Heavy oil viscosity reduction using ionic liquids

Abstract

The present process offers a new effective method for addressing the need to reduce the viscosity of heavy oils. In one embodiment the present process provides an efficient process for using ionic liquids (ILs), to reduce the viscosity of heavy oil. Particular ionic liquids have been found to surprisingly provide the needed reduction in viscosity to allow the transportation of heavy oils in pipelines. The present ionic liquids comprise an amine-based cation and a carboxylic acid-based anion.

Description

70205.0690WOU1 (T-11793-WO01)HEAVY OIL VISCOSITY REDUCTION USING IONIC LIQUIDSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 697,730 filed September 23, 2024, the complete disclosure of which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present process relates to reducing the viscosity of heavy oil. The process employs particular ionic liquids to achieve viscosity reduction.BACKGROUND

[0003] The high viscosity of production fluids presents an issue for the transportation of reservoir fluids from the reservoir to the topsides / processing facilities. Transporting highly viscous fluids can lead to flow assurance issues (not able to produce) and can result in significant operating expenses. Heavy oil is a common high viscosity fluid encountered in oil and gas production.

[0004] One of the reasons for the high viscosity of heavy oil is the presence of asphaltenes, which are mainly composed of polyaromatic rings, aliphatic side chains of various lengths and heteroatoms such as oxygen, nitrogen, sulfur, and heavy metals. Asphaltene is considered as one of the primary contributors to the high viscosity of heavy oils. Due to the highly polar and unsaturated nature, asphaltene molecules can also interact with each other forming even heavier agglomerates that, under certain conditions, could precipitate out from liquid hydrocarbon. Solvating asphaltenes in the crude oil could significantly reduce oil viscosity.

[0005] The most common practice in the industry to reduce heavy oil viscosity is to heat the heavy oil with steam, as the viscosity of the heavy oil decreases as temperature increases. However, the generation of steam can potentially increase the overall carbon footprint of the transportation process. Another practice is the injection of a solvent, such as toluene, to dilute the heavy oil and lower the viscosity of the mixture. However, the use of solvents increases operating expenses and risk due to their relatively low vapor pressure, and often times proves to be economically non-feasible. The low vapor pressure significantly increases transportation and storage safety concerns and costs. Hence the70205.0690WOU1 (T-11793-WO01) industry would be served by an alternate, novel solution to enable a cleaner, more economic, and reliable production of heavy oil.

[0006] One such alternative is the injection of low dosage chemicals that can alter the chemistry of heavy oil to reduce its viscosity. Ionic liquids have been employed. See, for example, U.S. Patent No. 9,790,446, which uses a chemical composition comprising an ionic liquid of the family of imidazolium cations combined with small anions such as chloride, hydroxide and fluorinated anions. See also, for example, U.S. Patent No. 11,235,998 which uses ionic liquids in the remediation and amelioration of oil sand materials, including the separation of bitumen from oil sand.

[0007] Major chemical suppliers have also proposed and supply chemicals such as flow improvers and viscosity reducers to decrease the viscosity of heavy oil. Such chemicals are expensive, and often not effective.

[0008] To provide a novel, more economic, and more effective processes for the reduction of heavy oil viscosity would be of great interest to the industry.SUMMARY

[0009] Against this backdrop the present invention was developed. The claimed process offers a new effective method for addressing the need to reduce the viscosity of heavy oils. In one embodiment the present process provides a new, useful, and efficient process for using Ionic Liquids (ILs), to reduce the viscosity of heavy oil. Particular ionic liquids have been found to surprisingly provide the needed reduction in viscosity to particularly allow the transportation of heavy oils in pipelines. The present ionic liquids comprise an amino-based cation and a carboxylic acid-based anion.

[0010] Among other factors, it has been found that adding the present ionic liquids to heavy oils can result in effective and efficient lowering of the viscosity of the heavy oil. The heavy oil can then be transported in an efficient, more economic fashion, which is beneficial to the industry.DETAILED DESCRIPTION

[0011] Before the ionic liquid compositions and their use in viscosity reduction of heavy oils are disclosed and described, it is to be understood that this disclosure is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for70205.0690WOU1 (T-11793-WO01) the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in this specification, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a step" may include multiple steps, reference to "producing" or "products" of a reaction or treatment should not be taken to be all of the products of a reaction / treatment, and reference to "treating" may include reference to one or more of such treatment steps. As such, the step of treating can include multiple or repeated treatment of similar materials / streams to produce identified treatment products.

[0012] Numerical values with "about" include typical experimental variances. As used herein, the term "about" means within a statistically meaningful range of a value, such as a stated particle size, concentration range, time frame, molecular weight, temperature, or pH. Such a range can be within an order of magnitude, typically within 10%, and more typically within 5% of the indicated value or range. Sometimes, such a range can be within the experimental error typical of standard methods used for the measurement and / or determination of a given value or range. The allowable variation encompassed by the term "about" will depend upon the particular system under study, and can be readily appreciated by one of ordinary skill in the art. Whenever a range is recited within this application, every whole number integer within the range is also contemplated as an embodiment of the invention.

[0013] The present process offers a new efficient method of addressing the need to lower the viscosity of heavy oil during the transportation of reservoir fluids from the reservoir to the topsides / processing facilities.

[0014] Ionic liquids are a new class of chemicals. These chemicals are, on a basic level, organic salts comprising an organic cation paired with an organic or inorganic anion. In general, the melting points are less than 200°C. The salts exhibit complex anionic- cationic interactions that can yield unconventional properties, including selective solubility, purification, and miscibility. The significant advantage offered by ILs is the ability to independently alter the cations and anions that comprise the IL to tailor or otherwise select the IL for specific applications. Such an IL is used in the present process.

[0015] In step a) of the present process, one such IL is provided, comprising an amino-based cation and an oleate acid-based anion. In one embodiment, the cation comprises an amine-based cation with alkane chains ranging from C2 - C22. This amine- based cation can comprise three alkane chains. In other embodiments, the amine-based- cation has triple alkane chains each with the same carbon number. This amine-based cation70205.0690WOU1 (T-11793-WO01) with triple alkane chains with the same carbon number can have the formula of (CnH2n+l)3N.

[0016] The anion comprises a carboxylic acid-based anion. The number of carbons in the carboxylic acid can range from 10 to 25 carbons in one embodiment, and from 13 to 21 in another. The best results have been found when the anion is based on oleic acid, comprising 18 carbons. Thus, in one embodiment, the anion comprises an oleic acid-based anion. It has been found that the oleic acid-based anion with the present amino-based cation provides an ionic liquid of particular effectiveness in reducing the viscosity of heavy oils. In one embodiment, the IL is tri-n-octylamine oleate.

[0017] In some embodiments, providing the present ionic liquid composition in step a) can further comprise mixing the ionic liquid with a diluent. In some embodiments this is done to further effectively reduce the viscosity of crude oil. In some embodiments these diluents comprise, but are not limited to, toluene, a petroleum distillate paraffinic solvent such as Isopar M available from ExxonMobil Chemical, condensate, and production fluids. In general, either aromatic solvents, such as toluene, or paraffinic solvents, such as Isopar M, provide the best results in viscosity reduction.

[0018] The amount of ionic liquid used or injected can be any suitable amount needed to achieve the required viscosity reduction. The amount will depend on the particular heavy oil in which the ionic liquid will be injected. The amount may also vary depending on any solvents also being injected. In general, the amount of the present ionic liquid injected into the heavy oil can range from 1000 ppmv to 50,000 ppmv (5v%). In one embodiment, the amount of ionic liquid ranges from 10,000 ppmv (lv%) to 30,000 ppmv (3v%). It has been found that viscosity reduction is lower at the lower concentrations of ionic liquid, within the range of IL concentration tested.

[0019] If the ionic liquid composition comprises a solvent, the amount of ionic liquid can comprise the same volume % of the mixture, but the total volume % of the mixture will now include the solvent as well. For the amount of solvent used, regardless of the type of solvent, the amount can range from 1 to 15 v% of the mixture of ionic liquid, heavy oil, and solvent. In some embodiments, the amount of solvent can range from 5 to 13v%, and in one embodiment, the amount of solvent is used in an amount of about 10 v%.

[0020] In step b) of the present process, the IL composition is introduced or injected into the heavy oil such as heavy oil in a production stream. By heavy oil, is meant heavy petroleum crude oils, as is known in the petroleum industry. The location of injection depends on the oil properties, and wellbore and flowline operating conditions. In some70205.0690WOU1 (T-11793-WO01) embodiments, the chemicals are injected at the wellhead at heavy oil fields. If the fluid temperature is sufficiently high in the wellbore, the pressure drop in the wellbore is not high and the fluid can be lifted from bottle hole to wellhead. As the fluid flows in the flow line (often bare pipeline with no insulation), the fluid quickly cools to the ambient temperature. At ambient temperature, the viscosity of heavy oil, hence the pressure drop in the flowline, is usually too high to be produced at sufficient rates without artificial lift methods. If the IL chemical is injected at the wellhead into the hot produced fluid, the fluid viscosity can be reduced to lower the pressure drop in the flowline. Injection at the wellhead is usually preferred to downhole injection.

[0021] In other embodiments, the IL is injected downhole. For downhole injection, chemicals may be transported to downhole locations via small diameter tubes. These downhole chemical tubes are usually not preferred in the well design as they increase the cost of well completion and introduce possible pathways for leaks.

[0022] Of particular relevance, the IL can be injected at point of extraction from the well in the field, during the transport of crude oil in pipelines, or in the well discharge pipelines. The application can thus be performed at several points along with production chain, for example, during the stage of extraction, surface transportation by pipelines and during processing. Transportation to processing facilities in pipelines has been found to be of particular importance, and the present process and ionic liquid composition is most helpful in such an application.

[0023] In some embodiments of step b) the IL being used can comprise either an undiluted IL, a diluted IL, or a mix of undiluted and diluted IL. In other embodiments undiluted ILs are injected at one injection site, while diluted ILs are injected at another. In still other embodiments both undiluted and diluted ILs are injected at the same injection site.

[0024] The effectiveness of the ionic liquid in reducing heavy oil viscosity may depend on the degree of mixing between the IL and the heavy oil. To increase the extent of mixing between the two, liquid-liquid mixing devices can be used. Some examples of mixing devices are orifice valves, vessels with impellers or baffles, nozzles, in-line static mixers or in-line dynamic mixers. The choice of a mixing device depends on the properties of the heavy oil and the ionic liquid, process and facility design, and operating conditions.

[0025] For the desired viscosity reduction, a certain concentration of IL in the mixture should be maintained. This concentration is achieved by ensuring a certain injection rate of ionic liquid into the system. The flow rate of ionic liquid is set by multiple parameters70205.0690WOU1 (T-11793-WO01) such as the pressure in the line where IL is injected, the speed and suction / discharge pressure of the chemical injection pump, the chemical injection valve (orifice / nozzle) opening, or the speed of impeller in an inline mixer.

[0026] In one embodiment a recovery step c) occurs in which the ionic liquid is recovered subsequent to completion of its application. In this recovery step, the ionic liquid can be recovered from the producing fluid received at the process facilities. Low dosage chemicals are typically not recovered from the produced fluids at the process facilities. This is due to their low concentration, typically less than 100 ppmv, in the fluid received at the process facilities, and due to the partitioning of the chemical in oil, gas and water phases. However, significantly, ILs can be custom designed to be retained in the oil phase, facilitating easier separation from the fluid. In some embodiments the recovered IL can be re-injected. Recovering and re-injecting the IL reduces the operating expenses from chemicals, further improving the economics of the project. In other embodiments the recovered IL can be disposed.

[0027] The use of the present ionic liquids in reducing the viscosity of heavy oils offers many advantages. First, an increased productivity factor and profitability of producing wells, especially those containing heavy and extra-heavy oils, with results that depend on the above-mentioned variables and of characteristics proper to the well. The chemical agents can be in aqueous or organic solutions. The formulations can be injected in one or several points, e.g., downhole in production tube, a well's discharge line and surface transportation pipelines. The net effect is the increase in the mobility of the crude oil, by reducing its viscosity and its interfacial tension, thus facilitating transportation and pumping operations. Therefore, the well productivity increases by increasing the flow rate, which follows the viscosity reduction. Therefore, this invention has a significant potential to promote a higher productivity of heavy oil wells, which is derived from a better oil mobility and its higher fluidity, which in turn improves the pumping operations and brings a cost reduction altogether.

[0028] Secondly, a cost reduction in the surface pipeline transport of heavy crude oils, especially for long distance operations, due to viscosity reduction, less friction of the fluids and easier pumping operations along the transport chain, which reduces expenses associated with extra heating of the crude oil along the lines of transport, especially in winter. The reduced viscosity also provide longer durability of the field installations, a decrease of the number of repairs arising from wear and use of pumping equipment, a reduction of delivery times, a risk reduction by deposit of asphaltenes, and additional70205.0690WOU1 (T-11793-WO01) savings in the use of other additives such as demulsifiers. Overall, the implementation of the present invention provides a multifactorial benefit derived from the decrease of crude oil mobility induced by the viscosity reduction as stated hereinbefore. This is a significant advantage.

[0029] A third advantage is its use offers greater flexibility and sustainability throughout the production chain, from extraction to processing, due to the use of chemical agents of low volatility in the aqueous medium, in contrast to high volatility conventional diluents such as kerosene, diesel, naphtha, condensate, natural gas and light oils, which cause a negative environmental impact and are not always available around the production area, or tend to run short, depending on the field decline.

[0030] Another advantage is flexibility in the “downstream” process steps or chain, i.e., in the processing stage. Because of better mobility and fluidity the crudes provide a better contact with a catalyst in the processing reactors. Additional improvements of the profitability of the heavy oil processing and along the production chain may be foreseen, with lesser operating costs derived from the increased oil mobility.

[0031] Additional benefits are derived from an application of the compositions in relation to formation of homogeneous water-oil emulsions, under dynamic conditions and the spontaneous emulsion breakage under static conditions. This behavior arises from the use of the compositions of the invention and this contributes further to their potential application in several stages of production, transport and processing.

[0032] The versatility of the present invention can provide a valuable service at the production site or along downstream transport stages. The injection of these products in the form of an aqueous solution, can be combined with steam or an organic dispersant, for adequate injection at the well head, or even along the discharge line, with the benefits described herein.

[0033] The application of the products mentioned herein is performed by the use of similar facilities as those used in conventional enhanced oil recovery (EOR) operations, as is known in the industry.

[0034] The following examples are provided to further illustrate the present invention. The examples are meant to only be illustrative and are not meant to be limiting.ILLUSTRATIVE EXAMPLES

[0035] Several ionic liquids were tested for their effectiveness in reducing the viscosity of heavy oil. Over a period of one year, 18 ionic liquids were tested.70205.0690WOU1 (T-11793-WO01)

[0036] Testing took place using two separate samples of heavy oil. The viscosity of these heavy oil samples ranged from 700-30,000 cP in the temperature range of 20-60°C. The API gravity of these oil samples ranged between 12-24 API, and their asphaltene content ranged from 3-11 wt%. Most of the testing was done on the oil from a first field, and some testing was done on oil from a second field.

[0037] Viscosity experiments were carried out with a Anton Paar SVM 3001 viscometer. The principle of this U-tube of rotating concentric cylinders apparatus is based on the relationship between torque and viscosity. It is stated that the torque required to turn an object in a fluid is a function of the viscosity of that fluid. The reproducibility in viscosity measurement is ± 0.35%. The equipment was calibrated using a high viscosity standard solution, APN 415. The following procedure was used for the viscosity measurement: a. Weigh out a small amount of the crude oils, about 27 g, in a glass vial. b. Mix with appropriate amounts of the ionic liquid (IL), which is previously dissolved in toluene (1 vol% IL in toluene). c. Sonicate the samples for 20 mins at room temperature and age them in 40°C oven overnight. d. Check the viscosity of freshly prepared baseline sample (10 vol% toluene in the first field oil) each time for quality check. e. Agitate the sample for about 30 secs to ensure homogeneity before each viscosity measurement. f. Carry out multiple viscosity measurements from each IL sample to confirm reproducibility of results.

[0038] Among the IL’ s tested, tri-n-octyl ammonium oleate (TO AO) was first found to show a 13.4% reduction in the viscosity of first field heavy oil at a dosage of 3v% (30,000 ppmv) when injected with a solvent of 10v% toluene. Lower concentrations (100 and 10,000 ppmv) of the same IL were tested with the first field oil to show that the impact on viscosity reduction was lower at lower concentrations.

[0039] Further testing was done to investigate the impact of another solvent on IL performance. Since toluene is an aromatic solvent, Isopar M, which is a paraffinic solvent, was tested. In this case, tri-n-octyl ammonium oleate showed 19% reduction in the first field heavy oil viscosity at 3 v% when injected with 10 v% Isopar M. Several lower concentrations of IL (1000, 5000, andlOOOO ppmv) were tested to measure the effect of70205.0690WOU1 (T-11793-WO01) concentration on oil viscosity. As seen with toluene, viscosity reduction was lower at IL lower concentrations.

[0040] This ionic liquid was also tested with another heavy oil from the second production field. In this case, tri-octyl ammonium oleate showed a 23.5% reduction in the second field heavy oil viscosity at 3 v% when injected with 10 v% Isopar M. TO AO was found to be more effective for the second field oil compared to the first field oil. The possible reason is the difference in asphaltene contents of these two oils (first field: 3.8wt% vs second field: 10.6wt%). The second field oil is also more paraffinic with 3 wt% wax and has higher sulfur content than the first field oil. As in the case of the first field oil, the viscosity reduction was lower at lower IL concentrations (1000, 5000, and 10000 ppmv).

[0041] The testing demonstrated the unique ability of tri-octyl ammonium oleate, an ionic liquid comprising an ammonium cation and a carboxylic acid based cation, to lower the viscosity of a heavy oil.

[0042] As used in this disclosure the word “comprises” or “comprising” is intended as an open-ended transition meaning the inclusion of the named elements, but not necessarily excluding other unnamed elements. The phrase “consists essentially of’ or “consisting essentially of’ is intended to mean the exclusion of other elements of any essential significance to the composition. The phrase “consisting of’ or “consists of’ is intended as a transition meaning the exclusion of all but the recited elements except for only minor traces of impurities.

[0043] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained.

[0044] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the technology are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0045] It will be clear that the compositions and methods described herein are well adapted to attain the ends and advantages mentioned as well as those inherent therein. Those skilled in the art will recognize that the methods and systems within this70205.0690WOU1 (T-11793-WO01) specification may be implemented in many manners and as such are not to be limited by the foregoing exemplified embodiments and examples. In this regard, any number of the features of the different embodiments described herein may be combined into one single embodiment and alternate embodiments having fewer than or more than all of the features herein described are possible.

[0046] As those skilled in the art will appreciate, numerous modifications and variations of the present invention are possible considering these teachings, and all such are contemplated hereby. For example, in addition to the embodiments described herein, the present invention contemplates and claims those inventions resulting from the combination of features of the invention cited herein and those of the cited prior art references which complement the features of the present invention. Similarly, it will be appreciated that any described material, feature, or article may be used in combination with any other material, feature, or article, and such combinations are considered within the scope of this invention.

[0047] All of the publications cited in this disclosure are incorporated by reference herein in their entireties for all purposes.

Claims

70205.0690WOU1 (T-11793-WO01)What is claimed is:

1. A process for reducing the viscosity of heavy oils using an ionic liquid comprising: a) preparing an ionic liquid composition comprised of an ionic liquid which is comprised of an amine based cation and a carboxylic acid-based anion; and b) introducing the ionic liquid into a production stream comprising the heavy oil.

2. The process of claim 1 , wherein the cation comprises an amine-based cation with alkane chains from C2 - C22.

3. The process of claim 2, wherein the amine-based cation with alkane chains from C2 - C22 comprises R1R2R3N.

4. The process of claim 2, wherein the amine-based cation comprises triple alkane chains with the same carbon number.

5. The process of claim 4 wherein the triple alkane chains with the same carbon number comprises (CnH2n+i)3N.

6. The process of claim 1 , wherein the anion comprises an oleic acid-based anion.

7. The process of claim 1 , wherein step a) further comprises adding a diluent.

8. The process of claim 7, wherein the diluent comprises toluene, a paraffinic fluid, condensate, or production fluid.

9. The process of claim 7 wherein the diluent comprises an aromatic solvent or a paraffinic solvent.

10. The process of claim 1 , wherein the ionic liquid in step b) comprises diluted, undiluted, or a mix of diluted and undiluted liquid.70205.0690WOU1 (T-11793-WO01)11. The process of claim 1 , wherein step b) occurs at the well head.

12. The process of claim 1 , wherein step b) occurs in a transport pipeline.

13. The process of claim 1, wherein a recovery step c) occurs, wherein the ionic liquid is recovered from the heavy oil.

14. The process of claim 13, wherein the recovered ionic liquid is re-injected or disposed.

15. The process of claim 1 , wherein introducing the ionic liquid into the production stream further comprises mixing the ionic liquid and production stream.

16. The process of claim 1, wherein the ionic liquid is introduced into the production stream at a point of extraction of heavy oil from a well in a field, during the transport of crude oil in pipelines, or in well discharge pipelines.

17. The process of claim 16, wherein the ionic liquid is introduced into the production stream during the transport of crude oil in a pipeline, with the crude oil being transported to processing facilities in the pipeline.

18. The process of claim 1 , wherein the amount of ionic liquid introduced into the production stream is controlled to achieve a desired viscosity.

19. The process of claim 18, wherein the amount of ionic liquid introduced ranges from 1000 ppmv to 50,000 ppmv.