Method for evaluating performance of oilfield chemical agent

Abstract

The invention relates to the technical field of chemical agent performance evaluation, in particular to an oilfield chemical agent performance evaluation method. The evaluation method comprises the steps of substrate pretreatment, probe pretreatment, test environment construction, probe position adjustment, laser adjustment, optical lever amplification ratio setting, displacement-force signal conversion, force-distance curve acquisition, adhesion spectrogram acquisition, data processing and the like to obtain the oil-rock mean adhesion before chemical agent treatment. And taking out the substrate, soaking the substrate in a chemical agent solution system, repeating the steps to obtain the average oil-rock adhesion after chemical agent treatment, and evaluating the performance of the chemical agent based on the average oil-rock adhesion before / after chemical agent treatment. By applying the evaluation method, rapid and accurate evaluation of the performance of the chemical agent under the nanoscale can be realized, and guidance is provided for design and optimization of the chemical agent.

Description

Technical Field

[0001] This invention relates to the field of chemical agent performance evaluation technology, specifically to a method for evaluating the performance of oilfield chemical agents, and more specifically to a method for evaluating the performance of oilfield chemical agents based on atomic force microscopy. Background Technology

[0002] In the development of unconventional oil reservoirs, chemical agents such as surfactants, polymers, and nanofluids have become important means to enhance oil recovery. They significantly improve flow behavior within porous media through microscopic effects such as reducing oil-water interfacial tension, regulating rock wettability, and weakening bituminous deposition. Especially in nano- and micro-porous networks, the extent to which chemical agents weaken the adhesion between crude oil and rock walls directly determines the mobility of residual oil. Therefore, accurately evaluating this nanoscale mechanical effect is crucial for chemical agent screening and formulation optimization.

[0003] Traditional evaluation methods remain at the macroscopic average level. Interfacial tensiometers calculate overall tension by rotating droplet morphology, and contact angle meters provide the average wetting angle based on droplet profiles. Neither can distinguish the heterogeneous characteristics of the rock surface, making it difficult to accurately quantify the impact of chemicals on the adhesion between crude oil and rock at the nanoscale. This limitation leads to inaccurate performance evaluation of oilfield chemicals, hindering the design and optimization of these chemicals.

[0004] Therefore, there is an urgent need for a method to evaluate the performance of oilfield chemicals in order to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to address the problem in the prior art that the influence of chemical agents on the adhesion force between crude oil and rock at the nanoscale cannot be accurately quantified, which makes it difficult to accurately evaluate the performance of chemical agents, and to provide a method for evaluating the performance of oilfield chemical agents.

[0006] To achieve the above objectives, the present invention provides a method for evaluating the performance of oilfield chemical agents, the method comprising the following steps: S1. Test environment setup: Place the probe in the liquid probe holder and clamp the tipless cantilever beam end in the probe holder, leaving the probe end exposed and suspended. Then fill the probe holder with liquid phase to create a sealed environment, and then place the probe holder on top of the substrate. S2. Probe position adjustment: Adjust the mineral sheet and probe clip to the center of the AFM sample stage, and then adjust the height of the sample stage so that the mineral sheet is close to but does not touch the cantilever beam. S3. Secondary adjustment of probe position: Focus the optical microscope on the substrate, adjust the field of view so that the probe cantilever is on one side of the image window and the probe tip is in the center of the field of view. Then adjust the height of the sample stage so that the probe is close to the substrate surface, and stop when the probe cantilever is clear. S4. Laser adjustment: Adjust the laser spot to the center of the probe tip, and then adjust the reflector above the sample stage to make the laser spot in the image window the brightest. S5. Set the optical lever amplification ratio and perform displacement-force signal conversion; S6. Force-distance curve acquisition: In force measurement mode, control the piezoelectric ceramic tube to approach and / or move away from the substrate at a constant speed to complete a single force-distance curve acquisition. S7. Adhesion force spectrum acquisition: Set the needle stop time, scanning range and number of scans, repeat the single force-distance curve acquisition operation to obtain the adhesion force spectrum of crude oil-rock surface, move the substrate position, repeat the scan, and retain multiple test data with small spectrum fluctuations and stable data. S8. Data processing: Adhesion force data is obtained by statistically analyzing test data from multiple measurement areas of the substrate. Then, a frequency distribution histogram is plotted based on the adhesion force data, and the mean oil-rock adhesion force before chemical treatment is obtained by Gaussian fitting. S9. Remove the substrate and immerse it in the chemical agent solution system. Repeat the above steps S1-S8 to obtain the average oil-rock adhesion force after chemical treatment. Then, evaluate the performance of the chemical agent based on the average oil-rock adhesion force before and after chemical treatment.

[0007] Preferably, the method further includes the following steps before step S1: S01, Substrate pretreatment: After pretreatment, the mineral sheet is placed on the AFM sample stage; S02, Probe Pretreatment: Soak the probe, then remove it and blow it dry.

[0008] Preferably, in step S01, the substrate pretreatment specifically includes: Cut the mineral sheet according to the size of the AFM test stage, grind it, immerse it in the cleaning solution for the first set time, then sonicate it in deionized water for the second set time multiple times and dry it, then install the mineral sheet on the circular iron plate, and finally place the mineral sheet on the AFM sample stage.

[0009] Preferably, in step S02, probe preprocessing specifically includes: After immersing the probe in deionized water for a third set time, remove it and dry it with a protective gas. Then, immerse the probe in a functionalized modification material solution for a fourth set time and remove it to dry it with a protective gas.

[0010] Preferably, the cleaning solution is a sodium hydroxide solution with a mass fraction of 8-12%, the first set time is 10-14h, the second set time is 0.5-1.5h, the number of ultrasonic treatments is 2-4, the drying temperature is 80-100℃, the diameter of the circular iron sheet is 8-12mm, and the thickness is 0.4-0.6mm.

[0011] Preferably, the third setting time is 1-3 hours, the protective gas is nitrogen, and the functionalized modification material solution is 1-dodecyl mercaptan with a concentration of 0.008-0.012 mol·L⁻¹. -1 The fourth set duration is 10-14 hours.

[0012] Preferably, in step S1, before filling the liquid phase, a vacuum degassing pipeline is connected to degas the liquid phase solution for a fifth set time, which is 20-30 hours; the probe clamp outlet is equipped with a 0.1-0.3 μm microporous filter; the liquid phase is deionized water or mineralized water, and the mineralization range of the mineralized water is 0-60000 mg·L. -1 .

[0013] Preferably, in step S5, the basis for setting the optical lever amplification ratio and performing displacement-force signal conversion is as follows: ; ; in, A The optical leverage ratio, L The length of the reflected light path. l The effective length of the cantilever beam. F For adhesion, k Let be the elastic constant of the cantilever beam. This refers to the displacement of the light spot detected by the photoelectric position sensor.

[0014] Preferably, in step S7, the needle stop time is 30-60 seconds.

[0015] Preferably, in step S8, data processing specifically includes: Test data from multiple measurement areas of the substrate were imported into NanoScope Analysis software. Then, the statistically obtained adhesion force data were imported into Origin software. A frequency distribution histogram was plotted based on Origin software, and the mean oil-rock adhesion force before chemical treatment was obtained by Gaussian fitting.

[0016] According to the above technical solution, based on the performance evaluation method of oilfield chemical agents, the average oil-rock adhesion force before chemical agent treatment is obtained through steps such as test environment construction, probe position adjustment, laser adjustment, setting the optical lever amplification ratio, displacement-force signal conversion, force-distance curve acquisition, adhesion force spectrum acquisition, and data processing. Then, the substrate is taken out and immersed in the chemical agent solution system, and the above steps are repeated to obtain the average oil-rock adhesion force after chemical agent treatment. Based on the average oil-rock adhesion force before and after chemical agent treatment, the performance of the chemical agent is evaluated. In practical applications, it can realize rapid and accurate evaluation of the performance of chemical agents at the nanoscale and provide guidance for the design and optimization of chemical agents. Attached Figure Description

[0017] Figure 1 This is a flowchart of the performance evaluation method for oilfield chemical agents; Figure 2 This is a schematic diagram of the light lever principle; Figure 3 This is the adhesion force spectrum of Example 1 before surfactant treatment; Figure 4 This is an adhesion force distribution diagram before surfactant treatment in Example 1; Figure 5 This is the adhesion force spectrum after surfactant treatment in Example 1; Figure 6 This is an adhesion force distribution diagram after surfactant treatment in Example 1; Figure 7 This is the adhesion force spectrum before surfactant treatment in Example 9. Detailed Implementation

[0018] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the present invention.

[0019] This invention provides a method for evaluating the performance of oilfield chemical agents, such as... Figure 1-2 As shown, the oilfield chemical agent performance evaluation method includes the following steps: S1. Test environment setup: Place the probe in the liquid probe holder and clamp the tipless cantilever beam end in the probe holder, leaving the probe end exposed and suspended. Then fill the probe holder with liquid phase to create a sealed environment, and then place the probe holder on top of the substrate. S2. Probe Position Adjustment: Adjust the mineral slide and probe clip to the center of the AFM (Atomic Force Microscope) sample stage, and then adjust the height of the sample stage so that the mineral slide is close to but does not touch the cantilever beam; specifically, the distance between the mineral slide and the cantilever beam is 0.5-1 mm. S3. Secondary adjustment of probe position: Focus the optical microscope on the substrate, adjust the field of view so that the probe cantilever is on one side of the image window and the probe tip is in the center of the field of view. Then adjust the height of the sample stage to bring the probe closer to the substrate surface, and stop when the probe cantilever is clear. Specifically, in the process of bringing the probe closer to the substrate surface, it is necessary to stop when the probe cantilever is basically clear to avoid breaking the probe when it is completely clear. S4. Laser adjustment: Adjust the laser spot to the center of the probe tip, and then adjust the reflector above the sample stage to make the laser spot in the image window the brightest. S5. Set the optical lever amplification ratio and perform displacement-force signal conversion; S6. Force-distance curve acquisition: In force measurement mode, the piezoelectric ceramic tube is controlled to approach and / or move away from the substrate at a constant speed to complete a single force-distance curve acquisition; specifically, the constant speed is 0.5-2 μm / s; S7. Adhesion force spectrum acquisition: Set the needle stop time, scanning range and number of scans, repeat the single force-distance curve acquisition operation to obtain the adhesion force spectrum of crude oil-rock surface, move the substrate position, repeat the scan, and retain multiple test data with small spectrum fluctuations and stable data; specifically, the scanning range is a square area with a side length of 2-5 μm, and the number of scanning points is 64-256; S8. Data processing: Adhesion force data is obtained by statistically analyzing test data from multiple measurement areas of the substrate. Then, a frequency distribution histogram is plotted based on the adhesion force data, and the mean oil-rock adhesion force before chemical treatment is obtained by Gaussian fitting. S9. Remove the substrate and immerse it in the chemical agent solution system. Repeat the above steps S1-S8 to obtain the average oil-rock adhesion force after chemical treatment. Then, evaluate the performance of the chemical agent based on the average oil-rock adhesion force before and after chemical treatment.

[0020] Based on the above technical solution, and based on the performance evaluation method of oilfield chemical agents, the dynamic changes of oil-rock adhesion force before and after the chemical agent is applied are quantitatively characterized by the optical lever principle and AFM in-situ force measurement technology. This method overcomes the limitations of traditional interfacial tension or contact angle measurements in capturing the mechanical properties of nanoscale oil film peeling. It can quickly and accurately quantify the enhancement effect of oilfield chemical agents on oil film desorption and provide guidance for the design and optimization of chemical agents.

[0021] In the oilfield chemical agent performance evaluation method of the present invention, preferably, the method further includes the following step before step S1: S01, Substrate pretreatment: After pretreatment, the mineral sheet is placed on the AFM sample stage; S02, Probe Pretreatment: Soak the probe, then remove it and blow it dry.

[0022] In this embodiment of the invention, by preprocessing the substrate and probe before step S1, the accuracy of the subsequent evaluation results can be effectively guaranteed.

[0023] Specifically, in order to further improve the effect of substrate pretreatment, step S01, substrate pretreatment, specifically includes: Mineral slices are cut according to the dimensions of the AFM testing stage, polished, and then immersed in a cleaning solution for a first set time. Next, they are ultrasonically soaked in deionized water for a second set time multiple times, then dried. The mineral slices are then mounted on a circular iron plate, and finally placed on the AFM sample stage. The cleaning solution is an 8-12% sodium hydroxide solution. The first set time is 10-14 hours, the second set time is 0.5-1.5 hours, the ultrasonic treatment is performed 2-4 times, the drying temperature is 80-100℃, and the diameter of the circular iron plate is 8-12 mm, with a thickness of 0.4-0.6 mm. The mineral slices can, in principle, be any hard and smooth mineral slices.

[0024] To further improve the effectiveness of probe pretreatment, step S02 specifically includes: The probe is immersed in deionized water for a third predetermined time, then removed and dried with a protective gas. Next, the probe is immersed in a functionalized modification material solution for a fourth predetermined time, then removed and dried with a protective gas. The third predetermined time is 1-3 hours, the protective gas is nitrogen, and the functionalized modification material solution is 1-dodecylthiol with a concentration of 0.008-0.012 mol·L⁻¹. -1 The fourth set duration is 10-14 hours.

[0025] In the oilfield chemical agent performance evaluation method of the present invention, preferably, in step S1, before filling the liquid phase, a vacuum degassing pipeline is connected to degas the liquid phase solution for a fifth set time, wherein the fifth set time is 20-30 h. In another preferred embodiment, the probe clamp outlet is provided with a 0.1-0.3 μm microporous filter element. In a specific embodiment, the liquid phase is deionized water or mineralized water, wherein the mineralization range of the mineralized water is 0-60000 mg·L. -1 .

[0026] In this embodiment of the invention, by connecting a vacuum degassing pipeline to degas the liquid phase solution before filling, the presence of microbubbles in the solution can be prevented from affecting the measurement results. Furthermore, by setting a microporous filter element at the probe clamp outlet, crystallization particles can be further intercepted, ensuring repeatability and accuracy under high mineralization conditions.

[0027] In the oilfield chemical agent performance evaluation method of the present invention, preferably, in step S5, the basis for setting the optical lever amplification ratio and performing displacement-force signal conversion is as follows: ; ; in, A The optical leverage ratio, L The length of the reflected light path. l The effective length of the cantilever beam. F For adhesion, k Let be the elastic constant of the cantilever beam. This refers to the displacement of the light spot detected by the photoelectric position sensor.

[0028] In this embodiment of the invention, by setting the optical lever amplification ratio of the AFM to 800-1200, sufficient force measurement accuracy can be ensured. That is, when the displacement of the cantilever beam under bending force is at the nanometer level, the displacement of the laser spot received by the photoelectric position sensor is at the micrometer level; and by utilizing its relationship with the length of the reflected optical path... L With the effective length of the cantilever beam l The relationship between the cantilever beam displacement and Hooke's Law can be used to convert the displacement of the cantilever beam into adhesion force.

[0029] In the oilfield chemical agent performance evaluation method of the present invention, preferably, in step S7, the needle stop time is 30-60 s, so as to avoid fluctuations in the obtained adhesion force spectrum, which would lead to a significant reduction in sampling accuracy, and ensure that the probe tip is in full contact with the oil film and rock substrate, so that the interface adsorption-desorption reaches dynamic equilibrium.

[0030] In the oilfield chemical agent performance evaluation method of the present invention, preferably, in step S8, data processing specifically includes: Test data from multiple measurement areas of the substrate were imported into NanoScope Analysis software. Then, the statistically obtained adhesion force data were imported into Origin software. A frequency distribution histogram was plotted based on Origin software, and the mean oil-rock adhesion force before chemical treatment was obtained by Gaussian fitting, thus accurately obtaining the mean oil-rock adhesion force.

[0031] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] Example 1 Adopting such Figure 1-6 The oilfield chemical performance evaluation method shown herein includes the following steps: S01, Substrate pretreatment: After pretreatment, the mineral sheet is placed on the AFM sample stage; S02, Probe Pretreatment: Immerse the probe, then remove and dry it; S1. Test environment setup: Place the probe in the liquid probe holder and clamp the tipless cantilever beam end in the probe holder, leaving the probe end exposed and suspended. Then fill the probe holder with liquid phase to create a sealed environment, and then place the probe holder on top of the substrate. S2. Probe position adjustment: Adjust the mineral sheet and probe clip to the center of the AFM sample stage, and then adjust the height of the sample stage so that the mineral sheet is close to but does not touch the cantilever beam. S3. Secondary adjustment of probe position: Focus the optical microscope on the substrate, adjust the field of view so that the probe cantilever is on one side of the image window and the probe tip is in the center of the field of view. Then adjust the height of the sample stage so that the probe is close to the substrate surface, and stop when the probe cantilever is clear. S4. Laser adjustment: Adjust the laser spot to the center of the probe tip, and then adjust the reflector above the sample stage to make the laser spot in the image window the brightest. S5. Set the optical lever amplification ratio and perform displacement-force signal conversion; S6. Force-distance curve acquisition: In force measurement mode, control the piezoelectric ceramic tube to approach and / or move away from the substrate at a constant speed to complete a single force-distance curve acquisition. S7. Adhesion force spectrum acquisition: Set the needle stop time, scanning range and number of scans, repeat the single force-distance curve acquisition operation to obtain the adhesion force spectrum of crude oil-rock surface, move the substrate position, repeat the scan, and retain multiple test data with small spectrum fluctuations and stable data. S8. Data processing: Adhesion force data is obtained by statistically analyzing test data from multiple measurement areas of the substrate. Then, a frequency distribution histogram is plotted based on the adhesion force data, and the mean oil-rock adhesion force before chemical treatment is obtained by Gaussian fitting. S9. Remove the substrate and immerse it in the chemical agent solution system for 2-12 hours. Repeat the above steps S1-S8 to obtain the average oil-rock adhesion force after chemical treatment. Then, evaluate the performance of the chemical agent based on the average oil-rock adhesion force before / after chemical treatment. Specifically, in step S01, the substrate is pretreated by cutting a rock slice into 10×10×1 mm pieces, polishing it smooth, and then soaking it in a 10% sodium hydroxide solution for 12 h to remove organic matter from the surface and hydroxylate the surface. Then, it is ultrasonicated three times in deionized water for 2 h each time, dried in a 90℃ oven, and then the rock slice is glued to a circular iron sheet using double-sided tape. Finally, it is placed on the sample stage of an atomic force microscope. In step S02, probe pretreatment: The probe used was NPG-10, with an elastic constant of 0.4219 N / m and a tip radius of 50 nm. Using AFM-specific non-magnetic stainless steel tweezers, the probe was gently placed in a beaker containing deionized water and immersed for 2 hours. After removal, it was dried with pure nitrogen gas and then immersed in a solution of 0.01 mol·L⁻¹. -1 The solution was placed in a 1-dodecylthiol solution and removed after 12 hours, then dried with pure nitrogen. In step S1, the test environment is set up as follows: using non-magnetic stainless steel tweezers, the probe is picked up and placed in a liquid probe holder, with the tipless cantilever beam end inserted into the probe holder and clamped, while the probe end is exposed and suspended. Deionized water is then filled into the liquid using a syringe connected to the probe holder. Before filling, the deionized water is degassed for 24 hours using a vacuum pump to prevent the presence of microbubbles in the solution from affecting the measurement results. A 0.2 µm microporous filter is placed at the probe holder outlet to further intercept crystallization particles and ensure repeatability and accuracy under high mineralization conditions. Finally, the probe holder is placed on top of the substrate. In step S2, the probe position is adjusted once: the circular iron plate with the rock piece attached is adjusted to the center of the sample stage, and the height of the sample stage is adjusted so that the distance between the rock piece and the cantilever beam is 1 mm. In step S3, the probe position is adjusted a second time: the position of the optical microscope is adjusted so that the probe and the substrate can be clearly seen when it is focused from top to bottom; then the optical microscope is focused on the substrate, and the field of view is adjusted so that the probe cantilever is on the right side of the image window and the probe tip is in the center of the field of view; then the height of the sample stage is adjusted so that the probe is close to the surface of the substrate, and the adjustment is stopped when the probe cantilever is basically clear. In step S4, laser adjustment: Adjust the two knobs in the AFM device that control the laser incident position to adjust the laser spot to the center of the probe tip. Then adjust the reflector above the sample stage to make the laser spot in the image window the brightest, specifically to make the SUM value in AFM reach 3.60. In step S5, the optical lever amplification ratio is set and the displacement-force signal is converted: the optical lever amplification ratio A of the AFM used is 1000 to ensure sufficient force measurement accuracy. The displacement of the cantilever beam can be converted into adhesion force by using its relationship with the reflected light path length L and the effective length l of the cantilever beam and Hooke's law. In step S6, force-distance curve acquisition: In Force Volume mode, the piezoelectric ceramic tube is controlled to move at a distance of 1 μm·s. -1 The probe moves closer to and further away from the substrate at a constant speed. The laser captures the displacement of the probe cantilever beam and converts it into laser spot displacement through the optical lever principle. Then, the displacement is converted into force through a photoelectric displacement sensor to complete the acquisition of a single force-distance curve. In step S7, the adhesion force spectrum is acquired: the needle stop time is set to 60 s, the scanning range is a square area with a side length of 5 μm, the number of scanning points is 256, and the single force-distance curve acquisition operation is repeated to obtain the adhesion force spectrum of crude oil-rock surface; the substrate position is manually moved, the scan is repeated, and the test results with small spectrum fluctuations and stable data are retained for 3 times; In step S8, data processing: the test data of the three measurement areas of the substrate are imported into NanoScopeAnalysis software, and then the statistically obtained adhesion force data are imported into Origin software. Based on Origin software, a frequency distribution histogram is plotted, and the mean oil-rock adhesion force on the surface of the rock sheet before chemical treatment is obtained by Gaussian fitting as 10.23 nN. In step S9, the substrate was removed and immersed in a 0.1% AOS solution for 2 hours. The above test steps S01-S8 were repeated, and the oil-rock adhesion force on the surface of the rock sheet after chemical treatment was obtained as 8.27 nN by Gaussian fitting.

[0033] Using the oilfield chemical agent performance evaluation method described in this invention, after soaking in a 0.1% AOS (sodium α-alkenyl sulfonate) solution for 2 hours, the oil-rock adhesion of rock flakes decreased by 1.96 nN, achieving rapid and accurate evaluation of chemical agent performance at the nanoscale.

[0034] Example 2 Following the method described in Example 1, except that the soaking solution for the substrate in step 9 was replaced with a 0.1% CHSB solution (cocamidopropyl hydroxysulfonate betaine). Gaussian fitting was used to obtain the original oil-rock adhesion force on the rock sheet surface as 10.34 nN. After chemical treatment, the oil-rock adhesion force on the rock sheet surface was 8.72 nN. After soaking in a 0.1% CHSB solution for 2 hours, the oil-rock adhesion force of the rock sheet decreased by 1.62 nN. Compared with the method in Example 1, this shows that the zwitterionic surfactant CHSB has a weaker ability to reduce oil-rock adhesion force than the anionic surfactant AOS.

[0035] Example 3 The same method was implemented as in Example 1, except that the soaking time in step 9 was changed to 4 h. The original oil-rock adhesion force on the surface of the rock sheet was 10.31 nN obtained by Gaussian fitting. After chemical treatment, the oil-rock adhesion force on the surface of the rock sheet was 6.74 nN. After soaking in AOS solution with a mass concentration of 0.1% for 4 h, the oil-rock adhesion force of the rock sheet decreased by 3.57 nN.

[0036] Example 4 The same method was implemented as in Example 1, except that the soaking time in step 9 was changed to 8 h. The original oil-rock adhesion force on the surface of the rock sheet was 11.45 nN obtained by Gaussian fitting. After chemical treatment, the oil-rock adhesion force on the surface of the rock sheet was 6.14 nN. After soaking in AOS solution with a mass concentration of 0.1% for 8 h, the oil-rock adhesion force of the rock sheet decreased by 5.31 nN.

[0037] Example 5 The same method was implemented as in Example 1, except that the soaking time in step 9 was changed to 12 h. The original oil-rock adhesion force on the surface of the rock sheet was 10.76 nN obtained by Gaussian fitting. After chemical treatment, the oil-rock adhesion force on the surface of the rock sheet was 4.48 nN. After soaking in AOS solution with a mass concentration of 0.1% for 12 h, the oil-rock adhesion force of the rock sheet decreased by 6.28 nN.

[0038] As can be seen from Examples 3-5 above, as the soaking time increases, the effect of the chemical agent on reducing the adhesion between oil and rock is enhanced, which is beneficial for oil film peeling, but the enhancing effect is weakened.

[0039] Example 6 Following the implementation of Example 1, except that the mass concentration of AOS in step 9 was changed to 0.3%, the original oil-rock adhesion force on the rock sheet surface was obtained as 11.03 nN by Gaussian fitting, and the oil-rock adhesion force on the rock sheet surface after chemical treatment was 7.82 nN. After soaking in a 0.3% AOS solution for 2 hours, the oil-rock adhesion force of the rock sheet decreased by 3.21 nN. Compared with the scheme in Example 1, this shows that as the concentration of chemical agent increases, the effect of chemical agent on reducing oil-rock adhesion force is enhanced, which is beneficial to oil film peeling.

[0040] Example 7 The procedure was carried out in accordance with Example 1, except that the liquid phase testing environment in step 1 was changed to 60,000 mg·L⁻¹. -1 The original oil-rock adhesion force on the rock sheet surface was 10.57 nN obtained by Gaussian fitting of NaCl aqueous solution. After chemical treatment, the oil-rock adhesion force on the rock sheet surface was 9.68 nN. After soaking in 0.1% AOS solution for 2 h, the oil-rock adhesion force of the rock sheet decreased by 0.89 nN. Compared with the scheme in Example 1, this shows that as the environmental mineralization increases, the chemical agent is affected by ions in the liquid phase, and the effect is weakened.

[0041] Example 8 Referring to Example 1, the difference is that the optical lever amplification ratio in step S5 is set to the conventional 300. It was found that under this optical lever amplification ratio, the data in the obtained adhesion force frequency distribution map is scattered, with weak normality, making it difficult to fit the mean adhesion force. Moreover, the signal-to-noise ratio is low, and it is easily affected by environmental vibration. Repeated experiments yield large differences in adhesion force with low accuracy. However, by actively adjusting the optical lever amplification ratio to 1000 using the optical lever amplification ratio formula, which is 300-500 higher than the conventional value, the nanoscale cantilever beam displacement can be amplified to the micrometer spot displacement, thereby increasing the signal intensity of the photoelectric sensor by 2-3 times and significantly improving the signal-to-noise ratio. Experimental verification shows that the force measurement error is reduced to within 5%, achieving accurate quantification of nanonewton-level adhesion force.

[0042] Example 9 Referring to Example 1, the difference is that the needle stop time in step S7 was set to 5 seconds. It was found that at this needle stop time, the obtained adhesion force spectrum was prone to fluctuations, such as... Figure 7 As shown, this leads to a significant reduction in sampling accuracy. However, by setting the needle stop time to 60 s, it is possible to ensure that the probe tip is in full contact with the oil film and rock substrate, so that the interface adsorption-desorption reaches a dynamic balance. Experimental data show that the repeatability of the force curve is improved to over 80%, and the standard deviation of the adhesion force measured multiple times in the same area is reduced from ±1.5 nN to ±0.3 nN.

[0043] Example 10 The experiment was carried out in accordance with Example 1, except that a vacuum degassing pipeline was not connected in step S1 and a microporous filter was not installed at the probe clamp outlet. It was found that during the test, when the sample stage was adjusted to bring the probe close to the substrate, air bubbles were easily generated, causing the test to be interrupted. In addition, some salt crystals precipitated in the probe clamp after the test, resulting in fluctuations in the test results. However, by connecting a vacuum degassing pipeline and installing a microporous filter at the probe clamp outlet, air bubbles in the solution can be effectively avoided, and the accuracy of the test can be guaranteed in a solution with the same salinity as the actual reservoir formation water.

[0044] Example 11 The experiment was carried out in accordance with Example 1, except that in step S02, the probe was soaked in deionized water and then dried with a protective gas. Instead of soaking the probe in the functionalized modification material solution and then drying it with a protective gas, the test results were found to be significantly lower than those in the other examples above, with an average adhesion force of about 3.67 nN. Further research revealed that this is because the surface of conventional AFM probes is bare metal, such as gold-plated probes, which have low affinity for crude oil and cannot simulate the real interaction between crude oil and rock surfaces.

[0045] Example 12 Following the implementation of Example 1, the difference is that only one complete scan was performed in step S7, without manually moving the substrate position for repeated scans. The test results were found to be significantly greater than those of the other examples, with an average adhesion force of approximately 15.20 nN. Further research revealed that this was because although the rock sheet had been polished smooth, it still exhibited microscopic heterogeneity in mineral composition and roughness. Directly applying AFM only measured a single area, ignoring the heterogeneity of the rock surface. Consequently, the results could not represent the overall adhesion force characteristics of the oil-rock interface, leading to a biased evaluation of the chemical agent's performance. However, by manually moving the substrate position and repeating the scan, retaining three test results with small spectral fluctuations and stable data, and combining this with the Gaussian fitting statistical mean adhesion force in step 8, the influence of heterogeneity could be effectively eliminated. Experiments showed that the representativeness of the results increased from 60% in a single area to over 90%.

[0046] The oilfield chemical agent performance evaluation method provided by this invention obtains the average oil-rock adhesion force before chemical agent treatment through steps such as test environment construction, probe position adjustment, laser adjustment, setting optical lever amplification ratio, displacement-force signal conversion, force-distance curve acquisition, adhesion force spectrum acquisition, and data processing. Then, the substrate is removed and immersed in the chemical agent solution system, and the above steps are repeated to obtain the average oil-rock adhesion force after chemical agent treatment. Based on the average oil-rock adhesion force before and after chemical agent treatment, the performance of the chemical agent is evaluated. In practical applications, it can realize rapid and accurate evaluation of the performance of chemical agents at the nanoscale and provide guidance for the design and optimization of chemical agents.

[0047] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention. To avoid unnecessary repetition, the present invention will not describe all possible combinations separately. However, these simple modifications and combinations should also be considered as part of the content disclosed in this invention and are all within the protection scope of this invention.

Claims

1. A method for evaluating the performance of oilfield chemical agents, characterized in that, The method for evaluating the performance of oilfield chemical agents includes the following steps: S1. Test environment setup: Place the probe in the liquid probe holder and clamp the tipless cantilever beam end in the probe holder, leaving the probe end exposed and suspended. Then fill the probe holder with liquid phase to create a sealed environment, and then place the probe holder on top of the substrate. S2. Probe position adjustment: Adjust the mineral sheet and probe clip to the center of the AFM sample stage, and then adjust the height of the sample stage so that the mineral sheet is close to but does not touch the cantilever beam. S3. Secondary adjustment of probe position: Focus the optical microscope on the substrate, adjust the field of view so that the probe cantilever is on one side of the image window and the probe tip is in the center of the field of view. Then adjust the height of the sample stage so that the probe is close to the substrate surface, and stop when the probe cantilever is clear. S4. Laser adjustment: Adjust the laser spot to the center of the probe tip, and then adjust the reflector above the sample stage to make the laser spot in the image window the brightest. S5. Set the optical lever amplification ratio and perform displacement-force signal conversion; S6. Force-distance curve acquisition: In force measurement mode, control the piezoelectric ceramic tube to approach and / or move away from the substrate at a constant speed to complete a single force-distance curve acquisition. S7. Adhesion force spectrum acquisition: Set the needle stop time, scanning range and number of scans, repeat the single force-distance curve acquisition operation to obtain the adhesion force spectrum of crude oil-rock surface, move the substrate position, repeat the scan, and retain multiple test data with small spectrum fluctuations and stable data. S8. Data processing: Adhesion force data is obtained by statistically analyzing test data from multiple measurement areas of the substrate. Then, a frequency distribution histogram is plotted based on the adhesion force data, and the mean oil-rock adhesion force before chemical treatment is obtained by Gaussian fitting. S9. Remove the substrate and immerse it in the chemical agent solution system. Repeat the above steps S1-S8 to obtain the average oil-rock adhesion force after chemical treatment. Then, evaluate the performance of the chemical agent based on the average oil-rock adhesion force before and after chemical treatment.

2. The method for evaluating the performance of oilfield chemical agents according to claim 1, characterized in that, The steps preceding step S1 also include: S01, Substrate pretreatment: After pretreatment, the mineral sheet is placed on the AFM sample stage; S02, Probe Pretreatment: Soak the probe, then remove it and blow it dry.

3. The method for evaluating the performance of oilfield chemical agents according to claim 2, characterized in that, In step S01, substrate pretreatment specifically includes: Cut the mineral sheet according to the size of the AFM test stage, grind it, immerse it in the cleaning solution for the first set time, then sonicate it in deionized water for the second set time multiple times and dry it, then install the mineral sheet on the circular iron plate, and finally place the mineral sheet on the AFM sample stage.

4. The method for evaluating the performance of oilfield chemical agents according to claim 2, characterized in that, In step S02, probe preprocessing specifically includes: After immersing the probe in deionized water for a third set time, remove it and dry it with a protective gas. Then, immerse the probe in a functionalized modification material solution for a fourth set time and remove it to dry it with a protective gas.

5. The method for evaluating the performance of oilfield chemical agents according to claim 3, characterized in that, The cleaning solution is a sodium hydroxide solution with a mass fraction of 8-12%. The first set time is 10-14 hours, the second set time is 0.5-1.5 hours, the number of ultrasonic treatments is 2-4, the drying temperature is 80-100℃, and the diameter of the circular iron sheet is 8-12 mm and the thickness is 0.4-0.6 mm.

6. The method for evaluating the performance of oilfield chemical agents according to claim 4, characterized in that, The third setting duration is 1-3 hours, the protective gas is nitrogen, and the functionalized modification material solution is 1-dodecyl mercaptan with a concentration of 0.008-0.012 mol·L⁻¹. -1 The fourth set duration is 10-14 hours.

7. The method for evaluating the performance of oilfield chemical agents according to any one of claims 1-6, characterized in that, In step S1, before filling the liquid phase, a vacuum degassing pipeline is connected to degas the liquid phase solution for a fifth set time, which is 20-30 hours; the probe clamp outlet is equipped with a 0.1-0.3 μm microporous filter; the liquid phase is deionized water or mineralized water, and the mineralization range of the mineralized water is 0-60000 mg·L. -1 .

8. The method for evaluating the performance of oilfield chemical agents according to claim 1, characterized in that, In step S5, the basis for setting the optical lever amplification ratio and performing displacement-force signal conversion is as follows: ； ； in, A The optical leverage ratio, L The length of the reflected light path. l The effective length of the cantilever beam. F For adhesion, k Let be the elastic constant of the cantilever beam. This refers to the displacement of the light spot detected by the photoelectric position sensor.

9. The method for evaluating the performance of oilfield chemical agents according to claim 1, characterized in that, In step S7, the needle stop time is 30-60 seconds.

10. The method for evaluating the performance of oilfield chemical agents according to claim 1, characterized in that, Step S8, data processing, specifically includes: Test data from multiple measurement areas of the substrate were imported into NanoScope Analysis software. Then, the statistically obtained adhesion force data were imported into Origin software. A frequency distribution histogram was plotted based on Origin software, and the mean oil-rock adhesion force before chemical treatment was obtained by Gaussian fitting.

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