CA2773000A1

CA2773000A1 - Method of partially upgrading heavy oil at well-site

Info

Publication number: CA2773000A1
Application number: CA2773000A
Authority: CA
Inventors: Hidetsugu Fukuyama; Satoshi Okajima; Junichi Mogi; Tsuneta Nakamura; Akira Ikeda
Original assignee: Japan Petroleum Exploration Co Ltd; Toyo Engineering Corp
Current assignee: Japan Petroleum Exploration Co Ltd; Toyo Engineering Corp
Priority date: 2009-09-18
Filing date: 2009-09-18
Publication date: 2011-03-24
Anticipated expiration: 2029-09-18
Also published as: EA026096B1; CA2773000C; EA201270436A1; WO2011033685A1; CN102686708A; CN102686708B

Abstract

Abstract The invention provides a method of partial upgrading of heavy oil at well-site, the heavy oil having an API gravity of 20 or less, by thermal cracking at well-site, using the thermal cracked residue as the fuel to produce the steam for recovering heavy oil from reservoir. The thermal cracking may be conducted at a pressure of 0 to 0.1 MPaG at a temperature of 370 to 440deg C for 15 to 150 minutes in a soaking drum, simultaneously injecting stripping steam to separate a thermal cracked oil, generated in a liquid phase of the soaking drum, as a gaseous thermal cracked oil, from a thermal cracked residue, to obtain a thermal cracked oil product, provided that the liquid phase of the soaking drum is maintained to have an S-value of 2.0 or larger at a thermal cracking extent of fractions having boiling points of 500deg C or higher in the starting heavy oil is 30 % or larger.

Description

Description Title of Invention Method of partially upgrading heavy oil at well-site Field of the invention This invention relates to partial upgrader set at well-site which yields lighter fraction by thermal cracking of heavy oil having an API gravity of 20 or less, and substantially produce fuel source to generate steam to recover heavy oil by injecting steam into a reservoir.

Background of the invention SAGD (Steam Assisted Gravity Drainage) and CSS (Cyclic Steam Stimulation), in which steam is used, are adopted for in-situ recovery of heavy oils. Steam is generated at boilers by firing natural gas, whose cost will occupy more than half of the total operating cost for heavy oil recovering. Therefore, it is necessary to find alternatives other than natural gas from the view points of natural gas availability and the reduction of cost related to fuel for steam generation.

The recovered heavy oil will not meet pipelineable specifications because of low API gravity and poor fluidity due to high viscosity at ambient temperature. Therefore heavy oil being diluted with naphtha or condensate is pipelined as so called DilBit in Canada directly to the market or a refinery, where the diluent is recovered then returned to the well-site via.
diluent pipeline. In the former case, the vol% of diluent is about 30 to the total volume of DilBit whose cost is substantially affected by diluent price and the availability of diluent will be another issue. In the latter case, the pipeline shall be so designed as to accommodate the increased massive volume of heavy oil by dilution and two pipelines are necessary, one for shipment and the other for diluent return between the well-site and the refinery.

Heavy oils are transacted in the market at lower price than conventional crudes for their high contents of impurities such as sulfur, nitrogen and heavy metals (nickel and vanadium) and they are more discounted when they are high-TAN (Total Acid Number).

From above situation, it is necessary to optimize the processing of heavy oils at well-site to upgrade properties and to improve transportability.

Such processes as thermal cracking, solvent deasphalting (SDA) and hydrocraking, which are commonly used to process atmospheric or vacuum residue at conventional refinery configuration, are not suitable for the upgrading of heavy oils at well-site from the following reasons.

Among the thermal cracking processes, coker is not fit to well-site because of a large amount of by-product coke, which requires rather complicated handling works and related facilities. Visbreaker has less upgrading margin from its conversion limitation by the stability of cracked oil.

SDA is an extraction process to separate asphaltene-containing fraction and DAO (de-asphalted oil) in heavy oil feedstock by certain solvent and operating conditions without any reaction to crack or modify the original molecules in the feedstock.

As described in US-B 6, 357, 526, the SCO (synthetic crude oil) , composed of pre-separated gas oil fraction from bitumen and DAO
of the residue by SDA, has an only 4-5 degree improvement of API gravity. This eventually means that API gravity of the obtained SCO from the bitumen supposing API 8 is only 12-13, which is less upgrading effect than the present invention.

The catalyst used in hydrocracking process is subjected to activity degradation due to contamination by nitrogen and heavy metals (nickel and vanadium) highly contained in heavy oils.
The hydracracking process requires high pressure equipment, and hydrogen production unit and source of hydrogen. Thus hydrocracking process may be less applicable to well-site upgrading from its operability and economic disadvantage.
It is pronounced to generate steam by gasification of residue, SDA asphaltene and coke. However gasification process is not appropriate for well-site upgrading f or its scale and complexity.
JP-A 6-88079 discloses thermally cracking a heavy oil and treating the cracking product with stripping steam, that is, HSC (High conversion Soaker Cracking) process.

Hydrocarbon Processing, Sept., 1989, p. 69 shows a conventional visbreaker and a conventional HSC.

Above cited HSC is technically and economically effective for upgrading of heavy oil at well-site replacing natural gas with the thermal cracked residue, by-product of the HSC, for SAGD
and CSS from the view points of natural gas availability and the reduction of cost related to fuel for steam generation.
Summary of Invention The invention provides a method of partially upgrading heavy oil, having an API gravity of 20 or less, fractions having boiling points of 500deg C or lower in an amount of 45 wt. % or smaller, residual carbon (MCR) in an amount of 10 wt. o or larger, a total acid number (TAN) of 1.0 or larger and a kinematic viscosity at 50deg C of 1, 000 mm2/s or larger, the method comprising thermal cracking heavy oil at well-site, using the thermal cracked residue as the fuel to produce the steam for recovering heavy oil from reservoir.

The invention provides a method of transporting, in pipeline, the thermal cracked oil product. Further the invention provides a method of transporting, in pipeline, a mixture of the thermal cracked oil product with heavy oil recovered at well-site for pipeline transportation, not treated by thermal cracking.
Detailed explanation of the invention The invention method of partially upgrading heavy oil may further includes thermal cracking of the heavy oil at a pressure of 0 to 0.1 MPaG at a temperature of 370 to 440deg C for 15 to 150 minutes in a soaking drum (R1) and at the same time injecting stripping steam into the soaking drum to separate a thermal cracked oil, generated in a liquid phase of the soaking drum, as a gaseous thermal cracked oil, from a thermal cracked residue, to obtain a thermal cracked oil product, provided that the liquid phase of the soaking drum is maintained to have an S-value of 2.0 or larger even when a thermal cracking extent of fractions having boiling points of 500deg C or higher in the starting heavy oil is 30 % or larger.

The invention method of partially upgrading heavy oil may further includes steps of flowing out the thermal cracked oil together with a thermal cracked gas and steam through a discharging line (Ll), provided upper in the soaking drum, cooling the lighter fraction directly with a heavier fraction of the thermal cracked oil at a discharging line (L1) , separating a non-condensed lighter fraction, a thermal cracked gas, steam and a condensed heavier fraction of the thermal cracked oil in an upgraded oil heavy fraction separator (D1), discharging the heavier fraction of the thermal cracked oil from a bottom of the separator (Dl), heating the starting heavy oil with a heat-exchanger (C2) for heat-recovering, generating steam at a heat-exchanger (C3), recycling part of the heavier fraction of the thermal cracked oil for a cooling medium to the discharging line (L1) , discharging the rest as a heavier fraction product, cooling the non-condensed lighter fraction, the thermal cracked gas and steam with the heat-exchanger(air cooler) (Cl), separating a condensed lighter fraction from water in an oil/water separator (D2), mixing the condensed lighter fraction with the heavier fraction product to obtain a thermal cracked oil product for pipeline transportation.

The invention provides the above shown thermal cracking method or step for a partially upgrading heavy oil.

In the invention, thermal cracking of heavy oil by the HSC
(High conversion Soaker Cracking) process produces upgraded oil with a lowered viscosity, a raisedAPl gravity and less impurities.
It improves the transportability of heavy oil and separates the thermal cracked residue which is used as the fuel to generate the injection steam into heavy oil reservoir. These directly relate to the reduction of investment cost of heavy oil upgrading at well-site and operating cost of heavy oil recovery by injecting steam into reservoir.

The invention is below explained in comparison with issues of conventional.

1. Heavy oils have higher viscosity and lower API gravity than conventional crudes and are hard to be pipelined. Moreover, heavy oils have high contents of impurities such as sulfur, nitrogen and heavy metals (nickel and vanadium) and TAN.
Thermal cracking of heavy oil by HSC (High conversion Soaker Cracking) process produces upgraded oil with a lowered viscosity, a raised API gravity and less impurities and separates the thermal cracked residue.

2. Visbreaker, a conventional thermal cracking process, is avoided from a high conversion from the reason that the coexistence of the lighter fraction and the cracked residue in the same liquid phase in the reactor has much propensity of asphaltene precipitation, which leads to coking of a reactor and plugging of pipes.

HSC thermal cracking can attain a higher conversion by avoiding the coexistence of the lighter fraction and the cracked residue in the same liquid phase.

3. Heavy oils are highly viscous and low in fluidity so that they have to be pipelined after diluted by diluent or condensate.
A diluent cost and related costs to pipeline are reduced by a less volume of the diluent by means of HSC. The ultimate case of no dilution requires no diluent-returning pipeline.

4. The cost of natural gas for steam generation amounts to more than half of the total operating cost for heavy oil recovering.
Replacing the natural gas for steam generation with the thermal cracked residue, by-product of the HSC, reduces the energy cost.

5. Such conventional processes as thermal cracking, solvent deasphalting (SDA) and hydrocracking, which are commonly used to process atmospheric or vacuum residues in refinery configuration, are not suitable for partial upgrading of heavy oil at well-site from the view points of economically feasible plant scale, obtainable upgrading margin and product oil specifications for pipeline transportation. The HSC process with simplified scheme is more economically feasible than conventional processes and thus suitable for partial upgrading of heavy oil and for making heavy oil transportable at well-site.

The invention solves the above shown issues as follows:
(1) HSC thermal cracking can be operated stably, attaining a higher conversion, in which asphaltenes are kept well-dispersed in the reaction liquid phase by simultaneous separation of thermal cracked oil from the reaction liquid phase, avoiding the coexistence with cracked residue in the same liquid phase.

(2) The HSC produces upgraded oil with a lowered viscosity, a raised API gravity and less impurities such as sulfur, nitrogen and heavy metals (nickel and vanadium) and reduced TAN.

(3) A process scheme in which heavy oil is thermally cracked by the HSC to produce upgraded oil with a lowered viscosity, a raised API gravity and less impurities and separates cracked residue. The thermal cracked oil product as upgraded oil is pipelined after heat recovery.

(4) In the method and scheme, the separated cracked residue is used as the fuel to generate the injection steam into heavy oil reservoir.

(5) The quantity of cracked residue corresponding to the required steam quantity by SOR (Steam to Oil Ratio= volume of water to volume of oil, converted to injection steam for one unit volume of heavy oil) at reservoir injection for heavy oil recovery is adjusted by the feeding rate of heavy oil to the HSC.

The invention relates preferably to a partial upgrading by thermal cracking of heavy oils in order to improve their properties and transportability at well-site at which heavy oils, whose API gravity is less than 20 such as extra heavy crude like Oil Sands Bitumen and Orinoco Tar, or heavy crude, are recovered by injecting steam into heavy oil reservoir.

In the invention, the thermal cracking and injection of stripping steam are carried out in a drum or reactor. The heavy oil is easily separated into a thermal cracked oil product and a thermal cracked residue. The invention can be preferably carried out at well-site of heavy oil source, that is, provides preferably a well-site upgrading method by thermal cracking.

In the invention, the thermal cracked oil product has sulfur, nitrogen and heavy metals (nickel/vanadium) in reduced amounts.
The thermal cracking is preferably carried out at 400deg C to 440deg C and the thermal cracked oil product has a reduced total acidnumber (TAN). The thermal cracked oil product has so reduced viscosity as to be suitable for pipeline transportation. The thermal cracked oil product has a larger API gravity than the starting heavy oil. The thermal cracked oil product is stable in properties by avoiding contact with air during storage or transportation.

The invention method may further comprise firing the separated thermal cracked residue in a boiler to generate steam and using the steam for recovering heavy oil in SAGD,CSS or Steam Flooding. The separated thermal cracked residue may be used in an amount to generate in an amount of steam required for SOR(Steam to oil Ratio) at well-site. The separated thermal cracked residue may be obtained by thermal cracking heavy oil recovered at well-site.

The invention method may further comprise mixing the thermal cracked product with heavy oil recovered at well-site for pipeline transportation.

It is preferable that the starting heavy oil has an API gravity of 20 or less. It is more preferable that the starting heavy oil has an API gravity of 10 or less and a total acid number (TAN) of 2.0 or larger, such as Oil Sands Bitumen or Orinoco Tar.

Brief description of Drawings Fig. 1, includes (a) conventional visbreaker and (b) HSC
and shows a conventional visbreaker and the HSC in comparison.
Fig. 2 shows a well-site HSC process flow scheme. Fig. 3 shows mixing schemes, including part 3. 1 showing commonly used scheme, part 3.2-1 showing all recovered heavy oil processed by the HSC
and part 3.2-2 showing part of recovered heavy oil processed by the HSC. Fig. 4 shows a simple flow diagram of auto-clave experimental apparatus. Fig, 5 is a graph showing thermal cracking yield and TAN of upgraded oil. Fig. 6 is a graph showing reaction temperature and TAN of upgraded-oil.

The invention will be explained more in details in reference to examples and drawings.

Fig. 1 shows conventional Visbreaker and the HSCin comparison.
The visbreaker, both coil type and soaker type, is operated at elevated pressure and the thermal cracked oil and the thermal cracked residue coexist in the same reaction liquid phase, which leads to the situation to accelerate the sedimentation of asphaltenes in the liquid phase. In order to avoid this situation, visbreaker process has intrinsically conversion limitation. In the HSC process, the thermal cracking reaction is carried out under atmospheric pressure and the thermal cracked oil produced is simultaneously stripped away from the reaction liquid phase by the vapor pressure reducing effect of the injected steam in the reaction liquid phase. This allows the HSC proceed the thermal cracking beyond the conversion limit of the conventional visbreaker process.

One of the evaluation methods of the stabilization of thermal cracked oil is known as S-value. S-value is determined by diluting an oil sample with toluene to fully disperse asphaltene and then adding n-heptane to the diluted liquid until asphaltene starts to precipitate. In ASTM D-7157-05, asphaltene precipitated point is optically detected by automatic titration with n-heptane of a toluene-diluted sample. Based on this principle, this invention adopted to detect the asphaltene precipitated point by observing the appearance of a dark spot mark at the center of the spot on the chromatograph paper dropping small amounts of sample specimen at every addition of known amount of n-heptane to toluene diluted sample. The higher S--value is the more stably asphaltenes are dispersed. When precipitation of asphaltene is observed without adding any n-heptane, it is denotedS-value as1Ø The visbreakerissaid to require S-value of minimum 2.0 for the stable process operation.

Fig. 2 shows the flow scheme of the HSC for upgrading heavy oil set at well-site. In Fig. 2, HVO: Heavy Oil Feed, UGO:
Upgraded Oil , P1: Feed Pump, P2: Upgraded Oil Heavy Fraction Circulation Pump, P3: Upgraded Oil Light Fraction Draw-out Pump, P4: Condensed Water Draw-out Pump, P5: Thermal Cracked Residue Circulation Pump, H1: Furnace Heater, Cl: Heat Exchanger 1, C2:
Heat Exchanger 2, C3: Heat Exchanger 3, C4: Heat Exchanger 4, C5: Heat Exchanger 5, Rl: Soaking Drum, D1: Upgraded Oil Heavy Fraction Separator, D2: Oil/Water Separator, Si: Steam, LI: Line 1. HVO is first supplied by a Pump P1 through Heat Exchanger C2 for heating and fed to Charge Heater H1 for designed temperature.
The heated HVO is fed to Soaking Drum Rl in which thermal cracking reactions occur in the liquid zone where steam Si superheated at H1 is injected. The thermal cracked oil (upgraded oil) , which is stripped away from the liquid zone as vapors by the vapor pressure reducing effect of the injected steam in the reaction liquid phase, flows out of the top of R1 together with cracked gas and steam to Upgraded Oil Heavy Fraction Separator D1 through Discharging Line L1. The upgraded oil is directly quenched by circulated cool heavier fraction of thermal cracked oil at L1 from R1 to Dl. Condensed heavier fraction of thermal cracked oil is separated from vapors of the lighter fraction of thermal cracked oil, thermal cracked gas and steam at Dl. Vapors of the lighter fraction of thermal cracked oil, thermal cracked gas and steam are cooled by Heat Exchanger Cl and uncondensed thermal cracked gas flows out of Oil/Water Separator D2. Condensed steam and the lighter fraction of thermal cracked oil are separated from each other at D2 and condensate water is drawn out by Pump P4. The separated lighter fraction of thermal cracked oil is drawn out by Pump P3 and mixed with the heavier fraction of thermal cracked oil. The separated heavier fraction of thermal cracked oil at D1 is circulated by Pump P2, during which is cooled by Heat Exchangers C2 and C3, and used for direct quenching of thermal cracked gas, upgraded oil and steam which come out of R1 at L1.
A part of the heavier fraction of thermal cracked oil cooled by C3 is mixed with the lighter fraction of thermal cracked oil and pipelined as the product upgraded oil UGO after cooled by Heat Exchanger C4.

It is also possible to pre-cut the lighter faction originally contained in HVO before the above processing scheme and to mix it with UGO.

A mixing scheme will be explained below in reference to Fig. 3.

Part 3.1 shows the commonly used scheme using natural gas for steam production and dilution of recovered heavy oil by diluent for pipelining. The water separated from the mixture of heavy oil and hot water came out from subterranean zone is re-circulated and reused for boiler feed water after required treatment.

Part 3.2-1 shows a schematic diagram for the case in which all of the recovered heavy oil is processed by the HSC and the upgraded oil which meets pipelineable specifications is pipelined without dilution. The thermal cracked residue is used as the fuel for steam generation in place of natural gas.
Part 3.2-2 shows a schematic diagram for the case in which the quantity of thermal cracked residue corresponding to the required steam quantity by SOR at reservoir injection for heavy oil recovery is adjusted by the feeding rate of heavy oil to the HSC. The rest of untreated heavy oil is mixed with the upgraded oil by the aforesaid method and the mixture is diluted by a diluent to adjust specifications for pipelining.

In this case, the water is also re-circulated and reused after required treatment of separated water from the mixture of heavy oil and hot water came out from subterranean zone.

Fig. 4 is a simple flow of an experimental autoclave (ACR) apparatus. About 500g of heavy oil is charged into 1 (one) liter autoclave ACR and precisely weighed. After closing the cover flange of the ACR and purging the system by nitrogen, the system was adjusted to the objected vacuum by Vacuum Pump VPUMP. ACR
is immersed into the molten tin bath and the agitator is started above the melting point of heavy oil in ACR. The reaction time counting is started when the heavy oil sample in ACR reached at objected reaction temperature. During the reaction, the effluents from ACR are first cooled at hot water condenser HC
and condensed heavier fraction of thermal cracked oil is collected in Heavy Oil Receiver HOR. Lighter fraction of thermal cracked oil is collected in Light oil Receiver LOR after cooling by cold water and chilled water Cold Trap CC. All of thermal cracked gas is collected in Tedler Bag after measuring the volume by Gas Meter GM.

After the reaction, the bath is lowered rapidly to cool ACR
and stop the reaction. Having been cooled to room temperature, the cover flange is taken out and the ACR is weighed. The weight of the content is determined by reducing the weight of the ACR
itself as a weight of the thermal cracked residue.

The oils in HOR and LOR are weighed in total as an amount of the thermal cracked oil product.

Taking a part of the thermal cracked gas in BAG, the concentration of hydrogen sulfide was measured by detecting tube and the rest of gas components was analyzed by gas chromatography.
The weight of thermal cracked gas was obtained from gas volumes and gas composition.

Properties of heavy oils, Oil Sands Bitumen and Orinoco Tar, used for the experiments, are listed in Table 1. Both feedstocks are extra heavy oil with API gravity less than 10.

Comparison with conventional visbreaking is explained below.

Examples are listed in Table 2 (1) . Examples 1, 2 and 3 are conducted varying the reaction time to obtain different cracking yields at constant vacuum and temperature conditions, 118mmHg and 410 deg C, respectively. S-values of solely the thermal cracked residue and the mixture of upgraded oil and the thermal cracked residue were measured and compared, the former simulating the reaction liquid phase of the HSC in which the upgraded oil simultaneously separated as vapor by stripping steam from the liquid phase, and the latter simulating the reaction liquid phase of visbreaker.

As in Example 1, S-value of the mixture of upgraded oil and the thermal racked residue at the thermal cracking yield (gas +upgraded oil) of 58.3 wt% is 1.9 which is lower than 2.0 of the limit value for the stable operation of visbreaker process.
This means that further cracking brings about highly risky situation which may lead to the contamination, plugging and ultimately coking of the reactor by asphaltene sedimentation.
On the other hands, S-value of solely the thermal cracked residue is 2.8 at the same thermal cracking yield, which implies the well dispersed asphaltenes.

S-value of the mixture of upgraded oil and the thermal cracked residue of Example 2 is 1.6 at thermal cracking yield (gas +upgraded oil) of 62.4wt%, which means worse dispersion of asphaltenes. However, S-value of solely the thermal cracked residue is 2.5 at the same thermal cracking yield, which means asphaltene dispersion kept satisfactorily.

S-value of the mixture of upgraded oil and the thermal cracked residue of Example 3 is 1.4 at thermal cracking yield (gas +upgraded oil) of 67.4wt%, which means worse dispersion of asphaltenes. However, S-value of solely the thermal cracked residue is 2.0 at the same thermal cracking yield meaning asphaltene dispersion kept still within the allowable range of visbreaker. From above Examples the HSC is evidently has the advantage to conventional visbreker keeping asphaltene stability in the reaction liquid phase even above the limit of visbreaker.

Table 2(2) shows S-values of thermal cracked residues from Middle Eastern vacuum residue. Although the softening point of thermal cracked residue of Comparative Example 1 is same as that of Example 1, S-value of Comparative Example 1 is 2.2, which is lower than that of Example 1, namely 2.8.

In the same way, although the softening point of thermal cracked residue of Comparative Example 2 is the same as that of Example 2, S-value of Comparative Example 2 is 1.7, which is lower than that of Example 2, this time namely 2. 5. Thus, the HSC is a superior technology to upgrade heavy oil, especially Oil Sands Bitumen.

Reduction of Contents of Impurities will be explained below.
As shown in Table 3 (1) , contents of nitrogen of 0.4wt%, sulfur of 5. 02wt % and heavy metals (nickel/vanadium) of 85/220wppm of feedstock Oil Sands Bitumen are improved to 0.1-0.2wt%, 3.4-3.66wto and <1/<lwppm, respectively, in the upgraded oils.

Also as shown in Table 3 (2) , contents of nitrogen of 0. 58wt%, sulfur of 3.61wto and heavy metals (nickel/vanadium) of 92/439wppm of feedstock Oil Sands Bitumen are improved to 0.2-0.3wt%, 3.29-3.52wt% and <1/<lwppm, respectively, in the upgraded oils.

Reduction of TAN will be explained below.

Results of TAN reduction of Examples 1, 2, 3, 4, 5 and 6 are shown in Table 4(1), Figs. 5 and 6. When Oil Sands Bitumen with TAN
of 2. 80mgKOH/g is treated by the HSC, TAN of the upgraded oils is reduced to 2.12-1.66 mgKOH/g.

It is observed that the reduction rate of thermal cracking at 390 C is the least and tends to increase with the increase of temperature. Temperature higher than 400 C is effective for the reduction of TAN.

Table 4 (2) shows the results of Examples 11 and 12 for Orinoco Tar. Orinoco Tar with TAN of 3.3 mgKOH/g is treated by the HSC, TAN of the upgraded oils is reduced to 2.0 mgKOH/g.

Storage Stability of Upgraded Oil will be explained below.
Table 5 shows test results of storage stability of upgraded oil. The API gravity and kinematic viscosity of upgraded oil increased with the increase of storage duration in air atmosphere as in Comparative Example 4. However, properties of upgraded oil stored in nitrogen atmosphere are unchanged after 60 days storage as in Example 9. The stability of upgraded oil is kept avoiding the contact with air during long time storage.
Reduction of Diluent and Property Improvement of Blended Oil by Heavy Oil Upgrading In Canada, viscosity not more than 350mm2/s and API gravity more than 19 are one of the pipelineable specifications for heavy oil. Respective viscosities of Examples 1, 2 and 3 are 158, 142 and 130 mm2/s even at 7. 5 C (the climate yearly lowest reference temperature), which are sufficiently below 350mm2/s, as shown in Table 3(1).

Respective API gravities of upgraded oils of Examples 1, 2 and 3 of Table 3 (1) are 19.0, 19.1 and 19.3, which satisfy the requirement of pipelineable specification without dilution.

Table 6 shows the dilution ratios when API gravity of 21 is required for pipelineable specification. Against Comparative Example 3 for which the diluent of 29.8vol% is necessary for the case without upgrading, the upgraded oil by the HSC requires the diluent of 18vol% at SOR 3.0 (Example 7) and the diluent of 11. 5vol % at SOR 4. 0 (Example 8) . Thus when the bitumen processed by the HSC, less amount of the diluent is necessary for pipelineable specification of API gravity 21.

At the same time, sulfur, nitrogen, heavy metals (nickel and vanadium) and TAN of the blended oils of Examples 7 and 8 are lower than those of Comparative Example 3, thus properties of blended oils are improved.

Table 1, Table 1 (continued) , Table 2 (1) , Table 2 (2) , Table 3 (1) , Table 3(1) (continued) , Table 3 (2) , Table 3 (2) (continued), Table 4(1), Table 4(2), Table 5 and Table 6 are below described.

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Table 4(2) Total Acid Number of Upgraded Oil Feed Example 11 Exam le 12 Orinoco Tar Upgraded Upgraded Cerro Negro Oil Oil Vacuum mmHg - 118 140 Reaction Temp. C - 410 420 Reaction Duration min - 20 10 TAN m KOH/ 3.3 2.0 2.0 (1'~ 0, M
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Table 6 Blending Ration for API 21 and Properties of Blended Oil Comparative Example 7 Example 8 Example 3 SOR - 3.0 4.0 without Ungraded Ungraded Upgrading by HSC by HSC
Diluent vol% 29.8 18.0 11.5 Oil Sands vol% 70.2 37.4 19.2 Bitumen Upgraded Oil vol% - 44.6 69.3 Properties of Blended Oil S wt% 3.91 3.64 3.73 N wt% 0.31 0.15 0.21 Ni/V wppm 73/170 10 40/91 TAN mgKOI-1/g 2.15 1.75 1.90 API Gravity: Diluent 65, Oil Sands Bitumen 7.6, Upgraded Oil 19.3

Claims

Claim 1 A method of partially upgrading heavy oil, having an API
gravity of 20 or less, fractions having boiling points of 500deg C or lower in an amount of 45 wt. % or smaller, residual carbon (MCR) in an amount of 10 wt.% or larger, a total acid number (TAN) of 1.0 or larger and a kinematic viscosity at 50deg C
of 1, 000 mm2/s or larger, the method comprising thermal cracking heavy oil at well-site, using the thermal cracked residue as the fuel to produce the steam for recovering heavy oil from reservoir.
Claim 2 The method of Claim 1, further comprising thermal cracking of the heavy oil at a pressure of 0 to 0.1 MPaG at a temperature of 370 to 440deg C for 15 to 150 minutes in a soaking drum (R1) and at the same time injecting stripping steam into the soaking drum to separate a thermal cracked oil, generated in a liquid phase of the soaking drum, as a gaseous thermal cracked oil, from a thermal cracked residue, to obtain a thermal cracked oil product, provided that the liquid phase of the soaking drum is maintained to have an S-value of 2.0 or larger even when a thermal cracking extent of fractions having boiling points of 500deg C or higher in the starting heavy oil is 30 % or larger.
Claim 3 The method of Claim 2, further comprising steps of flowing out the thermal cracked oil together with a thermal cracked gas and steam through a discharging line (L1), provided upper in the soaking drum, cooling the lighter fraction directly with a heavier fraction of the thermal cracked oil at a discharging line (L1), separating a non-condensed lighter fraction, a thermal cracked gas, steam and a condensed heavier fraction of the thermal cracked oil in an upgraded oil heavy fraction separator (D1),discharging the heavier fraction of the thermal cracked oil from a bottom of the separator (D1), heating the starting heavy oil with a heat-exchanger (C2) for heat-recovering, generating steam at a heat-exchanger (C3), recycling part of the heavier fraction of the thermal cracked oil for a cooling medium to the discharging line (L1) , discharging the rest as a heavier fraction product, cooling the non-condensed lighter fraction, the thermal cracked gas and steam with the heat-exchanger(air cooler) (C1),separating a condensed lighter fraction from water in an oil/water separator (D2), mixing the condensed lighter fraction with the heavier fraction product to obtain a thermal cracked oil product for pipeline transportation.
Claim 4 The method according to anyone of claims 1 to 3, in which the thermal cracked oil product contains reduced amounts of sulfur, nitrogen and heavy metals (nickel/vanadium).
Claim 5 The method according to anyone of claims 1 to 3, in which the thermal cracking is carried out at 400deg C to 440deg C
and the thermal cracked oil product has a reduced total acid number (TAN).
Claim 6 The method according to anyone of claims 1 to 5, in which the thermal cracked oil product has a reduced viscosity for pipeline transportation.
Claim 7 The method according to anyone of claims 1 to 6, in which the thermal cracked oil product has a larger API gravity than the starting heavy oil.
Claim 8 The method according to anyone of claims 1 to 7, in which the thermal cracked oil product is stable in properties by avoiding contact with air during storage or transportation.
Claim 9 The method according to anyone of claims 1 to 8, which further comprises firing the separated thermal cracked residue in a boiler to generate steam and using the steam for recovering heavy oil in SAGD,CSS or Steam Flooding.
Claim 10 The method according to claim 9, in which the separated thermal cracked residue is used in an amount to generate in an amount of steam required for SOR(Steam to Oil Ratio) at well-site.
Claim 11 The method according to claim 10, in which the separated thermal cracked residue is obtained by thermal cracking of heavy oil recovered at well-site.
Claim 12 The method according to anyone of claims 1 to 11, further comprising mixing the thermal cracked oil product with heavy oil recovered at well-site for pipeline transportation, not treated by thermal cracking.
Claim 13 The method according to anyone of claims 1 to 12, in which the starting heavy oil has an API gravity of less than 10.
Claim 14 A method of transporting, in pipeline, the thermal cracked oil product of anyone of claims 1 to 11.
Claim 15 A method of transporting, in pipeline, a mixture of the thermal cracked oil product of anyone of claims 1 to 11 with heavy oil recovered at well-site for pipeline transportation, not treated by thermal cracking.
Claim 16 The method according to anyone of claims 1 to 15, in which the starting heavy oil has an API gravity of less than 10 and a total acid number (TAN) of 2.0 or larger.
Claim 17 The method according to claim 16, in which the starting heavy oil is Oil Sands Bitumen or Orinoco Tar.