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Description  |
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TECHNICAL FIELD
The present invention relates to solvents, particularly hydrocarbon
solvents, and which may be used particularly as oil and gas well site
operation fluid compositions or as industrial solvents, and to a method of
fire retarding such solvents.
BACKGROUND OF THE INVENTION
Many industrial and household organic solvents such as hydrocarbon solvents
manufactured under the trademark VARSOL of Imperial Oil, Calgary, Canada,
or such as turpentine, are made of petroleum distillates and are
frequently flammable. This evidently creates a hazard, particularly when
these solvents are used in oil and gas exploration as well site operation
fluids. Such well site operation fluids are pumped down the well, often
under high pressure, and are frequently used in the vicinity of equipment
with high temperature components, such as exhaust pipes. The use of
flammable organic solvents in these conditions and during transportation
evidently presents a hazard.
In particular, when light petroleum distillates (having primarily between 5
and 12 carbon atoms) are used for fracturing a well formation, the very
high pressures used can create a fire hazard. For example, among frac oils
used in industry, the following products of Dome Petroleum Limited of
Calgary, Alberta have densities (in kg/m.sup.3 at 15.degree. C.) and flash
points (flash points are Pensky Martens throughout this patent disclosure)
indicated: FRAC OIL 120 . . . 780, 10.degree. C.; FRAC OIL 200 . . . 785,
20.degree. C.; FRAC OIL 300 . . . 800, -3.degree. C.; FRAC OIL 500 . . .
798, 15.degree. C. SUPER FRAC.TM. made by Home Oil Company Limited of
Calgary, Alberta has a flash point of 15.degree. C. and density of 778.
Diesel P-40 has a flash point of 43.degree. C. and density of 820. These
fluids are being actively used as frac oils and the present invention is
believed to have utility for fire retarding them, and other similar
flammable organic solvents.
Substitution of other fluids for the volatile hydrocarbons, or alteration
of these fluids to make them non-flammable, cannot be reliably predicted
to work in part because of formation compatibility.
SUMMARY OF THE INVENTION
The inventors have proposed a way of fire retarding flammable and
combustible organic solvents such as the lighter hydrocarbons particularly
for use in wellsite operations, but also for use as industrial or
household solvents with low volume percentages of additive. These fluids
are non-aqueous.
The inventors have therefore proposed in one aspect of the invention a fire
retarded solvent composition for use as an oil and gas operation fluid,
the composition comprising at least one formation compatible combustible
organic solvent; and at least one brominated non-aromatic hydrocarbon
dissolved in the organic solvent in an amount sufficient to cause a
decrease in the flame propagation rate of the solvent composition.
The inventors found, moreover, that the fire retarded organic solvents thus
produced were compatible with most formations and would be superior to
existing drilling and service fluids.
In another aspect of the invention the inventors have proposed a fire
retarded solvent composition for use as an industrial or household
solvent, the composition comprising at least one flammable organic
solvent; and at least one brominated hydrocarbon dissolved in the organic
solvent in an amount sufficient to cause a decrease in the flame
propagation rate of the solvent composition.
In a still further aspect of the invention there is proposed a method of
fire retarding a flammable organic solvent to create a fire retarded
organic solvent, the method comprising the step of dissolving in the
flammable organic solvent a mixture of at least one brominated hydrocarbon
in an amount sufficient to decrease the flame propagation rate of the
organic solvent.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The brominated hydrocarbon should be selected to allow sufficient
concentration of additive in the vapour phase to result in a decrease in
the flame propagation rate of the composition and preferably increase the
flash point and fire point of the composition.
The preferred organic solvents for use as formation compatible oil and gas
well site operation fluids (sometimes referred to as operation fluids)
typically comprise combustible or flammable fluid hydrocarbons such as
light petroleum distillates (condensates), diesel and crude oil, these
being hydrocarbons having between 5 and 12 carbon atoms (C5-C12) and
traces of hydrocarbons having up to 30+ carbon atoms. The preferred cut is
about 100.degree. C. and greater. A good example is the Sundre C5+
condensate available from Trysol Inc. of Calgary, Alberta, Canada
distilled to 110.degree. C. It includes the following constituents (with
volume fraction in parentheses as determined by gas chromatography):
heptanes (0.0072), octanes (0.1191), nonanes (0.1028), decanes (0.1143),
undecanes (0.0927), dodecanes (0.0687), tridecanes (0.0598), tetradecanes
(0.0449), pentadecanes (0.0366) and smaller quantities of C.sub.16 +
alkanes, as well as smaller quantities of toluene (0.0131), benzene and
xylene (ethylbenzene, p+m-xylene 0.0371, o-xylene 0.0156, 1,2,4
trimethylbenzene 0.0158). However, actual aromatic content is believed to
be about 35% (the gas chromatography does not distinguish between some
aromatics and alkanes). The preferred organic solvent primarily includes a
mixture of alkanes and aromatics.
These organic solvents typically have a specific gravity of about 0.8, so
that when mixed with no more than about 5% by volume of halogenated
hydrocarbon as described in this disclosure, the fire retarded solvent
will typically have a specific gravity of less than 0.9. Thus, fluid
condensate (98.degree. C. cut, s.g. .7950) may be mixed with up to 5%
dibromomethane (b.p. 96.degree.-98.degree. C.) to produce an organic
solvent with a specific gravity of up to 0.8794. Fluid condensates with
which the mixture of brominated hydrocarbon may be added to improve fire
retardancy include C4 condensate from the Coleman field in Alberta,
Canada, with s.g. of 0.800, or C6+ condensate from the Harmattan Area Gas
Plant in Alberta, Canada, with s.g. of about 0.765. Useful flammable
organic solvents include hydrocarbon solvents manufactured under the
trademark VARSOL of Imperial Oil Canada.
When the flammable organic solvent is used in well site operations, it is
preferred that the organic solvent include toluene, ethylbenzene,
para-xylene, meta-xylene, ortho-xylene as well as other mono-, di- and
tri-aromatics to assist in solvating waxes and asphaltenes. In particular,
if a particular condensate from a refinery is found after analysis and
testing to assist in asphaltene precipitation, then xylene (preferably
from a 130.degree. C. to 145.degree. C. cut) may be added to ensure
compatibility of the organic solvent with the reservoir. The xylene may be
obtained by removing a xylene rich cut from for example the Sundre feed
stock described above and further distilling it to produce a cut that is
richer in xylene. It is desirable to ensure that the percentage of
aromatics in the solvent be kept above about 30% since otherwise there is
increasing danger of asphaltene precipitation.
Other organic solvents for use in wells should be formation compatible and
include hydrocarbon derivatives such as alcohols, ketones, esters, ethers,
and terpenes.
Due to restrictions on the commercial use of fully brominated hydrocarbons,
these are not believed to have utility in all places and at all times, and
thus the emphasis in this patent disclosure is on the properties of
partially brominated hydrocarbons whose utility is believed to be of
greatest use in the compositions and methods of the invention.
Nonetheless, the fire retardant properties of fully brominated
hydrocarbons are desirable properties so that where permitted by law they
might be used. Also, other brominated hydrocarbons can be highly toxic,
thus for example, it is not recommended to use bromomethane. Brominated
hydrocarbons in particular have surprising utility when used in or as a
formation compatible oil and gas well site operation fluid. The bromines
provide good fire retardance in small quantities. Bromochloromethane may
be used as the brominated hydrocarbon, and the addition of the chlorine,
by lowering the boiling point of the additive, is believed to assist in
the fire retardant properties of the composition.
Other halogens may have utility in some circumstances, but they are
presently expensive to manufacture and therefore are not preferred.
Dibromomethane is believed to be preferred. Test results show a desirable
composition would include about up to 5% of dibromomethane when added to a
98.degree. C. cut fluid condensate, yielding a specific gravity up to
0.8794.
Other brominated hydrocarbons believed to have utility as good fire
retardants, while being formation compatible, include dibromoethane (s.g.
2.18, b.p. 131.degree.-132.degree. C.), chlorodibromomethane (s.g. 2.451,
b.p. 119.degree.-120.degree. C.), bromochloromethane (s.g. 1.991, b.p.
68.degree. C.), and 1,2dibromoethylene (s.g. 2.246, b.p. 110.degree. C.).
Alkanes are believed to be most useful because they may be economically
produced. Further, for oil and gas operations it is believed to be
inadvisable to use brominated aromatics, particularly aromatics with an
oxygen bridge, since where there is sulphur in the well formation fluid,
the sulphur may react with the bromine and produce corrosive compounds
(such as HBr). However, such compounds may still have utility where the
solvent is not being used in oil and gas operations or where hydrogen
sulphide is not present.
The inventors have also found, unexpectedly, that dibromodifluoromethane
can assist in causing asphaltene precipitation in some reservoir fluids.
It is believed that this is due to the presence of the fluorine in the
halocarbon. This is surprising because the halogen analog carbon
tetrachloride is compatible with most reservoirs, as is dibromomethane.
The precipitation of asphaltenes can be very damaging to formations, and
thus it is believed that use of fluorinated hydrocarbons is not in general
desirable.
In wells with low downhole pressures, the composition of the present
invention has particular utility in that heavy fluids cannot be used.
However, a mixture of condensate and brominated hydrocarbon may be readily
prepared that has low density.
The composition of the present invention also helps to reduce the viscosity
of vegetable oil formation compatible oil and gas well site operation
fluids. Mixtures of less than 5% halogenated hydrocarbon by volume in the
vegetable oil can give the vegetable oil desirable viscosity.
The composition of the present invention may also be used to fire retard
operation fluids during transportation and storage.
It will be understood that not all operation fluids will be compatible with
every well, so that care must be taken to select the appropriate mixture
of operation fluids and brominated hydrocarbons for the well of concern.
The brominated hydrocarbons noted here, particularly dibromomethane and
chlorobromomethane, or mixtures of them, may also be used to fire retard
solvents, particularly hydrocarbon solvents that are derived from
petroleum refining such as aromatics and naphthalenes. These are also
useful frac fluids. For example, in the case of VARSOL.sup..TM., a
variable composition of aromatics, naphthalenes and chain saturates,
addition of less than 1% dibromomethane and chlorobromomethane in a
mixture is believed to be sufficient for fire retardance. Similarly, such
a low percentage of brominated hydrocarbon mixed with diesel, or another
fluid petroleum distillate cut above about 100.degree. C., is believed to
provide good fire retardancy. A combination of dibromomethane and
chlorobromomethane is also believed to be useful when used in combination
since the dibromomethane boils at 98.degree. C. and the
chlorobromomethane, since it boils at 66.degree. C., this reduces the
average boiling point of the additive. In the case of the use of the
organic solvent as a commercial or consumer solvent, then fluorinated
hydrocarbons may be used such as dibromodifluoromethane (b.p.
22.degree.-23.degree. C.), dibromodifluoroethane (s.g.2.224),
1,2,dibromo-1,1-difluoroethane (b.p. 93.degree.-94.degree. C.),
chlorodibromofluoromethane (b.p. 79.degree.-80.degree. C.) and
1,2dibromotetrafluoroethane (s.g.2.175, b.p. 47.degree. C.).
Useful commercial solvents in which the brominated hydrocarbons are
believed to be miscible and to produce good fire retardancy include
acetone, amyl acetate, amyl alcohol, n-amylamine, n-amylbenzene,
n-amylchloride, benzene, benzyl chloride, bromoform, bromo-m-xylene,
o-bromotoluene, n-butane, butanol, carbon tetrachloride, chloroform,
cumene, naphthene, cyclohexane, dimethyl ether, dipentene, ethane,
ethanol, ethylbenzene, ethyl bromide, ethyl chloride, ethylene, ethylene
dibromide, ethylene dichloride, ethylene glycol monoethyl, ethyl ether,
n-hexane, isopropanol, isopropyl ether, methane, methanol,
methylcyclohexane, methyl formate, naphthalene, acetone,
pentachloroethane, pentane, perchloroethylene, phenol, phenyl methyl
ether, propane, propanol, toluene and xylene.
EXAMPLES
Tests conducted on diesel and other organic solvents (diesel, San Frac Oil,
Arosol HTU available from Gulf Oil, Calgary, Canada, FRACOIL 200,
SUPERFRAC OIL and BP PC condensate, available from British petroleum,
Calgary, Canada) with various combinations of brominated hydrocarbons
(CF.sub.2 Br.sub.2 and CH.sub.2 Br.sub.2) showed good solubility of the
additive in the organic solvent, and compatibility with current gellation
processes. Flash points tests showed flash points of various mixtures of
organic solvents with brominated hydrocarbons of the invention as shown in
the following table (percentages are volume percentages):
______________________________________
FLASH FIRE
PT PT
ASTM ASTM
FLUID D-93 D-92
______________________________________
DIESEL (NO ADDITIVE)
45 63
DIESEL + 2.5% CH.sub.2 Br.sub.2
48 108
DIESEL + 1% CF.sub.2 Br.sub.2 +
>100 130
2% CH.sub.2 Br.sub.2
DIESEL + 2% CF.sub.2 Br.sub.2 +
>100 130
1% CH.sub.2 Br.sub.2
DIESEL + .5% CF.sub.2 Br.sub.2 +
>100 83
.5% CH.sub.2 Br.sub.2
DIESEL + 1% CH.sub.2 Br.sub.2 +
>100
1% CH.sub.2 BrCl
DIESEL + .5% CH.sub.2 Br.sub.2 +
>100
.5% CH.sub.2 BrCl
DIESEL + 2.5% CH.sub.2 Br.sub.2 +
>100
2.5% CH.sub.2 BrCl
TURPENTINE 36 (56) 56
TURPENTINE + 5% CH.sub.2 Br.sub.2
>100 (60) 99
TURPENTINE + 5% CF.sub.2 Br.sub.2
>100 (61) 63
TURPENTINE + 2.5% >100 (60) 62
CH.sub.2 Br.sub.2 + 2.5% CF.sub.2 Br.sub.2
VARSOL .TM. 46 55
VARSOL .TM. + 5% CH.sub.2 Br.sub.2
>100 (58) 77
VARSOL .TM. + 5% CF.sub.2 Br.sub.2
>100 (67) 81
VARSOL .TM. + 2.5% CH.sub.2 Br.sub.2 +
>100 (65) 74
2.5% CF.sub.2 Br.sub.2
PAINT THINNER (P.T.)
46 52
P.T. + 5% CH.sub.2 Br.sub.2
>100 (61) 75
P.T. + 5% CF.sub.2 Br.sub.2
>100 (60) 72
P.T. + 2.5% CH.sub.2 Br.sub.2 +
>100 (61) 82
2.5% CF.sub.2 Br.sub.2
TOLUENE 8 (11) 17
TOLUENE + 5% CH.sub.2 Br.sub.2
10 (24) 60
TOLUENE + 5% CF.sub.2 Br.sub.2
N/A (23) 40
TOLUENE + 2.5% CH.sub.2 Br.sub.2 +
N/A (24) 40
2.5% CF.sub.2 Br.sub.2
XYLENE 25 (34) 38
XYLENE + 5% CH.sub.2 Br.sub.2
29 (39) 80
XYLENE + 5% CF.sub.2 Br.sub.2
>100 (45) 71
XYLENE + 2.5% CH.sub.2 Br.sub.2 +
>100 (39) 70
2.5% CF.sub.2 Br.sub.2
METHANOL 12 | | |
