Note: Descriptions are shown in the official language in which they were submitted.
METHODS AND COMPOSITIONS FOR STIMULATING THE
PRODUCTION OF HYDROCARBONS FROM SUBTERRANEAN
FORMATIONS
Related Applications
This application is a division of Canadian Patent Application No. 2,906,047
filed March 13, 2014, which claims priority to U.S. Patent Application No.
13/829,495 filed March 14, 2013, entitled "Methods and Compositions for
Stimulating the Production of Hydrocarbons from Subterranean Formations,"
(published as US 2014/0262261A1) and to U.S. Patent Application No. 13/829,434
filed March 14, 2013 entitled "Methods and Compositions for Stimulating the
Production of Hydrocarbons from Subterranean Foimations" (published as US
2014/0274817A1).
Field of Invention
The present invention generally provides methods and compositions for
stimulating the production of hydrocarbons (e.g., formation crude oil and/or
formation
gas) from subterranean formations.
Background of 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 term "stimulation" generally refers to the treatment of geological
formations to
improve the recovery of liquid hydrocarbons (e.g., formation crude oil and/or
formation gas). Common stimulation techniques include well fracturing and
acidizing
operations.
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. Hydraulic fracturing is commonly used to
stimulate low
permeability geological formations to improve the recovery of hydrocarbons.
The
process can involve suspending chemical agents in a well-treatment fluid
(e.g.,
fracturing fluid) and injecting the fluid down the wellbore. However, the
assortment
of chemicals pumped down the well can cause damage to the surrounding
formation
by entering the reservoir rock and blocking the pore throats. It is known that
fluid
invasion can have a
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CA 3059006 2019-10-17
detrimental effect on gas permeability and can impair well productivity. In
addition,
fluids may become trapped in the formation due to capillary end effects in and
around
the vicinity of the formation fractures.
In efforts to reduce phase trapping, additives have been incorporated into
well-
treatment fluids. Generally, the composition of additives comprises multi-
component
chemical substances and compositions that contain mutually distributed
nanodomains of
normally immiscible solvents, such as water and hydrocarbon-based organic
solvents,
stabilized by surfactants (e.g., microemulsions). The incorporation of
additives into well-
treatment fluids can increase crude oil or formation gas, for example by
reducing
capillary pressure and/or minimizing capillary end effects.
Although a number of additives are known in the art, there is a continued need
for more effective additives for increasing crude oil or formation gas for
wellbore
remediation, drilling operations, and formation stimulation.
Summary of Invention
Methods and compositions for stimulating the production of hydrocarbons (e.g.,
formation crude oil and/or formation gas) from subterranean formations are
provided.
In some embodiments, methods of selecting a composition for treating an oil or
gas well having a wellbore are provided comprising determining whether
displacement
of residual aqueous treatment fluid by formation crude oil or displacement of
residual
aqueous treatment fluid by formation gas is preferentially stimulated for the
oil or gas
well having a wellbore; and selecting an emulsion or a microemulsion for
injection into
the wellbore to increase formation crude oil or formation gas production by
the well,
wherein the emulsion or the microemulsion comprises water, a terpene, and a
surfactant,
the ratio of water to terpene by weight is between about 3:1 and about 1:2;
wherein the
terpene has a phase inversion temperature greater than 43 C when displacement
of
residual aqueous treatment fluid by formation crude oil is preferentially
stimulated, or
wherein the terpene has a phase inversion temperature less than 43 C when
displacement of residual aqueous treatment fluid by formation gas is
preferentially
stimulated. In some embodiments, the method further comprises injecting the
emulsion
or the microemulsion into the wellbore to increase production of formation
crude oil or
formation gas by the well.
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CA 3059006 2019-10-17
In some embodiments, methods of treating an oil or gas well having a wellbore
are provided comprising injecting an emulsion or a microemulsion into the
wellbore of
the oil or gas well to stimulate displacement of residual aqueous treatment
fluid by
formation crude oil and increase production of formation crude oil by the
well, wherein
the emulsion or the microemulsion comprises water, a terpene, and a
surfactant; wherein
the ratio of water to terpene by weight is between about 3:1 and about 1:2;
and wherein
the terpene has a phase inversion temperature greater than 43 C.
In some embodiments, methods of treating an oil or gas well having a wellbore
are provided comprising injecting an emulsion or a microemulsion into the
wellbore of
the oil or gas well to stimulate displacement of residual aqueous treatment
fluid by
formation gas and increase production of formation gas by the well, wherein
the
emulsion or the microemulsion comprises water, a terpene, and a surfactant;
wherein the
ratio of water to terpene by weight is between about 3:1 and about 1:2; and
wherein the
terpene has a phase inversion temperature less than 43 C.
In some embodiments, methods of treating an oil or gas well having a wellbore
are provided comprising using an emulsion or a microemulsion to stimulate
displacement
of residual aqueous treatment fluid by formation crude oil or displacement of
residual
aqueous treatment fluid by formation gas by injecting the emulsion or the
microemulsion
into the wellbore of the oil or gas well, and increase production of formation
crude oil or
formation gas by the well, wherein the emulsion or the microemulsion comprises
water,
a terpene, and a surfactant; wherein the ratio of water to terpene by weight
is between
about 10:1 and about 3:1; and wherein the terpene has a phase inversion
temperature of
greater than 43 C.
In some embodiments, methods of treating an oil or gas well having a wellbore
are provided comprising using an emulsion or a microemulsion to stimulate
displacement
of residual aqueous treatment fluid by oil or displacement of residual aqueous
treatment
fluid by gas by injecting the emulsion or the microemulsion into the wellbore
of the oil
or gas well, and increase production of formation crude oil or formation gas
by the well,
wherein the emulsion or the microemulsion comprises water, a terpene, and a
surfactant;
wherein the ratio of water to terpene by weight is between about 10:1 and
about 3:1; and
wherein the terpene has a phase inversion temperature of less than 43 C.
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CA 3059006 2019-10-17 - -
In some embodiments, an emulsion or a microemulsion for stimulating an oil or
gas
well is provided comprising an aqueous phase; a surfactant; a freezing point
depression
agent; and a terpene, wherein the terpene is nopol.
In some embodiments, an emulsion or a microemulsion for stimulating an oil or
gas
well is provided comprising an aqueous phase; a surfactant; a freezing point
depression
agent; and a terpene, wherein the terpene is eucalyptol.
Other aspects, embodiments, and features of the invention will become apparent
from
the following detailed description when considered in conjunction with the
accompanying
drawings.
Brief Description of the Drawings
The accompanying drawings are not intended to be drawn to scale. In the
drawings,
each identical or nearly identical component that is illustrated in various
figures is
represented by a like numeral. For purposes of clarity, not every component
may be labeled
in every drawing. In the drawings:
Figure 1 shows an exemplary plot for determining the phase inversion
temperature of
a microemulsion, according to some embodiments.
Detailed Description
The present invention generally relates to methods and well-treatment
compositions
(e.g., emulsions or microemulsions) for stimulating of the production of
liquid hydrocarbons
(e.g., formation crude oil and/or formation gas) from subterranean formations.
In some
embodiments, the compositions comprise an emulsion or a microemulsion, as
described in
more detail herein. The emulsions or the microemulsions may include water, a
terpene, a
surfactant, and optionally a freezing point depression agent or other
components. In some
embodiments, the methods relate to stimulating displacement of residual
aqueous treatment
fluid by formation crude oil or formation gas to increase production of liquid
hydrocarbons,
as described in more detail below. In some embodiments, methods of selecting
an emulsion
or a microemulsion comprising a terpene are provided, wherein the emulsion or
the
microemulsion is selected so as to increase liquid hydrocarbon production.
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Date Recue/Date Received 2020-06-17
As described herein, in some embodiments, the inventors have found that
microemulsions or emulsions comprising certain terpenes increase the
displacement
(e.g., flowback) of residual aqueous treatment fluid by liquid hydrocarbons
(e.g., crude
oil) as compared to other terpenes. In other embodiments, emulsions or
microemulsions
comprising certain terpenes increase the displacement of residual aqueous
treatment fluid
by gaseous hydrocarbons as compared to other terpenes. Laboratory tests may be
conducted, as described herein, to determine the displacement of residual
aqueous
treatment fluid by liquid hydrocarbons and/or gaseous hydrocarbons of an
emulsion or a
microemulsion
Petroleum is generally recovered from subterranean reservoirs through the use
of
drilled wells and production equipment. Wells are "stimulated" using various
treatments
(e.g., fracturing, acidizing) of geological formations to improve the recovery
of liquid
hydrocarbons. Oil and natural gas are found in, and produced from, porous and
permeable subterranean formations. Based on techniques known in the art, as
well as the
.. preference for the desired product isolated (e.g., formation crude oil or
formation gas), it
may be preferential to stimulate either crude oil production or gas production
from each
well. A well drilled into a subterranean formation may penetrate formations
containing
liquid or gaseous hydrocarbons or both, as well as connate water or brine. The
gas-to-oil
ratio is termed the GOR. The operator of the well may choose to complete the
well in
such a way as to produce (for example) predominantly liquid hydrocarbons
(crude oil).
Alternatively, the operator may be fracturing a tight gas shale formation
containing
predominantly gaseous hydrocarbons.
Incorporation of the emulsions or the microemulsions described herein (e.g.,
comprising water, a terpene, and a surfactant) into well-treatment fluids
(e.g., fracturing
fluids) can aid in reducing fluid trapping, for example, by reducing capillary
pressure
and/or minimizing capillary end effects. In additional, incorporation of the
emulsions or
the microemulsions described herein into well-treatment fluids can promote
increased
flow back of aqueous phases following well treatment, and thus, increase
production of
liquid and/or gaseous hydrocarbons. That is, incorporation of an emulsion or a
.. microemulsion described herein can aid in the displacement of residual
aqueous
treatment fluid by formation crude oil and/or formation gas. Residual aqueous
treatment
fluids may include those fluids employed for fracturing, as well as residual
aqueous
fluids originally present in the well.
CA 3059006 2019-10-17 - 5 -
In some embodiments, methods of treating an oil or gas well are provided. In
some embodiments, the methods comprise injecting an emulsion or a
microemulsion into
the wellbore of the oil or gas well to stimulate displacement of residual
aqueous
treatment fluid by formation crude oil or formation gas, and increase
production of liquid
hydrocarbons by the well.
In some embodiments, methods are provided for selecting a composition for
treating an oil or gas well. The inventors have discovered that certain
terpenes are more
effective at stimulating displacement of residual aqueous treatment fluid by
formation
crude oil or displacement of residual aqueous treatment fluid by formation gas
for the oil
or gas well and that the selection of the terpene may be influenced by the
ratio of water
to terpene in the emulsion or the microemulsion.
In some embodiments, if displacement of residual aqueous treatment fluid by
formation crude oil is preferentially stimulated and the emulsion or the
microemulsion
comprises water to terpene at a ratio between about 3:1 and about 1:2, then
the terpene
may be selected to have a phase inversion temperature greater than 43 C, as
determined
by the method described herein. Alternatively, if displacement of residual
aqueous
treatment fluid by formation gas is preferentially stimulated and the emulsion
or the
microemulsion comprises water to terpene at a ratio between about 3:1 and
about 1:2,
then the terpene may be selected to have a phase inversion temperature less
than 43 C,
as determined by the method described herein In some embodiments, the ratio of
water
to terpene by weight is between about 3:1 and about 1:1.5, or between about
2:1 and
about 1:1.5.
In some embodiments, to stimulate displacement of residual aqueous treatment
fluid by formation crude oil, the ratio of water to terpene by weight in the
emulsion or
the microemulsion may be between about 3:1 and about 1:2, or between about 2:1
and
about 1:1.5, and the terpene may be selected to have a phase inversion
temperature
greater than 43 C, as determined by the method described herein. In some
embodiments,
to stimulate displacement of residual aqueous treatment fluid by formation
crude oil or
formation gas and increase production of formation gas the well, the ratio of
water to
terpene by weight in the emulsion or the microemulsion may be between about
3:1 and
about 1:2, or between about 2:1 and about 1:1.5, and the terpene may be
selected to have
a phase inversion temperature less than 43 C, as determined by the method
described
herein.
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In some embodiments, to stimulate displacement of residual aqueous treatment
fluid by formation crude oil, wherein the ratio of water to terpene by weight
in the
emulsion or the microemulsion is between about 10:1 and about 3:1, the terpene
may be
selected to have a phase inversion temperature greater than 43 C, as
determined by the
method described herein. In some embodiments, to stimulate displacement of
residual
aqueous treatment fluid by formation gas and increase production of formation
gas by
the well, wherein the ratio of water to terpene by weight in the emulsion or
the
microemulsion is between about 10:1 and about 3:1, the terpene may be selected
to have
a phase inversion temperature less than 43 C, as determined by the method
described
herein. In some embodiments, the ratio of water to terpene by weight is
between about
6:1 and about 5:1.
It should understood, that in embodiments where a microemulsion is said to be
injected into a wellbore, that the microemulsion may be diluted and/or
combined with
other liquid component(s) prior to and/or during injection. For example, in
some
embodiments, the microemulsion is diluted with an aqueous carrier fluid (e.g.,
water,
brine, sea water, fresh water, or a treatment fluid such as a fracturing fluid
comprising
polymers, sand, etc.) prior to and/or during injection into the wellbore. In
some
embodiments, a composition for injecting into a wellbore is provided
comprising a
microemulsion 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 of dilution fluid ("gpt"), or between about 0.5 and about 10
gpt, or
between about 0.5 and about 2 gpt. Generally, dilution of a microemulsion does
not
result in the breakdown of the microemulsion.
In some embodiments, emulsions 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.
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,
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CA 3059006 2019-10-17
with diameters approximately in the range 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
- 8 -
CA 3059006 2019-10-17
of water, oil, solvent, and/or other additives which have equal or about equal
affinities
for the surfactant).
In some embodiments, a microemulsion comprises water, a terpene, and a
surfactant. In some embodiments, the microemulsion may further comprise
additional
components, for example, a freezing point depression agent. 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 microemulsion comprises a terpene or a terpenoid.
The microemulsion may comprise a single terpene or terpenoid or a combination
of two
or more terpenes and/or terpenoids. For example, in some embodiments, the
terpene or
terpenoid comprises a first type of terpene or terpenoid and a second type of
terpene or
terpenoid. 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).
In some embodiments, the terpene is a monoterpene. Monoterpenes may be
further classified as acyclic, monocyclic, and bicyclic (e.g., with a total
number of
carbons in the range between 18 and 20), 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
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CA 3059006 2019-10-17
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, P-occimene, y-
terpinene,
a-pinene, and citronellene. In a particular embodiment, the terpene is
selected from the
group consisting of a-terpeneol, 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
to 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 terpenc (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, mcnthene, p-cymene, r-carvone, terpinenes (e.g., alpha-
terpinenes,
beta-terpinenes, gamma-terpinenes), dipentenes, terpinolenes, borneol, alpha-
terpinamine, and pine oils.
In some embodiments, the terpene is classified in terms of its phase inversion
temperature (PIT). The term phase inversion temperature is given its ordinary
meaning in
the art and refers to the temperature at which an oil in water microemulsion
inverts to a
water in oil microemulsion (or vice versa). Those of ordinary skill in the art
will be
aware of methods for determining the PIT for a microemulsion comprising a
terpene
(e.g., see Strey, Colloid & Polymer Science, 1994. 272(8): p. 1005-1019;
Kahlweit et al.,
Angewandte Chemie International Edition in English, 1985. 24(8): p. 654-668).
The PIT
values described herein were determined using a 1:1 ratio of terpene (e.g.,
one or more
terpenes):de-ionized water and varying amounts (e.g., between about 20 wt% and
about
60 wt%; generally, between 3 and 9 different amounts are employed) of a 1:1
blend of
surfactant comprising linear C12-C15 alcohol ethoxylates with on average 7
moles of
ethylene oxide (e.g., Neodol 25-7):isopropyl alcohol wherein the upper and
lower
temperature boundaries of the microemulsion region can be determined and a
phase
diagram may be generated. Those of ordinary skill in the art will recognize
that such a
phase diagram (e.g., a plot of temperature against surfactant concentration at
a constant
oil-to-water ratio) may be referred to as fish diagram or a Kahlweit plot. The
temperature
at the vertex is the PIT. An exemplary fish diagram indicating the PIT is
shown in Figure
-10-
CA 3059006 2019-10-17
1. PITs for non-limiting examples of terpenes determined using this
experimental
procedure outlined above are given in Table 1.
Table 1: Phase inversion temperatures for non-limiting examples of terpenes.
Terpene Phase Inversion Temperature C ( F)
linalool -4 (24.8)
geraniol -0.5 (31.1)
nopol 2.5 (36.5)
a-terpineol 4.6 (40.3)
menthol 16 (60.8)
eucalyptol 31 (87.8)
menthone 32 (89.6)
d-limonene 43 (109.4)
terpinolene 48 (118.4)
13-occimene 49 (120.2)
y-terpinene 49 (120.2)
a-pinene 57 (134.6)
citronellene 58 (136.4)
In some embodiments, as described in more detail herein, the terpene has a PIT
greater than and/or less than 43 C, as determined by the method described
herein. In
some embodiments, the terpene has a PIT greater than 43 C, as determined by
the
method described herein. In some embodiments, the terpene has a PIT less than
43 C, as
determined by the method described herein. In some embodiments, the terpene
has a PIT
greater than 32 C, as determined by the method described herein. In some
embodiments,
the terpene has a PIT less than 32 C, as determined by the method described
herein. In
some embodiments, the PIT is between about -10 'V and about 70 C, or between
about
-4 C and about 60 C, as determined by the method described herein. In some
embodiments, the minimum PIT is -10 C, or -4 C, as determined by the method
described herein. In some embodiments, the maximum PIT is 70 C, or 60 C, as
determined by the method described herein.
In certain embodiments, the solvent utilized in the emulsion or microemulsion
herein may comprise one or more impurities. For example, in some embodiments,
a
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CA 3059006 2019-10-17
solvent (e.g., a terpene) is extracted from a natural source (e.g., citrus),
and may
comprise one or more impurities present from the extraction process. In some
embodiment, the solvent comprises a crude cut (e.g., uncut crude oil, for
example, made
by settling, separation, heating, etc.). In some embodiments, the solvent is a
crude oil
(e.g., naturally occurring crude oil, uncut crude oil, crude oil extracted
from the wellbore,
synthetic crude oil, etc.). In some embodiments, the solvent is a citrus
extract (e.g., crude
orange oil, orange oil, etc.).
The terpene may be present in the microemulsion in any suitable amount. In
some embodiments, terpene is present in an amount between about In some
embodiments, terpene is present in an amount between about 2 wt% and about 60
wt%,
or between about 5 wt% and about 40 wt%, or between about 5 wt% and about 30
wt%,
versus the total microemulsion composition. In some embodiments, the terpene
is present
in an amount between about 1 wt% and about 99 wt%, or between about 2 wt% and
about 90 wt %, or between about 1 wt% and about 60 wt%, or between about 2 wt%
and
about 60 wt%, or between about 1 wt% and about 50 wt%, or between about 1 wt%
and
about 30 wt%, or between about 5 wt% and about 40 wt%, or between about 5 wt%
and
about 30 wt%, or between about 2 wt% and about 25 wt%, or between about 5 wt%
and
about 25 wt%, or between about 60 wt% and about 95 wt%, or between about 70
wt% or
about 95 wt%, or between about 75 wt% and about 90 wt%, or between about 80
wt%
and about 95 wt%, versus the total microemulsion composition.
The water to terpene ratio in a microemulsion may be varied, as described
herein.
In some embodiments, the ratio of water to terpene, along with other
parameters of the
terpene (e.g., phase inversion temperature of the terpene) may be varied so
that
displacement of residual aqueous treatment fluid by formation gas and/or
formation
crude is preferentially stimulated. In some embodiments, the ratio of water to
terpene by
weight is between about 3:1 and about 1:2, or between about 2:1 and about
1:1.5. In
other embodiments, the ratio of water to terpene is between about 10:1 and
about 3:1, or
between about 6:1 and about 5:1.
Generally, the microemulsion comprises an aqueous phase comprising 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
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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.
In some embodiments, at the emulsion or microemulsion may comprise mutual
solvent which is miscible together with the water and the terpene. In some
embodiments,
the mutual solvent is present in an amount between about at 0.5 wt% to about
30% of
mutual solvent. Non-limiting examples of suitable mutual solvents include
ethyleneglycolmonobutyl ether (EGMBE), dipropylene glycol monomethyl ether,
short
chain alcohols (e.g., isopropanol), tetrahydrofuran, dioxane,
dimethylformamide, and
dimethylsulfoxide.
In some embodiments, the microemulsion comprises a surfactant. The
microemulsion may comprise a single surfactant or a combination of two or more
surfactants. For example, in some embodiments, the surfactant comprises a
first type of
surfactant and a second type of surfactant. The term "surfactant," as used
herein, is given
.. its ordinary meaning in the art and refers to compounds having an
amphiphilic structure
which gives them a specific affinity for oil/water-type and water/oil-type
interfaces
which helps the compounds to reduce the free energy of these interfaces and to
stabilize
the dispersed phase of a microemulsion. The term surfactant encompasses
cationic
surfactants, anionic surfactants, amphoteric surfactants, nonionic
surfactants, zwitterionic
.. surfactants, and mixtures thereof. In some embodiments, the surfactant is a
nonionic
surfactant. Nonionic surfactants generally do not contain any charges.
Amphoteric
surfactants generally have both positive and negative charges, however, the
net charge of
the surfactant can be positive, negative, or neutral, depending on the pH of
the solution.
Anionic surfactants generally possess a net negative charge. Cationic
surfactants
generally possess a net positive charge. Awitterionic surfactants are
generally no pH
dependent. not pH dependent. A zwitterion is a neutral molecule with a
positive and a
negative electrical charge, though multiple positive and negative charges can
be present.
Zwitterions are distinct from dipole, at different locations within that
molecule.
In some embodiments, the surfactant is an amphiphilic block copolymer where
.. one block is hydrophobic and one block is hydrophilic. In some cases, the
total
molecular weight of the polymer is greater than 5000 daltons. The hydrophilic
block of
these polymers can be nonionic, anionic, cationic, amphoteric, or
zwitterionic.
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The term surface energy, as used herein, is given its ordinary meaning in the
art
and refers to the extent of disruption of intermolecular bonds that occur when
the surface
is created (e.g., the energy excess associated with the surface as compared to
the bulk).
Generally, surface energy is also referred to as surface tension (e.g., for
liquid-gas
interfaces) or interfacial tension (e.g., for liquid-liquid interfaces). As
will be understood
by those skilled in the art, surfactants generally orient themselves across
the interface to
minimize the extent of disruption of intermolecular bonds (i.e. lower the
surface energy).
Typically, a surfactant at an interface between polar and non-polar phases
orient
themselves at the interface such that the difference in polarity is minimized.
Those of ordinary skill in the art will be aware of methods and techniques for
selecting surfactants for use in the microemulsions described herein. In some
cases, the
surfactant(s) are matched to and/or optimized for the particular oil or
solvent in use. In
some embodiments, the surfactant(s) are selected by mapping the phase behavior
of the
microemulsion and choosing the surfactant(s) that gives the desired range of
stability. In
some cases, the stability of the microemulsion over a wide range of
temperatures is
targeted as the microemulsion may be subject to a wide range of temperatures
due to the
environmental conditions present at the subterranean formation and/or
reservoir.
Suitable surfactants for use with the compositions and methods described
herein
will be known in the art. In some embodiments, the surfactant is an alkyl
polyglycol
ether, for example, having 2-250 ethylene oxide (EO) (e.g., or 2-200, or 2-
150, or 2-100,
or 2-50, or 2-40) units and alkyl groups of 4-20 carbon atoms. In some
embodiments, the
surfactant is an alkylaryl polyglycol ether having 2-250 EO units (e.g., or 2-
200, or 2-
150, or 2-100, or 2-50, or 2-40) and 8-20 carbon atoms in the alkyl and aryl
groups. In
some embodiments, the surfactant is an ethylene oxide/propylene oxide (E0/P0)
block
copolymer having 2-250 E0 or PO units (e.g., or 2-200, or 2-150, or 2-100, or
2-50, or
2-40). In some embodiments, the surfactant is a fatty acid polyglycol ester
having 6-24
carbon atoms and 2-250 EO units (e.g., or 2-200, or 2-150, or 2-100, or 2-50,
or 2-40). In
some embodiments, the surfactant is a polyglycol ether of hydroxyl-containing
triglycerides (e.g., castor oil). In some embodiments, the surfactant is an
alkylpolyglycoside of the general formula where R" denotes a linear or
branched, saturated or unsaturated alkyl group having on average 8-24 carbon
atoms and
denotes an oligoglycoside group having on average n=1-10 hexose or pentose
units or
mixtures thereof. In some embodiments, the surfactant is a fatty ester of
glycerol,
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sorbitol, or pentaerythritol. In some embodiments, the surfactant is an amine
oxide (e.g.,
dodecyldimethylamine oxide). In some embodiments, the surfactant is an alkyl
sulfate,
for example having a chain length of 8-18 carbon atoms, alkyl ether sulfates
having
8-18 carbon atoms in the hydrophobic group and 1-40 ethylene oxide (EO) or
propylene
oxide (PO) units. In some embodiments, the surfactant is a sulfonate, for
example, an
alkyl sulfonate having 8-18 carbon atoms, an alkylaryl sulfonate having 8-18
carbon
atoms, an ester or half ester of sulthsuccinic acid with monohydric alcohols
or
alkylphenols having 4-15 carbon atoms, or a multisulfonate (e.g., comprising
two, three,
four, or more, sulfonate groups). In some cases, the alcohol or alkylphenol
can also be
ethoxylated with 1-250 EO units (e.g., or 2-200, or 2-150, or 2-100, or 2-50,
or 2-40). In
some embodiments, the surfactant is an alkali metal salt or ammonium salt of a
carboxylic acid or poly(alkylene glycol) ether carboxylic acid having 8-20
carbon atoms
in the alkyl, aryl, alkaryl or aralkyl group and 1-250 EO or PO units (e.g.,
or 2-200, or 2-
150, or 2-100, or 2-50, or 2-40). In some embodiments, the surfactant is a
partial
phosphoric ester or the corresponding alkali metal salt or ammonium salt,
e.g., an alkyl
and alkaryl phosphate having 8-20 carbon atoms in the organic group, an
alkylether
phosphate or alkarylether phosphate having 8-20 carbon atoms in the alkyl or
alkaryl
group and 1-250 EO units (e.g., or 2-200, or 2-150, or 2-100, or 2-50, or 2-
40). In some
embodiments, the surfactant is a salt of primary, secondary, or tertiary fatty
amine
having 8-24 carbon atoms with acetic acid, sulfuric acid, hydrochloric acid,
and
phosphoric acid. In some embodiments, the surfactant is a quaternary alkyl-
and
alkylbenzylammonium salt, whose alkyl groups have 1-24 carbon atoms (e.g., a
halide,
sulfate, phosphate, acetate, or hydroxide salt). In some embodiments, the
surfactant is an
alkylpyridinium, an alkylimidazolinium, or an alkyloxazolinium salt whose
alkyl chain
has up to 18 carbons atoms (e.g., a halide, sulfate, phosphate, acetate, or
hydroxide salt).
In some embodiments, the surfactant is amphoteric or zwitterionic, including
sultaines
(e.g., cocamidopropyl hydroxysultaine), betaines (e.g., cocamidopropyl
betaine), or
phosphates (e.g., lecithin). Non-limiting examples of specific surfactants
include a linear
C12-C15 ethoxylated alcohols with 5-12 moles of EO, lauryl alcohol ethoxylate
with 4-8
moles of EO, nonyl phenol ethoxylate with 5-9 moles of EO, octyl phenol
ethoxylate
with 5-9 moles of EO, tridecyl alcohol ethoxylate with 5-9 moles of EO,
Pluronic
matrix of EO/PO copolymers, ethoxylated cocoamide with 4-8 moles of EO,
ethoxylated
coco fatty acid with 7-11 moles of EO, and cocoamidopropyl amine oxide.
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In some embodiments, the surfactant is a siloxane surfactant as described in
U.S. Patent Application Serial No. 13/831,410, filed March 14, 2014.
In some embodiments, the surfactant is a Gemini surfactant. Gemini
surfactants generally have the structure of multiple amphiphilic molecules
linked
together by one or more covalent spacers. In some embodiments, the surfactant
is an
extended surfactant, wherein the extended surfactats has the structure where a
non-
ionic hydrophilic spacer (e.g. ethylene oxide or propylene oxide) connects an
ionic
hydrophilic group (e.g. carboxylate, sulfate, phosphate).
In some embodiments the surfactant is an alkoxylated polyimine with a
relative solubility number (RSN) in the range of 5-20. As will be known to
those of
ordinary skill in the art, RSN values are generally determined by titrating
water into a
solution of surfactant in 1,4dioxane. The RSN values is generally defined as
the
amount of distilled water necessary to be added to produce persistent
turbidity. In
some embodiments the surfactant is an alkoxylated novolac resin (also known as
a
phenolic resin) with a relative solubility number in the range of 5-20. In
some
embodiments the surfactant is a block copolymer surfactant with a total
molecular
weight greater than 5000 daltons. The block copolymer may have a hydrophobic
block that is comprised of a polymer chain that is linear, branched,
hyperbranched,
dendritic or cyclic. Non-limiting examples of monomeric repeat units in the
hydrophobic chains of block copolymer surfactants are isomers of acrylic,
methacrylic, styrenic, isoprene, butadiene, acrylamide, ethylene, propylene
and
norbomene. The block copolymer may have a hydrophilic block that is comprised
of a
polymer chain that is linear, branched, hyper branched, dendritic or cyclic.
Non-
limiting examples of monomeric repeat units in the hydrophilic chains of the
block
copolymer surfactants are isomers of acrylic acid, maleic acid, methacrylic
acid,
ethylene oxide, and acrylamine.
In some embodiments, the surfactant has a structure as in Formula I:
16
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R8
R7 R9
R1 f=-%
2(k)/ r0 R 0
R11
(0,
wherein each of R7, R8, R9, R'', and R" are the same or different and are
selected from
the group consisting of hydrogen, optionally substituted alkyl, and ¨CH=CHAr,
wherein
Ar is an aryl group, provided at least one of R7, R8, R9, RI", and RH is
¨CH=CHAr,
is hydrogen or alkyl, n is 1-100, and each m is independently 1 or 2. In some
embodiments, for a compound of Formula (I), V is hydrogen or C1-6 alkyl. In
some
embodiments, for a compound of Formula (I), R12 is H, methyl, or ethyl. In
some
embodiments, for a compound of Formula (I), V is H.
In some embodiments, the surfactant has a structure as in Formula II:
R8
R7 R9
e
X Y
0 R1
1 1
R
(II)
wherein each of R7, R8, R9, RI", and R" are the same or different and are
selected from
the group consisting of hydrogen, optionally substituted alkyl, and ¨CH=CHAr,
wherein
Ar is an aryl group, provided at least one of R7, Rs, R9, Ric), and K-11
is ¨CH=CHAr, r is
an anionic group, X"I. is a cationic group, n is 1-100, and each m is
independently 1 or 2.
In some embodiments, for a compound of Formula (II), X"'" is a metal cation or
N(R13)4,
wherein each V is independently selected from the group consisting of
hydrogen,
optionally substituted alkyl, or optionally substituted aryl. In some
embodiments, V" is
NH4. Non-limiting examples of metal cations are Nat, IC+, Mg42, and Ca12. In
some
embodiments, for a compound of Formula (II), r is -cr, -S020, or ¨0S020.
In some embodiments, the surfactant has a structure as in Formula III:
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R8
R7 R9
0 R10
R11
(III)
wherein each of R7, R8, R9, R1 , and R" are the same or different and are
selected from
the group consisting of hydrogen, optionally substituted alkyl, and -CH=CHAr,
wherein
Ar is an aryl group, provided at least one of R7, R8, R9, Ric), and R"
is -CH=CHAr, Z+ is
a cationic group, n is 1-100, and each m is independently 1 or 2. In some
embodiments,
for a compound of Formula (III), Z+ is N(R13)3, wherein each Rn is independent
selected
from the group consisting of hydrogen, optionally substituted alkyl, or
optionally
substituted aryl.
In some embodiments, for a compound of Formula (I), (II), or (III), two of R7,
R8,
R9, Rio, and tc. -11
are -CH=CHAr. In some embodiments, for a compound of Formula (I),
(II), or (III), one of R7, R8, R9, R1 , and R" is -CH=CHAr and each of the
other groups is
hydrogen. In some embodiments, for a compound of Formula (I), (II), or (III),
two of R7,
R8, R9, RI , and R" are -CH=CHAr and each of the other groups is hydrogen. In
some
embodiments, for a compound of Formula (I), (II), or (III), R7 and R8 are -
CH=CHAr
and R9, R1 , and R11 are each hydrogen. In some embodiments, for a compound of
Formula (I), (II), or (III), three of R7, R8, R9, Ru:), and K-11
are -CH=CHAr and each of
the other groups is hydrogen. In some embodiments, for a compound of Formula
(I), (II),
or (III), R7, R8, and R9 are -CH=CHAr and R1 and R11 are each hydrogen. In
embodiments, for a compound of Formula (I), (II), or (III), Ar is phenyl. In
some
embodiments, for a compound of Formula (I), (II), or (III), each m is 1. In
some
embodiments, for a compound of Formula (I), (II), or (III), each m is 2. In
some
embodiments, for a compound of Formula (I), (II), or (III), n is 6-100, or 1-
50, or 6-50,
or 6-25, or 1-25, or 5-50, or 5-25, or 5-20.
Those of ordinary skill in the art will be aware of methods and techniques for
selecting surfactant for use in the microemulsions described herein. In some
cases, the
surfactant(s) are matched to and/or optimized for the particular oil or
solvent in use. In
some embodiments, the surfactant(s) are selected by mapping the phase behavior
of the
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microemulsion and choosing the surfactant(s) that gives the desired range of
stability. In
some cases, the stability of the microemulsion over a wide range of
temperatures is
targeting as the microemulsion may be subject to a wide range of temperatures
due to the
environmental conditions present at the subterranean formation.
In some embodiments, the emulsion or microemulsion may comprise one or more
additives in addition to water, solvent (e.g., one or more types of solvents),
and
surfactant (e.g., one or more types of surfactants). In some embodiments, the
additive is
an alcohol, a freezing point depression agent, an acid, a salt, a proppant, a
scale inhibitor,
a friction reducer, a biocide, a corrosion inhibitor, a buffer, a viscosifier,
a clay swelling
inhibitor, an oxygen scavenger, and/or a clay stabilizer.
The surfactant may be present in the microemulsion in any suitable amount. In
some embodiments, the surfactant is present in an amount between about 10 wt%
and
about 70 wt%, or between about 15 wt% and about 55 wt% versus the total
microemulsion composition, or between about 20 wt% and about 50 wt%, versus
the
.. total microemulsion composition. In some embodiments, the surfactant is
present in an
amount between about 0 wt% and about 99 wt%, or between about 10 wt% and about
70 wt%, or between about 0 wt% and about 60 wt%, or between about 1 wt% and
about
60 wt%, or between about 5 wt% and about 60 wt%, or between about 10 wt% and
about
60 wt%, or between 5 wt% and about 65 wt%, or between 5 wt% and about 55 wt%,
or
between about 0 wt% and about 40 wt%, or between about 15 wt% and about 55
wt%, or
between about 20 wt% and about 50 wt%, versus the total microemulsion
composition.
In some embodiments, the microemulsion comprises an alcohol. The alcohol may
serve as a coupling agent between the solvent and the surfactant and aid in
the
stabilization of the microemulsion. The alcohol may also lower the freezing
point of the
microemulsion The microemulsion may comprise a single alcohol or a combination
of
two or more alcohols. In some embodiments, the alcohol is selected from
primary,
secondary and tertiary alcohols having between 1 and 20 carbon atoms. In some
embodiments, the alcohol comprises a first type of alcohol and a second type
of alcohol.
Non-limiting examples of alcohols include methanol, ethanol, isopropanol, n-
propanol,
n-butanol, i-butanol, sec-butanol, iso-butanol, and t-butanol. In some
embodiments, the
alcohol is ethanol or isopropanol. In some embodiments, the alcohol is
isopropanol.
The alcohol may be present in the emulsion in any suitable amount. In some
embodiments, the alcohol is present in an amount between about 0 wt% and about
50
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wt%, or between about 0.1 wt% and about 50 wt%, or between about 1 wt% and
about
50 wt%, or between about 5 wt% and about 40 wt%, or between about 5 wt% and 35
wt%, versus the total microemulsion composition.
In some embodiments, the microemulsion comprises a freezing point depression
agent. The microemulsion may comprise a single freezing point depression agent
or a
combination of two or more freezing point depression agents. For example, in
some
embodiments, the freezing point depression agent comprises a first type of
freezing point
depression agent and a second type of freezing point depression agent. The
term
"freezing point depression agent" is given its ordinary meaning in the art and
refers to a
compound which is added to a solution to reduce the freezing point of the
solution. That
is, a solution comprising the freezing point depression agent has a lower
freezing point as
compared to an essentially identical solution not comprising the freezing
point
depression agent. Those of ordinary skill in the art will be aware of suitable
freezing
point depression agents for use in the microemulsions described herein. Non-
limiting
examples of freezing point depression agents include primary, secondary, and
tertiary
alcohols with between 1 and 20 carbon atoms. In some embodiments, the alcohol
comprises at least 2 carbon atoms, alkylene glycols including polyalkylene
glycols, and
salts. Non-limiting examples of alcohols include methanol, ethanol, i-
propanol,
n-propanol, t-butanol, n-butanol, n-pentanol, n-hexanol, and 2-ethyl-hexanol.
In some
embodiments, the freezing point depression agent is not methanol (e.g., due to
toxicity).
Non-limiting examples of alkylene glycols include ethylene glycol (EG),
polyethylene
glycol (PEG), propylene glycol (PG), and triethylene glycol (TEG). In some
embodiments, the freezing point depression agent is not ethylene oxide (e.g.,
due to
toxicity). In some embodiments, the freezing point depression agent comprises
an
alcohol and an alkylene glycol. In some embodiments, the freezing point
depression
agent comprises a carboxycyclic acid salt and/or a di-carboxycylic acid salt.
Another
non-limiting example of a freezing point depression agent is a combination of
choline
chloride and urea. In some embodiments, the microemulsion comprising the
freezing
point depression agent is stable over a wide range of temperatures, for
example, between
about -25 *F to 150 F, or between about -50 F to 200 'F.
The freezing point depression agent may be present in the microemulsion in any
suitable amount. In some embodiments, the freezing point depression agent is
present in
an amount between about 1 wt% and about 40 wt%, or between about 3 wt% and
about
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20 wt%, or between about 8 wt% and about 16 wt%, versus the total
microemulsion
composition. In some embodiments, the freezing point depression agent is
present in an
amount between about 0 wt% and about 70 wt%, or between about 1 wt% and about
40 wt%, or between about 0 wt% and about 25 wt%, or between about 1 wt% and
about
25 wt%, or between about 1 wt% and about 20 wt%, or between about 3 wt% and
about
20 wt%, or between about 8 wt% and about 16 wt%, versus the total
microemulsion
composition.
Further non-limiting examples of other additives include proppants, scale
inhibitors, friction reducers, biocides, corrosion inhibitors, buffers,
viscosifiers, clay
swelling inhibitors, paraffin dispersing additives, asphaltene dispersing
additives, and
oxygen scavengers.
Non-limiting examples of proppants (e.g., propping agents) include grains of
sand, glass beads, crystalline silica (e.g., Quartz), hexamethylenetetramine,
ceramic
proppants (e.g., calcined clays), resin coated sands, and resin coated ceramic
proppants.
Other proppants are also possible and will be known to those skilled in the
art.
Non-limiting examples of scale inhibitors include one or more of methyl
alcohol,
organic phosphonic acid salts (e.g., phosphonate salt), polyacrylate, ethane-
1,2-diol,
calcium chloride, and sodium hydroxide. Other scale inhibitors are also
possible and will
be known to those skilled in the art.
Non-limiting examples of buffers include acetic acid, acetic anhydride,
potassium
hydroxide, sodium hydroxide, and sodium acetate. Other buffers are also
possible and
will be known to those skilled in the art.
Non-limiting examples of corrosion inhibitors include isopropanol, quaternary
ammonium compounds, thiourea/formaldehyde copolymers, propargyl alcohol and
methanol. Other corrosion inhibitors are also possible and will be known to
those skilled
in the art.
Non-limiting examples of biocides include didecyl dimethyl ammonium chloride,
gluteral, Dazomet, bronopol, tributyl tetradecyl phosphonium chloride,
tetrakis
(hydroxymethyl) phosphonium sulfate, AQUCARTM, UCARC1DETM, glutaraldehyde,
sodium hypochlorite, and sodium hydroxide. Other biocides are also possible
and will be
known to those skilled in the art.
- 21 -
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Non-limiting examples of clay swelling inhibitors include quaternary ammonium
chloride and tetramethylammonium chloride. Other clay swelling inhibitors are
also
possible and will be known to those skilled in the art.
Non-limiting examples of friction reducers include petroleum distillates,
ammonium salts, polyethoxylated alcohol surfactants, and anionic
polyacrylamide
copolymers. Other friction reducers are also possible and will be known to
those skilled
in the art.
Non-limiting examples of oxygen scavengers include sulfites, and bisulfites.
Other oxygen scavengers are also possible and will be known to those skilled
in the art.
Non-limiting examples of paraffin dispersing additives and asphaltene
dispersing
additives include active acidic copolymers, active alkylated polyester, active
alkylated
polyester amides, active alkylated polyester imides, aromatic naphthas, and
active amine
sulfonates. Other paraffin dispersing additives are also possible and will be
known to
those skilled in the art.
In some embodiments, for the formulations above, the other additives are
present
in an amount between about 0 wt% about 70 wt%, or between about 0 wt % and
about 30
wt%, or between about 1 wt% and about 30 wt%, or between about 1 wt% and about
25
wt%, or between about 1 and about 20 wt%, versus the total microemulsion
composition.
In some embodiments, the microemulsion comprises an acid or an acid precursor.
For example, the microemulsion may comprise an acid when used during acidizing
operations. The microemulsion may comprise a single acid or a combination of
two or
more acids. For example, in some embodiments, the acid comprises a first type
of acid
and a second type of acid. Non-limiting examples of acids or di-acids include
hydrochloric acid, acetic acid, formic acid, succinic acid, maleic acid, malic
acid, lactic
acid, and hydrochloric-hydrofluoric acids. In some embodiments, the
microemulsion
comprises an organic acid or organic di-acid in the ester (or di-ester) form,
whereby the
ester (or diester) is hydrolyzed in the wellbore and/or reservoir to form the
parent organic
acid and an alcohol in the wellbore and/or reservoir. Non-limiting examples of
esters or
di-esters include isomers of methyl formate, ethyl formate, ethylene glycol
diformate,
a,a-4-trimethy1-3-cyclohexene-1 -methylformate, methyl lactate, ethyl lactate,
a,a-4-
trimethyl 3-cyclohexene-1-methyllactate, ethylene glycol dilactate, ethylene
glycol
diacetate, methyl acetate, ethyl acetate, a,a,-4-trimethy1-3-cyclohexene-1-
methylacetate,
dimethyl succinate, dimethyl maleate, di(a,a-4-trimethy1-3-cyclohexene-1-
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methyl)succinate, 1-methy1-4-(1-methyletheny1)-cyclohexylfonnate, 1-methy1-4-
(1-
ethylethenyl)cyclohexylactate, 1-methy1-4-(1-methylethenyl)cyclohexylacetate,
di(1-
methy-4-(1-methylethenyl)cyclohexyl)succinate.
In some embodiments, the microemulsion comprises a salt. The presence of the
salt may reduce the amount of water needed as a carrier fluid, and in
addition, may lower
the freezing point of the microemulsion. The microemulsion may comprise a
single salt
or a combination of two or more salts. For example, in some embodiments, the
salt
comprises a first type of salt and a second type of salt. Non-limiting
examples of salts
include salts comprising K, Na, Br, Cr, Cs, or Li, for example, halides of
these metals,
including NaC1, KC1, CaCl2, and MgCl2.
In some embodiments, the microemulsion comprises a clay stabilizer. The
microemulsion may comprise a single clay stabilizer or a combination of two or
more
clay stabilizers. For example, in some embodiments, the salt comprises a first
type of
clay stabilizer and a second type of clay stabilizer. Non-limiting examples of
clay
stabilizers include salts above, polymers (PAC, PHPA, etc.), glycols,
sulfonated asphalt,
lignite, sodium silicate, and choline chloride.
In some embodiments, for the formulations above, the other additives are
present
in an amount between about 0 wt% about 70 wt%, or between about 1 wt% and
about 30
wt%, or between about 1 wt% and about 25 wt%, or between about 1 and about 20
wt%,
versus the total microemulsion composition.
In some embodiments, the components of the microemulsion and/or the amounts
of the components may be selected so that the microemulsion is stable over a
wide-range
of temperatures. For example, the microemulsion may exhibit stability between
about
-40 F and about 400 F, or between -40 F. and about 300 F, or between about
-40 '1'
and about 150 *F. Those of ordinary skill in the art will be aware of methods
and
techniques for determining the range of stability of the microemulsion. For
example, the
lower boundary may be determined by the freezing point and the upper boundary
may be
determined by the cloud point and/or using spectroscopy methods. Stability
over a wide
range of temperatures may be important in embodiments where the microemulsions
are
being employed in applications comprising environments wherein the temperature
may
vary significantly, or may have extreme highs (e.g., desert) or lows (e.g.,
artic).
The microemulsions described herein may be formed using methods known to
those of ordinary skill in the art. In some embodiments, the aqueous and non-
aqueous
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phases may be combined (e.g., the water and the terpene(s)), followed by
addition of a
surfactant(s) and optionally other components (e.g., freezing point depression
agent(s)) and
agitation. The strength, type, and length of the agitation may be varied as
known in the art
depending on various factors including the components of the microemulsion,
the quantity of
the microemulsion, and the resulting type of microemulsion formed. For
example, for small
samples, a few seconds of gentle mixing can yield a microemulsion, whereas for
larger
samples, longer agitation times and/or stronger agitation may be required.
Agitation may be
provided by any suitable source, for example, a vortex mixer, a stirrer (e.g.,
magnetic stirrer),
etc.
Any suitable method for injecting the microemulsion (e.g., a diluted
microemulsion)
into a wellbore may be employed. For example, in some embodiments, the
microemulsion,
optionally diluted, 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.
In some embodiments, experiments may be carried out to determine displacement
of
residual aqueous treatment fluid by formation crude oil or formation gas by a
microemulsion
(e.g., a diluted microemulsion). For example, displacement of residual aqueous
treatment
fluid by formation crude oil may be determined using the method described in
Example 3
and/or displacement of residual aqueous treatment fluid by formation gas may
be determined
using the method described in Example 2.
For convenience, certain terms employed in the specification, examples, and
appended claims are listed here.
Definitions of specific functional groups and chemical terms are described in
more
detail below. For purposes of this invention, the chemical elements are
identified in
accordance with the Periodic Table of the Elements, CAS version, Handbook of
Chemistry
and Physics, 75th
hOl inside cover, and specific functional groups are generally defined as
described therein. Additionally, general principles of organic chemistry, as
well as specific
functional moieties and reactivity, are described in Organic Chemistry, Thomas
Sorrell,
University Science Books, Sausalito: 1999.
Certain compounds of the present invention may exist in particular geometric
or
stereoisomeric forms. The present invention contemplates all such compounds,
including cis-
24
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and trans-isomers, R- and S-enantiomers, diastereomers, (D)-isomers, (0-
isomers, the
racemic mixtures thereof, and other mixtures thereof, as falling within the
scope of the
invention. Additional asymmetric carbon atoms may be present in a substituent
such as an
alkyl group. All such isomers, as well as mixtures thereof, are intended to be
included in this
invention.
Isomeric mixtures containing any of a variety of isomer ratios may be utilized
in
accordance with the present invention. For example, where only two isomers are
combined,
mixtures containing 50:50, 60:40, 70:30, 80:20, 90:10, 95:5, 96:4, 97:3, 98:2,
99:1, or 100:0
isomer ratios are all contemplated by the present invention. Those of ordinary
skill in the art
will readily appreciate that analogous ratios are contemplated for more
complex isomer
mixtures.
The term "aliphatic," as used herein, includes both saturated and unsaturated,
nonaromatic, straight chain (i.e. unbranched), branched, acyclic, and cyclic
(i.e. carbocyclic)
hydrocarbons, which are optionally substituted with one or more functional
groups. As will
be appreciated by one of ordinary skill in the art, "aliphatic" is intended
herein to include, but
is not limited to, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, and
cycloallcynyl moieties.
Thus, as used herein, the term "alkyl" includes straight, branched and cyclic
alkyl groups. An
analogous convention applies to other generic terms such as "alkenyl",
"alkynyl", and the
like. Furthermore, as used herein, the telins "alkyl", "alkenyl", "alkynyl",
and the like
encompass both substituted and unsubstituted groups. In certain embodiments,
as used herein,
"aliphatic" is used to indicate those aliphatic groups (cyclic, acyclic,
substituted,
unsubstituted, branched or unbranched) having 1-20 carbon atoms. Aliphatic
group
substituents include, but are not limited to, any of the substituents
described herein, that result
in the formation of a stable moiety (e.g., aliphatic, alkyl, alkenyl, alkynyl,
heteroaliphatic,
heterocyclic, aryl, heteroaryl, acyl, oxo, imino, thiooxo, cyano, isocyano,
amino, azido, nitro,
hydroxyl, thiol, halo, aliphaticamino, heteroaliphaticamino, alkylamino,
heteroalkylamino,
arylamino, heteroarylamino, alkylaryl, arylalkyl, aliphaticoxy,
heteroaliphaticoxy, alkyloxy,
heteroalkyloxy, aryloxy, heteroaryloxy, aliphaticthioxy,
heteroaliphaticthioxy, alkylthioxy,
heteroalkylthioxy, arylthioxy, heteroarylthioxy, acyloxy, and the like, each
CA 3059006 2019-10-17
of which may or may not be further substituted).
The term "alkane" is given its ordinary meaning in the art and refers to a
saturated hydrocarbon molecule. The term "branched alkane" refers to an alkane
that
includes one or more branches, while the term "unbranched alkane" refers to an
alkane
that is straight-chained. The term "cyclic alkane" refers to an alkane that
includes one or
more ring structures, and may be optionally branched. The term "acyclic
alkane" refers
to an alkane that does not include any ring structures, and may be optionally
branched.
The term "alkene" is given its ordinary meaning in the art and refers to an
unsaturated hydrocarbon molecule that includes one or more carbon-carbon
double
bonds. The term "branched alkene" refers to an alkene that includes one or
more
branches, while the term "unbranched alkene" refers to an alkene that is
straight-chained.
The term "cyclic alkene" refers to an alkene that includes one or more ring
structures,
and may be optionally branched. The term "acyclic alkene" refers to an alkene
that does
not include any ring structures, and may be optionally branched.
The term "aromatic" is given its ordinary meaning in the art and refers to
aromatic carbocyclic groups, having a single ring (e.g., phenyl), multiple
rings (e.g.,
biphenyl), or multiple fused rings in which at least one is aromatic (e.g.,
1,2,3,4-
tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl). That is, at least one
ring may
have a conjugated pi electron system, while other, adjoining rings can be
cycloalkyls,
cycloalkenyls, cycloalkynyls, aryls and/or heterocyclyls.
The term "aryl" is given its ordinary meaning in the art and refers to
aromatic
carbocyclic groups, optionally substituted, having a single ring (e.g.,
phenyl), multiple
rings (e.g., biphenyl), or multiple fused rings in which at least one is
aromatic (e.g.,
1,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl). That is, at
least one ring
may have a conjugated pi electron system, while other, adjoining rings can be
cycloalkyls, cycloalkenyls, cycloalkynyls, aryls and/or heterocyclyls. The
aryl group
may be optionally substituted, as described herein. Substituents include, but
are not
limited to, any of the previously mentioned substitutents, i.e., the
substituents recited for
aliphatic moieties, or for other moieties as disclosed herein, resulting in
the folination of
a stable compound. In some cases, an aryl group is a stable mono- or
polycyclic
unsaturated moiety having preferably 3-14 carbon atoms, each of which may be
substituted or unsubstituted.
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These and other aspects of the present invention will be further appreciated
upon
consideration of the following Examples, which are intended to illustrate
certain
particular embodiments of the invention but are not intended to limit its
scope, as defined
by the claims.
Examples
Example 1:
A series of laboratory tests were conducted to characterize the effectiveness
of a
series of microemulsions incorporating a range of terpenes. For these
experiments,
samples of a base microemulsion were prepared in which a detergent range
alcohol
ethoxylate surfactant was first blended in a 1:1 ratio with isopropyl alcohol.
Suitable
detergent range alcohol ethoxylate surfactants include Neodol 25-7 (obtained
from Shell
Chemical Co.; e.g., a surfactant comprising linear C12-Ci5 alcohol ethoxylates
with on
average 7 moles of ethylene oxide), or comparable linear and branched alcohol
ethoxylate surfactants available from SASOL, Huntsman or Stepan. The examples
in
Table 2 were prepared using Neodol 25-7. 46 parts by weight of this blend was
mixed
with 27 parts by weight of terpene and 27 parts by weight of water. Although
substantial
differences in the microemulsion phase behavior of the different terpenes were
observed,
this composition was chosen because at this composition, the exemplary
terpenes that
were tested spontaneously formed transparent stable microemulsions with gentle
mixing
of the ingredients. Subsequently, 1-2 gallons per thousand (gpt) dilutions
were prepared
and tested.
A transparent low-viscosity mixture that exhibited the characteristic
properties of
a microemulsion was prepared using 46% by weight of a blend of Neodol 25-7 and
isopropyl alcohol, 27% by weight of water, and 27% by weight of technical
grade d-
limonene. This mixture was identified as a microemulsion based on the
spontaneous
formation with minimal mechanical energy input to form a clear dispersion from
an
immiscible mixture of water and d-limonene upon addition of an appropriate
amount of
surfactant and co-solvent. The order of mixing of this and other compositions
described
in this example were not necessary, but for convenience, a procedure was
generally
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followed in which a mixture of the surfactant and the isopropyl alcohol was
first
prepared then combined that with a mixture of the terpene and water. With
small
samples, in the laboratory, a few seconds of gentle mixing yielded a
transparent
dispersion.
The non-limiting terpenes used this example were classified by measuring their
phase inversion temperature (PIT) using methods described in the literature
(e.g., see
Strey, Microemulsion microstructure and interfacial curvature. Colloid &
Polymer
Science, 1994. 272(8): p. 1005-1019; Kahlweit et al., Phase Behavior of
Ternary
Systems of the Type H2O-Oil-Nonionic Amphiphile (Microemulsions). Angewandte
Chemie International Edition in English, 1985. 24(8): p. 654-668.). As will be
known in
the art, the PIT measured for a given oil or solvent depends on the surfactant
and
aqueous phase in which it is measured. In this example, a 1:1 mixture of
terpene solvent
and de-ionized water was combined with varying amounts of a 1:1 blend of
Neodol 25-7
and IPA and the upper and lower temperature boundaries of the one-phase
.. microemulsion region were determined. A phase diagram such as this,
plotting
temperature against surfactant concentration at a constant oil-to-water ratio
is often
called a "fish" diagram or a Kahlweit plot. The phase inversion temperature
was
determined as the point at the "fish-tail" at which the temperature range of
one-phase
microemulsion closes to a vertex. In this example, the temperature at the
vertex was
selected as the PIT. An exemplary fish diagram indicating the PIT is shown in
Figure 1.
For the terpene solvents used in this example, the PIT values which were
measured using
this above-described procedure are shown in Table 2. Those terpenes containing
alcohol
groups (linalool, geraniol, nopol, a-terpineol and menthol), gave PIT values
between
-4 C and 16 C. Eucalyptol, containing an ether-oxygen, and menthone,
containing a
.. carbonyl oxygen, gave somewhat higher values near 30 C. D-limonene gave 43
C,
while other non-oxygen containing terpenes gave values between 48-58 C. As
described
in more detail below, displacement of residual treatment fluid (containing 1-2
gpt of the
microemulsion well treatment) from a sand pack by crude oil or gas was found
to
correlate to the PIT values.
Table 2 shows results for displacement of residual aqueous treatment fluid by
oil
and gas for formulations (e.g., using the experimental procedures outlined in
Examples 3
and 4) using dilutions of the microemulsions prepared in this example (e.g.,
the
microemulsions comprising 46 parts of 1:1 Neodol 25-7, 27 parts deionized
water, and
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27 parts terpene solvent). The dilutions were prepared of each microemulsion
in 2% KC1,
at 2 gpt. The table shows that the terpene solvents with PIT values higher
than 43 C all
give approximately 90% recovery, while those below 43 C give significantly
lower
recovery. Table 2 also shows displacement by gas results for the dilutions
that
demonstrates that terpene solvents with PIT values higher than 43 C give
approximately
40% recovery, while those with PIT values below 43 C give significantly
higher
recovery.
Table 2. PIT values for various terpene solvents (e.g., measured at 1:1 water-
oil).
Displacement results for 2 gpt dilution of microemulsions comprising 46:27:27
surfactant:water:terpene + isopropanol formulations.
Terpene Phase Inversion % displacement of % displacement of
Temperature ( C) brine by crude oil brine by gas
Linalool -4 81.9
Geraniol -0.5 69.3 67.8
Nopol 2.5 80.3 58.8
a-Terpineol 4.6 80 92.9
Menthol 16 49.7
Eucalyptol 31 54.6
Menthone 32 79.4
d-Limonene 43 89.3 45.6
Terpinolene 48 90.5 41.8
P-Occimene 49 90.2 44.2
y-Terpinene 49 89 32.2
a-Pinene 57 89.9 38.7
Citronellene 58 88.2 40.5
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Table 3. Oil and Gas displacement results for a-pinene and a-terpineol as a
function of
surfactant concentration and solvent-to-water ratio.
Formulation Terpene % displacement of % displacement of
T/S/W* brine by crude oil brine by gas
27-46-27 a-terpineol 80 92.9
27-46-27 a-pinene 89.9 38.7
21-46-33 a-terpineol 88 83
21-46-33 a-pinene 87 46
11-46-43 a-terpineol 88.5 80
11-46-43 a-pinene 96 47
15-56-28 a-terpineol 87.8 85
15-56-28 a-pinene 88.6 52
.. *T/S/W stands for terpene weight %/1:1 surfactant-IPA weight %/deionized
water wt%
The results shown in Table 3 demonstrate that at a 1:1 ratio of terpene to
water,
and 46 weight % surfactant-IPA, the high PIT a-pinene performed better on oil
displacement and much poorer on gas displacement than the low PIT a-terpineol.
As the
terpene-to-water ratio decreases from 27-27 to 21-33 to 11-43, the difference
in oil
displacement performance decreased, then increased again at the lower level.
Higher
surfactant levels did not substantially increase or decrease the displacement
(which may
suggest that the microemulsion is performing differently than a surfactant
package
lacking the terpene solvent). The displacement by gas was better for the low
PIT a-
terpineol than for the high PIT a-pinene.
Example 2:
Microemulsions were prepared having the following formulation, wherein the
terpene was varied as indicated in Table 4. The water to terpene ratio was
about 5.5:1..
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Microemulsion formulation:
Water 27.35 wt%
Ethoxylated alcohol surfactant 52.5 wt%
2-propanol 8.75 wt%
Triethylene Glycol 3 wt%
Propylene Glycol 3.3 wt%
Ethoxylated castor oil 0.1 wt%
Terpene 5 wt%
1 gallon per thousand dilutions were prepared of each microemulsion in 2% KC1.
The dilutions were then employed to determine the displacement of brine by oil
and gas
(e.g., using the experimental procedures outlined in Examples 3 and 4). The
results are
given in Table 4.
Table 4: Brine displacement by oil and gas
Terpene Effectiveness of brine Effectiveness of brine
displacement by gas (%) displacement by oil (%)
d-limonene 79 64
et-terpineol 90 88
a-pinene 86 87
geraniol 87 89
linalool 88 87
nopol 89 88
turpentine 83 76
menthol 82 90
eucalyptol 77 90
terpinolene 79 72
P-ocimene 71 68
X-terpinene 74 60
citronellene 73 88
Example 3:
This example described a non-limiting experiment for determining displacement
of residual aqueous treatment fluid by formation crude oil. A 25 cm long, 2.5
cm
diameter capped glass chromatography column was packed with 77 grams of 100
mesh
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sand. The column was left open on one end and a PTFE insert containing a
recessed
bottom, 3.2 mm diameter outlet, and nipple was placed into the other end.
Prior to
placing the insert into the column, a 3 cm diameter filter paper disc
(Whatman, #40) was
pressed firmly into the recessed bottom of the insert to prevent leakage of
100 mesh
sand. A 2" piece of vinyl tubing was placed onto the nipple of the insert and
a clamp was
fixed in place on the tubing prior to packing. The columns were gravity-packed
by
pouring approximately 25 grams of the diluted microemulsions (e.g., the
microemulsions
described in Examples 1 or 2, and diluted with 2% KC1, e.g., to about 2 gpt,
or about
1 gpt) into the column followed by a slow, continuous addition of sand. After
the last
ft) portion of sand had been added and was allowed to settle, the excess of
brine was
removed from the column so that the level of liquid exactly matched the level
of sand.
Pore volume in the packed column was calculated as the difference in mass of
fluid prior
to column packing and after the column had been packed. Three additional pore
volumes
of brine were passed through the column. After the last pore volume was
passed, the
level of brine was adjusted exactly to the level of sand bed. Light condensate
oil was
then added on the top of sand bed to form the 5 cm oil column above the bed.
Additional
oil was placed into a separatory funnel with a side arm open to an atmosphere.
Once the
setup was assembled, the clamp was released from the tubing, and timer was
started.
Throughout the experiment the level of oil was monitored and kept constant at
a 5 cm
mark above the bed. Oil was added from the separatory funnel as necessary, to
ensure
this constant level of head in the column. Portions of effluent coming from
the column
were collected into plastic beakers over a measured time intervals. The amount
of fluid
was monitored. When both brine and oil were produced from the column, they
were
separated with a syringe and weighed separately. The experiment was conducted
for
3 hours at which the steady-state conditions were typically reached. The
cumulative % or
aqueous fluid displaced from the column over 120 minute time period, and the
steady-
state mass flow rate of oil at t=120 mm through the column were determined.
Example 4:
This example described a non-limiting experiment for determining displacement
of residual aqueous treatment fluid by formation gas. A 51 cm long, 2.5 cm
inner-diameter capped glass chromatography column was filled with
approximately
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410 20 g of 20/40 mesh Ottawa sand and the diluted microemulsions (e.g., the
microemulsions described in Examples 1 or 2, and diluted with 2% KC1, e.g., to
about
2 gpt, or about 1 gpt) To ensure uniform packing, small amounts of proppant
were
interchanged with small volumes of liquid. Periodically the mixture in the
column was
homogenized with the help of an electrical hand massager, in order to remove
possible
air pockets. Sand and brine were added to completely fill the column to the
level of the
upper cap. The exact amounts of fluid and sand placed in the column were
determined in
each experiment. The column was oriented vertically and was connected at the
bottom to
a nitrogen cylinder via a gas flow controller pre-set at a flow rate of 60
cm3/min. The
valve at the bottom was slowly opened and liquid exiting the column at the top
was
collected into a tarred jar placed on a balance. Mass of collected fluid was
recorded as a
function of time by a computer running a data logging software. The
experiments were
conducted until no more brine could be displaced from the column. The total %
of fluid
recovered was then calculated.
Example 5:
This examples describes a general preparation method for the production of
diluted microemulsion. The microemulsions were prepared in the laboratory by
mixing
the ingredients listed in specific examples. All ingredients are commercially
available
materials. In some embodiments, the components were mixed together in the
order
water-alcohol-surfactant- citrus terpene solvent, but other order of addition
may also be
employed. The mixtures were then agitated on a magnetic stirrer for 5-10
minutes. The
microemulsions were then diluted to concentrations of 1 or 2 gallons per 1000
gallons
with 2% KCl brine and these diluted fluids were used in displacement
experiments
described in Examples 3 and 4.
It will be evident to one skilled in the art that the present disclosure is
not limited
to the foregoing illustrative examples, and that it can be embodied in other
specific forms
without departing from the essential attributes thereof. It is therefore
desired that the
examples be considered in all respects as illustrative and not restrictive,
reference being
made to the appended claims, rather than to the foregoing examples, and all
changes
CA 3059006 2019-10-17
which come within the meaning and range of equivalency of the claims are
therefore
intended to be embraced therein.
While several embodiments of the present invention have been described and
illustrated herein, those of ordinary skill in the art will readily envision a
variety of other
means and/or structures for performing the fimctions and/or obtaining the
results and/or
one or more of the advantages described herein, and each of such variations
and/or
modifications is deemed to be within the scope of the present invention. More
generally,
those skilled in the art will readily appreciate that all parameters,
dimensions, materials,
and configurations described herein are meant to be exemplary and that the
actual
.. parameters, dimensions, materials, and/or configurations will depend upon
the specific
application or applications for which the teachings of the present invention
is/are used.
Those skilled in the art will recognize, or be able to ascertain using no more
than routine
experimentation, many equivalents to the specific embodiments of the invention
described herein. It is, therefore, to be understood that the foregoing
embodiments are
presented by way of example only and that, within the scope of the appended
claims and
equivalents thereto, the invention may be practiced otherwise than as
specifically
described and claimed. The present invention is directed to each individual
feature,
system, article, material, kit, and/or method described herein. In addition,
any
combination of two or more such features, systems, articles, materials, kits,
and/or
methods, if such features, systems, articles, materials, kits, and/or methods
are not
mutually inconsistent, is included within the scope of the present invention.
The indefinite articles "a" and "an," as used herein in the specification and
in the
claims, unless clearly indicated to the contrary, should be understood to mean
"at least
one."
The phrase "and/or," as used herein in the specification and in the claims,
should
be understood to mean "either or both" of the elements so conjoined, i.e.,
elements that
are conjunctively present in some cases and disjunctively present in other
cases. Other
elements may optionally be present other than the elements specifically
identified by the
"and/or" clause, whether related or unrelated to those elements specifically
identified
unless clearly indicated to the contrary. Thus, as a non-limiting example, a
reference to
"A and/or B," when used in conjunction with open-ended language such as
"comprising"
can refer, in one embodiment, to A without B (optionally including elements
other than
CA 3059006 2019-10-17
B); in another embodiment, to B without A (optionally including elements other
than A);
in yet another embodiment, to both A and B (optionally including other
elements); etc.
As used herein in the specification and in the claims, "or" should be
understood
to have the same meaning as "and/or" as defined above. For example, when
separating
items in a list, "or" or "and/or" shall be interpreted as being inclusive,
i.e., the inclusion
of at least one, but also including more than one, of a number or list of
elements, and,
optionally, additional unlisted items. Only terms clearly indicated to the
contrary, such as
"only one of' or "exactly one of," or, when used in the claims, "consisting
of," will refer
to the inclusion of exactly one element or a list of elements. In general, the
term "or" as
used herein shall only be interpreted as indicating exclusive alternatives
(i.e. "one or the
other but not both") when preceded by terms of exclusivity, such as "either,"
"one of,"
"only one of," or "exactly one of." "Consisting essentially of," when used in
the claims,
shall have its ordinary meaning as used in the field of patent law.
As used herein in the specification and in the claims, the phrase "at least
one," in
reference to a list of one or more elements, should be understood to mean at
least one
element selected from any one or more of the elements in the list of elements,
but not
necessarily including at least one of each and every element specifically
listed within the
list of elements and not excluding any combinations of elements in the list of
elements.
This definition also allows that elements may optionally be present other than
the
elements specifically identified within the list of elements to which the
phrase "at least
one" refers, whether related or unrelated to those elements specifically
identified. Thus,
as a non-limiting example, "at least one of A and B" (or, equivalently, "at
least one of A
or B," or, equivalently "at least one of A and/or B") can refer, in one
embodiment, to at
least one, optionally including more than one, A, with no B present (and
optionally
including elements other than B); in another embodiment, to at least one,
optionally
including more than one, B, with no A present (and optionally including
elements other
than A); in yet another embodiment, to at least one, optionally including more
than one,
A, and at least one, optionally including more than one, B (and optionally
including other
elements); etc.
In the claims, as well as in the specification above, all transitional phrases
such as
"comprising," "including," "carrying," "having," "containing," "involving,"
"holding,"
and the like are to be understood to be open-ended, i.e., to mean including
but not limited
to. Only the transitional phrases "consisting of' and "consisting essentially
of' shall be
CA 3059006 2019-10-17
closed or semi-closed transitional phrases, respectively.
36
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