Note: Descriptions are shown in the official language in which they were submitted.
5~
~'7~
COMPOSITION AND_METHOD FOR CORROSION INHIBITION
Background
This invention relates to the treatment of metal surfaces to
increase their resistance to corrosion. It further relates to
compositions which form a corrosion-resistant film on metal surfaces to
which they are applied.
The problem of corrosion of metal surfaces in contact with air
snd water ls well ~nown. Corrosion and pitting are accelerated in
environments in which metal surfaces are in contact with chemicals such
as hydrogen sulfide, carbon dioxide and organic acids, and water having a
high electrolyte concentration. Such environments are typical of down-
well conditions in oil and gas wells, in which corrosion of metal pipes,
pumps and other equipment poses a serious problem requiring monitorlng of
well sites, frequent maintenance and costly replacement of parts. Oil
recovery operations in deep-sea oil fields present these corrosion
problems in their most extreme form. The down-well metal surfaces are in
contact with large quantities of corrosive chemicals such as dissolved
acid gases present in the recovered oil, and in addition, the metal
surfaces are subjected to temperatures of 250F or higher and pressures
of 3000 psig or higher, the extreme conditions of temperature and
pressure acting to accelerate corrosion and to intensify the problems of
applying and maintaining chemical protection for the equipment. In
offshore oil wells, secondary recovery operations ir.volving water-
flooding of the undersea formations subjects the down-well equipment to
highly corrosive sea water containing dissolved oxygen.
Conventional corrosion-inhibiting agents are often not
-- effective at all under such extreme conditions or reduce corrosion
$~ ~
often at great expense and inconvenience if the well site is not easily
accessible or, as in the case of off-shore wells, poses difficulties of
transporting and applying large volumes of chemicals.
It is therefore an object of this invention to provide a
composition which can be applied to a metal surface to inhibit corrosion
and pitting on the metal. It is a further object of the invention to
provide a method of treating metal surfaces so as to form a film which
ir.h bits corrosion on the metal even under extreme conditions of --
temperature and pressure and in highly corrosive environments. It is a
further object of the invention to provide an article having a surface
film of a composition which inhibits corrosion.
Summary of the Invention
According to the invention, there is provided a composition ~.-~
which, when applied to a metal surface, forms a corrosion-inhibiting film
on the metal surface, the composition comprising an epoxy resin, an
effective amount of a curing agent for the epoxy resin, an alcohol, and a
hydrocarbon diluent. The composition can be applied by contacting the
~ metal surface with the composition so that a film is formed thereon. The
composition can be applied as one solution or by sequentially contacting
the metal with a hydrocarbon solution of the epoxy resin and a
hydrocarbon solution of the alcohol and curing agent. Also according to
the invention, metal articles having a corrosion-inhibiting film thereon
are provided.
Detailed Description of the Invention
Any epoxy resin having, on the average, more than one vicinal
epoxite group per molecule can be used in the invention composition and
process. The epoxy resin may be saturated or unsaturated, aliphatic,
cycloaliphatic, aromatic or heterocyclic, and may bear substituents ~*~
which do not materially interfere with the curing reaction. They may be
monomeric or polymeric.
Suitable epoxy resins include glycidyl ethers prepared by the
reaction of epichlorohydrin with a compound containing a hydroxyl group
carried out under alkaline reaction conditions. The epoxy resin products
obtained when the hydroxyl group containing compound is bisphenol A are
represented below by structure I wherein n is zero or a number greater
than 0, commonly in the range of 0 to 10, preferably in the, range of 0 to
2.
~ ~ 7~ .7
3 :
O CH
CH2 - CHCH2Cl + HO~ C _<~>-OH NaOH
5EPICHLOROHYDRIN CH3
BISPHENOL-A
O CH3 OH CH3 O : ~~~
-C <~ocH2cH-cH2-o3--<~ -C-<~>-O-CH2CH - CH2
CH3 n CH3
Other suitable epoxy resins can be prepared by the reaction of
epichlorohydrin with mononuclear di- and tri-hydroxy phenolic compounds
- 15 such as resorcinol and phloroglucinol, selected polynuclear polyhydroxy
phenollc compounds such as bis(p-hydroxyphenyl)methane and 4,4'-
dih~aroxy biphenyl, or aliphatic polyols such as 1,4-butanediol and
glycerol.
Epoxy resins suitable for use in the invention have molecular
20 weights generally within the range of 50 to about 10,000, preferably
about 200 to about 1500. The commercially available Epon 828 epoxy
resln, a reaction product of epichlorohydrin and 2,2-bist4-
hydsoxyphenyl)propane (bisphenol A) and having a molecular weight of
about 400, an epoxide equivalent (ASTM D-16i2) of about 185-192, and an n
value in structure I above of about 0.2, is presently preferred because
of the superior effectiveness, as shown in field tests, of the invention
composition containing Epon 828.
Additional epoxy-containing materials suitable for use in the
present invention include the epoxidized derivatives of natural oils
such as the triesters of glycerol with mixed long-chain saturated and
unsaturated acids which contain, e.g., 16, 18 and 20 carbon atoms. Such
natural oils are represented by formula II:
5~3 Sk~
H2C - O - C - R
HC - O - ~ - R
H2C - O - ~ - R
II
wherein R represents alkyl and/or alkenyl groups containing 15 to l9
carbon atoms with the proviso that epoxidation of said oils yields a
polyepoxide having more than one vicinal-epoxy group per molecule of
epoxidized oil. Soybean oil is a typical triglceride which can be
converted to a polyepoxide suitable for use in the instant invention.
Other polyepoxides suitable for use in the present invention
are derived from esters of polycarboxylic acids such as maleic acid,
terephthalic acid, oxalic acid, succinic acid, azelaic acid, malonic
acid, tartaric acid, adipic acid and the like with unsaturated alcohols
as described by formula III:
C - O - R'
C - O - R'
O
III
wherein Q represents a valence bond, or the following groupings: 1,2-
phenylene, 1,4-phenylene, methylene, dimethylene, trimethylene,
tetramethylene, pentamethylene, hexamethylene, heptamethylene,
vlnylene, 1,2-cyclohexylene, 1,4-cyclohexylene 1,2-ethylenediol and the R~
3' ii'ke, and R' represents alkylene and branched alkylene groups containing
4 to 14 carbon atoms. Representative epoxidized esters derived from
materials described by structure (III) include the following: dit2,3-
epoxybutyl)tetrahydrophthalate, di(2,3-epoxyoctyl)oxalate, di(2,3-
epoxyisobutyl)adipate, di(3,4-epoxypentyl)succinate, di(4,5-
epoxydodecyl)terephthalate, di(3,4-epoxyhexyl)phthalate, di(2,3-
epoxybutyl)tartrate, di(7,8-epoxytetr~decyl)adipate, di(3,4-
epoxybutyl)glutarate, di(2,3-epoxyhexyl)pimelate, ~ di(3,4-
~i7~S~
s
epoxyoctyl)suberate, di(4,5-epoxydecyl)azelate, di(2,3-
epoxyisohexyl)tetrahydroterephthalate and the like.
In addition to the foregoing, it is contemplated that suitable
polyepoxides can be derived from esters prepared from unsaturated
5 alcohols and unsaturated carboxylic acids described by formula IV: -
O
R"O - C - R"' ~~
IV
wherein R" represents alkenyl and cycloalkenyl groups containing 4 to 12
csrbon atoms and R"' represents alkenyl and cycloalkenyl groups
contalning 4 to 12 carbon atoms. Representative epoxidized esters -.
include the following: 2,3-epoxypentyl-3,4-epoxybutyrate; 2,3-
epoxybutyl-3,4-epoxyhexanoate; 3,4-epoxyoctyl-2,3-epoxycyclohexane
carboxylate; 2,3-epoxydodecyl-4,5-epoxyoctanoate; 2,3-epoxyisobutyl-
4,5-epoxydodecanoate; 2,3-epoxycyclododecyl-3,4-epoxypentanoate; 3,4-
epoxyoctyl-2,3-epoxycyclododecane carboxylate and the like.
Other unsaturated materials which can be epoxidized to give
resins suitable for use in the instant process include butadiene based
polymers such as butadiene-styrene copolymers, polyesters available as
derivatives of polyols such as ethylene glycol with unsaturated acid
anhydrides such as maleic anhydride, and esters of unsaturated
polycarboxylic acids. Representative polyepoxides derived from the
la~ter include the following: dimethyl 3,4,7,8-diepoxydecanedioate;
dibutyl 3,4,5,6-diepoxycyclohexane-1,2-carboxylate; dioctyl 3,4,7,8-
diepoxyhexadecanedioate; diethyl 5,6,9,10-diepoxytetradecanedioate and
the like.
Dimers of dienes such as 4-vinyl cyclohexene-l from butadiene
and dicyclopentadiene from cyclopentadiene can be converted to
epoxidized derivatives wh::ch are suitable for use in the instant process.
Any agent suitable for curing epoxy resins may be used in the
invention composition and method. Curing agents for epoxy resins include
amines, acids, anhydrides and aldehyde resins. The curing agent is used
in an amount effective for curing the amount of epoxy resin used.
~7~S~ ~
Curing agents suitable for use in the invention composition
and process include compounds having amino hydrogen atoms. These include
aliphatic, cycloaliphatic, aromatic and heterocyclic amines. Examples
of curing compounds include aliphatic polyamines such as ethylene
diamine, diethylene triamine, triethylene tetramine, tetraethylene
pentamine, 1,4-aminobutane, 1,3-diaminobutane, hexamethylene diamine, 3-
(n-isopropylamino)propylamine, N,N'-diethyl-1,3-propanediamine,
h-:-.Yapropylene heptamine, penta(l-methyl-propylene)hexamine, ~ -
tetrabutylenepentamine, hexa-(l,l-dimethylethylene)-heptamine, di~l-
methylbutylene)triamine, pentaamylene hexamine, tritl,2,2-
trimethylethylene)tetramine, tetra(l,3-dimethylpropylene)pentamine,
penta(l,5-dimethylamylene)hexamine, S-methylnonanediamine, penta(l,2-
dimethyl-l-isopropylethylene)hexamine and N,N'-dibutyl-1,6-
hexanediamine.
A class of polyamines particularly suitable for use in the
invention are N-alkyl- and N-alkylenyl-substituted 1,3-diaminopropanes
and mixtures thereof. Examples of such polyamines include N-hexadecyl-
1,3-diaminopropane, N-tetradecyl-1,3-diaminopropane, N-octadecyl-1,3-
d~aminopLopane, X-pentadecyl-1,3-diaminopropane, N-heptadecyl-1,3-
diaminopropane, N-nonadecyl-1,3-diaminopropane, and N-octadecenyl-1,3-
diaminopropane. Various commercially available mixtures of N-alkylated
and N-alkenylated diamines can be used in the invention. The presently
preferred polyamine is a commercial product sold under the trademark
Duomeen T. This product is N-tallow-1,3-diaminopropane in which the
.; majority of the tallow substituent groups are alkyl and alkenyl
containing from 16 to 18 carbon atoms each, with a minority of
substituent groups having 14 carbon atoms each. It is presently believed
that the effectiveness of Duomeen T in the corrosion-inhibiting
composition stems from its relatively high molecular weight, which
produces a long-chain "net" to cover the metal surface, its
polyfunctionality, and its relatively high boiling point, which permits
its use in high-temperature envlronments. Other commercially available
materials include N-coco-1,3-diaminopropane in which the majority of the
coco substituent groups contain 12 to 14 carbon atoms, commercially
available under the tradename Duomeen C, and N-soya-1,3-diaminopropane,
which contains C18 alkenyl groups along with a minor proportion of C16
alkyl groups.
Additional polyamines suitable for use in the invention can .
contain 3 or more nitrogen atoms as illustrated by the following
examples: N-dodecyl-diethylene triamine, N-tetradecyl-diethylene
triamine, N-tetradecyl-dipropylene triamine, N-tetradecyl triethylene
tetramine and the corresponding N-alkenyl triamines.
Other curing agents which can be used include polyfunctional
nitrogen-containing compounds such as, for example, amino acids, amino
alcohols, amino r~itriles~ and amino ketones; sulfonic acids; carboxylic
acids; and organic anhydrides. `
Alcohols suitable for use in the invention include any
alkanols containing at least one -OH functional group. These include
. alcohols containing 1 to about 15 carbon atoms such as methanol, ethanol,
l-propanol, 2-propanol, butanols, pentanols, hexanols, heptanols, ~~
octanols, l-pentadecanol, and mixtures of these. Polyols containing 1 to
5 carbon atoms such as ethylene glycol, 1,3-propanediol, 2,3-butanediol,
glycerol and pentaerythritol can also be used. Presently, methanol is
preferred, particularly in an anti-corrosion composition containing
xylene as the aromatic hydrocarbon diluent, Epon 828 as the epoxy resin,
an~ Duomeen T as the poiyamine, because Duomeen T is soluble in methanol
at room temperature and because of the effectiveness of the resulting
corrosion inhibiting system.
A hydrocarbon diluent is used for the invention composition.
Examples of hydrocarbon diluents suitable for use in the treating agents
include the isomeric xylenes, toluene, benzene, naphtha,
cyclohexylbenzene, fuel oil, diesel oil, heavy aromatic oils, Stoddart
solvent, crude oil, and condensate from gas wells. Presently, xylene is
the preferred hydrocarbon diluent because it is an effective solvent for
the other preferred components and because of the corrosion-inhibiting
effectiveness of the resulting composition.
The higher-boiling aromatic hydrocarbons are particularly
useful for deeper wells with higher downhole te~peratures and in high-
temperature gas and oil wells generally.
In so~e treatment methods, discussed bclow, it is advantageous
to employ a carrier liquid or drive fluid to force a slug of the
corrosion-inhibiting composition down into the well being treated. Any
of the hydrocarbons listed above as suitable diluents may be used. For
' .
~ s~
practical and economic raasons, diesel oil, sea water or condensate from
the well being treated are preferred carrier fluids.
Various alcohol-aromatic hydrocarbon azeotropes can be used in
the invention compositions to supply at least partially the diluent and
the alcohol components. Representative azeotropes include the
following, with the weight percent of each component in parenthesis:
methanol (39.1)/ benzene (60.9); ethanol (32)/benzene (68); 2-propanol
(33.3)1benzene (60.7); l-propanol (16.9)/benzene (83.1); isobutyl
alcohol (9.3)/benzene (90.7); l-butanol (68)/p-xylene (32); 2-pentanol
(28)/toluene (72) and hexanol (13)/p-xylene ~87). It is also
contemplated that impure salcohol streams such as mixed butanols
resulting from Oxo technology using propylene feedstock can be used inthe treating compositions. ' ~~
The components of the corrosion-inhibiting system can be mixed
in any order, but it is presently preferred to dissolve the epoxy resin
in a hydrocarbon and add an amine/alcohol/hydrocarbon mixture to this
solution. A batch of the treating composition can be prepared by mixing
a first solution of alcohol, hydrocarbon and amine in, for example,
ap~s oximately a 1:1:1 (mL:mL:g) ratio and a second solution of an epoxy
resin in a hydrocarbon in about a 3:1 (g:mL) ratio. The corrosion-
inhibiting agent is then prepared by mixing the first and second
solutions in such proportions that the weight ratio of polyamine to epoxy
resin in the final solution varies over the broad range of about 1000:1
to 1:500, preferably about 100:1 to 1:50, and most preferably about 10:1
to 1:5. The weight percent of alcohol in the final composition varies
over the broad range of 1 to 99, preferably 10 to 60, and most preferably
20 to 30. The hydrocarbon diluent can be present in any concentration
range in which the invention composition remains in an essentially fluid ~3~Ppumpable state.
The invention composition is useful for coating oxidizsable
metal surfaces, particularly surface of objects made from iron and
steel. It is particularly useful for treating metal surfaces such as
metal pipes and casings in oil, gas ahd geothermal wells, which are
subjected to high temperatures and pressures and corrosive chemical
agents.
~'7~S~
Down-well treatments with the corrosion-inhibiting
compositions can be effected by a variety of methods depending upon the
particular chemical and physical characteristics of the well being
~reated. When treating metal surfaces, particularly in down-well
applications, the corrosion-inhibiting composition can be applied as ---
one solution, or alternatively it can be applied by contacting the metal
surfaces sequentially with a solution of the curing agent and a solution
of the epoxy resin. In practice, the resin solution and amine solution
can be pumped from separate storage tanks to a static mixer at a T-
juncture immediately prior to pumping the mixture downhole. Thefollowing down-well treatment methods can be used to apply the
composition to metal surfaces of equipment used to recover natural fluids
from a subterranean reservoir.
Batch Treatment. The invention composition comprising
alcohol, epoxy resin, curing agent and hydrocarbon diluent is introduced
preferably in an oil carrier into the annulus of a cased wellbore between
the casing and the tubing. The well is returned to production and the
in~ected composltions are gradually returned with the produced fluids,
effecting en route the coatlng of contacted metal surfaces with a
corroslon-resistant fllm. Alternatlvely ln this method, a liquid column
of the treating agent can be placed ln the tubing or the annular space
ant allowed to stand for a time which can range from lQ min. to 24 hours
before resumlng productlon, usually at least 2hours.
Extended Batch Treatment. The invention composition ls
in3ected into the annular space of a cased wellbore, the well is closed
off, and the composition is continuously circulated with well fluids down
the annulus and up the tubing for an extended period of time which csn
vary widely but will usually be between 6 and 48 hours. ~t the end of the
determined time period, the well is returned to production.
~9~ Treatment. The invention composition is injected down
a cased wellbore penetrating a subterranean formation and is forced into
the formation against formation pressure with high-pre~sure p~mps. The
composition can be injected within a gelled or dispersed polymer matrix ~ -
based, for example, on polyacrylamides, biopolysaccarides, or cellulose
ethers. After the pressure is released, the tresting agent is slowly
produced back with the recovered fluids, resultin~ in the apPlication of
P17~S6{) ~
a corrosion-resistant film on metal surfaces contacted by the treating
agent as it flows to the surface. This method is particularly suitable
in high-pressure gas or oil wells.
Spearhead Treatment. A highly concentrated slug of the
invention composition, for example about 27 weight percent alcohol,
about 27 weight percent amine, about 15 weight percent epoxy resin, about
31 weight percent hydrocarbon diluent, is injected into the tubing of a
cased borehole and pressured down the tubing with a fluid column of a :_
brine solution such as 2 weight percent aqueous potassium chloride. When
the pressure is released, the aqueous brine column and the corrosion-
inhibiting composition are produced up the tubing. The composition as a
concentrated slug thus contacts the metal walls of the tubing and lays
down a protective film as it flows in a downward and upward circuit. -
Metal surfaces can also be protected by dipping or spraying the
surfaces with the invention compositions and then allowing excess fluid
to drain from the treated surfaces at ambient conditions. A protective
film is thus formed on the metal surface without conventional heat-curing
or extended air-drying treatment, although such drying treatments can be
used if desired and if conditions permit it. The advantage in using an
anti-corrosion system which does not require air- or heat-drying is that
the system can be applied to metal surfaces which are hundreds or
thousands of feet below ground level or are in an environment which is
always flooded with brine or other fluids.
When applying the composition to the metal tubing of, for
example, a gas or oil well, it is not necessary to pre-coat the treated
metal surfaces with oil or other substances prior to applying the
invention composition, and the treated surfaces may or may not have an
oil coating prior to the application. The invention has been found
effec~ive in inhibiting corrosion in wells producing as much as 95
percent brine and 5 percent oil.
The nature of the film thus formed can vary accord'.ng to the
particular composition used and the environment in which it is applied,
but it has been found that the film will generally be a soft, sticky
layer adhering to the metal surface. It is not necessary that the
composition harden to a tough coating, and it has been found in
laboratory runs that the applied film tends to maintain a tacky or greasy
consistency.
/0
11
EXA~IPLE I
This example describes the trestment of an open-ended cased
borehole in the North Burbank field in Oklahoma to inhibit corrosion on
metal surfaces of the down-well equipment. The test well was a low fluid
level well producing about 550 barrels of water per day (bwpd) and 4-5
barrels of oil per day (bopd).
A solution of xylene, methanol and amine curing agent was mixed
with a xylene solution of an epoxy resin to give a total of 25 gallons of
the invention treating composition. The final composition was 27 weight
percent methanol, 27 weight percent Duomeen T curing agent, 15 weight
percent Epon 828 epoxy resin, and 31 weight percent xylene.
The 25 gallons of inhibitor solution were poured into the
annulus of the closed well. The fluids were circulated through the
tubing and annulus for about 24 hours in an extended batch treatment.
The well was returned to production and the corrosion rate was monitcred
by a conductivity probe for a period of 54 days. Prior to injection of
the invention composition, the rate of corrosion was about 3.6 mils per
year (mpy). During the subsequent 53-day period, the corrosion rate
dropped and stayed below the target rate of 0.5 mpy. The iron count
measurements in the produced water decreased from 33 ppm initially to
about 24 ppm and remained at that level.
After 53 days, the corrosion rate had increased to 0.5 mpy,
where it remained for 3 days. The well was then retreated with a 5-
gallon batch of the same corrosion-inhibiting composition. The same
extented batch trea~ment was used, except that the fluids were circulated
for 6 hours instead of 24 hours. Following this retreatment, the
corrosion rate remained in the range of 0.1 to 0.45 mpy for 21 dayq.
In an alternate method of treatment using the same
composition, a 5-gallon batch of the invention corrosion inhibitor was
poured directly into the annulus and flushed for five minutes wlthout
shut-in for circulation of the fluids. The corrosion rate remained below
0.5 mpy for about one week, after which the well was retreated by the
same method. Two weeks later, when the testing ended, the corrosion rate
was 0.1, confirming the effectiveness of the invention corrosion
inhibitor in a batch treatment operation.
12
Prior to the testing of the invention composition, a
commercially available, long-chain, high-boiling amine corrosion
inhibitor had been used. The treatment program consisted of flushing
eleven gallons of the commercial corrosion inhibitor into the annulus
S initially and then retreating with five quarts every four days to control
corrosion The invention composition was considerably more eficient in
terms of its effectiveness in controlling corrosion rate over an extended
period of time than was the commercial inhibitor.
EXAMPLE II
This example cescribes the treatment of an open-ended cased
borehole in the North Burbank field in Oklahoma to inhibit corrosion on
down-hole metal surfaces. The test well was a high fluid level well
producing about 1250 bwpd and 6 bopd.
A solution of xylene, methanol and Duomeen C curing agent was
mixed with a xylene solution of Epon 828 epoxy resin to give a total of lS
gallons of a composition containing 31 weight percent xylene, 27 weight
percent methanol, 27 weight percent Duomeen C and 15 weight percent Epon
828.
The lS gallons of inhibitor solution were poured into the
annulus of the closed well. The well fluids and inhibitor were
circulated through the tubing and annulus for 24 hours in an extended
batch treatment process. The well was returned to production and the
corrosion rate was monitored by a conductivity probe for a period of
about two weeks. During this time the corrosion rate was generally
greater than the target rate of O.S mpy. A subsequent treatment with an
additional 15-gallon batch of the Duomeen C-containing inhibitor failed
to reduce the corrosion rate to this level over a 7-day period. The
corrosion rate was 3.5 mpy when the inhibitor composition of Example I
~containing Duomeen T curing agent) was applied to this well.
A 15-gallon volume of the Duomeen T-containing composition
described in Example I was placed in the test well and circulated for 24
hours. The corrosion rate decreased from 3.5 mpy to about 0.1-0.2 mpy
and remained below the target level of 0.5 for a period of about 98 days.
Iron count during this time remained in the range of 14-17 ppm.
Previously in this well, it was necessary to apply a commercial inhibitor
~n pn in~ti~l ll-o~lll~n tr~ tmc.nt :~nA f~ll~ T~ T'~-l'r ~ TC' ~.~;tl~ 7_~ .T'
13
treatments. This result demonstrates the efficiency and effectiveness
of the xylene/Duomeen T/methanol/Epon 828 system in reducing the
corrosion rate in cased oil wells. It also demonstrates the necessity of
determining the appropriate corrosion inhibitor solution for each well
or set of well conditions. A composition containing Duomeen C was an
effective corrosion inhibitor in the laboratory under simulated well
conditions, but did not perform effectively under the conditions
encour;tered in this particular test well using the extended batch
treatment method.
EXAMPLE III
This example describes the use of the invention composition
. for reducing the corrosion rate in a hot gas condensate well in the
Parcperdue Fieid, Lafayette Parish, Louisiana. The well was a hot (about
256~F) gas condensate well producing about 7.2 MMcfd gas containing 1
percent carbon dioxide, 3 bwpd and 400 bpd condensate. The well depth
was 13,266 feet and the wellhead pressure was 6000 psig.
A total of 72 barrels of the invention composition in a carrier
of heavy aromatic oil was pumped into the well. The injected fluid
co.;ta ned 2.2 weight percent methanol, 2.2 weight percent Duomeen T
20 curing agent, 1.2 weight percent Epon 828 epoxy resin, 2.5 weight percent
xylene, and 91.9 weight percent heavy aromatic oil. After the tubing was
filled wlth the fluid, the well was shut in for about 1.5 hours. The
inhibitor fluid was then returned to the surface and production was
resumed.
Prior to thls treatment the iron level was 195 ppm, but two
days after the treatment the iron count had dropped to 56 ppm. The iron
level then gradually increased and reached a level of 92 ppm eleven days
after treatment. At the end of about 30 days after treatment, the iron ~2
level had reached 200 ppm and a retreatment was carried out using the
portion of the original solution which had been returned to the surface
during the initial treatment. An additional 4.6 volume percent of the
invention composition was added and 72 barrels of this mixture was pumped
into the well, the treatment method being the same except that the
residence time was increased from 1.5 hours to 24 hours. The iron
35 concentration decreased to 56 ppm but then gradually increased to 101 ppm
over a 23-day period and remained at this level for seven days. At this
14
time it was decided to use a spearhead treatment method on the well as
described below.
Six and one-half barrels of a concentrated solution of the
invention composition containing 27 weight percent methanol, 27 weight
percent Duomeen-T, .5 weight percent Epon 828 and 31 weight percent
xylene were injected into the well followed by 66 barrels of 2 weight
percent aqueous potassium chloride solution. This volume was designed to
.ill ~he tubing to within about 300 feet of the well bottom and avoid
injection of the chemicals into the formation. The well was shut in for
about 1.5 hours and then returned to production. The initial iron
concentration in the produced water dropped from 100 ppm to 54 ppm in 12
days. The iron count remained in the range of 42 to 55 ppm over a period
of 37 days.
EXA~PLE IV
A series of laboratory corrosion inhibition tests were carried
out in l-liter Erlenmeyer flasks equipped with magnetic stirring bars,
under laboratory conditions designed to simulate corrosive oil-water
environments encountered in field drilling sites. A charge of 50 mL of
~rude oil and 950 mL of synthetic brine was used in each run. A slow
stream of carbon dioxide was bubbled through the solution during each
test to maintain the mixture near saturation with CO2 at ambient
conditions. After charging 950 mL of synthetic North Sea water (93.lg
CaC12 2H20, 46.4g ~gC12-6H2O and 781.1g NaCl per 5 gal. distilled H~O)
into the Erlenmeyer flask, the resin/hydrocarbon solution and
amine/alcohol/hydrocarbon solution were individually charged to the
flask, then the specified crude oil was added. The rate of corrosion and
pitting index were determined using a Corrater(R) monitoring system
a~ailable from Rohrback Instruments. A carbon steel probe was suspended
in the stirred oil-water mixture maintained at approximately 49C during
each run.
In a typical run, individual mixtures of 1:1:1 by weight
samples of amine/alcohol/hydrocarbon and 3:1 by weight samples of
resin/hydrocarbon were prepsred. For these laboratory runs, it was
convenient to make a first solution of 1 g Duomeen T, 1 g methanol and 1 g
35 xylene, and a second solution of 3 g Epon 828 and 1 g xylene. Specified
~1~7~5~3 - ~
aliquots of these solutîons were then transferred to the oil-water
mixture contained in the l-L Erlenmeyer flasks. The corrosion rate and
pitting index were observed after various reaction times. Results of the
tests are summarized in Table I. ---
TABLE I
Sol Aa Sol Rb Reaction Corrosion Pitting
Run ~ (g) Crude Oil Time (hrs) Rate (mpy) Index
1 0.63 g 0.158 g Tor 3 0.04 0.00
2 0.6 o,ld NBue 21 0.07 0.00
3 0.42f 0.158 Tor 3 2 1.5
4 0.32 O.O79g Tor 5 0.16 0.10
21 0.1 0.05
0.22h 0.079 Tor 5 2.0 0.6
21 0.25 0.1
6 0.2i 0'05~ Tek 21 0.02 0
7 0.2i 0~05~ NBUe 21 0.1 0
~a) Solution A represents the amine/alcohol/hydrocarbon mixture.
(b) Solution R represents the resin/hydrocarbon mixture.
(c) A 0.6 mL aliquot of solution A was used in this run.
(d) A 0.1 g sample of Epon 828 was used as solution R.
(e) NBU represents North Burbank Unit crude oil used with NBU brine
(96.3g MgC12-6H20, 289.2g CaC12 2H20, 1259g NaCl in 5 gal. dis-
tilled H 0).
(f) This solution contained no methanol (0.21 g Duomeen T and 0.21 g
xylene).
(8) An additional gram of methanol was added to this mixture.
(h) This solution contained no methanol ~0.11 g Duomeen T and 0.11 g
xylene).
(i) A 0.2 mL aliquot of a solution containing 1/3 amine and 2/3 (70Z
xylene and 30% isopropanol) was used.
(j) A 0.05 mL aliquot of a solution containing 75% resin and 25% xylene
was used.
(k) Te represents Teesside crude oil used with synthetic North Sea water.
(m) Tor crude oil used with synthetic North Sea water.
16
The runs in Table I demonstrate the effectiveness of the .r
invention alcohol-containing compositions for inhibiting corrosion in
systems containing Tor crude oil (Runs l and 4) and North Burbank crude
oil (Run 2) using methanol as the alcohol. Runs 3 and 5 show the reduced
S effectiveness of the amine/hydrocarbon/resin system in the absence of an
alcohol. Runs 6 and 7 demonstrate the effectiveness of the invention
isopropanol-containing compositions for inhibiting corrosion in systems
~ontaining Teeside crude oil and North Burbank Unit crude oil, ~~=~
respectively.
EXAMPLE V
This example provides a hypothetical method of treatment for
an off-shore oil well having a depth of about 15,000 feet, formation
temperatures of 300F or higher, and pressures on the order of S000 psig.
An amine solution containing equal parts by weight of xylene, methanol
and Duomeen T and a solution containing 3 parts by weight of Epon 828 and
1 part by weight of xylene are used in the ratio of 4 parts by volume of
the amine solution to 1 part by volume of the epoxy solution. The
solutions are combined in a static mixer at a T-junction before injection
into the well. Two barrels of the inhibitor solution are injected for
20 each 5000 feet of 3-7/8" I.D. tubing. The injection of inhibitor
solution is followed with 10 to 15 barrels of formation water or fresh
water. The inhibitor is displaced down the tubing with diesel oil as far
as practical without injecting inhibitor into the formation, and the well
is then shut in for about three hours. The well is returned to normal
2; p oduction while 50 to 100 ppm of an emulsion-breaker such as Nalfloc
VH35E is injected into the produced fluids upstream of the condensate
storage tank or separator. This emulsion-breaking treatment may be
necessary to prevent the formation of an emulsion or highly-condensed ~4
p-oduct, presumably caused by injection of an excess of the concentrated
inhibitor solution.
EXAMPLE VI
The runs in Table II demonstrate the effectiveness of
invention systems containing Duomeen C as the polyamine curing agent.
Duomeen C is described by the general formula R'NH(CH2)3NH2 wherein R'
represents straight chain hydrocarbon radicals containing on the average
12 to 14 carbon atoms. The laboratory runs were carried ou~ as described
in Example IV.
~7~5~
17
TABLE II
S 1 Aa Sol RbReaction Corrosion Pitting
Run (~ )Crude Oil Time (hrs) Rate (mpy) Index
8 0.45 0.13NBU 21 0.25 0.11
9 0.60 0.17Tor 22.5 0.25 0.1
0.45 0.13Tor 18 0.05 0.01 -_-
11 NOnee NOneeTord 22.5 0.45 0.2
ta) Solution A was prepared by mixing equal weights of xylene, methanol and
Duomeen C.
(b). Solution R was prepared by mixing lO parts by weight of ~pon 828 with 3
parts by weight of xylene.
tc) NBU represents North Burbank Unit crude oil used with NBU brine. A 50 mL
sample of oil was used with 9;0 mL of brine.
(d) Tor represents Tor crude oil used with synthetic North Sea water.
15 (e) In run 11 0.2 g of KP 2023 (a commercial inhibitor from Tretolite Corp.)
was used.
EXAMPLE VII
The runs in Table III demonstrate the effectiveness of
inventive systems containing varying ratios of the resin/hydrocarbon
solution (Solution R) and the amine/alcohol/hydrocarbon solution
(Solution A). Duomeen T was used as the polyamine curing agent. Duomeen
T ls described by the general formula R2NH(CH2)3NH2 wherein R2 represents
straight chain hydrocarbon radicals containing on the average 16 to 18
carbon atoms. The laboratory runs were carried out as described in
Example IV.
TABLE III
S 1 Aa Sol RbReaction Corrosion Pitting
Run (g) (~)Crude Oil Time thrs) Rate (mpy) Index
12 0.1 0~4NBUC 23 0.7 0.05
30 13 0.4 0.1NBU 23 2.6 0.1
14 0.2 0.3NBU 20.5 3.8 0.4
0.3 0.2 NBU 21 2.2 0.6
18
16 0.2 0.3 NBU 23.5 2.0 0.3
17 0.3 0.2 NBU 7 0.46 0.2
18 0.4 0.1 NBU 22 5.2 0.8
19 0.3 0.2 NBU 22 0.75 0.3
0.3 0.2 NBU 20 0.80 0.01
21 0.15 0.1 NBU 22.5 0.08 0.02
22 0.45 0.13 Tord 21 0.02 0
23 None None Tee 20.7 110 0
(a) The amine solution (Solution A) was prepared by mixing 1 part by
10 weight of the amine with 1 part by volume of alcohol and 1 part by
volume of xylene, e.g., ; g of Duomeen T with 5 mL of methanol and
5 mL of xylene.
(b) The resin solution (Solution R) was prepared by mixing 3 parts by
weight of the epoxy resin with 1 part by volume of xylene, e.g.,
15 30 g of Epon 828 with 10 mL of xylene.
(c) North Burbank Unit crude oil used with NBU brine.
(d~ Tor crude oil used with synthetic North Sea water.
(e) Teesside (mixed crude oil from North Sea complex) crude oil with
synthetic North Sea water.
