Method for comprehensive modification of crude oil electromagnetic field

Abstract

The present application provides a crude oil electromagnetic field comprehensive modification method. The method comprises the following steps: heating crude oil to a first predetermined temperature above its wax precipitation point temperature and constant temperature for a first time; then cooling to a second predetermined temperature and constant temperature for a second time; then performing magnetic field treatment at the second predetermined temperature; then constant temperature at a third predetermined temperature between the wax precipitation point temperature and the freezing point temperature of the crude oil for a third time; then performing electric field treatment at the third predetermined temperature to obtain modified crude oil. The method of the present application is not a simple combination of magnetic field and electric field, but uses the effect of magnetic field on key components in crude oil to enhance the electric field viscosity reduction effect of crude oil and improve the flowability of crude oil.

Description

TECHNICAL FIELD

[0001] The present application relates to a crude oil electromagnetic field comprehensive modification method, belonging to the technical field of crude oil viscosity reduction. BACKGROUND

[0002] At ambient temperature, the crystallization and precipitation of wax in crude oil deteriorate the flowability of crude oil, which poses a serious challenge to crude oil production and long-distance pipeline transportation. Under the dual-carbon target, intermittent transportation and low-throughput operation of crude oil pipelines will become the norm, and it is urgent to develop and optimize the crude oil modification method (i.e., using physical and chemical methods to improve the flowability of crude oil).

[0003] High-voltage electric field modification is a new, efficient and low-energy method for crude oil modification. By applying an electric field to crude oil near its freezing point for a few seconds, the flowability of crude oil is significantly improved (the viscosity of crude oil can be reduced by more than 90%), and the energy consumption of electric field modification is only 1% of the heating energy consumption to achieve the same viscosity reduction. However, this method still has the limitation of significant differences in effect on different crude oils.

[0004] Improving the universality of the high-voltage electric field modification method and enhancing the electric field viscosity reduction effect will help to break through the technical bottleneck of industrial application of the electric field modification method for crude oil. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide a crude oil electromagnetic field comprehensive modification method. The method of the present application utilizes the action of magnetic field on key components in crude oil to enhance the electric field viscosity reduction effect of crude oil and improve the flowability of crude oil.

[0006] To achieve the above-mentioned purpose, the present application provides a crude oil electric-magnetic field comprehensive modification method, which comprises the following steps:

[0007] The crude oil is heated to a first predetermined temperature above its wax dissolution point temperature and kept at the first temperature for a first time; then cooled to a second predetermined temperature and kept at the second temperature for a second time; and then subjected to magnetic field treatment at the second predetermined temperature;

[0008] Then, the crude oil is kept at a third predetermined temperature between the wax precipitation point temperature and the freezing point temperature for a third time; and then subjected to electric field treatment at the third predetermined temperature to obtain modified crude oil.

[0009] In the above method, preferably, the crude oil includes one or a combination of several of low-wax crude oil, waxy crude oil and high-wax crude oil.

[0010] In the above method, preferably, the wax content of the crude oil is 3wt%-25wt%.

[0011] In the above method, preferably, the water content of the crude oil is less than or equal to 1wt%.

[0012] In the above method, preferably, the crude oil is a waxy crude oil, and the (gum content + asphaltene content) / waxy content (i.e., gum to wax ratio) of the waxy crude oil is 0.5 to 1, more preferably 0.7 to 1.

[0013] In the above method, preferably, the heating rate of the crude oil to the first predetermined temperature above the wax dissolution point temperature of the crude oil is 0.2 to 2°C / min.

[0014] In the above method, the first predetermined temperature can be any temperature above the wax dissolution point temperature of the crude oil. Preferably, the first predetermined temperature is 1 to 25°C above the wax dissolution point temperature of the crude oil.

[0015] In the above method, preferably, the first time is 30 min or more, more preferably 30 to 60 min.

[0016] In the above method, preferably, the cooling rate from the first predetermined temperature to the second predetermined temperature is 0.2 to 2°C / min.

[0017] In the above method, preferably, the second predetermined temperature is 10°C above the wax precipitation point temperature of the crude oil to the third predetermined temperature (i.e., the electric field treatment temperature). More preferably, the second predetermined temperature is 3 to 7.5°C above the wax precipitation point temperature of the crude oil.

[0018] In the above method, preferably, the second time is 5 min or more, more preferably 5 to 20 min.

[0019] In the above method, preferably, the magnetic field strength of the magnetic field treatment is 50 to 2000 mT, more preferably 50 to 300 mT.

[0020] In the above method, preferably, the time of the magnetic field treatment is 1 to 10 min, more preferably 1 to 3 min.

[0021] In the above method, preferably, the cooling rate from the second predetermined temperature to the third predetermined temperature is 0.2 to 2°C / min.

[0022] In the above method, preferably, the third predetermined temperature is 2 to 5°C above the freezing point temperature of the crude oil.

[0023] In the above method, preferably, the third time is 1 to 30 min.

[0024] In the above method, preferably, the electric field applied in the electric field treatment includes one or a combination of several of a direct current electric field, an alternating current electric field, and a pulse electric field.

[0025] In the above method, preferably, the electric field strength of the electric field treatment is 0.1 kV / mm-10 kV / mm.

[0026] In the above method, preferably, the time of the electric field treatment is 10 s or more, more preferably 10-600 s.

[0027] The present application provides a crude oil electromagnetic field comprehensive modification method. The method of the present application is not a simple combination of magnetic field and electric field, but uses the action of magnetic field on key components in crude oil to enhance the effect of electric field viscosity reduction of crude oil and improve the flowability of crude oil. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The flowchart of the crude oil electromagnetic field comprehensive modification method provided in the detailed description of the present application. DETAILED DESCRIPTION

[0029] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application will be described in detail below, but it should not be understood as limiting the scope of the present application.

[0030] According to the specific embodiments of the present application, preferably, the present application provides a crude oil electromagnetic field comprehensive modification method, as shown in Figure 1 which comprises the following steps:

[0031] The crude oil is heated to a first predetermined temperature above its wax dissolution point temperature and kept at the first temperature for a first time; then cooled to a second predetermined temperature and kept at the second temperature for a second time; and then subjected to magnetic field treatment at the second predetermined temperature;

[0032] then cooled to a third predetermined temperature between the wax precipitation point temperature and the freezing point temperature of the crude oil and kept at the third temperature for a third time; and then subjected to electric field treatment at the third predetermined temperature to obtain the modified crude oil.

[0033] In some embodiments, the crude oil includes one or a combination of several of low-wax crude oil, waxy crude oil and high-wax crude oil. The wax content of the crude oil is 3wt%-25wt%. The water content of the crude oil is 1wt% or less. According to the specific embodiments of the present application, the crude oil treated by the present application is preferably dehydrated crude oil, which can meet the long-distance transportation standard, and the water content is not more than 1wt%. Preferably, the crude oil is waxy crude oil, and the (gum content+asphaltene content) / wax content of the waxy crude oil (i.e. gum wax ratio) is 0.5-1, more preferably 0.7-1.

[0034] In some embodiments, the heating rate of the crude oil to a first predetermined temperature above its wax dissolution point temperature is 0.2-2℃ / min.

[0035] In some embodiments, the first predetermined temperature is 1-25°C above the wax appearance point temperature of the crude oil.

[0036] In some embodiments, the first time is 30 min or more, preferably 30-60 min.

[0037] In some embodiments, the cooling rate from the first predetermined temperature to the second predetermined temperature is 0.2-2°C / min.

[0038] In some embodiments, the second predetermined temperature is 10°C above the wax appearance point temperature of the crude oil, preferably 3-7.5°C above the wax appearance point temperature of the crude oil, to the third predetermined temperature (i.e. the electric field treatment temperature).

[0039] In some embodiments, the second time is 5 min or more, preferably 5-20 min.

[0040] In some embodiments, the magnetic field strength of the magnetic field treatment is 50-2000 mT, preferably 50-300 mT.

[0041] In some embodiments, the time of the magnetic field treatment is 1-10 min, preferably 1-3 min.

[0042] In some embodiments, the cooling rate from the second predetermined temperature to the third predetermined temperature is 0.2-2°C / min.

[0043] In some embodiments, the third predetermined temperature is 2-5°C above the pour point temperature of the crude oil.

[0044] In some embodiments, the third time is 1-30 min.

[0045] In some embodiments, the electric field applied in the high-voltage electric field treatment comprises one or a combination of several of a direct current electric field, an alternating current electric field, and a pulsed electric field.

[0046] In some embodiments, the electric field strength of the high-voltage electric field treatment is 0.1 kV / mm-10 kV / mm.

[0047] In some embodiments, the time of the high-voltage electric field treatment is 10 s or more, preferably 10-600 s.

[0048] The technical solutions of the present application are specifically illustrated below by examples, comparative examples, but the present application is not limited to these examples, and of course various modifications can be made within the scope of the gist of the present application.

[0049] Example 1

[0050] The selected oil sample is a typical waxy crude oil #1, and the basic properties and test methods thereof are shown in Table 1.

[0051] Table 1 Basic properties and test methods of waxy crude oil #1

[0052]

[0053] The waxy crude oil #1 was heated to 70℃ (above the wax dissolution point temperature) at a heating rate of 2℃ / min and kept constant for 30min, then cooled to 37℃ (6.1℃ above the wax precipitation point temperature) at a cooling rate of 0.5℃ / min and kept constant for 10min, then subjected to magnetic field treatment at 37℃, the magnetic field strength was 100mT, and the treatment time was 1min. Then the crude oil after magnetic field treatment was loaded into a rheometer and cooled to 20℃ (2℃ above the freezing point temperature) at a cooling rate of 0.5℃ / min and kept constant for 10min, then subjected to high-voltage electric field treatment, the electric field was a direct current electric field, the electric field strength was 2kV / mm, and the treatment time was 3min, to obtain the modified crude oil.

[0054] As a comparison, the waxy crude oil #1 without magnetic field treatment was loaded into a rheometer at 37℃, cooled to 20℃ at a cooling rate of 0.5℃ / min and kept constant for 10min, then subjected to high-voltage electric field treatment, the electric field was a direct current electric field, the electric field strength was 2kV / mm, and the treatment time was 3min, to obtain the modified crude oil.

[0055] The results are shown in Table 2.

[0056] Table 2 Effect of electromagnetic comprehensive action on waxy crude oil #1 (magnetic field treatment at 37℃, electric field treatment at 20℃)

[0057]

[0058]

[0059] The formula for calculating the viscosity reduction rate is 10s -1 before electric field treatment -1 The equilibrium viscosity is η E , and the viscosity reduction rate is:

[0060] Δη=(η0-η E ) / η0×100%.

[0061] As can be seen from Table 2, the viscosity reduction rate of the crude oil which is not subjected to the magnetic field treatment and only subjected to the electric field treatment is only 43.2%, while the viscosity reduction rate of the crude oil which is subjected to the magnetic field treatment and then subjected to the electric field treatment is increased to 66.7%, that is, the method of the present application can significantly improve the electric field viscosity reduction effect. It is worth noting that the magnetic field treatment above the wax precipitation point temperature has almost no effect on the viscosity of the crude oil, and even slightly improves the viscosity, so the present application is not a simple superposition of the electric field treatment and the magnetic field treatment.

[0062] Subsequently, for the waxy crude oil #1, the effect of different magnetic field treatment times on the modification effect of the crude oil was studied, the magnetic field strength was fixed at 100 mT, the treatment time was 1 min, 3 min, 10 min and 20 min, respectively, and the other steps and conditions were the same. The results are shown in Table 3.

[0063] Table 3 Effect of magnetic field treatment time on modification effect

[0064]

[0065] As can be seen from Table 3, when the magnetic field treatment time is 1-10 min, the electromagnetic comprehensive treatment can improve the electric field viscosity reduction effect; but when the magnetic field treatment time is increased to 20 min, the viscosity of the crude oil after the comprehensive action is even higher than that of the crude oil after the electric field action only. Therefore, the magnetic field treatment time of the present application is 1-10 min, preferably 1-3 min.

[0066] As a comparison, the waxy crude oil #1 was subjected to the electromagnetic comprehensive treatment outside the electric field treatment temperature range to be controlled in the present application, and the specific steps were as follows: the waxy crude oil #1 was heated to 70℃ (above the wax dissolution point temperature) at a heating rate of 2℃ / min and kept constant for 30 min, then cooled to 37℃ (6.1℃ above the wax precipitation point temperature) at a cooling rate of 0.5℃ / min and kept constant for 10 min, then subjected to the magnetic field treatment at 37℃, the magnetic field strength was 100 mT, and the treatment time was 1 min. Then the modified crude oil after the magnetic field treatment was loaded into a rheometer and cooled to 32℃ at a cooling rate of 0.5℃ / min and kept constant for 10 min, then subjected to the high-voltage electric field treatment, the electric field was a direct current electric field, the electric field strength was 2 kV / mm, and the treatment time was 3 min, to obtain the modified crude oil. The result is: the viscosity reduction rate is 0%.

[0067] As a comparison, the first predetermined temperature of heating the crude oil to above its wax precipitation point temperature and the step of constant temperature for the first time were omitted, and the waxy crude oil #1 was subjected to electromagnetic comprehensive treatment. The specific steps were as follows: the waxy crude oil #1 was subjected to magnetic field treatment at 37°C (6.1°C above the wax precipitation point temperature) for 10 min, the magnetic field strength was 100 mT, and the treatment time was 1 min. Subsequently, the crude oil modified by the magnetic field treatment was loaded into a rheometer, and the temperature was lowered to 20°C (2°C above the freezing point temperature) at a cooling rate of 0.5°C / min and was kept constant for 10 min, and then high-voltage electric field treatment was performed. The electric field was a direct current electric field, the electric field strength was 2 kV / mm, and the treatment time was 3 min, to obtain the modified crude oil. The result was that the viscosity reduction rate was 15%.

[0068] Example 2

[0069] The selected oil sample was a certain typical waxy crude oil #2, and the basic properties and test methods are shown in Table 4.

[0070] Table 4 Basic properties and test methods of waxy crude oil #2

[0071]

[0072] The waxy crude oil #2 was heated to 80°C (above the wax precipitation point temperature) at a heating rate of 1°C / min and was kept constant for 30 min, and then was cooled to 67°C (7.3°C above the wax precipitation point temperature) at a cooling rate of 0.5°C / min and was kept constant for 10 min, and then was subjected to magnetic field treatment at 67°C, the magnetic field strength was 100 mT, and the treatment time was 1 min. Subsequently, the crude oil modified by the magnetic field treatment was loaded into a rheometer, and the temperature was lowered to 34°C (2°C above the freezing point temperature) at a cooling rate of 0.5°C / min and was kept constant for 10 min, and then high-voltage electric field treatment was performed. The electric field was a direct current electric field, the electric field strength was 2 kV / mm, and the treatment time was 3 min, to obtain the modified crude oil.

[0073] As a comparison, the waxy crude oil #2 without magnetic field treatment was loaded into a rheometer at 67°C, and the temperature was lowered to 34°C at a cooling rate of 0.5°C / min and was kept constant for 10 min, and then high-voltage electric field treatment was performed. The electric field was a direct current electric field, the electric field strength was 2 kV / mm, and the treatment time was 3 min, to obtain the modified crude oil.

[0074] The results are shown in Table 5.

[0075] Table 5 Electromagnetic comprehensive effect of waxy crude oil #2 (magnetic field treatment at 67°C, electric field treatment at 34°C)

[0076]

[0077] As can be seen from Table 5, the viscosity of crude oil #2 cannot be reduced by the electric field treatment alone or the magnetic field treatment alone; and the viscosity reduction rate of the crude oil can reach 13.6% after the magnetic field treatment followed by the electric field treatment. This embodiment again illustrates that the present application is not a simple superposition of the two modification methods.

[0078] Comparative Example 1

[0079] As a comparison, a typical waxy crude oil #3 was selected for the experiment, and the basic properties and test methods thereof are shown in Table 6.

[0080] Table 6 Basic properties and test methods of waxy crude oil #3

[0081]

[0082] It can be seen that the gel wax ratio of the waxy crude oil #3, i.e., the ratio of the content of gum and asphaltene to the wax content (i.e., the gel wax ratio) is 2.04, which is not within the scope of the present application.

[0083] The waxy crude oil #3 was heated to 60°C (above the wax dissolution point temperature) at a heating rate of 1°C / min and kept at 60°C for 30 min, then cooled to 30°C (6°C above the wax precipitation point temperature) at a cooling rate of 0.5°C / min and kept at 30°C for 10 min, and then subjected to a magnetic field treatment at 30°C, the magnetic field strength was 100 mT, and the treatment time was 1 min. Then the crude oil modified by the magnetic field treatment was loaded into a rheometer and cooled to 18°C (2°C above the freezing point temperature) at a cooling rate of 0.5°C / min and kept at 18°C for 10 min, and then subjected to a high-voltage electric field treatment, the electric field was a direct current electric field, the electric field strength was 2 kV / mm, and the treatment time was 3 min, to obtain the modified crude oil.

[0084] As a comparison, the waxy crude oil #3 without the magnetic field treatment was loaded into a rheometer at 60°C, cooled to 18°C at a cooling rate of 0.5°C / min and kept at 18°C for 10 min, and then subjected to a high-voltage electric field treatment, the electric field was a direct current electric field, the electric field strength was 2 kV / mm, and the treatment time was 3 min, to obtain the modified crude oil.

[0085] The results are shown in Table 7.

[0086] Table 7 Effect of electromagnetic comprehensive action on waxy crude oil #3 (magnetic field treatment at 30°C, electric field treatment at 18°C)

[0087]

[0088] In summary, the crude oil electromagnetic field comprehensive modification method greatly improves the viscosity reduction effect of crude oil 1, has the electric field viscosity reduction effect on crude oil 2 with excessively high gum content, and cannot improve the electric field viscosity reduction effect of crude oil 3 with a gum-wax ratio out of the range of the application. Therefore, the application improves the crude oil modification effect by using the multi-physical field comprehensive treatment method for specific waxy crude oil, and significantly improves the flowability of the crude oil.

Claims

1. A method for comprehensive electromagnetic field modification of crude oil, comprising the following steps: The crude oil is heated to a first predetermined temperature above its melting point and held at that temperature for a first time of at least 30 minutes; then cooled to a second predetermined temperature and held at that temperature for a second time; and then subjected to magnetic field treatment at the second predetermined temperature for 1-3 minutes. Then, the crude oil is kept at a predetermined temperature between the wax precipitation point and the pour point for a third time; subsequently, it is subjected to electric field treatment under the third predetermined temperature condition to obtain the modified crude oil. Wherein, the crude oil is waxy crude oil, and the (colloid content + asphaltene content) / wax content of the waxy crude oil is 0.5-1; the second predetermined temperature is the third predetermined temperature to 10°C above the wax precipitation point temperature of the crude oil.

2. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The crude oil has a wax content of 3wt%-25wt% and a water content of less than 1wt%.

3. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The waxy crude oil has a (colloidal content + asphaltene content) / wax content ratio of 0.7-1.

4. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The heating rate for raising the crude oil to a first predetermined temperature above its melting point is 0.2-2°C / min.

5. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The cooling rate from the first predetermined temperature to the second predetermined temperature is 0.2-2°C / min.

6. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The second time is 5 minutes or more.

7. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The magnetic field strength for the magnetic field treatment is 50-2000 mT.

8. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The cooling rate from the second predetermined temperature to the third predetermined temperature is 0.2-2°C / min.

9. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The third predetermined temperature is 2-5°C above the crude oil pour point temperature; the third time is 1-30 min.

10. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The electric field applied by the electric field treatment includes one or a combination of several of the following: DC electric field, AC electric field, and pulsed electric field.

11. The method for comprehensive electromagnetic field modification of crude oil according to claim 1, wherein, The electric field strength for the electric field treatment is 0.1 kV / mm-10 kV / mm; the electric field treatment time is more than 10 s.

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