Experimental device and method for studying using capacity of membranous remaining oil

Abstract

The invention discloses an experimental device and method for studying the using capacity of membranous remaining oil, and belongs to the technical field of water injection oil extraction experiments, the experimental device comprises rock arranged in a base groove and a transparent cover at the top of the rock, a liquid inlet of the base groove is connected with a displacement assembly, and a liquid outlet of the base groove is connected with a collecting barrel; a rock plate simulating underground oil reservoir rock is prepared, the height of the rock plate is adjusted through a hydraulic power assembly, an oil film on the surface of the rock plate is scraped to be flat through a film scraper, water is injected into a groove through a displacement assembly to enable the oil film on the surface of the rock plate to be in a water phase, and the oil film on the rock plate is heated or cooled through a temperature control instrument. The form of the remaining oil on the rock plate is observed through the image acquisition module, and the influence of different oil film thicknesses and different oil product types on the temperature required for converting the oil film-shaped remaining oil into liquid drop-shaped remaining oil under the water phase condition is explored. The device is convenient to operate, simple in structure and direct in observation, quantitative property evaluation can be carried out on the using capacity of the membrane-shaped residual oil, and the effect of improving the recovery ratio is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of water injection oil production experiments, and in particular relates to an experimental device and method for studying the mobilization capacity of film-like residual oil. Background Art

[0002] Residual oil refers to the oil that has not yet been produced in the oil layer, oil reservoir or oil field that has been put into development. In the process of water injection oil production, due to the complex situations encountered during the fluid flow process, various types of residual oil will be formed after water injection, including continuous and dispersed residual oil. The specific forms include film, cluster, column, "island" and angular. Membrane residual oil refers to the part of crude oil that remains in the pores in the form of oil film due to the complexity of rock pores during water injection oil production and has not been completely displaced. The formation of film residual oil is mainly due to the fact that when the crude oil is displaced, the injected water passes through the center of the pore and preferentially displaces the crude oil in the middle part of the pore, and the adhesion of the pore wall is greater than the shear force of water on the oil film, which leads to the formation of oil film.

[0003] As we all know, most oil fields enter the high water content oil recovery stage in the middle and late stages of development. After water injection development, 60% to 70% of the oil underground is still unextracted, becoming residual oil. With the development of the national economy, the demand for oil and natural gas has increased year by year, and the contradiction between supply and demand has become increasingly prominent. Therefore, strengthening the research on the distribution of residual oil has important practical significance for improving the recovery rate. Summary of the invention

[0004] In order to solve the above problems, the present invention provides an experimental device and method for studying the mobilization capacity of film-like residual oil.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: An experimental device for studying the mobilization capacity of film-like residual oil, the experimental device comprising a rock plate for simulating underground oil reservoir rock, the rock plate being arranged in a groove of a base, a transparent cover being arranged on the top of the base, and the four edges of the two being connected; a liquid inlet of the base groove being connected to a displacement component, and a liquid outlet being connected to a collection bucket; a film scraper being able to scrape the oil film on the surface of the rock plate; the rock plate being connected to a temperature control instrument for heating or cooling the rock plate; the bottom of the rock plate being connected to a hydraulic power assembly for adjusting the height of the rock plate; an image acquisition module being arranged above the rock plate and the transparent cover, and the displacement component, the temperature control instrument, the hydraulic power assembly and the image acquisition module being all connected to a computer.

[0006] Furthermore, the displacement assembly includes a constant pressure constant speed displacement pump, a first piston container and a second piston container, the inlet ends of the first piston container and the second piston container are connected in parallel with the constant pressure constant speed displacement pump, and the outlet ends of the first piston container and the second piston container are connected in parallel with the liquid inlet of the base groove; the first piston container contains water, and the second piston container contains cleaning liquid. The constant pressure constant speed displacement pump is controlled by a computer and can achieve stable output of the fluid in the rock plate.

[0007] Furthermore, the film scraper includes a lead screw and a scraper, the lead screw is threadedly matched with a nut, and the scraper is connected to the nut; a hand wheel is provided at one end of the lead screw.

[0008] Furthermore, the hydraulic power assembly includes a hydraulic pump and a multi-stage hydraulic cylinder. The hydraulic pump is controlled by a computer. The hydraulic oil of the hydraulic pump is pushed to the multi-stage hydraulic cylinder through the computer. The oil pressure is adjusted to control the step-by-step extension and retraction of the multi-stage piston to adjust the bottom support height of the base groove, thereby achieving ±10μm height adjustment of the rock plate.

[0009] Furthermore, the image acquisition module is a microscope, which is used to observe the morphology of residual oil on the rock plate.

[0010] Furthermore, the preparation method of the rock plate is as follows: Select underground oil reservoir rock samples, clean them and dry them; The dried rock samples are crushed into rock particles and sieved to obtain uniform rock particles; Mix rock particles, adhesive and resin in the following proportions, pour the evenly mixed materials into a mold to obtain a formed rock slab; The ratio of simulated sandstone is: 75% quartz sand + 12% epoxy resin + 10% phenolic resin + 3% silane coupling agent; Alternatively, the ratio of simulated carbonate rock is: 80% calcium carbonate powder + 10% silicate cement + 10% polyurethane resin; After grinding the rock slab with abrasives or grinding discs, polish the rock slab; [Use coarse abrasives or grinding discs to grind the rock slab initially, and then use medium abrasives or grinding discs and fine abrasives or grinding discs to further grind] Furthermore, the roughness of the rock plate is represented by the following composite function:

[0011] Where: is the rock characterization coefficient, For surface heterogeneous dynamics, It is the micro-geometric difference; The rock characterization coefficient ε is a dimensionless parameter that describes the degree of deviation of the macroscopic geometric profile of the rock plate surface from the ideal plane, reflecting the overall uniformity of the rock particle distribution. ε≈0 The surface is close to the ideal plane (such as a glass plate) ε>0.5 The surface is highly irregular (such as unpolished sandstone), experimental correlation: The larger the ε, the stronger the oil film adhesion, and the critical flow rate needs to be increased Surface heterogeneity dynamic δ characterizes the dynamic response ability of the chemical / wettability heterogeneity of the rock plate surface, which is defined as the ratio of the wetting contact angle hysteresis to the temperature change rate. High δ: The surface wettability is sensitive to temperature changes, which can easily cause local rupture of the oil film (promote dropletization); low δ: The surface chemical properties are stable and the oil film is difficult to peel off. Micro-geometric variability γ describes the degree of discreteness of the surface micro-roughness features, which is determined by the ratio of the standard deviation of the surface height distribution to the autocorrelation length. γ≤1: The surface texture is regular (such as mechanical polishing surface) γ≥1: There are sharp protrusions / deep grooves on the surface (such as rocks with natural cracks).

[0012] The present invention also provides an experimental method for studying the mobilization capacity of film-like residual oil. The experiment is carried out using the above experimental device, and comprises the following steps: Assemble the above experimental apparatus; Open the transparent cover, lay a layer of oil film on the rock plate in advance to simulate the residual oil, start the hydraulic power assembly to adjust the height of the rock plate to make the elevation of its upper surface consistent; start the film scraper to keep the thickness of the oil film on the rock plate consistent; close the transparent cover after adjustment; Start the displacement component to deliver water into the groove to flush the rock plate, adjust the water flow from low to high, and observe and record the morphological changes of the remaining oil on the surface of the rock plate through the image acquisition module; When the film-like remaining oil on the rock plate changes into oil drop-like remaining oil, record the water flow rate at this time to determine the relationship between the flow rate and the change in the remaining oil morphology; Start the displacement assembly again to deliver the cleaning fluid into the groove of the base to clean the groove and the rock plate; The evaluation formula for the mobilization capacity of film residual oil obtained through experiments is as follows:

[0013] Where: ME —mobilization capacity of film residual oil; A—constant, usually 0.8; Q—flow rate; Q c — critical flow; When the flow rate is lower than Qc, the oil film remains stable; When the flow rate ≥ Qc, the oil film begins to break and transform into droplets; Relationship between flow rate and mobilization capacity: When the flow rate exceeds Qc, ME is linearly positively correlated with (Q-Qc); the greater the flow rate, the higher the oil film breaking efficiency; The calculation formula of oil film conversion rate R is as follows:

[0014] Where: T—temperature, K; Q—flow rate, ml / min; η—dynamic viscosity of crude oil, mPa·s; h—initial thickness of oil film, μm; γ—oil-water interfacial tension, mN / m; The calculation formula of oil film glass rate OFR is as follows:

[0015] Where: k 1 —constant, usually 0.25; T—temperature, K; Q—flow rate, ml / min; η—dynamic viscosity of crude oil, mPa·s; h—initial thickness of oil film, μm; γ—oil-water interfacial tension, mN / m; θ—contact angle; The conclusion drawn from the above formula is: the higher the oil film conversion rate R, the higher the oil film glass rate OFR, and the stronger the residual oil mobilization ability; the lower the oil film conversion rate R, the lower the oil film glass rate OFR, the weaker the residual oil mobilization ability, the more stable the oil film, and the higher the residual oil retention.

[0016] Furthermore, when water enters the groove of the base to flush the oil film on the rock plate, the rock plate is heated by a temperature control instrument, and images at different time points are collected by an image acquisition module. During the heating process, the morphological changes of the residual oil are regularly observed and recorded, and the collected images are analyzed by a computer to determine the oil film glass fraction OFR. When the oil film begins to break and transform into droplet-shaped residual oil, the temperature and heating time at this time are recorded, and the oil film conversion rate R is calculated to evaluate the efficiency of the conversion of oil film-shaped residual oil to droplet-shaped residual oil.

[0017] Furthermore, the oil type of the oil film was changed, and the temperature required for the oil film to transform into droplet residual oil under water phase conditions was observed and recorded. The critical temperature T of the film residual oil to droplet transformation of different oil types was c The influence of is derived through the functional relationship between the oil film conversion rate R and the oil film glass rate OFR. The functional relationship is as follows:

[0018] Where: T c —The critical temperature corresponding to the oil type, characterized by the oil type viscosity η, density ρ, and interfacial tension γ, K; k 3 —Proportional constant, usually taken as 50; η—dynamic viscosity of crude oil, mPa·s; ρ—density of crude oil, g / cm³; cosθ: rock surface wettability, θ is the contact angle.

[0019] Compared with the prior art, the present invention has the following technical advances: The present invention simulates underground reservoir rocks by using rock plates, uses hydraulic power components to adjust the height of the rock plates, and uses a film scraper to scrape the oil film on the surface of the rock plates. Water is injected into the groove of the base through the displacement component to make the oil film on the surface of the rock plates in the water phase. The oil film on the rock plates is heated or cooled by a temperature control instrument, and the residual oil morphology on the rock plates is observed by an image acquisition module to explore the influence of different oil film thicknesses and different oil types on the temperature required for the oil film-like residual oil to be transformed into droplet-like residual oil under water phase conditions. The present invention has a simple structure, convenient operation, and direct observation. It can quantitatively evaluate the mobilization capacity of the film-like residual oil, thereby further improving the recovery rate. The present invention has important theoretical guidance value and practical significance for optimizing oilfield development plans and improving crude oil recovery by revealing the key conditions for the transformation of film-like residual oil into droplet-like residual oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0021] In the attached picture: Figure 1 A schematic diagram of the structure of an experimental device for studying the mobilization capacity of film-like residual oil provided by an embodiment of the present invention; In the figure: 1-constant pressure constant speed displacement pump, 2-first piston container, 3-second piston container, 4-microscope, 5-groove, 6-temperature control instrument, 7-multi-stage hydraulic cylinder, 8-hydraulic pump, 9-transparent cover, 10-computer, 11-hand wheel, 12-scraper, 13-collecting bucket; 14-rock plate; 15-screw. DETAILED DESCRIPTION

[0022] The following specific embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments. The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0023] like Figure 1As shown, an experimental device for studying the mobilization capacity of film-like residual oil, the experimental device includes a rock plate 14 for simulating underground oil reservoir rock, the rock plate 14 is arranged in a groove 5 of a base, a transparent cover 9 is provided on the top of the base, and the edges of the two are connected; the liquid inlet of the base groove 5 is connected to the displacement component, and the liquid outlet is connected to the collection bucket 13; the scraper can scrape the oil film on the surface of the rock plate 14; the rock plate 14 is connected to the temperature control instrument 6 for heating or cooling the rock plate 14; the bottom of the rock plate 14 is connected to the hydraulic power component for adjusting the height of the rock plate 14; an image acquisition module 4 is provided above the rock plate 14 and the transparent cover 9, and the displacement component, temperature control instrument, hydraulic power component and image acquisition module are all connected to the computer 10 to facilitate automatic control.

[0024] In a specific embodiment of the present invention, the displacement assembly includes a constant pressure constant speed displacement pump 1, a first piston container 2 and a second piston container 3, the inlet ends of the first piston container 2 and the second piston container 3 are connected in parallel with the constant pressure constant speed displacement pump 1, and the outlet ends of the first piston container 2 and the second piston container 3 are connected in parallel with the liquid inlet of the base groove 5; the first piston container 2 contains water, and the water is injected into the groove by the constant pressure constant speed displacement pump so that the oil film on the rock plate is immersed in water; the second piston container 3 contains cleaning liquid, and the cleaning liquid can be used to clean the groove and the rock plate after the experiment is completed, so as to prepare for the next experiment. At the same time, the outlet end of the groove is connected to the collection barrel through a recovery pipe, which can effectively collect and store the discharged waste liquid, which is convenient for subsequent centralized treatment. The constant pressure constant speed displacement pump 1 is controlled by a computer 10, which can realize the stable flow of the fluid in the groove. The constant pressure constant speed displacement pump can accurately control the flow and pressure of the water, ensure the stability and accuracy of the water flow during the experiment, and realize the analysis of the mobilization of the film residual oil under different flow conditions.

[0025] As the output water flow rate of the constant pressure and constant speed displacement pump increases, the flushing force of the water injected into the groove on the crude oil on the surface of the rock plate will also increase. This flushing force helps to break the continuous state of the crude oil, causing it to gradually transform from a film-like state to a dispersed droplet-like state. Therefore, a larger flow rate helps to promote the transformation of film-like residual oil to droplet-like residual oil. Changes in flow rate also affect the size of the oil droplets. Generally speaking, as the flow rate increases, the average volume of the oil droplets decreases, while the number of oil droplets increases. This is because the faster water flow rate causes more violent disturbances and stronger shear effects on the surface of the linear oil film, making the surface energy of the oil droplets insufficient to maintain its complete shape at a relatively large size, causing the oil droplets to split into smaller droplets. Therefore, a larger flow rate tends to result in smaller oil droplet sizes and more uniform oil droplet distribution.

[0026] The present invention uses a constant pressure and constant speed displacement pump to measure the critical flow rate at which the film-like residual oil undergoes droplet transformation. The relationship between the flow rate and the mobilization capacity of the film-like residual oil is shown in the formula:

[0027] Where: ME—mobilization capacity of filmy residual oil; A —constant, usually 0.8; Q—flow rate; Q c —Critical flow.

[0028] Critical flow rate Qc: When the flow rate is lower than Qc, the oil film remains stable; When the flow rate ≥ Qc, the oil film begins to break and transform into droplets.

[0029] Relationship between flow rate and mobilization capacity: After the flow rate exceeds Qc, ME is linearly positively correlated with (Q-Qc); the larger the flow rate, the higher the oil film breaking efficiency. As a preferred structure, the film scraper includes a lead screw 15 and a scraper 12, the lead screw 15 is threaded with a nut, and the scraper 12 is connected to the nut; a hand wheel 11 is provided at one end of the lead screw 15. The lead screw transmission belongs to the prior art and will not be described here. The scraper is driven to move back and forth by shaking the hand wheel, thereby scraping the oil film on the surface of the rock plate.

[0030] In a specific embodiment of the present invention, the hydraulic power assembly includes a hydraulic pump 8 and a multi-stage hydraulic cylinder 7. The hydraulic pump 8 is controlled by a computer 10. The hydraulic oil of the hydraulic pump 8 is pushed to the multi-stage hydraulic cylinder 7 by the computer. The oil pressure is adjusted to control the step-by-step extension and retraction of the multi-stage piston in the multi-stage hydraulic cylinder 7 to adjust the bottom support height of the base groove 5, thereby achieving ±10μm level height adjustment of the rock plate 14. The multi-stage hydraulic cylinder adopts a multi-stage sleeve hydraulic cylinder. The multi-stage sleeve hydraulic cylinder can achieve a longer stroke through a multi-section piston. The computer controls the hydraulic pump through a digital signal to achieve precise adjustment of the bottom of the groove, and finally uses a sensor to monitor the real-time position in real time.

[0031] During specific production, the image acquisition module 4 is a microscope, which is used to observe the morphology of the residual oil on the rock plate 14. When in use, the microscope can be adjusted to a suitable observation position to ensure that the morphology of the residual oil on the rock plate can be clearly observed. The water flow in the groove is adjusted by a constant pressure and constant speed displacement pump, and the morphological changes of the residual oil are carefully observed using a microscope. The morphological changes of the residual oil at each flow rate are observed and recorded to ensure the accuracy of the observation results. When it is observed that the film-like residual oil begins to transform into oil droplet-like residual oil, the flow value at this time is recorded to determine the relationship between the flow rate and the morphological changes of the residual oil.

[0032] In addition, the temperature control instrument 6 is mainly composed of a heater, a temperature sensor, a controller and an actuator. The heater is responsible for providing heat energy to heat up the object; the temperature sensor is used to monitor the temperature of the object in real time and feed back the temperature signal to the controller; the controller adjusts the power of the heater through an actuator (such as a relay, a transistor, etc.) according to the difference between the preset temperature value and the actual temperature value, thereby achieving precise control of the temperature of the object. This is a prior art and can be purchased outsourced according to experimental needs. The device can respond quickly to temperature changes and quickly adjust the power of the heater to achieve rapid heating and automatic temperature control.

[0033] In a specific embodiment of the present invention, the preparation method of the rock plate 14 is as follows: According to the experimental needs, select representative underground reservoir rock samples, such as sandstone, carbonate rock, etc. The selected rock samples are cleaned to remove surface impurities and contaminants, and then dried.

[0034] The dried rock samples are crushed into rock particles and sieved to obtain evenly distributed rock particles; Mix the sieved rock particles with adhesive and resin in a certain proportion, such as sandstone simulation: 75% quartz sand + 12% epoxy resin + 10% phenolic resin + 3% silane coupling agent, carbonate rock simulation: 80% calcium carbonate powder + 10% silicate cement + 10% polyurethane resin. Pour the mixed materials into the mold to obtain the formed rock plate. The shape and size of the mold should be designed according to the experimental needs.

[0035] After grinding the rock slab with abrasives or grinding discs, the rock slab is polished; the specific grinding process is as follows: First, use a coarse abrasive or grinding disc to grind the rock slab preliminarily to remove surface unevenness and flaws. On the basis of coarse grinding, use medium abrasive or grinding disc for further grinding to make the surface of the rock slab smoother. Then use finer abrasive or grinding disc for further grinding to further improve the smoothness and glossiness of the rock slab surface. Finally, polish the rock slab with a polishing agent or polishing paste to make the surface of the rock slab present a bright luster. The roughness of the rock slab is a key parameter to describe the microscopic unevenness of the rock slab surface, which directly affects the adhesion between the oil film and the rock slab substrate and the efficiency of the remaining oil mobilization. The roughness of the rock slab is represented by the following composite function:

[0036] Where: is the rock characterization coefficient, For surface heterogeneous dynamics, It is the micro-geometric difference.

[0037] :This function converts the rock characterization coefficient into a logarithmic expression , surface heterogeneity dynamics , and micro-geometric differences This formalism aims to capture the interactions and nonlinear effects between these complex properties.

[0038] here Directly add an exponential term, which represents more complex and high-order changes, and can simulate the variation of roughness at different scales. Superimpose δ (chemical dynamic characteristics) and γ (micro-geometric characteristics) in an exponential form to nonlinearly amplify the combined effect of the two. If δ and γ increase at the same time, e δ+γ will rise sharply, significantly increasing the value of the roughness function.

[0039] Moderate roughness: Promotes the transformation of oil film-like residual oil into droplet-like residual oil by enhancing shear and reducing contact area.

[0040] Excessive roughness: Geometric capture and wetting reversal hinder the transformation of oil film-like residual oil into droplet-like residual oil.

[0041] Moderately rough range: ∈[1.5,3.0], rock characterization coefficient ε∈[0.3,0.6], δ∈[2,5] micro-geometry variability γ∈[0.8,1.2].

[0042] Excessive roughness interval: >3.5, ε∈0.8, γ>1.5.

[0043] The present invention also provides an experimental method for studying the mobilization capacity of film-like residual oil. The experiment is carried out using the above experimental device, and comprises the following steps: S1: Assemble the above experimental apparatus; S2: Open the transparent cover, lay a layer of oil film on the rock plate in advance to simulate the remaining oil, and control the hydraulic pump through the computer to push the liquid to the multi-stage hydraulic cylinder. Monitor the output pressure of the hydraulic pump in real time, and automatically adjust the working state of the pump through the feedback loop to ensure stable and accurate pressure. The telescopic action of the multi-stage hydraulic cylinder is controlled by the signal sent by the computer. According to the target adjustment requirements at the bottom of the groove, the telescopic length of the hydraulic cylinder is adjusted in stages. The real-time data (displacement, pressure) of the sensor in the hydraulic cylinder is analyzed by the computer, and the subtle position of the hydraulic cylinder is gradually adjusted to ensure that there is no jump or deviation during the adjustment process. The hydraulic cylinder transmits the adjustment force to the bottom of the groove to achieve fine-tuning of the height of the rock plate and make the elevation of the upper surface of the rock plate consistent.

[0044] S3: Drive the scraper by hand wheel, adjust the scraper accurately by linear motion, scrape the remaining oil film thickness, make the oil film thickness consistent at the beginning of each experiment, and keep the oil film flat. Close the transparent cover after adjustment.

[0045] S4: Start the constant pressure and constant speed displacement pump, and let the water in the first piston container enter the groove at a certain flow rate to flush the rock plate. Adjust the microscope to a suitable observation position, and observe and record the morphology of the residual oil on the surface of the rock plate. Gradually adjust the water flow rate from low to high, observe and record the morphological changes of the residual oil at each flow rate. When the film-like residual oil begins to transform into oil droplet-like residual oil, record the flow value at this time to determine the relationship between the flow rate and the morphological changes of the residual oil.

[0046] S5: Dispose of waste liquid according to specifications, start the constant pressure and constant speed displacement pump again, transfer the cleaning liquid in the second piston container to the groove, clean the groove and the rock plate to facilitate the next test, check whether the valves of the two piston containers are closed, turn off the microscope and computer, and the test is over.

[0047] The evaluation formula for the mobilization capacity of film residual oil obtained through the above experiments is as follows:

[0048] Where: ME—mobilization capacity of filmy residual oil; A—constant, usually 0.8; Q—flow rate; Q c —Critical flow.

[0049] Through this experiment, the influence of different oil film thicknesses and different oil types on the temperature required for the oil film-like residual oil to be transformed into droplet-like residual oil under water phase conditions is explored. Ensure that the type of oil used in each experiment is the same so as to compare the influence of different oil film thicknesses. Alternatively, different types of oils are used in different experimental groups to compare the influence of oil types. Therefore, the present invention can explore the influence of different oil film thicknesses and different oil types on the temperature required for the oil film-like residual oil to be transformed into droplet-like residual oil under water phase conditions.

[0050] (I) Under the same conditions, the influence of different oil film thickness on the critical temperature required for film residual oil dropletization was investigated. The critical temperature of film residual oil dropletization (T c The relationship between ) and oil film thickness (h) can be derived from the functional model of oil film glass fraction (OFR) and oil film conversion rate (R). Combining the key parameters and formulas in the experimental description, the following functional relationship can be constructed:

[0051] Where: T c(h)—critical temperature when the oil film thickness is h; k 2 — proportionality constant, which is related to the experimental conditions and the properties of the oil; k 1 —Constant, usually taken as 0.25, obtained from the oil film conversion rate formula; — rock characterization coefficient; — Surface heterogeneity dynamics; —Micro-geometric differences; h is the oil film thickness, n is an empirical index (usually n>0), reflecting the negative correlation between thickness and critical temperature.

[0052] At the beginning of the experiment, the same oil was used to unify the variables, the transparent cover was opened, the rock plate was fixed in the groove, the hydraulic pump was started, and the position of the multi-stage hydraulic cylinder was controlled by a digital signal sent by the computer to fine-tune the rock plate to the target height (adjusted in units of tens of microns). The high-precision adjustment function of the hydraulic cylinder was used to make the height of the bottom of the groove meet the experimental requirements. The scraper was driven by a handwheel, and the contact position and pressure between the scraper and the rock plate were adjusted through linear motion to scrape out oil films of different thicknesses. The difference in thickness was precisely controlled by the forward and backward movement distance of the scraper to ensure that the thickness of the oil film was evenly distributed. After completion, the transparent cover was closed and the experimental sample was fixed.

[0053] According to the purpose and needs of the experiment, a series of temperature gradients are set. For example, starting from room temperature, gradually increase to a predetermined maximum temperature. Each temperature gradient requires a period of heating and observation to ensure that the changes of the residual oil at this temperature are fully reflected. Put the film residual oil sample into the heating device and set the required temperature. Start the temperature control instrument to start heating and closely observe the changes in the oil film. Use a microscope and other equipment to capture images at different time points. During the heating process, regularly observe and record the morphological changes of the residual oil. The computer automatically analyzes the images recorded by the microscope and determines the oil film glass fraction (OFR), which is a characterizing parameter of the effect of the change in oil-water interfacial tension on the stability of the oil film. As the heating proceeds, closely observe the changes in the oil film. When the oil film begins to break and transform into droplet-shaped residual oil, record the temperature and heating time at this time. At the same time, calculate the oil film conversion rate (R) to evaluate the efficiency of the transformation of oil film-shaped residual oil to droplet-shaped residual oil. This is used to characterize the temperature required for the transformation of oil film-shaped residual oil to droplet-shaped residual oil under different thickness conditions.

[0054] (II) Under the same other conditions, explore the temperature required for different oil types to transform from oil film residual oil to droplet residual oil under water phase conditions, and the critical temperature T of film residual oil droplet transformation for different oil types. cThe influence of can be constructed as follows:

[0055] Where: T c —The critical temperature corresponding to the oil type, characterized by the oil type viscosity η, density ρ, and interfacial tension γ, K; k 3 —Proportional constant; usually taken as 50; η—dynamic viscosity of crude oil, mPa·s; ρ—density of crude oil, g / cm³; cosθ: rock surface wettability (θ is the contact angle).

[0056] The above experimental device was fixed on the experimental platform, the transparent cover was opened, the hydraulic pump was started, and the hydraulic pump was controlled by the computer to push the liquid to the multi-stage hydraulic cylinder. The multi-stage hydraulic cylinder gradually adjusted the height through computer instructions, and the bottom of the container was accurately adjusted to the target position (with an accuracy range of tens of microns). At the beginning of the experiment, the thickness of the oil film should be kept consistent to unify the variables. The scraper was driven by a handwheel, and the contact pressure and position between the scraper and the bottom of the container were adjusted by linear motion to scrape out an oil film of uniform thickness. Ensure that the thickness of the oil film is consistent to provide uniform conditions for subsequent experiments with different oil types. In order to compare the effects of different oil types. Select several representative oil types, such as light oil, medium oil, heavy oil, or a specific type of industrial oil. Ensure that each oil has enough volume for multiple experiments. Start the temperature control instrument and use a thermometer to monitor the oil film temperature to ensure that the temperature rises at a predetermined rate. Use a microscope to observe the process of the oil film-like residual oil turning into droplet-like residual oil. When obvious oil droplets are observed, stop heating immediately and use a timer to record the time required from the start of heating to the formation of oil droplets. At the same time, record the temperature at this time. Based on the data analysis results, specific conclusions were drawn about the temperature required for different oil types to transform from oil film-like residual oil to droplet-like residual oil under water phase conditions. The microscope image data was processed by computer to calculate the oil film glass fraction (OFR), which is a parameter that characterizes the effect of oil-water interfacial tension changes on oil film stability. At the same time, the oil film conversion rate (R) was calculated to evaluate the efficiency of the transformation of oil film-like residual oil to droplet-like residual oil.

[0057] 1. The calculation formula of oil film conversion rate R is as follows:

[0058] Where: T—temperature, K; Q—flow rate, ml / min; η—dynamic viscosity of crude oil, mPa·s; h—initial thickness of oil film, μm; γ—oil-water interfacial tension, mN / m.

[0059] (1) The higher the oil film conversion rate (R), the stronger the residual oil mobilization capacity Temperature (T) rises: High temperature will reduce the viscosity of crude oil (η↓), making the oil film easier to be peeled off by water flow and broken into droplets. By observing the oil film rupture process by heating, it is shown that temperature rise can significantly increase the oil film conversion rate (R) and enhance the ability to mobilize the remaining oil.

[0060] Increased flow rate (Q): Increased flow rate means increased water shear force, which directly destroys the oil film structure and promotes oil film rupture (R↑).

[0061] The initial thickness of the oil film (h) decreases: the thinner the oil film is, the easier it is for the shear force of the water flow to penetrate and destroy the oil film structure, and the mobilization capacity is enhanced.

[0062] Viscosity (η) decreases: Low-viscosity crude oil has better fluidity and the oil film is easier to be stripped by the displacing fluid (R↑).

[0063] (2) The lower the oil film conversion rate (R), the weaker the remaining oil mobilization capacity Low temperature, low flow rate, low shear force (such as low flow water injection) or high viscosity crude oil will reduce the oil film conversion rate (R↓), resulting in enhanced oil film stability and difficulty in displacing the remaining oil.

[0064] 2. The calculation formula of oil film glass rate OFR is as follows:

[0065] Where: k 1 —Empirical constant, which needs to be calibrated by experiment or corrected by different conditions; OFR values ​​under different conditions are measured by core flow experiment or microscopic visualization experiment, and k in the reverse fitting formula is 1 , usually 0.25 T—temperature, K; Q—flow rate, ml / min; η—dynamic viscosity of crude oil, mPa·s; h—initial thickness of oil film, μm; γ—oil-water interfacial tension, mN / m; θ—contact angle.

[0066] (1) The higher the OFR, the stronger the remaining oil mobilization capacity Increased flow rate (Q): In the formula, Q is positively correlated with OFR. When the flow rate increases, the shear force of the fluid on the oil film increases, which makes it easier to destroy the continuity of the oil film and break it into droplets. "As the flow rate increases, the average volume of the oil droplets decreases and the number increases", which means that high OFR can more effectively drive the film-like residual oil to transform into movable droplets.

[0067] Oil-water interfacial tension (γ) decreases: The lower the interfacial tension, the easier it is for the oil film to be stripped by water flow, the OFR increases, and the remaining oil is easier to be displaced.

[0068] Viscosity (η) decreases: Fluids with low viscosity and density (such as light oil or low-mineralization water) are more fluid, have a more significant shearing effect on the oil film, increase OFR, and increase the amount of residual oil mobilized.

[0069] Contact angle (θ) optimization: The contact angle θ is the core parameter that characterizes the wettability of the rock surface. The smaller its value (strong hydrophilicity), the easier it is for the oil film to be stripped off, the higher the OFR, and the stronger the ability to mobilize the remaining oil.

[0070] (2) The lower the OFR, the weaker the remaining oil mobilization capacity When the flow rate is low, the interfacial tension is high, the fluid is viscous or the rock surface is hydrophobic, the OFR decreases, the oil film stability increases, the remaining oil is difficult to be displaced, and the mobilized amount decreases.

[0071] The conclusions obtained are: the higher the OFR, the easier it is for the oil film to break into movable droplets, and the greater the amount of residual oil mobilization. The lower the OFR, the more stable the oil film, and the higher the residual oil retention.

[0072] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. An experimental device for studying the mobilization capacity of film-like residual oil, characterized in that: The experimental device includes a rock plate for simulating underground oil reservoir rocks, the rock plate is arranged in a groove of a base, a transparent cover is provided on the top of the base, and the edges of the two are connected; the liquid inlet of the base groove is connected to the displacement component, and the liquid outlet is connected to the collection bucket; the scraper can scrape the oil film on the surface of the rock plate; the rock plate is connected to a temperature control instrument for heating or cooling the rock plate; the bottom of the rock plate is connected to a hydraulic power assembly for adjusting the height of the rock plate; an image acquisition module is provided above the rock plate and the transparent cover.

2. The experimental device for studying the mobilization capacity of film-like residual oil according to claim 1, characterized in that: The displacement assembly includes a constant pressure and constant speed displacement pump, a first piston container and a second piston container. The inlet ends of the first piston container and the second piston container are connected in parallel with the constant pressure and constant speed displacement pump, and the outlet ends of the first piston container and the second piston container are connected in parallel with the liquid inlet of the base groove; the first piston container contains water, and the second piston container contains cleaning liquid.

3. The experimental device for studying the mobilization capacity of film-like residual oil according to claim 1 is characterized in that: The film scraper comprises a lead screw and a scraper, wherein the lead screw is threadably matched with a nut, and the scraper is connected with the nut; a hand wheel is arranged at one end of the lead screw.

4. The experimental device for studying the mobilization capacity of film-like residual oil according to claim 1 is characterized in that: The hydraulic power assembly includes a hydraulic pump and a multi-stage hydraulic cylinder. The hydraulic pump is controlled by a computer. The computer pushes the hydraulic oil of the hydraulic pump to the multi-stage hydraulic cylinder. The oil pressure is adjusted to control the step-by-step extension and retraction of the multi-stage pistons in the multi-stage hydraulic cylinder to adjust the bottom support height of the base groove, thereby achieving ±10μm height adjustment of the rock plate.

5. The experimental device for studying the mobilization capacity of film-like residual oil according to claim 1 is characterized in that: The image acquisition module is a microscope, which is used to observe the morphology of the remaining oil on the rock plate.

6. The experimental device for studying the mobilization capacity of film-like residual oil according to claim 1 is characterized in that: The preparation method of the rock plate is as follows: Select underground oil reservoir rock samples, clean them and dry them; The dried rock samples are crushed into rock particles and sieved to obtain uniform rock particles; Mix rock particles, adhesive and resin in the following proportions, pour the evenly mixed materials into a mold to obtain a formed rock slab; The ratio of simulated sandstone is: 75% quartz sand + 12% epoxy resin + 10% phenolic resin + 3% silane coupling agent; Alternatively, the ratio of simulated carbonate rock is: 80% calcium carbonate powder + 10% silicate cement + 10% polyurethane resin; After grinding the rock slab with abrasives or grinding discs, the rock slab is polished.

7. The experimental device for studying the mobilization capacity of film-like residual oil according to claim 6, characterized in that: The roughness of the rock plate is expressed by the following composite function: ； Where: is the rock characterization coefficient, For surface heterogeneous dynamics, It is the micro-geometric difference; The rock characterization coefficient ε is a dimensionless parameter that describes the degree of deviation between the macroscopic geometric profile of the rock plate surface and the ideal plane, and is used to reflect the overall uniformity of rock particle distribution. The larger the ε, the stronger the oil film adhesion, and the higher the critical flow rate needs to be. The surface heterogeneity dynamic δ characterizes the dynamic response ability of the chemical / wettability heterogeneity of the rock surface, which is defined as the ratio of the wetting contact angle hysteresis to the temperature change rate; High δ: surface wettability is sensitive to temperature changes and can promote dropletization; Low δ: surface chemical properties are stable and the oil film is difficult to peel off; The micro-geometric difference γ describes the degree of discreteness of the micro-roughness features of the surface, which is determined by the ratio of the standard deviation of the surface height distribution to the autocorrelation length; γ≤1: the surface texture is regular, γ≥1: there are sharp protrusions or deep grooves on the surface.

8. An experimental method for studying the mobilization capacity of filmy residual oil, characterized in that: The experiment is carried out using the experimental device as described in any one of claims 1 to 7, comprising the following steps: Assemble the experimental apparatus; Open the transparent cover, lay a layer of oil film on the rock plate in advance to simulate the residual oil, start the hydraulic power assembly to adjust the height of the rock plate to make the elevation of its upper surface consistent; start the film scraper to keep the thickness of the oil film on the rock plate consistent; close the transparent cover after adjustment; Start the displacement component to deliver water into the groove to flush the rock plate, adjust the water flow from low to high, and observe and record the morphological changes of the remaining oil on the surface of the rock plate through the image acquisition module; When the film-like remaining oil on the rock plate changes into oil drop-like remaining oil, record the water flow rate at this time to determine the relationship between the flow rate and the change in the remaining oil morphology; Start the displacement assembly again to deliver the cleaning fluid into the groove of the base to clean the groove and the rock plate; The evaluation formula for the mobilization capacity of film residual oil obtained through experiments is as follows: ； Where: ME —mobilization capacity of film residual oil; A—constant, usually 0.8; Q—flow rate, ml / min; Q c — critical flow; When the flow rate is less than Qc, the oil film remains stable; When the flow rate ≥ Qc, the oil film begins to break and transform into droplets; Relationship between flow rate and mobilization capacity: When the flow rate exceeds Qc, ME is linearly positively correlated with (Q-Qc); the greater the flow rate, the higher the oil film breaking efficiency; The calculation formula of oil film conversion rate R is as follows: ； Where: T—temperature, K; Q—flow rate, ml / min; η—dynamic viscosity of crude oil, mPa·s; h—initial thickness of oil film, μm; γ—oil-water interfacial tension, mN / m; The calculation formula of oil film glass rate OFR is as follows: ； Where: k1 is a constant, with a value of 0.25; T—temperature, K; Q—flow rate, ml / min; η—dynamic viscosity of crude oil, mPa·s; h—initial thickness of oil film, μm; γ—oil-water interfacial tension, mN / m; θ—contact angle; The conclusion drawn from the above formula is: the higher the oil film conversion rate R, the higher the oil film glass rate OFR, and the stronger the residual oil mobilization ability; the lower the oil film conversion rate R, the lower the oil film glass rate OFR, the weaker the residual oil mobilization ability, the more stable the oil film, and the higher the residual oil retention.

9. The experimental method for studying the mobilization capacity of film-like residual oil according to claim 8, characterized in that: When water enters the groove of the base to flush the oil film on the rock plate, the rock plate is heated by a temperature control instrument, and images at different time points are collected by an image acquisition module. During the heating process, the morphological changes of the residual oil are regularly observed and recorded, and the collected images are analyzed by a computer to determine the oil film glass fraction OFR. When the oil film begins to break and transform into droplet-shaped residual oil, the temperature and heating time at this time are recorded, and the oil film conversion rate R is calculated to evaluate the efficiency of the conversion of oil film-shaped residual oil to droplet-shaped residual oil.

10. The experimental method for studying the mobilization capacity of film-like residual oil according to claim 9, characterized in that: Change the oil type of the oil film, observe and record the temperature required for different oil types to transform from oil film to droplet residual oil under water phase conditions, and the critical temperature T of different oil types for film residual oil to droplet c The influence of is derived through the functional relationship between the oil film conversion rate R and the oil film glass rate OFR. The functional relationship is as follows: ； Where: T c —The critical temperature corresponding to the oil type is characterized by the oil type viscosity η, density ρ, and interfacial tension γ; k3—proportional constant, usually 50; η—dynamic viscosity of crude oil, mPa·s; ρ—density of crude oil, g / cm³; cosθ: rock surface wettability, θ is the contact angle.

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