A CO2-stimuli-responsive crude oil emulsion with both long-term stability and rapid demulsification performance for viscosity reduction of heavy oil

Abstract

The present invention discloses a CO2-stimuli responsive crude oil emulsion for reducing the viscosity of oil, which has both long-term stability and rapid demulsification properties. The CO2-stimuli responsive crude oil emulsion is composed of a heavy oil viscosity reducer and crude oil. By mass percentage, the raw material composition of the heavy oil viscosity reducer is as follows: emulsifier 0.50-1.50%, responsive agent 0.50-1.50%, water 48.50-49.50%; the responsive agent is one or several of N,N-dimethylcyclohexylamine, N,N-dimethylcyclobenzylamine, N,N-dimethylbutylamine, diethylenetriamine, N,N-dimethyldodecylamine, N,N-dimethyltetradecylamine, N,N-dimethylhexadecylamine, N,N-dimethyloctadecylamine and N,N-dimethylerucylamide-based tertiary amine. The CO2-responsive emulsion provided by the present invention only needs to introduce CO2 during demulsification without adding a demulsifier, and at the same time has long-term stability and rapid demulsification properties, so it has a very broad prospect in the transportation of heavy oil.

Description

Technical Field

[0001] The present invention relates to a CO2 stimulus-responsive crude oil emulsion for viscosity reduction of heavy oil, which has both long-term stability and rapid demulsification property, and belongs to the technical field of oil and gas field development. Background Art

[0002] Oil plays an extremely important role in the economic development of a country. With the rapid development of the Chinese economy, the crude oil production and construction in China have been further developed. Crude oil pipeline transportation refers to the transportation of crude oil through pipelines. After the crude oil extracted from the bottom of the well undergoes processes such as oil-gas separation and dehydration, it is directly transported to the refinery or transfer station through pipelines. Pipeline transportation is called the "fifth transportation method" after the four major transportation methods of railway, highway, sea transportation, and air transportation, and has unique advantages such as less initial investment, low transportation cost, high safety, environmental friendliness, and high automation level. However, the viscosities of the crude oils produced by each oilfield vary greatly, and the transportation requirements are also different. When transporting heavy oil in pipelines, the too-high viscosity of heavy oil will greatly reduce the transportation efficiency, and heavy oil is prone to adhere to the inner wall of the pipeline. The low-molecular inorganic corrosive impurities in it will gradually corrode the pipeline, and then cause the pipeline to rupture and lead to leakage accidents, resulting in significant economic losses. Therefore, it is necessary to reduce the viscosity of crude oil during transportation. How to balance the relationship between the long-term stability and simple and rapid demulsification of the emulsion has also become the focus of research in the field of emulsions in recent years.

[0003] Common heavy oil viscosity reduction methods at home and abroad currently include: heating method, diluent oil blending method, viscosity reduction by upgrading, and emulsification viscosity reduction method. The heating method uses the viscosity-temperature relationship of crude oil to reduce viscosity, and the main problem is high energy consumption and high equipment cost. The viscosity reduction by upgrading method reduces viscosity by decomposing macromolecular hydrocarbons into small-molecular hydrocarbons through carbon removal or hydrogenation. The limitation is that it has strict requirements for reaction conditions and a narrow application range. The principle of the diluent oil blending method is to reduce the concentration of resins and asphaltenes in heavy oil, and reduce the degree of entanglement of the solubles in heavy oil. The main problem is the shortage and high price of diluent oil, so economic benefits should be considered when using it. Emulsification viscosity reduction is currently the viscosity reduction method with the best effect and the widest application. First, before transportation, the heavy oil is emulsified to reduce viscosity to obtain an oil-in-water emulsion with low viscosity. At this time, the emulsion is required to have good stability; when reaching the transportation end point, the emulsion is demulsified into oil and water phases. At this time, the emulsion is required to be able to demulsify simply and quickly. The traditional method is to add an emulsifier and a demulsifier respectively, but in actual production, the problem of difficult demulsification in the later stage often occurs. Therefore, there is an urgent need for a crude oil emulsion with controllable stability to ensure good stability during its transportation, and it can be demulsified relatively simply when phase separation is required, that is, it is necessary to find a crude oil emulsion that has both long-term stability and rapid demulsification property. Summary of the Invention

[0004] The object of the present invention is to provide a CO2-responsive crude oil emulsion, which has good stability and CO2 responsiveness. Therefore, during pipeline transportation, demulsification will not occur. After reaching the transportation destination, when demulsification is required, there is no need to add a demulsifier. Only a small amount of CO2 needs to be introduced to achieve rapid demulsification, separating the oil and water phases, which not only reduces costs but is also very friendly to the environment.

[0005] The present invention first provides a viscosity reducer for heavy oil. In terms of mass percentage, the raw material composition is as follows:

[0006] Emulsifier 0.50 - 1.50%, Responsive agent 0.50 - 1.50%, Water 48.50 - 49.50%;

[0007] The responsive agent is one or more of N,N-dimethylcyclohexylamine, N,N-dimethylcyclobenzylamine, N,N-dimethylbutylamine, diethylenetriamine, N,N-dimethyldodecylamine, N,N-dimethyltetradecylamine, N,N-dimethylhexadecylamine, N,N-dimethyloctadecylamine, and N,N-dimethylerucic acid amide-based tertiary amine;

[0008] The emulsifier is one or more of sodium dodecylbenzenesulfonate, N'-long-chain alkyl-N,N-dimethylethylamidine, N,N'-dialkylethylenediamine diethylamidine, 2-alkyl-1-hydroxyethylimidazoline, N-long-chain alkyl amidinium bicarbonate, dodecyltetramethylguanidine, N,N-dimethylaminoethyl methacrylate, and 4-dimethylaminostyrene;

[0009] The water is deionized water or tap water.

[0010] The viscosity reducer for heavy oil of the present invention can reduce the viscosity of crude oil. It can be mixed with crude oil directly, and the mixing method is as follows:

[0011] Mix the emulsifier with the water to obtain an emulsifier solution as the aqueous phase. Mix the crude oil with the aqueous phase, and then add the responsive agent, and stir at a stirring speed of 300 - 800 rpm for 12 - 24 h to obtain;

[0012] The mass ratio of the viscosity reducer for heavy oil to the crude oil is 6:4 - 4:6. On the basis of the viscosity reducer for heavy oil, the present invention further provides a CO2-responsive crude oil emulsion, which is composed of the viscosity reducer for heavy oil and crude oil;

[0013] When demulsification of the crude oil emulsion is required, introduce CO2 into it at a rate of 80 - 100 mL / min for 90 - 180 s to complete demulsification.

[0014] The CO2-responsive emulsion of the present invention utilizes the good stability and CO2 responsiveness of the emulsion system. When the emulsion is transported through a pipeline, the shear force during transportation can fully maintain the stability of the emulsion, enabling it to remain in a low-viscosity emulsion state throughout the transportation process. When it reaches the transportation end point, without the need to add an additional demulsifier, complete demulsification can be achieved simply by introducing CO2 into the emulsion, which has a very broad application prospect in crude oil transportation. Currently, for the convenience of crude oil transportation, the crude oil is usually emulsified to reduce its viscosity before transportation. When it reaches the transportation end point, a demulsifier needs to be added to break the crude oil emulsion. Therefore, a large number of suitable demulsifiers need to be screened. However, the existing demulsifiers not only have a high price but also are difficult to achieve complete demulsification. The CO2-responsive emulsion of the present invention does not require the addition of a demulsifier during demulsification. Only a small amount of CO2 needs to be introduced to quickly break the emulsion and separate the oil and water phases. This not only reduces the cost but also is very friendly to the environment.

[0015] As a colorless, odorless, non-toxic, and chemically stable gas, CO2 occupies a certain proportion in the air and has the advantages of reliable source, low cost, and environmental friendliness. Therefore, the CO2-responsive emulsion has the advantages of relatively easy availability of raw materials and simple demulsification conditions. The present invention uses one or more CO2-responsive agents and surfactants together as emulsifiers to prepare the CO2-responsive emulsion, and each emulsion has good stability and rapid responsiveness. When CO2 is introduced into the emulsion, the emulsion can quickly demulsify and separate into oil and water phases. The present invention utilizes the characteristic that the amino group in the responsive agent molecule can be protonated in a CO2 atmosphere to generate a positively charged quaternary ammonium salt. The quaternary ammonium salt can then combine with the negatively charged surfactant through electrostatic interaction to form an ion pair. These ion pairs have strong hydrophobicity and dissolve in the oil phase, resulting in the surfactant being unable to arrange at the oil-water interface anymore and losing its emulsifying function, leading to the demulsification of the emulsion. Therefore, the hydrophobicity of the ion pair can be regulated by adjusting the carbon chain length of the emulsifier, and the faster the demulsification speed of the emulsion, so as to achieve the advantage of short-time demulsification.

[0016] The present invention first proposes to use the CO2-responsive emulsion to reduce the viscosity of crude oil, which is a great supplement and benefit to the current field of crude oil viscosity reduction during transportation. Usually, before transporting heavy oil, water and an emulsifier are added to form a low-viscosity water-in-oil emulsion. After transportation, a demulsifier is added to separate the oil and water. The limitation is that it is difficult to demulsify the emulsion and the oil-water separation efficiency is relatively low. The CO2-responsive emulsion provided by the present invention only needs to introduce CO2 during demulsification without the need to add a demulsifier, and at the same time has long-term stability and rapid demulsification properties. Therefore, it has a very broad prospect in heavy oil transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1Electron micrographs of the emulsion prepared in Example 1 of the present invention. Among them, the left figure is the electron micrograph of the newly prepared emulsion, and the right figure is the electron micrograph of the emulsion after being placed for one month.

[0018] Figure 2 Pictures of the crude oil emulsion (left figure) prepared in Example 1 of the present invention and the picture after demulsification (right figure).

[0019] Figure 3 Electron micrographs of the crude oil emulsion prepared in Example 1 of the present invention after being passed through CO2 for different times.

[0020] Figure 4 Electron micrographs of the emulsion prepared in Example 2 of the present invention. Among them, the left figure is the electron micrograph of the newly prepared emulsion, and the right figure is the electron micrograph of the emulsion after being placed for one month.

[0021] Figure 5 Electron micrographs of the crude oil emulsion prepared in Example 2 of the present invention after being passed through CO2 for different times.

[0022] Figure 6 Electron micrographs of the crude oil emulsion prepared in Example 3 of the present invention after being passed through CO2 for different times

[0023] Figure 7 Electron micrographs of the emulsion prepared in Example 4 of the present invention. Among them, the left figure is the electron micrograph of the newly prepared emulsion, and the right figure is the electron micrograph of the emulsion after being placed for two months.

[0024] Figure 8 Electron micrographs of the crude oil emulsion prepared in Example 4 of the present invention after being passed through CO2 for different times.

[0025] Figure 9 Pictures of the crude oil emulsion prepared in Comparative Example 1 of the present invention. Among them, the left figure is the picture of the newly prepared crude oil emulsion, and the right figure is the picture of the crude oil emulsion after standing for half an hour. Detailed implementation mode

[0026] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0027] Unless otherwise specified, the materials, reagents, etc. used in the following examples can all be obtained from commercial channels.

[0028] The method for reducing the viscosity of crude oil using the CO2-responsive crude oil emulsion system provided by the present invention can measure the viscosities of the simulated oil and the emulsion, as well as the demulsibility of the crude oil emulsion after passing through CO2, so as to judge the efficiency of the CO2-responsive crude oil emulsion system in reducing the viscosity of crude oil. The specific steps are as follows:

[0029] (1) Add an appropriate amount of emulsifier to deionized water and stir until completely dissolved to prepare an emulsifier solution with a certain concentration. Use this solution as the aqueous phase of the emulsion, use crude oil as the oil phase of the emulsion, prepare the emulsion according to the corresponding oil-water ratio, and then add a certain amount of responsive agent. Under room temperature conditions, use a magnetic stirrer to stir the emulsion at a specified stirring speed and stirring time. The emulsion is finally a uniform and stable black liquid.

[0030] (2) Press CO2 gas into the reaction kettle and introduce CO2 at a certain rate for a certain time to completely demulsify the above emulsion.

[0031] Example 1

[0032] For the CO2-responsive emulsion provided in this example, calculated by weight percentage, its raw material composition includes:

[0033] Sodium dodecylbenzenesulfonate as emulsifier 0.50 wt%, crude oil (from Shengli Oilfield) 50.00 wt%, tap water 49.00 wt%, responsive agent N,N-dimethyldodecylamine 0.50 wt%.

[0034] The CO2-responsive crude oil emulsion in this example is prepared by the following steps:

[0035] Add an appropriate amount of sodium dodecylbenzenesulfonate to tap water and stir until completely dissolved to prepare a 1.0 wt% surfactant solution, and use this surfactant solution as the aqueous phase of the emulsion. Select Shengli crude oil as the oil phase of the emulsion and prepare a total of 10 mL of solution according to a 1:1 oil-water (mass ratio). Then add 0.50 wt% N,N-dimethyldodecylamine to this solution, and use a magnetic stirrer to stir the solution at a specified stirring speed and stirring time under room temperature conditions. Finally, a uniform and stable black liquid is obtained, which is the crude oil emulsion. This emulsion can be stable for about one month under static conditions and has a certain long-term stability. As Figure 1 shown, where the left figure is the electron microscope photo of the newly prepared emulsion, and the right figure is the electron microscope photo of the emulsion after being placed for one month.

[0036] Pour the crude oil and the prepared emulsion into the sample cell respectively, and use a Brookfield viscometer of model DV-IIPro to measure the viscosity. The viscosity of the crude oil is 237.3 mPa·s, and the viscosity of the crude oil emulsion is 28.3 mPa·s. It can be seen that emulsifying the crude oil into a CO2-responsive emulsion can reduce its viscosity by about 8 times. Further, introduce CO2 into this crude oil emulsion at a rate of 80 mL / min for 90 s, and complete demulsification can be achieved after standing for 120 s, as Figure 2 and Figure 3 shown.

[0037] The results of this example show that the CO2-responsive crude oil emulsion system of the present invention is successful in reducing the viscosity of crude oil, has good long-term stability, has a rapid response to CO2, and can achieve rapid and complete demulsification by introducing CO2.

[0038] Example 2,

[0039] The CO2-responsive emulsion provided in this example, by weight percentage, its raw material composition includes:

[0040] Emulsifier N,N'-bisalkyl ethylenediamine diethylamidine 0.55 wt%, crude oil (from Gudong Oilfield) 50.00 wt%, tap water 49.00 wt%, responsive agent diethylenetriamine 0.45 wt%;

[0041] The CO2-responsive crude oil emulsion of this example is prepared by the following steps:

[0042] Add an appropriate amount of N,N'-bisalkyl ethylenediamine diethylamidine to tap water and stir until completely dissolved to prepare a 1.0 wt% surfactant solution, and use this surfactant solution as the aqueous phase of the emulsion. Select Gudong crude oil as the oil phase of the emulsion, and prepare a 10 mL solution according to an oil-water ratio (mass ratio) of 4:6. Then add 0.45 wt% diethylenetriamine to this solution, and use a magnetic stirrer to stir the solution at a specified stirring speed and stirring time at room temperature. Finally, a uniform and stable black liquid is obtained, which is the crude oil emulsion. This emulsion can be stable for about one and a half months under static conditions and has a certain long-term stability, as Figure 4 shown.

[0043] Pour the crude oil and the prepared emulsion into sample cells respectively, and use a Brookfield viscometer of model DV-IIPro to measure the viscosity. The viscosity of the crude oil is 526.4 mPa·s, and the viscosity of the crude oil emulsion is 27.5 mPa·s. It can be seen that emulsifying the crude oil into a CO2-responsive emulsion can reduce its viscosity by about 19 times. Further, introduce CO2 into this crude oil emulsion at a rate of 80 mL / min for 90 s, and complete demulsification can be achieved after standing for 90 s, as Figure 5 shown.

[0044] The results of this example show that the CO2-responsive crude oil emulsion system is successful in reducing the viscosity of crude oil, has good long-term stability, has a rapid response to CO2, and can achieve rapid and complete demulsification by introducing CO2.

[0045] Example 3,

[0046] The CO2-responsive emulsion provided in this example, by weight percentage, its raw material composition includes:

[0047] Emulsifier 2-alkyl-1-hydroxyethyl imidazoline 0.50 wt%, crude oil (from Gudong Oilfield) 50.00 wt%, tap water 49.00 wt%, responder N,N-dimethyl erucamide-based tertiary amine 0.50 wt%;

[0048] The CO2-responsive crude oil emulsion of this example is prepared by the following steps:

[0049] Add an appropriate amount of 2-alkyl-1-hydroxyethyl imidazoline to tap water and stir until completely dissolved to prepare a 1.0 wt% surfactant solution, and use this surfactant solution as the aqueous phase of the emulsion. Select Gudong crude oil as the oil phase of the emulsion, and prepare a total of 10 mL of solution according to an oil-water ratio (mass ratio) of 1:1. Then add 0.50 wt% N,N-dimethyl erucamide-based tertiary amine responder to this solution, and use a magnetic stirrer to stir the solution at a specified stirring speed and stirring time under room temperature conditions. Finally, a uniform and stable black liquid is obtained, which is the crude oil emulsion. This emulsion can be stable for about two months under static conditions and has a certain long-term stability.

[0050] Pour the prepared simulated oil and the emulsion into the sample cell respectively, and use a Brookfield viscometer of model DV-IIPro to measure the viscosity. The viscosity of the simulated oil is 526.4 mPa·s, and the viscosity of the crude oil emulsion is 39.8 mPa·s. It can be seen that emulsifying the crude oil into a CO2-responsive emulsion can reduce its viscosity by about 13 times. Further, pass CO2 into this crude oil emulsion at a rate of 80 mL / min for 90 s, and complete demulsification can be achieved after standing for 100 s, as Figure 6 shown.

[0051] The results of this example show that the CO2-responsive crude oil emulsion system is successful in reducing the viscosity of crude oil, and it has good long-term stability and rapid responsiveness to CO2. Rapid and complete demulsification can be achieved by passing CO2.

[0052] Example 4

[0053] The CO2-responsive emulsion provided in this example, by weight percentage, its raw material composition includes:

[0054] Emulsifier 2-alkyl-1-hydroxyethyl imidazoline 0.50 wt%, crude oil (from Gudong Oilfield) 50.00 wt%, tap water 49.00 wt%, responders diethylenetriamine and N,N-dimethyl erucamide-based tertiary amine each 0.25 wt%;

[0055] The CO2-responsive crude oil emulsion of this example is prepared by the following steps:

[0056] Add an appropriate amount of 2-alkyl-1-hydroxyethyl imidazoline to tap water and stir until completely dissolved to prepare a 1.0 wt% surfactant solution, and use this surfactant solution as the aqueous phase of the emulsion. Select Gudong crude oil as the oil phase of the emulsion, and prepare 10 mL of solution according to an oil-water ratio (mass ratio) of 6:4. Then add 0.25 wt% of each of the responsive agents diethylenetriamine and N,N-dimethyl erucyl amido tertiary amine to this solution, and use a magnetic stirrer to stir the solution at a specified stirring speed and stirring time under room temperature conditions. Finally, a homogeneous and stable black liquid is obtained, which is the crude oil emulsion. This emulsion can be stable for about two months under static conditions and has a certain long-term stability.

[0057] Pour the prepared simulated oil and emulsion into the sample cell respectively, and use a Brookfield viscometer of model DV-IIPro to measure the viscosity. The viscosity of the simulated oil is 1415.8 mPa·s, and the viscosity of the crude oil emulsion is 75.6 mPa·s. It can be seen that emulsifying the crude oil into a CO2-responsive emulsion can reduce its viscosity by about 20 times. Further, pass CO2 into this crude oil emulsion at a rate of 80 mL / min for 90 s, and complete demulsification can be achieved after standing for 60 s, as Figure 8 shown.

[0058] The results of this example show that the CO2-responsive crude oil emulsion system is successful in reducing the viscosity of crude oil, and it has good long-term stability, rapid responsiveness to CO2, and rapid and complete demulsification can be achieved by passing CO2.

[0059] Comparative Example 1

[0060] To illustrate the advantages of the CO2-responsive crude oil emulsion system by comparison, this comparative example prepares a crude oil emulsion without adding a CO2-responsive agent. In terms of weight percentage, its raw material composition includes:

[0061] Emulsifier sodium dodecylbenzenesulfonate 0.50 wt%, crude oil (from Shengli Oilfield) 50.00 wt%, tap water 49.50 wt%.

[0062] The crude oil emulsion of this example is prepared through the following steps:

[0063] Add an appropriate amount of sodium dodecylbenzenesulfonate to tap water and stir until completely dissolved to prepare a 1.0 wt% surfactant solution, and use this surfactant solution as the aqueous phase of the emulsion. Select Shengli crude oil as the oil phase of the emulsion, and prepare 10 mL of solution according to a 1:1 oil-water (mass ratio). Use a magnetic stirrer to stir the solution at a specified stirring speed and stirring time under room temperature conditions. Finally, a homogeneous and stable black liquid is obtained, which is the crude oil emulsion.

[0064] Pour the crude oil and the prepared emulsion into the sample cell respectively, and use a Brookfield viscometer of model DV-IIPro to measure the viscosity. The viscosity of the crude oil is 237.3 mPa·s, and the viscosity of the crude oil emulsion is 147.6 mPa·s. The viscosity of the crude oil has decreased, but the decrease amplitude is not large. However, the stability of the crude oil emulsion is very poor, and oil-water separation occurs after about half an hour, as Figure 9 shown.

[0065] The results of this example show that although the non-CO2-responsive crude oil emulsion system can reduce the viscosity of crude oil to a certain extent, its stability is poor, which is not conducive to pipeline transportation. Moreover, after oil-water separation, the water phase is turbid and complete demulsification cannot be achieved.

Claims

1. A heavy oil viscosity reducer, the raw material composition is as follows in terms of mass percentage: Emulsifier 0.50-1.50%, response agent 0.50-1.50%, water 48.50-49.50%; The responder is diethylenetriamine and / or N,N-dimethylerucic acid amide tertiary amine; The emulsifier is 2-alkyl-1-hydroxyethyl imidazoline or N,N'-bis-alkylethylenediamine diethylamidine; The water is deionized water or tap water.

2. Use of the heavy oil viscosity reducer according to claim 1 in reducing crude oil viscosity.

3. A method for reducing crude oil viscosity, comprising the step of mixing crude oil with the heavy oil viscosity reducer according to claim 1; The mass ratio of the heavy oil viscosity reducer to the crude oil is 6:4 to 4:6; The crude oil is added during the preparation of the heavy oil viscosity reducer, and the specific steps are as follows: The emulsifier is mixed with the water to obtain an emulsifier solution, which is used as a water phase, the crude oil is mixed with the water phase, and then the responder is added.

4. A CO2-responsive crude oil emulsion, which consists of the heavy oil viscosity reducer according to claim 1 and crude oil; The mass ratio of the heavy oil viscosity reducer to the crude oil is 6:4 to 4:

6.

5. The method for demulsifying a CO2-responsive crude oil emulsion according to claim 4, comprising the following steps: introducing CO2 into the CO2-responsive crude oil emulsion; The rate of introducing CO2 is 80-100 mL / min, and the time is 90-180 s.

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