Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
SILOXANE SURFACTANT ADDITIVES FOR OIL AND GAS APPLICATIONS
FIELD OF THE INVENTION
The present invention generally relates to the production of petroleum and
more
particularly to compositions and processes for improving the recovery of
petroleum from a
subterranean geological formation.
BACKGROUND OF THE INVENTION
For many years, petroleum has been recovered from subterranean reservoirs
through the
use of drilled wells and production equipment. During the production of
desirable hydrocarbons,
such as crude oil and natural gas, a number of other naturally occurring
substances may also be
encountered within the subterranean environment.
The removal of unwanted deposits from the wellbore and production equipment is
generally referred to as "remediation." In contrast, the term "stimulation"
generally refers to the
treatment of geological formations to improve the recovery of hydrocarbons.
Common
stimulation techniques include well fracturing and acidizing operations. Well
remediation and
stimulation are important services that are offered through a variety of
techniques by a large
number of companies.
Oil and natural gas are found in, and produced from, porous and permeable
subterranean
formations. The porosity and permeability of the formation determine its
ability to store
hydrocarbons, and the facility with which the hydrocarbons can be extracted
from the formation.
The use of certain microemulsion additives during completion of both oil and
gas wells
leads to higher near wellbore permeability and long-term increased production
of hydrocarbons
from the well. The increased displacement of water from the formation and
proppant by both oil
and gas (flowback) and consequent increased production of hydrocarbons have
been attributed to
lowered capillary pressure. However, the solvent -hydrocarbon surfactant
systems that have been
used have limitations in their ability to lower capillary pressure. There is,
therefore, a need for
treatment compositions that are capable of lowering capillary pressure and
increasing wettability
while maintaining the desirable properties of conventional emulsified
treatment formulations.
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SUMMARY OF THE INVENTION
In some embodiments, a well treatment additive is provided comprising a foam,
wherein
the foam comprises an emulsion or microemulsion comprising a siloxane
surfactant, a solvent,
and an aqueous phase, and wherein the solvent is a terpene hydrocarbon.
In some embodiments, a method of treating a wellbore of an oil/and or gas is
provided
comprising injecting an additive into the wellbore, wherein the additive
comprises an emulsion
or microemulsion, wherein the emulsion or microemulsion comprises an siloxane
surfactant, a
solvent, and an aqueous phase, wherein the solvent comprises a terpene, and
forming a foam
from the emulsion or microemulsion prior to and/or during the injection of the
additive into the
wellbore.
In some embodiments, the present invention includes a well treatment additive
that
includes a siloxane surfactant, a solvent and an aqueous phase. The solvent is
preferably a
terpene hydrocarbon. The well treatment additive preferably is a spontaneously
formed nanofluid
with a nano-sized self-assembled liquid phase.
In some embodiment, siloxane surfactants (alone or in combination with
conventional
hydrocarbon surfactants) are used to form and enhance the properties of
terpene solvent based
nanofluid additives useful for the treatment of oil and gas wells.
In another aspect, methods of using the novel well treatment additives in a
variety of well
treatment processes are provided. Suitable well treatment processes include,
but are not limited
to, acidizing operations, hydraulic fracturing operations, well remediation
operations and water
removal operations.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 provides a graph of the surface tension of 2 gpt dispersions of
siloxane surfactant
containing microemulsion formulations. The squares represent formulations
containing a higher
level of terpene solvent while the circles represent formulations with a lower
level of terpene
solvent.
FIG. 2 provides a graph of the aqueous phase displacement by gas for a
siloxane
surfactant additive during an upflow experiment using 20/40 mesh Ottawa sand.
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FIG. 3 provides a graph of aqueous phase displacement by Eagle Ford condensate
for two
siloxane surfactant microemulsion products compared with two existing
commercial
microemulsion products in a downflow experiment using 70/140 Ottawa Sand.
Figure 4 provides a graph of particle size distribution for a 2 gpt dispersion
of
Formulation A in 2% KCI brine. The formulation disperses to a narrow single
distribution of
very small nanodroplets.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Presently preferred embodiments generally contemplate the preparation of an
additive for
use in oil and gas wells. The additive preferably includes a solvent
component, a surfactant
component and an aqueous phase. In some embodiments, nano-sized particles of
the solvent
component are distributed within the aqueous phase. In certain embodiments,
the additive
comprises an emulsion or microemulsion. In some embodiments, the additive
forms a stable
foam. Other functional materials may also be included advantageously.
Generally, the additive is prepared using a siloxane surfactant, a solvent and
an aqueous
phase. In some embodiments, the solvent is a terpene and the surfactant
includes a combination
of a siloxane surfactant and a hydrocarbon surfactant of a kind, amount and
proportion effective
to form a stable distribution of the nanosized particles of terpene solvent
within the aqueous
phase. In certain embodiments, the solvent is a terpene and the surfactant
includes a combination
of a siloxane surfactant and an alcohol. Each of these components is discussed
separately below.
In some embodiments, additives comprising an emulsion or microemulsion are
provided.
The terms should be understood to include emulsions or microemulsions that
have a water
continuous phase, or that have an oil continuous phase, or microemulsions that
are bicontinuous
or multiple continuous phases of water and oil. In certain embodiments, the
additive comprising
an emulsion or microemulsion forms a stable foam.
As used herein, the term emulsion is given its ordinary meaning in the art and
refers to
dispersions of one immiscible liquid in another, in the form of droplets, with
diameters
approximately in the range of 100-1,000 nanometers. Emulsions may be
thermodynamically
unstable and/or require high shear forces to induce their formation.
As used herein, the term microemulsion is given its ordinary meaning in the
art and refers
to dispersions of one immiscible liquid in another, in the form of droplets,
with diameters
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approximately in the range of about between about 1 and about 1000 nm, or
between 10 and
about 1000 nanometers, or between about 10 and about 500 nm, or between about
10 and about
300 nm, or between about 10 and about 100 nm. Microemulsions are clear or
transparent because
they contain particles smaller than the wavelength of visible light. In
addition, microemulsions
are homogeneous thermodynamically stable single phases, and form
spontaneously, and thus,
differ markedly from thermodynamically unstable emulsions, which generally
depend upon
intense mixing energy for their formation. Microemulsions may be characterized
by a variety of
advantageous properties including, by not limited to, (i) clarity, (ii) very
small particle size, (iii)
ultra-low interfacial tensions, (iv) the ability to combine properties of
water and oil in a single
homogeneous fluid, (v) shelf life stability, and (vi) ease of preparation.
In some embodiments, the microemulsions described herein are stabilized
microemulsions that are formed by the combination of a solvent-surfactant
blend with an
appropriate oil-based or water-based carrier fluid. Generally, the
microemulsion forms upon
simple mixing of the components without the need for high shearing generally
required in the
formation of ordinary emulsions. In some embodiments, the microemulsion is a
thermodynamically stable system, and the droplets remain finely dispersed over
time. In some
cases, the average droplet size ranges from about 10 nm to about 300 nm.
It should be understood, that while much of the description herein focuses on
microemulsions, this is by no means limiting, and emulsions may be employed
where
appropriate.
In some embodiments, the emulsion or microemulsion is a single emulsion or
microemulsion. For example, the emulsion or microemulsion comprises a single
layer of a
surfactant. In other embodiments, the emulsion or microemulsion may be a
double or
multilamellar emulsion or microemulsion. For example, the emulsion or
microemulsion
comprises two or more layers of a surfactant. In some embodiments, the
emulsion or
microemulsion comprises a single layer of surfactant surrounding a core (e.g.,
one or more of
water, oil, solvent, and/or other additives) or a multiple layers of
surfactant (e.g., two or more
concentric layers surrounding the core). In certain embodiments, the emulsion
or microemulsion
comprises two or more immiscible cores (e.g., one or more of water, oil,
solvent, and/or other
.. additives which have equal or about equal affinities for the surfactant).
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In some embodiments, a microemulsion comprises water, a solvent, and a
surfactant. In
some embodiments, the microemulsion further comprises additional components,
for example, a
freezing point depression agent or an alcohol. Details of each of the
components of the
microemulsions are described in detail herein. In some embodiments, the
components of the
microemulsions are selected so as to reduce or eliminate the hazards of the
microemulsion to the
environment and/or the subterranean reservoirs.
In some embodiments, the emulsion or microemulsion comprise between about 3
wt%
and about 50 wt% solvent (e.g., a terpene), between about 10 wt% and about 70
wt% surfactant
(e.g., a siloxane surfactant), and between about 5 wt% and about 45 wt% a co-
solvent. In certain
embodiments, the solvent is present in the emulsion or microemulsion in an
amount between
about 5 wt% and about 35 wt%, or between about 7 wt% and about 27 wt%. In some
embodiments, the surfactant is present in the emulsion or microemulsion in an
amount between
about 15 wt% and about 60 wt%, or between about 20 wt% and about 50 wt%. In
certain
embodiments, the co-solvent is present in the emulsion or microemulsion in an
amount between
about 5 wt% and about 35 wt%, or between about 5 wt% and about 20 wt%. In some
embodiments, the co-solvent is an alcohol. In some embodiments, the co-solvent
is selected
from the group consisting of methanol, ethanol, isopropyl alcohol, ethylene
glycol, propylene
glycol, dipropylene glycol monomethyl ether, triethylene glycol, ethylene
glycol monobutyl
ether, and combinations thereof.
In some embodiments, the emulsion or microemulsion is as described in U.S.
Patent No.
7,380,606, entitled "Composition and Process for Well Cleaning", or in U.S.
Patent Application
Serial No. 14/212,763, filed March 14, 2014, and entitled "Methods and
Compositions for use in
Oil and/or Gas Wells".
As used herein, the term "siloxane surfactant" refers to permethylated
siloxane materials
functionalized with a sufficient number of polar groups so as to render them
usefully surface
active in aqueous mixtures. Thus, these siloxane surfactants qualify as
amphiphiles in which a
hydrophobic silicone group is coupled with one or more hydrophilic groups.
They may be, in
some cases, co-polymers, or molecules comparable in molecular weight to
conventional organic
surfactants such as heptaethylene glycol monododecyl ether.
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To facilitate description of preferred siloxane surfactants, it is helpful to
use the MDTQ
notation for siloxane copolymers adopted in United States Patent No. 3,299,112
issued January
17, 1967 to Bailey, and summarized in Table 1 below:
Table 1- MDTQ Notation for Siloxane Building Block Units
Me3Si010¨ A trimethyl end-cap unit
¨Me2Si0¨ The basic dimethyl unit
¨MeSiO3/2¨ A three-way branch point unit
Q. ¨S102¨ A four-way branch point unit
M' Me2(R)5101/2¨ A substituted trifunctional end-
cap unit
ID' ¨Me(R)Si0¨ A substituted difunctional unit
T' ¨RS1030¨ A substituted three-way branch
point unit
Me ¨CH3
H, or (after hydrosilylation) some non-
methyl
organic group such as
¨CH2CH2CH2(OCH2CH2)n0H
It should be noted that while an organic radical, R, is implicit in the M'D'T
notation, the
R group is shown in the structures given below to permit a more detailed
disclosure of the range
of non-limiting structures of R groups useful within the siloxane surfactant
component.
In some embodiments, the siloxane surfactant component is an organosilicon
compound
having a formula selected from the group consisting of one of the formulas
identified in Table 2
below:
1. MDa(D'Rl)bM a graft-type copolymer
2. (M'RI)Da(M'RI) an ABA-type copolymer
3. (IVIRI)Da(M'R1) an AB-type copolymer
4. a hybrid graft-type, ABA-type copolymer
(MRI)Da(D'R1)b(M'R1)
5. Tz(T'Rl)c a silsesquioxane cage structure
6. (M'Rl)tMuQv a functionalized MQ silicone resin
7. [(D'Rl)Dk] a cyclic siloxane (the square brackets denote a cyclic
structure)
where R1 represents an organic radical comprising -(CH2)n-(OCH2CH2)x-
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(OCH(CH3)CH2)y-OR3, in which n=3 to about 11, x=3 to about 30, y=1 to about
30, and R3 may be -H, -Me, or -C(0)CH3.
For formula 1, a is 0-200, and b is 1-20. The case for which a=0 and b=1
represents the
heptamethyltrisiloxane surfactants. Suitable examples are available from Dow
Corning
Corporation as Dow Corning Q2-5211 Superwetting Agent, or from Momentive TM
as Silwet
L-77. For formula 2, a is 4-50. A suitable example available from Dow Corning
Corporation is
Dow Corning 2-8692 Fluid. For formula 3, a is 0-25, and R2 represents an
alkane radical of 1-
8 carbon atoms. For formula 4, a is 0-200, and b is 1-20. For formula 5, the
ratio of c:z is 1:7 to
2:6, and the total molecular weight should be less than 7000 Daltons. For
formula 6, the ratio of
(t+u):v is from 0.4:1 to 2:1 and the ratio of t:u is from 1:4 to 1:1, and the
total molecular weight
should be less than 7000 Daltons. For formula 7, k is 4-5.
In some embodiments, the surfactant comprises an alkoxylated siloxane
surfactant. In
some embodiments, the siloxane comprises a plurality of ethylene oxide and/or
propylene oxide
groups. For example, in some embodiments, the surfactant is an AB-type
copolymer comprising
the structure as in formula 8:
(CH3)3SiO(Si(CH3)20),,Si(CH3)2CH2CH2CH2(OCH2CH2)x(OCH(CH3)CH2)y0R3 (8)
(e.g., MDnM'R1 in the MDTQ notation) wherein R3 is H, -CH3, or -C(0)CH3, m is
1-4, x is 4-12,
and y is 0-2.
In certain embodiments, the surfactant is an ABA-type copolymer comprising the
structure as in formula 9:
R3(ocii2cH2)õ(ocri(cx,)cH2)ycx,cH2cH,(cH3)2sio(si(cx,)2o)nsi(cH3)2cH2cui,ci-
ifocH2cH2.),c(ocx(cHocti2)yoR3
(9)
(e.g., R11\4'DnM'R1 in the MDTQ notation) wherein each R3 is independently H, -
CH3, or -
C(0)CH3, n is 2-4, each x is independently 4-12, and each y is independently 0-
2.
In some embodiments, the surfactant is a functionalized cyclosiloxane
comprising the
structure as in formula 10:
(0Si(CH3)2),OSi(CH3)2CH2CH2CH2(OCH2CH2)x(OCH(CH3)CH2)yOR3
(10)
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(e.g., DaD'Ri in the MDTQ notation) wherein R3 is H, -CH3, or ¨C(0)CH3, z is 3
(e.g., a cyclic
tetramer) or 4 (e.g., a cyclic pentamer), x is 4-12, and y is 0-2.
Other non-limiting cyclic siloxanes will be known in the art, for examples,
those
described in U.S. Patent No. 3,299,112, entitled "Siloxane Wetting Agents",
filed June 19, 1964,
and U.S. Patent No. 3,562,786, entitled "Organosilicon-surfactant
compositions," filed
November 9, 1966.
In certain embodiments, the siloxane surfactant is an alkoxylated trisiloxane
surfactant.
In some embodiments, the siloxane surfactant of formula 8, 9, or 10 has a
molecular weight of
between about 350 Daltons and about 2000 Daltons. In certain embodiments, the
siloxane
surfactant of formula 8, 9, or 10 has a molecular weight of less than or equal
to about 2000
Daltons, less than or equal to about 1500 Daltons, less than or equal to about
1000 Daltons, less
than or equal to about 500 Daltons, or less than or equal to about 400
Daltons. In some
embodiments, the siloxane surfactant of formula 8, 9, or 10 has a molecular
weight of greater
than about 350 Daltons, greater than about 500 Daltons, greater than about
1000 Daltons, or
greater than about 1500 Daltons. Combinations of the above-referenced ranges
are also possible
(e.g., between about 350 Daltons and about 2000 Daltons, between about 500
Daltons and about
2000 Daltons, or between about 700 Daltons and about 2000 Daltons). Other
molecular weights
are also possible.
Suitable hydrocarbon surfactants include a multiplicity of surface active
agents which are
expediently classified into nonionic, anionic, cationic and amphoteric surface-
active agents. An
overview is cited in Ullmanns Encyklopadie der technischen Chemie [Ullmanns
Encyclopedia of
Industrial Chemistry], Verlag Chemie Weinheim, 4th Edition 1975, Volume 10,
pp. 449-473.
In some embodiments, the additive comprises one or more surfactants (e.g., in
addition
to the siloxane surfactant; e.g., a first surfactant and a second surfactant).
Non-limiting examples
of suitable surfactants include nonionic surfactants, cationic surfactants,
anionic surfactants,
zwitterionic surfactants, or combinations thereof. Surfactants in general are
wetting agents that
lower the surface tension of a liquid in which they are dissolved, allowing
easier spreading and
decreasing the interfacial tension between two liquids. Each surfactant has a
hydrophilic head
that is attracted to water molecules and a hydrophobic tail that repels water
and attaches itself to
hydrophobic materials such as oil and grease.
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In certain embodiments, the additive comprises a non-ionic surfactant. In this
context, a
nonionic surfactant has an uncharged hydrophilic head and a hydrophobic tail
comprising a
carbon chain. Examples of nonionic surfactants suitable for use in this
disclosure include without
limitation linear alcohol ethoxylates, polyoxyethylene alkylphenol
ethoxylates, polyoxyethylene
alcohol ethoxylates, polyoxyethylene esters of fatty acids, polyoxyethylene
alkylamines, alkyl
polyglucosides, ethylene oxide-propylene oxide copolymers or a combination
thereof In some
cases, nonionic surfactants may have a carbon chain length of 8-20 carbon
atoms and 3-40
ethylene oxide units, up to 40 propylene oxide units, up to 2 glucose units or
a combination
thereof.
In some embodiments, the nonionic surfactant may be present in the additive in
an
amount of from about 5 wt. % to about 70 wt. % based on the total weight of
the additive, or
from about 10 wt. %to about 70 wt. %, or from about 20 wt.% to about 40 wt. %.
In certain embodiments, the additive comprises an anionic surfactant. In this
context, an
anionic surfactant has a negatively charged head and a hydrophobic tail
comprising a carbon
chain. Examples of anionic surfactants suitable for use in this disclosure
include without
limitation sodium salts of fatty acids, alkyl sulphates, alkyl ethoxylate
sulphates or sulfonates, or
a combination thereof In some cases, anionic surfactants may have a carbon
chain length of 8-20
carbon atoms.
In some embodiments, the additive comprises a cationic surfactant. In this
context, a
cationic surfactant has a positively charged head and a hydrophobic tail
comprising a carbon
chain. Examples of cationic surfactants suitable for use in this disclosure
include without
limitation quaternary ammonium salts, ethoxylated quaternary ammonium salts,
or a
combination thereof. In some cases, the cationic surfactant may have a carbon
chain length of 8-
20 carbon atoms.
In certain embodiments, the additive comprises a zwitterionic surfactant.
Zwitterionic
surfactants are electrically neutral surfactants that carry both a formal
positive and a formal
negative charge on different atoms in the same molecule. Examples of
zwitterionic surfactants
suitable for use in this disclosure include without limitation alkyl amine
oxides, alkyl betaines,
alkyl amidopropyl betaine, alkyl sulfobetaines, alkyl sultaines, or
combinations thereof In some
cases, the zwitterionic surfactant may have a carbon chain length of 8-20
carbon atoms.
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Surfactants can be described in terms of their hydrophile-lipophile balance
(HLB)
numbers, or silicone HLB (SHLB) numbers for siloxane surfactants, but the
formulation of a
microemulsion generally requires that the surfactant system be matched to, and
optimized for the
particular oil or solvent in use. It has been determined that the best
procedure for selecting and
optimizing a surfactant system, in some embodiments, is to map the phase
behavior and select
the system that gives the desired stability over a wide range of temperatures.
Other non-limiting surfactants will be known in the art, for examples, those
described in
U.S. Patent No. 7,380,606, entitled "Composition and Process for Well
Cleaning", and in U.S.
Patent Application Serial No. 14/212,763, filed March 14, 2014, and entitled
"Methods and
Compositions for use in Oil and/or Gas Wells".
In some embodiments, the solvent component may be selected from the class of
solvents
referred to as terpenes, including those derived from citrus and from pine
sources. Terpene
solvents are natural products, whose structures are built up from isoprene
units. In some
embodiments, at least one of the solvents present in the microemulsion is a
terpene or a
terpenoid. In some embodiments, the terpene or terpenoid comprises a first
type of terpene or
terpenoid and a second type of terpene or terpenoid. A dimer consisting of two
isoprene units is
termed a monoterpene. They can be acyclic or cyclic. The broader term
"terpenoids" also covers
natural and synthetic derivatives such as alcohols, aldehydes, ketones, and
ethers. In certain
embodiments, terpenes include cyclic and acyclic monoterpenoids, including but
not limited to
those that are good solvents for paraffins and asphaltenes.
Terpenes may be generally classified as monoterpenes (e.g., having two
isoprene units),
sesquiterpenes (e.g., having 3 isoprene units), diterpenes, or the like. The
term terpenoid also
includes natural degradation products, such as ionones, and natural and
synthetic derivatives,
e.g., terpene alcohols, aldehydes, ketones, acids, esters, epoxides, and
hydrogenation products
(e.g., see Ullmann's Encyclopedia of Industrial Chemistry, 2012, pages 29-45).
It should be
understood, that while much of the description herein focuses on terpenes,
this is by no means
limiting, and terpenoids may be employed where appropriate. In some cases, the
terpene is a
naturally occurring terpene. In some cases, the terpene is a non-naturally
occurring terpene
and/or a chemically modified terpene (e.g., saturated terpene, terpene amine,
fluorinated terpene,
or silylated terpene).
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In some embodiments, the terpene is a monoterpene. Monoterpenes may be further
classified as acyclic, monocyclic, and bicyclic, as well as whether the
monoterpene comprises
one or more oxygen atoms (e.g., alcohol groups, ester groups, carbonyl groups,
etc.). In some
embodiments, the terpene is an oxygenated terpene, for example, a terpene
comprising an
alcohol, an aldehyde, and/or a ketone group. In some embodiments, the terpene
comprises an
alcohol group. Non-limiting examples of terpenes comprising an alcohol group
are linalool,
geraniol, nopol, a-terpineol, and menthol. In some embodiments, the terpene
comprises an ether-
oxygen, for example, eucalyptol, or a carbonyl oxygen, for example, menthone.
In some
embodiments, the terpene does not comprise an oxygen atom, for example, d-
limonene.
Non-limiting examples of terpenes include linalool, geraniol, nopol, a-
terpineol, menthol,
eucalyptol, menthone, d-limonene, terpinolene,13-occimene, y-terpinene, a-
pinene, and
citronellene. In a particular embodiment, the terpene is selected from the
group consisting of a-
terpineol, a-pinene, nopol, and eucalyptol. In one embodiment, the terpene is
nopol. In another
embodiment, the terpene is eucalyptol. In some embodiments, the terpene is not
limonene (e.g.,
d-limonene). In some embodiments, the emulsion is free of limonene.
In some embodiments, the terpene is a non-naturally occurring terpene and/or a
chemically modified terpene (e.g., saturated terpene). In some cases, the
terpene is a partially or
fully saturated terpene (e.g., p-menthane, pinane). In some cases, the terpene
is a non-naturally
occurring terpene. Non-limiting examples of non-naturally occurring terpenes
include, menthene,
p-cymene, r-carvone, terpinenes (e.g., alpha-terpinenes, beta-terpinenes,
gamma-terpinenes),
dipentenes, terpinolenes, borneol, alpha-terpinamine, and pine oils.
Those of ordinary skill in the art will be aware of solvents other than
terpenes to use with
the additives described herein. Other non-limiting solvents will be known in
the art, for
examples, those described in U.S. Patent No. 7,380,606, entitled "Composition
and Process for
Well Cleaning", and in U.S. Patent Application Serial No. 14/212,763, filed
March 14, 2014, and
entitled "Methods and Compositions for use in Oil and/or Gas Wells".
The emulsion or microemulsion may comprise a co-solvent or a mixture of co-
solvents.
Co-solvents may, in some cases, increase the usefulness of emulsion or
microemulsion,
especially freeze stability. Non-limiting examples of co-solvents include
short chain alkyl
alcohols and glycols and combinations thereof. In some embodiments, the co-
solvents comprise
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methanol, ethanol, isopropanol, 1,2-pentanediol, propylene glycol, and
triethylene glycol and/or
combinations thereof.
In some embodiments, the co-solvent may be present in the additive in an
amount of from
about 5 wt.% to about 70 wt. %based on the total weight of the additive, more
preferably from
.. about 10 wt. % to about 70 wt. %, and even more preferably from about 20
wt. %to about 40 wt.
%. Alternatively, the co-solvents are incorporated into the additive to
provide a formulation that
is clear and stable over a temperature range from -25 degrees F to 150 degrees
F.
Generally, the microemulsion comprises an aqueous phase. Generally, the
aqueous phase
comprises water. The water may be provided from any suitable source (e.g., sea
water, fresh
.. water, deionized water, reverse osmosis water, water from field
production). The water may be
present in any suitable amount. In some embodiments, the total amount of water
present in the
microemulsion is between about 1 wt% about 95 wt%, or between about 1 wt%
about 90 wt%, or
between about 1 wt% and about 60 wt%, or between about 5 wt% and about 60 wt%
or between
about 10 and about 55 wt%, or between about 15 and about 45 wt%, versus the
total
microemulsion composition.
The water to solvent ratio in a microemulsion may be varied. In some
embodiments, the
ratio of water to solvent, along with other parameters of the solvent may be
varied. In some
embodiments, the ratio of water to solvent by weight is between about 15:1 and
1:10, or between
9:1 and 1:4, or between 3.2:1 and 1:4.
Any suitable method for injecting the additive (e.g., emulsion or
microemulsion) into a
wellbore may be employed. For example, in some embodiments, the additive may
be injected
into a subterranean formation by injecting it into a well or wellbore in the
zone of interest of the
formation and thereafter pressurizing it into the formation for the selected
distance. Methods for
achieving the placement of a selected quantity of a mixture in a subterranean
formation are
known in the art. The well may be treated with the microemulsion for a
suitable period of time.
The microemulsion and/or other fluids may be removed from the well using known
techniques,
including producing the well.
It should be understood, that in embodiments where an additive is said to be
injected into
a wellbore, that the additive may be diluted and/or combined with other liquid
component(s)
prior to and/or during injection (e.g., via straight tubing, via coiled
tubing, etc.). For example, in
some embodiments, the additive is diluted with an aqueous carrier fluid (e.g.,
water, brine, sea
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water, fresh water, or a well-treatment fluid (e.g., an acid, a fracturing
fluid comprising
polymers, produced water, sand, slickwater, etc.,)) prior to and/or during
injection into the
wellbore. In some embodiments, a composition for injecting into a wellbore is
provided
comprising an additive as described herein and an aqueous carrier fluid,
wherein the
microemulsion is present in an amount between about 0.1 and about 50 gallons
per thousand
gallons (gpt) per dilution fluid, or between 0.1 and about 100 gpt, or between
about 0.5 and
about 10 gpt, or between about 0.5 and about 2 gpt.
In some embodiments, the additive is utilized as a form. In some embodiments,
the
additive comprises an emulsion or microemulsion in the form of a foam. In some
embodiments,
the emulsions or microemulsions described herein are used to generate the
foam.
Generally, oil recovered from oil bearing earth formations is usually first
produced by the
inherent formation pressure of the oil bearing earth formations. In some
cases, however, the oil
bearing formation lacks sufficient inherent pressure to force the oil from the
formation upward to
the surface. In other cases, the inherent pressure of an oil-bearing formation
can be expended
prior to the recovery of all of the recoverable oil so that when the pressure
of the production zone
has been reduced by continued withdrawal, where the well may stop flowing. In
such cases,
artificial methods of lifting the oil from the formation to the surface are
usually employed. For
example, foam may be used, in some embodiments, to increase the viscosity of
the gas phase of a
gas flooding operation or an immiscible gas flooding operation which provides
lift and enhances
production of liquid hydrocarbon from the well. Foam may also be used, in some
cases, to divert
flow from a highly swept (or high permeability zone) to a less swept (or lower
permeability)
zone thus increasing the efficacy of pushing the crude oil towards a
production well. Foam may
also be used, in some cases, to energize fracturing operations and carry
proppant during a
fracturing operation.
However, maintaining foam in an oil formation is difficult because crude oil
is a known
defoamer and may inhibit, diminish, or completely eliminate the foam generated
by most
hydrocarbon surfactants. In addition, siloxane materials (e.g., siloxane
surfactants) are typically
used as defoamers. The inventors unexpectedly discovered that a certain class
of alkoxylated
siloxane surfactants, as described above, are capable of stabilizing a foam in
the presence of
crude oil.
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=
In some embodiments, the foam comprises an emulsion or microemulsion as
described
herein. For example, in certain embodiments, the foam comprises water, a
solvent (e.g., a
terpene), and a surfactant (e.g., an alkoxylated siloxane surfactant). In some
embodiments, the
foam further comprises additional components, for example, a freezing point
depression agent or
a co-solvent (e.g., an alcohol).
In some embodiments, an emulsion or a microemulsion described herein (e.g.,
comprising an alkoxylated siloxane surfactant) forms a foam upon contact with
gas (e.g., carbon
dioxide, flu gas, methane, natural gas, or nitrogen) and is injected into a
formation (e.g., in an
aqueous treatment fluid or injected into the gas stream). In certain
embodiments, the emulsion or
microemulsion described herein (e.g., comprising an alkoxylated siloxane
surfactant) forms a
foam upon contact with gas (e.g., carbon dioxide or nitrogen) and is injected
into the formation
to divert gas flow from high permeability zones to low permeability zones
during a gas flood
enhanced oil recovery (IOR or EOR) treatments. In some embodiments, an
emulsion and/or
microemulsion is injected into the formation as a preflush to prepare the
formation for the foam
injection. The injection of the foam comprising an alkoxylated siloxane
surfactant may have
many advantages as compared to the injection of a foam not comprising an
alkoxylated siloxane
surfactant, including enhancing the stability of the foam (e.g., by preventing
the breakdown of
the foam by crude oil), and/or increasing the penetration of the foam into the
formation (e.g., by
increasing the volume of the foam formed).
Methods for using and generating foam will be generally known in the art. For
example,
a fluid comprising an additive (e.g., an emulsion or microemulsion) may
further comprise at least
one gas (e.g., nitrogen gas, carbon dioxide). In some embodiments, a foam may
be formed by
combining an additive (e.g., an emulsion or microemulsion) with a gas (e.g.,
nitrogen gas, carbon
dioxide). In some embodiments, the foam is generated prior to injection of the
material into a
wellbore. In certain embodiments, as described above, the foam is generated
from an emulsion
or microemulsion during and/or after injection into a wellbore.
A series of laboratory tests confirms the superior effectiveness of the
additives
incorporating siloxane surfactants. It has been determined that mixtures of
siloxane surfactants
and hydrocarbon surfactants, in some embodiments, can markedly lower surface
tension to
values not achievable by the hydrocarbon surfactants alone. In addition, and
unexpectedly since
silicone materials are usually regarded as incompatible with hydrocarbon
materials, the additives
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of in some embodiments have been found to exhibit improved aqueous phase
(brine)
displacement by crude oil or gas.
Within these laboratory tests, a first series of additives was prepared using
a siloxane
surfactant, a co-solvent, aqueous phase and a terpene solvent. A second series
of additives was
prepared using a siloxane surfactant, a hydrocarbon surfactant, a co-solvent,
an aqueous phase
and a terpene solvent. The following examples provide performance
characteristics for the first
and second series of additives.
Example 1: A transparent low-viscosity mixture that exhibited the
characteristic
properties of a microemulsion was prepared using 60% by weight of a 1:1 blend
of Dow Corning
Xiametere OFX-0190 Fluid (siloxane surfactant) and isopropyl alcohol (co-
solvent), 30% by
weight of water (aqueous phase), and 10% by weight of technical grade d-
limonene (terpene
solvent). This mixture was identified as a microemulsion based on the
spontaneous formation
with minimal mechanical energy input to form a transparent dispersion from an
immiscible
mixture of water and d-limonene upon addition of an appropriate amount of
surfactant and co-
solvent. These and other salient characteristics identifying a mixture as a
spontaneously formed
microemulsion are well known to practitioners in the art.
The order of mixing of this and other compositions described in this
disclosure is not
critical, but for convenience during the laboratory tests, the additives were
prepared using a
procedure in which a mixture of the surfactant and the isopropyl alcohol was
first prepared and
then combined with a mixture of the technical grade d-limonene and water. With
small samples
in the laboratory, a few seconds of gentle mixing yielded a transparent
dispersion. It will be
understood by experts on liquid mixing that longer times are required in the
large vessels used in
full-scale commercial manufacturing.
Example 2: A transparent low-viscosity additive was prepared using 30% by
weight of a
1:1 blend of Dow Corning 5211 Superwetting Agent (siloxane surfactant) an
isopropyl alcohol
(co-solvent), 60% by weight of water (aqueous phase), and 10% by weight of
technical grade d-
limonene (terpene solvent).
Example 3: A transparent low-viscosity additive was prepared using about 61%
by
weight of a blend of a detergent range alcohol ethoxylate surfactant, an
ethoxylated castor oil
surfactant, isopropyl alcohol and glycol co-solvent, about 2% by weight of
MomentiveTM Silwet
L-77 siloxane surfactant, 15% by weight of water, and 22% by weight of
technical grade d-
CA 2904736 2018-06-27
limonene. This is the formulation referenced as Formulation 3B below.
Additional transparent
low-viscosity additives were prepared increasing the siloxane surfactant up to
12% by weight of
Momentive TM Silwet L-77 (and 51% by weight of the other surfactant/co-solvent
components).
This is the formulation designated as 4B below.
Example 4: A transparent low-viscosity additive was prepared using about 41%
by
weight of a blend of a detergent range alcohol ethoxylate surfactant, an
ethoxylated castor oil
surfactant, isopropyl alcohol and glycol co-solvent, about 12% by weight of
MomentiveTM
Silwet L-77 siloxane surfactant, 41% by weight of water, and 6% by weight of
technical grade d-
limonene. Several additional formulations similar to this were prepared with
varying amounts of
siloxane surfactant. These are the microemulsion formulations shown in Figure
1 with a lower
level of terpene solvent.
To characterize the interfacial and performance characteristics of these
additives, 2
gallons per thousand (gpt) dilutions were prepared. The surface tension of the
2 gpt dilution was
measured using a properly calibrated Kruss K100 tensiometer. The surface
tension results for the
formulations described under Example 3 are shown in Figure 1. As Figure 1
demonstrates,
incorporation of the siloxane surfactant into these microemulsion formulations
produced a
progressive decrease in the surface tension, ultimately reaching values below
22 mN/m - much
lower than common hydrocarbon surfactants, which typically give surface
tension values greater
than 28 mN/m.
Contact angles of 2 gpt dilutions were measured on dry-polished shale core
samples from
the Niobrara formation. For commercially available microemulsion products,
initial contact
angle values for 2 gpt dilutions are around 30-40 degrees with rapid
relaxation to stable values of
9-15 degrees within 30 seconds. For the formulations shown in Figure 1, all
except the 0%
siloxane surfactant gave contact angles of zero degrees (hence complete
wetting) after 6-20
seconds. This demonstrates the remarkable ability of the microemulsion
incorporating this
siloxane surfactant to produce complete wetting of mixed-wet formation rock
surfaces even for
small proportions of the siloxane surfactant in the formulation. Decreasing
the contact angle
from 9 degrees to zero degrees increases the capillary pressure slightly, but
even a small decrease
in the surface tension from 29 to 28 mN/m more than offsets this slight
increase (assuming a 10
micron pore diameter, capillary pressure Pc=0.831 psi for a surface tension of
29 mN/m and
contact angle of 9 degrees, and Pc=0.812 psi for 28 mN/m and zero degrees).
Thus the
16
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combination of surface tension lowering and increased wetting would be
expected to lead to an
increase in near wellbore conductivity.
Figure 2 shows the efficacy of one of the low terpene solvent formulations
from Figure 1
in promoting brine displacement by gas. A 2 gpt dispersion of this formulation
gave a surface
tension of 25.8 mN/m.
Surface tensions of the 2 gpt dispersions were measured before and after they
passed
through the sand pack to determine how much of the surfactant was lost to
adsorption during the
experiment. An increase of surface tension of 1-3 mN/m was typically observed.
In the case of
the formulation shown in Figure 2 the increase was < 1 mN/m. In comparison, a
surfactant
package widely used in the oilfield exhibited an increase in surface tension
of > 20 mN/m, often
up to 40 mN/m (representing essentially complete loss of all surfactant due to
adsorption).
Figure 3 shows the progression in performance enhancement from an all-
hydrocarbon
microemulsion formulation with increasing level of siloxane surfactant.
Formulation 3B gave a
surface tension of 28 mN/m, while 4B gave a surface tension value of 24.5
mN/m. Both siloxane
surfactant formulations perform better than the commercial products. Thus,
combining the
siloxane surfactant with the hydrocarbon surfactant and the terpene solvent
yields a
microemulsion formulation with much improved performance.
Example 5: An additive was prepared using a combination of Dow Corning
Xiameter
OFX-0190 Fluid (siloxane surfactant) with a detergent grade alcohol ethoxylate
surfactant and d-
limonene as the solvent, and its performance compared with that of the
hydrocarbon surfactant.
The ratio of the siloxane surfactant to the detergent grade alcohol ethoxylate
(hydrocarbon)
surfactant is 1:4 (by weight). Figure 4 shows the particle size distribution
of a 2 gpt dispersion of
Formulation A into 2% KCI brine. The additive disperses to a narrow single
distribution of very
small nanodroplets, easily small enough to be compatible with the pore size of
even low
permeability tight shale gas formations. This formulation gave 87% aqueous
phase displacement
by condensate, and 73% aqueous phase displacement by gas (upflow).
Example 6: A further demonstration of the efficacy of a microemulsion prepared
by
combining a higher HLB highly efficient siloxane surfactant with a hydrocarbon
surfactant and a
terpene solvent. The siloxane surfactant had an HLB value of 13.2 and was
combined with a
detergent grade alcohol ethoxylate surfactant and d-limonene as the terpene
solvent. Formulation
1 was prepared with a 1:1 ratio of water to terpene solvent, while Formulation
2 was prepared
17
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with a 6.5:1 ratio of water to terpene solvent. In both formulations, the
surfactant mixture and
concentration were identical. The surface tensions of both formulations before
passing through
the sand pack were about 21 mN/m. After contacting the sand pack the surface
tensions
increased 2-4 mN/m for the first pore volume, and negligible increase for the
third pore volume.
Both formulations reached excellent Eagle Ford condensate displacement values
of about 90% -
slightly better than the siloxane surfactant formulations shown in Figure 3,
and much better than
the commercial microemulsion products shown in Figure 3. These formulations
achieved gas
displacement values of 69-76% (see Figure 2 for experimental details).
Example 7: Laboratory tests were conducted to characterize the effectiveness
of various
microemulsions and their ability to produce foam. The microemulsions used in
these tests were
prepared using several surfactants with different foamabilities. Two
microemulsions were made
with an alkoxylate trisiloxane surfactant mixed with isopropyl alcohol at a
1:1 ratio. The first, a
high surfactant microemulsion, contained 90 parts by weight of the surfactant
isopropyl alcohol
mix, 5 parts by weight of terpene, and 5 parts by weight of water. The second,
a low surfactant
microemulsion, contained 60 parts by weight of the surfactant isopropyl
alcohol mix, 20 parts by
weight of terpene, and 20 parts by weight of water. A second surfactant
comprised of linear C12-
C15 alcohol ethoxylates with an average of 7 moles of ethylene oxide was mixed
with isopropyl
alcohol at a 1:1 ratio and used to make a standard microemulsion. The standard
microemulsion
contained 46 parts by weight of the surfactant isopropyl alcohol mix, 27 parts
by weight of
terpenes, and 27 parts by weight of water. The last surfactant used was an
alkyl polyglucoside
surfactant. The alkyl polyglucoside microemulsion was made using similar
ratios as the low
surfactant microemulsion described above. The microemulsions described above
were used as
treatments in foam tests.
To begin the foam testing procedure, 2 gallons per thousand of each treatment
was
diluted into 200 grams of solution (2% KC1 with or without condensate). This
solution
containing treatment was put into a 1 liter jar on a WARING blender. The
WARING blender
was connected to a rheostat which was set to 70% of the maximum output
voltage. The treated
solution was mixed in the WARING blender for 30 seconds on the low setting.
Once mixed the
solution was poured into a 1 liter graduated cylinder. The volume of the
initial height of the foam
was recorded in milliliters. The amount of time needed for the foam to break
to 100 milliliters of
liquid was also recorded. The examples in Tables 3, 4, and 5 show the
percentage of foam
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increase for each microemulsion tested. This percentage was established by the
difference in the
volume of the solution before and after mixing:
Percent foam increase was determined by the following equation:
% Foam Increase = Foam Height after Blending ¨ Initial Liquid Volume
x 100
Initial Liquid Volume
Table 3. Foam test results for 2 gpt of treatment in 2% KC1.
Formulation Surfactant % Foam Increase
High Surfactant
Microemulsion Alkoxylated Trisiloxane A 150
Low Surfactant
Microemulsion Alkoxylated Trisiloxane A 105
Standard C12 ¨ C15 Linear Alcohol
Microemulsion Ethoxylate 75
Low Surfactant Cio ¨ C16 Alkyl
Microemulsion Polyglucoside 35
Table 4. Foam test results for 2 gpt of treatment in 2% KC1 with 0.5%
condensate.
Formulation Surfactant % Foam Increase
High Surfactant
Microemulsion Alkoxylated Trisiloxane A 85
Standard C12 ¨ C15 Linear Alcohol
Microemulsion Ethoxylate 20
Table 5. Foam test results for 2 gpt of treatment in 2% KC1 with 1.0%
condensate.
Formulation Surfactant % Foam Increase
High Surfactant
Microemulsion Alkoxylated Trisiloxane A 55
Low Surfactant
Microemulsion Alkoxylated Trisiloxane A 55
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Low Surfactant C to ¨ C16 Alkyl
Microemulsion Polyglucoside 10
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 as defined in the written description and appended
claims.
CA 2904736 2018-06-27
