U.S. patent application number 10/259839 was filed with the patent office on 2003-05-01 for maintenance of oil production and refining equipment.
This patent application is currently assigned to Imperial Chemical Industries PLC. Invention is credited to Cox, Terence, Grainger, Neil, Scovell, Edward George.
Application Number | 20030079879 10/259839 |
Document ID | / |
Family ID | 9888838 |
Filed Date | 2003-05-01 |
United States Patent
Application |
20030079879 |
Kind Code |
A1 |
Grainger, Neil ; et
al. |
May 1, 2003 |
Maintenance of oil production and refining equipment
Abstract
The deposition of asphaltenes and/or petroleum waxes can be
inhibited and/or asphaltenes and/or petroleum waxes can be removed
from a well, pipe or vessel by contacting the asphaltene and/or
petroleum wax or the well pipe or vessel adjacent a location where
deposition of asphaltene and/or petroleum wax is expected, with a
solvent including at least one compound of the formula (I):
R.sup.1--(AO).sub.n--OOC--(CH.sub.2).sub.m--- Ph--(R.sup.2).sub.p
where R.sup.1 is a C.sub.1 to C.sub.20 hydrocarbyl group; AO is an
alkyleneoxy group and may vary along the (poly)alkyleneoxy chain; n
is 1 or from 1 to 100; m is 0, 1 or 2; and Ph is a phenyl group,
which may be substituted with groups (R.sup.2).sub.p where each
R.sup.2 is independently a C.sub.1 to C.sub.4 alkyl or alkoxy
group; and p is 0, 1 or 2, and subsequently removing the solvent
with softened, dissolved or dipersed asphaltenes and/or petroleum
waxes from the well, pipe or vessel.
Inventors: |
Grainger, Neil;
(Stockton-On-Tees, GB) ; Scovell, Edward George;
(Great Ayton, GB) ; Cox, Terence; (Saltburn,
GB) |
Correspondence
Address: |
PILLSBURY WINTHROP, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
Imperial Chemical Industries
PLC
London
GB
|
Family ID: |
9888838 |
Appl. No.: |
10/259839 |
Filed: |
September 30, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10259839 |
Sep 30, 2002 |
|
|
|
PCT/GB01/01382 |
Mar 28, 2001 |
|
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Current U.S.
Class: |
166/304 |
Current CPC
Class: |
C09K 8/524 20130101 |
Class at
Publication: |
166/304 |
International
Class: |
E21B 037/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2000 |
GB |
0007830.3 |
Claims
1 A method of removing from, or preventing or inhibiting the
deposition in, a well, pipe or vessel, of asphaltenes and/or
petroleum waxes which comprises contacting the asphaltene and/or
petroleum wax or the well pipe or vessel adjacent a location where
deposition of asphaltene and/or petroleum wax is expected, with a
solvent including at least one compound of the formula
(I):R.sup.1--(AO).sub.n--OOC--(CH.sub.2).sub.m--Ph--(R.sup-
.2).sub.p (I)where R.sup.1 is a C.sub.1 to C.sub.20 hydrocarbyl
group; AO is an alkyleneoxy group and may vary along the
(poly)alkyleneoxy chain; n 0 or from 1 to 100; m is 0, 1 or 2; and
Ph is a phenyl group, which may be substituted with groups
(R.sup.2).sub.p; where each R.sup.2 is independently a C.sub.1 to
C.sub.4 alkyl or alkoxy group; and p is 0, 1 or 2; and subsequently
removing the solvent with softened, dissolved or dispersed
asphaltenes and/or petroleum waxes from the well, pipe or
vessel:
2 A method as claimed in claim 1 wherein m, n and p are all 0.
3 A method as claimed in either claim 1 or claim 2 wherein R.sup.1
is a C.sub.3 to C.sub.5 branched alkyl group.
4 A method as claimed in any one of claims 1 to 3 wherein the
solvent is or includes iso-propyl benzoate.
5 A method as claimed in either claim 1 or claim 2 wherein R.sup.1
is a C8 to C20 branched and/or unsaturated alkyl or alkenyl
group.
6 A method as claimed in any one of claims 1 to 5 wherein the
asphaltene and/or petroleum wax is contacted with the solvent at a
superambient temperature.
7 A method as claimed in any one of claims 1 to 6 wherein the
solvent includes a dispersant for the asphaltene and/or petroleum
wax.
8 A method as claimed in any one of claims 1 to 7 to treat an oil
storage tank, vessel, or oil refinery pipework to remove deposits
of asphaltenes and/or petroleum waxes, in which a solvent including
a compound of the formula (I) as defined above, is introduced into
the tank, vessel or pipework at or adjacent the location of a
deposit of asphaltene and/or petroleum wax, and subsequently
softened dispersed or dissolved asphaltene and/or petroleum wax is
removed from the tank, vessel or pipework.
9 A method as claimed in any one of claims 1 to 7 to treat an oil
well to treat an oil well to remove a deposit of asphaltenes and/or
petroleum waxes, in which a solvent including a compound of the
formula (I) as defined above, is introduced into the oil well in or
adjacent to a deposit on a surface or in a rock formation and
subsequently softened dispersed or dissolved asphaltene and/or
petroleum wax is removed from the surface or formation.
10 A method as claimed in any one of claims 1 to 7 to treat an oil
well to inhibit or prevent the deposition of asphaltenes and/or
petroleum waxes, in which a stream of a solvent including a
compound of the formula (I) as defined above, is introduced into
the oil well in a location, particularly onto a surface or into a
rock formation, where deposition is expected thereby carrying away
asphaltenes and/or petroleum waxes before they are deposited on the
surface or in the formation.
Description
[0001] The present invention relates to the removal of deposits in
oil production and refining equipment and in particular to the
removal of deposits of asphaltene and/or petroleum waxes from such
equipment.
[0002] Crude petroleum is a mixture of many components which varies
depending on the source. Typically, it will include relatively low
molecular weight components, mostly hydrocarbons including
aliphatic and aromatic compounds. Relatively low molecular weight
products such as naphtha, gasoline, diesel or light fuel oil,
benzene and toluene are obtained mainly from these components.
Usually crude petroleum also includes materials having much higher
molecular weights including those known as asphaltenes and
petroleum waxes. Asphaltenes vary depending on the source of the
oil, but are typically polycyclic, usually aromatic or partly
aromatic, compounds, including heterocyclic especially N and S
atoms, and typically with multiple aliphatic substituent chains.
Asphaltenes are probably not truly soluble in most crude oils, but
are present as fine particles or platelets. Their dispersion in the
oil is aided by the presence of resinous materials usually called
maltenes and the relatively high temperatures of most oil producing
formations. Petroleum waxes are long chain, typically C.sub.15 to
C.sub.100, usually mainly open chain aliphatic compounds. They are
often described as paraffins and may be straight or branched chain
materials. Usually they are soluble in crude oil, particularly at
the temperatures of most oil producing formations.
[0003] In refining, the normal fate of these materials is to be
cracked into lower molecular weight compounds that then form part
of useful fractions in the products e.g. petroleum waxes can be
converted into useful shorter chain alkanes or alkenes, or to end
up as still bottoms e.g. as part of bitumenic products.
[0004] During production and processing, and in particular at
temperatures below those of the oil producing formation,
asphaltenes and petroleum waxes may separate from the bulk of the
oil and may become solidified as deposits on surfaces with which
they are in contact. These deposits can block the well or other
pipes through which the oil passes, or be deposits at the bottom of
separation vessels or storage tanks during production and the early
stages of refinery operations. It is important to remove such
deposits to avoid blockage of pipes and reduction in the capacity
of vessels.
[0005] Conventionally, aromatic solvent, such as xylene, sometimes
in combination with dispersants are used to remove both asphaltenes
and petroleum waxes from pipes and vessels. Such aromatic materials
are good solvents, but environmental considerations are leading to
pressure to reduce the proportion of such volatile aromatic
compounds used in industrial applications.
[0006] The present invention is based on the discovery that
certain, particularly alkyl, esters of aromatic carboxylic acids,
particularly benzoic acid, are very effective solvents for
materials deposited in oil recovery and refining equipment,
particularly asphaltenes and petroleum waxes and are
environmentally much less objectionable than the xylenic solvents
currently used for such purposes.
[0007] The present invention accordingly provides a method of
removing from or preventing or inhibiting the deposition in a well
pipe or vessel of asphaltenes and/or petroleum waxes which
comprises contacting the asphaltene and/or petroleum wax or the
well pipe or vessel adjacent a location where deposition of
asphaltene and/or petroleum wax is expected, with a solvent
including at least one compound of the formula (I):
R.sup.1--(AO).sub.n--OOC--(CH.sub.2).sub.m--Ph--(R.sup.2).sub.p
(I)
[0008] where
[0009] R.sup.1 is a C.sub.1 to C.sub.20 hydrocarbyl group,
particularly a C.sub.3 to C.sub.18 alkyl or alkenyl group;
[0010] AO is an alkyleneoxy group, particularly an ethyleneoxy or a
propyleneoxy group, and may vary along the (poly)alkyleneoxy
chain;
[0011] n 0 or from 1 to 100, desirably 0;
[0012] m is 0, 1 or 2, desirably 0; and
[0013] Ph is a phenyl group, which may be substituted with groups
(R.sup.2).sub.p; where
[0014] each R.sup.2 is independently a C.sub.1 to C.sub.4 alkyl or
alkoxy group; and p is 0, 1 or 2, desirably 0; and subsequently
removing the solvent with softened, dissolved or dispersed
asphaltenes and/or petroleum waxes from the well, pipe or
vessel.
[0015] In the compound of the formula (I) used in the invention
R.sup.1 can be an alkyl or alkenyl group. Alkyl groups have the
advantage that they are more stable, particularly to oxidation than
alkenyl groups, but alkenyl esters generally remain fluid at lower
temperatures than alkyl esters, especially for longer chain
materials. Desirably, an alkenyl group includes only a single
double bond as multiple unsaturation generally gives poor
stability. In removing asphaltenes, R.sup.1 is particularly a
relatively short chain, such as a C.sub.2 to C.sub.10 chain, for
example a C.sub.3 to C.sub.6, alkyl group. Desirably R.sup.1 is
branched e.g. it is an iso-propyl (prop-2-yl), sec-butyl
(but-2-yl), iso-butyl (2-methyl-prop1-yl), tert-butyl and/or
2-ethyl hexyl group, to reduce the ease with which the ester can be
hydrolysed. Esters with secondary alcohols are particularly useful
in this regard and R.sup.1 is thus especially a C.sub.3 to C.sub.5
secondary alkyl group and very desirably an iso-propyl group. Other
relatively short chain alkyl esters that can be used include ethyl,
nonyl, and other straight chain alkyl benzoates such as propyl,
butyl, pentyl and hexyl benzoates. A benefit of relatively short
chain esters is that they have low viscosity. In removing petroleum
waxes, longer chain esters may be desirable to improve the low
temperature solubility of the waxes in the solvent. Thus, R.sup.1
can be a C.sub.6 to C.sub.20, particularly a C.sub.8 to C.sub.18
alkyl or alkenyl group which may be straight chain e.g. as in mixed
esters such as (mixed C.sub.12/C.sub.13 alkyl) benzoate, or
branched e.g. as in 2-ethylhexyl or iso-nonyl or branched chain
C.sub.18 alkyl as in so-called iso-stearyl (actually a mixture of
mainly branched C.sub.14 to C.sub.22 alkyl with an average chain
length close to C.sub.18). Unsaturated longer chain groups include
oleyl. Where longer chain length groups are used, particularly
longer than C.sub.12, it is desirable that they are or include
branching and/or unsaturation and/or that mixtures of such esters
are used, as these promote liquid esters where straight chain
saturated ester compounds may be solid and thus more difficult to
use.
[0016] Although the carboxylic acid used in the ester can be a
dihydrocinnamic acid or a phenylacetic acid, it is very desirably a
benzoic acid i.e. desirably m is 0. Similarly, although the phenyl
ring of the acid may be substituted, it is desirable that it is
unsubstituted i.e. desirably p is 0. The esters used in the
invention may include a (poly)alkyleneoxy chain, (AO)n in formula
(I), between the carboxyl group and the group R.sup.1. When present
the (poly)alkyleneoxy chain is desirably a (poly)ethyleneoxy, a
(poly)propyleneoxy chain or a chain including both ethyleneoxy and
propyleneoxy residues. Generally, it is desirable not to include
such a chain in the ester i.e. desirably n is 0.
[0017] Particularly for dissolving asphaltenes, an especially
useful ester is iso-propyl benzoate and the invention specifically
includes a method of the invention in which the solvent is or
includes iso-propyl benzoate. Iso-propyl benzoate has a combination
of properties that make it exceptionally useful in the solvent
role. As a pure material, it has a wide liquid range having a high
boiling point (BP ca 219.degree. C.) and remaining fluid at
temperatures below normally expected environmental temperatures
(pour point <-60.degree. C.); it has a flash point (ca
99.degree. C.) so that it is classified as non-flammable and under
normal use conditions it has a low vapour pressure; it has a
density similar to that of water (1.008 kg.l.sup.-1 at 25.degree.
C.); and a low viscosity (2.32 cSt at 25.degree. C.; measured by
the U tube method, equivalent to 2.34 mPa.multidot.s).
[0018] By comparison other alkyl benzoates have viscosities (at
25.degree. C.) as follows:
[0019] ethyl benzoate: 1.9 cSt; 2-ethyl hexyl benzoate: 6.1 cSt;
nonyl benzoate: 7.5 cSt; (mixed
[0020] C.sub.12/C.sub.13 alkyl) benzoate: 14 cSt; and iso-stearyl
benzoate: 30 cSt.
[0021] To provide a balance of solubility for both asphaltene and
petroleum wax, mixed esters, having a variety of groups R.sup.1, or
blends of compounds of the formula (I), may be advantageous by
providing a combination of solvency properties matching
combinations of asphaltene and waxes. Such mixed esters of blends
can have the additional benefit that they are more liquid than
pure, especially linear saturated compounds of similar overall
R.sup.1 carbon number.
[0022] The solvent used in the method of the invention can be
wholly of one or more compounds of the formula (I), or it may
contain other solvents in admixture. Although xylenes can be
included it is unlikely that xylenes or other solvent including a
substantial proportion of aromatic hydrocarbons will be used as a
major component of any such mixed carrier fluid, because of its
adverse environmental impact. Mixtures with paraffinic liquid
solvents may improve the solubility of petroleum waxes, but are
likely to reduce the solubility of asphaltenes. Other solvents such
as water soluble alcohols may be included either as carriers for
additives (see below) or to improve compatibility with aqueous
materials in use. In such mixed solvents, the proportions used will
thus depend on the particular nature of material deposited in the
pipe or vessel, and probably on the balance and detailed
composition of asphaltenes and waxes. When mixtures are used,
compounds of the formula (I) will typically be present in at least
25%, usually at least 40%, more usually at least 50%, desirably at
least 60%, and particularly at least 75%, by weight of the total
carrier fluid used. When present, other solvent components will
desirably be used at level typically of from 1 to 75, usually 1 to
40%, more desirably 2 to 25, and particularly 5 to 15% by weight of
the total carrier fluid used.
[0023] To aid in dispersing the asphaltene and/or petroleum wax,
the solvent may include dispersants, particularly non-ionic
surfactants and dispersants such as alcohol alkoxylates; reaction
products between poly-iso-butylene succinic anhydrides (PIBSA's)
and alcohol alkoxylates, particularly C.sub.10 to C.sub.18 e.g.
C.sub.13 to C.sub.15 alcohol ethoxylates; reaction products between
PIBSA's and alkanolamines such as di- and tri-ethanolamine; and
sorbitan fatty acid esters, especially mono esters and particularly
esters of unsaturated fatty acids e.g. sorbitan mono-oleate;
sulphonic acid dispersants such as alkyl aryl sulphonic acids; or
resinous dispersants such as phenol formaldehyde resin dispersants
and ethylene vinyl acetate co-polymers. When used dispersants will
typically be included as from 1 to 40%, more usually 1 to 30% and
desirably from 1 to 20%, by weight of the solvent formulation.
[0024] Further additives such as fluid loss agents particularly
such as synthetic polymers such as polyacrylamides, polyacrylates,
polyamides and similar polymers (some of which can also function as
viscosity improving agents); corrosion inhibitors; demulsifiers;
scale inhibitors; oxygen scavengers; and other similar additive
materials, can be included in the solvent formulation used in the
invention. Particularly when such other additives are used, one or
more co-solvents may be used e.g. a water soluble alcohol, such as
propanol, particularly for use in systems operating in the presence
of water, and/or a dispersant for the additive may be included.
[0025] Generally, in production wells, the temperatures of the oil
bearing formation and the crude oil are often superambient
typically within the range 50 to 150.degree. C., particularly 60 to
120.degree. C. Asphaltene and/or waxes tend to be deposited at
temperatures below those of the formation, but generally within or
somewhat below the ranges given above, particularly in the range 40
to 110.degree. C. The compounds of the formula (I), particularly
iso-propyl benzoate, are better solvents for such materials at such
moderately elevated temperatures. Thus it may be advantageous to
operate at superambient temperature e.g. by heating the solvent,
either deliberately or e.g. in an oil well by contact with rock
formations at elevated temperatures, to improve solvent
performance. The temperature of pipes, tanks and refinery equipment
will generally be determined by the desired operating temperatures
(often linked to the feed temperature).
[0026] The equipment treated can be pipes such as pipes in oil well
structures, including the interior bore of well casings, pipelines,
including well head pipes, undersea pipes and pipework in
refineries; or vessels such as oil separators (to separate gas, oil
water and resinous phases); storage tanks, particularly near the
well head and at or near refineries; and refinery equipment. The
removal of deposits of asphaltenes and/or waxes can be by way of
introducing a body of solvent into contact with the deposit, if
necessary providing circulation or agitation of the solvent, and
removal of the softened, dissolved or dispersed deposit from the
equipment. In storage tanks and other refinery process locations,
the use of solvents to remove tank bottoms has the advantage of not
needing to open the tank for mechanical cleaning. The tank
contents, tank bottoms and/or solvent can be heated to aid
solubilisation and the tarry solid tank bottoms dispersed into the
solvent and usually added to a crude oil stream for further
refinery processing.
[0027] The invention includes a method of treating an oil storage
tank, vessel, or oil refinery pipework to remove deposits of
asphaltenes and/or petroleum waxes, in which a treatment material
including a compound of the formula (I) as defined above is
introduced into the tank, vessel or pipework at or adjacent the
location of a deposit of asphaltene and/or petroleum wax, and
subsequently softened dispersed or dissolved asphaltene and/or
petroleum wax is removed from the tank, vessel or pipework.
[0028] Particularly in oil wells, conventional techniques include
preventative application of solvents optionally including
dispersants with the aim of preventing flocculation and deposition
of asphaltenes and/or waxes. These methods generally involve
continuous treatment by pumping the treatment material down the
well e.g. using capillary tubing, or by a slip stream. This lays
down a thin layer of treatment material in the area where
deposition is considered likely and can effectively prevent
flocculation and deposition in the tubing and flow lines. They are
less effective in preventing deposition in the near wellbore area
e.g. within the production formation itself. in such cases the
treatment material needs to be placed in the formation where it can
inhibit solid deposition e.g. by squeezing the treatment material
into the formation.
[0029] The invention accordingly includes a method of treating an
oil well to remove a deposit of asphaltenes and/or petroleum waxes,
in which a solvent including a compound of the formula (I) as
defined above is introduced into the oil well in or adjacent to a
deposit on a surface or in a rock formation.
[0030] The invention further includes a method of treating an oil
well to inhibit or prevent the deposition of asphaltenes and/or
petroleum waxes, in which a stream of a treatment material
including a compound of the formula (I) as defined above is
introduced into the oil well in a location, particularly onto a
surface or into a rock formation, where deposition is expected
thereby carrying away asphaltenes and/or petroleum waxes before
they are deposited on the surface or in the formation.
[0031] The following Examples illustrate the invention. All parts
and percentages are by weight unless otherwise specified.
EXAMPLE 1
[0032] Scampton C4 crude oil was added to hexane to precipitate
asphaltene (the hexane dissolves asphaltene stabilising resins),
the upper solvent layer was removed and residual hexane allowed to
evaporate to give asphaltene as a viscous liquid residue. 5.2 g
iso-propyl benzoate solvent was added to 0.048 g of asphaltene and
after a few minutes at ambient temperature virtually all the
asphaltene had dissolved (a few very small particles of asphaltene
remained visible in the solution). The estimated (minimum)
solubility was calculated as ca 0.85% by weight.
EXAMPLE 1a
[0033] In a separate experiment, asphaltene was made as described
in Example 1 and its solubility was assessed in the various
solvents as decribed in Example 1. The solvents were ethyl
benzoate, iso-propyl benzoate, 2-ethyl hexyl benzoate, nonyl
benzoate, 3:1 by weight mixture of iso-propyl benzoate and nonyl
benzoate, (mixed C12/C13 alkyl) benzoate and iso-stearyl benzoate.
In each case the majority of the asphaltene dissolved but a few
very small particles remained visible in the solution.
EXAMPLE 2
[0034] About 0.025 g asphaltene (obtained as described in Example
1) was smeared onto a weighed 5 cm.times.1 cm rectangular mild
steel coupon and placed inside a weighed glass jar which was then
reweighed to give the amount of asphaltene by difference. About 2
ml solvent (weighed accurately) was added, the jar sealed and the
sealed jar placed on moving rollers, so that the metal coupon was
constantly covered with solvent at ambient temperature, for about
half an hour. The asphaltene was removed completely from the metal
coupon, indicating an effective minimum solubility of asphaltene in
the solvent of 1.3%. Similar results were obtained using xylene as
the solvent.
EXAMPLE 2a
[0035] In a separate experiment, Example 2 was repeated using the
solvents listed in Example 1a. In each case, the solvent removed
all of the asphaltene from the metal coupon.
EXAMPLE 3
[0036] Example 2 was repeated using about 0.18 g asphaltene and
about 0.5 ml iso-propyl benzoate. Again the solvent removed all the
asphaltene from the metal coupon.
EXAMPLE 3a
[0037] In a separate experiment, Example 3 was repeated using
different quantities: 0.4 g of asphaltene and 1 ml solvent, and the
solvents listed in Example 1a. In each case, at the end of the
rolling most of the asphaltene was removed, but small traces were
left adhering to the metal surface. The residues could not be
measured quantitatively, but visual inspection of the metal coupons
suggested that the ranking of the solvents in this test was (from
best to worst):
[0038] ethyl benzoate>nonyl benzoate>2-ethyl hexyl
benzoate>3:1 by weight mixture of iso-propyl benzoate and nonyl
benzoate>iso-propyl benzoate>(mixed C12/C13 alkyl)
benzoate>iso-stearyl benzoate.
EXAMPLE 4
[0039] The solubility of soft white paraffin wax [mp 49 to
59.degree. C.] in iso-propyl benzoate was measured. At ambient
temperature, the wax solubility was low (less than 1%), but on
warming to 50 to 60.degree. C. more than 60% by weight (on solvent)
of the wax could be dissolved.
EXAMPLE 4a
[0040] In a separate experiment, Example 4 was repeated to assess
the solubility of soft white paraffin wax in the solvents listed in
Example 1a. In each case the solubility appeared to be low at
ambient temperature but at 60.degree. C. more than 60% by weight of
wax cound be dissolved in each of the solvents.
EXAMPLE 5
[0041] Weighed metal coupons were coated with the wax described in
Example 4 by smearing the soft paraffin onto the coupon surface and
tested for wax removal by iso-propyl benzoate using the method
described in Example 2. The amount of wax was about 10% by weight
of the solvent. At ambient temperature, a small amount of wax was
removed giving a cloudy solution, but at 59.degree. C. all the wax
was readily removed from the coupon surface.
EXAMPLE 5a
[0042] In a separate experiment, Example 5 was repeated using soft
white paraffin wax and the solvents listed in Example 1a. Each of
the solvents removed all the wax at ambient temperature giving
cloudy solutions. Visual inspection of the extent of cloudiness
suggested that the ranking of the solvents in this test was (from
best to worst):
[0043] iso-stearyl benzoate.about.iso-stearyl benzoate>nonyl
benzoate.about.2-ethyl hexyl benzoate>ethyl
benzoate.about.iso-propyl benzoate.about.3:1 by weight mixture of
iso-propyl benzoate and nonyl benzoate.
* * * * *