A method for measuring the interaction force between oil droplets

Abstract

The present invention relates to a method for measuring the interaction force between oil droplets and oil droplets, which comprises: preparing ternary composite drive produced water containing a crude oil droplet i to be tested, scanning the surface microscopic morphology of the ternary composite drive produced water to be tested, and determining the position of the crude oil droplet i to be tested; modifying the probe, adhering the oil droplet ii to be tested to the probe, inserting the needle in the center of each crude oil droplet i to be tested, and obtaining the force curve between the crude oil droplet i to be tested and the oil droplet ii to be tested; under the high salt condition of salinity>1mol / L NaCl, shielding the double electric layer repulsion, and obtaining the force curve between the crude oil droplet i to be tested and the oil droplet ii to be tested again; according to each force curve obtained, obtaining the microscopic surface force type result of the crude oil droplet i to be tested and the oil droplet ii to be tested in a unit area. The present invention can explain the interaction force in the process of oil droplet aggregation from a microscopic perspective, and measure and evaluate the microscopic force between variable particles.

Description

Technical field:

[0001] The present invention relates to a method for microscopic quantitative analysis of oil drop force problems in the field of petroleum engineering, and specifically to a method for measuring the interaction force between oil droplets. Background technology:

[0002] The ternary composite flooding (alkali-polymer-surfactant) technology is a method developed on the basis of alkali-polymer flooding and surfactant-polymer flooding to significantly improve the recovery rate. It can increase the recovery rate by more than 20 percentage points under the extreme exploitation conditions of the oil field water content reaching 98%.

[0003] Due to the addition of alkali, polymer and surfactant, the synergistic effect between the three elements makes the produced water of ASP flooding more difficult to treat than that of water flooding. Some conventional oil-water separation technologies become ineffective in the treatment of produced water of ASP flooding, thus limiting the promotion of ASP flooding technology. At the same time, the produced water of ASP flooding is generally used for reinjection into the formation to maintain the formation pressure after treatment, and a small amount will be discharged into the environment. However, the existing ground equipment in the oil field has gradually failed to make the treatment of ASP produced water meet the standards of reinjection or discharge, which not only increases the cost of oil field ground equipment transformation, but also brings challenges to environmental protection.

[0004] The fundamental reason why it is difficult to achieve a breakthrough in the treatment technology of ASP flooding produced water is that there is insufficient research on the interfacial dynamics of oil droplets in the produced water of ASP flooding and the laws and mechanisms of coalescence between oil droplets.

[0005] The coalescence of droplets depends on the mechanical effect of two droplets colliding with each other. Therefore, the study of the interaction force between two droplets is helpful to further deepen the microscopic understanding of the dispersed phase system and deepen the study of demulsification mechanism, which is of great significance. Summary of the invention:

[0006] The purpose of the present invention is to provide a method for measuring the interaction force between oil droplets. This method for measuring the interaction force between oil droplets is used to solve the problem that the existing technology cannot quantitatively characterize the interaction force between two oil droplets, and to measure and evaluate the microscopic force between variable particles.

[0007] The technical solution adopted by the present invention to solve the technical problem is: the method for measuring the interaction force between oil droplets comprises the following steps:

[0008] Step 1: preparing produced water from ASP flooding to be tested, wherein the produced water from ASP flooding to be tested contains a crude oil droplet i to be tested, and using an atomic force microscope containing a probe to scan a microscopic surface area of ​​the produced water from ASP flooding in a tapping measurement mode to obtain a surface microscopic morphology of the produced water from ASP flooding to be tested, and determine the position of the crude oil droplet i to be tested;

[0009] Step 2: modify the probe, adhere the oil droplet ii to be tested on the probe, the probe is a nitride silica gel containing a micro cantilever, and according to the microscopic morphology of the crude oil droplet i to be tested, adopt a quantitative nanomechanical measurement mode, insert the needle into the center of each crude oil droplet i to be tested, and obtain the force curve between the crude oil droplet i to be tested and the oil droplet ii to be tested;

[0010] One end of a pair of micro-cantilevers that are extremely sensitive to weak forces in the modified probe is fixed, and the tiny needle tip at the other end is close to the sample. At this time, the probe needle tip interacts with the crude oil droplet i sample. The force will cause the micro-cantilever of the probe to deform when it contacts the surface of the crude oil droplet i. The micro-cantilever will deflect by δc, and a displacement Z will be generated between the fixed position of the micro-cantilever and the crude oil droplet i sample. The actual distance D between the probe needle tip and the crude oil droplet i sample is related to the sample deformation δ s The relationship between the formula D = Z-(δ s +δ c )calculate;

[0011] The force F between the probe tip and the atoms of the crude oil droplet i sample will be transmitted to the cantilever of the probe and amplified. The sensor is used to detect the deformation of the surface of the crude oil droplet i sample to obtain the surface force distribution information of the crude oil droplet i to be tested. The force between the probe tip and the crude oil droplet i to be tested conforms to Hooke's law F = -K c δ c , K C is the stiffness coefficient of the microcantilever;

[0012] Step 3: Under the high salt condition of salinity>1 mol / L NaCl, the double electrical layer repulsion is shielded, and steps 1 to 2 are repeated to obtain the force curve between the crude oil droplet i and the oil droplet ii to be tested;

[0013] Step 4: Based on the force curves obtained in step 2 and step 3, Nanoscope Analysis software is used to obtain the microscopic surface force type results of the crude oil droplet i and the crude oil droplet ii to be tested within a unit area.

[0014] The specific method of step one in the above scheme is:

[0015] ① After turning on the computer host monitor connected to the atomic force microscope cable, the light source and the controller are turned on, and the extremely weak interaction force between atoms on the surface of the crude oil droplet to be tested and a micro force sensitive element is imaged in the atomic force microscope system to obtain the surface microscopic morphology of the material;

[0016] ② Bond the mica sheet and the iron sheet to obtain a measurement substrate, take 1-10 drops of the ternary composite flooding produced aqueous solution and cover it on the mica sheet by spin coating for 10-30 minutes to obtain the crude oil droplet i sample, and then place the crude oil droplet i sample on the sample stage with magnetic force of the atomic force microscope;

[0017] ③ Place the probe in the liquid pool probe clamp, install the O-type rubber ring into the groove at the bottom of the liquid pool, and place it on the atomic force microscope. The O-type rubber ring and the crude oil droplet i sample form a stable closed space;

[0018] ④ Start Nanoscope software in the computer, select the tapping measurement mode of the atomic force microscope, set the scanning range according to the particle size range of the crude oil droplet i to be tested, scan the crude oil droplet i sample, obtain the microscopic morphology of the produced water of the ternary composite flooding to be tested, and determine the position of the crude oil droplet i to be tested.

[0019] In the above scheme, a probe with a small elastic constant suitable for soft particles is selected for measurement according to the texture of the crude oil droplet i sample, and the probe is selected from one of the ScanAsyst, Tap150A, P / N MPP-12120-10, and NPG-10 model probes.

[0020] In the above scheme, the probe is modified by using a drug to simulate the oil droplet ii to be detected, and the drug is selected from 1,10-decanedialkyl mercaptan, n-dodecyl mercaptan, and n-heptyl mercaptan.

[0021] The probe in the above scheme is NPG-10 probe. The method for modifying the probe is as follows: the NPG-10 probe is immersed in a liquid having a weight concentration of 2×10 3 The probe was placed in a 100 g / mL dodecyl mercaptan / anhydrous ethanol solution, taken out after 12 hours, washed with anhydrous ethanol, and then dried with high-purity nitrogen to obtain a probe containing the oil droplet ii to be tested.

[0022] The force measurement mode of the atomic force microscope in the above scheme is Peak Force QNM.

[0023] In step 2 of the above scheme, the PeakForce Setpoint is adjusted according to the characteristics of the crude oil droplet i sample until the force curve is correct.

[0024] In the above scheme, the probe force measurement process has a needle raising and lowering speed of 0-0.2 μm / s and a scanning range of 0-20 μm.

[0025] The scanning range in the above scheme is 0-5 μm.

[0026] The method for shielding the double electric layer repulsion in step three of the above scheme is: adding NaCl to the produced water containing the ASP flooding to be tested prepared in step one, wherein the mass content of NaCl is 71%.

[0027] The present invention has the following beneficial effects:

[0028] 1. The present invention uses an atomic force microscope to quantitatively characterize the force between two oil droplets under original formation conditions and under high mineralization shielding electrostatic repulsion conditions. For crude oil droplets, especially microscopic deformable droplets in a dispersed system, the method provided by the present invention can intuitively reflect the type and mechanism of the dynamic force between the oil droplets.

[0029] 2. The method provided by the present invention can explain the interaction force in the process of oil droplet aggregation from a microscopic perspective, laying a solid theoretical foundation for the research, development and application of ternary composite flooding water treatment technology. Description of the drawings:

[0030] Figure 1 It is a schematic diagram of the interaction mode between the probe and the sample containing the crude oil droplet ii during the measurement process according to the embodiment of the present invention;

[0031] Figure 2 is a relationship curve between the sum of the forces obtained in the measurement process of the present invention and the distance between the probe containing the crude oil droplet ii and the crude oil droplet i sample;

[0032] Figure 3 is a curve showing the relationship between the van der Waals attraction obtained under the condition of shielding electrostatic repulsion and the distance between the probe containing the crude oil droplet ii and the crude oil droplet i sample in the measurement process of the present invention in the embodiment;

[0033] Description of Reference Numerals

[0034] 1 ASP flooding produced water, 2 O-shaped rubber ring, 3 probe, 4 oil drop to be measured ii, 5 crude oil drop in ASP flooding produced water i, 6 measurement substrate obtained by bonding mica sheet and iron sheet. Specific implementation method:

[0035] The present invention will be further described below in conjunction with the accompanying drawings:

[0036] The method for measuring the interaction force between oil droplets is as follows:

[0037] (1) Prepare ASP flooding produced water to be tested containing crude oil droplets i, and use an atomic force microscope containing a probe to scan the microscopic surface area of ​​the ASP flooding produced water in a tapping measurement mode to obtain the microscopic morphology of the ASP flooding produced water to be tested, and determine the position of the crude oil droplets i to be tested.

[0038] The preparation method of ASP flooding produced water containing the crude oil droplet i to be tested is as follows:

[0039] In the presence of a solvent, a polymer, a surfactant, an alkali and crude oil are contacted and reacted to obtain the ternary composite flooding produced water containing crude oil droplets i, wherein the amount of the solvent is 30%, the amount of the polymer is 15%, the amount of the surfactant is 12%, the amount of the alkali is 13%, and the weight of the crude oil is 30%.

[0040] The polymer is selected from nonionic polyacrylamide powder, anionic polyacrylamide powder, and cationic polyacrylamide powder. In this embodiment, the polymer is anionic polyacrylamide powder; the surfactant is selected from alkylbenzene sulfonate, sodium dodecyl sulfate, petroleum sulfonate, OP-10 and other surfactants. In this embodiment, the surfactant is alkylbenzene sulfonate; the alkali is selected from Na2CO3, Na2SiO4, and NaOH. In this embodiment, the polymer is NaOH; the crude oil is selected from the crude oil exported from the test area; the solvent is simulated formation water. In this embodiment, the simulated formation water is a mixed solution containing NaCl, CaCl2, and MgCl2. Based on the total weight of the simulated formation water solute, the content of NaCl is 29%, the content of CaCl2 is 13%, and the content of MgCl2 is 8%.

[0041] (2) The oil droplet ii to be tested is adhered to a nitride colloidal probe containing a microcantilever to modify the probe, and according to the microscopic morphology of the crude oil droplet i to be tested, a quantitative nanomechanical measurement mode is used to insert a needle into the center of each spherical oil droplet i to obtain the force curve between the oil droplet i to be tested and the oil droplet ii to be tested. The method of adhering the oil droplet ii to be tested to the nitride colloidal probe containing a microcantilever is:

[0042] The gold-plated probe with linear alkane modified on the surface is used to simulate the crude oil drop to be tested ii. The chemical used to modify the probe is preferably selected from 1,10-decanedialkyl mercaptan, n-dodecyl mercaptan, and n-heptyl mercaptan. In this embodiment, the chemical used to modify the linear alkane on the gold-plated probe is n-dodecyl mercaptan / anhydrous ethanol solution.

[0043] (3) Under high salt conditions (mineralization> 1 mol / L NaCl), the double layer repulsion is shielded, and steps 1 to 2 are repeated to obtain the force curve between the oil droplet i to be tested and the oil droplet ii to be tested. The method of setting high salt conditions to shield the double layer repulsion is:

[0044] NaCl is added to the produced water containing the crude oil droplets to be tested prepared in step (1) and the content of NaCl is 71%.

[0045] The probe, force mode, needle lifting and lowering speed and scanning range described in step (3) are all consistent with those in step (2).

[0046] (4) According to each of the force curves, the Nanoscope Analysis software is used to obtain the force type results of the microscopic surfaces of the oil droplets i and ii in a unit area. The file used to obtain the force type of the microscopic surfaces of the oil droplets i and ii in a unit area is preferably selected from the pfc file, bin file, and spm file of each of the force curves.

[0047] The present invention has no special requirements for the calibration method of the elastic coefficient of the modified probe cantilever containing crude oil droplets ii, and those skilled in the art can select the method in combination with the techniques known in the art.

[0048] The probe model is selected from ScanAsyst, Tap150A, P / N MPP-12120-10, NPG-10, and in this embodiment, it is NPG-10.

[0049] The force measurement mode of the atomic force microscope is Peak Force QNM, the needle raising and lowering speed during the force measurement process is 0-0.2 μm / s, and the scanning range is 0-20 μm. In this embodiment, the scanning range is 0-5 μm.

[0050] Combination Figure 1 The present invention is described as follows:

[0051] A mica sheet and an iron sheet are bonded together to obtain a measuring substrate 6, 1-10 drops of crude oil droplets i to be tested (crude oil droplets i 5 in the produced water of ternary composite flooding) are taken and covered on the measuring substrate 6 with ternary composite flooding produced water 1, and then spin-coated for 10-30 minutes, and then placed on a sample stage with a magnetic force of an atomic force microscope; a probe 4 containing a probe cantilever 3 and a modified probe needle tip that can be used to simulate the crude oil droplets ii is placed in a liquid pool probe clamp, and an O-type rubber ring 2 is placed in the lower part of the liquid pool to make the crude oil droplets i to be tested and the crude oil droplets ii to be tested be in a stable closed space before starting measurement.

[0052] The present invention will be described in detail below by way of examples. In the following examples, all raw materials used are commercially available products and are analytically pure unless otherwise specified.

[0053] Polymer: Anionic partially hydrolyzed polyacrylamide powder: brand JX-12, purchased from Daqing Oilfield Production Engineering Research Institute; Surfactant: Alkylbenzene sulfonate: brand ORS-41, purchased from Daqing Oilfield Production Plant No. 1; Alkali: NaOH: brand NH-a21, purchased from Daqing Oilfield Production Engineering Research Institute; Dodecyl mercaptan: brand WJ-z12, purchased from Daqing Oilfield Production Plant No. 1.

[0054] Atomic force microscope (AFM): Model is Multimode-8, manufactured by Bruker Instruments, USA.

[0055] Probe: Model is NPG-10, manufactured by Bruker Instruments, USA.

[0056] Example 1

[0057] This method measures the interaction force between oil droplets.

[0058] Preparation of the produced water containing crude oil droplets i from ASP flooding:

[0059] (1) Add 290 g of NaCl, 130 g of CaCl2, and 80 g of MgCl2 into a beaker containing 1 L of ultrapure water and mix well to obtain simulated formation water.

[0060] (2) In the presence of simulated formation water, polyacrylamide dry powder polymer, alkylbenzene sulfonate, NaOH, and crude oil are added into a beaker to obtain ASP flooding produced water containing crude oil droplets i, wherein the amounts of the simulated formation water i, the polyacrylamide dry powder polymer, the alkylbenzene sulfonate, the NaOH, and the crude oil are 300 g, 150 g, 130 g, 120 g, and 300 g, respectively;

[0061] The method for measuring the sum of the interaction forces between oil droplets comprises the following steps:

[0062] (1) An atomic force microscope with a probe of model NPG-10 is used to scan the microscopic surface area of ​​the produced water of the ASP flooding in a tapping mode, wherein the average particle size R of the crude oil droplet i to be tested is s =4.96 μm, a 32*32 matrix is ​​selected, and the scanning range is set to 0-5 μm to obtain the microscopic morphology of the crude oil droplet i.

[0063] (2) The NPG-10 probe was immersed in a solution with a weight concentration of 2×10 3 The probe was placed in the dodecyl mercaptan / anhydrous ethanol solution of 50 g / mL, taken out after 12 hours, washed with anhydrous ethanol, and then dried with high-purity nitrogen to obtain a probe containing crude oil droplets ii.

[0064] (3) using an atomic force microscope with a probe of model NPG-10 containing a crude oil droplet ii to scan the microscopic surface area of ​​the crude oil droplet i to be measured in a quantitative nanomechanical measurement mode to obtain a force curve between the crude oil droplet i and the probe containing the crude oil droplet ii,

[0065] Figure 2 is the force curve of crude oil droplet i and oil droplet ii obtained in Example 1 under the preferred case of the present invention, Figure 2 It can be seen that there is both van der Waals attraction and repulsion induced by electrostatic effect between the two oil droplets.

[0066] The method for measuring the van der Waals attraction between oil droplets comprises the following steps:

[0067] (1) Add 290 g of NaCl to the produced water of the ASP flooding containing the crude oil droplets to be tested prepared in step (1).

[0068] (2) An atomic force microscope with a probe of model NPG-10 is used to scan the microscopic surface area of ​​the produced water of the ASP flooding in a tapping mode, wherein the average particle size R of the crude oil droplet i to be tested is s =4.96 μm, a 32*32 matrix is ​​selected, and the scanning range is set to 0-5 μm to obtain the microscopic morphology of the crude oil droplet i.

[0069] (3) The NPG-10 probe was immersed in a solution with a weight concentration of 2×10 3 The probe was placed in the dodecyl mercaptan / anhydrous ethanol solution of 50 g / mL, taken out after 12 hours, washed with anhydrous ethanol, and then dried with high-purity nitrogen to obtain a probe containing crude oil droplets ii.

[0070] (4) using an atomic force microscope with a probe of model NPG-10 containing a crude oil droplet ii to scan the microscopic surface area of ​​the crude oil droplet i to be measured in a quantitative nanomechanical measurement mode to obtain a van der Waals attraction curve between the oil droplet i and the probe containing the oil droplet ii,

[0071] Figure 3 is the van der Waals attraction curve between crude oil droplet i and oil droplet ii obtained in Example 1 under the preferred case of the present invention, Figure 2 It can be seen that the high ion concentration of the solution under high salinity conditions will cause the diffuse double layer to shrink, thus shielding the electrostatic effect in the measurement system.

[0072] According to the force curve, the spm file is selected and the Nanoscope Analysis software is used to obtain the microscopic surface force of the oil droplet i and the oil droplet ii in the unit area, wherein the van der Waals attraction between the crude oil droplet i and the oil droplet ii is 1.684N. The double layer repulsion is 0.0648N.

[0073] It can be seen from the above results that the method provided by the present invention can measure the interaction force between oil droplets and intuitively reflect the type and mechanism of the dynamic interaction force between oil droplets.

[0074] The method provided by the present invention can explain the interaction force in the oil droplet aggregation process from a microscopic perspective, laying a solid theoretical foundation for the research, development and application of ternary composite flooding water treatment technology.

[0075] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for measuring the interaction force between oil droplets, characterized in that: The force between two oil droplets is quantitatively characterized under the original formation conditions and under the condition of high salinity shielding electrostatic repulsion, which specifically includes the following steps: Step 1: Prepare the produced water from the ASP flooding to be tested, the produced water from the ASP flooding to be tested contains the crude oil droplet i to be tested, and use an atomic force microscope containing a probe to scan the microscopic surface area of ​​the produced water from the ASP flooding to be tested in a tapping measurement mode to obtain the surface microscopic morphology of the produced water from the ASP flooding to be tested, and determine the position of the crude oil droplet i to be tested, specifically: ① After turning on the computer host monitor connected to the atomic force microscope cable, the light source and the controller are turned on, and the extremely weak interaction force between atoms on the surface of the crude oil droplet to be tested and a micro force sensitive element is imaged in the atomic force microscope system to obtain the surface microscopic morphology of the material; ② Bond the mica sheet and the iron sheet to obtain a measurement substrate, take 1-10 drops of the ternary composite flooding produced aqueous solution and cover it on the mica sheet by spin coating for 10-30 minutes to obtain the crude oil droplet i sample, and then place the crude oil droplet i sample on the sample stage with magnetic force of the atomic force microscope; ③ Place the probe in the liquid pool probe clamp, install the O-type rubber ring into the groove at the bottom of the liquid pool, and place it on the atomic force microscope. The O-type rubber ring and the crude oil droplet i sample form a stable closed space; ④ Start the Nanoscope software in the computer, select the tapping measurement mode of the atomic force microscope, set the scanning range according to the particle size range of the crude oil droplet i to be tested, scan the crude oil droplet i sample, obtain the microscopic morphology of the produced water of the ternary composite flooding to be tested, and determine the position of the crude oil droplet i to be tested; Step 2: modify the probe, adhere the oil droplet ii to be tested on the probe, the probe is a nitride silica gel containing a micro cantilever, and according to the microscopic morphology of the crude oil droplet i to be tested, adopt a quantitative nanomechanical measurement mode, insert the needle into the center of each crude oil droplet i to be tested, and obtain the force curve between the crude oil droplet i to be tested and the oil droplet ii to be tested; The probe force measurement process has a needle raising and lowering speed of 0-0.2 μm / s and a scanning range of 0-20 μm; One end of a pair of extremely sensitive micro-cantilevers in the modified probe is fixed, and the tiny needle tip at the other end is close to the sample. At this time, the probe needle tip interacts with the crude oil droplet i sample, and the force will cause the micro-cantilever of the probe to deform when it contacts the surface of the crude oil droplet i, and the micro-cantilever will The displacement between the fixed position of the microcantilever and the crude oil droplet i sample is Z ; The actual distance between the probe tip and the crude oil droplet i sample D and sample shape δ s The relationship between D = Z -( δ s + δ c )calculate; The force between the probe tip and the sample atoms in the crude oil droplet F The force is transmitted to the cantilever of the probe and amplified. The deformation of the surface of the crude oil droplet i is detected by the sensor to obtain the surface force distribution information of the crude oil droplet i to be tested. The force between the probe tip and the crude oil droplet i to be tested conforms to Hooke's law. F =- K c δ c , K C is the stiffness coefficient of the microcantilever; Step 3: Under the high salt condition of salinity>1 mol / L NaCl, the double electrical layer repulsion is shielded, and steps 1 to 2 are repeated to obtain the force curve between the crude oil droplet i and the oil droplet ii to be tested; Step 4: Based on the force curves obtained in step 2 and step 3, Nanoscope Analysis software is used to obtain the microscopic surface force type results of the crude oil droplet i and the crude oil droplet ii to be tested within a unit area.

2. The method for measuring the interaction force between oil droplets according to claim 1, characterized in that: According to the texture of the crude oil droplet i sample, a probe with a smaller elastic constant suitable for soft particles is selected for measurement, and the probe is selected from one of ScanAsyst, Tap150A, P / N MPP-12120-10, and NPG-10 model probes.

3. The method for measuring the interaction force between oil droplets according to claim 2, characterized in that: The probe is modified by using a drug to modify the probe to simulate the oil droplet ii to be detected, and the drug is selected from 1,10-decanedialkyl mercaptan, n-dodecyl mercaptan, and n-heptyl mercaptan.

4. The method for measuring the interaction force between oil droplets according to claim 3, characterized in that: The method for shielding the double electric layer repulsion in step three is: adding NaCl to the produced water containing the ASP flooding to be tested prepared in step one, wherein the mass content of NaCl is 71%.

5. The method for measuring the interaction force between oil droplets according to claim 4, characterized in that: The force measurement mode of the atomic force microscope is Peak Force QNM. In the step 2, the PeakForce Setpoint is adjusted according to the characteristics of the crude oil droplet i sample until the force curve is correct.

6. The method for measuring the interaction force between oil droplets according to claim 5, characterized in that: The scanning range is 0-5 μm.

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