Additives for steam-recovery of bitumen

Abstract

The present invention relates to in-situ bitumen recovery from an oil sands reservoir. Steam is injected into the reservoir with a mixture of two different alkanolamines and with less than 25 pphw of capped glycol ethers, based on the combined weights of alkanolamines and capped glycol ethers.

Description

ADDITIVES FOR STEAM-RECOVERY OF BITUMENTECHNICAL FIELD

[0001] This application relates to the field of oilfield services.BACKGROUND

[0002] Bitumen and heavy oil (collectively called “high viscosity petroleum” or “HVP” in this document) are viscous petroleum mixtures that are often too viscous to flow readily. Oil sands often contain HVP mixed with sand, clay and other inorganic material. Deposits of oil sands are found around the world, including Canada, Venezuela, and the United States.

[0003] A common group of processes to recover HVP from deep wells uses steam injection to heat the HVP and reduce its viscosity, so that it can flow to a production well and be pumped to the surface. These “steam recovery processes” include cyclic steam stimulation (CSS), steam flooding and steam assisted gravity drainage (SAGD).

[0004] Cyclic steam stimulation (CSS) uses a single well for both injection of steam and recovery of HVP. Steam is injected into the well at a temperature of 250°C to 400°C over a period of days to heat the HVP and decrease its viscosity. The well is allowed to sit for days or weeks, allowing the heated HVP and condensed steam to flow back to the well . Then HVP mixed with condensed steam is pumped to the surface. The process is then repeated. Unfortunately, the CSS process typically results in only 20 to 25 percent recovery of the available HVP.

[0005] Steam flooding uses two vertical wells separated from each other with the target oil sands reservoir between them. A production well is drilled at one end of a reservoir to the level of the oil sands, and an injection well is drilled at the opposite side of the reservoir. Steam is injected into the injection well . The steam heats the HVP and reduces its viscosity, and steam pressure pushes the HVP toward the production well, where it is recovered and pumped to the surface. Steam flooding is commonly used to obtain additional production from an oil sand reservoir after CSS. Typical recovery of the available HVP from steam flooding is about 50 percent.

[0006] Steam assisted gravity drainage (SAGD) uses two different two horizontal wells: A production well is drilled horizontally below a reservoir of oil sands, and an injection well is drilled horizontally above the production well, such as about 5 meters above. Groups of these wells may extend through a reservoir for kilometers in multiple directions. Steam is injected into the injection well. The steam heats and reduces the viscosity of HVP above, to the sides of and below the injection well. Gravity causes the HVP to flow down to the production well, where it is recovered and pumped to the surface. Typical recovery of the available HVP is 40 to 60 percent.

[0007] The steam recovery processes often produce an emulsified mixture of HVP and water. Demulsifiers are used to separate the emulsion into aqueous and organic phases, which can be separated by decanting. The water is cleaned and re-used to make more steam. The HVP is sent for further processing and refinement.

[0008] It is desirable to maximize the recovery of HVP, but steam recovery processes recover only a fraction of the HVP in the reservoir. Thus, there remains a need for efficient and cost-effective methods to increase the recovery of HVP from oil sands. It is known to increase recovery by adding amines, alkanolamines or inorganic bases to the steam used in the steam recovery process. It is desirable to identify optimized additives that can be used in the steam recovery processes.SUMMARY

[0009] The present invention is a process for recovery of bitumen or heavy oil (collectively called “high viscosity petroleum” or “HVP”) from an underground reservoir that contains HVP, comprising tlie steps of: a) injecting into the reservoir a steam / alkanolamine blend that comprises: i. steam; and ii. at least 100 parts-per-million by weight (ppmw) of an alkanolamine mixture, based on the combined weight of alkanolamine mixture and steam, wherein the alkanolamine mixture contains at least 10 weight percent of a first alkanolamine and at least 10 weight percent of a second alkanolamine that is different from the first alkanolamine, based on the total weight of the alkanolamine mixture, and iii. less than 25 parts-per-hundred-by-weight (pphw) of glycol ether that is capped by ethylene oxide or propylene oxide (“capped glycol ethers”), based on the combined weights of the alkanolamine mixture and capped glycol ethers, under conditions such that HVP flows to a production well; and b) recovering the HVP from the production well.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic of the test apparatus used in the Examples. The test apparatus simulates in-situ recovery of bitumen from oil sands.DETAILED DESCRIPTION

[0011] This invention relates to in situ recovery of high viscosity petroleum (HVP) from an oil sand reservoir by a steam recovery process, such as CSS, steam flooding or SAGD.

[0012] The term “steam” used herein includes superheated steam, saturated steam, and less than 100 percent quality steam. For purposes of clarity, the term “less than 100 percent quality steam” refers to steam having a liquid water phase present. Steam quality is defined as the weight percent of dry steam contained in a unit weight of a steam-liquid mixture. “Saturated steam” is used synonymously with “100 percent quality steam.” “Superheated steam” is steam which has been heated above the vapor-liquid equilibrium point. In some embodiments, super-heated steam is between 5 to 50°C above the vapor-liquid equilibrium temperature.

[0013] The optimum steam temperature and pressure needed in the process varies depending on specific reservoir characteristics, such as depth, overburden pressure, and pay zone thickness. In some embodiments, the steam has a temperature of at least 150°C or at least 180°C or at least 200°C. In some embodiments, the steam has a temperature of at most 300°C or at most 260°C or at most 250°C. In some embodiments, the steam has a pressure of at least 4 bar or at least 10 bar or at least 15 bar. In some embodiments, the steam has a pressure of at most 86 bar or at most 47 bar or at most 40 bar.

[0014] In the steam recovery process, steam is injected through an injection well into the reservoir. The steam heats the HVP and reduces its viscosity. In the process, the steam condenses to water. A mixture of the HVP and water flows to a production well, where it is recovered and pumped to the surface. In some embodiments, the mixture is recovered as an emulsion.

[0015] As previously described, in a CSS process, a single well serves as both injection well and production well. Steam is injected into the well. The well is allowed to soak while HVP and water are in contact, and heat transfer occurs. Then the HVP / water mixture is pumped to the surface using the same well. In some embodiments, steam injection is maintained for at least 1 day or at least 2 days or at least 3 days or at least 4 days or at least 5 days or at least 6 days or at least 7 days or at least 8 days or at least 9 days. In some embodiments, steam injection is maintained for at most 21 days or at most 18 days or at most 15 days or at most 14 days or at most 13 days or at most 12 days.

[0016] As previously described, in a steam flooding or SAGD process, steam is injected through an injection well. The force of the steam (in steam flooding) or the force of gravity (in SAGD) brings the softened HVP in a mixture with water to a separate production well. Steam may be injected continuously into the injection well, or steam may be injected periodically with rest times between injections. In some embodiments, the rate of steam injection is managed to maintain a constant desired pressure. In some embodiments, steam is injected at a constant rate, which may be based on the available capacity of steam. In some embodiments of steam flooding, the rate of steam injection is sufficient to provide an advance through the formation of from 1 to 3 feet / day. In some embodiments of steam flooding or SAGD, injection of steam may be simultaneous or alternated with injection of other materials, such as water, carbon dioxide, hydrocarbon or nitrogen.

[0017] Equipment for injecting the steam and the alkanolamine composition into the injection well is known and commercially available. In some embodiments, equipment that is in contact with alkanolamines for long times and / or at high temperatures and / or in high concentrations is made of corrosion resistant materials, such as stainless steel.

[0018] In this invention, the steam is part of a steam / alkanolamine blend that comprises, in addition to steam, an alkanolamine mixture. The alkanolamine mixture contains at least 10 weight percent of a first alkanolamine and at least 10 weight percent of a second alkanolamine that is different from the first alkanolamine, based on the total weight of the alkanolamine mixture. In some embodiments, the alkanolamine mixture contains only two alkanolamines: the first and second alkanolamine. In some embodiments, the alkanolamine mixture contains at least 10 weight percent of each of three or more alkanolamines. In some embodiments, the alkanolamine mixture contains at least 10 weight percent of each of no more than 8 different alkanolamines or no more than 6 different alkanolamines or no more than 5 different alkanolamines or no more than 4 different alkanolamines or no more than 3 different alkanolamines or no more than 2 different alkanolamines.

[0019] Each alkanolamine comprises at least one amine group and at least one hydroxyl group linked by at least one alkyl group. Some embodiments of the alkanolamines are represented by Formula 1 :wherein:• R1is an alkyl group and• R2and R3are each individually selected from hydrogen, alkyl moieties, alkanol moieties which comprise an alkyl group with a pendant or terminal hydroxyl group, and alkylamine moieties which comprise an alkyl group with a pendant or terminal amine group.

[0020] In some embodiments, each alkanolamine is individually soluble in water up to at least 1000 ppmw or at least 2000 ppmw or at least 3000 ppmw or at least 4000 ppmw or at least 5000 ppmw or at least 8000 ppmw or at least 10,000 ppmw. In some embodiments, one or more of the alkanolamines is completely miscible with water. Larger alkyl groups in R1, R2and R3can reduce solubility in water, and hydroxyl or amine groups in R1, R2and R3can increase solubility in water.

[0021] In some embodiments, each alkanolamine individually has a molecular weight of at least 60 Da.In some embodiments, each alkanolamine individually has a molecular weight of at most 200 Da or at most 180 Da or at most 160 Da or at most 140 Da or at most 130 Da or at most 120 Da.

[0022] In some alkanolamines, R1comprises at least 2 carbon atoms. Tn some alkanolamines, R1comprises at most 6 carbon atoms or at most 5 carbon atoms or at most 4 carbon atoms or at most 3 carbon atoms or at most 2 carbon atoms.

[0023] In some alkanolamines, R2and R3are each hydrogen. In some alkanolamines, R2is hydrogen and R3is an alkyl moiety, an alkanol moiety or an alkylamine moiety. In some alkanolamines, R2and R3are each individually an alkyl moiety, an alkanol moiety or an alkylamine moiety.

[0024] Examples of suitable combinations for the alkanolamines include:• R2and R3are both hydrogen, such that the amine group shown in Formula 1 is a primary amine;• R2is hydrogen and R3is an alkyl moiety, such that the amine group shown in Formula 1 is a secondary amine;• R2is hydrogen and R3is an alkanol moiety, such that the amine group shown in Formula 1 is a secondary amine;• R2is hydrogen and R3is an alkylamine moiety, such that the amine group shown in Formula 1 is a secondary amine;• R2is alkyl moiety and R3is an alkanol moiety, such that the amine group shown in Formula 1 is a tertiary amine;• R2is alkyl moiety and R3is an alkylamine moiety, such that the amine group shown in Formula 1 is a tertiary amine;• R2and R3are each individually an alkyl moiety, such that the amine group shown in Formula 1 is a tertiary amine;• R2is alkanol moiety and R3is an alkylamine moiety, such that the amine group shown in Formula 1 is a tertiary amine;• R2and R3are each individually an alkanol moiety, such that the amine group shown in Formula 1 is a tertiary amine; or• R2and R3are each individually an alkylamine moiety, such that the amine group shown in Formula 1 is a tertiary amine.

[0025] In some embodiments, alkyl moieties in R2and R3are individually selected from methyl, ethyl, propyl, butyl, pentyl and hexyl groups, or from methyl, ethyl, propyl or butyl groups. In some embodiments, alkyl moieties in R2and R3are methyl groups. Tn some embodiments, alkyl moieties in R2and R3are ethyl groups.

[0026] In some embodiments, alkanol moieties in R2and R3individually contain at least 2 carbon atoms. In some embodiments, alkanol moieties in R2and R3individually contain at most 6 carbon atoms or at most 5 carbon atoms or at most 4 carbon atoms or at most 3 carbon atoms or at most 2 carbon atoms.In some embodiments, alkanol moieties in R2and R3are individually selected from 2-hydroxyethyl (-CH2- CH2-OH) or 3 -hydroxypropyl (-CH2-CH2-CH2-OH) moieties.

[0027] In some embodiments, alkylamine moieties in R2and R3individually contain at least 2 carbon atoms. In some embodiments, alkylamine moieties in R2and R3individually contain at most 6 carbon atoms or at most 5 carbon atoms or at most 4 carbon atoms or at most 3 carbon atoms or at most 2 carbon atoms. In some embodiments, alkylamine moieties in R2and R3are individually selected from 2- aminoiethyl (-CH2-CH2-NH2) or 3-aminopropyl (-CH2-CH2-CH2-NH2) moieties.

[0028] In some embodiments, one or more amine groups in the alkylamine moieties in R2and R3are individually primary amine groups. In some embodiments, one or more amine groups in the alkylamine moieties in R2and R3are individually secondary amine groups. In some embodiments, one or more amine groups in the alkylamine moieties in R2and R3are individually tertiary amine groups. In some embodiments, at least one of the first alkanolamine and the second alkanolamine is a primary or secondary amine. In some embodiments, both the first and second alkanolamines are independently primary or secondary amines.

[0029] In some embodiments, hydroxyl groups in R2and R3are terminal hydroxyl groups, such as 2- hydroxyethyl or 3 -hydroxypropyl moieties. In some embodiments, amine groups in R2and R3are terminal amine groups, such as 2-aminoethyl or 3-aminopropyl moieties. In some embodiments, hydroxyl groups or amine groups in R2and R3are pendant hydroxyl or amine groups, such as 2-hydroxypropyl moieties or 2-aminopropyl moieties.

[0030] Examples of alkanolamines that contain primary amines include ethanolamine (also called mono-ethanolamine or “MEA”), 3 -amino- 1 -propanol, 4-amino-l -butanol, valinol and 2-aminoethyl- ethanolamine (“AEEA”).

[0031] Examples of alkanolamines that contain secondary amines include n-methyl ethanolamine (“NMEA”), diethanolamine (“DEA”), 2-aminoethyl-ethanolamine (“AEEA”), ethylaminoethanol, isopropylaminoethanol, n-butylaminoethanol and t-butylaminoethanol.

[0032] Examples of alkanolamines that contain tertiary amines include diethylaminoethanol, isopropylaminodiethanol, diisopropylaminoethanol, n-butyldiethanolamine, di-n-butylaminoethanol and dimethylamino-2-propanol.

[0033] In some embodiments, the first alkanolamine comprises a secondary amine nitrogen. In some embodiments, the first alkanolamine is NMEA. In some embodiments, the first alkanolamine is DEA. In some embodiments, the first alkanolamine comprises a tertiary amine nitrogen. In some embodiments, the first alkanolamine makes up at least 20 weight percent of the alkanolamine mixture or at least 30 weight percent or at least 40 weight percent or at least 50 weight percent or at least 60 weight percent or at least70 weight percent or at least 80 weight percent. The first alkanolamine necessarily makes up no more than 10 weight percent of the alkanolamine mixture.

[0034] In some embodiments, the second alkanolamine comprises a primary amine nitrogen. In some embodiments, the second alkanolamine is MEA. In some embodiments, the second alkanolamine comprises both a primary amine nitrogen and a secondary amine nitrogen, such as 2-aminoethyl- ethanolamine (“AEEA”). In some embodiments, the second alkanolamine makes up at least 15 weight percent of the alkanolamine mixture or at least 20 weight percent or at least 30 weight percent or at least 40 weight percent or at least 50 weight percent or at least 60 weight percent or at least 70 weight percent or at least 80 weight percent. The second alkanolamine necessarily makes up no more than 10 weight percent of the alkanolamine mixture. In some embodiments, the second alkanolamine makes up at most 80 weight percent of the alkanolamine mixture or at most 70 weight percent or at most 60 weight percent or at most 50 weight percent or at most 40 weight percent or at most 30 weight percent or at most 20 weight percent.

[0035] The alkanolamines of this invention may extract hydrogen from water to form ionized equivalents when they are mixed with water or steam. The description of alkanolamines in this document includes and applies with equal force to the ionized equivalents.

[0036] The alkanolamine mixture may be added to the steam neat or as a concentrate. If added as a concentrate, it may be added as a 1 to 99 weight percent solution in water. In some embodiments, the concentrate contains at least 5 weight percent of the alkanolamine mixture or at least 10 weight percent or at least 15 weight percent or at least 20 weight percent or at least 25 weight percent. In some embodiments, the concentrate contains at most 90 weight percent of the alkanolamine mixture or at most 80 weight percent or at most 70 weight percent or at most 60 weight percent or at most 50 weight percent. In some embodiments, the alkanolamine mixture is substantially volatilized and carried into the reservoir as an aerosol or mist, in order to maximize the amount of alkanolamine traveling with the steam into the reservoir.

[0037] The alkanolamines in the alkanolamine mixture may be premixed to make the alkanolamine mixture before being added to the steam. Alternatively, the alkanolamines may be added separately to the steam and form the alkanolamine mixture in the steam.

[0038] The steam / alkanolamine blend contains at least 100 part-per-million-by-weight (ppmw) of the alkanolamine mixture. In some embodiments, the steam / alkanolamine blend contains at least 200 part-per- million-by-weight (ppmw) of the alkanolamine mixture or at least 250 ppmw or at least 400 ppmw or at least 500 ppmw or at least 750 ppmw or at least 1000 ppmw. In some embodiments, the steam / alkanolamine blend contains at most 20,000 ppmw of the alkanolamine mixture, or at most 15,000 ppmw or at most 10,000 ppmw or at most 8000 ppmw or at most 6000 ppmw or at most 5000 ppmw.

[0039] We hypothesize, without intending to be bound, that the alkanolamines in the alkanolamine mixture (and possibly also their degradation products) act as surfactants to improve the transportation of HVP with the steam and / or condensed water to the recovery well.

[0040] In the invention, the steam / alkanolamine blend contains less than 25 parts per hundred by weight (pphw) of ethylene oxide-capped and propylene-oxide capped glycol ether, based on the combined weight of alkanolamines and glycol ethers. As used hereafter, ethylene oxide capped glycol ethers means that the ethylene oxide cap comprises 1 to 3 ethylene oxide units. As used hereafter, propylene oxide capped glycol ethers means that the propylene oxide cap comprises 1 to 3 propylene oxide units. Exemplary “capped glycol ethers” conform to Formula 1(a) or 1(b):(la) RO-(CH2CH(CH3)O)ni(C2H4O)n H(lb) RO-( C2H4O)o(CH2CH(CH3)O)p H wherein:• R is a linear, branched, cyclic alkyl, phenyl, or alkyl phenyl group of equal to or greater than 4 carbons,• m is on average 0 to 3,• n is on average 1 to 3,• o is on average 0 to 3, and• p is on average 1 to 3,

[0041] In some embodiments, the steam / alkanolamine blend contains no more than 24 pphw capped glycol ethers, based on the combined weight of alkanolamines and glycol ethers, or no more than 22 pphw or no more than 20 pphw or no more than 18 pphw or no more than 16 pphw or no more than 14 pphw or no more than 12 pphw or no more than 10 pphw or no more than 8 pphw or no more than 6 pphw or no more than 4 pphw or no more than 2 pphw or 0 pphw. There is no minimum amount of glycol ether desired. In some embodiments, the steam / alkanolamine blend contains no glycol ethers, but some embodiments of the steam / alkanolamine blend contains at least 1 pphw glycol ethers, based on die combined weight of alkanolamines and glycol ethers, or at least 5 pphw or at least 10 pphw.

[0042] In some embodiments, the steam / alkanolamine blend contains no more than 50 pphw of fatty alkyl esters, based on the combined weight of alkanolamines and fatty alkyl esters, or no more than 40 pphw or no more than 30 pphw or no more than 25 pphw or no more than 20 pphw or no more than 18 pphw or no more than 15 pphw or no more than 12 pphw or no more than 10 pphw or no more than 8 pphw or no more than 6 pphw or no more than 4 pphw or no more than 2 pphw or 0 pphw. There is no minimum amount of fatty alkyl esters desired. In some embodiments, the steam / alkanolamine blend contains no fatty alkyl esters, but some embodiments thesteam / alkanolamine blend contains at least 1 pphw fatty alkyl esters, based on the combined weight of alkanolamines and fatty alkyl esters, or at least 5 pphw or at least 10 pphw. Examples of fatty alkyl esters include methyl, ethyl, n-propyl, isopropyl, or n-butyl esters of C4 to C22 fatty acids, such as fatty acids derived from soya, canola, and other vegetable oils.

[0043] The effectiveness of the steam / alkanolamine blend can be measured by measuring the production difference in a well between ordinary steam and steam that contains the alkanolamine mixture; the difference is sometimes called “oil uplift.” For example, in some cases, the first production in a well is with ordinary steam, and then an additive package is tested in the steam later in production, to judge how effective the additive package is for that particular well In some embodiments, the oil uplift of HVP at the production well after using the alkanolamine mixture is at least 5% percent greater than using the alkanolamine mixture or at least 30% percent greater or at least 50% percent greater.

[0044] As previously discussed, HVP is often recovered as an emulsion of HVP and water. HVP can be recovered from the emulsion by adding a demulsifier, and decanting to separate the aqueous and organic phases. Demulsifiers are known and commercially available. They include polyol block copolymers, alkoxylated alkyl phenol formaldehyde, epoxy resin alkoxylates, amine-initiated polyol block copolymers, modified silicone polyethers, and silicone polyethers. They are available under the DEMTROL™, DOWSIL™ and XIAMETER™ trademarks.

[0045] The following Examples show the performance of specific embodiments of the alkanolamine mixture in a laboratory apparatus that simulates performance of the alkanolamine mixture in steam recovery processes in in-situ oil sands.EXAMPLESExamples 1-5:

[0046] For Inventive Examples IE1-IE4 and for Comparative Examples CE0-CE4b, sand cores saturated with native bitumen are tested in a test apparatus that is illustrated in FIG. 1. The apparatus contains a fluid-tight pressure vessel, which fits inside an oven. The bottom of the pressure vessel can hold liquid, and a raised glass cup stands on tripod legs above the expected level of liquid in the pressure vessel. A post from the top of the pressure vessel suspends the following components over the cup:• a cold finger that is 6 inches long and 0.5 inch in diameter; and• a synthetic sand core that encloses the cold finger and is 6 inches long and 1.5 inch in diameter. Feed lines inside the post connect the cold finger to a cooling water source outside the oven and bring pressurized cooling water to and from the cold finger. The feed lines are insulated to minimize both the heating of the cooling water in the feed lines and the condensation of vapors in the pressure vessel on the feed lines. Cooling water in the feed lines and the cold finger is under pressure of 30 bar to 35 barto minimize flashing and cold spots. The test apparatus simulates conditions in an underground reservoir in which a steam / alkanolamine blend (evaporated from the bottom of the pressure vessel) encounters sand that contains bitumen at a lower temperature than the steam (due to the presence of the cold finger).

[0047] Synthetic cores are made by placing crushed sandstone in a cylindrical mesh (6 inches long by 1.5 inches in diameter, with a 0.5 inch gap in the idle for a cold finger). Each sand core is dipped in dewatered native bitumen at 60°C for 24 to 48 hours to completely saturate the core with bitumen. The saturated core is quenched to room temperature. The bitumen reaches a viscosity of around 1,000,000 cP. Each core is weighed before and after saturation, so that the quantity of bitumen in the saturated core is known.

[0048] The following commercial alkanolamines from The Dow Chemical Company are used in the examples:

[0049] Aqueous solutions are made that contain 5000 ppmw of the alkanolamines / mixtures listed in Table 1. In each example, a 0.4 L portion of an aqueous solution is added to the bottom of the pressure vessel. A three-legged collection cup of known tare weight stands above the level of the additive solution. A saturated core is weighed and suspended on the cold finger from the top of the pressure vessel, above the open mouth of the glass collection cup. \

[0050] The pressure vessel is sealed, placed in the oven and heated about 60 minutes for the vessel to reach temperatures around 250°C, while cooling water flows through the cold finger. We estimate that the saturated core has a surface temperature of 250°C and an interior temperature of 180°C. The system is maintained in this state for 6 hours while monitoring temperature across the core and the pressure vessel. During this time, an emulsion of bitumen and water drips from the saturated core into the collection cup.

[0051] After six hours, the pressure vessel is removed from the oven and quenched to reduce dripping of the bitumen from the core.

[0052] The amount of bitumen that has been recovered from the saturated core is determined by two methods:• First, the core is recovered and weighed. The difference in weight from the saturated core after the test is considered to be the amount of recovered bitumen.• Second, the emulsion collected in the cup is weighed. An aliquot of the emulsion is tested to measure the content of bitumen in emulsion. The total amount of bitumen is calculated as this bitumen content times the amount of emulsion collected.Both numbers are averaged to get the amount of bitumen recovered in the experiment.

[0053] Comparative Example CEO lists the bitumen recovery from water without alkanolamines, as a percentage of bitumen in the core, in the column “Measured Recovery.” This is the baseline for the examples.

[0054] Comparative Examples CEla to CE4b list the bitumen recovery from water with individual alkanolamines at a concentration of 5000 ppmw in water, as a percentage of bitumen in the core, in the column “Measured Recovery.” The column “Improvement over Baseline (%)” shows how much the measured recovery improved over the baseline of water.

[0055] In vend ve Examples IE1 to IE4 list the bitumen recovery from water with mixtures of alkanolamines at an aggregate concentration of 5000 ppmw in water, as a percentage of bitumen in the core, in the column “Measured Recovery.” The column “Improvement over Baseline (%)” shows how much the measured recovery improved over the baseline of water.

[0056] For each mixture, the expected performance of the mixture is calculated based on the pro rata performance of the individual alkanolamines in the mixture, and is shown in the column “Predicted Recovery (%)”. Likewise, the expected improvement over baseline is calculated and is shown in the column “Predicted Improvement over Baseline”.

[0057] Inventive Examples IE1 to IE 4 show that mixtures of alkanolamines recover more bitumen than would be expected based on the individual performance of the components in the mixture and, in some cases, recover more bitumen than any component can recover by itself.Table 1

Claims

CLAIMSWe claim:

1. A process for in-situ recovery of bitumen or heavy oil, which is collectively called “high viscosity petroleum” or “HVP”, from an underground reservoir that contains HVP, comprising the steps of: a) injecting into the reservoir a steam / alkanolamine blend that comprises: i) steam; and ii) at least 100 parts-per-million by weight (ppmw) of an alkanolamine mixture, based on the combined weight of alkanolamine mixture and steam, wherein the alkanolamine mixture contains at least 10 weight percent of a first alkanolamine and at least 10 weight percent of a second alkanolamine that is different from the first alkanolamine, based on the total weight of the alkanolamine mixture, and iii) less than 25 parts-per-hundred-by-weight (pphw) of glycol ether that is capped by ethylene oxide or propylene oxide, called “capped glycol ethers”, based on the combined weights of the alkanolamine mixture and capped glycol ethers; under conditions such that HVP flows to a production well; and b) recovering tire HVP from die production well.

2. The process of Claim 1 wherein the first alkanolamine and the second alkanolamine are each individually represented by Formula 1wherein: a) R1is an alkyl group; and b) R2and R3are each individually selected from hydrogen, alkyl moieties, alkanol moieties which comprise an alkyl group with a pendant or terminal hydroxyl group, and alkylamine moieties which comprise an alkyl group with a pendant or terminal amine group.

3. The process of Claim 2 wherein the first alkanolamine and the second alkanolamine are each individually soluble in water up to at least 2000 ppmw.

4. The process of Claim 2 wherein the first alkanolamine and the second alkanolamine each individually have a molecular weight from 60 Da to 180 Da.

5. The process of Claim 2 wherein the first alkanolamine comprises a secondary or tertiary amine nitrogen and the second alkanolamine comprises a primary amine nitrogen.

6. The process of Claim 5 wherein the second alkanolamine comprises both a primary amine nitrogen and a secondary amine nitrogen.

7. The process of Claim 5 wherein the first alkanolamine comprises a secondary amine nitrogen.

8. The process of Claim 5 wherein the first alkanolamine comprises a tertiary amine nitrogen.

9. The process of Claim 5 wherein the alkanolamine mixture contains at least 40 weight percent of the first alkanolamine and at least 15 weight percent of the second alkanolamine.

10. The process of Claim 1 wherein: a) the first alkanolamine is selected from n-methyl ethanolamine, diethanolamine, n-methyl diethanolamine or triethanolamine, and b) the second alkanolamine is selected from mono-ethanolamine or 2-aminoethyl-ethanolamine.

11. The process of Claim 10 wherein the first alkanolamine is n-methyl ethanolamine (“NMEA”).

12. The process of Claim 1 wherein the steam / alkanol amine blend comprises no more than 10 pphw of capped glycol ethers, based on the combined weights of the alkanolamine mixture and capped glycol ethers.

13. The process of Claim 12 wherein the steam / alkanolamine blend comprises no more than 50 pphw fatty alkyl esters, based on the combined weight of alkanolamines and fatty alkyl esters.

14. The process of any one of Claims 1 to 13 wherein the steam / alkanolamine blend comprises at least 500 ppmw of the alkanolamine mixture.

15. The process of Claim 14 wherein the steam / alkanolamine blend comprises from 1000 ppmw to 5000 ppmw of the alkanolamine mixture.

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