsite.
[0025] A "stable crosslinker" is defined herein to be any
crosslinker that is not degraded under the stimulus that causes the
labile crosslinker to disintegrate. Representative non-labile
crosslinking monomers include methylene bisacrylamide,
diallylamine, triallylamine, divinyl sulfone, diethyleneglycol
diallyl ether, and the like and combinations thereof. A preferred
non-labile crosslinking monomer is methylene bisacrylamide.
[0026] The "labile crosslinker" is defined herein to be any
crosslinker that decays or is reversible on application of a
particular stimulus, such as irradiation, pH, temperature, etc. and
combinations thereof. Representative labile crosslinkers include
diacrylamides and methacrylamides of diamines such as the
diacrylamide of piperazine, acrylate or methacrylate esters of di,
tri, tetra hydroxy compounds including ethyleneglycol diacrylate,
polyethyleneglycol diacrylate, trimethylopropane trimethacrylate,
ethoxylated trimethylol triacrylate, ethoxylated pentaerythritol
tetracrylate, and the like; divinyl or diallyl compounds separated
by an azo such as the diallylamide of 2,2'-Azobis(isbutyric acid)
and the vinyl or allyl esters of di or tri functional acids, and
combinations thereof. Preferred labile cross linking monomers
include water soluble diacrylates such as PEG 200 diacrylate and
PEG 400 diacrylate and polyfunctional vinyl derivatives of a
polyalcohol such as ethoxylated (9-20) trimethylol triacrylate and
polymethyleneglycol diacrylate.
[0027] Combinations of multiple stable and labile crosslinkers can
also be employed advantageously. Reaction to stimuli can also be
controlled by labile crosslinker selection, as needed for
particular reservoir conditions or for the application at issue.
For example, judicious selection of labile crosslinkers--one that
degrades at a very high temperature and another at a lower
temperature--can affect the temperature and pH at which the kernel
pops.
[0028] The preferred "tertiary crosslinker" used herein is PEI,
because PEI is readily available, cost effective, the gels produced
by this crosslinker are stable, yet provide less environmental
impact than prior art tertiary crosslinkers. Further, PEI
crosslinked gels have been tested under reservoir conditions, and
are known to provide a stable 3D gel structure for extended periods
of time, thus providing effective water shut-off at elevated
reservoir temperatures. Additionally, the PEI crosslinked gels have
longer gelation time than that of commonly used chromium(III)
acetate cross-linking HPAM gel systems at 40.degree. C., thus
allowing them to penetrate deeper into the reservoir before
gelling.
[0029] The gelation mechanism is believed to be a transamidation
mechanism, as shown in FIG. 1. FIG. 1 shows transamidation
mechanism suggested in published literature (SPE 97530). As this
reaction scheme shows, two amide groups from the acrylamide
constituents of the popped Brightwater.RTM. polymer undergo
transamidation reaction with two amine groups of PEI to create
crosslink sites resulting in gels.
[0030] Although PEI is a preferred tertiary crosslinker, there are
many similar amine-based crosslinkers that can serve the same
function, having amine groups that can transamidate with amide
groups in the polymer. Thus, tertiary crosslinkers can include
polyalkyleneimine, a polyethyleneimine, a polyalkylenepolyamine, or
simple polyamines such methylene diamine, ethylene diamine,
hexamethylene diamine, hexamethylene triamine could also be used as
tertiary crosslinkers.
[0031] When employed for enhanced oil recovery applications, the
size range of the unexpanded particle will be selected to accord
with the permeability characteristics of a given reservoir and
increasing labile crosslinker provides smaller particles. Thus, the
size is preferably about 0.05 to about 10 microns, or 1-3 microns,
but the size can vary according to the needs of each application.
Ranges as broad as 0.01 to about 100 microns, or sizes as high as
1000 microns can be acceptable. Further, in certain soil and
spillage applications, the size can be up to a cm, though more
preferably may be 1-5 mm. Generally speaking, the smaller particles
will swell more quickly due to increased surface area to
volume.
[0032] The proportion of stable to labile crosslinker can also vary
depending on how much swelling on stimulus is required, but in the
enhanced oil recovery applications a great deal of swelling is
desired to effectively block the thief zones and increase the
mobilization and/or recovery rate of hydrocarbon fluids present in
the formations. Thus, the labile crosslinker greatly exceeds the
stable crosslinker.
[0033] To obtain sizes in the range of about 0.05 to about 10
microns suitable for injection fluid use the labile crosslinker
content is about 9,000-250,000 ppm or 10,000-200,000 ppm or
20,000-60,000 ppm. The smaller the particle desired, the more
labile crosslinker used. If bigger particles are acceptable, less
labile crosslinker can be used.
[0034] The amount of stable crosslinkers is from 1-1000 ppm or
100-500 ppm or about 300 ppm, but again this can vary based on the
needs of the application.
[0035] The amount of unreacted tertiary crosslinker is in the range
of 100-5,000 ppm, preferably about 200-2000, or more preferred
about 200-1500 ppm, again depending on the application, the more
rigid gels requiring increased concentrations. However, too much
tertiary crosslinker concentration can cause excessive
cross-linking and lead to gel syneresis (expulsion of water from
gel structure due to over crosslinking), especially in brines with
high Ca.sup.2+ and/or Mg.sup.2+ content.
[0036] The polymeric particles can be prepared from any suitable
monomers, including nonionic monomers, cationic monomers, anionic
monomers, and betaine monomers, provided at least one of the
components therein provides the necessary group(s) for
transamidation or PEI crosslinking to occur.
[0037] Representative nonionic monomers include
N-isopropylacrylamide, N,N-dimethylacrylamide,
N,N-diethylacrylamide, dimethylaminopropyl acrylamide,
dimethylaminopropyl methacrylamide, acryloyl morpholine,
hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl
methacrylate, hydroxypropyl methacrylate,
dimethylaminoethylacrylate (DMAEA), dimethylaminoethyl methacrylate
(DMAEM), maleic anhydride, N-vinyl pyrrolidone, vinyl acetate and
N-vinyl formamide. Preferred nonionic monomers include acrylamide,
N-methylacrylamide, N,N-dimethylacrylamide and methacrylamide.
Acrylamide is more preferred.
[0038] Representative anionic monomers that can be used include
acrylic acid, methacrylic acid, maleic acid, itaconic acid,
2-propenoic acid, 2-methyl-2-propenoic acid, 2-acrylamido-2-methyl
propane sulfonic acid, sulfopropyl acrylic acid and other
water-soluble forms of these or other polymerizable carboxylic or
sulphonic acids, sulphomethylated acrylamide, allyl sulphonic acid,
vinyl sulphonic acid, and the like. Preferred anionic monomers
include 2-acrylamido-2-methyl propanesulfonic acid sodium salt,
vinyl sulfonic acid sodium salt and styrene sulfonic acid sodium
salt. 2-Acrylamido-2-methyl propanesulfonic acid sodium salt is
more preferred.
[0039] Representative cationic monomers include the quaternary or
acid salts of dialkylaminoalkyl acrylates and methacrylates such as
dimethylaminoethylacrylate methyl chloride quaternary salt
(DMAEA.MCQ), dimethylaminoethylmethacrylate methyl chloride
quaternary salt (DMAEM.MCQ), dimethylaminoethylacrylate
hydrochloric acid salt, dimethylaminoethylacrylate sulfuric acid
salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt
(DMAEA.BCQ) and dimethylaminoethylacrylate methyl sulfate
quaternary salt; the quaternary or acid salts of
dialkylaminoalkylacrylamides and methacrylamides such as
dimethylaminopropyl acrylamide hydrochloric acid salt,
dimethylaminopropyl acrylamide sulfuric acid salt,
dimethylaminopropyl methacrylamide hydrochloric acid salt and
dimethylaminopropyl methacrylamide sulfuric acid salt,
methacrylamidopropyl trimethyl ammonium chloride and
acrylamidopropyl trimethyl ammonium chloride; and
N,N-diallyldialkyl ammonium halides such as diallyldimethyl
ammonium chloride (DADMAC). Preferred cationic monomers include
dimethylaminoethylacrylate methyl chloride quaternary salt,
dimethylaminoethylmethacrylate methyl chloride quaternary salt and
diallyldimethyl ammonium chloride. Diallyldimethyl ammonium
chloride is more preferred.
[0040] Representative betaine monomers (a net neutral mix of
cationic and anionic monomers) include
N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)-ammonium betaine,
N,N-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl)-ammonium
betaine,
N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium
betaine,
N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium
betaine, N,N-dimethyl-N-acryloxyethyl-N-(3-sulfopropyl)-ammonium
betaine,
N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium
betaine, N-3-sulfopropylvinylpyridine ammonium betaine,
2-(methylthio)ethyl methacryloyl-S-(sulfopropyl)-sulfonium betaine,
1-(3-sulfopropyl)-2-vinylpyridinium betaine,
N-(4-sulfobutyl)-N-methyldiallylamine ammonium betaine (MDABS),
N,N-diallyl-N-methyl-N-(2-sulfoethyl)ammonium betaine, and the
like. A preferred betaine monomer is
N,N-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl)-ammonium
betaine.
[0041] Representative swellable polymers also include polymers and
copolymers of acrylamide. For example, copolymers of acrylamide and
2-acrylamido-2-methyl propane sulfonic acid, copolymers of
acrylamide and 2-acrylamido-2-methyl propane sulfonic acid sodium,
potassium or ammonium salts, copolymers of acrylamide and sodium
acrylate, terpolymers of acrylamide, 2-acrylamido-2-methyl propane
sulfonic acid and sodium acrylate.
[0042] The kernels can be prepared by methods known in the art,
including the inverse emulsion polymerization technique described
in U.S. Pat. No. 6,454,003, U.S. Pat. No. 6,729,402 and U.S. Pat.
No. 6,984,705.
[0043] Kernel suspensions are prepared by mixing the tertiary
crosslinker with the kernels and injection fluid, although as noted
above, the tertiary crosslinker can be provided in an intimate
mixture of crosslinker and microparticles, in which case, only
fluid need be added.
[0044] In addition to the monomers that make up the polymeric
kernel and three types of crosslinkers (two of which form the
kernel polymer and one of which is unreacted until placed in situ),
the aqueous solution may also contain other conventional additives
including chelating agents to remove polymerization inhibitors, pH
adjusters, initiators and other conventional additives,
accelerators, retardants, as appropriate for the particular
application. In addition, chemicals can be added that will reduce
the adsorption of gelation chemicals to the oil reservoir.
[0045] The rate of gelation with the unreacted tertiary crosslinker
can be controlled, as is known in the art. For example, SPE139308
describes a water-soluble carbonate retarder (0-10%), that has been
added to a PEI crosslinking gel to delay the in situ cross linking
time and allow reasonable placement times in reservoirs up to
350.degree. F. Such retarders include sodium carbonate, sodium
bicarbonate, lithium carbonate, lithium bicarbonate, potassium
carbonate, potassium bicarbonate, ammonium carbonate, or ammonium
bicarbonate. Additionally, temperature and pH can also affect the
rate of gelation, as needed for a particular application. In
addition, the gels can be destroyed with the use of strong
oxidizing agents such as sodium hypochlorite.
[0046] In various embodiments, the invention can comprise one or
more of the following:
[0047] A composition comprising expandable acrylamide-based
polymeric particles having labile crosslinkers and stable
crosslinkers, said particles combined with a fluid and an unreacted
tertiary crosslinker comprising polyethyleneimine ("PEI") that is
capable of further crosslinking the particles on degradation of the
labile crosslinker so as to form a stable gel.
[0048] Preferably, the particles have acrylamide therein, or at
least amide groups that can be transamidated. Particularly
preferred particles comprise polyacrylamide, or partially
hydrolyzed polyacrylamide, copolymer of acrylamide and sodium
2-acrylamido-2-methylpropane sulfonate. Preferably, the stable
crosslinker is methylene bisacrylamide and the labile crosslinker
is a diacrylate, or polyethylene glycol diacrylate.
[0049] In another embodiment, the invention is a composition
comprising highly cross linked expandable hydrophilic polymeric
microparticles having an unexpanded volume average particle size
diameter of about 0.05-10 microns and a cross linking agent content
of about 100,000-250,000 ppm of labile crosslinkers and about 1-500
ppm of stable cross linkers, combined with about 200-2000 ppm of
unreacted PEI and a fluid comprising water, wherein the particles
and crosslinkers are as herein described.
[0050] In another embodiment, the invention is a composition
comprising a highly crosslinked expandable hydrophilic polymeric
microparticle, preferably about 0.05-10 microns, and said
hydrophilic polymer having amine/amide groups. The hydrophilic
polymer can have an internal (reacted) crosslinker content of
10,000-250,000 ppm of labile crosslinkers and 1-500 ppm of stable
crosslinkers. This microparticle can be combined with a fluid and
200-2000 ppm of unreacted tertiary crosslinker that can further
crosslink said hydrophilic polymer, wherein said tertiary
crosslinker is selected from the group consisting of
polyalkyleneimine, a polyethyleneimine, a polyalkylenepolyamine,
PEI, simple polyamines, methylene diamine, ethylene diamine,
hexamethylene diamine, and hexamethylene triamine. The tertiary
crosslinker can be premixed with the microparticle, co-injected
therewith, or the two can be injected separately.
[0051] Methods of increasing the recovery of hydrocarbon fluids in
a subterranean formation are also provided, comprising injecting
into the subterranean formation a mixture comprising water and the
compositions herein described, aging said mixture until it gels,
and then producing hydrocarbon from said subterranean formation.
The tertiary crosslinker can be premixed with the microparticles,
co-injected at the same time, or the two can be injected
separately, as desired.
[0052] As used herein ppm refers to weight ratio in parts per
million, based on total weight.
[0053] As used herein a microparticle is about 0.05-10 microns in
average size.
[0054] As used herein, "polymers" includes homopolymers and
heteropolymers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIG. 1. Transamidation of the amide group.
[0056] FIG. 2. Results of Slim Tube testing of the BrightWater.RTM.
polymer.
[0057] FIG. 3. Viscosity versus Aging Time for 0.5%
BrightWater.RTM. EC 9408A with (black diamonds) or without (hollow
diamonds) 1000 ppm PEI (25 KD), which was prepared in Brine A and
aged at 190.degree. F.
[0058] FIG. 4. Viscosity versus Aging Time for 0.5%
BrightWater.RTM. EC 9408A with (black square) or without (hollow
square) 1000 ppm PEI (25 KD), which was prepared in Brine A and
aged at 150.degree. F.
[0059] FIG. 5. Viscosity versus Aging Time for 0.5%
BrightWater.RTM. EC 9408A with (black shapes) or without (hollow
shapes) 1000 ppm PEI (25 KDa), which was prepared in Brine A and
aged at 150.degree. F. and 190.degree. F.
[0060] FIG. 6. Viscosity versus aging time for an anionic polymeric
microparticle and 1000 ppm PEI prepared in synthetic Brine A and
aged at 150.degree. F. (triangles) and 190.degree. F. (diamonds).
The anionic polymeric microparticle is a swellable copolymer of
acrylamide and sodium acrylate crosslinked with poly(ethylene
glycol) (258) diacrylate and methylene bisacrylamide.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0061] The invention provides a novel polymer that swells on a
stimulus and is then additionally crosslinked in situ to form a
gel. Such smart gels have particular utility in sweeping
reservoirs, but many uses are possible.
[0062] Extensive experiments performed with an expandable polymer,
as described in U.S. Pat. No. 6,454,003, U.S. Pat. No. 6,729,402
and U.S. Pat. No. 6,984,705, demonstrated that this polymer swells
as a result of aging at elevated temperature or exposure to acidic
or caustic conditions. The copolymer of acrylamide and sodium AMPS
is crosslinked with two crosslinkers. The first crosslinker is a
stable crosslinker such as methylene bis-acrylamide in the range of
1-300 ppm, while the second crosslinker is a labile (unstable)
compound such as PEG-200, or PEG-400, a diacrylate crosslinker that
breaks down when exposed to high temperatures or changes in pH. The
resulting doubly-crosslinked polymer results in a small particle
size, ranging at 0.05 to 10 microns.
[0063] Such small particle polymers exhibit very low viscosity when
suspended in water, a desirable property that improves injectivity,
for treating high permeability zones deep in oil bearing
formations. These low viscosity (water-like) micro-particle
solutions are injected into the thief zones of the reservoirs with
very little pressure requirement for penetration.
[0064] If the reservoir temperature is high enough, or another
suitable stimulus is applied, the labile crosslinker undergoes
hydrolysis and breaks down allowing the microparticle or "kernel"
to expand or "pop," thus increasing the viscosity of the solution.
The resulting "popped" polymer diverts the subsequent water
injection away from the thief zones into lower permeability oil
zones to produce additional oil.
[0065] Experiments performed with these micro-particles injected
into 40' slim tubes packed with sand showed impressive resistance
factors in all eight 5' sections of the slim tubes after aging at
elevated temperatures (150-190.degree. F.). However, our research
also indicated that resistance to flow of water gradually
diminished with additional water injection indicating polymer
wash-out in porous media--a highly undesirable property. See e.g.,
FIG. 2.
[0066] We therefore undertook to prevent wash-out of expandable
polymers, and discovered that when PEI was combined with the above
swellable polymer, the resulting gel remained extremely stable to
washout, even at high pressure!
[0067] The function of the PEI tertiary crosslinker in this
application is not proven, but probably uses a mechanism similar to
the following: The unswelled microparticles contain a copolymer of
acrylamide and sodium AMPS, which is doubly crosslinked with
methylene bis-acrylamide as a permanent crosslinker and PEG-200 or
PEG-400 diacrylate, as a labile or unstable crosslinkers. These
micro-particles are in a ball form and cannot be further
crosslinked since the functional groups are mostly hidden inside
these microparticles.
[0068] After the polymer reaches the target zone deep in the
reservoir, the unstable internal crosslinkers PEG-200 or PEG-400
diacrylates hydrolyze, and the particle then opens up (swells or
"pops"). Such popped particles behave as a typical polymer
exhibiting good viscosities, but they are not gels. The addition of
the tertiary PEI crosslinker, crosslinks the now accessible amide
groups and results in a stable gel in situ.
[0069] Slim tube tests were performed to determine the performance
of BrightWater.RTM. type polymers in porous media when crosslinked
in situ with the PEI tertiary crosslinker. Each tube was composed
of eight 5' long stainless steel tubing with internal diameter
(i.d.)=3/8''. The sections were filled with sand before connecting
each to a pressure tap and assembling them together and forming a
coil from them for ease of handling. The coil was then placed in an
oven set to a desired temperature. Flow rates and differential
pressure measurements were monitored by a LabVIEW data acquisition
system throughout the experiment.
[0070] Each test required three Isco 500D syringe pumps. One pump
was used to maintain a back pressure of 100 psi on the slim tube.
The second pump was used for water injection, and the third pump
was used for polymer injection. These pumps were programmed to
inject or withdraw at a given flow rate while monitoring the
pressure.
[0071] The test was initiated by water injection at constant flow
rates to determine permeability in each section of the slim tube.
About 1-2 pore volume (PV) polymer solution was then injected into
the slim tube at constant flow rate followed by a small amount of
water injection to clear the inlet lines from polymer.
Simultaneously 6 ampoules containing the polymer solution were
placed in the same oven to monitor the progress of popping
process.
[0072] Popping time is a strong function of aging temperature--that
is the higher the temperature, the shorter the popping time. In
order to determine the optimum aging condition, we accelerated
aging of the polymer at 190.degree. F. to shorten the popping time.
After varying aging times at 190.degree. F. or 150.degree. F., the
resistance factor was determined by injecting a small amount of
water. At the same time the content of one ampoule was used to
determine the viscosity and extent of polymer popping.
[0073] The brine composition used in the experiments is given in
Table A.
TABLE-US-00001 TABLE 1 Brine A Composition Bicarbonate Ppm 1621
Chloride Ppm 15330 Sulfate Ppm 250 Calcium Ppm 121 Potassium Ppm
86.9 Magnesium Ppm 169 Sodium Ppm 11040 Strontium Ppm 7.57
[0074] FIG. 3 shows the viscosity versus aging time for 0.5%
BrightWater.RTM. EC 9408A microparticles with and without 1000 ppm
PEI aged at 190.degree. F. in brine A. As this graphic shows, the
solution of polymer alone reached a maximum viscosity of about 67
centi Poise (cP) within 11 days of aging with no appreciable change
with additional aging at 190.degree. F. However, the same
microparticles solution containing 1000 ppm PEI (identified as
"gelant") began to gel within a few days of aging at 190.degree.
F.
[0075] A similar experiment performed with this system aged at
150.degree. F. resulted in gel formation at longer aging times.
FIG. 4 shows a plot of viscosity versus aging time at 150.degree.
F. for a solution of 0.5% BrightWater.RTM. EC 9408A microparticles
achieving a maximum viscosity of about 57 cP in 51 days of aging. A
similar solution containing 0.5% BrightWater.RTM. EC 9408A and 1000
ppm PEI (identified as "gelant") began to gel in about 28 days of
aging at 150.degree. F.
[0076] FIG. 5 shows composite plots of FIGS. 3 and 4 indicating gel
formation when the polymer contains PEI and aged at 150.degree. F.
or 190.degree. F. The difference is the longer tertiary gelation
time at the lower temperature. Gelation time can also be increased
with the addition of a carbonate retarder.
[0077] Earlier experiments performed in a slim tube treated with
BrightWater.RTM. microparticles and phenol/formaldehyde
crosslinking systems also produced strong gels. The resulting gel
effectively prohibited water flow in such tube even at pressures as
high as 1000 psi. Such gels essentially consolidated the sand,
which could not be pushed out of the tube unless it was cut in
small segments (2-3'') and exposed to very high pressures
(.about.1000 psi). Our experiments herein with the PEI tertiary
crosslinker also produced very strong gels, but differed in that
PEI is less toxic to the environment. Further, PEI being a single
component avoids any risk of separation, whereas
phenol/formaldehyde might separate due to chromatographic
separation.
[0078] A final experiment is shown in FIG. 6, which compares
viscosity versus aging time for an anionic polymeric microparticle
that is a swellable copolymer of acrylamide and sodium acrylate
crosslinked with poly(ethylene glycol) diacrylate and methylene
bisacrylamide and including 1000 ppm PEI (MW 2000). The polymeric
particles were aged in synthetic Brine A. As illustrated in FIG. 6,
temperature affects gelation rate, increasing temperature
increasing gelation rate.
[0079] In summary, addition of polyethyleneimine to
BrightWater.RTM. or anionic polymeric microparticles result in
gelation of the popped polymer, when exposed to stimulants such as
heat or pH changes. This process is expected to improve the
longevity of BrightWater.RTM. or other swellable microparticle
treatments. While gelation of PHPAM or other acrylamide based
polymers with polyethyleneimine is well known, gelation of
swellable microparticles with PEI is a novel process with the
distinct advantage of low injection viscosity and in situ formation
of gels which increase the longevity of BrightWater.RTM. and
similar treatments.
[0080] These experiments proved that the longevity of
BrightWater.RTM. and similar polymer treatments could be
significantly enhanced by addition of an external tertiary
crosslinking system to the injection package. In these treatments,
PEI tertiary crosslinking system produced gels with the popped
polymer exhibiting very large RF values. The resulting gels are not
mobile and cannot be washed out of the slim tube. Such gels
actually behaved as binding agents consolidating the sand.
Furthermore, the compositions described herein have many uses in
other industries.
[0081] Each of the following references is incorporated herein in
their entirety for all purposes. [0082] U.S. Pat. No. 4,773,481
[0083] U.S. Pat. No. 6,454,003, U.S. Pat. No. 6,729,402, U.S. Pat.
No. 6,984,705 [0084] US2010234252 Crosslinked Swellable Polymer
[0085] US2010314115 Swellable polymer with cationic sites [0086]
US2010292109 Swellable polymers with hydrophobic groups [0087]
US2010314114 Swellable polymer with anionic sites [0088] SPE139308
Laboratory Development and Successful Field Application of a
Conformance Polymer System for Low-, Medium- and High-Temperature
Applications. [0089] SPE97530 Investigation of--A High Temperature
Organic Water-Shutoff Gel: Reaction Mechanisms
* * * * *