Preparation method of reverse wetting agent for oil field

Abstract

The invention discloses a preparation method of a reverse wetting agent for an oil field, and relates to the technical field of oil field chemistry, and the reverse wetting agent for the oil field is prepared from the following materials in parts: 180-270 parts of mahogany petroleum sulfonate, 30-45 parts of fatty alcohol-polyoxyethylene ether, 200-300 parts of sodium dodecyl benzene sulfonate, 300-450 parts of polyacrylamide, 290-435 parts of methanol and 120-130 parts of sodium hydroxide. According to the preparation method of the reverse wetting agent for the oil field, the product can effectively solve the problems that in fracturing development of a low-permeability oil and gas field, surfactant molecules are adsorbed to hydrophilic rocks, the wettability of the rocks is changed into hydrophobicity, and the recovery efficiency is reduced, and the reverse wetting agent for the oil field is prepared through the specific preparation technology and the raw material ratio. According to the present invention, the reverse of the formation wettability can be achieved, the adhesion work of the crude oil in the oleophylic rock core can be reduced, and the hydrophobic rock can be changed into the hydrophilic rock, such that the petroleum recovery rate can be improved, the exploitation requirements of different oil fields can be met, and the important significance can be provided for the improvement of the exploitation efficiency of the low-permeability oil-gas field.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, and specifically relates to a preparation method of a wetting reversal agent for oilfields. Background Art

[0002] With the in-depth development of low-permeability oil and gas fields, the performance requirements for fracturing fluids have become increasingly strict, aiming to overcome problems such as difficult gel breaking, high filtration loss, and a large amount of residue existing in traditional fracturing fluids. In recent years, due to many advantages of clean fracturing fluids, such as good filtration loss control, effective fracture height control, low construction friction, high fracturing fluid efficiency, and little damage to reservoirs, etc., they have gradually become a research and application hotspot. Especially in natural gas wells, clean fracturing fluids have shown significant production-increasing effects.

[0003] The main components of clean fracturing fluids include viscoelastic surfactants, salt solutions, and stabilizers. Currently, the carbon chain lengths of surfactants in research and application mostly range from 12 to 18, and they are mainly divided into anionic and cationic types. Cationic surfactants occupy a dominant position in research and field applications due to their good gelling performance, temperature resistance performance, and mature synthesis process. However, with the in-depth research, scientists have found that cationic surfactants have strong adsorption on formation clays and sandstones, which may lead to formation wetting reversal, thereby increasing the damage to reservoirs and affecting the final recovery rate. The wetting reversal phenomenon is crucial for oilfield development. The research by Wang Zhenyu et al. shows that the adhesion work of crude oil in hydrophilic cores is much smaller than that in oleophilic cores, and the former is only 1 / 6.8 of the latter. This means that in oil wells, when the sandstone surface shows hydrophilicity, the oil recovery rate will be significantly improved. In view of this, we propose a preparation method of a wetting reversal agent for oilfields. Summary of the Invention

[0004] To solve the above technical problems, a preparation method of a wetting reversal agent for oilfields is provided, and this technical solution solves the above problems.

[0005] To achieve the above purposes, the technical solution adopted by the present invention is as follows: A preparation method of a wetting reversal agent for oilfields, the wetting reversal agent for oilfields is prepared from the following parts by weight of materials: 180 - 270 parts of petroleum sulfonate, 30 - 45 parts of fatty alcohol polyoxyethylene ether, 200 - 300 parts of sodium dodecylbenzenesulfonate, 300 - 450 parts of polyacrylamide, 290 - 435 parts of methanol, and 120 - 130 parts of sodium hydroxide.

[0006] Preferably, the wetting reversal agent for oilfields is specifically prepared from the following parts by weight of materials: 216 parts of petroleum sulfonate, 36 parts of fatty alcohol polyoxyethylene ether, 240 parts of sodium dodecylbenzenesulfonate, 360 parts of polyacrylamide, 348 parts of methanol, and 115 parts of sodium hydroxide.

[0007] Preferably, the preparation method is as follows: S1. Prepare materials: 216 parts of petroleum sulfonate, 36 parts of fatty alcohol polyoxyethylene ether, 240 parts of sodium dodecylbenzenesulfonate, 360 parts of polyacrylamide, 348 parts of methanol, and 115 parts of sodium hydroxide; S2. Put the petroleum sulfonate, fatty alcohol polyoxyethylene ether, and sodium dodecylbenzenesulfonate into a reaction kettle, add methanol, and stir at a stirring speed of 200 - 500 r / min for 30 - 60 min until completely dissolved to obtain Solution 1; S3. Slowly add polyacrylamide to Solution 1 while stirring, adjust the stirring speed to 100 - 200 r / min, and stir for 60 - 120 min. The particle size of the polyacrylamide is 70 - 150 nm to obtain Solution 2; S4. Use a pH meter to measure, dropwise add sodium hydroxide solution to Solution 2 while stirring and observing the pH meter reading, and adjust the pH value of Solution 2 to between 6 and 8; S5. Filter the prepared wetting reversal agent solution through a filter to remove impurities and insoluble substances therein; S6. Conduct quality inspection on the prepared wetting reversal agent. The quality inspection includes: appearance, surface tension, and wettability; S7. Package the wetting reversal agent that passes the inspection and store it in a dry, cool, and ventilated environment.

[0008] Preferably, the preparation process of the petroleum sulfonate is as follows: React the petroleum fraction with concentrated sulfuric acid at 40 - 60 for 2 - 4 h, where the mass ratio of the petroleum fraction to concentrated sulfuric acid is 3:1 - 5:1; After the reaction, pour the mixture into cold water, stir for 30 - 60 min, and let it stand for layering for 2 - 3 h; Take the upper oil phase and neutralize it to a pH value of 7 - 9 with a sodium hydroxide solution with a mass fraction of 5% - 10%; After vacuum distillation, distill out excess water and low - boiling impurities at 120 - 150 and a vacuum degree of 0.08 - 0.1 MPa to obtain petroleum sulfonate.

[0009] Preferably, the active ingredient content of the petroleum sulfonate shall not be less than 85%, and its production process shall follow the sulfonation reaction specification, controlling the reaction temperature in the range of 40 - 60 and the reaction time of 3 - 5 h; The ethylene oxide addition number of the fatty alcohol polyoxyethylene ether needs to be controlled between 5 and 10; The purity of the sodium dodecylbenzenesulfonate is required to be greater than or equal to 90%.

[0010] Preferably, during the stirring and dissolving process in step S2, the reactor should be made of stainless steel and have a jacket temperature control function; The initial stirring temperature is set to 30 When the dissolution process is halfway through, / min rate rises to 40 , continue stirring until completely dissolved; The stirring blade adopts a double-layer turbine design. The ratio of the upper blade diameter to the inner diameter of the reactor is 0.4-0.5, and the lower blade is 0.3-0.4. The rotation speed is dynamically adjusted between 200-500r / min according to the dissolution conditions.

[0011] Preferably, in step S3, when the amount of polyacrylamide added is 0-100 parts, the addition rate is 1-2 parts / minute; In the range of 101-200 copies, the rate is adjusted to 0.8-1.5 copies / minute; When the number of copies is 201-300, it is reduced to 0.5-1 copy / minute; When the amount exceeds 300, maintain 0.3-0.8 portion / min until all the portions are added; During this process, the angle of the stirring blade changes with the amount of polyacrylamide added. Initially, the angle between the upper blade and the horizontal is 30°-40°, and the angle between the lower blade and the horizontal is 20°-30°. The angle is adjusted every time 100 portions are added, and finally the upper blade reaches 45°-55° and the lower blade reaches 35°-45°. To prevent agglomeration, sodium hexametaphosphate, a dispersant, was pre-added to solution 1 in an amount of 0.5%-1% of the mass of polyacrylamide; During the whole process of adding polyacrylamide, the jacket of the reactor was circulated with water to control the temperature. , every 30 minutes up to 2 -3 Up to 35 -40 , stabilize the stretching of polymer molecular chains and interact with solvent molecules to form a uniform and stable system, thereby improving the quality stability and performance consistency of solution 2.

[0012] Preferably, in step S4, a pH meter with an accuracy of 0.01 is used for real-time monitoring, the tip of the dropper for dripping the sodium hydroxide solution has an inner diameter of 0.5-1 mm and a length of 5-10 cm, and the dripping speed is dynamically adjusted according to the pH change; When the pH value is lower than 6 and the difference from 6 is ΔpH>0.5, the dripping rate is 10-15 drops / minute; When ΔpH is between 0.2-0.5, it drops to 5-8 drops / minute; When pH reaches 6 and ΔpH < 0.2, reduce to 2-4 drops / minute for fine-tuning; When the pH is above 6 and below 7, the dropping speed is adjusted reversely according to a similar rule based on the difference from 7. When the pH is above 7 and below 8, for every 0.1 increase, the speed is decreased by 1 - 2 drops / minute. The stirring speed changes according to the pH trend. When the pH increases, it is 120 - 150 r / min, and when approaching the target value, it is decreased to 80 - 100 r / min to prevent local alkali overdose.

[0013] Preferably, the refinement requirements for the filtration operation in step S5 are as follows: The filter adopts a multi - layer composite structure, which is, from the inside to the outside, a 5 - 10 μm stainless - steel filter mesh, a 3 - 5 mm thick diatomite filter layer, and an 8 - 12 μm polyethersulfone filter membrane. Before filtration, first rinse the filter 3 - 5 times with deionized water pre - heated to 40 - 45 to remove impurities and pollutants. During filtration, the pressure difference is controlled at 0.2 - 0.4 MPa, and adjusted according to the turbidity and flow rate of the solution. When the solution has high turbidity and large flow rate, the pressure difference is set at 0.3 - 0.4 MPa. When it gradually becomes clear and the flow rate decreases, it is decreased by 0.02 - 0.05 MPa every 10 minutes until it reaches 0.2 MPa to maintain stable filtration. The filtrate is collected in a light - shielding, nitrogen - filled storage tank with a temperature control of 20 - 25 to prevent oxidation degradation and microbial growth. The filter layer is replaced regularly. The stainless - steel filter mesh is replaced every 10 - 15 batches, the diatomite layer is replaced every 5 - 8 batches, and the polyethersulfone filter membrane is replaced every 8 - 10 batches, determined according to the filtration resistance and filtrate quality monitoring.

[0014] Preferably, in step S6, the appearance inspection is carried out in an observation room with a white background and an illuminance of 500 - 800 lx. The solution should be clear, transparent, without precipitation and flocculation, and its color is white to light yellow. The surface tension is detected by combining the pendant - drop method and the Wilhelmy - plate method. The pendant - drop method measures the static tension, and the plate method measures the dynamic tension. At 25 the qualified static value is 28 - 32 mN / m and the dynamic value is 30 - 34 mN / m. The wettability is detected by the contact - angle measurement method. A quartz glass slide is used to simulate the reservoir rock, the droplet volume is 5 - 8 μL, and the average value is taken from 5 measurements. For the water contact angle, before inversion, it is 100° - 120°, and after inversion, it is ≤60° to meet the standard; for the oil contact angle, before inversion, it is 20° - 30°, and after inversion, it is ≥80° to be qualified.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The preparation method of the wettability reversal agent for oil fields proposed by the present invention can effectively solve the problem that in the fracturing development of low-permeability oil and gas fields, surfactant molecules adsorb onto hydrophilic rocks, change the wettability of the rocks to hydrophobic, and reduce the recovery rate. Through specific preparation processes and raw material ratios, this wettability reversal agent can achieve the reversal of formation wettability, reduce the adhesion work of crude oil in oil-wet cores, and thus improve the oil recovery rate. Through precise raw material ratios and preparation steps, high-quality wettability reversal agents can be stably prepared. The raw materials used in the preparation process are widely sourced and relatively low in cost, which is beneficial to reducing production costs. The prepared wettability reversal agent has good stability and performance consistency, can meet the exploitation requirements of different oil fields, and is of great significance for improving the exploitation efficiency and economic benefits of low-permeability oil and gas fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of the preparation method of the wettability reversal agent for oil fields. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are only examples, and those skilled in the art can think of other obvious variations.

[0018] A preparation method of a wettability reversal agent for oil fields, the wettability reversal agent for oil fields is prepared from the following parts by weight of materials: 180 - 270 parts of petroleum sulfonate, 30 - 45 parts of fatty alcohol polyoxyethylene ether, 200 - 300 parts of sodium dodecylbenzenesulfonate, 300 - 450 parts of polyacrylamide, 290 - 435 parts of methanol, and 120 - 130 parts of sodium hydroxide.

[0019] The wettability reversal agent for oil fields is specifically prepared from the following parts by weight of materials: 216 parts of petroleum sulfonate, 36 parts of fatty alcohol polyoxyethylene ether, 240 parts of sodium dodecylbenzenesulfonate, 360 parts of polyacrylamide, 348 parts of methanol, and 115 parts of sodium hydroxide.

[0020] Refer to Figure 1 As shown, the preparation method of the wettability reversal agent for oil fields is as follows: Prepare the materials. 216 parts of petroleum sulfonate are required, which plays a key role in the preparation of the wettability reversal agent. At the same time, prepare 36 parts of fatty alcohol polyoxyethylene ether, which can enhance the performance of the wettability reversal agent. In addition, there are 240 parts of sodium dodecylbenzenesulfonate, which has good surface activity, and 360 parts of polyacrylamide. Polyacrylamide can achieve better effects within a specific particle size range. Additionally, prepare 348 parts of methanol, which can fully dissolve various components as a solvent. Finally, prepare 115 parts of sodium hydroxide for adjusting the pH value of the solution.

[0021] Put petroleum sulfonate, fatty alcohol polyoxyethylene ether, and sodium dodecylbenzenesulfonate into a reaction kettle, then add methanol, turn on the stirring device, control the stirring speed within the range of 200 to 500 revolutions per minute, and continuously stir for 30 to 60 minutes to ensure that these components are completely dissolved, thus obtaining Solution 1.

[0022] Slowly add polyacrylamide to Solution 1, and stir while adding. At this time, adjust the stirring speed to 100 to 200 revolutions per minute, and set the stirring time to 60 to 120 minutes. It should be noted that the particle size of the polyacrylamide used here is 70 to 150 nanometers, and such a particle size range can ensure that polyacrylamide plays the best role in the wetting reversal agent.

[0023] Use a pH meter to measure, and slowly add sodium hydroxide solution drop by drop to Solution 2 while stirring, and always observe the reading of the pH meter. In this way, adjust the pH value of Solution 2 to between 6 and 8. This pH range can ensure that the wetting reversal agent has good stability and performance.

[0024] Filter the prepared wetting reversal agent solution through a filter to remove impurities and insoluble substances, which can ensure the purity of the wetting reversal agent and improve its use effect.

[0025] Conduct quality inspection on the prepared wetting reversal agent. The quality inspection includes multiple aspects. First is the appearance inspection, observing the appearance characteristics such as the color and transparency of the wetting reversal agent. Second is the surface tension inspection, measuring the surface tension of the wetting reversal agent through professional instruments to determine its surface activity. Finally is the wettability inspection, evaluating the wetting performance of the wetting reversal agent on various substances in the oilfield.

[0026] Package the wetting reversal agent that has passed the inspection. Store it in a dry, cool, and ventilated environment to ensure that the quality and performance of the wetting reversal agent are not affected. In this way, the preparation process of the wetting reversal agent for oilfield use is completed.

[0027] The preparation process of petroleum sulfonate is as follows: Prepare petroleum fraction and concentrated sulfuric acid. React the petroleum fraction with concentrated sulfuric acid at a temperature of 40 to 60 degrees Celsius. This temperature range can ensure the smooth progress of the reaction and avoid side reactions caused by too high a temperature. The reaction time lasts for 2 to 4 hours. During this period, the petroleum fraction and concentrated sulfuric acid are in full contact and undergo a chemical reaction. Among them, the mass ratio of the petroleum fraction to concentrated sulfuric acid is controlled within the range of 3:1 to 5:1. This ratio is crucial for the reaction effect. If the ratio is inappropriate, it may affect the yield and quality of petroleum sulfonate.

[0028] After the reaction is completed, carefully pour the mixture into cold water. The process of pouring cold water should be carried out slowly to prevent violent reactions. Then, stir the mixture for 30 to 60 minutes. Stirring can make the mixture mix thoroughly and promote the separation of reaction products. Next, let the mixture stand for layering for 2 to 3 hours. During the standing process, due to density differences, the mixture will gradually layer, with the upper layer being the oil phase and the lower layer being the water phase and other impurities.

[0029] Take the upper oil phase for treatment. Neutralize the upper oil phase with a sodium hydroxide solution with a mass fraction of 5% to 10%. During the neutralization process, slowly add the sodium hydroxide solution and keep stirring. Through the neutralization reaction, neutralize the acidic substances in the oil phase to make its pH value reach the range of 7 to 9. This pH value range can ensure the stability and performance of petroleum sulfonate.

[0030] Carry out vacuum distillation on the neutralized oil phase. Distill at a temperature of 120 to 150 °C and a vacuum degree of 0.08 to 0.1 MPa. During this process, excess water and low-boiling impurities will be distilled out, while petroleum sulfonate will remain in the distillation flask. Through vacuum distillation, the purity of petroleum sulfonate can be improved, impurities can be removed, and it can meet the requirements of industrial applications.

[0031] After the above series of steps, high-quality petroleum sulfonate can be obtained.

[0032] For petroleum sulfonate, the content of its active ingredients has strict requirements and shall not be less than 85%. This standard of high active ingredient content ensures that petroleum sulfonate can exhibit good performance in subsequent applications. In terms of production process, the sulfonation reaction specifications should be strictly followed. The sulfonation reaction is a key chemical process, and the control of reaction conditions is crucial. Among them, the reaction temperature needs to be controlled within the range of 40 - 60 Within this temperature range, the reaction can proceed relatively stably, neither too slow due to too low temperature nor causing side reactions due to too high temperature, which affects the product quality. At the same time, the reaction time should be controlled within 3 - 5 hours. Such a reaction time can ensure that the reaction proceeds fully and the active ingredients of petroleum sulfonate can be fully generated.

[0033] For fatty alcohol polyoxyethylene ether, the ethylene oxide addition number needs to be strictly controlled between 5 and 10. The control of the ethylene oxide addition number has an important impact on the performance of fatty alcohol polyoxyethylene ether. Within this range, fatty alcohol polyoxyethylene ether can have a suitable balance of hydrophilicity and hydrophobicity, so as to play a good synergistic role when mixed with other components and improve the overall performance of the wetting reversal agent.

[0034] For sodium dodecylbenzenesulfonate, its purity is required to be greater than or equal to 90%. High-purity sodium dodecylbenzenesulfonate can ensure its stable surface-active effect in the wetting reverser. The guarantee of purity means that the content of impurities in it is low, reducing the adverse effects that may be brought by impurities, such as reducing the reaction efficiency and affecting the product stability. At the same time, high-purity sodium dodecylbenzenesulfonate can also improve the quality and performance of the wetting reverser, making it more reliable in oilfield applications.

[0035] During the stirring and dissolving process in step S2, the material selection and functional requirements of the reaction kettle are very strict. The reaction kettle needs to be made of stainless steel because stainless steel has good corrosion resistance and stability, can withstand the erosion of various chemical substances during the reaction process, and ensure the safety of the reaction. And the reaction kettle should have a jacket temperature control function, which is crucial for controlling the reaction temperature. At the beginning of stirring, the set temperature is 30 . This relatively low starting temperature helps the components start to mix under relatively mild conditions, laying the foundation for the subsequent dissolving process. When the dissolving process is half done, it is heated to 40 at a rate of 2 / minute. This slow heating method can avoid adverse effects on the reaction system caused by too rapid temperature changes and ensure the best dissolving effect at different stages. Keep stirring until completely dissolved to ensure that the components are fully mixed to form a uniform solution. The stirring paddle is designed with a double-layer turbine type, which can provide a strong stirring force to make the components in the solution fully contact. The ratio of the diameter of the upper paddle to the inner diameter of the reaction kettle is 0.4 - 0.5, and the lower layer is 0.3 - 0.4. Such a ratio design can ensure that the solution at different levels can be fully stirred during the stirring process, improving the dissolving efficiency. The rotation speed is dynamically adjusted between 200 - 500 r / min according to the dissolving situation. Adjusting the stirring speed in real time according to the actual dissolving situation can better adapt to the reaction requirements at different stages and ensure the smooth progress of the dissolving process.

[0036] In step S3, there are detailed requirements for the addition of polyacrylamide. When the addition amount of polyacrylamide is between 0 and 100 parts, the addition rate is 1 - 2 parts / minute. At this stage, a slower addition rate can enable polyacrylamide to fully contact with other components in solution 1, avoiding excessive local concentration caused by too fast addition and affecting the dissolution effect. In the range of 101 - 200 parts, the rate is adjusted to 0.8 - 1.5 parts / minute. As the addition amount increases, appropriately reducing the addition rate can better control the stability of the reaction system. When it reaches 201 - 300 parts, it drops to 0.5 - 1 part / minute. When it exceeds 300 parts until all is added, it is maintained at 0.3 - 0.8 parts / minute. This way of gradually reducing the addition rate can ensure that the reaction system remains in a relatively stable state throughout the addition process. During this process, the angle of the stirring paddle changes with the addition amount of polyacrylamide, which is to better adapt to the stirring requirements under different addition amounts. Initially, the upper paddle forms an angle of 30° - 40° with the horizontal, and the lower paddle forms an angle of 20° - 30° with the horizontal. It is adjusted once every 100 parts added, and finally the upper paddle reaches 45° - 55° and the lower paddle reaches 35° - 45°. By adjusting the angle of the stirring paddle, the intensity and direction of stirring can be changed, improving the stirring efficiency and ensuring the full dissolution of polyacrylamide. To prevent agglomeration, sodium hexametaphosphate as a dispersant is pre-added to solution 1, and the addition amount is 0.5% - 1% of the mass of polyacrylamide. The addition of the dispersant can effectively prevent the agglomeration of polyacrylamide particles and improve its dispersibility in the solution. And throughout the addition of polyacrylamide, the jacket of the reaction kettle is passed through circulating water for temperature control, starting at 25 , rising 2 -3 to 35 -40 . By controlling the temperature, the stretching of polymer molecular chains can be stabilized, promoting their interaction with solvent molecules to form a uniform and stable system, thereby enhancing the mass stability and performance consistency of solution 2.

[0037] In step S4, a pH meter with a precision of 0.01 is used for real-time monitoring. This high-precision pH meter can accurately measure the pH value of the solution, ensuring the accuracy of the adjustment process. The inner diameter of the dropper tip for adding sodium hydroxide solution is 0.5 - 1 mm, and the length is 5 - 10 cm. Such a design can better control the dropping speed, ensuring that the sodium hydroxide solution can be evenly added to the solution. The dropping speed is dynamically adjusted according to the pH change. When the pH value is lower than 6 and the difference ΔpH from 6 is > 0.5, the dropping speed is 10 - 15 drops per minute. At this stage, a larger dropping speed can quickly increase the pH value of the solution. When ΔpH is between 0.2 - 0.5, it is reduced to 5 - 8 drops per minute. As the pH value gradually approaches the target value, reducing the dropping speed can more finely adjust the pH value. When the pH reaches 6 and ΔpH < 0.2, it is reduced to 2 - 4 drops per minute for fine-tuning. When approaching the target value, using a slower dropping speed can avoid over-adjustment. When the pH exceeds 6 and is lower than 7, the dropping speed is adjusted in the reverse direction according to a similar rule based on the difference from 7. When it exceeds 7 and is lower than 8, it is reduced by 1 - 2 drops per minute for every 0.1 increase. At the same time, the stirring speed changes according to the pH trend. When the pH increases, the stirring speed is 120 - 150 r / min, and it is reduced to 80 - 100 r / min when approaching the target value to prevent local alkali overdose. Through this dynamic adjustment method, the pH value of the solution can be more accurately controlled, ensuring the stability of the reaction system.

[0038] In the filtration operation of step S5, there are strict refinement requirements. The filter adopts a multi-layer composite structure, which is successively a 5 - 10 μm stainless steel filter screen, a 3 - 5 mm thick diatomite filter layer, and an 8 - 12 μm polyethersulfone filter membrane from the inside to the outside. This multi-layer composite structure can effectively remove impurities and insoluble substances in the solution, improving the purity of the filtrate. Before filtration, first rinse the filter 3 - 5 times with deionized water preheated to 40 -45 and having the same volume as the wetting inversion agent solution to remove impurities and contaminants. The preheated deionized water can better clean the filter, ensuring that no new impurities are introduced during the filtration process. During filtration, the pressure difference is controlled at 0.2 - 0.4 MPa and adjusted according to the solution turbidity and flow rate. In the stage where the solution turbidity is high and the flow rate is large, the pressure difference is set at 0.3 - 0.4 MPa to ensure that larger particles of impurities can be quickly filtered out. When the solution gradually becomes clear and the flow rate decreases, it is reduced by 0.02 - 0.05 MPa every 10 minutes until 0.2 MPa is maintained for stable filtration. This can avoid the filter membrane from rupturing or the filtration effect from decreasing due to excessive pressure in the later stage of filtration. The filtrate is collected in a light-shielded, nitrogen-filled container with a temperature control of 20 -25 Storage tank, preventing oxidative degradation and microbial growth. Light shielding can avoid the influence of light on the filtrate, nitrogen filling can prevent oxidation, and temperature control can ensure the stability of the filtrate. Replace the filter layer regularly. Replace the stainless steel filter screen every 10 - 15 batches, the diatomaceous earth layer every 5 - 8 batches, and the polyethersulfone filter membrane every 8 - 10 batches. Determine the replacement time based on the filtration resistance and filtrate quality monitoring. This can ensure that the filter always maintains a good filtration effect and guarantees the quality of the filtrate.

[0039] In step S6, the appearance inspection is carried out in an observation room with a white background and an illuminance of 500 - 800 lx. The solution should be clear, transparent, without precipitation and flocculation, and white to light yellow. Such inspection conditions can better observe the appearance of the solution and ensure that it meets the quality requirements. The surface tension is detected by combining the pendant drop method and the Wilhelmy plate method. The pendant drop method measures the static tension, and the plate method measures the dynamic tension. At 25 °C, the qualified static value is 28 - 32 mN / m, and the dynamic value is 30 - 34 mN / m. By combining the two methods, the surface tension characteristics of the solution can be more comprehensively understood. The wettability is detected by the contact angle measurement method. The quartz glass slide is used to simulate the reservoir rock, the droplet volume is 5 - 8 μL, and the average value is taken from 5 measurements. For the water contact angle, it meets the standard when it is 100° - 120° before inversion and ≤60° after inversion; for the oil contact angle, it is qualified when it is 20° - 30° before inversion and ≥80° after inversion. By measuring the contact angle, the wettability of the wettability reversal agent can be evaluated to ensure its effectiveness in oilfield applications.

[0040] The usage process of the present invention is as follows: Prepare the required materials and weigh them precisely, mix the main materials and methanol and stir to dissolve, slowly add polyacrylamide and stir, adjust the pH value of the solution to between 6 - 8, remove impurities and insoluble substances through a filter, conduct quality inspection on the wettability reversal agent, and package and store it in a dry, cool and well-ventilated environment.

[0041] In summary, the advantages of the present invention are as follows: The preparation process is simple and controllable, the raw materials used in the preparation process are widely sourced, and the prepared wettability reversal agent has good stability and performance consistency.

[0042] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a wettability reversal agent for oil fields, characterized in that, The wetting reversal agent for oil fields is prepared from the following parts by weight of materials: 180 - 270 parts of petroleum sulfonate, 30 - 45 parts of fatty alcohol polyoxyethylene ether, 200 - 300 parts of sodium dodecylbenzenesulfonate, 300 - 450 parts of polyacrylamide, 290 - 435 parts of methanol, and 120 - 130 parts of sodium hydroxide.

2. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that, Specifically, the wetting reversal agent for oil fields is prepared from the following parts by weight of materials: 216 parts of petroleum sulfonate, 36 parts of fatty alcohol polyoxyethylene ether, 240 parts of sodium dodecylbenzenesulfonate, 360 parts of polyacrylamide, 348 parts of methanol, and 115 parts of sodium hydroxide.

3. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that, The preparation method is as follows: S1. Prepare the materials: 216 parts of petroleum sulfonate, 36 parts of fatty alcohol polyoxyethylene ether, 240 parts of sodium dodecylbenzenesulfonate, 360 parts of polyacrylamide, 348 parts of methanol, and 115 parts of sodium hydroxide. S2. Put the petroleum sulfonate, fatty alcohol polyoxyethylene ether, and sodium dodecylbenzenesulfonate into a reaction kettle, add methanol, and stir at a speed of 200 - 500 r / min for 30 - 60 min until completely dissolved to obtain Solution 1. S3. Slowly add polyacrylamide to Solution 1 while stirring, adjust the stirring speed to 100 - 200 r / min, and stir for 60 - 120 min. The particle size of polyacrylamide is 70 - 150 nm to obtain Solution 2. S4. Use a pH meter to measure, and slowly add sodium hydroxide solution drop by drop to Solution 2 while stirring and observing the reading of the pH meter to adjust the pH value of Solution 2 to between 6 and 8. S5. Filter the prepared wetting reversal agent solution through a filter to remove impurities and insoluble substances. S6. Conduct quality inspection on the prepared wetting reversal agent. The quality inspection includes: appearance, surface tension, and wettability. S7. Package the wetting reversal agent that passes the inspection and store it in a dry, cool, and ventilated environment.

4. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that, The preparation process of petroleum sulfonate is as follows: React the petroleum fraction with concentrated sulfuric acid at 40 - 60 for 2 - 4 h, where the mass ratio of the petroleum fraction to the concentrated sulfuric acid is 3:1 - 5:1; After the reaction is completed, pour the mixture into cold water, stir for 30 - 60 min, and let it stand for layering for 2 - 3 h. Take the upper oil phase and neutralize it to a pH value of 7 - 9 with a sodium hydroxide solution with a mass fraction of 5% - 10%. After vacuum distillation, water and low-boiling impurities are distilled off at 120 - 150 under a vacuum of 0.08 - 0.1 MPa to obtain petroleum sulfonate.

5. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that: The active ingredient content of the petroleum sulfonate shall not be less than 85%, and its production process shall follow the sulfonation reaction specifications, controlling the reaction temperature in the range of 40-60 interval, and the reaction time is 3-5h; The ethylene oxide addition number of the fatty alcohol polyoxyethylene ether needs to be controlled between 5 and 10. The purity of the sodium dodecylbenzenesulfonate is required to be greater than or equal to 90%.

6. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that: During the stirring and dissolving process in Step S2, the reaction kettle should be made of stainless steel and have a jacket temperature control function. The initial set temperature during stirring is 30 , when the dissolution process is half done, heat up to 40 at a rate of 2 / minute and continue stirring until completely dissolved; The stirring paddle is designed with a double - layer turbine. The ratio of the diameter of the upper paddle to the inner diameter of the reaction kettle is 0.4 - 0.5, and the lower layer is 0.3 - 0.

4. The rotation speed is dynamically adjusted between 200 - 500 r / min according to the dissolution situation.

7. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that, In Step S3, when the addition amount of polyacrylamide is 0 - 100 parts, the addition rate is 1 - 2 parts / min. In the range of 101 - 200 parts, the rate is adjusted to 0.8 - 1.5 parts / min. When it is 201 - 300 parts, it drops to 0.5 - 1 part / min. When it exceeds 300 parts until all is added, it is maintained at 0.3 - 0.8 parts / min. During this process, the angle of the stirring paddle changes with the addition amount of polyacrylamide. Initially, the upper paddle forms an angle of 30° - 40° with the horizontal, and the lower paddle forms an angle of 20° - 30° with the horizontal. It is adjusted once every 100 parts added. Eventually, the upper layer reaches 45° - 55°, and the lower layer reaches 35° - 45°; To prevent agglomeration, sodium hexametaphosphate, a dispersant, is pre-added to Solution 1, and the addition amount is 0.5% - 1% of the mass of polyacrylamide; And throughout the process of adding polyacrylamide, circulating water is passed through the jacket of the reaction kettle to control the temperature, starting at 25 , rising by 2 every 30 minutes -3 to 35 -40 , stabilizing the stretching of polymer molecular chains and the interaction with solvent molecules to form a uniform and stable system, and improving the quality stability and performance consistency of Solution 2.

8. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that: In Step S4, a pH meter with a precision of 0.01 is used for real-time monitoring. The inner diameter of the dropper tip for dripping the sodium hydroxide solution is 0.5 - 1 mm, and the length is 5 - 10 cm. The dripping speed is dynamically adjusted according to the change in pH; When the pH value is lower than 6 and the difference ΔpH from 6 is > 0.5, the dripping speed is 10 - 15 drops per minute; When ΔpH is between 0.2 and 0.5, it is reduced to 5 - 8 drops per minute; When pH reaches 6 and ΔpH < 0.2, it is reduced to 2 - 4 drops per minute for fine adjustment; When pH exceeds 6 and is lower than 7, the dripping speed is adjusted in the reverse direction according to a similar rule based on the difference from 7. When it exceeds 7 and is lower than 8, it is reduced by 1 - 2 drops per minute for every 0.1 increase; The stirring speed changes according to the pH trend. When pH rises, it is 120 - 150 r / min, and when approaching the target value, it is reduced to 80 - 100 r / min to prevent local alkali overdose.

9. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that: The refined requirements for the filtration operation in Step S5 are as follows: The filter adopts a multi-layer composite structure, which is successively a 5 - 10 μm stainless steel filter screen, a 3 - 5 mm thick diatomite filtration layer, and an 8 - 12 μm polyethersulfone filter membrane from the inside to the outside; Before filtration, first rinse the filter 3 - 5 times with deionized water preheated to 40 - 45 equal in volume to the wetting reversal agent solution to remove impurities and contaminants; During filtration, the pressure difference is controlled at 0.2 - 0.4 MPa and adjusted according to the turbidity and flow rate of the solution. During the stage with high solution turbidity and large flow rate, the pressure difference is set at 0.3 - 0.4 MPa. When it gradually becomes clear and the flow rate decreases, it is reduced by 0.02 - 0.05 MPa every 10 minutes until it reaches 0.2 MPa to maintain stable filtration; The filtrate is collected in a light-shielded, nitrogen-filled storage tank with a temperature control of 20 -25 to prevent oxidative degradation and microbial growth. The filter layer is replaced regularly. The stainless steel filter mesh is replaced every 10 - 15 batches, the diatomaceous earth layer is replaced every 5 - 8 batches, and the polyethersulfone filter membrane is replaced every 8 - 10 batches, determined according to the filtration resistance and the quality monitoring of the filtrate.

10. The preparation method of a wettability reversal agent for oil fields according to claim 1, characterized in that: In Step S6, the appearance inspection is carried out in an observation room with a white background and an illuminance of 500 - 800 lx. The solution should be clear, transparent, without precipitation and flocculation, and its color is white to light yellow; The pendant drop method is combined with the Wilhelmy plate method for surface tension detection. The pendant drop method measures the static tension, and the plate method measures the dynamic tension. At 25 Under this condition, the static value of 28 - 32 mN / m and the dynamic value of 30 - 34 mN / m are qualified; The wettability detection adopts the contact angle measurement method. A quartz glass slide is used to simulate the reservoir rock. The droplet volume is 5 - 8 μL, and the average value is taken from 5 measurements. For the water contact angle, it should be 100° - 120° before inversion and ≤ 60° after inversion to meet the standard; for the oil contact angle, it should be 20° - 30° before inversion and ≥ 80° after inversion to be qualified.

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