Note: Descriptions are shown in the official language in which they were submitted.
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! (EXX0N 13)
METHOD OF INHlBlTING CORROSI~N IN ACI~I~ING WELL~
1 BACKGR0UND OF THE INVENTIO~
This invention relates generally to corrosion inhibitors
and more specifically to the use of corrosion inhibitors contain-
in~ quaterndry/anti~ony complex in acid solutions used in acid
treatment of subterranean formations without acetylenic alcohols.
In one aspect, the invention relates to the direct addition of the
~ corrosion inhibitor additives directly to the aqueous acid
solution used in well acidizina.
DESC~IPTION OF THE PRIOR ART
Acids and acid solùtions have long been used in the
stimulation of oil wells, gas wells, ~ater wells, and similar
boreholes. ~cid stimulation is performed in wells completed in
subterranean formations. Acidi2ing is used in conjunction with
hydraulic fracturing techniques and matrix acidizing techniques.
In both acid fracturing and matrix acidizing, the well treating
acid solutions, usually HCl, HF, or mixtures thereof, are pumped
through the well tubular goods and injected into the formation
where the acid attacks formation materials increasing its
permeability to oil and/or gas.
In order to protect the equipment and tubular goods from
the corrosive effects of the acid, the well treating acid almost
always includes a corrosion inhibitor.
Corrosion inhibitors of diverse description and
composition have been proposed over the years for use with well
treating acids. Corrosion inhibitors that have received wide
spread use are those containing metalJquaternary ammonium
complexes. Some of these are described in the following U.S.
Patents: 3,773,465 (cuprous iodide); 4,498,997; 4,522,658;
and 4,552,672 (antimony compounds).
In the past, the metal/quaternary complexes, havé been
used with an acetylenic compound which apparently contributes to
the effectiveness of the complex, particularly at high tempera-
tures and high concentrations. Corrosion inhibitors containing
acetylenic compounds are toxic. Therefore, it is desirable to
avoid the use of the acetylenics where possible.
f - 2 ~ 2 0 5 1 0 8 1
~ 1 SUMMARY OF THE INVENTION
The method o~ the present invention comprises the steps
of adding directly to a well treating aqueous acidizing solution
corrosion inhibitor additives consisting essentially of:
(a) a surfactant;
(b) an antimony compound or antimony metal
mixture; and
(c) an ammonium quaternary compound capable of~
forming a complex with the antimony and other
metals in the mixture.
, Surprisingly, it has been found that the nonacetylenic
corrosion inhibitor additives described above, when added directly
to the aqueous acid solution, exhibits excellent dispersion and
provides improved corrosion protection for the well equipment at
relatively low concentrations in comparison to corrosion
inhibitors with acetylenics and aromatic hydrocarbons.
Although the reasons for the improved performance are
not fully understood, it is believed that the acetylenic compound
and/or the aromatic hydrocarbon solvent interfere with deposition
of the antimony on the well tubulars.
The concentrations of the three essential additives in
the acid solution are as follows:
MOST
BROAD PREFERRED PREFERRED
RANGE RANGE RANGE
25 Component (wt%) (wtX) (wt%)
Metal/
Metal Mixture .04 to 2.0 .05 to 1.0 .07 to .80
Quaternary
30Compound 0.2 to 10 0.4 to 5.0 0.4 to 2.2
Surfactant 0.1 to 25 0.1 to 5.0 0.1 to 1.5
Generally, the component ranges are interchangeable. For
example, the most preferred range of a metal component may be used
with both the broad and preferred ranges of the other components.
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? 205 ~ 08 1
1 The metal colnpound will always include antilnony, either alone or
as one compounn of a binary or ternary blend. At least 0.04 wt~
of antimony should be present in the acid.
The corrosion inhibitor components are separately
introduced into the well treating acid at a concentration suffi-
cient to coat the well tubulars and equipment. The concentration
of each component in the acid solution should generally be suffi-
cient to provide the acid solution with from 0.04 wt% to 0.80 wt%
of Sb.
The method of the present invention provides effective
corrosion high temperature protection associated with metal salt
complexes and employs low toxicity additives which are separately
dispersible in the aqueous acid solution. The method of the
present invention offers the operational advantage of direct
addition and dispersion in the acidizing solution without
preformulation. The corrosion inhibitors with acetylenic
compounds of the prior art generally required solvents and
premixture of at least so~e of the components.
DESCRIPTION OF PREFERRED EMBODIMENTS
As indicated above the method of the present invention
employs only three essential additives which combine in situ when
added to a well treating acid solution to provide effective cor-
rosion inhibition. Each of these compounds as well as the acid
solution in which they are used are described below.
Aqueous Acid Solutions: Any of the known oil field
acids may be used. These are referred to herein as "well treating
acids" and include aqueous solutions of hydrochloric acid (HCl),
hydrofluoric acid (HF), mixtures of HCl and HF (i.e. mud acid),
acetic acid, formic acid, and other organic acids and anhydrides.
The most common acids are 3X H~l, 7 1/2X HCl, 15X HCl, 28X HCl and
blends of HCl and HF (mud acid). Mud acid is normally a blend of
6 to 12X of HCl and 1 1/2 to 6X HF.
Antimony Compounds and Mixtures: The function of the
antimony and/or the meta1 mixed therewith is to complex with the
quaternary ammonium compound and form a protective deposit on the
metal tubulars and equipment.
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1 Tests have shown that salts of the following metals and
mixtures thereof exhibit corrosion protection when co;nplexed with
a quaternary ammonium compound or conpounds: Sb, Sb/Al. Sb/~l/Cu+,
Sh/Cu~, Sb/Ca/Cu~, and Ca/Sb. The preferred metals are Sb
alone and Sb, Cu+, and Ca binary alld ternary ~l~ixtures.
The metal salts or mixtures must be readily dispersible
in the aqueous acid solution and form a complex with the
quaternary ammonium compound. The term ~complexU as used herein
means a coordination or association of the metal compound with the
quaternary compound.
The preferred antimony salts and salts of the mixture
are halides, specifically metal chlorides. Some of the salts n,ay
be formed in situ, in acid solution. For example, antimony chloride
is produced from Sb203 in aqueous acid such as HCl. The insoluble
Sb203 is converted to soluble salt.
The antimony compound may comprise, for example,
antimony trichloride, antimony pentachloride, antimony
trifluoride, alkali metal salts of antimony tartrate, antimony
adducts of ethylene glycol, and antimony trioxide or any other
trivalent or pentavalent antimony compound and the like. As men-
tioned above, the antimony oxides may be converted to halide salts
in the presence of ~queous acid.
The cuprous compound may be cuprous iodide as described
in U.S. patent 3,773,465.
The binary and ternary metal mixtures are preferred for
particularly severe corrosive environments since they appear to
combine synergistically to provide protection. The binary and
fernary metals may be mixed in any ratio, provided Sb constitutes
at least 20 wt%, preferably 30 wtX, of the metal mixture.
Quaternary Compounds: The quaternary ammonium compounds
(referred to as ~uaternary~ herein) employed in the present in-
vention must be capable of complexing with the antimony and other
metals of the metal mixture (if employed). The preferred quater-
nary comprise aromatic nitrogen compounds which may be illustrated
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_ 1 by alkyl pyridine-N-methyl chloride quaternary, alkyl pyridine-N-
benzyl chloride quaternary, quinoline -N-methyl chloride quaternary,
quinoline-N-benzyl chloride quaternary, quinoline-N-(chloro-benzyl
chloride) quaternary, isoquinoline quaternaries, benzoquinoline
quaternaries, chloromethyl napthalene quaternaries and admixtures
of such compounds, and the like. The quaternary compoun~ and Sb
and Sb mixtures may be used in molar ratios of 1:1 to 5:1.
Generally, the quaternary compound, because of its higher molecular
weight, will be present in the acid solution at a higher concer,-
tration than the metal compound. The weight ratios of the quater-
nary compound and the Sb and Sb mixtures thereof preferably range
from 1:1 to 4:1.
The Surfactant: The surfactant serves to wet the tubu-
lar goods to permit deposition of the quaternary/metal complex.
The preferred surfactants are the nonionics having hydrophilic -
lipophilic balance (HLB~ numbers of 8 to 18, preferably 9 to 16,
such as laurates, stearates, and oleates. Nonionic surfactants
include the polyoxyethylene surfactants (such as ethoxylated
alkyl phenols, ethoxylated aliphatic alcohols) polyethylene
glycol esters of fatty, resin, and tall oil acids. Examples of
such surfactants are polyoxyethylene alkyl phenol wherein the
alkyl group is linear or branched C8 - C12 and contains above
about 60 wt% polyoxyethylene. Octyl and nonyl phenols containing
9 to 15 moles ethylene oxide per mole hydrophobe are the prefer-
red ethoxylated alkyl phenol surfactants.
The polyoxyethylene ester of fatty acids include themono and dioleates and sesquioleates wherein the molecular weight
of the esterified polyethylene glycol is between about 200 and 1000.
Polyoxyethylene sorbitan oleates are also useable.
In practice, the nonionics may be blended to provide the
desired properties. A particularly useful surfactant is a blend
of polyethylene glycol esters of fatty acids and ethoxylated
alkylphenols.
Operation: In operation, the three essential additives
are added to the aqueous acid solution at the well site. The
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1 additives may be added in any order but prefera~ly are in the
~ following order: (1) surfactant; (2) quaternary compound; (3) and
metal compound. The concentration of quaternary/metdl complex in
the acid solution should preferably provide a metal ~including Sb)
concentration of at 0.050 wtX.
The procedure for preparing the inhibited acid for
pumping down the well is preferably by a batch process. In this
process, the additives are blended into the aqueous acid solution
in a large tank and then pumped into the well.
It has been found that the direct addition of the
additives requires only a few minutes for dispersion and complex-
ina to occur, so that any pumping process including the continuous
process may be employed. The batch process, however, is preferred
7 because it assures adequate conditioning of tne corrosion
inhibitor in the acid prior to pumping.
The method of the present invention can be used in wells
to protect tubular goods made of typical oil field tubular steels
such as J-55, N-80, P:105, and the like; or made of high alloy
chrome steels such as Cr-9, Cr-13, Cr-2205, Cr-2250, and the like.
EXPERIMENTS
In order to demonstrate the effectiveness of the non-
acetylenic corrosion inhibitor additiYes added directly to the
acid solution, several samples with and without acetylenics were
tested using various components. The additives used in the tests
were as follows.
The quaternary a~monium compounds used in the experi-
ments was a quinoline-N-benzyl chloride quaternary
(quaternary X).
The surfactant was nonylphenol (10 mols E0).
The HCl acid was 15X-HCl.
The HF was 12X HCl and 3X HF.
The acetylenic compounds were a ble~d of ethyl
octynol and propar~yl in wt ratios of 1 to 1 or 2 to 3.
The Sb compounds were Sb203.
The procedure for preparing the aqueous acid solution
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_ 1 wit~ inhibitor and the test procedure was as follows (all X are
Wtb unless otherwise indicated)
1. The additives were added to the aqueous acid
sol~tion C(15~ HCl or mud acid, (12X HCl/3X
HF)] in the following order
(a) surfactant
(b) acetylenic alcohol
(c~ aromatic hydrocar~on solvent (if used)
(d) quaternary compound
(e)Sb2o3
2. The c~upouns (N-80 steel or Cr-2205) were then
put in the acid solution with the additives and
heated to 350-F under 3,000 psi for four hours.
3. The coupouns were then removed and cleaned, the
weight loss ~easured, and the corrosion rate
calculated.
T~e composition of the samples tested are shown in
Tables I and II.
TABLE I - ACETYLENIC SAMPLES
Additives (wt%)
Sample Surfactant Acet. Solvent Quat. Sb Acid
A-1 0.37 0.35-~.40 0.37-0.40 1.12 0.075 HCl
A-2 0.37 0.35-0.40 0.37-0.40 1.12 0.15 Mud
A-3 0.37 0.35-0.40 0.37-0.40 0.60 0.75 HCl
A-4 0.37 0.35-0.40 0.37-0.40 0.6~ 0.75 hud
TABLE II - NONACETYLENIC SAMPLES
Additives (wt%)
Sample Surfactant ~uat. Sb Acid
NA-1 0.37 1.12 0.075 HCl
NA-2 0.37 1.12 0.15 Mud
NA-3 0.37 0~6 0.75 HCl
NA-4 0.37 0.6 0.75 Mud
The corrosion rates, expressed as pound/ft2, using the
above samples are presented in Table III.
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205 1 08 1
1 ~ABLE III
HCl Corrosion Rate In Mud Acid Corrosion Rate In
Sample N-80 Cr-2205Salnple N-80 Cr-2205
A-10.0156 0.0262 A-2 0.0302 0.0182
NA-10.009~ 0.0158 NA-2 0.0245 0.~107
A-30.0095 0.0089 A-4 0.0078 0.0109
NA-30.0056 0.006p NA-4 0.0052 0.0072
From the Table III data,it can be seen that the non-
acetylenic samples (NA) gave improved results in all tests.
Additional samples were prepared and tests were carried
out using binary and ternary mixtures of Sb. ~hese samples had
the compositions shown in Table IV.
TABLE IV
Additive (wtX~
Sample Surfactant Quat. Sb Mixture1 Acid
NA-5 0.37 1.12 SbtAl HCl
NA-6 0.37 1.12 Sb/Al Mud
20 NA-7 0-37 1.12 Sb/Al/Cu+ HCl
NA-8 0.37 1.12 Sb/Al/Cu+ Mud
NA-9 0.37 1.12 Sb/Ca HCl
NA-10 0.37 1.12 Sb/Ca Mud
NA-11 0.37 1.12 Sb/Cu+ HCl
25NA-12 0.37 1.12 Sb/Cu+ Mvd
NA-13 0.37 1.12 Sb/Ca/Cu+ ~Cl
NA-14 0.37 1.12 Sb/Ca/Cu+ Mud
1The Sb mixtures were dS follows (all wtt):
Sb/Al: Mixture of Sb203 and AlCl3 (Sb 0.38%; Al 0.101 %)
Sb/Al/Cu+: Mixture of Sb203, AlCl3, and CuI (Sb 0.25X;
Al 0.067%; and Cu+ 0.109X)
Sb/Ca: Mixture of Sb203 and CaC12 (Sb 0.38X; Ca 0.136%)
Sb/Cu~: Mixture of Sb203 and CuI (Sb 0.38X; Cu+ 0.164%)
Sb/Ca/Cu+: Mixture of Sb203, CaCl2, and CuI (Sb 0.25X;
Cu 0.091%; and Cu+ ~.109X)
2 0 5 1 0 8 1
_ 1 The corrosion rates (lb/ft2) using the binary and
ternary mixtures of Sb are shown in rable V.
~ABLE V
HCl Corrosion Rate Mud Acid Corrosion Rate
Sample MetalN-80 Cr-2205Sample N-80 Cr-2205
A-3 Sb 0.0095 0.0~8~ A-4 0.007~ 0.010~
NA-5 Sb/Al0.0~95 0.0070 NA-6 0.0143 0.0125
NA-7 Sb/Al/Cu+0.0115 ~.0111 NA-8 0.0078 0.0131
10NA-9 Sb/Ca0.0~66 0.0060 NA-10 0.0086 0.0030
NA-11 Sb/Cu+ 0.0064 0.0086 NA-12 0.0070 U.0041
NA-13 Sb/Ca/Cu+ 0.0069 0.0069 NA-14 0.0042 0.0047
.
A comparison of tne ~able V data reveals that the
nonacetylenic samples (NA) performed generally as good as, an~
frequently better, than the acetylenic samples (A-3 and A-4).
Samples NA-9 throuqh NA-14, containing the binary and ternary
mixtures of Sb, Ca and Cu+, gave exceptional results vis-a-vis
Samples A-3 and A-4. Although the nonacetylenic Sb and Al
mixtures (Samples NA-S though NA-~) performed generally the same
as Samples A-3 and A-4, it is noted that the total metal content
of the acetylenic samples was almost 50% higher than the metal
content of the nonacetylenic samples. Moreover, the Sb content
of the nonacetylenic samples was one-half or less than the Sb
content of Samples A-3 and A-4 with the balance being Al or
Al/Cu~. It was surprising that substitutin~ the less expensive
Al and Al/Cu+ blend in the nonacetylenic samples gave comparable
protection as the acetylenic samples, even at the lower total
metal content.
