Note: Descriptions are shown in the official language in which they were submitted.
1
CORROSION INHIBITORS FOR DRILLING FLUID BRINES
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is broadly concerned with improved anti-corrosion
products for use
with heavy brines employed in the petroleum industry during well drilling.
More particularly,
the invention is concerned with such products and corresponding methods
wherein corrosion
inhibitors comprising amounts of a phosphonate or salts thereof, and gluconic
acid or salts
thereof, are introduced into the brines. The combined ingredients of the
inhibitors are
synergistically effective in reducing corrosion rates attributable to the
brines.
Description of the Prior Art
Calcium chloride and calcium nitrate brines are used in establishing and
maintaining
petroleum (i.e., oil and gas) wells. For example, calcium chloride brines are
used in drilling
muds to cool and lubricate well bits and to remove cuttings from the hole. The
brines help
maintain the consistency of the drilling muds and add density thereto, to
better enable the muds
to overcome formation pressures and thereby oil, gas, and water in place. Such
brines also
inhibit clay and shale hydration and add needed weight to the muds.
Brines are also used as completion fluids just before the producing formation
is reached,
to flush the hole clean of solids so that the casing can be cemented in place.
As clear,
substantially solid-free brines, calcium chloride and calcium nitrate brines
are ideal as
completion fluids.
Once a well casing is cemented in place, smaller diameter tubing is inserted
in the casing,
which makes the flow of oil or gas more efficient and can be replaced if plugs
develop. Tubing
Date recue / Date received 2021-11-01
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in used with packer fluid that keeps the well fluids away from the casing to
minimize corrosion.
Calcium chloride and calcium nitrate brines are used in the packing injected
into the annular
space between the tubing and the casing in order to maintain pressure levels.
Finally, these brines can also be used as workover fluids, by flushing wells
free of solids
before they are repaired, or before reworking a well that has been idle.
Notwithstanding the multiple uses of these brines, problems remain. A
principal
drawback is the fact that the brines tend to be highly corrosive to downhole
equipment surfaces,
causing pitting and erosion thereof often with the result that the equipment
in question must be
repaired or replaced at frequent intervals.
Attempts have been made to control the corrosive activity of well brines, see
e.g., US
Patent No. 4,784,778. This patent teaches that particular thio compounds and
aldose group
antioxidants may be used in the context of zinc halide-based, high density
fluids. US Patent No.
5,171,460 describes scale inhibitors for use with calcium and similar brines,
comprising a
phosphonomethylated oxyalkyleneamine. Other background references include US
Patents Nos.
4,061,589, 4,279,768, 4,303,568, 4,849,171, 4,869,827, 5,330,683, 5,589,106,
5,023,011, and
7,172,677, and PCT Publications Nos. WO 86/04634 and WO 2008/084503. However,
no fully
satisfactory anti-corrosion system for calcium chloride and calcium nitrate
brines has heretofore
been developed.
SUMMARY OF THE INVENTION
The present invention overcomes the problems outlined above, and provides
improved,
synergistic anti-corrosion systems for use with calcium chloride or calcium
nitrate brines
employed in the oil and gas industry. Broadly speaking, the invention provides
methods of
inhibiting corrosion of metal surfaces in petroleum well equipment when using
such brines,
wherein a selected brine is injected into the well and a corrosion inhibitor
is mixed therewith; the
inhibitor includes respective amounts of a phosphonate or salts thereof, and
gluconic acid or salts
thereof. Particularly preferred phosphates are the amine polyphosphoriates.
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The invention also provides corrosion inhibitors for brines selected from the
group
consisting of calcium chloride or calcium nitrate brines, consisting
essentially of a phosphonate
or salts thereof; and gluconic acid or salts thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a graph of the anti-corrosion results of the Example 1 test;
Fig. 2 is a graph of the anti-corrosion results of the Example 2 test;
Fig. 3 is a graph of the anti-corrosion results of the Example 3 test;
Fig. 4 is a graph of the anti-corrosion results of the Example 4 test;
Fig. 5 is a graph of the anti-corrosion results of the Example 5 test;
Fig. 6 is a graph of the anti-corrosion results of the Example 6 test;
Fig. 7 is a graph of the anti-corrosion results of the Example 7 test;
Fig. 8 is a graph of the anti-corrosion results of the Example 8 test;
Fig. 9 is a graph of the anti-corrosion results of the Example 9 test;
Fig. 10 is a graph of the anti-corrosion results of the Example 10 test;
Fig. 11 is a graph of the anti-corrosion results of the Example 11 test;
Fig. 12 is a graph of the anti-corrosion results of the Example 12 test;
Fig. 13 is a graph of the anti-corrosion results of the Example 13 test;
Fig. 14 is a graph of the anti-corrosion results of the Example 14 test;
Fig. 15 is a graph of the anti-corrosion results of the Example 15 test; and
Fig. 16 is a graph of the anti-corrosion results of the Example 16 test.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention provides synergistic anti-corrosion inhibitors for use
with drilling
fluid brines, wherein the inhibitors generally include a phosphonate and
gluconic acid and/or a
precursor of gluconic acid, or corresponding gluconate salts.
Brines useful in the invention are dispersions or solutions containing calcium
chloride
and/or calcium nitrate. Generally, the brines should contain from about 25-40%
by weight
calcium chloride, and more preferably from about 28-34% by weight. These
brines should also
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have a density of from about 1000 kg/m3 to saturation, and more preferably
from about 1200
kg/m3 to saturation. Saturation points are dependent upon the ionic species
present in the brines,
and potentially well temperatures. The specific gravities of the brines are
normally in the range
of from about 1.2-1.45 at 15.6 C. The pH meter-measured levels of pH of the
brines should be
from about 8-13, more preferably from about 9.5-11. The ionic strength of the
brines suppresses
hydronium ion activity, which is what the pH meter electrode measures. As
such, the measured
pH values may not be the "true" pH, but rather is an artifact of the pH meter
apparatus. In this
connection, pH measured manually by pH strips usually does not correlate with
the value
measured using a pH meter in these brines.
Suitable brines typically have impurities such as magnesium, sodium, and
potassium ion,
as well as the corresponding chloride salts thereof. Calcium ion is typically
present at a level of
from about 8-14% by weight, whereas magnesium chloride is present at a level
of from about 2-
6% by weight. The other impurities are at minor levels in the brines.
Particularly preferred
brines are the commercially available mined calcium chloride brines produced
in Alberta,
Canada, and especially a brine commercialized under the designation Gold Plus
35%, Clear
Brine.
A variety of different effective phosphonates may be used in the invention, so
long as
they appropriate dispersibility in the brines and are effective corrosion
inhibitors.
Advantageously, the phosphonates are dispersible at levels up to about 200,000
ppm in the
brines, and have 2-8 phosphono groups therein, more preferably 2-5 phosphono
groups.
Primary, secondary, and/or tertiary amine phosphonates are generally
preferred, although use of
these phosphonates is not mandatory.
A particularly preferred class of tertiary amine phosphonates have the general
formula
X¨N¨ Y2 1,
where X is selected from the group consisting of alkyl phosphonates of the
formula
0
ii
¨RrP0R3 Ii
OR2
CA 02911576 2015-11-05
alkyl alcohols of the formula
--R4-OH III
alkoxyalcohols of the formula
IV
5 and mixtures thereof; and Y is selected from the group consisting of
alkylphosphonates of the
formula
0
II __________________________________
OR3 V
OR2
and alkylaminediphosphonates of the formula
0
N _______________________________ R10 ¨P __ OR3 VI
OR2
-2
and mixtures thereof, where each respective Ri, and R4 through Rio moiety is
independently
selected from the group consisting of Cl -C6 straight or branched chain alkyl
groups, and each
respective R2 and R3 moiety is independently selected from the group
consisting of H and Cl -C6
straight or branched chain alkyl groups. In each instance, the moieties may be
the same as or
different from other such moieties. Salts of any of the foregoing
phosphonates, and especially
the alkali metal salts, are also usable in the invention.
Specific examples of these preferred tertiary amine phosphonates include
ammonium
phosphonate
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0
ofi
0 OH
OH
/ OH VII
0
AMP Ammonia Phosphonate
DETA phosphonate
0 0
H0,41 OH
HO OH
HO 01I
p
VIII
0'
OH
0
DETA Phosphonate
monoethanolamine phosphonate
0
I 1OH
OH
OH
HOo
MEA Phosphonate
and 2-(aminoethoxy) ethanol phosphonate:
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0
JOH
OH
./1
OH
0
0
2-(2-aminoeth)oxy)ethanol phosphonate
As indicated previously, the phosphonates need not be amine phosphonates. For
example, 1-hydroxyethylidene-1,1-diphosphoric acid Formula XI and salts
thereof can also be
employed.
HO 0
HO\
P HO II
\ X1
OH
0 CH3
HEDP
1-Hydroxy ethylidene-1,1-Diphosphonic acid
Other exemplary non-amine phosphonates include phosphonobutane-1,2,4-
tricarboxylie acid,
and 2-hydroxyphosphoriocarboxylic acid, and salts thereof.
Gluconic acid and the salts thereof, particularly the alkali metal salts, are
used to good
effect in the invention. Precursors of gluconic acid may also be used, e.g.,
gluconolactone,
which yield gluconic acid in aqueous systems. Thus, as used herein, "gluconic
acid and the salts
thereof" shall mean gluconic acid, salts thereof, and precursors of any of the
foregoing.
The corrosion inhibitors of the invention preferably include from about 30-70%
by
weight phosphonate (more preferably from about 40-60% by weight, and most
preferably about
50% by weight), and correspondingly from about 70-30% by weight gluconic acid
or gluconate
(more preferably from about 60-40% by weight, and most preferably about 50% by
weight). The
inhibitors are preferably in the form of aqueous dispersions or solutions
having pH levels of from
about 8-13, more preferably from about 9-12, and most preferably from about 10-
10.5.
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Advantageously, the components of the corrosion inhibitors are present in
synergistically
effective amounts, meaning that the amounts of the phosphonates and the
gluconic acids or
gluconates are in coordinated amounts of each, which in combination give
increased anti-
corrosion activities in excess of the anti-corrosion activities which could be
obtained by
individual use of the respective components; stated otherwise, the coordinated
amounts of the
components give anti-corrosion effects greater than a mere additive effect
obtainable through the
use of the components alone in the same amounts.
In use, the corrosion inhibitors are either directly added to the brines
before injection
thereof, or may be added with other fluids, which ultimately mix with the
brines during use
thereof. The inhibitors should be used at a level to provide from about 10-
10,000 ppm inhibitor
in the brine, more preferably from about 1,000-8,000 ppm, and most preferably
from about
2,000-5,000 ppm. Alternately, the phosphonate or salts thereof; and the
gluconic acid or salts
thereof; may be individually introduced into the well for mixing into the
brine, to provide the
complete corrosion inhibitor in the above-listed amounts.
Examples
The following Examples set forth preferred brine corrosion inhibitor products
and
methods of testing thereof. It is to be understood that these examples are
provided by way of
illustration only, and nothing therein should be taken as a limitation upon
the overall scope of the
invention.
In each of the experiments described below, a Pine Research Instruments
rotating
cylinder electrode (RCE) apparatus equipped with a Gamry potentiostat and
DC105 software
was employed. The electrode material was carbon steel and had a surface area
of 3 cm2, and was
rotated at 700 rpm. Experiments were conducted at ambient pressure and a brine
temperature of
50 C at a solution pH of between 10 and 12. Each test solution contained
approximately 15% by
weight calcium chloride in deionized water with 5 mL ethanolarnine per liter.
Corrosion rates were monitored by Linear Polarization Resistance (LPR)
measurements
every 5 minutes for a period of approximately 30 hours. The test inhibitors
were added at
approximately 6 hours at specific concentrations and pH levels.
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Example 1
In this Example, the calcium chloride solution had a pH of 10.4, and 5 mL
(5,000 ppm)
of a test inhibitor containing 50g HEDP (1-hydroxyethane 1,1 diphosphonic
acid, WCS 3730,
commercialized by Jacam Chemical Company 2013, LLC) and 50g gluconic acid in
50g
deionized water. Sufficient 50% sodium hydroxide was added to elevate the pH
of the inhibitor
to 10. As illustrated in Fig. 1, the corrosion rate decreased precipitously
after addition of the
inhibitor and was maintained at a low level throughout the remainder of the
test.
Example 2
In this Example, the calcium chloride solution had a pH of 10.4, and 5 mL
(5,000 ppm)
of a test inhibitor containing 50g DETA phosphonate (JC 3600 W, commercialized
by Jacam
Chemical Company 2013, LLC) and 50g gluconic acid in 50g deionized water.
Sufficient 50%
sodium hydroxide was added to elevate the pH of the inhibitor to 10. As
illustrated in Fig. 2, the
corrosion rate decreased precipitously after addition of the inhibitor and was
maintained at a low
level throughout the remainder of the test.
Example 3
In this Example, the calcium chloride solution had a pH of 10.4, and 5 mL
(5,000 ppm)
of a test inhibitor containing 50g ATMF (aminotrismethylene phosphonic acid,
commercialized
by Jacam Chemical Company 2013, LLC) and 50g gluconic acid in 50g deionized
water.
Sufficient 50% sodium hydroxide was added to elevate the pH of the inhibitor
to 10. As
illustrated in Fig. 3, the corrosion rate decreased precipitously after
addition of the inhibitor and
was maintained at a low level throughout the remainder of the test.
Example 4
In this Example, the calcium chloride solution had a pH of 10.4, and 2 mL
(2,000 ppm)
of a test inhibitor containing 50g methanolamine phosphonate (50% active), WCS
3830,
commercialized by Jacam Chemical Company 2013, LLC, and 50g gluconic acid in
50g
deionized water. Sufficient 50% sodium hydroxide was added to elevate the pH
of the inhibitor
to 10. As illustrated in Fig. 4, the corrosion rate decreased precipitously
after addition of the
inhibitor and was maintained at a low level throughout the remainder of the
test.
CA 02911576 2015-11-05
Example 5
In this Example, the calcium chloride solution had a pH of 10.4, and 2 mL
(2,000 ppm)
of a test inhibitor containing 50g 2-(aminoethoxy)ethanol phosphonate (50%
active), WCS 3930,
commercialized by Jacam Chemical Company 2013, LLC, and 50g gluconic acid in
50g
5 deionized water. Sufficient 50% sodium hydroxide was added to elevate the
pH of the inhibitor
to 10. As illustrated in Fig. 5, the corrosion rate decreased precipitously
after addition of the
inhibitor and was maintained at a low level throughout the remainder of the
test.
Example 6
In this Example, the calcium chloride solution had a pH of 11, and 5 mL (5,000
ppm) of a
10 test inhibitor containing 50g WCS 3830 (50% active) and 50g gluconic
acid in 50g deionized
water. Sufficient 50% sodium hydroxide was added to elevate the pH of the
inhibitor to 10. As
illustrated in Fig. 6, the corrosion rate decreased precipitously after
addition of the inhibitor and
was maintained at a low level throughout the remainder of the test.
Example 7
In this Example, the calcium chloride solution had a pH of 11, and 5 mL (5,000
ppm) of a
test inhibitor containing 50g WCS 3930 (50% active) and 50g gluconic acid in
50g deionized
water. Sufficient 50% sodium hydroxide was added to elevate the pH of the
inhibitor to 10. As
illustrated in Fig. 7, the corrosion rate decreased precipitously after
addition of the inhibitor and
was maintained at a low level throughout the remainder of the test.
Example 8
In this Example, the calcium chloride solution had a pH of 10.5, and 2 mL
(2,000 ppm)
of a test inhibitor containing 50g gluconic acid in 50g deionized water.
Sufficient 50% sodium
hydroxide was added to elevate the pH of the inhibitor to 10.01. As
illustrated in Fig. 8, the
addition of gluconic acid alone had no perceptible effect on the corrosion
rate.
Example 9
In this Example, the calcium chloride solution had a pH of 10.5, and 5 mL
(5,000 ppm)
of a test inhibitor containing 50g gluconic acid in 50g deionized water.
Sufficient 50% sodium
hydroxide was added to elevate the pH of the inhibitor to 10.01. As
illustrated in Fig. 9, the
addition of gluconic acid alone had no perceptible effect on the corrosion
rate.
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Example 10
In this Example, the calcium chloride solution had a pH of 12, and 5 mL (5,000
ppm) of a
test inhibitor containing 50g WCS 3830 (25% active) in 50g deionized water.
Sufficient 50%
sodium hydroxide was added to elevate the pH of the inhibitor to 10.01. As
illustrated in Fig. 10,
the addition of gluconic acid alone had no perceptible effect on the corrosion
rate.
Example 11
In this Example, the calcium chloride solution had a pH of 12, and 5 mL (5,000
ppm) of a
test inhibitor containing 50g WCS 3930 (25% active) in 50g deionized water.
Sufficient 50%
sodium hydroxide was added to elevate the pH of the inhibitor to 10.05. As
illustrated in Fig. 11,
the addition of gluconic acid alone had no perceptible effect on the corrosion
rate.
Example 12
In this Example, the calcium chloride solution had a pH of 10.3, and 2 mL of a
commercially available neutralized amine corrosion inhibitor (V/Cl 1157, a
mixture of
neutralized imidazoline tallow di amine and quaternary amines, pH 4.87,
commercialized by
Jacam Chemical Company 2013, LLC) was added to the brine. As illustrated in
Fig. 12, no
perceptible decrease in corrosion was observed.
Example 13
This Example is identical with Example 12, except that 5 mL of the WCI 1157
product
was added to the brine. This resulted in a slight decrease in corrosion, as
illustrated in Fig. 13.
Example 14
In this Example, the calcium chloride solution had a pH of 10, and 5 mL (5,000
ppm) of a
test inhibitor containing 50g WCS 3730 and 50g gluconolactone in 50g deionized
water.
Sufficient 50% sodium hydroxide was added to elevate the pH of the inhibitor
to 10. As
illustrated in Fig. 14, the corrosion rate decreased precipitously after
addition of the inhibitor and
was maintained at a low level throughout the remainder of the test.
Example 15
In this Example, the calcium chloride solution had a pH of 10, and 2 mL (2,000
ppm) of a
test inhibitor containing 50g WCS 3730 and 50g gluconic acid in 50g deionized
water.
Sufficient 50% sodium hydroxide was added to elevate the pH of the inhibitor
to 10. As
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illustrated in Fig. 15, the corrosion rate decreased precipitously after
addition of the inhibitor and
was maintained at a low level throughout the remainder of the test.
Example 16
This Example is identical to Example 15, except that 5 mL (5,000 ppm) of the
test
inhibitor was used. As illustrated in Fig. 16, the corrosion rate decreased
precipitously after
addition of the inhibitor and was maintained at a low level throughout the
remainder of the test.
As is evident from the foregoing results, the corrosion test utilizing the
individual
ingredients of the products of the invention, namely the selected phosphonate
or gluconic acid
(Examples 8-11) demonstrated no anti-corrosion effects, whereas the products
of the invention
gave very significant results. Thus, the synergistic behavior of the products
of the invention is
concerned. As further illustrated in Examples 12 and 13, use of a conventional
amine corrosion
inhibitor had no significant beneficial effect.
=
