Note: Descriptions are shown in the official language in which they were submitted.
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Method for Up~radin Heavy and Semi-Heavy
In investigating extraction of oil or oil precursor matter from coal, oil
shales, bitumen and
heavy oils with supercritical or near-supercritical water we observed that
conjoint use of
carbon monoxide can lead to significant upgrading of the precursor material
during
extraction. Such upgrading manifested itself specifically in the class
composition of the
recovered organic matter, i.e., higher proportions of aliphatics and
correspondingly lowered
presence of aromatics and so-called upolar" compounds carrying heteroatoms
such as
oxygen, nitrogen and/or sulfur.
An example, which relates to extraction of a Fort McMurray (Alberta) high-
grade" oil
sand,l is shown in the table below:
' In jurisdictions other than Alberta, this resource is commonly referred to
as tar sand or
bituminous sand.
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1 2 3 4
feed 36 11 37 16
extracted with H20 at
400°C/14.0 M Pa 30 19 39 12
400°C/17.9 MPa 24 24 40 12
400°C/24.5 MPa 28 27 43 2
extracted with H20 + CO~a~ at
400°C/14.0 MPa 74 5 19 2
400°C/17.9 MPa 72 5 21 2
400°C/24.5 Mpa 66 5 27 2
H20/CO mole ratios in these runs were 1.05, 1.3 and 2.2 respectively.
1: aliphatics 2: aromatics 3: polar compounds 4: asphaltenes
Recovery of hydrocarbon material, which depended on sweep rates and on the
disposition
of the test sample in the reactor, ranged between ~80 and 90 wt.% of the
bitumen in
place.
The evidence at hand permits the conjecture that such compositional shifts --
which are
associated with concurrent reductions of the average molecular weight of the
recovered
hydrocarbon material (and therefore lower viscosity) -- accrue from a complex
reaction
sequence that entails
[1] thermally driven homolytic and/or hydrolytic bond scission -- in
particular
scission of carbon-carbon bonds within the constituent molecules, and
consequent formation of short-lived radical species which would, in the
absence of modifiers, randomly recombine without substantially changing the
molecular weights of the precursors;
[2] some interaction of radical species with H20 to generate alcohols by
reactions
such as
R ~ CH3 + H20 ~ R ~ CH20H . . . . . [1]
and
[3] an in situ shift reaction
CO + H20 ~ H2 + C02 . . . . . . . . . . [2]
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which generates elemental hydrogen and can thereby (i) stabilize radical
species before
they can recombine or interact with H20 or (ii) reduce alcohols by, in effect,
reversing
reaction [1].
These or similar chemical processes make conjoint use of supercritical (or
near-
supercritical) H20 and CO practical means for recovering fossil hydrocarbons
such as heavy
oils, bitumens and heavy oil precursors from oil shales. The following
examples may serve
to illustrate this form of recovery.
1. One procedure, specifically but not exclusively designed for in-situ
recovery of heavy
oils, entails
(a) completing two suitably spaced small diameter boreholes (I and II)
vertically
into the payzone;
(b) where necessary, enhancing communication between these holes by hydraulic
or electrical fracturing of the formation in order to establish suitable
communication;
(c) through one hole (I) injecting supercritical (or near-supercritical) H20
into the
formation at temperatures in the range of 400-450°C (~ 750-840°~
and
pressures between 14 and 21 Mpa (~ 2000-3000 psi);
(d) through the other hole (II) producing the steam with its load of extracted
oil;
and
(e) at a convenient (surface or downhole) location passing the produced stream
through a pressure letdown vessel in which lower pressures and/or lower
temperatures cause the oil and coproduced inorganic matter (if any) to fall
out,
i.e., to spontaneously separate from the steam.
Before processing the separated crude letdown oil (e.g., by secondary
hydrogenation
or coking) it can then, where necessary, be freed of inorganic matter by
filtration or
use of an antisolvent. Recovered steam and condensed H20 are then prepared for
recycling to the injection hole.
Bitumens and related asphaltics, which from a production standpoint differ
from
heavy oils only in specific gravities, can be recovered from oil sands (or
their
equivalents) and processed by substantially the same steps.
1A. Where the permeability of the prospective payzone and/or the effective
floor and roof
of that zone is low, the objectives of the procedure outlined in #1 can be
attained
by
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(a) completing a directional (substantially horizontal) borehole over an
appropriate
distance;
(b) fracturing the stata hydraulically;
(c) where necessary, lining the borehole with a perforated casing; and
(d) injecting supercritical (or near-supercritical) HZO and CO at 400-
450°C while
producing from the other end of the borehole.
2. Another example of implementing recovery -- this form being particularly
suitable or
in-situ extraction of organic matter from very dense envelopes such as oil
shales, but
not limited to such strata -- involves
(a) creating an underground retort by completing a borehole of suitable
diameter
vertically into the payzone;
(b) fragmenting the formation near the bottom of the hole, e.g., by suitably
placed
explosive charges;
(c) injecting supercritical (or near-supercritical) H20 and CO at 400-
450°C and
14-21 Mpa;
(d) producing the steam with its load of extracted organic matter through an
off-take pipe concentrically positioned within the borehole so that the
annulus
between them can serve as the injection hole; and
(e) proceeding as in example #1.
Subsequent coking then allows upgrading of the organic material and concurrent
separation from entrained inorganic matter.
An essential feature of the technique illustrated by examples #1, 1A and 2 is
(i) the use of near-supercritical steam as 'solvent' and
(ii) uninterrupted 'sweeping' of the pay zone during the production cycle by
continuous injection of H20 and CO as well as continuous recovery (and
processing) of the product stream.
However, fundamental to satisfactory operation of the schemes exemplified in
#1, 1A and
2 is recognition that optimum injection temperatures and pressures are site-
specific and
depend upon the thermal characteristics of the strata from which the
hydrocarbon is to be
recovered. Our experience to date suggests that optimum temperatures in the
pay zone
will generally but not always lie between 400 and 425°C and optimum
pressures will range
from 14 to 17.5 Mpa.
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3. An alternative method for recovering fossil hydrocarbon material with
supercritical (or
near-supercritical) H20 and CO entails processing in a suitably constructed
and sized
surface reactor. In such an operation, the feed -- mined oil sand, oil shale
or coal --
would be coarsely crushed before transfer to the pressure vessel, but all
other steps
correspond to those outlined above.
Our laboratory test on bitumen extraction by supercritical H20 clearly
suggests that
removal of residual bitumen from, e.g., hot water extraction process tailings,
by such
extraction in a surface facility holds commercial potential. Major benefits
would lie
in accelerated settling of ponded tailings and, consepuently, in greatly
enhanced
capability for recycling process water.
4. A further aspect of conjoint use of H20 and CO at 400-425°C and 14-
21 Mpa is
accelerated partial upgrading of heavy oils, accomplished in situ (as in
examples #1,
1A and 2) or surface reactor operations (as in #3) by entraining a catalyst
such as
iron oxide in the H20/CO stream. Such catalysts are often available as a
"throw-away" product from other processes.
5. In appropriate adapted form, the procedure outlined in #3 could also offer
means
for rendering toxic or otherwise noxious organic wastes substantially harmless
by
eliminating heteroatom configurations that endow them with unacceptable
characteristics and thereby converting them into hydrocarbons. For that
purpose,
interaction with H20 and CO would optimally proceed at 450-600°C and >
17.5
Mpa.
SIGNED at Calgary, SIGNED at Calgary,
this 11t" day of August, 1998. 11'" day of August, 1998.
105, 11660 - 79 Avenue 1144 Edgemont Road N.W.
Edmonton, Alberta T6G OP7 Calgary, Alberta T3A 2J8
