CA2316084C - Method for extracting and upgrading of heavy and semi-heavy oils and bitumens - Google Patents

Abstract

A method and apparatus for optimal heavy oil or hydrocarbon upgrading or extraction using supercritical or near-supercritical water is provided by an appropriately designed and scaled single-chamber flow-through reactor, and with in-reactor residence times of no greater than 60 seconds, at temperatures in the range of 300°C to 450°C (preferably between 300°C and 380°C), and pressures between 1000-3000 psi or 7 to 21 MPa. The addition of carbon monoxide to the reactor can in some cases improve the resulting products.

Description

METHOD FOR EXTRACTING AND UPGRADING OF HEAVY AND SEMI-HEAVY
OILS AND BITUMENS
FIELD OF THE INVENTION
[0001 ] Selective extraction of components from a raw feedstock with a supercritical fluid - in effect, a fractionation of the feed - is well known and at present widely used in commercial production of pharmaceuticals, perfumes and spices as well as in the manufacture of prepared foodstuffs such as caffeine-free coffee. The extractor fluids deployed in these operations are usually supercritical carbon dioxide or propane.

[0002] More recently substantial R & D has centered on the use of nominally supercritical water (SCW) for generating from coal, oil shales and oil sands relatively low-molecular-weight oils or oil precursors that are amenable to conventional upgrading or refining techniques (cite 1, 2, 3). Some attention has likewise been given to the destruction of noxious or hazardous wastes by interaction with this medium (cite 4).

[0003] We have found that, like heavier fossil hydrocarbons, heavy oils can also be upgraded to refmable crude oils by interaction with supercritical water. But the extent to which the average molecular size, and hence the viscosity of these feedstocks, is reduced is critically dependent on operating conditions, and these in turn, are directly governed by the chemical reactions that accompany processing.

[0004] This invention has to do with a novel method of processing heavier fossil hydrocarbons or heavy oils, utilizing nominally supercritical water to obtain lower viscosity hydrocarbons with notably less coke and with notably fewer contaminants.
BACKGROUND OF THE INVENTION

[0005] It is known to use supercritical water in processes which attempt to upgrade complex hydrocarbons, notably bitumen and heavy oils. Various processes are noted below, but each has drawbacks, described below, at least some of which this invention overcomes.
PRIOR ART

[0006] Brons (LJS 5,695,632) deals with removal of sulfur and other organically bound heteroatoms and metals from heavy oil. The heavy oil is contacted with aqueous sodium hydroxide and subsequently water (and optionally hydrogen) at temperatures in the range 380°C-450°C, to produce sodium sulfide, which is subsequently removed from the mixture. Reaction times are about 5 minutes to 3 hours. When hydrogen is added to the system, pressures range from 50-700 psi; otherwise, pressure is not defined.
'fhe teaching of the use of water at temperatures which may be near tc~ supercritical to upgrade heavy oil by removal of sulfur and metals is of some interest.

[0007] Brons (CTS 5,693,632) is liruited to removal of undesirable components (namely organically bound sulfur, heteroatoms and m~:tals) from a heavy oil feedstoek. The Brons invention does not deal with the upgrading of h~;avy oil to unrefined crude oil quality, especially with regard to favourable ehang~es in viscosity and density.
Moreover, sodium sulfide is corrosive and diffcult to handle. Handli~n.g of hydrogen at high pressures and temperatures is also difficult. There aro therefore limits to the usefulness of Brons's (US
5,695,632) invention as disclosed.
~OOOSj Braris (US 5,635,0S6) is similar to Broils (US 5,695,632) in that it deals with removal. of a class of organically-bound sulfhr and metals from heavy oil.
This patent specifies a different class of such components. Operating conditiotas and methodologies are similar to those specified in Brons (CTS 5,695,632). A.~ain, water is supplied together with a transition metal in an intermEdiate step t0 modify the end-stage. The disclosure notes, as an aside, that the asphaltene content, density and viscosity may also be reduced using the water-with-transitional-metal process. Brons (US 5,635,055) does nest provide for any specific pressure range, and emphasizes removal of undesirable components.
[0009] As in Brons (US 5,895,632), the handling of sodium sulfide and hydrogen is difficult.
[0010] These two Brons patents (US 5,635,056 and US 5,695,632) rely fundazx~entally on mixing and reaction of heavy oil with aqueous sodium sulfide, and both suffer the difficulty of having to deal with corrosive sodiemt sulfide or the difficulty of obtaining hydrogen and the danger of handling high pressure and high temperature hydrogen.
[0011 J Siskin {LJS 5,611,915) deals with removal of heteroatoms from high asphaltene materials (such as from heavy oil production) and coal, to favourably lower molecular weights. The patent deals with use of supercritical water in the presence of CO at = 500 psi-2700 psi, with water temperatures in the range of 400°C to 600°C. The teaching of the use of supercritical water together with CO is of some interest.
[0012] This patent (Siskin (US 5,611,915)) relies fundamentally on addition of CO, at high temperatures (400°C-600°C). No provision is made for any convenient apparatus design for mixing and processing the reactants. This patent teaches away from Berkowitz (Cdn 2,000,251), which it cites for use of CO to extract liquids from tar sands, by stressing only N
and S removal. Siskin '91 S in fact is limited in its scope by the prior Berkowitz patent application (Cdn 2,000,251) which already covers all of the subject-matter in Siskin, except that Berkowitz (Cdn 2,000,251) did not specifically mention N or S removal.
Siskin is problematic in requiring high temperatures and the addition of CO, while not providing for any convenient process methodology. Siskin's contribution to the art in the '91 S patent is limited to removal of N and S using a prior piece of art, namely Berkowitz's prior published Canadian application (Cdn 2,000,251).
(0013] Siskin (US 5,338,442) deals with upgrading organic materials such as coal and oil shale, using water at sub-critical temperatures (200°C-374.4°C) in the presence of an acid catalyst. The patent explicitly emphasizes upgrading of coal and oil shale, and does not deal with tarloil sands. Treatment times are S minutes to 1 week (with preference for 30 minutes -3 hours). A key requirement of this process is that for each contacting temperature, the corresponding pressure is the autogenous pressure, i.e., the pressure is kept higher than the critical one in order to maintain the water in liquid form, apparently in a closed reactor. Siskin (US 5,338,443) is problematic in that it relies on addition of an acid catalyst in addition to the water, thus the process involves the expense and complexity of acquiring, stockpiling, handling and balancing catalyst. Moreover, the pressure corresponding to each temperature is high (e.g. Siskin requires a pressure of about 3199.6 psi at the critical temperature of 374.4°C), necessitating expensive and dangerous processing equipment and techniques for its commercial operation; the invention as described does not specify maintaining the contacting water in liquid or supercritical form. There are problems with high temperature, high pressures, and the required use of a catalyst. Additionally, there are unanswered questions with respect to the form of the water during the reaction cycles, and there is a lack of specificity in the nature of the reactor required for tlxe process described, although the maintenance of autogenous pressures leads to batch or closed system apparati.
[0014] Coenen (US 4,485,003) deals with processing coal to make a hydrocarbon liquid using supercritical water at 380°C-600°C in a hi~th pressure reactor. Required pressures range from about 3800 psi to about 6500 psi, and the process also requires addition of hydrogen and a sodium or potassium salt as a catalyst. to the coal. Contact times are 10-120 mitxutes. The teaching of the use of supercritical water to upgrade a fossil fttel to lxydmcarbon liquid is of some interest, however, Coenen (U5 4,48~~,003) is problematic in that it requires the addition of expensive hydrogen and uses corrosive and difficult to handle salts as a necessary catalyst. It also deals with very high pressures, and somewhat lengthy process times.
[001] de Bruijn (Cdn 2,103,508) discloses the use of a water-gas-shift (WGS) in a continuous process to thermally rearrange liquid oil ix~olecules and thus reduce viscosity and density. 'Tho aim is to produce an oillwater emulsion with a sufficiently low viscosity and density to allow transport of the emulsion via pipeline. The process requires contact with CO
or synthesis gas, together with a bifixnctional cai.alyst (such as production fines), at temperatures in the range 250°C-460°C and pressures i.n the range 100-10,000 psi, and reactor residence times of 3 minutes to 10 hours. de Bruijn (C:dn 2,103,508) is problematic in that it relies on addition of a catalyst (together with CO ar synthesis gas, and water). Moreover, de Bruijn emphasizes production of oil/water emulsion rather than crac)Qng of the constituent oil molecules, and does not provide for a lowered viscosity hydrocarbon reaction product, but rather an emulsion requiring further decomposition by additional processing steps to demulsify the reaction product and Further separate th~j water and oil into useful components.
Very high operating pressure and temperature conditions are also required.
[0016] Gregoli (US 4,81$,370) uses a continuous reacfiion to upgrade heavy oil by injecting brine at supercritical conditions. 'The aim is to lower the API
gravity (density) and viscosity of the hydrocarbon feadstock, as well as to reduce the sulfur, nitrogen and heavy metal content. "Brine" refers, in Gregoli, to captured or connate water from the formation.
Specified operating temperatures and pressures are shout 376°C-4$2°C and 3400-4000 psi, respectively, while reactor residence times range from 15 minutes to 6 hours.
Gregoli (CTS

4,818,370) relies on relatively long reactor residene~e times and very high pressure and temperature ranges for operation. In particular, both the pressure and residence time ranges are high, causing some process delay and complexity to required equipment.
Gregoli contemplates that the continuous reaction be accomplished in situ in a production well, by introduction of heated brine and withdrawal of reaction products after a designed dwell-time in situ at desired pressures and temperatures which are quite high. The teaching leads to the use of connate water with included or dissolved minerals, thus contemplating a catalyst-like added feature to the near supercritical brine. Connate water may vary significantly from production well to production well in its composition (~~hemicals in addition to the water), and in situ conditions may be difficult to maintain and expensive and difficult to control or predict.
(001'Tj Enomoto {Cdn 2,220,800) cites as an essential element the injection of water/steam into a well, and the return of mixed oil and water/stearrx, prior to treatment in a reactor system. The processing thus cannot begin except at the production well-site, and is thus constrained in the location of at least some of its apparatus, and by definition uses at least two reaction chambers (the well and a reactor system:l, and perhaps requires more. Enomoco (Cdn 2,220,800) contemplates either heavy oil premixed with water, preferably underground (in an oil reservoir or well), and then heatinglpressurizing of the mixture;
high-temperature water is then added to the system. There are a great number of individual steps anal stages to the processes disclosed. Because Enomoto considers an in situ system, pressure and temperature ranges are not well defined nor well controlled. In broad temps, they range from 71-1420 psi aztd 20°C-350°C, respectively, and thus near supereritieality of the water used is not important for the entire reaction process as specified.
(041$] For the portion of the disclosure dealing specifically with the use of supercritical water in the upgrading process, Enomoto prefers a temperature range of: 300°C-540°C in a very high pressure range most preferably o f 2840-7100 psi.
Enornato discusses an in situ system with several steps, but actually discloses tests performed in a batch mode {1.e. in a closed, and not continuous, system of autoclave,}. The test data disclosed uses high operating conditions of 430°C, a high pressure 63913 psi, and reaction rimes of 5, 15, 30 minutes (actually the in-system dwell time is Ionge:r by an unspecified amount of time, because this is the time described for reaction AFTER REACHING the target temperature by heating in the autoclave over an unspecified preparation time). The Enomoto disclosure may not be workable, discloses a system and process using a number of different reaction chambers, pre-mixes and then heats the hydrocarbon arid water, and deals with high pressures, high temperatures, and long in-system dwell times.
[0019] Furkhermore, Ez~omoto (Cdn 2,22fl,800) specifies a system in which water fmm the reactor system is removed in a phase separator while at high temperature, thus requiring the treatment and handling ofhigh temperature water and hydrocarbons, which may also ba problematic, dangerous and complex, requiring specialized techniques and equipment.
[0020] Brons (US 5,316,659) deals with upgrading of bitumen asphaitenes obtained from oiI sands. The method involves separating sc>lid asphaltene materials from whole bitumen that is recovered from tar sands. Solvent d~asphalting of the whole bitumen is achieved using a C3-CS aliphatic hydrocarbon sol~c~ent such as propane or butane. The precipitated asphaltenes are than contacted with water at temperatures of 300°C-425°C but at no particular pressure and for no particular reaction tune, in order to produce material with a lower average molecular weight. Examples meation xr~ctions in an autoclave, with reactions at 350°C and 400°C over 2 hours. Brons (U9 5,316,659) requires a key addition of a de-asphalting solvent to separate asphaltenes from the whole bitumen, and then uses heated water to treat only the resulting asphaltenes. Thus, there are: required two separate reaction stages, involving quite different reactions (solvent de-aspht~lting of the whole bitumen and then upgrading of the resulting asphaltenes). The reaction tune is quite Lengthy, and the process appears to be done in batches.
[0021) Brons (XJS 5,326,456) is identical to Brons (US 5,316,659), except that it specifies the addition of a soluble carbonate salt, and ~aossibly a transition metal oxide, to the water. These additions further improve the quality of the product. Otherwise, the two disclosures share the same shortcomings.
[0022] Faspek (US 5,096,56'n deals with a process of upgrading heavy hydrocarbons.
The method of this invention features production of au oi1/water emulsion to permit pipeline transfer of the heavy hydrocarbons, together with a method to process the emulsified oil feedstock to obtain light hydrocarbon products. The: method first requires as an essential element the premixing of the oil feedstock and an imnziscible solvent (predominantly water}
to form an emulsion with specified oil droplet sizes. Wlsile the claims indicate that use only of water as the immiscible solvent is sufficient, it is known that heavy oils will not typically forra an emulsion with water (and certainly not in the small range of droplet sizes indicated in the patent) without the addition of some surfactant or ether such component.
Thus, it will be inferred ~d understood that f'aspek (US 5,096,567) re~quircs the addition of some surfactant or other similar material, or rely upon some other unspmified process step in order to work as otherwise described.
j0023] Other parts of the Paspek (US 5,096,567} patent advocate the addition of emulsifying materials such as short-chained alcohc~ls, salts, or other catalysts such as ruthenium carbonyl. The addition of one or more of these catalysts is key, but adds expense, complexity and the need for other materials to the processes involved. The emulsion is subsequently heated in a reactor system and the lighter hydrocarbons are separated. Paspek (US 5,096,567) mentions reaction temperatures in the range 350-1000°C, but preferably in the range 450°C-500°C. Reaction pressures are not specified, but the embodiment teaches pressures in the range of 3000-5000 psi. It can therefore be appreciated that high temperatures, high pressures and complex additive:o are concerns with the Paspek (US
5,096,567) invention. Furthermore, Paspek teaches a reaction time of 30 minutes, which means that the reaction process described will involve; a lengthy processing time. It is noted that the suggestion for use of an immiscible solvent mixed or replaced by short-chained alcohols or other emulsifying materials as x preferta~ embodiment teaches away from use only of water as the immiscible solvent, and in particular away from the use of supercritical water as a satisfactory solvent on its own, thus introducing the need, in the preferred embodiment, of additives and more complex processes.
[0024] lVlurthy (US 4,446,012) deals with upgrading of heavy hydrocarbons into light hydrocarbons by contacting the feedstock with water at temperatures in the range of 380°C-480°C (most preferably between 430°C-460°C) and at pressures in the range of 725-2175 psi.
An essential element of the patent is use of two inaction zones - the first to k~eat the hydrocarbon and water simultaneously to produce a uniform mixture, and the second in which the temperature and pressure are maintained for some time while the uniform mixture is separated into a residue and a vapour phase comprised of a mixture of night hydrocarbons, gas and water. The residue is removed from this second zone and the light hydrocarbon is then recovered from the remaii~zng materials in a phase: separation vessel. Thus, the system requires at least two separate zones wiih separate characters in its reactions.
[0025] Another critical feature of this patent if that the specified range of temperature and pressure is maixataitted itt both the first and the second zones.
Separation of the hydrocarbon, gas and water mixture occurs only subsequently, after the residue is fast removed. Residence tirr~es in the continuous flow s~~stem range from a few minutes to 20 minutes. Murthy (US A~,~6,012) is unique in its essential requirement of two separate reaction zones, in its maintenance of high pressures ar:d temperatures in both zones, and in its method to separate and recover a light hydrocarbon F~hase. Also, the hydrocarbon and water are first mixed and only then heated, apparently to provide a uniformity Qf the mixture.
Murthy requires, in addition to the two separate ?;ones of different character (and thus complex control and sensing zxaechanisms in the processing apparatus), high temperatures for its processes, and deals with the removal of light and vapourous hydrocarbons as part of the processing stages, thus introducing some further c:oznplexity in materials handling and concerns with safe handling of pressurized hydrocarbon vapours at high temperatures.
SUMMr~RY OF THE INVENTION
[4426] Supercritical water is fluid water bn~ught by a combination of heat and pressure to the point at which, as a near vapour, it corribines properties of a gas and a liquid.
[0027] Unlike supercritical propane or cwbon dioxide, supercritical or near-supercritical water exists only at temperatures in excess of 350°C-375°C and at such temperatures, high molecular weight hydrocarbons are: prone to thermal decomposition. Such degradation, synonymous with cracking, tends to incr ease with time at reaction temperatures and as a rule entails two net reaction sets, one generating gas and another yielding high molecular weight carbonaceous products loosely termed coke.
[002$] As is apparent from the background, there are numerous disadvantages to processes and process equipment used in the prior art to upgrade high molecular weight hydrocarbons such as heavy and Serrxi..heavy oils, hydrocarbons recovered from tar sands and oil shales, coals, coal liquids and other bitumens (all of which arc referred to below as "high molecular weight hydrocarbons"). We note that hydrocarbons recovered using conventional Steam Assisted Gravity Drainage (SAGD) production processes for heavy oil production may contain some water, which is not deleterious to the processes of this invention; thus hydrocarbons with water from SAGD recovery processes are included amongst the potential feedstocks for the process of this invention.
[0029) It is apparent, as well, that the term "upgrading", when used in the description of this invention and in the claims, means both upgrading of heavy and semi-heavy oils to unrefined crude oil quality in aspects of viscosity, density, and/or molecular weight, as well as reduction in sulfur, nitrogen and/or metal concentrations, but also means extraction of acceptable oils and oil precursors from oil sand bitumens, coals, coal liquids, oil shales, shale oils, and other bitumens, "acceptable oils and oil precursors" being defined as hydrocarbons suitable for conventional transport and processing/refining.
(0030] In particular, problems with the prior art processes and equipment arise where complex mufti-reactor or mufti-step devices or processes are used, additives such as connate water or catalysts are required, coke byproducts or caustic or dangerous chemicals are produced, or other problems as identified above are encountered.
(0031] In the presence of nominally supercritical water, we find that these processes are also accompanied by thermally-driven hydrolysis of the general form:
R-R'+ H20 ~ R-H + R'-OH
[0032) This is, however, reversible because -C-OH is inherently unstable under reaction conditions, and thus represents a transient process. Maximizing the hydrolyzed reaction product and concurrently inhibiting extreme thermal cracking, which yields gas and coke by random radical recombinations, therefore requires an empirically established compromise between reaction temperature, pressure and the in-reactor residence time of [R-H], [R'-OH] and other species sufficiently degraded to be'soluble' in SCW.
[0033] These considerations, confirmed by data from an extensive series of laboratory tests, lead us to the conclusion that a simple stirred pressure-reactor precludes optimal hydrocarbon upgrading with supercritical water.
[0034] It is an object of the present invention to obviate or mitigate at least one disadvantage of previous processes or process apparatus.

[0035] A far more efficient system offers itself by use of a process and with an apparatus comprising an appropriately designed and scaled flow-through reactor in accordance with the following:
1. The apparatus of the invention is a flow-through reactor for upgrading high molecular weight hydrocarbons, the reactor comprises:
a. a single reaction chamber for maintenance of continuously introduced materials at operating temperatures in the range of 300-450°C and at operating pressures between 1000-3000 psi while the materials are mixed and held inside the chamber for a desired amount of time b. a port for introducing water, including supercritical or near-supercritical water, into the chamber under pressure in a continuous manner c. a port for introducing high molecular weight hydrocarbons into the chamber under pressure in a continuous manner d. an exit port to permit reaction products to leave the chamber under pressure in a continuous manner e. a port for introduction of pressurized CO or nitrogen (optional)~=-2. The process involves a flow-through reactor for upgrading high molecular weight hydrocarbons, the reactor having a single reaction chamber being held at pressures in the range of 1000-3000 psi and temperatures in the range 300°C - 450 °C ardhile water and the hydrocarbons to be upgraded are introduced into the chamber, and then mixed, being held in the chamber for a predefined period of reaction time and thereafter the products of the resulting reaction are permitted to leave the chamber, all on a continuous basis during operation.
In a preferred embodiment, in-reactor residence time does not exceed 25 seconds.
[0036] Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS
(0037) Figure 1 shows a flow-diagram charting the interrelationship of pieces of equipment in a preferred embodiment.
DETAILED DESCRIPTION
(0038) The principal components of a suitable reactor of this type are exemplified in the attached diagram (Figure 1). The numbering in that schematic represents 1. high-pressure nitrogen or CO - the latter for enhancement of oil quality (see below) 2. water reservoir 3. preheater 4. stirred reactor 5. pressure letdown vessel 6. sampling or gas release valve 7. activated carbon trap (or other gas collector) [0039) In such a system, supercritical watery generated by pumping water from the reservoir 2 through the preheater 3, is injected into the reactor 4 at rates similar to those at which it and its entrained hydrocarbon load is withdrawn into the pressure letdown vessel 5 in order to maintain desired operating pressures in the reactor. The reaction can be followed by periodically sampling the exiting stream through a release valve 6, and uncondensed vapours as well as gaseous reaction products are captured as required in an appropriately cooled trap 7. Oils carried into the pressure letdown vessel are recovered by holding its pressure and/or temperature regime sufficiently below that of the reactor to allow the oils to fall out from then-sub-critical water, draining the oils, and substantially freeing them from uncondensed water by phase-separation.
[0040) The inclusion of a source of high-pressure carbon monoxide in the schematic reflects our finding that co-introduction of CO can in some instances -notably when the feedstock is predominantly aromatic - improve the quality of the product oil by increasing the proportion of aliphatics at the expense of aromatics and (hetero-atom bearing) polar compounds. In a preferred embodiment, up to 10% v/v of carbon monoxide is injected based on injected supercritical or near supercritical water. Table 1 illustrates this with data for an Alberta bitumen and also show that pressures above 15-17 MPa can prove counterproductive.

Table 1 Feed 36 11 37 16 reacted with H20 at 400°C/I4.0 MPa 30 19 39 12 400°C/17.9 MPa 24 24 40 12 400°C/24.5 MPa 28 27 43 2 reacted with H20 + CO at 400°C/14.0 NIPa 74 5 19 2 400°C/17.9 MPa 72 5 21 2 400°C/24.5 MPa 66 5 27 2 1. aliphatics; 2. aromatics; 3. polar compounds; 4. asphaltenes HZO/CO mole ratios in these runs ranged from 1.05 and 1.30 to 2.20 [004I] The reference to "hetero-atoms" means that the feedstock may contain sulfur, nitrogen and/or metals. By reducing the proportion of polar compounds from the feedstock, this process, "by definition", has the advantage of also removing sulfur, nitrogen and/or metals, when such hetero-atoms are present in the feedstock.
(0042] We have provisionally ascribed the intervention of CO to generation of active hydrogen by:
CO + H20 ~ COZ + H2 or to an ionic reaction path of the form (cite 5):
Hz0 ~ H+ + OH';CO + OH ~ HCOz ; HCOi + H20 ~ H2C02 + OH', H2CO2 ~ H2 + COa [0043] Literature cited:
1. Berkowitz, N and J. Calderon On 'partial' coal conversion by extraction with supercritical H20 Fuel Process. Technol. 16, 245-256, 1987 2. Berkowitz, N and J. Calderon Extraction of oil sand bitumens with supercritical water Fuel Process Technol. 25, 33-44, 1990 3. Ogunsola, O. M. and N. Berkowitz l;xtraction of oiI shaIes with sub- and near- critical water Fuel Process_ Technol. 45, 95-107, 1995 4. fit. W. Shaw, T. B. Brill, A. A. Clifford., C. A. Eckert and B. U. Frank Supercritical Water - A Medium for Chemistry Chem. & Bngng. News Dee. 23, 16, 19~~1 R. K. Helling and J. W. Tester Energy & Fuels, 1, 417, 1987; Environ. Sci. Technol., 22, 1319, 1988

Claims (10)

1. A continuous method for upgrading a feedstock comprising a high molecular weight hydrocarbon or extracting acceptable oil or oil precursors from feedstock of coal, oil shale, oil sand, bitumen or heavy and semi-heavy oil, comprising:
passing water into a preheater in which said water is converted to supercritical or near supercritical water, injecting said supercritical or near supercritical water into a reactor under pressure in a continuous manner, and simultaneously introducing said feedstock into the reactor under pressure in a continuous manner, reacting said feedstock in said reactor continuously at a temperature in the range of 300-450°C and a pressure in the range of 7 to 21 MPa, for an in-reactor residence time of no greater than 60 seconds, to inhibit substantial coking, and continuously withdrawing hydrocarbon and water from said reactor.

2. The method of claim 1 wherein the pressure is between 7 and 15 MPa.

3. The method of claim 1 or 2 wherein the in-reactor residence time within said reactor for material passing therethrough is less than 25 seconds.

4. The method of any one of claims 1 to 3 wherein the temperature of the supercritical or near-supercritical water upstream of the reactor is at least 350°C.

5. The method of any one of claims 1 to 4 comprising the step of injecting up to 10% v/v carbon monoxide based on injected supercritical or near supercritical water.

6. A system for upgrading a feedstock comprising a high molecular weight hydrocarbon or extracting acceptable oil or oil precursors from feedstock of coal, oil shale, oil sand, bitumen or heavy and semi-heavy oil, comprising:
a preheater for converting water to supercritical or near supercritical water, a reactor, means for injecting supercritical or near supercritical water into the reactor under pressure in a continuous manner, injection means for simultaneously introducing said feedstock into the reactor under pressure in a continuous manner;
means for continuously withdrawing hydrocarbon and water from said reactor, wherein the reaction takes place at a temperature in the range of 300-450°C and a pressure of between 7 and 21 MPa for an in-reactor residence time of no greater than 60 seconds.

7. The system of claim 6 wherein the pressure is between 7 and 15 MPa.

8. The system of claim 6 or 7 wherein the in-reactor residence time within said reactor for material passing therethrough is less than 25 seconds.

9. The system of any one of claims 6 to 8 wherein the temperature of the supercritical or near-supercritical water upstream of the reactor is at least 350°C.

10. The system of any one of claims 6 to 9 further comprising injection means for carbon monoxide into the reactor.