Carbonate rock-based super-hydrophobic slippage mechanism measurement method

Abstract

The invention discloses a super-hydrophobic slippage mechanism measuring method based on carbonate rocks, and belongs to the field of oil and gas field development. The method comprises the following steps: firstly, preparing super-hydrophobic nano silicon dioxide particles by an infiltration method, and then carrying out synergistic modification on a carbonate rock core by utilizing the particles and a polysiloxane solution to obtain a super-hydrophobic carbonate rock sample. The method is characterized in that a rough surface contact mode interface boundary slippage theoretical measurement model is constructed, an atomic force microscope is utilized to measure a submerged force curve, and the curve is substituted into the model to quantitatively calculate the boundary slippage distance b of the rock core interface. According to the method, the super-hydrophobic modification effect is associated with a quantifiable slippage parameter b for the first time, the adsorption and retention capacity of water on the surface of a rock core is effectively weakened, and finally the purposes of inhibiting water invasion of a gas reservoir, guaranteeing stable output of gas and improving the recovery ratio are achieved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development, and in particular to a method for measuring the superhydrophobic slip mechanism based on carbonate rocks. Background Technology

[0002] Currently, international gas field development mainly focuses on large pure gas reservoirs and weak water reservoirs, with relatively little investment in research on water-driven gas reservoirs. In my country, however, water-driven gas reservoirs account for a large proportion, with approximately 40% to 50% of these reservoirs having active edge and bottom water, directly resulting in low recovery rates of only 31% to 40%. With the increasing number of gas-water co-producing wells, water management issues are becoming increasingly prominent, exacerbating the "water disaster" problem. Effective water control has become a critical issue that urgently needs to be addressed in ensuring stable gas production. Edge and bottom water in gas reservoirs have a dual nature: on the one hand, it is the driving force for gas displacement; on the other hand, it is also the source of water intrusion. As development progresses, reservoir pressure decreases, and edge and bottom water intrudes into the gas-bearing area, forming a water intrusion zone, which in turn reduces gas phase permeability and adversely affects overall production. Carbonate reservoirs, due to their strong heterogeneity, face a higher risk of water intrusion, exhibiting a significant water-sealing effect. This not only limits recovery rates (to only 40% to 60%, far lower than the 80% to 95% of pure gas reservoirs), but also reduces economic efficiency, increases operating costs, and poses a challenge to the long-term sustainable development of gas reservoirs.

[0003] In carbonate gas reservoirs, both micro-fractures and large fractures significantly impact fluid flow. Micro-fractures are widely distributed in the formation, tightly connected to pores, forming fluid seepage channels and facilitating fluid exchange between pores. Large fractures are fewer in number and unevenly distributed, extending from several meters to several kilometers. Fluid flow in these large fractures is high-speed non-Darcy flow, exceeding the range of conventional Darcy flow. After a water-producing gas well is put into production, the resulting pressure drop propagates rapidly along the large fractures connected to edge and bottom water, causing formation water to rush into the well bottom through these fractures, resulting in "fracture water channeling." This phenomenon accelerates formation water intrusion, severely impacting stable well production and the overall reservoir development strategy. Water control technology is crucial in oil and gas field development, significantly contributing to improved reservoir recovery and extended well production duration. With the continuous exploitation of oil and gas resources, the management and control of water-producing gas reservoirs are receiving increasing attention from the industry. This technology, utilizing scientific methods and advanced technology, effectively curbs reservoir water intrusion, thereby improving the overall development efficiency of the gas reservoir. Summary of the Invention

[0004] To address the lack of effective means in existing technologies to quantitatively characterize the effects of superhydrophobic modification on carbonate rocks, and the problem of how to directly link the modification effects with the improvement of water recovery in gas reservoirs, this invention provides a measurement method aimed at quantitatively characterizing the interfacial slip capacity of superhydrophobic carbonate rocks, providing key parameters for evaluating the modification effects and predicting water control effectiveness.

[0005] The technical solution of the present invention:

[0006] A method for measuring the superhydrophobic slip mechanism based on carbonate rocks, comprising:

[0007] Preparation of superhydrophobic nano-silica particles;

[0008] Superhydrophobic modification was performed on carbonate rock cores to obtain superhydrophobic carbonate rock samples;

[0009] A theoretical measurement model for interface boundary slip in rough surface contact mode was constructed based on superhydrophobic nano-silica particles and superhydrophobic carbonate rock samples.

[0010] Substituting the force curve of the underwater model obtained by atomic force microscopy into the model, the boundary slip distance b of the superhydrophobic carbonate rock interface was calculated.

[0011] Further, the preparation of superhydrophobic nano-silica particles includes:

[0012] Nano-silica was placed in a prepared organic solution and ultrasonically dispersed for 20 minutes to obtain a nano-silica suspension.

[0013] The nano-silica suspension was stirred at 3000 r / min for 20 minutes to obtain a homogenized nano-silica suspension.

[0014] The homogenized nano silica suspension was placed in an environment of 75°C and surface modified with alkylsilane at a concentration of 3wt% for 12 hours to obtain alkylsilane modified silica nanoparticles.

[0015] Alkylsilane-modified silica nanoparticles were washed sequentially with deionized water and anhydrous ethanol, centrifuged, dried at 60°C, and then ground into powder to obtain superhydrophobic silica nanoparticles.

[0016] Furthermore, the prepared organic solution is a mixed solution of dimethylformamide and tetrahydrofuran in a volume ratio of 7:3.

[0017] Furthermore, the mass fraction of the nano-silica in the prepared organic solution is 30%.

[0018] Furthermore, the superhydrophobic modification of the carbonate rock core to obtain a superhydrophobic carbonate rock sample includes:

[0019] Prepare a polysiloxane solution with a concentration of 2.5 mg / L, and stir until completely dissolved;

[0020] Carbonate rock core slices were placed in a mixed solution of dissolved polysiloxane solution and 30% by mass of superhydrophobic nano silica particles, and modified at 120°C for 6 hours to obtain carbonate rock cores with preliminary surface modification.

[0021] The carbonate rock core with preliminary surface modification was dried at 60℃ for 12 hours to obtain a superhydrophobic carbonate rock sample.

[0022] Furthermore, the measurement model for interface boundary slip in rough surface contact mode includes:

[0023] Establish a theoretical coordinate system and interface geometric model, set boundary conditions and initial parameters, and complete the construction of the theoretical framework;

[0024] Based on the Navier-Stokes equations and the fluid momentum equations, the fluid control equations are derived and the Navier boundary slip condition is defined, resulting in a set of theoretical equations that include the slip distance b.

[0025] Solving the fluid velocity and pressure distribution functions in the theoretical equations yields a mathematical description of the fluid dynamics behavior.

[0026] The fluid force is calculated by integrating the fluid pressure distribution function, and experimental measurement parameters from atomic force microscopy are introduced to establish a correlation model between the fluid force and the experimental observations.

[0027] Furthermore, the atomic force microscope (AFM) probe measures the model force curves underwater, including:

[0028] Microspheres were cleaned in an ultrasonic cleaner using acetone and methanol solutions, then allowed to stand at room temperature. The microspheres were then precisely bonded to the end of an atomic force microscope probe using epoxy resin adhesive to obtain a microsphere-modified colloidal probe.

[0029] The modified carbonate rock sample was fixed on the sample stage, and the colloidal probe was installed using a polychlorotrifluoroethylene underwater probe holder. Real-time monitoring was performed using reflected laser light.

[0030] Test liquid is dripped between the liquid holder and the sample to form a stable crescent-shaped droplet, ensuring continuous liquid contact between the holder and the superhydrophobic core interface.

[0031] Use a pipette to add 100 μL of test liquid to the interface of the sample under test, and at the same time add a drop of 20 μL of liquid to the probe of the atomic force microscope. Then drive the probe close to the sample interface and measure the relationship curve between the cantilever deformation and the separation distance under the liquid.

[0032] Based on the elastic stiffness of the probe cantilever, the cantilever deformation is converted into force to obtain the force curve of the underwater model.

[0033] Furthermore, the carbonate rock comprises single-material calcite, dolomite, or a mixture of calcite and dolomite.

[0034] The beneficial effects of this invention are:

[0035] This invention is the first to correlate the superhydrophobic modification effect with a quantifiable slip parameter b. Through rigorous theoretical models and precise experimental measurements, it achieves a quantitative evaluation of the interface properties of superhydrophobic carbonate rocks. This method can effectively assess the effect of modification processes on reducing the adsorption and retention capacity of water on the core surface, providing a scientific basis and data support for optimizing water control processes in gas reservoirs, suppressing water intrusion, ensuring stable gas production, and improving oil recovery. Attached Figure Description

[0036] Figure 1 This is a logic flowchart of the measurement method of the present invention;

[0037] Figure 2 A schematic diagram and a contact angle curve are provided for calculating the contact angle using the tangent method.

[0038] Figure 3 The contact angle curve of the superhydrophobic carbonate rock core surface;

[0039] Figure 4 The superhydrophobic carbonate rock core indicates the boundary slip distance;

[0040] Figure 5 The image shows the rolling state of a droplet after modification with 2.50 mg / L polysiloxane solution and 30% superhydrophobic nanoparticles.

[0041] Figure 6 Schematic diagram of the principle of measuring the slip distance of superhydrophobic boundaries in carbonate rocks;

[0042] Figure 7 This refers to the unmodified interface morphology of the carbonate rock core and the plane height difference in the X and Y directions.

[0043] Figure 8 The interface morphology and the height difference in the X and Y directions of the carbonate rock core interface after modification with superhydrophobic nanoparticles are shown.

[0044] Figure 9 This represents the slip distance at the interface of the carbonate rock core after superhydrophobic modification. Detailed Implementation

[0045] The following is in conjunction with the appendix Figures 1-9 The embodiments of the present invention will be further described.

[0046] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. In the examples described below, alkylsilanes were provided by Xuanhao New Materials Technology Co., Ltd., dimethylformamide (DMF) by Suzhou Senfida Chemical Co., Ltd., tetrahydrofuran (THF) by Chengdu Kelong Chemical Co., Ltd., and polysiloxane (PD) by Wanhua Chemical Group Co., Ltd.

[0047] In this invention, the wetting contact angle of the modified surface is measured and verified to be greater than 150° using the tangent method. The purpose is not only to qualitatively confirm the superhydrophobic properties of the surface, but also to provide a crucial physical premise and logical foundation for subsequent boundary slip theory models and measurements. The core theoretical model of this invention—the rough surface contact mode interface boundary slip theory measurement model—is based on the Navier boundary slip condition. This condition describes that at the solid-liquid interface, the fluid velocity is no longer zero, but is proportional to the local shear stress, with the proportionality coefficient relating to the slip distance b. Therefore, the measured high contact angle (>150°) is direct experimental evidence that the surface has successfully constructed a gas-liquid-solid composite interface capable of producing a slip effect. It ensures that the force curves measured using AFM are obtained at an interface with a significant slip effect.

[0048] Example

[0049] First, superhydrophobic nano-silica particles are prepared, including: placing nano-silica in a prepared organic solution, wherein the organic solution is a mixture of dimethylformamide and tetrahydrofuran with a volume ratio of 7:3, and the mass fraction of nano-silica in the prepared organic solution is 30%. The nano-silica is ultrasonically dispersed for 20 minutes to obtain a nano-silica suspension; the nano-silica suspension is stirred at 3000 r / min for 20 minutes to obtain a homogenized nano-silica suspension; the homogenized nano-silica suspension is placed in a 75℃ environment and surface modified with a 3wt% alkylsilane for 12 hours to obtain alkylsilane-modified silica nanoparticles; the alkylsilane-modified silica nanoparticles are washed sequentially with deionized water and anhydrous ethanol, centrifuged, dried at 60℃, and then ground into powder to obtain superhydrophobic nano-silica particles.

[0050] Specifically, a 7:3 organic solution of dimethylformamide (DMF) / tetrahydrofuran (THF) was prepared, and silane coupling agent solutions were prepared using DMF / THF at concentrations of 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%. The coupling agent solutions of different concentrations were first dissolved in anhydrous ethanol and mixed, then placed in 50 mL beakers and sonicated at room temperature for 30 min to ensure homogeneity. Neutral nano-SiO2 was then placed in 10 mL of silane coupling agent solutions of different concentrations. The nano-SiO2 was ultrasonically dispersed in the solvent for 10-30 min, with a mass concentration of 0-30%. It was then uniformly stirred at 3000 r / min using a digital display high-speed stirrer for 20 min and placed in a 75℃ electric heating drying oven for 12 h for modification. After the reaction, the supernatant was discarded, and the nano-SiO2 was washed several times with deionized water and anhydrous ethanol. The nano-SiO2 was then centrifuged at high speed using a benchtop centrifuge, dried in an electric heating drying oven at 40-60℃, and finally ground into powder using a mortar and pestle for later use. The superhydrophobicity of the prepared nano-silica powder was then verified: a grooved quartz slide was ultrasonically cleaned in toluene and methanol for 25-50 minutes, followed by multiple rinsings with deionized water, and finally dried in an oven at 40-60°C. A certain amount of nano-SiO2 powder was placed in the groove of the slide, and the nano-SiO2 was pressed with a glass slide for 10-30 minutes. Then, the contact angle measuring instrument was turned on, the camera light source was adjusted so that the slide was positioned in the display area of ​​the testing software, and the density and related parameters of the deionized water and the measured nano-SiO2 were set to be measured. The micro-pump speed was set to 1 μL / s. The interface between deionized water and modified nano-SiO2 was dropped for 5 seconds. After the droplet stabilized for 5 minutes, the state of the droplet was quickly photographed and recorded using DSA3 software. The wetting contact angle of the droplet was then measured using the tangent method. The measured contact angle was greater than 150°, confirming its superhydrophobic properties.

[0051] Superhydrophobic modification of carbonate rock cores was performed to obtain superhydrophobic carbonate rock samples. The process included: preparing a 2.5 mg / L polysiloxane solution and stirring until completely dissolved; placing thin slices of carbonate rock core into a mixed solution of the dissolved polysiloxane solution and 30% by mass superhydrophobic nano-silica particles, and modifying the solution at 120°C for 6 hours to obtain a carbonate rock core with preliminary surface modification; and drying the carbonate rock core with preliminary surface modification at 60°C for 12 hours to obtain a superhydrophobic carbonate rock sample.

[0052] Specifically, a 2.5 mg / L polysiloxane solution was stirred at 50–75 °C for 6 hours with a digital display stirrer until completely dissolved. Self-made modified 0–30% superhydrophobic nano-SiO2 was dispersed in the polysiloxane PD solution. Self-made core slices with different proportions were placed in the polysiloxane PD solution for interface modification at 120 °C for 6 hours. After modification, the core slices were washed several times with anhydrous ethanol and dried in an electric heating oven at 40–60 °C for 12 hours. The superhydrophobic modification effect was then verified: an SDC-350 contact angle meter was used to measure the angle using a 5 μL deionized water droplet at room temperature via the seated drop method. The average of five measurements for all samples was recorded as the liquid-solid contact angle. The roll-off angle, denoted by α, is the critical angle formed between the inclined interface and the horizontal plane when the droplet just begins to roll on the inclined interface.

[0053] By constructing a theoretical measurement model of interface boundary slip in rough surface contact mode, the following steps are taken: establishing a theoretical coordinate system and interface geometric model, setting boundary conditions and initial parameters, and completing the theoretical framework; deriving the fluid control equations and defining the Navier boundary slip condition based on the Navier-Stokes equations and fluid momentum equations, obtaining a set of theoretical equations including the slip distance b; solving the fluid velocity and pressure distribution functions in the theoretical equations to obtain a mathematical description of the fluid dynamics behavior; integrating the fluid pressure distribution function to calculate the fluid force, and introducing atomic force microscopy experimental measurement parameters to establish a correlation model between the fluid force and experimental observations.

[0054] Specifically, the theoretical coordinate system and interface geometric model are first established, boundary conditions and initial parameters are set, and the theoretical framework is completed:

[0055] Establish a coordinate system where the w-axis represents the tangent direction of the W2 interface, and the z-axis is perpendicular to the W2 interface and passes through the center of the sphere in W1. The origin O of the coordinate system is located on the W2 interface. This setup helps to more accurately analyze and describe the hydrodynamic effects caused by liquid compression between the sphere and the rough interface.

[0056] In the region where the ball gradually approaches interface W2, interface W1 can be represented by a planar coordinate system, and the interface of the ball can be represented by a parabolic surface. The equation of interface W1 / W2 in the two-dimensional coordinate system (z, w) can be written as:

[0057] （1）

[0058] Where W1 represents rough interface 1; W2 represents rough interface 2; w represents the height change in the two-dimensional plane coordinate direction; z represents the z-direction coordinate; H represents the distance between the sphere and the plane; and R represents the radius of the glass sphere.

[0059] Based on the Navier-Stokes equations and the fluid momentum equations, the fluid control equations are derived and the Navier boundary slip condition is defined, resulting in a set of theoretical equations including the slip distance b:

[0060] Under steady-state conditions, the momentum equation for a fluid can be simplified to describe the relationship between internal pressure, viscous forces, and velocity gradient. Due to the thin fluid layer, the influence of viscous forces on fluid motion is particularly significant. Furthermore, due to V... z Much smaller than V x and V y Based on the Navier-Stokes equations and the momentum equation, the continuity equation for the fluid can be expressed as:

[0061] （2）

[0062] In the formula, p represents the pressure of the fluid between the two planes; μ represents the dynamic viscosity of the liquid; G represents the atmospheric pressure outside the plane and the fluid; T c Energy representing absolute temperature; R e V represents the Reynolds number, a dimensionless number used to characterize the viscous response of fluid flow; x V y and V z V represents the fluid velocity in the x, y, and z directions, respectively. w d represents the velocity of a two-dimensional planar fluid. t denoted by ; w represents the time derivative; represents the change in height along the two-dimensional plane coordinates; z represents the vertical coordinates.

[0063] In laminar flow, viscous forces play a dominant role in fluid motion; therefore, viscous forces cannot be ignored. On the contrary, their influence on fluid flow must be fully considered. Meanwhile, since the fluid layer is very thin, the effects of external atmospheric pressure and room temperature on the fluid layer's interior can be neglected, hence G=T. c =1 can be represented as:

[0064] （3）

[0065] Where P represents the pressure of the fluid between the two planes; w represents the height change along the two-dimensional plane coordinates; μ represents the dynamic viscosity of the liquid; V w denoted by z, which represents the velocity of a fluid in a two-dimensional plane; z represents the vertical coordinate.

[0066] The continuity equation for incompressible liquids is:

[0067] （4）

[0068] Where P represents the pressure of the fluid between the two planes; w represents the height change in the two-dimensional plane coordinate direction; V w This represents the velocity of a fluid in a two-dimensional plane.

[0069] The momentum equations in the w and z directions can be expressed as:

[0070] （5）

[0071] In the formula, ρ represents the density of the fluid; w represents the change in height along the two-dimensional plane coordinates; V w Represents the velocity of a two-dimensional planar fluid; z represents the vertical coordinate; V z The z-axis represents the fluid velocity; P represents the fluid pressure between the two planes.

[0072] Assume that both interfaces and the solid-liquid interface between the liquid and the interface are subject to Navier boundary slip conditions, and the boundary slip distance of the interface is b. The coefficients k and b take the following two values:

[0073] （6）

[0074] Where b represents the sliding distance; k represents the sliding adjustment coefficient.

[0075] It should be noted that when k=0, this condition corresponds to the ideal case of perfect slip or infinite slip distance. In practical applications, when the solid-liquid interface interaction is extremely weak, such as when a liquid advances on a superhydrophobic surface with a stable gas film, the interfacial resistance approaches zero, and this boundary condition can be approximated. It is usually used as the limiting case for theoretical analysis. In this invention, this condition is mainly used to verify the integrity of the theoretical model or as a benchmark to assess how close the slip performance of a real superhydrophobic surface is to the ideal state. This condition is not directly used when calculating the slip distance b of the modified core. When k=μ / b, it corresponds to the real physical scenario of partial slip, that is, the slip distance b is a finite, positive value to be determined. This accurately describes the actual slip behavior that occurs at the gas-liquid-solid composite interface when a liquid flows on a superhydrophobic surface with a microscopic or nanoscale rough structure. This is the only applicable condition in this invention for calculating the slip distance b of actual superhydrophobic carbonate rock samples. Since our goal is to measure this finite slip distance b, we must use this boundary condition to build a bridge between the theoretical model and the experimental data.

[0076] According to the Navier boundary slip model, the boundary condition of the solid-liquid interface W1 can be expressed as:

[0077] （7）

[0078] Where z represents the vertical coordinate; V z D represents the fluid velocity in the z-direction; h The distance between the glass sphere and the interface is represented by: w; the height variation in the two-dimensional plane coordinate direction is represented by: R; the radius of the glass sphere is represented by: V.w b represents the velocity of the fluid in the two-dimensional plane; k represents the slip distance; and b represents the slip adjustment coefficient.

[0079] The boundary condition of the rough solid-liquid interface W2 can be expressed as:

[0080] （8）

[0081] Among them, D h R represents the separation distance between the glass sphere and the interface; Z represents the vertical coordinate; V represents the vertical coordinate. z V represents the fluid velocity in the z-direction; w b represents the velocity of the fluid in a two-dimensional plane; b represents the slip distance.

[0082] Solving the fluid velocity and pressure distribution functions in the theoretical equations yields a mathematical description of the fluid dynamics behavior:

[0083] Substituting the boundary conditions (7) and (8) into the continuity equation (4) for the fluid between the two planes, the fluid velocity V w The expression is:

[0084] （9）

[0085] Where w represents the change in height along the two-dimensional plane coordinate direction; V w The value represents the velocity of the fluid in the two-dimensional plane; z represents the vertical coordinate; P represents the pressure of the fluid between the two planes; μ represents the dynamic viscosity of the liquid; H is the distance between the sphere and the plane; R represents the radius of the glass sphere; b represents the sliding distance; and k represents the sliding adjustment coefficient.

[0086] Furthermore, the expression for the boundary condition H of the solid-liquid interface W1 in the z-direction is:

[0087] （10）

[0088] Where w represents the change in height along the two-dimensional plane coordinates; R represents the radius of the glass sphere; D h This indicates the separation distance between the ball and the interface.

[0089] Substituting equation (9) into the continuity equation (4), we can obtain the relationship between the approach velocities V and z between the two interfaces as follows:

[0090] （11）

[0091] Where w represents the height change in the two-dimensional plane coordinate direction; P represents the pressure of the fluid between the two planes; μ represents the dynamic viscosity of the liquid; H represents the distance between the sphere and the plane; R represents the radius of the glass sphere; b represents the sliding distance; and k represents the sliding adjustment coefficient.

[0092] but:

[0093] （12）

[0094] Where μ represents the dynamic viscosity of the liquid; P represents the pressure of the fluid between the two planes; w represents the height change along the two-dimensional plane coordinates; V w This represents the velocity of a fluid in a two-dimensional plane. Furthermore, L can be specifically expressed by the formula:

[0095] （13）

[0096] Where w represents the height change in the two-dimensional plane coordinate direction; H represents the distance between the sphere and the plane; R represents the radius of the glass sphere; b represents the sliding distance; and k represents the sliding adjustment coefficient.

[0097] Because the flow field is axially symmetric along the z-axis, when w=0, d p / d w =0. Based on the previous assumption, p=0 when w→∞. The fluid pressure p can be expressed as:

[0098] （14）

[0099] Where P represents the pressure of the fluid between the two planes; μ represents the dynamic viscosity of the liquid; V represents the relative velocity between the colloidal probe and the core being tested; H represents the distance between the sphere and the plane; and R represents the radius of the glass sphere.

[0100] Specifically, p* can be represented as:

[0101] （15）

[0102] Furthermore, A', B', C', and D' can be expressed by formulas respectively:

[0103] （16）

[0104] Where H represents the distance between the small ball and the plane; R represents the radius of the glass ball; b represents the sliding distance; and k represents the sliding adjustment coefficient.

[0105] The fluid force is calculated using the integral fluid pressure distribution function, and experimental measurement parameters from atomic force microscopy are introduced to establish a correlation model between the fluid force and experimental observations.

[0106] As interface W1 approaches interface W2, the fluid forces F acting on interfaces W1 and W2 are equal in magnitude and opposite in direction. The fluid force F can be expressed as:

[0107] （17）

[0108] Where F represents fluid force; w represents the change in height along the two-dimensional plane coordinates; P represents the fluid pressure between the two planes; μ represents the dynamic viscosity of the liquid; V z R represents the velocity along the z-axis; V represents the radius of the glass sphere; V represents the relative velocity between the colloidal probe and the core sample; and H represents the distance between the sphere and the plane.

[0109] Furthermore, f* can be specifically represented as:

[0110] （18）

[0111] Colloidal probes in atomic force microscopy (AFM) typically use borosilicate glass microspheres as micrometer-scale contactors; some experiments also employ gold-plated borosilicate glass microspheres at the interface. When the slip distance of water at the borosilicate glass microsphere interface is almost zero, it indicates that the interaction between water molecules and the glass interface is very strong, and the fluid behavior at the interface is close to a no-slip state. In this case, the influence of the microsphere interface boundary conditions on the hydrodynamic measurement is usually ignored, and f* can thus be simplified to:

[0112] （19）

[0113] Substituting the physical quantities measured by atomic force microscopy (AFM) experiments directly into the theoretical model, we finally obtain the experimental general formula 20:

[0114] When the distance between the borosilicate glass microsphere and the interface is relatively large, interfacial forces such as electrostatic forces and van der Waals forces can usually be ignored. Under boundary slip conditions, using Hooke's law, the force on the borosilicate glass microsphere can be calculated from the deformation of the cantilever beam. The deformation D of the colloidal probe cantilever beam is... ef It can be represented as:

[0115] （20）

[0116] Where V represents the relative velocity between the colloidal probe and the core sample, in nm / s; R represents the radius of the borosilicate glass microsphere, in μm; F s The interfacial force on the colloidal probe is represented by nN; F represents the fluid force on the colloidal probe, nN; k represents the cantilever stiffness of the colloidal probe, N / m; μ represents the liquid viscosity, mPa·s; D k b represents the separation distance between the borosilicate glass microsphere and the interface under test, in nm; b represents the slip distance, in nm.

[0117] Formula (20) expresses the fluid force F as a function of the slip distance b.

[0118] The method for measuring the underwater model force curve using an atomic force microscope (AFM) probe includes: cleaning microspheres with acetone and methanol solution in an ultrasonic cleaner, then allowing them to stand at room temperature; precisely bonding the microspheres to the tail end of the AFM probe using epoxy resin to obtain a microsphere-modified colloidal probe; fixing the modified carbonate rock sample on the sample stage and installing the colloidal probe using a polychlorotrifluoroethylene (PTFE) underwater probe holder, with real-time monitoring via reflected laser; dripping test liquid between the liquid holder and the sample to form a stable crescent-shaped droplet, ensuring continuous liquid contact between the holder and the superhydrophobic core interface; adding 100 μL of test liquid to the sample interface using a pipette, while simultaneously dripping a 20 μL drop of liquid onto the AFM probe; then driving the probe close to the sample interface and measuring the relationship between the cantilever deformation and the separation distance; and finally, converting the cantilever deformation into a force based on the elastic stiffness of the probe cantilever to obtain the underwater model force curve.

[0119] It should be noted that although polychlorotrifluoroethylene is the preferred material for implementing the measurement method described in this invention, those skilled in the art will understand that any material that can simultaneously satisfy high chemical stability, low surface energy, good optical compatibility and high mechanical stiffness can be used as an alternative, such as polytetrafluoroethylene or specific grades of solvent-resistant engineering plastics.

[0120] Specifically, the microspheres were repeatedly cleaned 3-5 times in an ultrasonic cleaner using acetone and methanol solutions, then allowed to stand at room temperature for 4 hours. The microspheres were then precisely bonded to the probe tip using epoxy resin, resulting in a microsphere-modified colloidal probe. The modified carbonate rock sample was fixed on the sample stage, and the colloidal probe was mounted using a Bruker PVC underwater probe holder. Real-time monitoring was performed using a reflected laser. During the measurement process, the holder came into direct contact with various test liquids (deionized water, hexadecane, and ethylene glycol). PVC exhibits excellent chemical inertness to these liquids and to organic solvents such as acetone and methanol used for cleaning. This ensures that the holder does not swell, deform, or degrade during the experiment, thus maintaining the stability of the holder's geometry. This geometric stability is the physical basis for the formation and maintenance of a "stable crescent-shaped droplet." Between the liquid holder and the sample, drop 10–20 μL of liquid until an axisymmetric meniscus is formed between the droplet and the sample surface, ensuring continuous liquid contact between the holder and the superhydrophobic core interface. After adding the liquid, allow it to stand for at least 60–120 seconds. This time allows the initial flow and vibrations generated during the droplet addition to decay sufficiently, and allows the system (liquid-holder-sample) to reach thermal equilibrium, reducing the effects of thermal drift. Using a pipette, add 100 μL of liquid to the sample interface and approximately 20 μL to the AFM probe. Using an AFM in the liquid environment, directly measure and record the raw data relationship between the cantilever deformation (force) and the probe position (distance) as the probe approaches / moves away from the sample surface, obtaining the raw force-distance curve and acquiring the fluid force F and separation distance D. k The relative velocity of the probe is V. The deformation of the cantilever is D. ef The vertical axis directly corresponds to the original curve, i.e., the probe bending degree measured by AFM through laser reflection; separation distance D k The horizontal axis corresponds to the original curve, representing the distance between the probe and the sample interface recorded in real-time by AFM; the probe relative velocity V is a preset experimental parameter during the acquisition of the original curve; the fluid force F is based on the D of the original curve. ef The value was calculated using Hooke's Law. Subsequently, the probe was driven close to the sample interface, and the relationship between the cantilever deformation and the separation distance under the liquid was measured. The V / F curve was calculated using the fluid force F, and the slope k1 and intercept m were obtained by fitting the V / F curve. Based on the elastic stiffness of the probe cantilever, the cantilever deformation was converted into a force, yielding the underwater model force curve.

[0121] (twenty one)

[0122] Where b represents the sliding distance, nm; V represents the probe approach velocity, μm / s; k represents the probe stiffness, N / m; μ represents the liquid viscosity, mPa∙s; R represents the glass sphere radius, μm; k1 represents the slope, dimensionless; and m represents the intercept, dimensionless.

[0123] The experimental parameters were set as follows: probe approach velocity V = 38.5 μm / s; cantilever stiffness k = 0.3 N / m; known physical constant water viscosity μ = 1 mPa∙s; actual radius R = 50 μm obtained by precise measurement of the ball using a scanning electron microscope. These parameters were then used to obtain the slip distance b of the superhydrophobic carbonate rock from the force curve of the underwater model.

[0124] The theoretical model designs a superhydrophobic surface for carbonate rocks, which causes water droplets to form many "cavitation" at the interface of the carbonate rock core. This causes the water droplets to roll rapidly on the surface, thereby greatly reducing the ability of water to be adsorbed on the core surface and ensuring the stable production of gas in actual carbonate gas reservoirs.

[0125] Therefore, those skilled in the art will recognize that although embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

[0126] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for measuring the superhydrophobic slip mechanism based on carbonate rocks, characterized in that, include: Preparation of superhydrophobic nano-silica particles; Superhydrophobic modification was performed on carbonate rock cores to obtain superhydrophobic carbonate rock samples; A theoretical measurement model for interface boundary slip in rough surface contact mode was constructed based on superhydrophobic nano-silica particles and superhydrophobic carbonate rock samples. Substituting the force curve of the underwater model obtained by atomic force microscopy into the model, the boundary slip distance b of the superhydrophobic carbonate rock interface was calculated.

2. The method according to claim 1, characterized in that, The preparation of superhydrophobic nano-silica particles includes: Nano-silica was placed in a prepared organic solution and ultrasonically dispersed for 20 minutes to obtain a nano-silica suspension. The nano-silica suspension was stirred at 3000 r / min for 20 minutes to obtain a homogenized nano-silica suspension. The homogenized nano silica suspension was placed in an environment of 75°C and surface modified with alkylsilane at a concentration of 3wt% for 12 hours to obtain alkylsilane modified silica nanoparticles. Alkylsilane-modified silica nanoparticles were washed sequentially with deionized water and anhydrous ethanol, centrifuged, dried at 60°C, and then ground into powder to obtain superhydrophobic silica nanoparticles.

3. The method according to claim 2, characterized in that, The prepared organic solution is a mixture of dimethylformamide and tetrahydrofuran in a volume ratio of 7:

3.

4. The method according to claim 2, characterized in that, The nano-silica is placed in the prepared organic solution at a mass fraction of 30%.

5. The method according to claim 1, characterized in that, The superhydrophobic modification of carbonate rock cores to obtain superhydrophobic carbonate rock samples includes: Prepare a polysiloxane solution with a concentration of 2.5 mg / L and stir until completely dissolved; Carbonate rock core slices were placed in a mixed solution of dissolved polysiloxane solution and 30% by mass of superhydrophobic nano silica particles, and modified at 120°C for 6 hours to obtain carbonate rock cores with preliminary surface modification. The carbonate rock core with preliminary surface modification was dried at 60℃ for 12 hours to obtain a superhydrophobic carbonate rock sample.

6. The method according to claim 1, characterized in that, The method of constructing a theoretical measurement model for interface boundary slip in rough surface contact modes includes: Establish a theoretical coordinate system and interface geometric model, set boundary conditions and initial parameters, and complete the construction of the theoretical framework; Based on the Navier-Stokes equations and the fluid momentum equations, the fluid control equations are derived and the Navier boundary slip condition is defined, resulting in a set of theoretical equations that include the slip distance b. Solving the fluid velocity and pressure distribution functions in the theoretical equations yields a mathematical description of the fluid dynamics behavior. The fluid force is calculated using the integral fluid pressure distribution function, and experimental measurement parameters from atomic force microscopy are introduced to establish a correlation model between the fluid force and experimental observations.

7. The method according to claim 1, characterized in that, The atomic force microscope (AFM) probe measures the model force curves underwater, including: Microspheres were cleaned in an ultrasonic cleaner using acetone and methanol solutions, then allowed to stand at room temperature. The microspheres were then precisely bonded to the end of an atomic force microscope probe using epoxy resin adhesive to obtain a microsphere-modified colloidal probe. The modified carbonate rock sample was fixed on the sample stage, and the colloidal probe was installed using a polychlorotrifluoroethylene underwater probe holder. Real-time monitoring was performed using reflected laser light. Test liquid is dripped between the liquid holder and the sample to form a stable crescent-shaped droplet, ensuring continuous liquid contact between the holder and the superhydrophobic core interface; Use a pipette to add 100 μL of test liquid to the interface of the sample under test, and at the same time add a drop of 20 μL of liquid to the probe of the atomic force microscope. Then drive the probe close to the sample interface and measure the relationship curve between the cantilever deformation and the separation distance under the liquid. Based on the elastic stiffness of the probe cantilever, the cantilever deformation is converted into force to obtain the force curve of the underwater model.

8. The method according to claim 1, characterized in that, The carbonate rocks include single-material calcite, dolomite, and mixtures of calcite and dolomite.

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