Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
The present invention relates to petroleum refining
and, more particularly, to petroleum distillation and/or cracking
conducted in a unit disposed in a geothermally heated subsurface
zone.
DESCRIPTION OF THE PRIOR ART
Petroleum is a complex liquid mixture of organic com-
pounds obtained from certain points in the upper strata of the
earth. The chief components of this very complex mixture are
hydrocarbonds. Petroleum is refined that is separated into
useful products by dividing the petroleum into fractions of
different boiling ranges by distillation and by special treat-
ments of the fraction to remove undesirable components. The
main fractions are gas, light, naphtha (240F), heavy naphtha
(340F), Kerosene (420F), gas oil (50QF), paraffin (600F)
and high boiling residue (800F). The residue can be dis-
tilled under reduced pressure for the recovery of an overhead
product suitable for refining into lubricating oils or for
use of a feed stock for cracking or used directly
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as fuel. Thermal cracking results not only in smaller molecules
of higher volatility, but also in the production of olefins and
aromatic hydrocarbons. The cracking process results in not only
a higher yield of gasoline but also in a product with higher octane
number. Thermal cracking is carried out at temperatures between
400 and 600C at increased pressure of 175-250 psi. The amount
of material in the liquid phase is increased. The cracking reac-
tion is accelerated in presence of solid catalyst such as natural
clays or synthetic aluminum silicate mixtures and catalytic
cracXing can be carried out at 450-500C, at relatively low
pressures of 10-50 psi.
Though both of these processes result in the conversion
of a larger portion of the petroleum to commercially useful fuels,
both processes suffer an energy penalty in requiring an addition
of significant amounts of high thermal energies to the crude oil
to effect conversion.
SUMMARY OF THE INVENTION
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It has ~ been discovered in accordance with this
invention that crude petroleum oil can be distilled into fractions
and/or cracked to form gas or lighter oil fractions by pumping the
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oil into a refining unit disposed in hot subsurface gas tho~mal
zone. The upwardly rising product gases and distillate fractions
heat the downwardly flowing crude oil. The refining un~t6 is
housed in a cased geothermal well and in the portion of the casing
disposed in a hot geothermal zone having a temperature of at least
300, preferably 500-800 or higher. Means for delivering crude
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oil to the rofin~r~y unit are provided and li~uid products and gas
outlets are provided to recover the desired fractions. The
viscous bottom residue oil can be removed to the surface for
further treatment or use as fuel or cracked therein to lighter
li~uid and/or gaseous fuel products.
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~ The process of this invention can be practiced close to
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the source of crude oil, if~ geothermal zone having an appropriate
temperature is located nearby. If not, the crude oil can be
delivered to a location where high geothermal temperatures are
reached in fairly shallow depths. Other aspects of the invention
relate to generation of steam within the geothermal well for use
in the distillation reaction either directly or to remove certain
molecules from the petroleum feed or to aid in delivering portions
of the fractions to the surface.
These and many other objects and attendant advantages of
the invention will become apparent as the invention becomes better
understood_ ~ reference to the following detailed description
when considered in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic view, partly in section of a
first embodiment of a geothermal petroleum refining distillation
system;
Fig. 2 is a schematic view partly in section of a pipe
still embodiment of a geothermal petroleum refining unit;
Fig. 3 is a schematic view partly in section of a
geothermal petroleum refining system utilizing geothermal steam;
Fig. 4 is a schema~ic view of an embodiment in which
water is injected into the geothermal zone to generate steam; and
Fig. 5 is a schematic view of a geothermal petroleum
refining system incorporating catalytic cracking ass~mhly.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Xeferring now to Figure 1, the geothermal petroleum
refining system of the inventîon generally includes a geothermal
well 10 extending from the surfa~e into a geothermal zone 13
having a temperature of at least 300F, preferably at least 500F.
The zone 13 is preferably a wet geothermal zone containing pressurized
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hot water which acts as an efficient thermal carrier for the
geothermal heat. Wet pressurized zones are usually disposed
~etween impervious layers 17, 19, such as shale.
The normal geothermal gradient is about 3C for each
330 feet of depth. Abnormal gradients occur in many instances
due to faulting, volcanism, metamorphosis, chemical and radio-
logical action. Petroleum fields are entrapments usually asso-
ciated with faults in which the hot magna invades upper strata
providing hot geothermal temperatures close to the surface.
Thus, it is very likely that a feasible geothermal refining
system can be located near to a petroleum production field
minimizing storaqe and transportation costs.
The well 10 includes an outer layer 27, suitably cement,
which seals the surfaces of the well extending through porous
stxata 11. The well 10 is usually provided with a metal
casing 12 which is terminated with a plug 14 and a well head 22.
The lower portion of the well 10 extending into the geothermal
zone 13 includes a refining section 18 for receiving a flow
of crude oil. The crude oil is supplied through inlet 20 and
flows through the annulus 24 surrounding vapor duct 16 and
through opening 21 into the refining section 18 to form a body
of oil 59. As the oil is geothermally heated, vapors rise
through duct 16 and heat the downwardly flowing oil in annulus
24 and proceed to the surface for further treatment such as
fractionation. Non-boiling residue is removed through pipe
30 by ~eans of pump 31. If the temperature in the unit 18 is
high, suitably above 700F, some thermal cracking may occur.
In the geothermal refining unit of Figure 2 distillation
of the crude oil S9 is conducted by means of a pipe still 32.
The well head 42 contains ports for sealingly receiving a water
conduit 34, crude conduit 36 and vapor stack 47 communicating
with outlet 40. The outlet 35 of the water conduit extends
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into a steam boiler section 37. The steam generated by the
geothermal heat from zone 13 enters the pipe still and heats
the body of oil 59 to vaporize`fractions having a boiling point
below the temperature in the zone 13. The still 32 may have
S a steam outlet 44. The steam injected into the oil 59 can
extract some miscible components by steam distillation and
serves to entrain higher boiling residue components. The
generated vapors and the steam and entrained liquid rise
through the annulus 38 through outlet 40 and stack 47 into
separator 46 from which steam and water are removed and then
into fractionator-condenser 48.
Referring now to Figure 3, generation of steam by injecting
water from the surface may not be reguired if the bottom portion
of well 10 containing the distillation unit is disposed in a
wet, pressurized ~eothermal zone 50. Geothermal heat and geo-
thermal steam from the zone entering perforations 52 distill
fractions from the oil 59. The distilled vapors 55 heat the
downwardly falling crude in cond~it 54 and rise and are recovered
through vapor outlet 56 provided in well head 58.
In the case a dry, fractured geothermal zone, the steam
necessary for distillation and to aid in removing residue can
be provided by injecting water into the zone to generate steam.
The water can be injected adjacent the well into the zone below
the end of the casing or can be injected through the plug.
~eferring now to Figure 4, a central water injection
pipe 64 is surrounded with a crude delivery pipe 68 extends
through the oil 59 in the refining section and then through
the plug 14 surrounded by steam delivery conduit 76. The
lower end of pipe 64 is below the end of conduit 76. Crude
is delivered to inlet 70 and flows through the annulus of the
the concentric assembly of pipes 64, 66 and out outlet 72 into
the refining unit to form the distillable body of oil 59. The
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water injected into the lower portion of zone 60 is vaporizedto form steam which flows through annulus 74, into the body
of oil 59, causes distillation thereof to form vapors 55 which
are recovered through outlet 62.
Though some cracking may occur due to thermal causes,
additional cracking of the larger, less volatile components
of the crude can be effected by disposing a cracking catalyst
within the portion of the geothermal well within the hot zone
13.
Referring now to Figure 5, a perforated basket 80 con-
taining solid, particulate cracking catalyst 82 is disposed
within the zone 13. The walls 84 of the basket contain per-
forations 86. As the oil 59 enters the perforations and con-
tacts the particles 82 of catalyst carbon-carbon bonds are
broken to form smaller more volatile molecules. The distilled
vapors rise through the annular space in casing 12, heat the
crude in pipe 88 and are recovered through outlet 90 for fur-
ther processing. The basket 90 can be removed periodically
to replace or regenerate the catalyst or the crude flow to the
well can be interrupted to regenerate the catalyst thermally
within the zone 13 to burn off coke deposits or by flushing
regenerating fluids onto the catalyst through conduit 88.
Cracking catalysts are generally natural clays or synthetic
alumina-silica mixtures. Catalytic cracking can be carried
out at relatively low pressures of 10-50 psi and at temper-
atures as low as 450 to 500F. Cracking also increases octane
number due to the formation of olefins and aromatic hydrocar-
bons. Straight run gasoline can be run through the unit of
Figure 5 to increase octane number, an operation known as
reforming.
Grade #2 fuel oil is the designation give~ to the heating
oil commonly used for home heating and much commercial space
heating. This is a distillate product, normally fractionated
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to a boiling range of 350 degrees to 650 degrees F, (177 to
343 degrees C). Texas, Mississippi, New Mexico and
Louisiana crude oils have API gravities between approximately
. 35 and 40 (American Petroleum Institute-API) and yields from
25 to 35 percent gasoline (this fraction boiling below about
400 degree F.) by volume.
Major fractions which are subject to later separations
and ideal for geothermal energy distillation as envisioned in
this invention are: (1) a light straight-run fraction, con-
sisting of primarily C4, C5 and C6 hydrocarbons and lighter
gaseous hydrocarbons dissolved in the crude; (2) a naphtha
fraction having a nominal boiling range of 200 to 400 degrees
F.; (3) light distillate with a boiling range of 400 to 650
degrees F.
It is to be understood that only preferred embodiments
of the invention have been described and that numerous substi-
tutions, modifications and alterations are permissible without
departing from the spirit and scope of the invention as defined
in the following claims.
