Note: Descriptions are shown in the official language in which they were submitted.
1~75l~8'Y
The invention resides in an aqueous composition,
a method of reducing the surface tension of aqueous liquids
and a method for treating subterranean formations to stimu-
late the flow of fluids therethrough.
S For various reasons it is often desired to lower the
the surface tension of aqueous liquids. For example, by
lowering the surface tension of aqueous liquids, solid
matter can be more easily wet by the liquid. This property
is useful, for example, when treating subterranean for-
mations with various aqueous liquids to stimulate the flow
of petroleum and/or aqueous fluids therefrom. Thus, it is
desirable to, for example, employ acidizing, hydraulic
fracturing, and other aqueous treatment liquids having low
surface tensions.
~ow surface tension values in combination with
the water wetting properties of an aque7ous liquid reduce
the capillary forces in the formation being treated. Re-
duction of the capillary forces in a reservoir results in
a more effective recovery of fluids after the formation
has been treated. The present invention concerns the
discovery of a composition which, when added to an aqueous
liquid, effectively reduces the surface tension thereof
and also increases the watex wetting properties of the
liquid.
Various quaternized perfluoroalkane-sulfonami-
-dopolymethylenealkylamine compounds are known to reduce
the surface tension of neutral, acidic and basic aqueous
solutions even when present in minute amounts (see U.S.
Patent No. 2,759,019). However, these compounds were
17,529-F -1-
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found to become ineffective when the aqueou~ solution in
which they were employed came into contact with earthen
formations. Thus, the use o~ such compounds in liquids
employed to treat, for example, subterranean formations is
limited. The present invention concerns the discovery o~
how to effectively ma~e use of the surface active properties
of such compound in these types of liquids.
The present invention provides an aqueous composition
suitable for use in treating subterranean formations comprising:
A. an aqueous liquid; and dispersed in said
aqueous liquid,
. an effective amount of a per~luorinated surfactant
of the formula
_ ._
/ C~3 +
C8F17S02NHC3H6-N~ CH3 A
I \ CH3
wherein A is Cl , F , I or Br ;
C. a second surfactant blend comprising about the
following percentages by weight, 57 percent polyethylene
glycol monostearate; 19.2 percent sodium di(2-ethylhexyl)-
-sulfosccinate; 3.0 percent di-2-ethylhexyl maleate; 10.0
percent isooctyl alcohol; 4.5 percen~ isopropyl alcohol and
6.2 percent water; and
D. a third surfactant selected from the group
co~sisting of an adduct of a C10-Cl2 alcohol with five moles
of ethylene oxide3 an adduct of trimethyl-l-heptanol with seven
moles of ethylene oxide, and mixtures thereof; the total
amount of said perfluorinated surfactant and other surfactants
being present in said aqueous liquid in an amount ranging
from 0.02 to 0.2 percent by weight of said composition.
The present in~ention also resides in a method of
stimulating the flow of a fluid from a subterranean formation
wherein a portion of the formation is solubilized with an
aqueous acid solution the improvement which comprises:
employing the composition defined above wherein said aqueous
liquid is an acid in which at least a portion o~ said
17,529-F - 2 -
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~L~75~387
subterranean forma-tion is soluble.
The present invention further resides in a method
of stimulating the flow of fluid from a subterranean formation
wherein the Eormation is fractured by introducing an aqueous
fracturing fluid through a borehole and into contact with
said formation under sufficient pressure to fracture the formation,
- the improve~ent which comprises: employing as the fracturing
fluid the composition defined above.
The aqueous liquids comprise acidic, neutral and
alkaline solutions and can be gelled, contain noninterfering
functional additives such as corrosion inhibitors, freeze
point depressants, weighting agents, proppants, alcohols,
and the like.
The combination of the perfluorinated surfactant
and the other surfactants are employed in a combined amount
ranging from 0.02 to 0.2 percent by weight of the aqueous
liquid. The exact amount will depend on the particular
aqueous liquid they are dispersed in. For example, in
conc~ntrat~d acid solutiions, such a~ ~Cl and HF, th~ co~binati~n
~f materials are employed in an amount ranging from
0.1 to 0.2 percent by weight of the aqueous acid
solution. In brines, the combination of compounds is
employed in an amount ranging from 0.02 to 0.1 percent
- by weight of the brine.
The aqueous liquids containing the combination
of surfactants can be employed in many uses wherein low
surface tension properties are desired, e.g., matrix
acidizing, water-base fracturing, fracture-acidizing and
emulsified acids employed in acidizing-fracturing techniquesO
Such liquids are particularly useful for treating subter-
ranean formations to perfect or make more efficient the
recovery
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1075~387
of fluids, e.g., petroleum fluids (oil and gas), water, other gases etc.,
therefrom.
The efficiency of an acidizing solution is greatly increased
by incorporating therein the perfluorinated surfactant B, and the other
identified water wetting surfactants C and D. For example, in acidizing
with HCl solutions, the surface tension of the resulting solution can
be drastically reduced by employing therein from about 0.1 to about 0.2
per cent by weight of the combination of surfactants previously iden-
tified. The acidizing solution is then used in standard acidizing pro-
cedures, i.e. it can be used in standard matrix acidizing process, in
acidizing-fracturing processes and the like. It has been found that
. such acidizing solutions penetrate the formation more easily, thereby
effecting a greater stimulation of the production of fluids. Also,
such solutions are more easily removed from the formation following the
acidlzing treatment.
It has been also discovered that the aqueous solution is
quite effective for acidizing gas producing formations. The use of
aqueous liquids to treat gas producing formations has produced par-
: .
ticular difficulties because aqueous liquids tend to block the intri-
cacies of the formation to the flow of gases. Thus, in many instances,
such solutions have hindered instead of stimulated the flow of gas
from the formation. When fracturing a gas producing formation, it
has been the practice to employ nonaqueous fracturing fluids such as
o ls, C02-methanol
~75~
mixtures and the like. However~ because aqueous liquids
can be considerably less expensive and also are generally
more available than other such fluids, it is desired to
use aqueous liquids if possible. The present discovery
now permits such use4
The individual surfactants can be blended
directly into an aqueous treatment liquid or they can be
premixed and easily blended into a treatment liquid employ-
ing standard equipment employed in fracturing and acidizing
- treatments. The premix may also contain water, mono and/or
polyhydric alcohols, and other functional additive.
One such preblend comprises a mixture containing,
as pàrts by weight, 2397 parts H20; 2397 parts isopropyl
alcohol; 2397 parts of the second surfactant (C) identified
above and 40 parts of the above identified perfluorinated
surfactant wherein A is iodide.
Another ~lend which can be prepar~d and em~loy~
-~n t~e practice of the present invention comprises as parts
by weight, 2502 parts H20; 1965 parts isopropyl alcohol;
2655 parts of the second surfactant (C); 835 parts of the
third surfactants (D) and 40 parts of the above identified
perfluorinated compound wherein A is iodide.
- The above defined blends are employed in an amount
ranging from 2 to 4 gallons per 1000 gallons of an acid, e.g.
hydrochloric acid (3 to 28 per cent strength), hydrochloric-
-hydrofluoric acid mixtures, aqueous fracturing fluids and
other other aqueous fluids to lower the
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surface tension thereof. Higher concentrations are
recommended for matrix acidizing treatments while lower
concentrations can be employed in fracturing treatments.
As indicated the aqueous liquids in which the
combination of surfactants can be successfully employed can
contain other functional additi~res such as thickening
and gelling agents, weighing agents, corrosion inhibitors
and the like. The compatibility of the combination of
surfactants with other functional additives should be ascer-
tained prior to preparing large quantities of such aqueous
liquids.
A preblend was prepared containing, as parts
by weight, 2502 H2O; 1965 isopropyl alcohol; 2655 parts
of a mixture containing as per cent by weight, 17~1 per cent
polyethylene glycol monostearate, 6.7 per cent sodium di(2-
ethylhexyl) sulfonosuccinate, 3.1 per cent isooctyl alcohol,
31.4 per cent water and 10 per cent of an adduct of a
C10-Cl2 alcohol with five moles of ethylene oxide; 836
parts of an adduct of trimethyl-l-heptanol plu5 seven moles
o ethylene oxide, and 40 parts of ~he iodide salt
of the previously defined perfluorinated compound. Aqueous
mixturas were prepared containing an equivalent of 2 gallons
of the pre~lend with 1000 gallons of various liquids.
; The surface tension of the mixtures we~e determined employ-
ing a DuNouy Tensiometer ~he liquids employed, their oriqinal
surface tension, and the resulting surface tension are
set forth in the following Table.
17,529-F -6-
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