A multi-chemical comprehensive treatment method for improving low-temperature fluidity of crude oil

Abstract

The application discloses a multi-chemical agent comprehensive treatment method for improving low-temperature fluidity of crude oil. The method comprises the following steps: S1, heating crude oil to a first predetermined temperature above a wax melting point and keeping the temperature for a first predetermined time, then adding a pour point depressant to perform first stirring treatment at the first predetermined temperature; S2, after the first stirring is completed, cooling the crude oil to a second predetermined temperature between a wax precipitation point and a freezing point of the crude oil and keeping the temperature for a second predetermined time, then adding a heavy oil viscosity reducer to perform second stirring treatment at the second predetermined temperature, and completing the multi-chemical agent comprehensive treatment. The method utilizes multi-chemical agent comprehensive treatment, can further improve the low-temperature fluidity of the crude oil, and is expected to bring a new solution to solve problems in the process of crude oil pipeline transportation and storage.

Description

Technical Field

[0001] This invention relates to a method for significantly improving crude oil fluidity by using a combination of multiple chemical agents, belonging to the field of crude oil viscosity reduction technology. Background Technology

[0002] Petroleum plays an indispensable role in my country's national economic development and is one of the most important resources in the international community today. With the continuous growth of the national economy, my country's demand for petroleum is also constantly expanding. Most of the crude oil produced in my country is high-viscosity and has poor fluidity, such as waxy crude oil.

[0003] Waxy crude oil exhibits complex rheological properties. Its wax gradually precipitates at lower temperatures, forming a sponge-like network structure, resulting in poor fluidity and posing challenges to pipeline transportation and storage. Currently, the mainstream method for modifying waxy crude oil is the use of pour point depressants. This technology has been widely applied in the pipeline transportation of waxy crude oil, achieving good economic benefits in numerous long-distance crude oil pipelines both domestically and internationally. However, this technology is not very effective in some crude oils with high wax content (e.g., wax content greater than 15 wt%).

[0004] The effect of pour point depressants on modifying waxy crude oil has certain limitations. Therefore, how to improve the fluidity of crude oil at low temperatures remains a pressing technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil. This method utilizes a variety of chemical agents to further improve the fluidity of crude oil at low temperatures, and is expected to bring new solutions to problems in crude oil pipeline transportation and storage.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil, comprising the following steps:

[0008] S1. Heat the crude oil to a first predetermined temperature above the melting point of wax and keep it at that temperature for a first predetermined time. Then add the pour point depressant and perform the first stirring treatment at the first predetermined temperature.

[0009] S2. After the first stirring is completed, the crude oil is cooled to a second predetermined temperature between the crude oil wax precipitation point and the pour point and kept at the temperature for a second predetermined time. Then, a heavy oil viscosity reducer is added and a second stirring treatment is carried out at the second predetermined temperature to complete the multi-chemical agent comprehensive treatment.

[0010] In the above-mentioned multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil, the crude oil is waxy crude oil or mixed waxy crude oil.

[0011] Furthermore, the wax content of the crude oil is 10-25 wt% (e.g., 18.35 wt%, 21.1 wt%, 11.46 wt%), and preferably the total content of gums and asphaltenes is 5-18 wt% (e.g., 17 wt%, 9 wt%, 7.5 wt%). If the total content of gums and asphaltenes exceeds this range, the effect of the heavy oil viscosity reducer will be relatively poor.

[0012] Furthermore, the water content of the crude oil does not exceed 1%, such as 1%.

[0013] In the above-mentioned multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil, the first predetermined temperature is 3 to 15°C above the wax melting point of crude oil, such as 4.1°C, 7°C or 4.1°C above the wax melting point of crude oil; if the first predetermined temperature is below this range, the crude oil may contain wax, which will affect the effect of the pour point depressant; if it is above this range, the temperature is too high and there is a safety risk.

[0014] The first predetermined time shall not be less than 30 minutes, such as 30 minutes.

[0015] In the above-mentioned comprehensive treatment method for improving the low-temperature fluidity of crude oil using multiple chemical agents, the pour point depressant includes one or more of ethylene-vinyl acetate copolymer (EVA), polyacrylate copolymer, maleic anhydride copolymer, nitrogen-containing polymer, and nano-pour point depressant and micron-pour point depressant; as an example, the pour point depressant is ethylene-vinyl acetate copolymer (EVA) with a VA content of 28% and a melt index of 25 g / 10 min.

[0016] The amount of pour point depressant added is 30-200 ppm, preferably 50-100 ppm, such as 50 ppm or 100 ppm; if the amount of pour point depressant added is lower than this range, the pour point depressant cannot play its due role, and if it is higher than this range, the economy is poor.

[0017] The stirring rate for the first stirring process is 50–300 rpm, preferably 80–100 rpm, such as 80 rpm;

[0018] The first stirring process takes 10 to 30 minutes, such as 10 minutes or 20 minutes.

[0019] In the above-mentioned multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil, the cooling rate in the cooling step is 0.2 to 2℃ / min, preferably 0.5℃ / min;

[0020] The second predetermined temperature is 10-12°C above the pour point of crude oil, such as 12°C, 10°C or 11°C above the pour point of crude oil; if the second predetermined temperature exceeds this range, the modification effect of the heavy oil viscosity reducer will be poor; the second predetermined temperature can be 45°C, 40°C or 25°C.

[0021] The second predetermined time is 10 to 30 minutes, such as 10 minutes or 20 minutes.

[0022] In the above-mentioned comprehensive treatment method for improving the low-temperature fluidity of crude oil using multiple chemical agents, the heavy oil viscosity reducer includes one or more of the following: hydroxyl derivative dispersants, polyacrylates, polyurethanes, triethylhexylphosphate, sodium dodecyl sulfate, dodecylbenzene sulfonic acid, methylpentanol, and cellulose derivatives, specifically dodecylbenzene sulfonic acid (DBSA).

[0023] The amount of the heavy oil viscosity reducer added is 30-200 ppm, preferably 50-100 ppm, such as 50 ppm or 100 ppm;

[0024] The second stirring process is carried out at a rate of 50–300 rpm, preferably 80–100 rpm, such as 80 rpm.

[0025] The second stirring process takes 10 to 30 minutes, such as 10 minutes or 20 minutes.

[0026] In this invention, an addition amount of 1 ppm means that the mass of solute contained in one million parts of solution is 1 unit mass.

[0027] In the above-mentioned multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil, the first stirring treatment and the second stirring treatment are carried out in a stirred tank.

[0028] In the above-mentioned multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil, the improvement of the low-temperature fluidity of crude oil is manifested in reducing the viscosity of crude oil and / or reducing the pour point of crude oil.

[0029] The present invention has the following beneficial effects:

[0030] Traditional methods of modifying crude oil with a single pour point depressant are ineffective in reducing pour point and viscosity of high-wax crude oil (wax content greater than 15 wt%). However, this invention is applicable to crude oils with a wax content range of 10–25 wt%, offering a wider range of applicability compared to traditional pour point depressant methods. This invention utilizes a combination of chemical agents to further improve the fluidity of crude oil at low temperatures, specifically by reducing crude oil viscosity and pour point, potentially providing a new solution to problems encountered in crude oil pipeline transportation and storage. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the process flow of the multi-chemical agent integrated treatment method provided by the present invention. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0033] Unless otherwise specified, the methods used in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0034] The pour point depressant used in the following examples was ethylene-vinyl acetate copolymer (EVA-2825), purchased from DuPont, USA. The VA content was 28%, and the melt flow index was 25 g / 10 min.

[0035] The viscosity reducers for heavy oil are all dodecylbenzenesulfonic acid (DBSA).

[0036] Example 1

[0037] The selected oil sample is a typical waxy crude oil #1, and its basic physical properties and testing methods are shown in Table 1.

[0038] Table 1. Basic physical properties and testing methods of waxy crude oil #1

[0039]

[0040]

[0041] (1) Combined treatment of waxy crude oil with pour point depressant and heavy oil viscosity reducer.

[0042] according to Figure 1 The flowchart shown illustrates the comprehensive multi-chemical treatment of waxy crude oil #1 to improve its low-temperature fluidity. The specific steps are as follows:

[0043] Waxy crude oil #1 was heated to 80℃ (above its melting point) and held at that temperature for 30 minutes. Then, 100 ppm of pour point depressant was added, and the mixture was placed in a stirred tank and stirred at 80 rpm for 10 minutes at 80℃. Next, the temperature was lowered to 45℃ (12℃ above its pour point) at a rate of 0.5℃ / min and held at 45℃ for 10 minutes. Then, 100 ppm of heavy oil viscosity reducer was added, and the mixture was stirred at 80 rpm for 10 minutes at 45℃. This process was used to prepare waxy crude oil treated with both pour point depressant and heavy oil viscosity reducer.

[0044] (2) Modification of waxy crude oil with a single chemical agent

[0045] To demonstrate the further modification effect of multi-chemical agent treatment on waxy crude oil #1, it is necessary to prepare waxy crude oil #1 modified by a single chemical agent. The specific steps are as follows:

[0046] Waxy crude oil #1 was heated to 80℃ (above its melting point) and held at that temperature for 30 minutes. Then, 200 ppm of pour point depressant / heavy oil viscosity reducer was added, and the mixture was placed in a stirred tank and stirred at 80 rpm for 10 minutes at 80℃. The waxy crude oil modified with a single chemical agent was prepared using the above process.

[0047] (3) Viscosity test

[0048] The viscosity of additive-treated oil (waxy crude oil treated with a combination of pour point depressant and heavy oil viscosity reducer, waxy crude oil modified with pour point depressant, and waxy crude oil treated with heavy oil viscosity reducer) and blank crude oil were tested. The specific steps are as follows:

[0049] The additive oil / blank crude oil was heated to 80℃ and held at that temperature for 30 min, then cooled to 35℃ (2℃ above the pour point) at a rate of 0.5℃ / min. After holding at 35℃ for 20 min, the additive oil / blank crude oil was tested at a shear rate of 10 s⁻¹. -1 The viscosity at that point is shown in Table 2.

[0050] Table 2. Effects of multi-chemical agent comprehensive modification on the viscosity of waxy crude oil #1

[0051]

[0052] The formula for calculating the viscosity reduction rate is: 10 seconds before the additive treatment. -1 The equilibrium viscosity is η0, and the viscosity is 10s after the addition treatment. -1 The equilibrium viscosity is η T The viscosity reduction rate is:

[0053] Δη=(η0-η T ) / η0×100%

[0054] As can be seen from Table 2, the viscosity of crude oil treated with multiple chemical agents is lower than that of crude oil treated with only a single chemical agent.

[0055] Comparative Example 1

[0056] The selected oil sample was a typical waxy crude oil #1 (same as in Example 1). To demonstrate the modification effect of the additive method shown in this invention, the waxy crude oil #1 was treated with additives using a conventional additive method. The specific steps are as follows:

[0057] Waxy crude oil #1 was heated to 80℃ (above its melting point) and held at that temperature for 30 minutes. Then, 100 ppm of pour point depressant and 100 ppm of heavy oil viscosity reducer were added, and the mixture was placed in a stirred tank and stirred at 80 rpm for 10 minutes at 80℃. The waxy crude oil treated with the combined pour point depressant and heavy oil viscosity reducer was prepared using the above process.

[0058] Next, prepare an oil sample containing only pour point depressant / heavy oil viscosity reducer according to the following preparation process: heat the waxy crude oil #1 to 80℃ (above the wax melting point temperature) and keep it at that temperature for 30 minutes. Then add 200 ppm of pour point depressant / heavy oil viscosity reducer and place it in a mixing tank. Stir at 80℃ and 80 rpm for 10 minutes.

[0059] The viscosity of the additive oil and blank crude oil was tested using the following steps: The additive oil / blank crude oil was heated to 80℃ and held at that temperature for 30 minutes. Then, it was cooled to 35℃ (2℃ above the pour point) at a rate of 0.5℃ / min. After holding at 35℃ for 20 minutes, the viscosity of the additive oil / blank crude oil at a shear rate of 10s⁻¹ was tested. -1 The viscosity at that point (calculated using the same formula as in Example 1) is shown in Table 3.

[0060] Table 3. Effects of multi-chemical agent comprehensive modification on the viscosity of waxy crude oil #1

[0061]

[0062] As can be clearly seen from Table 3, if the waxy crude oil #1 is not treated with additives according to the additive process shown in this invention, the viscosity of the crude oil after comprehensive treatment with multiple chemical agents may even increase.

[0063] Example 2

[0064] The selected oil sample was a typical waxy crude oil #2, and its basic properties and testing methods are shown in Table 4.

[0065] Table 4. Basic physical properties and testing methods of waxy crude oil #2

[0066]

[0067] (1) Combined treatment of waxy crude oil with pour point depressant and heavy oil viscosity reducer.

[0068] according to Figure 1 The flowchart shown illustrates the comprehensive multi-chemical treatment of waxy crude oil #2 to improve its low-temperature fluidity. The specific steps are as follows:

[0069] Waxy crude oil #2 was heated to 70℃ (above its melting point) and held at that temperature for 30 minutes. Then, 50 ppm of a pour point depressant was added, and the mixture was placed in a stirred tank and stirred at 70℃ and 80 rpm for 20 minutes. Next, the temperature was lowered to 40℃ (10℃ above the pour point) at a rate of 0.5℃ / min and held at 40℃ for 20 minutes. Then, 50 ppm of a heavy oil viscosity reducer was added, and the mixture was stirred at 40℃ and 80 rpm for 20 minutes. This process was used to prepare waxy crude oil treated with both a pour point depressant and a heavy oil viscosity reducer.

[0070] (2) Modification of waxy crude oil with a single chemical agent

[0071] To demonstrate the further modification effect of multi-chemical agent treatment on waxy crude oil #2, waxy crude oil #2 modified with a single chemical agent needs to be prepared. The preparation process is as follows: heat waxy crude oil #2 to 70℃ (above the wax melting point temperature) and maintain the temperature for 30 minutes, then add 100 ppm pour point depressant / heavy oil viscosity reducer, and then place it in a stirred tank and stir at 70℃ and 80 rpm for 20 minutes.

[0072] (3) Freezing point test

[0073] The specific steps for testing the pour points of the additive-treated oil and the blank crude oil are as follows:

[0074] The additive oil / blank crude oil was heated to 70℃ and held at that temperature for 30 min. Then, it was cooled to 8℃ above the expected pour point at a rate of 0.5℃ / min. The fluidity of the additive oil / blank crude oil was observed every 2℃. The highest temperature at which the oil sample did not flow after being placed horizontally for 5 seconds was taken as the pour point. The experimental results are shown in Table 5.

[0075] Table 5. Effects of multi-chemical agent comprehensive modification on the pour point of waxy crude oil #2

[0076]

[0077] As can be seen from Table 5, the pour point of crude oil treated with multiple chemical agents is lower than that of crude oil treated with only a single chemical agent.

[0078] Example 3

[0079] The selected oil sample was a typical mixed waxy crude oil #3, and its basic physical properties and testing methods are shown in Table 6.

[0080] Table 6. Basic physical properties and testing methods of waxy crude oil #3

[0081]

[0082]

[0083] (1) Combined treatment of mixed waxy crude oil with pour point depressant and heavy oil viscosity reducer.

[0084] according to Figure 1 The flowchart shown illustrates the comprehensive multi-chemical treatment of mixed waxy crude oil #3 to improve its low-temperature fluidity. The specific steps are as follows:

[0085] The mixed waxy crude oil #3 was heated to 50°C (above the melting point of wax) and held at that temperature for 30 minutes. Then, 100 ppm of pour point depressant was added, and the mixture was placed in a stirred tank and stirred at 80 rpm for 10 minutes at 50°C. The temperature was then lowered to 25°C (11°C above the pour point) at a rate of 0.5°C / min and held at 25°C for 10 minutes. Then, 100 ppm of heavy oil viscosity reducer was added, and the mixture was stirred at 80 rpm for 10 minutes at 25°C. This process was used to prepare the waxy crude oil treated with a combination of pour point depressant and heavy oil viscosity reducer.

[0086] (2) Modification of mixed waxy crude oil with a single chemical agent

[0087] To demonstrate the further modification effect of multi-chemical agent comprehensive treatment on mixed waxy crude oil #3, it is necessary to prepare mixed waxy crude oil #3 modified by a single chemical agent. The specific steps are as follows:

[0088] The mixed waxy crude oil #3 was heated to 50°C (above the melting point of wax) and held at that temperature for 30 minutes. Then, 200 ppm of pour point depressant / heavy oil viscosity reducer was added, and the mixture was placed in a stirred tank and stirred at 80 rpm for 10 minutes at 50°C. The waxy crude oil modified with a single chemical agent was prepared using the above process.

[0089] (3) Viscosity test

[0090] The viscosity of additive-treated oil (mixed waxy crude oil treated with a combination of pour point depressant and heavy oil viscosity reducer, mixed waxy crude oil modified with pour point depressant, and mixed waxy crude oil treated with heavy oil viscosity reducer) and blank crude oil were tested. The specific steps are as follows:

[0091] The additive oil / blank crude oil was heated to 50°C and held at that temperature for 30 min. Then, it was cooled to 16°C (2°C above the pour point) at a rate of 0.5°C / min. After holding at 16°C for 20 min, the additive oil / blank crude oil was tested at a shear rate of 10 s⁻¹. -1 The viscosity at that point is shown in Table 7.

[0092] Table 7. Effects of multi-chemical agent comprehensive modification on the viscosity of mixed waxy crude oil #3

[0093]

[0094] As can be seen from Table 7, the viscosity of crude oil treated with multiple chemical agents is lower than that of crude oil treated with only a single chemical agent.

[0095] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including modifications made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil, comprising the following steps: S1. Heat the crude oil to a first predetermined temperature above the melting point of wax and keep it at that temperature for a first predetermined time. Then add the pour point depressant and perform the first stirring treatment at the first predetermined temperature. The first predetermined temperature is 3-15°C above the melting point of crude oil; The first scheduled time shall not be less than 30 minutes; The pour point depressant includes one or more of the following: ethylene-vinyl acetate copolymer, polyacrylate copolymer, maleic anhydride copolymer, nitrogen-containing polymer, nano pour point depressant, and micron pour point depressant. The amount of pour point depressant added is 30~200ppm; The stirring rate for the first stirring process is 50~300 rpm; The first stirring process takes 10-30 minutes. S2. After the first stirring is completed, the crude oil is cooled to a second predetermined temperature between the crude oil wax precipitation point and the pour point and kept at the temperature for a second predetermined time. Then, a heavy oil viscosity reducer is added and a second stirring treatment is carried out at the second predetermined temperature to complete the multi-chemical agent comprehensive treatment. The cooling rate in the cooling step is 0.2~2°C / min; The second predetermined temperature is 10-12°C above the crude oil pour point temperature; The second predetermined time is 10~30 minutes; The heavy oil viscosity reducer includes one or more of the following: hydroxyl derivative dispersants, polyacrylates, polyurethanes, triethylhexylphosphate, sodium dodecyl sulfate, dodecylbenzene sulfonic acid, methylpentanol, and cellulose derivatives. The amount of the heavy oil viscosity reducer added is 30~200ppm; The second stirring process is carried out at a rate of 50-300 rpm; The second stirring process takes 10 to 30 minutes.

2. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to claim 1, characterized in that: The crude oil is waxy crude oil or a mixture of waxy crude oil.

3. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to claim 2, characterized in that: The wax content of the crude oil is 10-25 wt%.

4. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to claim 3, characterized in that: The total content of gums and asphaltenes in the crude oil is 5-18 wt%.

5. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to claim 2, characterized in that: The water content of the crude oil is no more than 1%.

6. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to any one of claims 1-5, characterized in that: The amount of the pour point depressant added is 50~100ppm; The stirring rate for the first stirring process is 80-100 rpm.

7. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to any one of claims 1-5, characterized in that: The cooling rate in the cooling step is 0.5°C / min.

8. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to any one of claims 1-5, characterized in that: The amount of the heavy oil viscosity reducer added is 50~100ppm; The second stirring process is carried out at a rate of 80-100 rpm.

9. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to any one of claims 1-5, characterized in that: The first and second stirring processes are carried out in a stirred tank.

10. The multi-chemical agent integrated treatment method for improving the low-temperature fluidity of crude oil according to any one of claims 1-5, characterized in that: The improvement in the low-temperature fluidity of crude oil is manifested in reducing crude oil viscosity and / or reducing crude oil pour point.

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