Asphaltene sediment dispersing agent based on dielectric constant measurement and preparation method
By matching the dielectric constants of toluene and ethanol mixed solutions, the problem that a single solvent is difficult to disperse complex asphaltene deposits in heavy oil is solved, and efficient and low-cost asphaltene dispersion and dissolution effects are achieved.
Patent Information
- Application Number
- CN202410259043.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-07
- Publication Date
- 2025-09-09
AI Technical Summary
In the existing technology, a single solvent is difficult to effectively disperse the complex asphaltene deposits in heavy oil, especially the layered inclusions containing components such as rock fragments and polymers, resulting in increased energy consumption and higher costs during the mining process.
A mixed solution of toluene and ethanol is used. By measuring the dielectric constant of asphaltene deposits, a mixing ratio with similar or equal dielectric constants is selected to improve the dispersion and dissolution ability of asphaltene deposits and reduce energy consumption.
It achieves effective dispersion and dissolution of asphaltene deposits at room temperature and high temperature, reduces energy consumption and processing costs, and improves the environmental protection and economy of the dispersant.
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Figure CN120607882A_ABST
Abstract
Description
Technical Field
[0001] The patent of this invention belongs to the field of heavy oil reservoir exploitation, and specifically relates to an asphaltene sediment dispersant based on dielectric constant measurement and a preparation method. Background Art
[0002] In order to improve oil recovery, different production-increasing measures need to be adopted according to the reservoir properties of different oil fields, such as secondary oil recovery, tertiary oil recovery, and carbon dioxide flooding. The application of these measures changes the physical properties of the crude oil in the reservoir, and the risk of asphaltene aggregation in the crude oil increases. In addition, during the production of heavy oil, as the oil gradually migrates from the reservoir to the surface, the pressure and temperature of the system will inevitably change, exacerbating the risk of asphaltene and colloid aggregation. Furthermore, during the drilling and oil production process, some rock cuttings in the formation will be dispersed in the oil, and interact with the polar molecules (asphaltene and colloid) and non-polar molecules (wax) in the oil through adsorption and other interactions, leading to the formation of asphaltene deposits.
[0003] Wax, asphaltenes, and colloids in heavy oil significantly impact crude oil properties. Asphaltenes, the heaviest polar component in crude oil, possess a high dielectric constant, making their impact significant. Asphaltenes are susceptible to precipitation under the influence of temperature and pressure fluctuations. These precipitations can serve as crystallization nuclei for wax molecules, altering the wax gel point temperature and yield stress. This can increase energy consumption during extraction, necessitating the use of chemical and physical methods to reduce extraction costs. Therefore, inhibiting asphaltene precipitation and dissolving any existing precipitation are crucial.
[0004] Currently, commonly used asphaltene deposit dispersants are primarily composed of aromatic solvents (e.g., single solvents such as xylene and toluene), which are toxic and relatively expensive. Furthermore, the composition of asphaltene deposits formed in oil wells is highly complex, containing asphaltenes, colloids, minerals such as rock fragments, wax precipitated from crude oil, and polymers added during oil production stimulation and flooding. Therefore, using a single aromatic solvent for oil recovery can only effectively disperse asphaltenes, colloids, and wax crystals, but not rock fragments and polymers. Using a single high-dielectric-constant solvent (ethanol), while effective in dispersing rock fragments and polymers, is ineffective in dispersing asphaltene and colloids. Because asphaltene deposits formed in oil wells are often complex mixtures, and mixtures often gradually form from various components, asphaltene deposits primarily manifest as layered inclusions composed of different types of substances. Therefore, using either a single polar or non-polar solvent effectively disperses and dissolves these inclusions. Summary of the Invention
[0005] In order to solve the above problems in the prior art, the present invention provides a method for determining the preferred asphaltene deposit dispersant based on dielectric constant.
[0006] The technical solutions of the present invention are as follows:
[0007] A dispersant for asphaltene deposits based on dielectric constant measurement is characterized by being a mixed solution of toluene and ethanol, wherein the dielectric constant of the mixed solution is equal to or differs within 5% of the dielectric constant of the asphaltene deposits.
[0008] The above-mentioned method for preparing an asphaltene sediment dispersant based on dielectric constant measurement is characterized in that it comprises the following steps:
[0009] First, the dielectric constant of the asphaltene sediment is measured, and then a mixed solution of toluene and ethanol with a dielectric constant equal to or close to that of the asphaltene sediment is determined as a dispersant.
[0010] Preferably, the method specifically includes:
[0011] ① Prepare several asphaltene solutions with different mass fractions, where the asphaltene mass percentage = solid asphaltene mass / total solution mass * 100%:
[0012] A certain amount of asphaltene sediment is mixed with toluene, and heated under reflux to fully dissolve to prepare a mother liquor;
[0013] The mother liquor was accurately weighed, placed in a vacuum drying oven and heated to dry to evaporate the toluene, and then the mass of the solid asphaltene was accurately weighed to calculate the percentage of asphaltene in each portion of the asphaltene mother liquor.
[0014] ② Use the mother liquor to prepare five asphaltene solutions with different mass fractions and the same total weight, and measure their capacitance values respectively:
[0015] The dielectric constant of asphaltene solution is calculated according to formula (1):
[0016]
[0017] Among them C i is the solution capacitance, pF,
[0018] C r is the residual capacitance value, pF,
[0019] C o is the air capacitance value, pF,
[0020] The curve is obtained by plotting the mass percentage against the dielectric constant of the asphaltene solution, and the dielectric constant is obtained by extrapolating to the case where the mass percentage of asphaltene is 100%, which is used as the dielectric constant of solid asphaltene.
[0021] According to formula (2), the dielectric constant of the mixture of ethanol and toluene is calculated.
[0022] ε=n1ε1+n2ε2 (2)
[0023] where n1ε1 is the mole fraction and dielectric constant of ethanol,
[0024] Where n2ε2 is the molar constant and dielectric constant of toluene,
[0025] A mixed solution of toluene and ethanol was prepared as a dispersant based on the calculated dielectric constant of the mixed solution.
[0026] The extracted and dried asphaltene is not easily soluble in toluene at room temperature, so it needs to be heated and refluxed in an oil pan to dissolve it. However, during the heating and reflux process, a certain amount of toluene will inevitably be volatilized and lost, so the mother liquor needs to be partially dried again after the reflux to obtain its accurate concentration.
[0027] Preferably, five asphaltene solutions with different mass fractions are prepared.
[0028] Preferably, asphaltene solutions are prepared with mass fractions of 1.5, 2, 4, 5, or 7 percent.
[0029] More preferably, after heating and reflux, asphaltene solutions with a total weight of 8 g are respectively prepared.
[0030] More preferably, after heating and reflux, asphaltene solutions with a total weight of 8 g and mass fractions of 1.5, 2, 4, 5, and 7 percent are respectively prepared.
[0031] The beneficial technical effects of the present invention are as follows:
[0032] The present invention aims to identify a ratio that is beneficial for dissolving asphaltene by mixing toluene and ethanol, measuring the dielectric constant of asphaltene deposits, and calculating the dielectric constant of the mixed solvent. Verification has shown that solvents with similar dielectric constants are more effective at dissolving asphaltene. This theoretical calculation guides the optimal mixing ratio for dissolving asphaltene deposits.
[0033] Based on the understanding of the composition of asphaltene sediments and the differences in the dispersing effects of mixed solvents with different dielectric constants on different components in the sediments, the present invention analyzes the composition of asphaltene sediments and, based on the composition characteristics of asphaltene sediments, preferably obtains a solvent compound system with different dielectric constants. By mixing a high dielectric constant solvent (ethanol) with a low dielectric constant solvent (toluene) in a certain ratio, the composition and dispersibility of the compound solvent are matched with the asphaltene sediments, thereby changing the defect that the dielectric constant of a single solvent cannot be changed, so as to achieve a dielectric constant close to that of the solvent and the asphaltene sediments to improve its dispersion and dissolving power. In addition, the addition of ethanol can form a binary mixed solution with toluene to lower the boiling point of the mixture, reduce the separation temperature of the later solvent separation process, and reduce the energy consumption of the subsequent separation process. The separated ethanol can be used as a gasoline additive. Therefore, the mixture of ethanol and toluene is selected to not only dissolve asphaltene sediments, but also reduce the energy consumption problem of subsequent treatment and the advantage of ethanol being reused.
[0034] This invention abandons the existing single-solvent asphaltene dispersing and unblocking agents and introduces a more efficient, inexpensive, environmentally friendly, and low-toxic compounded solvent. This design addresses the varying dielectric constants exhibited by asphaltene in different regions, resulting in a more effective composite unblocking agent. Compared to single solvents, this invention effectively disperses and dissolves asphaltene deposits at both room and elevated temperatures. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 This is the dielectric constant and mass fraction curve of asphaltene solution in Example 7. DETAILED DESCRIPTION
[0036] The present invention will be further described in detail below through specific embodiments, but this does not limit the technical solution of the present invention. All changes or equivalent substitutions based on the present invention should fall within the scope of protection of the present invention.
[0037] Example 1
[0038] After 3 hours of stirring on a magnetic stirrer, 0.2198 g of asphaltene plugging material and 15 mL of ethanol were observed to form a precipitate at the bottom of the beaker. After 24 hours of stabilization, distinct stratification was observed. Microscopic images of the dispersed solids after shaking showed that they tended to aggregate and were irregular in shape.
[0039] Example 2
[0040] Weigh 0.2007 g of asphaltene sediment, 5 mL of toluene, and 10 mL of ethanol, place them on a magnetic stirrer and stir for 3 hours. A small amount of precipitation can be seen at the bottom of the cup. After standing for 24 hours, obvious stratification occurs. After shaking, microscope photos show that the asphaltene particles are irregular in shape and vary greatly in size.
[0041] Example 3
[0042] Weigh 0.1992 g of asphaltene sediment, 7.5 mL of toluene, and 7.5 mL of ethanol, place them on a magnetic stirrer and stir for 3 hours. A small amount of precipitation can be seen at the bottom of the cup. After standing for 24 hours, the precipitation at the bottom of the cup increases slightly. After shaking, microscope photos show that the asphaltene particles are relatively regular in shape and have small size differences.
[0043] Example 4
[0044] Weigh 0.2021 g of asphaltene sediment, 10 mL of toluene, and 5 mL of ethanol, place them on a magnetic stirrer and stir for 3 hours. After standing for 24 hours, a small amount of precipitation appears at the bottom of the cup. After shaking, microscope photos show that the asphaltene particles are relatively regular in shape and vary greatly in size.
[0045] Example 5
[0046] Weigh 0.1964 g of asphaltene sediment, 15 mL of toluene, and 2.5 mL of ethanol, place them on a magnetic stirrer and stir for 3 hours. After standing for 24 hours, a small amount of precipitation appears at the bottom of the cup. After shaking, microscope photos show that the asphaltene particles vary greatly in size.
[0047] Example 6
[0048] Weigh 0.2048 g of asphaltene sediment, 13.5 mL of toluene, and 1.5 mL of ethanol, place them on a magnetic stirrer and stir for 3 hours. After standing for 24 hours, there is no obvious precipitation at the bottom of the cup. Microscope photos show that the asphaltene blockage is dissolved more dispersedly and the size is relatively uniform.
[0049] In Examples 1-6, the proportion of toluene increases and the proportion of ethanol decreases. Toluene has a low dielectric constant and ethanol has a high dielectric constant. According to Formula 2, it can be concluded that the dielectric constant of the dispersion system will decrease accordingly with the addition of toluene. A series of dispersion systems with different dielectric constants can be obtained under different ratios of toluene to ethanol. By comparing the dispersion of asphaltene deposits in dispersion systems with different dielectric constants, it can be seen that when the dielectric constant of the dispersion system is the same as or close to the dielectric constant of the asphaltene deposit, the dispersion effect is better. This is verified with the conclusion of the invention. Example 7
[0050] 7.1 Calculation of asphaltene content in mother liquor
[0051] The asphaltene mother liquor accurately weighed is 3.4975 g.
[0052] The mass of the asphaltene solid remaining after drying is 0.5911 g.
[0053] The asphaltene percentage in the mother liquor is 0.169.
[0054] 7.2 Calculation of the dielectric constant of solid asphaltene
[0055] 7.1 provides an accurate asphaltene concentration for 7.2. Because the dissolution of asphaltene in toluene requires a heating and reflux step, the concentration of the asphaltene mother liquor when first prepared is approximate. In 7.1, a certain mass of solution is dried to obtain the accurate asphaltene concentration in the mother liquor, thereby obtaining a certain asphaltene concentration in the mother liquor, providing a more accurate asphaltene concentration for the dilution calculation in 7.2.
[0056] Table 1 Dielectric constant measurement data of solid asphaltene
[0057] Mother liquor mass / g Solution mass / g Asphaltene mass percentage Solution capacitance / pF Solution dielectric constant / pF 0.7183 8.0281 1.51 12.285 1.3388 0.9496 8.0272 2 12.393 1.3540 1.8958 8.0963 3.96 13.003 1.4403 2.2970 8.0784 4.81 13.348 1.4891
[0058] The dielectric constant measurement data of asphaltene toluene solutions with different concentrations are shown in Table 1. The relationship between mass fraction and dielectric constant is plotted as follows: Figure 1 .
[0059] according to Figure 1 When extrapolated to an asphaltene mass fraction of 100%, the dielectric constant of the asphaltene plugging is 5.568.
[0060] 7.3 Dielectric Constants of Different Ethanol-Toluene Mixtures
[0061] The corresponding dielectric constants of the different dispersion systems used in the experiment were calculated using Formula 2 and are shown in Table 2.
[0062] Table 2 Dielectric constants of ethanol and toluene mixed system
[0063] Ratio ethanol:toluene Dielectric constant pF 1:0 24.30 2:1 19.55 1:1 16.49 1:2 12.79 0:1 2.37
[0064] 7.4 Calculation of the theoretical optimal ethanol to toluene ratio
[0065] According to formula (2) and the measured dielectric constant of solid asphaltene sediment, the optimal ethanol to toluene ratio can be calculated to be 1.5:13.5.
[0066] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined in the claims.
Claims
1. An asphaltene sediment dispersant based on dielectric constant determination, characterized in that The mixed solution is a mixture of toluene and ethanol, and the dielectric constant of the mixed solution is equal to or within 5% of the dielectric constant of the asphaltene sediment.
2. The method for preparing an asphaltene sediment dispersant based on dielectric constant measurement according to claim 1, characterized in that The following steps are involved: First, the dielectric constant of the asphaltene sediment is measured, and then a mixed solution of toluene and ethanol with a dielectric constant equal to or close to that of the asphaltene sediment is determined as a dispersant.
3. The method according to claim 2, characterized in that Specifically include: ① Prepare several asphaltene solutions with different mass fractions, where the asphaltene mass percentage = solid asphaltene mass / total solution mass * 100%: A certain amount of asphaltene sediment is mixed with toluene, and heated under reflux to fully dissolve to prepare a mother liquor; The mother liquor was accurately weighed, placed in a vacuum drying oven and heated to dry to evaporate the toluene, and then the mass of the solid asphaltene was accurately weighed to calculate the percentage of asphaltene in each portion of the asphaltene mother liquor. ② Use the mother liquor to prepare five asphaltene solutions with different mass fractions and the same total weight, and measure their capacitance values respectively: The dielectric constant of asphaltene solution is calculated according to formula (1): Among them C i is the solution capacitance, pF, C r is the residual capacitance value, pF, C o is the air capacitance value, pF, The curve is obtained by plotting the mass percentage against the dielectric constant of the asphaltene solution, and the dielectric constant is obtained by extrapolating to the case where the mass percentage of asphaltene is 100%, which is used as the dielectric constant of solid asphaltene. According to formula (2), the dielectric constant of the mixture of ethanol and toluene is calculated. ε=n1ε1+n2ε2 (2) where n1ε1 is the mole fraction and dielectric constant of ethanol, Where n2ε2 is the molar constant and dielectric constant of toluene, A mixed solution of toluene and ethanol was prepared as a dispersant based on the calculated dielectric constant of the mixed solution. The extracted and dried asphaltene is not easily soluble in toluene at room temperature, so it needs to be heated and refluxed in an oil pan to dissolve it. However, during the heating and reflux process, a certain amount of toluene will inevitably be volatilized and lost, so the mother liquor needs to be partially dried again after the reflux to obtain its accurate concentration.
4. The method according to claim 2, characterized in that Five asphaltene solutions with different mass fractions were prepared.
5. The method according to claim 4, characterized in that Asphaltene solutions with mass fractions of 1.5, 2, 4, 5, and 7 percent were prepared.
6. The method according to claim 5, characterized in that After heating to reflux, asphaltene solutions with a total weight of 8 g were prepared respectively.
7. The method according to claim 6, characterized in that After heating and reflux, asphaltene solutions with a total weight of 8 g and mass fractions of 1.5, 2, 4, 5, and 7 percent were prepared respectively.