Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
12,534-1
DESCRIPTION OF THE DISCLOSURE
This invention relates to aqueous solutions
containing crosslinked hydroxyethyl carboxyethyl cellu-
lose in which the crosslinkages are achieved through
polyvalent metals as derived from polyvalent metals in
the form of inorganic or organic acid salts, hydroxides
or oxides.
Hydroxyethyl carboxyethyl cellulose polymers are
known materials, see U. S. Patent 3,829,415, example No. 22
and suitably employable as hydrophilic colloids which possess
suspending, thickening, stabilizing, and film-
possess suspending, thickening, stabilizing, and film-
forming properties. As a general class they are cited as
useful as thickening agents in textile printing pastes,
latex dispersions, and in oil well drilling muds, see
col. 7, lines 42-48 of U. S. Patent 2,618,635.
Fracturing is defined as a method of stimulat-
ing production from an underground formation of low
permeability by inducing fractures and fissures in the
formation and forcing the strata apart. In a typical
"oil patch" fracture, sand is mixed into a thickened
brine solution and pumped downhole under high pressures.
When the fluid pressure exceeds the formation strength,
i.e., the cohesive resistance of the formation to with-
stand the pressure applied, fractures occur which become
filled with the sand-containing fluid. When the applied
pressure is relieved, the sand acts as a prop to support
the structural integrity of the fracture.
Water soluble polymers such as hydroxyethyl
cellulose have been employed in hydraulic or fluid
"~
~ ~,, I;
~ 3Z~ 12,534-1
fracturing of subterranean formations. However, their
employment as the sole viscosifier for this purpose is
quite limited owing to the large temperature coefficient
of viscosity of aqueous hydroxyethyl cellulose thickened
solutions. As such solutions are injected into a well
to a subterranean formation, the increased temperature
of the formation can cause the fluid to lose viscosity
and drop out the sand before it can be deployed in propp-
ing open the formation fractures. To overcome this effect,
it is necessary to alter the chemical ingredients utilized
for viscosification. Such alteration includes the
substitution of crosslinkable thickeners such as modified
guar gum (e.g. hydroxypropyguar gum) or hydroxyethyl
carboxymethyl cellulose. The thickener is dissolved
in, e.g., brine, crosslinker is added, and with the
sand included, the solution is pumped down the hole into
the formation. This technique is characterized in a
number of patents. U. S. Patent No. 3,898,165 describec
the use of hydroxyethyl carboxymethyl cellulose in
fracturing fluids. U, S. Patent No. 3,845,822 describes
plugging and sealing of fractures using primarily
carboxymethyl cellulose, a Cr+6 crosslinker and a
reducing compound suitable for reducing the chromium
compound to a lower valence state such as Cr+3
U. S. Patent No. 3,760,881 enhances the higher tempera-
ture viscosity retention of a fluid by crosslinking a
hydroxyethyl carboxymethyl cellulose thickener with
quaternary ammonium comyounds. U. S. Patent No. 3,926,258
modifies the thickening system of U. S. Pstent No. 3,845,822
by adding a complexing agent such as citric acid to the
;
~ 8 1~,53~-1
formulation. U. S. Patent No. 3,978,928 uses the gel
8~stem of U. S. Patents Nos. 3,845,822 and 3,926,258 for
controlling sand formation restriction at the bore hole.
Increasing the viscosity of a thickening
agent ~art~cularly carboxymethyl cellulose) utilized
~n aqueous solution for recovery of oil is described
in U. S. Patent No. 3,800,872. U. S. Patent No. 4,035,195
descri~es crosslinking of carboxymethyl hydroxyethyl
cellulose with polyvalent metal ions. In some respects,
the disclosure of this patent is similar to that of
U. S. Patent No. 3,926,258, supra.
U. S. Patent ~o. 3,727,687 utilizes the thicken-
ing system of U. S. Patent No. 3,845,822 in secondary oil
recovery and in drilling fluids used in drilling of oil
~ells, gas wells, etc. U. S. Patent ~o. 3,208,524
describes crosslinking polysaccharide thickening agents
~ith polyvalent crosslinking agents. Such a system is
utilized in plugging lost circulation zones and other
highly porous strata.
U. S. Patent No. 3,804,174 describes oil well
cementing using a thixotropic cellulosic solution
; achieved by crosslinking hydroxyethyl cellulose with
~irconium chloride and the patent mentions a number of
other cellulosic thickeners.
The process of this invention, indeed the composi-
tions employed in the process of this invention, provides
a number of unexpected but real advantages. It has been
determined that crosslinked hydroxyethyl carboxyethyl
cellulose requires significantly less crosslinking
polyvalent metal ion in order to give the same viscosity
12,534-1
increase that can be obtained with hydroxyethyl carboxymethyl
cellulose. Not only is this an economic advantage wlth
respect to the manufacture of a thickened system which has
good high temperature viscosity retention even at high
tem~eratures of a deeply situated subterranean strata, but it
also provides for less metal contamination in the aqueous
media thereby decreasing environmental concerns associated
~ith the presence of such polyvalent metal ions. In
addition, the aqueous solutions of hydroxyethyl carboxy-
ethyl cellulose in fresh water or brine are clearer thansolutions of hydroxyethyl carboxymethyl cellulose in
similar solvents. It has been noted that aqueous solu-
tions containing commercial hydroxyethyl carboxymethyl
cellulose possess haze an~ such haze has been found to
plug a coarsely porous material ,ndicating the capability
of the insoluble components which form the haze to plug
the subterranean formation walls thereby reducing the
passage of oil to the borehole.
The aqueous compositions of this invention
find enhanced utility as water flow diversion agents, and
as thickeners in the manufacture of drilling muds, and
completion and workover fluids. In addition, compositions
of this invention are easily obtained without the necessity
of complex oxidizing and reducing agents in order to effect
the appropriate crosslinking.
The compositions of this invention comprise an
aqueous media which contains from about .01 to about 5
~eight percent thereof of a hydroxyethyl carboxyethyl
cellulose which has a M.S. (i.e., molar substitution) of
hydroxyethyl from about 1.4 to about 2.6 and a D.S.
(i.e., degree of substitution) of carboxyethyl groups
~ 8 12,534-~
ranging from about 0.25 to about 0.6. The aqueous
solution can be fresh water or a salt containing aqueous
solution ranging from a dilute aqueous ~alt ~olution to
8 saturated aqueous salt solu~ion ~uch as a saturated
brlne.
The polyvalent metal crosslinker i8 de~ ed
from polyvalent metals in the form of inorganic or
organic acid salts, hydroxides and oxides, and mixtures
thereof, and include polyvalent metals from Group IIA,
IIIB, IVB, VB, VIB, VIIB, VIII, IB, IIB, IIIA and metals
of Group IVA and VA (excluding non-metals such as carbon,
silicon, nitrogen, phosphorous and arsenic). Particularly
preferred are the following polyvalent metals: Be, Mg, Al,
Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y,
Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Ba, Ta, Hf,
Ir, Re, Pt, Au, and the like. The periodic table
referred to above is taken from Lange's Handbook of
Chemistry, 10th edition, published by McGraw-Hill, 1967.
In characterizing the terms M.S. and D.S.,
reference is made to the definition of those terms as
recited in U. S. Patent No. 3,284,353, see col. 1, lines
69-72, to col. 2, lines 1 and 2 and the description at
col. 3, lines 28-36 of U. S. Patent No. 4,035,195.
In characterizing the above mentioned hydroxy-
ethyl carboxyethyl cellulose it is to be understood that
such materials are provided in their alkali metal salt
form, particularly as the sodium carboxylate form, see
U. S. Patent No. 3,845,822, at col. 4, lines 49-54.
The amount of the polyvalent metal which is
empolyed in making the aqueous solution of this invention
.
l~V3Z~3
12, 534-
ranges from about .01 to about 1.5 moles of the metal for
eaeh mole of carboxy present in the hydroxyethyl carboxy-
ethyl cellulose, preferably from about .01 moles to
about 1.05 for each mole of carboxy in the hydroxyethyl
carboxyethyl cellulose.
As stated previously, the polyvalent metal is
ut~lized for the purposes of crosslinking the hydroxy-
ethyl carboxyethyl cellulose in the inorganic or
organic acid salt form, or the hydroxide form, or the
oxide form, or mixtures thereof. For example, the
metal can be in the form of its chloride salt, sulfate
salt, perchlorate salt, iodide salt, bromide salt, per-
manganate salt, hydrogen peroxide salt, nitrate salt,
acetate salt, citrate salt, propionate salt, butanoate
salt, octanoate salt, benzoate salt, monochloroacetate
salt, and the like.
In the preferred embodiment of this invention,
the polyvalent metal is provided in combination with
the hydroxyethyl carboxyethyl cellulose in an already
stabilized form, preferably from an aqueous solution.
In those cases where a metal is in a typically insoluble
oxide form, it is desirable that it be treated with,
for example, caustic sufficiently to provide enough
solubility for use herein but not too much so as to
alter the total oxide structure. After the poly~alent
metal is rendered soluble, a solution of i~ is combined
with the hydroxyethyl carboxyethyl cellulose in the
prescribed proportions in order to produce compositions
suitable for the purposes of the present invention.
The hydroxyethyl carboxyethyl cellulose
suitable for the practice of the present invention and
12,534
having the prescribed M.S. and D.S., is produced by
methods conventional in the art. For example, cellulose
flock can be slurried in an alcohol water diluent such
as an isopropyl alcoholtwater diluent and t~e reactîon
system is purged to low oxygen levels with nitrogen. An
aqueous caustic solution is added to prepare a homogeneous
alkali cellulose. Ethylene oxide is added and the
temperature is increased to a cookout temperature which
is held until all the ethylene oxide is consumed. The
alkali content is adjusted as necessary and acrylamide
is added in a convenient manner. The temperature is
held until no acrylamide remains. The slurry is cooled
and acidified with about 10 to 15% excess acid. The
product is isolated by filtration and purified by
multiple washings with isopropyl alcohol/water mixture.
The following is h more specific illustration
of the manufacture of hydroxyethyl carboxyethyl cellu'ose
suitable for use in this invention:
EXAMPLE 1
Ten grams of cotton linters were slurried into
150 g of 12.5 weight percent aqueous isopropyl alcohol
and the reactor was nitrogen-purged for one-half hour.
A 22% weight percent aqueous sodium hydroxide solution
(15.9 g~ was added followed by one-half hour stirring.
Ethylene oxide (9.4 g) was added, the temperature was
increased to 75C over one hour and then held for 45 minutes.
A 14.5 g portion of a 28.6 weight percent so~ution of
acrylamide in isopropyl alcohol-water was added and the
mixture was stirred for two hours at 75C. The mixture
was acidified with 6 g of acetic acid and cooled to room
~ ~ 4U ~Z ~ 12,534-1
temperature. The solid was filtered, washed four times
with hot 12.5 weight percent aqueous isopropyl alcohol,
and dried. The product analyzed as having a M.S. of 1.47
and a D.S. of 0.31 and dissolved readily in water to give a
clear, viscous solution.
Another illustration for making hydroxyethyl
carboxyethyl cellulose useful in the practice of this
invention is the following:
EXAMPLE 2
Following the procedure of Example 1, 16 g dry
cotton linters and 240 g 12.5 weight percent aqueous
isopropyl alcohol were charged to the reactor. The
reactor was nitrogen-purged for one-half hour and
25.45 g of 22 weight percent sodium hydroxide was
added. After one-half hour stirring, the ethylene
oxide (25.20 g) was added, the mlxture was heated
to 75~C over one hour and the temperature was held
one additional hour. A second 22 weight percent
caustic charge of 1.75 g was made, 1~.~ g of 50
weight percent aqueous acrylamide was added, and
the slurry was reacted for two hours. The mixture was
cooled and acidified with 10.4 g glacial acetic acid.
The product was washed four times with 12.5 weight
percent aqueous isopropyl alcohol and dried. The
product analyzed at 2.21 M.S. and 0.30 D.S. and
gave a clear, viscous solution in water.
In Table I below, are designated a series of
cellulosic compositions A through K with the analysis
of their M.S. and D.S. Examples A through J inclusive
are each hydroxyethyl carboxyethyl cellulose~ The
12,534-1
product designated K is HECMC~ which is a commercial
hydroxyethyl carboxymethyl cellulose:
TABLE I
Product Analysis
Designation M S. _D S.
A 1.47 0.31
B 1.43 0.39
C 1.36 0.48
D 1.96 0.29
E 2.01 0.39
F 1.60 0.36
G 2.10 0.48
H 2.43 0.26
I 2.30 0.33
J 2.24 0.42
K (HECMC) 2.48 0.37
EXAMPLE 3
Four one-quart wide-mouth bottles were
charged with 700 ml of tap water and 3.70 g of the
hydroxyethyl carboxyethyl cellulose designated A in
Table I above was added 810wly to each with agitation.
After the polymer had completely dissolved the solu-
tions had an apparent viscosity, ~V, of 37.5 to 39.5 cps
as measured on the Fann Model 35A viscometer at room
temperature (about 23C). To the individual solutions
was added varying amounts of 2.5 weight percent CrC13 6H20
in water. The viscosity of the solutions vs. time was
determined. The data are:
Solution 1 2 3 4
g 2.5% CrC13'6H20 solution added 1.65 2.2 3.3 6.6
Initial Viscosity 39.5 39 37.538.5
15 min. 46.5 52.5 66~150
45 min. 58 73 ~150 >150
75 min. 64 95.5~ 150 ~ 150
Overnight ~150 >150 ~150 > 150
Thus, it ~as shown that hydroxyethyl carboxy-
ethyl cellulose can be crosslinked and the degree and
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~4(~3~8
~2,534-1
rate of crosslink can be varied by the concentration of
trivalent crosslinking ion. This is indicated by the
~ncrease in viscosity occurring with increasing concen-
trations of the Cr crosslinker.
EXAMPLE 4
By an analogous procedure to Example 3, the
1~ hydroxye~hyl carboxyethyl cellulose samples and the
hydroxyethyl carboxymethyl cellulose depicted in Table
I above were evaluated. Each cellulosic polymer
dissolved in tap water at a concentration (based on
contained resin~ equivalent to 2.0 lb./42 gal. barrel
hydroxyethyl carboxymethyl cellulose (as received).
The samples were also evaluated in saturated
~aCl brine with CrC13 6H2O and in 2 percent KCl ~rine
with A12(SO4)3;18H2O.
During these studies, it was observed that
the hydroxyethyl carboxyethyl cellulose solutions
generally had better clarity than those of hydroxyethyl
carboxymethyl cellulose and the observations about
clarity which is an indication of lower formation damage
and the crosslinkability of hydroxyethyl carboxyethyl
cellulose with less trivalent ions (mole ratio bases)
were noted.
EXAMPLE 5
In this example, the followin~ hydroxyethyl
carboxyethyl cellulose (desi~nated L, M, N) was
compared to the same hydroxyethyl carboxymethyl
cellulose (designated K, see Table I also):
28
12,534-1
TABLE II
-
Percent Percent
Designation M S. D S. Volatiles 5alt, From Ash
L 2.21 0.30 7.01 2.52
M 2.47 0.42 1.82 2.42
N 2.27 0.50 2.83 3.54
K 2.48 0.37 6.53 3.90
The aqueous solutions were made-up at 2.00
lb/bbl (4.0 grams/700 ml) hydroxyethyl carboxymethyl
cellulose, i.e., [4.0 x (1.0-(.0653 + .0390))] = 3.58
grams polymer as control. The same concentration of
contained polymer was maintained for the HECEC samples/
700 ml.
L [3.58 . (1.0-(.0701 + .0252))] = 3.96 gms
M [3.58 . (1.0-(.0182 + .0242))] = 3.74 gms
N [3.58 . ~1.0-(.0283 + .0354))] = 3.82 gms
K [4.0 x (1.0-(.0653 + .0390))] = 3.58 gms
By a procedure analogous to Example 1, the
crosslinkability of the three samples was compared
to HECMC in 2 percent KCl solution using A12S04 as
crosslinker. The results are:
HECEC as used herein means hydroxyethyl carboxyethyl
cellulose.
HECMC as used herein means hydroxyethyl carboxymethyl
cellulose, i.e., product designated K in Tables I and
II.
- 12 -
3;28 1'~, 534-1
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o O ~ ~D O C~
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oo~ Xr~
~D ~ C~O ~D 00 0
o C~
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~ ~ ~ I ~
CO ~o ~
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O ~n ~o O
h ~ ~ h ~: C`l
'~ O O `-- ^
a~ P
¢ :~ ~ ¢ :~C
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~1 rl ~ r~
U~ o . O ~ C~l O
O O~-r~-r r~ 1` :~ 00 U~-r~-r~-rl
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3Z8 12, 534-l
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_, ~ oo o ~ I~ o
,1 C~ o o o
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12,534-l
The viscosity in solutions containing the
higher concentrations of A12(S04~3 broke due to syneresis.
The unexpected crosslinkability of the HECEC
samples with less trivalent Al~ll compared to HECMC was
verified. HECEC crosslinks to the same viscosity
increase with less tri~alent Al ion than HEC~C. The
lower initial viscosity of solutions of Product M was
apparently due to air ~n the reactor during the reaction
Cpreparation) which lead to a slight reduction in mole-
cular weight. Product M is near the M.S. -D.S. composition
of the HECMC tested.
EXAMPLE 6
To confirm the observation of haze in the
HECMC solutions compared to the HECECts and the tendency
towards formation damage, the following was run:
Each of the polymers (1500 ppm as received)
L, M and N of Example 5 and two lots of commercial
HECMC, one being Product K above, were dissolved in a
3% NaCl 0.3% CaC12, by weight, brine. After standing
overnight they were filtered through a coarse sintered
glass filter to remove any large insoluble matter and
1,000 ml filtered under pressure (40 psig) through 0.8 micron
cellulose acetate/cellulose nitrate millipore filter
paper ~Millipore (TM~ M WP04700). The initial solution
viscosities were:
Product Solution
Designation Viscosity (1
L 6.8 cps
M 4.9 cps
N 9.6 cps
HECMC K 6.2 cps
HECMC O 6.2 cps
(1) Viscosity measured on LVT Brookfield viscometer with
UL attachment at 6 RPM at ambient temperature
(about 23C).
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12,534-1
The three HECEC solutions passed through the
sintered glass prefilter with ease. HECMC Product K
passed the prefilter satisfactorily but the HECMC
Product O was difficult to pass through the prefilter.
The prefiltered samples (1,000 ml) were then
pressure filtered through the 0.8 micron filter and the
volume passing vs. time were noted. The data are:
Z8 12, 534-l
C ~o
I o
o _,
~ c~ o o~ o ~
t,
I o~
oooooooooo
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12,534-1
These data show the improved filterability of
HECEC over HECMC which is indicative of lower formation
damage.
EXAMPLE 7
Two grams of Hydroxyethylcarboxyethyl Cellulose
(MS~2~4 DSz0.31) were dissolved in 350 ml of 2% KCl brine
by being mixed in a Waring blender for 15 seconds followed
by a gentle stirring in a wide-mouth bottle equipped with
a paddle stirrer for 10 m~nutes. The viscosity of the
resultant solution as measured on a Fann Model 35A vis-
cometer was 41.25 cps (indicated by a dial deflection of
82.5 at 600 ppm).
One-half (175 ml) of the solution was then
removed from the bottle and 0.8974 grams of 10%
A12(SO4)3 18H2O crosslinking solution were added to the
HECEC solution in the bottle. After one minute, the
gelled mixture was transferred to the Waring blender and
stirred at low speed for about two minutes to make it
uniform. The gelled solution was then transferred to a
calibrated Model 50C Fann viscometer and the sample heated
at 300 psig pressure. The viscosity as indicated by dial
deflection was measured at 100 and 200F. The data are
summarized in Table I below.
EXAMPLE 8
By a procedure similar to that described in
Example 7, 2.0 grams of the HECEC polymer described above
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12,534-l
were dissolved in 350 ml of 2% KCl. The viscosity of the
solution as measured on a Fann Model 35A viscometer was
39.75 cps ~indicated by a dial deflection of 79.5 at
6Q0 rpm). 175 ml of the solution were crosslinked with
0.7614 grams of 10% A12(SO4)3'18H2O and the viscosity-
temperature relationship then measured on the model 50C
Fann viscometer. The data are summarized in Table I below.
EXAMpTF 9
By a procedure similar to that described in
Example 7, 2.0 grams of commercial hydroxyethylcarboxy-
methyl cellulose (MS~2.48, DSs0.37) were dissolved in
350 ml of 2.0% KCl brine. The viscosity of the resultant
solution was 30 cps (indicated by a dial deflection of
60 at 600 rpm on a model 35A Fann viscometer).
One-half of the sample (175 ml) was then re-
moved and 0.9005 grams of 10% A12(SO4)3'18H2O crosslinkin~
solution added to the remaining HECMC solution. The
viscosity of the resultant gelled solution was measured
at 100 and 200F. The data are summarized in Table I.
TABLE I
Viscosity of Crosslinked
Initial Solution Solution at Elevated
Example Polymer Viscosity, cps_ ~ Temp.( )
100F 200F
7 HECEC 41.25 227 66
8 HECEC 39.75 120 54
9 HECMC 30 82 10
( ) Data reported are dial deflection units - higher
numbers indicate higher viscosity.
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12,53~-1
From the data of Table I ~t i8 apparent ~hat ~he
solutions of HECEC had a slightly higher viscosity before
crosslinking and that such viscosity was maintained after
crosslinking and at elevated temperatures. This is
significant in maintaining a constant fluid viscosity
during fracturing operations.
XAMPLE 10
This example demonstrates the ability to
breakdown the viscosity of the aqueous cros~linked
cellulosic composition of this invention to facilitate
production of the well.
A 300 cc. sample of a hydroxyethyl carboxyethyl
cellulose, essentially the same AS characterized in Example
3 above except it had been previously crosslinked with
0.523 g of an aqueous 2.5 weight percent chromium chloride
solution, was employed in this example. The viscosity
of the crosslinked solid gelled structure was well
over 300 on the Fann Model 35A viscometer dial at
600 rpm. A sample of the crossl$nked structure was
placed on a LightningTM mixer and the breaker of the
composition was added with ~gitation. The breaker
was a pre-mixed composition containing 24 drops
(1.77 g~ of 2 weight percent HCl, 0.88 g ammonium per-
sulfate and 0.72 g ferrous sulfate. The viscosity dropped
immediately and within a matter of minutes the Fann dial
reading dropped to 20 (at 600 RPM's) and finally
dropped to 3.5 (at 600 rpm) free of gels. The resulting
solution was a watery fluid after standing overnight.
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~ 8 12,534-1
The same effect can be achieved with a variety of
acid, bases and other redox systems which are capable o
displacing the bond between the hydroxyethyl carboxyethyl
cellulose and the polyvalent metal ion. Suitable viscosity
breaker materials include a variety of acids and bases, a
variety of alkali and alkaline earth metal salts or
materials which will eerve to reduce the valence of the
metal while at the same time effecting oxidation of the
cellulose material. Metal salts combined with mineral
acids constitute an effective breaker composition.
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