Note: Descriptions are shown in the official language in which they were submitted.
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1049926 :
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, ~ sAC~GROUND OF THE INVENTION ¦
; Field of the Invention
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This invention relates to injecting a micellar dis-
~; persion into a subterranean formation and displacing it
~ toward a production means in fluid communication therewith :
.: : to recover crude oil therethrough. .
. Description of the Prior Art
The prior art recognizes that micellar dispersions are
useful to displace crude oil from subterranean formations,
, e.g. se .5 Patent Nos. 3,254 714: 3,275,075; 3,506,070 ¦~
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1 3,497,006; 3,613,786; 3,734,185; 3,740,343; 3,827,496; and2 other patents defining surfactant systems and assigned to
3 Marathon Oil Company, Esso Production Research Company,
4 Shell Oil Company, Union Oil Company, Mobil Oil Company,
5 ~exaco Oil Company, etc. The micellar dispersion is
6 usually followed by an aqueous mobility buffer and then a
water drive to displace the crude oil from the reservoir.
8 The prior art has taught different methods of enhancing
9 the compatibility of the micellar dispersion with the
connate water to obtain improved oil recovery:
11 Davis in U.S. 3,476,184 teaches that the micellar dis-
12 persion slug should have a small hydrophilicy in the front
13 portion and a relatively larger hydrophilicy in the back
1~ portion thereof.
Jones, in U.S. 3,482,631 teaches that improved oil
16 recovery is obtained by injecting before the micellar dis-
17 persion an aqueous pre-slug containing a viscosity imparting
18 agent and electrolyte and/or cosurfactant.
19 Jones also teaches in U.S. 3,520,366 improved oil
recovery can be obtained by injecting previous to the
21 micellar dispersion an aqueous slug containing cosurfactant
22 or electrolyte and cosurfactant.
23 Poettmann in U.S. 3,324,944 teaches improved oil
24 recovery is obtained by injecting previous to the micellar
dispersion a hydrocarbon preslug to preferentially build up
26 an oil bank ahead of the micellar dispersion which in turn
27 preferentially pushes oil through the formation and displaces
28 a portion of the connate water.
29 Gogarty in U.S. 3,343,597 teaches improved oil recovery
by injecting an aqueous slug of controlled ions to protect
31 a subsequently injected micellar dispersion from the connate
water.
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1 Tosch et al in U.S. 3,561,530 teach improved flooding
2 by enhancing the compatibility of the micellar dispersion
3 with the connate water by first determining the salinity of
4 the connate water, then selecting the desired mole ratio of
water to surfactant within the micellar solution based on an
6 equilibrium curve.
7 Burdge in U.S. 3,623,553 teaches that the brine toler-
ance of a micellar dispersion can be increased by incorpora-
9 ting low average equivalent weight surfactants within the
micellar dispersion or increasing the average equivalent
11 weight of the surfactant to obtain lower brine tolerances.
12 Sydans~ et al in U.S. 3,648,770 teach improved flooding
13 of a reservoir by first determining the predominant cation
14 within the connate water, then designing the micellar
dispersion to contain a cation which has a greater affinity
16 for the petroleum sulfonate within the micellar dispersion
17 than the predominant cation within the connate water, and
18 then injecting and displacing the micellar dispersion through
19 the formation to recover crude oil therethrough.
Gogarty in U.S. 3,648,773 teaches that improved flooding
21 of a reservoir containing relatively high concentration of
22 divalent cations is obtained by designing the micellar
23 dispersion to contain a relatively low average equivale~_
24 weight sulfonate.
Knight et al in U.S. 3,844,350 teach improved flooding
26 of reservoirs containing high divalent cation concentrations
27 within the connate water by injecting previous to the
28 micellar dispersion an aqueous preslug containing 50-2,000
29 ppm of a biopolymer--the biopolymer "insulates" the micellar
dispersion from the connate water.
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1049926
1 SUMMARY OF THE INV~NTION
2 Applicants have discovered that improved flooding with
3 micellar dispersions containing cosurfactant~s) is obtained
4 by increasing the hydrophilicy of the cosurfactant where
the salinity of the connate water is high or decreasing
6 the hydrophilicy where the salinity of the connate water is
less. The cosurfactant(s) is also designed to impart the
8 desired viscosity to the micellar dispersion and also to
9 permit the dispersion to solubilize at most only a minimum
amount of the connate water, i.e. the dispersion can be
11 dehydrated to a limited extent by the connate water but
12 preferably the dispersion is designed to solubilize little
13 or no connate water.
14
BRIEF DESCRIPTION OF T~IE DRAWINGS
16 Figure l illustrates the relationship between cosur-
17 factant concentration and brine concentration on the phase
18 behavior of a micellar dispersion. This micellar dispersion
19 is identified in Example I. Electrolyte concentrations
shown on the abscissa of Figure I include only salts added
21 to the water used to make up the micellar dispersion and do
22 not include 3900 ppm of ammonium sulfate concentration
23 contributed by the petroleum sulfonate. The added salts or
24 electrolyte are 0.9% by weight calcium and magnesium, and
99.l~ sodium and chloride. As this graph illustrates, added
26 electrolyte reduces the amount of n-pentanol required to
27 solubilize the hydrocarbon. Also, an increase in electrolyte
28 reduces the alcohol concentration that causes an aqueous
29 phase to be expelled from the micellar dispersion and also
results in a narrowing of the "single-phase band" with
31 increasing electrolyte concentration. The negative slope of
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1 the single phase region is characteristic of substantially
2 water-insoluble cosurfactants.
3 Figure 2 illustrates the cosurfactant concentration
4 required to achieve "minimum viscosity" of the micellar
dispersion as a function of water salinity for dispersions
6 made from a variety of surfactant types. Compositions of
these micellar dispersions are defined in Example II. The
8 inverted triangular data points represent a micellar dis-
9 persion containing O.l~ of isopropyl alcohol and the upright
triangular data points represent a micellar dispersion
11 containing 0.02% isopropyl alcohol. The circular data
12 points represent a micellar dispersion containing ~.41%
13 isopropyl alcohol while the square data points represent a
14 micellar dispersion containing no isopropyl alcohol. The
point of "minimum viscosity" corresponds approximately to
16 the center of the "single-phase stability band" as shown in
17 Figure l, e.g. for an electrolyte concentration of 4,000
18 ppm, the cosurfactant concentration to achieve minimum
19 viscosity is about l.35. Also, this point of minimum viscosity
corresponds to the point farthest removed from slug instability.
21 The difference in the required n-amyl alcohol concentration
22 between the two upper or the two lower curves is mainly due to
23 different isopropyl alcohol concentrations in the micellar
24 dispersion slugs.
26 PREFERRED EMBODIMENTS OF THE INVENTION
27 The term "micellar dispersion" as used herein is meant
28 to include micellar solutions, microemulsions, "transparent
29 emulsions", hydrous soluble oils, micellar systems con-
taining lamellar micelles, etc. These systems can be oil-
31 external or water-external, they can act like they are
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1049926
1 either oil-external or water-external or both, and they can
2 also be in an "intermediate region" between a "classically"
3 oil-external micellar system and a "classically" water-
4 external micellar system. However, all of the systems,
regardless of the externality properties, are thermodynam-
6 ically stable and optically clear; but, color bodies within
7 the different components can prevent the transmission of
8 light.
9 The micellar dispersions are composed of hydrocarbon,
water, surfactant, cosurfactant, and optionally electrolyte.
11 Additional component(s) can be added to impart desired
12 properties to the micellar dispersion, e.g. high molecular
13 weight polymers to impart desired mobility characteristics.
14 However, these components must be compatible with the other
components of the dispersion and not impart adverse properties
16 to the system.
17 Examples of the components useful with the micellar
18 dispersion are defined within the patents mentioned in the
19 "Description of the Prior Art".
The surfactant can be anionic, nonionic, or cationic,
21 or mixtures thereof. Preferably, it is a monovalent cation-
22 containing petroleum sulfonate obtained by sulfonating a
23 fraction of crude oil, e.g. gas oil, or whole or topped
24 crude oil. Desirably, the petroleum sulfonate has an
average equivalent weight within the range of about 350 to
26 about 525 and more preferably about 390 to about 470. The
27 petroleum sulfonate can contain unreacted hydrocarbon and
28 salts (hereinafter defined as electrolytes).
The hydrocarbon is typically crude oil, a fraction
thereof, unreacted vehicle oil within the surfactant,
31 synthesized hydrocarbon, mixtures thereof, or like materials.
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1 water within the micellar dispersion can be distilled
2 water, fresh water, or water containing a moderate amount of
3 salts. Typically, the water contains about 5 to about
4 50,000 ppm of TDS (total dissolved solids). Preferably, the
water does not contain sufficient amounts of multi-valent
6 cations to displace a significant amount of the monovalent
7 cations on the surfactant.
8 Electrolytes useful include water-soluble inorganic
9 salts, inorganic bases, inorganic acids, or mixtures thereof.
Typically, the salts are reaction by-products from the
11 preferred petroleum sulfonate, e.g. ammonium sulfate, ammonium
12 sulfite, sodium sulfate, sodium sulfite, etc., but the
13 electrolytes can be added or blended with electrolytes
14 within the micellar dispersion mixture.
The cosurfactant, also known as a semi-polar organic
16 compound, cosolubilizer, or stabilizing agent, is an organic
17 compound(s) containing about l to about 25 or more carbon
18 atoms and more preferably about 3 to about 16 carbon atoms.
19 It can be an alcohol, amide, amino compound, ester, aldehyde,
ketone, complexes thereof, or a compound containing one or
21 more of amido, hydroxy, bromo, chloro, carbonato, mercapto,
22 oxo, oxy, carbonyl, or like groups, or mixtures thereof.
23 Specific examples include isopropanol, butanol, amyl alcohols,
24 hexanols, octanols, decyl alcohols, alkyl aryl alcohols such
as n-nonyl phenol and p-nonyl phenol, 2-butoxyhexanol,
26 alcoholic liquors such as fusel oil, mixed isomers of primary
27 amyl or hexyL alcohols such as UCAR-HCO (marketed by Union
28 Carbide Company, N.Y., N.Y.), blends of Cl2, Cl3, Cl4, Cl5,
29 etc. linear primary alcohols such as Neodal alcohols (marketed
by Shell Chemical Co.), ethoxylated alcohols such as alcohols
31 containing 4 to about 16 carbon atoms that are ethoxylated
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1 and optio~ally sulfated, hydrogenated hydrocarbons such as
2 hydrogenated croton oil, amidized hydrocarbons, and like
3 materials. The preferred cosurfactant is an alcohol which
4 can be primary, secondary or tertiary alcohol or mixtures
thereof and can optionally be ethoxylated and/or sulfated.
6 Concentration of the components within the micellar
7 dispersion vary depending upon the particular component and
8 the particular properties desired of the micellar dispersion.
9 Typically, the concentration is about 4 to about 56% and
preferably about 5 to about 50% and more preferably about
11 6 to about 20% hydrocarbon, about 40 to about 92% and preferably
12 about 60 to about 85% and more preferably about 65 to about
13 80% water, about 4 to about 20% or more and preferably about
14 6 to about 16% and more preferably about 7 to about 12% of
15 surfactant, about 0.01 to about 20% and preferably about
16 0.05 to about 10% and more preferably about 0.1 to about 1~
17 of cosurfactant, and about 0.001 to about 10% and preferably
18 about 0.01 to about 7.5% and more preferably about 0.1 to
19 about 5% of electrolyte.
The micellar dispersion is injected into the formation
21 in volume amounts of 1 to about 50% or more, and preferably
22 about 4 to about 15% FPV (formation pore volume). It is
23 preferably followed by a mobility buffer, e.g. an aqueous
24 solution containing a water~soluble polymer which imparts
2~ permeability reduction to the formation and/or viscosity
26 increasing properties to the aqueous solution--examples of
27 volume amounts include about 10 to about 200% FPV or more
28 and preferably about 50 to about 150% FPV, and more prefer-
29 ably about 60 to about 100% FPV. A water drive can be
injected to displace the micellar dispersion and the mobility
31 buffer toward a production well in fluid communication with
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1049926
1 the formation to recover crude oil thr~ugh said production
well.
3 Wi~h the proper type and concentration of cosurfactant(s),
4 a micellar dispersion can, within limits, be designed to
accommodate a particular salinity of a connate water. Also,
single-phase micellar dispersion systems can be formulated
7 at a given cosurfactant concentration over a range of
8 electrolyte concentrations in the connate water or through
9 a cosurfactant range at a fixed electrolyte concentration.
Increasing the hydrophilicy of the cosurfactant generally
11 increases the amount of an oleophilic cosurfactant, or less
12 hydrophilic cosurfactant, that is needed with certain micellar
13 flooding systems. The micellar dispersion slug must be
14 designed by properly selecting the desired type and concentration
of the cosurfactant(s), preferably alcohols, to obtain
16 optimum oil recovery with the particular salinity of the
17 connate water. Such can ~e accomplished by blendin~ two or
18 more cosurfactants, or by choosing a particular cosurfactant(s)
19 and then making up the dispersion--cosurfactant choice will
depend upon the type and concentration of the other components
21 of the micellar dispersion, the properties of the formation
22 fluids ti.e. crude oil and connate water) and gas if present,
23 the desired mobility design for the flooding process, the
24 reservoir conditions, etc.
The micellar dispersion is preferably designed such
26 that the cosurfactant concentration and type within the
27 micellar dispersion will solubilize only a minimum amount
28 and preferably no connate water or only a minimum amount of
29 the water within the micellar dispersion is permitted to be
expelled or dehydrated from the micellar dispersion. If the
31 connate water is permitted to be solubilized substantially
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10499Z6
1 ¦ within the micellar dispersion, this can cause instability
2 ¦ to occur within the micellar dispersion, resulting in the
3 ¦ formation of an emulsion, loss of mobility control, etc. and
4 ¦ an overall adverse influence on the flooding proeess.
5 ¦ Tne solubilization properties of the micellar dis-
6 ¦ persion are controlled by the cosurfactant within the
7 ¦ micellar dispersion. The coneentration of hydrophilie eo-
8 ¦ surfactants inereases as the salinity of the eonnate water
9 ¦ inereases and/or the concentration of oleophilie eosurfac-
10 ¦ tants deereases as the salinity of the eonnate water inereases.
11 ¦ It may be desirable to eombine a hydrophilie and an oleophilic
12 ¦ cosurfactant within the micellar dispersion in order to
13 ¦ obtain desired viseosity eharaeteristics of the mieellar
14 dispersion. If the latter is desirable, the hydrophilie and
oleophilie eosurfaetants must be blended in the right ratio
16 and present in the optimum coneentration to obtain the
17 desired solubilization properties to the mieellar dispersion.
18 The following examples are presented to teaeh speeific
19 embodiments of the invention. Unless otherwise speeified,
all pereents are based on volume and measurements are made
21 at 22-23C.
22 EXAMPLE I
23 A micellar dispersion composition is obtained by
24 mixing lO% of an ammonium petroleum sulfonate having an
average equivalent weight of about 440 and 61 weight pereent
26 active sulfonate, 40% of a crude oil having a viseosity of
27 7-9 ep. and 37 API gravity, 50% of water whieh contains
28 3900 ppm of ammonium sulfate and 400 ppm of other dissolved
Z9 solids. The total water concentration in the micellar
dispersion mixture is 54.5%, this ineludes water from the
31 petroleum sulfonate. Figure l shows the interaction between
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~049926
1 the cosurfactant and electrolyte concentrations on the phase
2 behavior of this composition. The electrolyte concentra-
3 tions shown on the abscissa of Figure l includes only salts
added to the water used to make up the micellar dispersion
S composition but do not include the 3900 ppm of ammonium
6 sulfate concentration. This graph shows that an increase in
7 electrolyte concentration of the connate water causes a
8 decrease in the n-pentanol.concentration, i.e. as the salinity
9 of the connate water increases, the concentration of an
oleophilic cosurfactant decreases in order to achieve a single
11 phase system.
12 EXAMPLE II
13 Micellar dispersion compositions containing 10% of an
14 ammonium petroleum sulfonate and 40% of a crude oil having a
lS viscosity of 7 cp. and 50~ water containing electrolyte
16 concentrations defined'in the abscissa in Figure 2, are
17 titrated with n-amyl alcohol at different electrolyte concen-
18 trations--the minimum viscosity of each micellar dispersion
19 ,as a function of cosurfactant concentration is determined.
The cosurfactant concentration at the minimum viscosity is
21 plotted in Figure 2. The petroleum sulfonate in the dispersions
represented by the inverted and upright triangles have an
average equivalent weight of about 410-420 and the sulfonates
24 ~represented by the circular and square data points have an
average equivalent weight of about 430-440. This figure
26 illustrates that as the salinity of the water increases, the
27 micellar dispersion requires less of the oleophilic cosurfactant.
28 It is not intended that the above examples limit the
29 invention. Rather, it is intended that all equivalents
obvious to those skilled in the art be incorporated within
the scope of the invention as defined within the speci-
fication and appended claims.
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