A foam flooding micro-nano chemical chip device and method

Abstract

The present invention relates to a foam flooding micro-nano chemical chip device and method, including a fluid injection device, a foam flooding micro-nano chemical chip and a clamping device thereof, and a microscopic observation device; the fluid injection device is used to inject foam liquid, carbon dioxide gas phase samples, and oil phase samples of oil flooding experiments; the clamping device is used to clamp and load the foam flooding micro-nano chemical chip; the microscopic observation device is used to observe and record the foam manufacturing process and the foam flooding process. The present invention can accurately control the foam gas-liquid ratio, regulate the foam quality, and produce stable foam; directly observe the rheological behavior, migration law, and oil flooding effect of the foam during the foam flooding process. The present invention realizes the integrated continuous operation of foam manufacturing and foam flooding, has high experimental accuracy, good repeatability, simple operation, and short time, and can be used for oil flooding effect evaluation, rapid screening of foaming agents, exploration of oil and gas seepage laws, etc., providing theoretical guidance and basic data support for the study of foam flooding technology.

Description

Technical Field

[0001] The invention relates to a foam oil-flooding micro-nano chemical chip device and method, belonging to the technical field of oil and gas field development. Background Art

[0002] Carbon dioxide foam flooding is an EOR technology that can improve both displacement efficiency and sweep efficiency. The carbon dioxide foam system consists of a foaming agent and CO2. The foaming agent is generally a surfactant with an emulsifying effect, which can improve the wettability of the reservoir environment and reduce the oil-gas interfacial tension. The CO2 gas contained in the foam is easily soluble in crude oil, which can expand the volume of crude oil, reduce viscosity, and improve fluidity, thereby facilitating the use of residual oil to improve displacement efficiency. Foam fluids exhibit high viscosity in macroporous media and are prone to form a Jamin effect during the seepage process at the narrow mouth of the pores. This can inhibit viscous fingering, prevent gas channeling, gravity differentiation, and other phenomena, and selectively block medium and high permeability areas, thereby effectively increasing the swept volume of low permeability areas and improving sweep efficiency.

[0003] Core flooding experiments are commonly used in laboratories to evaluate the effect of foam flooding. However, existing core foam flooding experimental research focuses more on the formulation and performance evaluation of foams, and there is a lack of research on the mechanism and regulation of foam flooding. The core flooding experiment has the following inherent shortcomings. First, this method can only evaluate the flooding effect by collecting the final recovery results of the outflowing crude oil, and there is no way to understand the plugging mechanism, flow law and regulation of foam fluid flooding in porous media; second, this method is also unable to observe the deformation, rupture, aggregation and flow behavior of the foam during the foaming process and the flooding process, and it is impossible to accurately measure the foam quality of the flooding foam, and it is difficult to accurately describe the foam state during the flooding process.

[0004] Microfluidics, also known as "laboratory on a chip" technology, can integrate and transform traditional experimental operation steps into a microfluidics chip physical model for implementation. It has the technical advantages of in-situ visualization, low sample consumption, short experimental time, and inherent safety. There are few reports on experiments on foam flooding based on microfluidics technology, and there are two major problems with existing flooding experiments using microscopic physical models: first, direct injection of gas and foaming agent liquid, the actual flooding process is surfactant flooding or surfactant slug flooding, rather than real foam flooding; second, foam manufacturing and foam flooding experiments are carried out separately in different micro-models, and foam is prone to breakage and aggregation when migrating between multiple devices, making it difficult to form foam with stable foam quality, that is, it is impossible to effectively control the foam fluid. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides a foam flooding micro-nano chemical chip device and method. The present invention can accurately control the foam gas-liquid ratio, regulate the foam quality, and produce stable foam; directly observe the rheological behavior, migration law, and oil displacement effect of the foam during the foam flooding process. The present invention realizes the integrated continuous operation of foam manufacturing and foam flooding, with high experimental accuracy, good repeatability, simple operation, and short time. It can be used for oil displacement effect evaluation, rapid screening of foaming agents, exploration of oil and gas seepage laws, etc., providing theoretical guidance and basic data support for the study of foam flooding technology.

[0006] The technical solution of the present invention is:

[0007] A foam flooding micro-nano chemical chip device, comprising a fluid injection device, a foam flooding micro-nano chemical chip and a clamping device thereof, and a microscopic observation device;

[0008] The fluid injection device is used to inject foam liquid, carbon dioxide gas phase sample, oil phase sample of oil displacement experiment, and accurately control the flow rate of injected fluid or the injection pressure of gas phase sample;

[0009] The clamping device is used to clamp and load the foam flooding micro-nano chemical chip;

[0010] The microscopic observation device is used for observing and recording the foam manufacturing process and the foam oil displacement process.

[0011] Preferably, the foam flooding micro-nano chemical chip comprises a single crystal silicon substrate and a quartz glass cover sheet made by anodic bonding, the single crystal silicon substrate is etched with a micron channel and a through hole for external fluid, and the micron channel is integrated with fluid flow areas connected in sequence, including a gas-liquid slug manufacturing part, a foaming part, a stable foam part, an emptying channel and a porous medium area;

[0012] The gas-liquid slug manufacturing unit comprises a first foam liquid flow channel, a gas phase sample flow channel, and a second foam liquid flow channel; the fluid injection device injects the foam liquid into the first foam liquid flow channel and the second foam liquid flow channel respectively, and the fluid injection device injects the gas phase sample into the gas phase sample flow channel;

[0013] The foaming part utilizes a liquid film separation foaming mechanism to perform foaming;

[0014] The stable foam section is a long-distance single channel;

[0015] The drain channel is used to drain the fluid in the microchannel and inject the unstable foam in the early stage;

[0016] The porous medium region is connected to the stable foam portion and is a foam flooding experimental observation region for exploring the influence of the interaction between the foam size and the flow channel pore-throat ratio on the foam flooding effect.

[0017] Further preferably, the porous medium region includes a porous medium portion with a pore-throat ratio of 3:1, a porous medium portion with a pore-throat ratio of 2:1, and a porous medium portion with a pore-throat ratio of 1:1, which are interconnected.

[0018] Further preferably, expansion openings are provided at the corners downstream of the first foam liquid flow channel and the second foam liquid flow channel.

[0019] Further preferably, a constriction is provided downstream of the gas phase sample flow channel.

[0020] According to a preferred embodiment of the present invention, the fluid injection device comprises a second fluid injection pump, a second high-pressure plunger pump, and a third fluid injection pump;

[0021] The second fluid injection pump is connected to the first foam liquid injection port, and the foam liquid is pumped into the first foam liquid flow channel through the second fluid injection pump; the third fluid injection pump is connected to the second foam liquid injection port, and the foam liquid is pumped into the second foam liquid flow channel through the third fluid injection pump; the second high-pressure plunger pump is connected to the gas phase sample injection port, and the carbon dioxide gas phase sample is pumped into the gas phase sample flow channel through the second high-pressure plunger pump.

[0022] According to the preferred embodiment of the present invention, the foam flooding micro-nano chemical chip device further comprises a first fluid injection pump, an oil phase sample injection and discharge port, a first high-pressure plunger pump and an emptying port;

[0023] One end of the emptying channel is connected to the stable foam portion, and the port at the other end of the emptying channel is an emptying port;

[0024] One end of the porous medium region is connected to the stable foam portion, and the port at the other end of the porous medium region is an oil phase sample injection and discharge port;

[0025] The first fluid injection pump is connected to the oil phase sample injection and discharge port; the first high-pressure plunger pump is connected to the discharge port;

[0026] Preferably, according to the present invention, the microscopic observation device includes a microscope, a CCD camera, an LED light source, and a computer workstation, which are used to observe and record the foam manufacturing process and the foam flooding process;

[0027] The microscope is suspended directly above the foam flooding micro-nano chemical chip to observe the fluid flow in the micron channel of the foam flooding micro-nano chemical chip. The LED light source is coupled to the microscope to provide an irradiation light source for the microscope. The image is acquired in real time through the CCD camera and transmitted to the computer workstation in real time.

[0028] A foam flooding observation and evaluation method is implemented by the foam flooding micro-nano chemical chip device, comprising:

[0029] (1) Preparation: Connect the foam flooding micro-nano chemical chip device;

[0030] Check the air tightness of the foam flooding micro-nano chemical chip device;

[0031] The foam flooding micro-nano chemical chip device is placed in a constant temperature operation box to accurately control the experimental environment temperature;

[0032] Control the temperature in the microchannel of the foam flooding micro-nano chemical chip;

[0033] (2) Foam manufacturing:

[0034] At the experimental environment temperature set in step (1),

[0035] First, the fluid injection device is connected to the gas-liquid slug manufacturing part, and the foam liquid and the carbon dioxide gas phase sample are injected; specifically, the foam liquid is injected into the foam flooding micro-nano chemical chip through the first foam liquid injection port and the second foam liquid injection port at a set flow rate through the third fluid injection pump and the second fluid injection pump respectively; then, the injection gas is injected into the foam flooding micro-nano chemical chip through the gas phase sample injection port at a set flow rate through the second high-pressure plunger pump; the gas flow rate is controlled by adjusting the second high-pressure plunger pump, and the foam liquid flow rate is controlled by adjusting the third fluid injection pump and the second fluid injection pump;

[0036] Secondly, the first high-pressure plunger pump is connected to the piston container to form a back pressure pipeline, and the drain port is connected to adjust the fluid flow rate of the entire microchannel passage; during the foam production, the gas-liquid phase fluid and the foam fluid flow out of the foam flooding micro-nano chemical chip through the drain port via the drain channel;

[0037] Finally, the gas-liquid phase fluid passes through the gas-liquid slug manufacturing section, the foaming section and the foam stabilization section under flow control to complete the foam manufacturing;

[0038] (3) Foam performance evaluation: The foam produced by precise control in step (2) is evaluated for foam performance when it flows through the stable foam section;

[0039] Adjust the microscopic observation device to the stable foam part, and use the bright field mode to record the foam flow process image video; use the image processing software ImageJ to process the image, and calculate the gas phase area S according to the contrast difference of the gas and liquid phases in the foam, that is, the gray value difference. g and liquid area S l , S g +S l =S all , S all is the horizontal cross-sectional area of ​​the entire microchannel in the selected area in the observation area; the gas phase area ratio is the volume ratio S g / S all =V g / Vall , V g V is the volume of gas phase in the microchannel in the selected area of ​​the observation area, all The volume of the entire microchannel in the selected area of ​​the observation area;

[0040] A section of the channel observation area is cut off at the foam stability part, and the foam stability is evaluated by comparing the foam quality at different times in the section;

[0041] Alternatively, the foam size is observed in a section of the channel observation area intercepted from the above-mentioned area, i.e., the foam stabilization part, and the foam stability is also evaluated by measuring the average area of ​​the foam divided by the liquid film and comparing the change of the foam size over time;

[0042] (4) Foam flooding: injecting the oil phase sample into the porous medium area; specifically, the oil phase sample is injected into the porous medium area of ​​the foam flooding experiment by the first fluid injection pump through the oil phase sample injection and discharge port;

[0043] Executing steps (1) and (2) to produce stable foam;

[0044] Implementation of foam flooding experiment:

[0045] The first fluid injection pump is turned off, and the external connection line of the oil phase sample injection and discharge port is switched to be connected to the piston container; at the same time, on the basis of the completion of the above steps (1) and (2), the outlet of the emptying channel, i.e., the emptying port, is closed, so that the foam flows into the porous medium area, i.e., foam flooding is performed; the fluid flow rate of the foam flooding process is adjusted; the interconnected regions with different pore-throat ratios constitute a complete porous medium area, and the influence of the interaction between the foam size and the pore-throat ratio of the flow channel on the foam flooding effect is explored;

[0046] (5) Evaluation of foam flooding effect:

[0047] The microscopic observation device was adjusted to the observation area, i.e., the porous medium area, and the microscopic observation device was adjusted to the bright field mode to observe the rheological behavior, migration law, and oil recovery effect of the foam; during the foam oil recovery process, the microscopic observation device was adjusted to the fluorescence mode, and the fluorescence image was recorded with a constant exposure time for recovery calculation.

[0048] Further preferably, the foam mass N is as shown in formula (I):

[0049]

[0050] Average foam area S ave As shown in formula (II):

[0051]

[0052] S g1It refers to the area of ​​a single bubble in the foam;

[0053] Further preferably, the foam flooding fluorescence image is processed in the image processing software ImageJ, and the oil phase sample and the foam fluid are distinguished according to the gray value difference between the oil phase sample and the foam fluid in the fluorescence image, and the oil phase area S is calculated. oil and the foam fluid area S foam , S oil +S foam =S all , S all It refers to the entire microchannel area in the selected area of ​​the observation area; the recovery factor P is calculated according to the above image data processing results, and the calculation formula is shown in formula (III):

[0054]

[0055] Further preferably, the image processing includes contrast adjustment, threshold adjustment, binarization processing, phase boundary extraction and boundary filling.

[0056] The beneficial effects of the present invention are:

[0057] 1. The method of the present invention can realize the integrated continuous operation of foam manufacturing and foam flooding, and use a variety of foams and a variety of displacement modes to conduct foam flooding effect evaluation experiments;

[0058] 2. The method of the present invention has the advantage of in-situ real-time visualization, and can directly observe the rupture, aggregation and deformation behavior of foam during the foam manufacturing process, as well as the migration law and flooding behavior of foam during the foam flooding process;

[0059] 3. The method of the present invention can accurately control the foam size, foam quality, foam gas-liquid ratio, injection rate and other injection parameters;

[0060] 4. The method of the present invention can conveniently simulate reservoir environments with different porosities and permeabilities to study the foam flooding mechanism and evaluate the flooding effect by changing the design of the porous medium pattern of the flooding chip;

[0061] 5. The oil displacement experiment involved in the method of the present invention directly calculates the recovery rate by statistically analyzing the residual oil distribution, and the data results are true and accurate;

[0062] 6. The method of the present invention can accurately calculate parameters such as foam quality and accurately describe the foam state during foam flooding;

[0063] 7. The method of the present invention has sufficient single-experiment data, and can obtain recovery factor data corresponding to thousands of time points in a single experiment;

[0064] 8. The oil displacement experiment involved in the method of the present invention takes a very short time. Compared with the traditional oil displacement experiment method, multiple experiments can be carried out in the same experimental time, generating several times or even dozens of times of experimental data;

[0065] 9. The method of the present invention consumes very little sample in the experiment, and the experiment can be completed with a few milliliters of liquid sample and tens of milliliters of gas sample;

[0066] 10. The method of the present invention is applicable to a variety of oil phase samples, including crude oil and synthetic oil samples prepared according to demand;

[0067] 11. The oil displacement experiment involved in the method of the present invention can be carried out under the temperature and pressure of most oil reservoir environments;

[0068] 12. The method of the present invention can conveniently evaluate the performance of oil displacement foam, such as: changing the gas and surfactant to produce foams of different properties, exploring the effects of gas type or gas purity, surfactant type or concentration on foam performance; injecting brine with different salinity or pH value, exploring the effects of formation brine salinity or acidity and alkalinity on foam performance;

[0069] 13. The device and method of the present invention are reasonably designed, with a simple operation process, easy standardization, strong controllability, good reliability, and the cost of the equipment used is greatly reduced compared with the traditional core flooding experimental method, and has strong practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 This is a schematic diagram of the design of the foam oil flooding micro-nano chemical chip of the present invention;

[0071] Figure 2 It is a structural schematic diagram of the foam flooding experimental device of the present invention;

[0072] Figure 3 It is a curve diagram showing the relationship between the recovery factor of different pore-throat ratio areas and time in the foam flooding experiment of the embodiment of the present invention;

[0073] Figure 4 It is a structural schematic diagram of the foam oil-flooding micro-nano chemical chip of the present invention.

[0074] Among them, 1. gas-liquid segment plug manufacturing part, 2. foaming part, 3. stable foam part, 4. porous medium part with pore-throat ratio of 3:1, 5. porous medium part with pore-throat ratio of 2:1, 6. porous medium part with pore-throat ratio of 1:1, 7. first foam liquid flow channel, 8. gas phase sample flow channel, 9. second foam liquid flow channel, 10. piston container, 11. first pressure sensor, 12. second pressure sensor, 13. first high-pressure plunger pump, 14. second high-pressure plunger pump, 15. first fluid injection pump, 16. second fluid injection pump, 17. third fluid injection pump, 18. first foam liquid injection port, 19. gas phase sample injection port, 20. second foam liquid injection port, 21. oil phase sample injection and discharge port, 22. emptying port. DETAILED DESCRIPTION

[0075] The present invention is further described below with reference to the accompanying drawings and specific embodiments, but is not limited thereto.

[0076] Example 1

[0077] A foam flooding micro-nano chemical chip device, comprising a fluid injection device, a foam flooding micro-nano chemical chip and a clamping device thereof, and a microscopic observation device;

[0078] The fluid injection device is used to inject foam liquid (mixture of ultrapure water and surfactant), carbon dioxide gas phase samples, and oil phase samples for oil displacement experiments, and accurately control the flow rate of the injected fluid or the injection pressure of the gas phase sample;

[0079] The clamping device is used to clamp and load the foam flooding micro-nano chemical chip; the clamping device, for example, is a temperature-controlled and pressure-resistant clamping device for a high-throughput visualization microfluidic chip disclosed in Chinese patent document CN111701631A.

[0080] The microscopic observation device is used to observe and record the foam manufacturing process and the foam flooding process.

[0081] Example 2

[0082] The difference of the foam flooding micro-nano chemical chip device described in Example 1 is that:

[0083] like Figure 4 As shown in FIG. 1 , the foam flooding micro-nano chemical chip includes a single crystal silicon substrate and a quartz glass cover sheet made by anodic bonding. The single crystal silicon substrate is etched with micron channels and through holes for external fluids. The micron channels are integrated with fluid flow areas that are sequentially connected, including a gas-liquid slug manufacturing part 1, a foaming part 2, a stable foam part 3, an emptying channel and a porous medium area. The foam flooding micro-nano chemical chip integrates the devices and pipelines used in traditional foam flooding experiments into the micron channels of the micro-nano chemical chip, such as Figure 1 As shown, accurate and rapid feedback of the experimental fluid on temperature and pressure is achieved.

[0084] The gas-liquid slug manufacturing unit 1 comprises a first foam liquid flow channel 7, a gas phase sample flow channel 8, and a second foam liquid flow channel 9; the fluid injection device injects the foam liquid into the first foam liquid flow channel 7 and the second foam liquid flow channel 9 respectively, and the fluid injection device injects the gas phase sample into the gas phase sample flow channel 8;

[0085] The dimensions of the first foam liquid flow channel 7 and the second foam liquid flow channel 9, the dimension of the gas phase sample flow channel 8, and the dimension of the foam flow channel downstream of the gas-liquid slug manufacturing part 1 are all 200 μm in width and 10 μm in depth; the width of the narrowest part of the downstream constriction of the gas phase sample flow channel 8 in the gas-liquid slug manufacturing part 1 is 50 μm, and the expansion width of the downstream channel changes from 100 μm to 200 μm.

[0086] The foaming section 2 uses the lamellae division foaming mechanism to foam; the gas-liquid slug formed by the gas-liquid slug manufacturing section 1 continuously collides with the hexagonal base particles in the foaming section 2 area, and the liquid phase slug is divided into liquid films, which are further divided into more and thinner liquid films, and the amount of foam increases rapidly. The symmetrical design of the flow channel of the foaming section 2 is conducive to the formation of uniform-sized foam. The channel size of the foaming section 2 is 50 μm wide and 10 μm deep.

[0087] The stable foam section 3 is a long U-shaped curved single channel. The long single channel design prolongs the residence time of the foam in the microchannel. The foam generated in the foaming stage undergoes a series of ruptures and coalescences in the long single channel in this area to form stable foam. In this area, the foam state can be observed and recorded, the foam quality can be calculated, and the foam performance can be evaluated.

[0088] The drain channel is used to drain the fluid in the microchannel and inject the unstable foam in the early stage;

[0089] The porous medium area is connected to the stable foam part 3, which is the observation area of ​​the foam flooding experiment, and is used to explore the effect of the interaction between the foam size and the pore-throat ratio of the flow channel on the foam flooding effect. The channel size of the porous medium area is 50 μm wide and 10 μm deep.

[0090] The porous media area includes a porous media section 4 with a pore-throat ratio of 3:1, a porous media section 5 with a pore-throat ratio of 2:1, and a porous media section 6 with a pore-throat ratio of 1:1, which are interconnected. The diameter of the circular hole (pore belly) at the intersection of the flow channels in the porous media section 5 with a pore-throat ratio of 2:1 is 100 μm, and the diameter of the circular hole (pore belly) at the intersection of the flow channels in the porous media section 4 with a pore-throat ratio of 3:1 is 150 μm; the size of the fluid distribution flow channel before and after the porous media area is 200 μm wide and 10 μm deep. The design of different pore-throat ratio areas in the porous media area can be used to explore the effect of the interaction between the foam size and the pore-throat ratio of the flow channel on the foam flooding effect. The pore-throat ratio is the ratio of the width at the widest point to the width at the narrowest point in the microchannel. The pore-throat ratio is an experimental research variable. The difference in oil displacement efficiency of foams of fixed size in different pore-throat ratio areas is compared to explore the effect of pore-throat ratio on the oil displacement effect of foams of fixed size. The porous medium region refers to a certain area in which some interconnected microchannels are designed. The interconnected microchannels can better simulate the pores of porous media such as oil reservoir rock formations, so this area is called the porous medium region. The channel pattern design of this area can be changed according to the experimental purpose.

[0091] Expanders are provided at the corners downstream of the first foam liquid flow channel 7 and the second foam liquid flow channel 9. This reduces the angle of the corners, which is beneficial for cutting off the liquid phase fluid by using the snap-off effect to produce a liquid phase slug.

[0092] A constriction is provided downstream of the gas phase sample flow channel 8. The setting of the constriction enables the gas to form a jet flow when it flows out, which is used to create local turbulence, which is conducive to cutting off the liquid phase fluid and further promoting the formation of gas-liquid slugs.

[0093] Example 3

[0094] The difference of the foam flooding micro-nano chemical chip device according to Example 2 is that:

[0095] The fluid injection device includes a second fluid injection pump 16, a second high-pressure plunger pump 14, and a third fluid injection pump 17;

[0096] The second fluid injection pump 16 is connected to the first foam liquid injection port 18 through a ball valve, and the foam liquid is pumped into the first foam liquid flow channel 7 through the second fluid injection pump 16; the third fluid injection pump 17 is connected to the second foam liquid injection port 20 through a ball valve, and the foam liquid is pumped into the second foam liquid flow channel 9 through the third fluid injection pump 17; the CO2 gas cylinder, the second high-pressure plunger pump 14, the ball valve, the first pressure sensor 11, the ball valve, and the gas phase sample injection port 19 are connected in sequence, and the carbon dioxide gas phase sample is pumped into the gas phase sample flow channel 8 through the second high-pressure plunger pump 14.

[0097] The foam flooding micro-nano chemical chip device also includes a first fluid injection pump 15, an oil phase sample injection and discharge port 21, a first high-pressure plunger pump 13 and an exhaust port 22;

[0098] One end of the emptying channel is connected to the stable foam portion 3, and the port at the other end of the emptying channel is an emptying port 22;

[0099] One end of the porous medium region is connected to the stable foam portion 3, and the port at the other end of the porous medium region is an oil phase sample injection and discharge port 21;

[0100] The first fluid injection pump 15 is connected to the oil phase sample injection and discharge port 21; the first high-pressure plunger pump 13 is connected to the discharge port 22;

[0101] The oil phase sample injection and discharge port 21 is externally connected to a tee, the tee outlet branch 1 is successively connected to a ball valve and a first fluid injection pump 15, the tee outlet branch 2 is successively connected to a ball valve, and the tee outlet branch 3 is connected to a tee, a piston container 10, a ball valve, a second pressure sensor 12, a ball valve, a first high-pressure plunger pump 13, and a CO2 gas cylinder;

[0102] The external pipeline of the exhaust port 22 is successively connected to the ball valve, and is connected to the tee, the piston container 10, the ball valve, the second pressure sensor 12, the ball valve, the first high-pressure plunger pump 13, and the CO2 cylinder as a branch.

[0103] Example 4

[0104] The difference of the foam flooding micro-nano chemical chip device described in Example 3 is that:

[0105] The microscopic observation device includes a microscope, a CCD camera, an LED light source, and a computer workstation, which are used to observe and record the foam manufacturing process and the foam flooding process;

[0106] The microscope is suspended directly above the foam flooding micro-nano chemical chip to observe the fluid flow in the micron channel of the foam flooding micro-nano chemical chip. The LED light source is coupled in the microscope to provide the microscope with a light source. The image is acquired in real time through the CCD camera and transmitted to the computer workstation in real time. The computer workstation is a high-performance desktop computer used for high-quality graphic display, high-speed large-capacity cache and image calculation and processing.

[0107] In the foam performance evaluation, the microscope is adjusted to the bright field mode, and the observation area of ​​the microscope is adjusted to the stable foam part 3 to observe and record the foam state; the light source intensity is 100%, and the exposure time is 10μs. In the foam oil recovery experiment, the microscope device is in fluorescence mode, and the output light source is adjusted to 460nm-550nm fluorescence excitation light, the light source intensity is 100%, and the exposure time is 50ms. The microscope observation area is adjusted to the porous medium area, the rheological behavior, migration law, and oil recovery effect of the foam are observed, and the fluorescence image video is recorded at a constant exposure time; the bright field mode refers to the observation condition under which the light source of the microscope is full-frequency white light without intervention. The fluorescence mode refers to the observation condition under which the LED light source is converted into a specific wavelength of excitation light that is easy to fully excite the fluorescence effect of oil phase samples such as crude oil through a filter.

[0108] Example 5

[0109] A foam flooding observation and evaluation method is implemented by the foam flooding micro-nano chemical chip device described in Example 4, comprising:

[0110] (1) Preparation: Connect the foam flooding micro-nano chemical chip device;

[0111] Before the observation and evaluation of foam flooding, the equipment is connected first: the foam flooding micro-nano chemical chip is loaded into the clamping device;

[0112] like Figure 2 As shown, the second fluid injection pump 16 is connected to the first foam liquid injection port 18, the third fluid injection pump 17 is connected to the second foam liquid injection port 20, the second high-pressure plunger pump 14 is connected to the gas phase sample injection port 19, the first fluid injection pump 15 is connected to the oil phase sample injection and discharge port 21, the first high-pressure plunger pump 13 is connected to the emptying port 22, and all connections between the fluid injection device and the foam oil-flooding micro-nano chemical chip and its clamping device are completed. After loading the foam oil-flooding micro-nano chemical chip and the connecting pipeline, check the air tightness of the foam oil-flooding micro-nano chemical chip device; connect the external pipeline of the second foam liquid injection port 20, set the pressure of the second high-pressure plunger pump 14 to 1Mpa, output CO2 gas at a constant pressure, observe the reading of the second pressure sensor 12, and the reading of the second pressure sensor 12 remains unchanged within 5 minutes, which means that the air tightness is good.

[0113] The foam flooding micro-nano chemical chip device was placed in a constant temperature operation box to precisely control the experimental environment temperature, which was set at 25°C.

[0114] The foam flooding micro-nano chemical chip and the clamping device are externally connected to a temperature sensor and a circulating constant temperature water bath to further control the temperature in the microchannel of the foam flooding micro-nano chemical chip to 25°C; due to the high thermal conductivity of silicon, the trace fluid passed into the foam flooding micro-nano chemical chip can achieve heat transfer equilibrium within a few minutes.

[0115] (2) Foam manufacturing:

[0116] At the experimental environment temperature set in step (1), a foam liquid sample is prepared. In this embodiment, 0.1 wt % sodium dodecyl sulfate (SDS) is used as a surfactant and dissolved in ultrapure water to obtain a foam liquid sample;

[0117] First, the fluid injection device is connected to the gas-liquid slug manufacturing part 1, and the foam liquid and the carbon dioxide gas phase sample are injected; specifically, the foam liquid is injected into the foam oil-flooding micro-nano chemical chip through the third fluid injection pump 17 and the second fluid injection pump 16 at a flow rate of 0.0005 mL / min through the first foam liquid injection port 18 and the second foam liquid injection port 20 respectively; then, the injected gas is injected through the second high-pressure plunger pump 14 at a flow rate of 0.001 mL / min through Figure 2 The gas sample injection port 19 shown is injected into the foam flooding micro-nano chemical chip; the gas flow rate is controlled by adjusting the second high-pressure plunger pump 14, and the foam liquid flow rate is controlled by adjusting the third fluid injection pump 17 and the second fluid injection pump 16; that is, the foam liquid is injected at a certain gas-liquid ratio. The gas-liquid two-phase flow ratio, that is, the length ratio of the gas-liquid slug formed in the foaming part 2, is controlled by adjusting the second high-pressure plunger pump 14, the third fluid injection pump 17 and the second fluid injection pump 16; in this embodiment, the gas-liquid two-phase fluid passes through the gas-liquid slug manufacturing part 1 under the above-mentioned flow control to form a gas-liquid slug with a length ratio of 3.5:1, which forms a stable foam after flowing through the foaming part 2 and the stable foam part 3;

[0118] Secondly, the first high-pressure plunger pump 13 is connected to the piston container 10 to form a back pressure pipeline, and the emptying port 22 is connected to adjust the front-to-back pressure difference of the entire microchannel passage. In this embodiment, the front-to-back pressure difference of the entire microchannel passage is 0.05 MPa; during the foam production, the gas-liquid phase fluid and the foam fluid flow out of the foam flooding micro-nano chemical chip through the emptying channel and the emptying port 22;

[0119] Finally, the gas-liquid phase fluid passes through the gas-liquid slug manufacturing part 1, the foaming part 2 and the foam stabilizing part 3 under flow control to complete the foam manufacturing;

[0120] (3) Foam performance evaluation: The foam produced by precise control in step (2) is evaluated for foam performance when it flows through the stable foam section 3;

[0121] Adjust the microscopic observation device to the stable foam part 3, use the bright field mode with an exposure time of 10 μs and a shooting interval of 1 s to record the foam flow process in real time; use the image processing software ImageJ to process the image, and calculate the gas phase area S according to the contrast difference of the gas and liquid phases in the foam, that is, the gray value difference. g and liquid area S lIn the experimental data image, the grayscale value of the bubbles in the foam, i.e. the gas phase area, is obviously different from the grayscale value of the surfactant film, i.e. the liquid phase area. After the binarization process of the ImageJ image processing software, the grayscale value of the pixels in the bubble, i.e. the gas phase area, is 255, which is white; while the grayscale value of the pixels in the surfactant film, i.e. the liquid phase area, is 0, which is black. The area of ​​the area with a grayscale value of 255, i.e. the gas phase area of ​​the bubbles in the foam, S, is counted using the surface statistics function of the ImageJ image processing software. g The area of ​​the region with gray value 0 is the liquid phase area S of the foam liquid film in the foam. l . S g +S l =S all , S all is the horizontal cross-sectional area of ​​the entire microchannel in the selected area of ​​the observation area; since the etching depth of the microchannels in the foam flooding chip is consistent, it can be considered that the gas phase area ratio is the volume ratio S g / S all =V g / V all , V g V is the volume of gas phase in the microchannel in the selected area of ​​the observation area, all The volume of the entire microchannel in the selected area of ​​the observation area;

[0122] A section of the channel observation area is intercepted at the foam stabilization part, and the foam stability is evaluated by comparing the foam quality in the section at different times; or the foam size is observed in a section of the channel observation area intercepted at the foam stabilization part, and the foam stability is evaluated by measuring the average area of ​​the foam divided by the liquid film and comparing the change of the foam size over time;

[0123] The foam quality N is shown in formula (I):

[0124]

[0125] N = Vg / Vall×100% = Sg / Sall×100%, the foam quality at the observation time of 10s was measured to be 87.935%, and the foam quality at the observation time of 60s was measured to be 88.245%, and the foam stability was good;

[0126] Average foam area S ave As shown in formula (II):

[0127]

[0128] S g1 It refers to the area of ​​a single bubble in the foam. The average foam area at the observation time of 10s is 346.36μm 2The average foam area at 60s was 359.68μm 2 The average foam area size changed by 3.7%, and the foam stability was good.

[0129] (4) Foam flooding: injecting the oil phase sample into the porous medium area; specifically, the oil phase sample is injected into the porous medium area of ​​the foam flooding experiment by the first fluid injection pump 15 through the oil phase sample injection and discharge port 21;

[0130] After the porous medium region is filled with the oil phase sample, the ball valve downstream of the first fluid injection pump 15 is closed;

[0131] Adjust the constant temperature operating box and circulating constant temperature water bath to accurately control the experimental temperature to 25℃;

[0132] Prepare an oil phase sample, prepare a decane sample with 1wt% Nile red as a fluorescent agent, inject the oil phase sample into the porous medium area of ​​the foam flooding experiment through the oil phase sample injection and discharge port 21 by the first fluid injection pump 15 at a flow rate of 0.1mL / min, and close the ball valve downstream of the first fluid injection pump 15 after the porous medium area is filled with the oil phase sample;

[0133] Executing steps (1) and (2) to produce stable foam;

[0134] Implementation of foam flooding experiment:

[0135] Close the ball valve downstream of the first fluid injection pump 15, and switch the external connection line of the oil phase sample injection and discharge port 21 to connect it to the piston container 10; at the same time, based on the completion of the above steps (1) and (2), close the valve on the external pipe line of the emptying channel outlet, i.e., the emptying port 22, so that the foam flows into the porous medium area, i.e., foam flooding is performed; at this time, the first high-pressure plunger pump 13 is connected to the back pressure pipeline formed by the piston container 10 to connect the oil phase sample injection and discharge port 21, so as to adjust the fluid flow rate of the foam flooding process; The plunger pump 13 is connected to the piston container 10 to form a back pressure pipeline connected to the drain port 22 for adjusting the front-to-back pressure difference of the entire microchannel passage. In this embodiment, the front-to-back pressure difference of the entire microchannel passage is 0.05MPa; the interconnected different pore-throat ratio areas constitute a complete porous medium area, and the influence of the interaction between foam size and flow channel pore-throat ratio on the foam flooding effect is explored; the porous medium pattern design can be changed according to experimental needs to simulate oil reservoir environments with different porosities and multiple permeabilities to conduct foam oil recovery mechanism research and evaluate the oil recovery effect.

[0136] (5) Evaluation of foam flooding effect:

[0137] Adjust the microscopic observation device to the observation area, i.e., the porous medium area, and adjust the microscopic observation device to the bright field mode to observe the rheological behavior, migration law, and oil displacement effect of the foam; during the foam flooding process, adjust the microscopic observation device to the fluorescence mode, and record the fluorescence image with an exposure time of 50 ms and a shooting time interval of 1 s for recovery calculation.

[0138] The oil phase sample or crude oil itself with added fluorescent display agent has fluorescence effect and appears white under the excitation light of specific wavelength in fluorescence mode. The foam fluid (containing surfactant and gas phase sample) has no fluorescence effect and appears black. The foam flooding fluorescence image is processed in the image processing software ImageJ. The oil phase sample and the foam fluid are distinguished according to the gray value difference between the oil phase sample and the foam fluid in the fluorescence image, and the oil phase area S is calculated. oil and the foam fluid area S foam , S oil +S foam =S all , S all It refers to the entire microchannel area in the selected area of ​​the observation area; the recovery factor P is calculated according to the above image data processing results, and the calculation formula is shown in formula (III):

[0139]

[0140] In the fluorescence observation mode, the oil phase appears bright white, and the grayscale value of the pixels in the oil phase area is significantly higher than the grayscale value of the pixels in the foam area without fluorescence signals. After the binarization process of ImageJ image processing software, the grayscale value of the pixels in the oil phase area is 255, which appears white; the grayscale value of the pixels in the foam area is 0, which appears black. The area calculation function of ImageJ image processing software is used to calculate the area of ​​the area with a grayscale value of 255, that is, the oil phase area S. oil The area of ​​the region with gray value 0 is the foam fluid area S foam .

[0141] Image processing includes contrast adjustment, threshold adjustment, binarization, phase boundary extraction and boundary filling.

[0142] According to the above image data processing results, a curve diagram of the relationship between the recovery rate of different porous media areas and time is drawn, such as Figure 3 As shown, the final recovery rate of the porous medium section 4 with a pore-throat ratio of 3:1 is 74.1%, the final recovery rate of the porous medium section 5 with a pore-throat ratio of 2:1 is 80.5%, and the final recovery rate of the porous medium section 6 with a pore-throat ratio of 1:1 is 91.0%.

[0143] The foam flooding observation and evaluation method of the present invention compares the final recovery rate data of foams with different foam qualities in porous media areas with different pore-throat ratios, explores the influence of foam quality, pore-throat ratio and the relationship between the two on the recovery rate, evaluates the foam flooding effect, and optimizes foam injection parameters to improve the recovery rate of reservoir areas with different pore-throat ratios in the oil reservoir.

Claims

1. A foam flooding micro-nano chemical chip device, characterized in that: It includes a fluid injection device, a foam flooding micro-nano chemical chip and its clamping device, and a microscopic observation device; The fluid injection device is used to inject foam liquid, carbon dioxide gas phase sample, oil phase sample of oil displacement experiment, and accurately control the flow rate of injected fluid or the injection pressure of gas phase sample; The clamping device is used to clamp and load the foam flooding micro-nano chemical chip; The microscopic observation device is used to observe and record the foam manufacturing process and the foam flooding process; The foam flooding micro-nano chemical chip comprises a single crystal silicon substrate and a quartz glass cover sheet made by anodic bonding, the single crystal silicon substrate is etched with a micron channel and a through hole for external fluid, and the micron channel is integrated with fluid flow areas connected in sequence, including a gas-liquid slug manufacturing part, a foaming part, a stable foam part, an emptying channel and a porous medium area; The gas-liquid slug manufacturing unit comprises a first foam liquid flow channel, a gas phase sample flow channel, and a second foam liquid flow channel; the fluid injection device injects the foam liquid into the first foam liquid flow channel and the second foam liquid flow channel respectively, and the fluid injection device injects the gas phase sample into the gas phase sample flow channel; The foaming part utilizes a liquid film separation foaming mechanism to perform foaming; The stable foam section is a long-distance single channel; The drain channel is used to drain the fluid in the microchannel and inject the unstable foam in the early stage; The porous medium region is connected to the stable foam portion and is a foam flooding experimental observation region for exploring the influence of the interaction between the foam size and the flow channel pore-throat ratio on the foam flooding effect.

2. A foam flooding micro-nano chemical chip device according to claim 1, characterized in that: The porous medium region includes a porous medium portion with a pore-throat ratio of 3:1, a porous medium portion with a pore-throat ratio of 2:1, and a porous medium portion with a pore-throat ratio of 1:1, which are interconnected.

3. A foam flooding micro-nano chemical chip device according to claim 1, characterized in that: Expanding openings are arranged at the corners of the first foam liquid flow channel and the second foam liquid flow channel downstream.

4. A foam flooding micro-nano chemical chip device according to claim 1, characterized in that: A constriction is arranged downstream of the gas phase sample flow channel.

5. A foam flooding micro-nano chemical chip device according to claim 1, characterized in that: The fluid injection device comprises a second fluid injection pump, a second high-pressure plunger pump, and a third fluid injection pump; The second fluid injection pump is connected to the first foam liquid injection port, and the foam liquid is pumped into the first foam liquid flow channel through the second fluid injection pump; The third fluid injection pump is connected to the second foam liquid injection port, and the foam liquid is pumped into the second foam liquid flow channel through the third fluid injection pump; the second high-pressure plunger pump is connected to the gas phase sample injection port, and the carbon dioxide gas phase sample is pumped into the gas phase sample flow channel through the second high-pressure plunger pump.

6. A foam flooding micro-nano chemical chip device according to claim 5, characterized in that: The foam flooding micro-nano chemical chip device also includes a first fluid injection pump, an oil phase sample injection and discharge port, a first high-pressure plunger pump and an emptying port; One end of the emptying channel is connected to the stable foam portion, and the port at the other end of the emptying channel is an emptying port; One end of the porous medium region is connected to the stable foam portion, and the port at the other end of the porous medium region is an oil phase sample injection and discharge port; The first fluid injection pump is connected to the oil phase sample injection and discharge port; the first high-pressure plunger pump is connected to the discharge port.

7. A foam flooding micro-nano chemical chip device according to claim 6, characterized in that: The microscopic observation device includes a microscope, a CCD camera, an LED light source, and a computer workstation, which are used to observe and record the foam manufacturing process and the foam flooding process; The microscope is suspended directly above the foam flooding micro-nano chemical chip to observe the fluid flow in the micron channel of the foam flooding micro-nano chemical chip. The LED light source is coupled to the microscope to provide an irradiation light source for the microscope. The image is acquired in real time through the CCD camera and transmitted to the computer workstation in real time.

8. A foam flooding observation and evaluation method, implemented by the foam flooding micro-nano chemical chip device according to claim 7, characterized in that: include: (1) Preparation: Connect the foam flooding micro-nano chemical chip device; Check the air tightness of the foam flooding micro-nano chemical chip device; The foam flooding micro-nano chemical chip device is placed in a constant temperature operation box to accurately control the experimental environment temperature; Control the temperature in the microchannel of the foam flooding micro-nano chemical chip; (2) Foam manufacturing: At the experimental environment temperature set in step (1), First, the fluid injection device is connected to the gas-liquid slug manufacturing part, and the foam liquid and the carbon dioxide gas phase sample are injected; specifically, the foam liquid is injected into the foam flooding micro-nano chemical chip through the first foam liquid injection port and the second foam liquid injection port at a set flow rate through the third fluid injection pump and the second fluid injection pump respectively; then, the injection gas is injected into the foam flooding micro-nano chemical chip through the gas phase sample injection port at a set flow rate through the second high-pressure plunger pump; the gas flow rate is controlled by adjusting the second high-pressure plunger pump, and the foam liquid flow rate is controlled by adjusting the third fluid injection pump and the second fluid injection pump; Secondly, the first high-pressure plunger pump is connected to the piston container to form a back pressure pipeline, and the drain port is connected to adjust the fluid flow rate of the entire microchannel passage; during the foam production, the gas-liquid phase fluid and the foam fluid flow out of the foam flooding micro-nano chemical chip through the drain port via the drain channel; Finally, the gas-liquid phase fluid passes through the gas-liquid slug manufacturing section, the foaming section and the foam stabilization section under flow control to complete the foam manufacturing; (3) Foam performance evaluation: The foam produced by precise control in step (2) is evaluated for foam performance when it flows through the stable foam section; Adjust the microscopic observation device to the stable foam part, and use the bright field mode to record the foam flow process image video; use the image processing software ImageJ to process the image, and calculate the gas phase area S according to the contrast difference of the gas and liquid phases in the foam, that is, the gray value difference. g and liquid area S l , S g +S l =S all , S all is the horizontal cross-sectional area of ​​the entire microchannel in the selected area in the observation area; the gas phase area ratio is the volume ratio S g / S all =V g / V all , V g V is the volume of gas phase in the microchannel in the selected area of ​​the observation area, all The volume of the entire microchannel in the selected area within the observation area; A section of the channel observation area is cut off at the foam stability part, and the foam stability is evaluated by comparing the foam quality at different times in the section; Alternatively, the foam size is observed in the above-mentioned area, i.e., a section of the channel observation area intercepted by the foam stabilization portion, and the foam stability is also evaluated by measuring the average area of ​​the foam divided by the liquid film and comparing the change of the foam size over time; (4) Foam flooding: injecting the oil phase sample into the porous medium area; specifically, the oil phase sample is injected into the porous medium area of ​​the foam flooding experiment by the first fluid injection pump through the oil phase sample injection and discharge port; Executing steps (1) and (2) to produce stable foam; Implementation of foam flooding experiment: The first fluid injection pump is turned off, and the external connection line of the oil phase sample injection and discharge port is switched to be connected to the piston container; at the same time, on the basis of the completion of the above steps (1) and (2), the outlet of the emptying channel, i.e., the emptying port, is closed, so that the foam flows into the porous medium area, i.e., foam flooding is performed; the fluid flow rate of the foam flooding process is adjusted; the interconnected regions with different pore-throat ratios constitute a complete porous medium area, and the influence of the interaction between the foam size and the pore-throat ratio of the flow channel on the foam flooding effect is explored; (5) Evaluation of foam flooding effect: The microscopic observation device was adjusted to the observation area, i.e., the porous medium area, and the microscopic observation device was adjusted to the bright field mode to observe the rheological behavior, migration law, and oil recovery effect of the foam; during the foam oil recovery process, the microscopic observation device was adjusted to the fluorescence mode, and the fluorescence image was recorded with a constant exposure time for recovery calculation.

9. A foam flooding observation and evaluation method according to claim 8, characterized in that: The foam quality N is shown in formula (I): Average foam area S ave As shown in formula (II): S g1 It refers to the area of ​​a single bubble in the foam.

10. A foam flooding observation and evaluation method according to claim 8, characterized in that: The foam flooding fluorescence images were processed in the image processing software ImageJ. The oil phase samples and foam fluids were distinguished according to the gray value difference between the oil phase samples and foam fluids in the fluorescence images, and the oil phase area S was calculated. oil and the foam fluid area S foam , S oil +S foam =S all , S all It refers to the entire microchannel area in the selected area of ​​the observation area; the recovery factor P is calculated according to the above image data processing results, and the calculation formula is shown in formula (III):

11. A foam flooding observation and evaluation method according to any one of claims 8 to 10, characterized in that: Image processing includes contrast adjustment, threshold adjustment, binarization, phase boundary extraction and boundary filling.

Images