Note: Descriptions are shown in the official language in which they were submitted.
BACKGF~OUND OF THE INVENT~ON
3 I. Field ~f the Invention:
The present invention relates to compositions and
6 methods for acidizing subterranean formations in the
7 vicinity of a well bore. More specifically, the
8 invention relates to the acidizing of a subterranean
9 formation using an acidic solution containing a
corrosion inhibitor which substantially reduces the
11 corrosive effects of the acidic solution on metals in
12 contact with the acidic solution.
13
14 2. Description o~ tlle Prior Art:
16 Acidization of oil-bearing strata is a well known
17 method of increasing oil production. The main
18 constituent of the treatment formulation is the acid,
19 usually hydrochloric acid, hydrofluoric acid, formic
acid, acetic acid, or mixtures thereof.
21
22 As the acid is moved from its manufacturing source
23 to the well borehole, and into the geological
24 formation, it comes into contact with metals in various
25 forms. Although commercial hydrochloric acid is
26 available at a concentration of about 30 to 40 percent
27 by weight, concentrated acid is generally diluted with
28 water to about 15 percent for most well acidizing jobs.
29 However, the strength of acid used in well stimulation
may range from 1 to 30 weight percent HCl, depending
31 upon various well conditions. To prevent metal ions
32 (the most common being iron) from becoming dissolved in
7 ~
1 the acid, the acid may be stored in non-reactive or
2 lined storage vessels prior to use.
4 Without the presence of an effective corrosion
inhihitor, the acidic solution attacks and deteriorates
6 most metals which are contacted. Corrosion by the
7 acidic solution of the tubular goods in the well bore
~ and of the other equipment used to carry out the
9 treatment is o~ major concern to operators. The expense
of repairing or replacing corrosion damaged equipment
11 is extremely high. The corrosion problem is also
12 heightened by the elevated temperatures found in deeper
13 geological formations being treated.
14
It is accordingly an object of the present
16 invention to provide a well acidizing solution which
17 substantially inhibits the deleterious effects of a
18 treatment acid on the equipment used in the acidizing
19 treatment.
21 Another object of the invention is to provide a
22 corrosion inhibitor for a well acidizing solution which
23 is effective to overcome the problems associated with
24 corrosion resulting from contact of the acidic solution
with ferrous and other metals at el~vated temperatures
26 in the range from 150F to 400F and even higher.
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SUMMARY OF THE INVENTION
3 These and other objects are accomplished through
4 the use of a treatment solution whlch contains a
corrosion inhibitor which substantially reduces the
6 corrosive effect of the acid on ferrous and other
7 metals without reducing the eff~ctiveness of the acidic
8 solution in treating the subterranean formation. The
9 acidizing solution is introduced into the subterranean
formation through a well bore at a flow rate and
11 pressure sufficient to permit the acid to dissolve
12 formation materials or foreign materials in the
13 vicinity of the well bore. The acidic solution can
14 comprise, for instance, a solution of hydrochloric
acid, hydrofluoric acid, formic acid, acetic acid,
16 citric acid and mixtures thereof. The corrosion
17 inhibitor comprises a mixture of:
18
19 a complex substituted keto-amine:
21 an acetylenic alcohol:
22
23 an alkanol;
24
a rosin acid component;
26
27 a non-ionic surfactant; and
28
29 an antimony compound.
31 Preferably, the corrosion inhibitor composition is
32 added to the acid solution in an amount effective to
33 reduce the corrosive effect of the acid solution on the
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23 1 rJ ~
1 ferrous metal, the corrosion inhibitor composition
2 comprising a mixture o~ the following components by
3 weight percent, based on the total weight of corrosion
4 inhibitor:
6 (a) a complex substituted keto-amine which
7 is a condensation product preparPd by a Mannich
8 reaction of formaldehyde, primary amines and ketones,
9 the complex substituted keto-amine being present in the
range from about 30-40 % by weight;
11
12 (b) an acetylenic alcohol, wherein the
13 acetylenic alcohol has the general formula:
14
R3
16
17 Rl- C- C- C--OH
18
19 ~2
21 wherein Rl, R2 and R3 are selected from the
22 group consisting of hydrogen, alkyl, phenyl,
23 substituted phenyl and hydroxy-alkyl radicals, the
24 acetylenic alcohol being present in the range from
about 5-25 % by weight;
26
27 (c) an alkanol, present in the range from
28 about 10-20 weight percent;
29
(d) a rosin acid component, present in the
31 range from about 1-10 weight percent; and
32
2 ~ ~, 3 ~ ^~
1 (e) a non-ionic surfactant, present in the
2 range from about 5-20 weight percent.
4 The corrosion inhibitor also has added thereto an
antimony compound present in an amount effective to
6 provide an antimony concentration of from about 0.0007
7 to about 0.04 molar solution to the corrosive acid.
9 Additional objects, features and advantages will
be apparent in the written description which follows.
DETAlLEr) DESCRIPTION OF THE INVENTION
3 The acidizing treatment fluids of the invention
4 are solutions containing one or more commonly available
acids. The acidizing treatment fluids can be
6 comprised, for example, of hydrochloric acid or
7 mixtures of hydrochloric acid with hydrofluoric acid,
8 acetic acid, formic acid, citric acid and mixtures
9 thereof. The acid concentration may range between
about 1~ and about 30%, by weight of the treatment
11 fluid, depending upon the type of acid used and well
12 conditions present.
13
14 The acidizing fluid of the invention also contains
a corrosion inhibitor composition which is a mixture of
16 a complex substituted keto-amine, an acetylenic
17 alcohol, an alkanol, a rosin acid component, a non-
18 ionic surfactant, and an antimony compound.
19
The complex substituted keto-amine is a
21 condensation product prepared by a Mannich reaction of
22 formaldehyde, primary amines and ketones as described
23 in U.S. Patent No. 3,071,590, entitled "Condensation
24 Products of Formaldehyde, Primary Amines and Ketones",
issued January 1, 1963, to Gardner, the disclosure of
26 which is incorporated herein by reference. Preferably,
27 the complex substituted keto-amine is of the formulao
28
29
~ ,",
31 ~ t~ Cl~C11~n~CIt~t~ ]~
32 h~
33
2 ~3 L C,~ .~ J . j
3 wherein R' is selected from the group
4 consisting of alkyl and alkenyl of 8 to 22 total carbon
atoms, R " is selected from the group consisting of
6 alkyl of from 1 to 19 carbon atoms, phenyl, benzyl,
7 biphenyl and thienyl; X is an acid radical selected
8 from the group consisting of Cl, S04 and Br; n is an
9 integer from 1 to 2 inclusive, and v is an integer
inverse to that of n whereby to satisfy the valence of
11 the imidazoline radical.
12
13 Particularly, preferred complex substituted keto-
14 amines are selected form the group consisting of:
16 2-heptadecenyl-1-(N-butanone-3)-aminoethyl
17 imidazoline dihydrochloride;
18
19 5-methyl-2-hexadecyl-1-(N-alpha-methyl-
cyclohexanone)-aminoisopropyl imidazoline sulfate;
21
22 2-heptadecyl-1-(N-4-methyl, pentanone-3)~
23 aminoethyl imidazoline dihydrochloride;
24
2-undecyl-1-(N-butanone-3)-aminoethyl
26 imidazonline dihydrochloride;and
27
28 2~undecyl-1-(N-phenyl-3, propanone-3)-
29 aminoethyl imidazoline dihydrochloride.
31 The complex substituted amine component o~ the
32 acidizing fluid is present in the range from about 30
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1 to 40 weight percent, based on the total weight of the
2 corrosion inhibitor.
4 The acetylenic alcohol component of the corrosion
inhibitor includes any of the acetylenic alcohols
6 having the general formula:
R3
11 1
12 R1- C C - C-OH
13
14 R2
16
17 wherein R1, R2 and R3 are hydrogen, alkyl,
18 phenyl, substituted phenyl or hydroxy-alkyl radicals.
19 Preferably, R1 comprises hydrogen~ Preferably, R2
comprises hydrogen, methyl, ethyl or propyl radicals.
21 Preferably, R3 comprises an alkyl radical having the
22 general formula CnH2n, where n is an integer from l to
23 10.
24
So~e examples of acetylenic alcohols which can be
26 utilized for the purposes of the present invention
27 include methyl butynol, methyl pentynol, hexynol, ethyl
28 octynol, propargyl alcohol, berlzylbutynol,
29 ethynlcyclohexanol, and the like. The preferred
acetylenic alcohol is propargyl alcohol. The acetylenic
31 alcohol component is present in the corrosion inhibitor
32 composition in the range from about 5 to 25 weight %
33 based on the total weight of the corrosion inhibitor.
r~
2 Propargyl alcohol is a commercially available
3 acetylenic primary alcohol. It is a colorless, volatile
4 liquid which is miscible in water and many organic
solvents. Propargyl alcohol has a density at 20'C of
6 0.9715, a boiling point of 114C and a viscosity at
7 20C in Cp. of 1.68.
9 The alkanol component of the corrosion inhibitor
composition can be, for example, methyl, ethyl, propyl,
11 isopropyl, butyl, pentyl, hexyl, heptyl, octyl and
12 other higher liquid members of these aliphatic
13 alcohols. The preferred alkanol component is isopropyl
14 alcohol because of its commercial availability. The
alkanol component is preferably present in an amount
16 sufficient to maintain the other components of the
17 corrosion inhibitor in homogeneous admixture.
18 Preferably, the alXanol component is present in the
19 range from about lo to 20 weight %, based on the total
weight of corrosion inhibitor composition.
21
22 The rosin acid component can be, for exa~ple,
23 abietic, sapiatic, or the pimaric type acids derived by
24 distillation of the oleoresin obtained from various
species of pine trees. These materials are used
26 extensively in protective coatings, printing ink
27 formulations, and the like. The rosin acid component
28 is preferably present in the range from about 1 to 10
29 weight %, based on the total weight of corrosion
inhibitor.
31
32 The non-ionic surfactant component useful in the
33 corrosion inhibitor compositions of the invention
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~ f~ ~? g
1 include ethoxylates of alkyl phenols, primary fatty
2 alco~ols, secondary fatty alcohols, and the like,
3 including alkyl and alkylaryl polyether alcohols such
4 as the reaction product of trimethyl-l-heptanol with
seven mols of ethylene oxide, the reaction products of
6 octyl or nonyl phenol with, e.g., from about 8 to 30
7 mols or more of ethylene oxide,
8 polyoxyethylenepolyoxypropylene block copolymers, and
g the like. A suitable non-ionic surfactant for purposes
of the present invention is commercially available from
11 the ~hom & Haas Company as the Titron N-101 and is an
12 ethoxylated nonyl phenol. The non-ionic surfactant is
13 preferably present in the range from about 5 to 20
14 weight %, based on the total weight of corrosion
inhibitor.
16
17 The antimony component of the corrosion inhibitor
18 of the invention can be any antimony compound capable
19 of reacting with the other components of the corrosion
inhibitor to substantially reduce the corrosive effect
21 of the acidic fluid on metals, particularly ferrous
22 metals, in contact with the acidizing fluid.
23 Preferably, the antimony compound is selected from the
24 group consisting of antimony trioxide, antimony
pentoxide, antimony trichloride, antimony
26 pentachloride, alkali metal salts of pyroantimonate,
27 antimony adducts of ethylene glycol and solutions
28 containing ethylene glycol, water and the oxidized
29 product of hydrogen peroxide and at least one member
selected from the group consisting of trivalent
31 antimony compounds. The most preferred antimony
32 compound is antimony trioxide. Preferably, a suf~icient
33 guantity of the antimony compound is present in the
r,~ r-
1 acidizing fluid to obtain a solution having a
2 concentration o~ ~rom about 0.007 to abouk 0.04 molar.
3 The antimony component can be admixed with the other
4 component of the corrosion inhibitor composition to
form a premixed inhibitor or it may be formulated in
6 situ in an acidic solution by the addition of a
7 sufficient quantity of the antimony compound and a
8 quantity of the other constituents which may be
9 premixed.
11 The method of the invention can be carried out by
12 first admixing an aqueous fluid with the acid to
13 provide an acidic solution of a desired concentration.
14 The corrosion inhibiting composition is then admixed
with the solution in an amount sufficient to
16 substantially reduce the corrosion rate of the acid on
17 metals in contact with the acid. When the corrosion
18 inhibiting composition is generated in situ, all of the
19 components except the antimony compound are preferably
admixed prior to the addition of the antimony compound.
21 The amount of corrosion inhibitor utilized in the
22 practice of the invention can vary over a substantial
23 range. Preferably, the inhibitor is present in an
24 amount of from about 10 to 30 gallons per 1000 gallons
of acidic solution. The concentration of corrosion
26 inhibitor will vary, however, depending upon the
27 concentration of the acid solution and the temperature
28 at which the acidic solution will contact the metal
29 surfaces.
31 The aqueous acidic solution is introduced into the
3~ subterranean formation whereb~ either foreign material
33 in the well bore or in the formation or formation
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2 ~3 :~ ~ t'3~
1 materials are dissolved to increase the permeability of
2 the formation. The increased permeabi]ity permits
3 better flow of hydrocarbon fluids through the formation
4 and into its well bore. The pumping rate and pressure
utilized will depend upon the characteristics of the
6 formation and whether or not fracturing of the
7 formation is desired. After the aqueous acidic
8 solution has been injected, the well may be shut in for
9 a period of time. The shut in period may depend on
various factors such as the type of acid employed, the
11 type of formation, the objective of the treatment, etc.
12 If there is pressure on the well, pressure then can be
13 released and the spent or at least partially spent
14 aqueous acidic solution, containing salks formed by the
reaction of the acid, is permitted to flow back into
16 the well bore and is pumped or flowed to the surface
17 for appropriate disposal.
18
19 The following examples are intended to be
illustrative of the invention:
21
22 EXAMPLE 1
23
24 To determine the effect of antimony concentration
on the inhibitor composition, the following tests were
26 performed: An acidic aqueous solution was prepared hy
27 adding concentrated hydrochloric acid to water to form
28 a 10% HCl solution. ~ corrosion inhibitor composition
29 was prepared as described above by mixing together the
complex substituted keto amine, propargyl alcohol,
31 isopropanol, rosin acids and non-ionic surfactant.
32 Then, a quantity of antimony compound as set forth
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2 ~J ~
1 below was added to the treating acid and co-mixed with
2 the other constituents of the corrosion inhibitor.
4 The acid solution containing corrosion inhibitor
and antimony compound at the concentration set forth
6 below, was then heated to a temperature of 350~F under
7 l,OoO psig pressure and a weighted sample of 1020 mild
8 steel was suspended in the solution. The volume ts
9 surface area ratio of the acidic solution to the metal
sample is about 25 cc/in2. After six hours, the metal
11 sample was removed from the solution, washed and
12 weighed to determine the corrosion loss (lb/ft2).
13
14 Test Conditions:
16 Temperature : 350F
17 Steel : 1020 mild steel
18 Acid : 10% HC1 (by weight)
19 Pressure : 1000 psi
Duration : 6 hours (at temperature)
21
22 Results-
23
24 Corrosion Sb2O3 Weight Loss
Inhikitor, ~ Conc._~_ppt lb/ft-
26
27 1.0 10 .0011
28 1.0 15 .0008
2Q 1.0 20 .0009
1.5 15 .0017
31 1.5 20 .0027
32
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2 5.J ,'~ r.
1 EX~MPLE II
3 Tests were also performed to test the
4 effectiveness of the corxosion inhibitor of the
invention as compared to a prior art formulation
6 containing an acetylenic alcohol, a quaternary ammonium
7 compound, an aromatic hydrocarbon and an antimony
8 compound. These tests were performed by adding the
9 same quantity of inhibitor/antimony compound to 15% HCl
acid solutions. The quantity of inhibitor added was
11 1.5% (by volume) and an antimony compound was mixed
12 with the acidic solution in an amount sufficient to
13 provide an antimony concentration of about 0.0197 molar
14 in the acidic aqueous solution. A weighted sample of
N-80 grade steel was then suspended in the acid and the
16 solution heated to a temperature of 325F under 1,000
17 psi nitrogen pressure. After 6 hours contact time (at
18 temperature) the metal sample was removed from the acid
19 solution, cleaned and weighed to determine the
corrosion weight loss. The effectiveness of each
21 inhibitor composition is illustrated by the following
22 data:
23
24 RESULTS:
26 Steel Sample Corrosion
27 InhibitorWeight, gm Weight Rate
228 System Initial Final Change, gm lb/ft2
30 Invention
31 Inhibitor/
32 Antimony 40.0388 39.8647 -0.1741 .0125
34 Prior Art
35 Inhibitor/
36 Antimony 42.9500 42.0448 -0.9052 .0652
37
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~ 3~r-
1 The corrosion rate of the present
2 inhibitor/antimony system of 0.0125 lb/ft2 is
3 substantially less than the general oil industry
4 allowable corrosion rate of about 0.05 lb/ft2. In
addition to the lower corrosion rate showed hy the
6 present invention s~stem, a difference in the coating-
7 film forming protection established on the metal
8 surface by the two inhibitors was also observed. The
9 sample exposed in the inventive syste~ showed a very
uniform, fine coating on all metal surfaces, whereas
11 the coating on the comparative sample was irregular,
12 leaving some areas of the metal unprotected. The test
13 results suggest that the components of the inhibitor of
14 the invention react differently with antimony than the
prior art components. The resulting synergism has been
16 observed to provide a higher degree of acid corrosion
17 protection.
18
1~ An invention has been provided with several
advantages. The corrosion inhibitor/antimony
21 composition of the invention provides a substantial
22 increase in corrosion protection, at temperatures above
23 300F, over other inhibitor systems tested. Various
24 oil field alloys, such as N-80, mild steel, and 13 Cr
stainless steels can be protected with the corrosion
26 inhibitor/antimony system. The composition is
27 compatible with many traditional additives used in
28 acidizing formulations, such as mutual solvents,
29 surfactants, sequestering agents, etc. The inhibitor
is stable under all well treatment conditions.
31
32 While the invention has been shown in only one o~
33 its forms, it is not thus limited but is susceptible to
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1 various changes and modifications without departing
2 from the spirit thereof.
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