Microscopic visualization system for simulating micro-fluidic displacement of low-permeability reservoir

Abstract

The invention discloses a microcosmic visualization system for simulating micro-fluidic displacement of a low-permeability reservoir, and relates to the technical field of oil and gas reservoir engineering, the microcosmic visualization system comprises a console, a microcosmic visualization high-temperature and high-pressure kettle, a gas-liquid pressurization system and a micro-fluidic chip; wherein the console is connected with the microcosmic visual high-temperature and high-pressure kettle through an electric lead; the console is connected with the gas-liquid pressurization system through an electric wire. The microcosmic visual high-temperature and high-pressure kettle is connected with the gas-liquid pressurization system through a gas-liquid pipeline; the micro-fluidic chip can be directly placed in a microcosmic visual high-temperature and high-pressure kettle. Through a glass wet etching-hot pressing bonding micro-model manufacturing technology, a microscopic seepage visualization experiment system is provided aiming at the low-permeability reservoir conditions of the Changqing oil field, trapping and observation of related information that water and oil are close to a real stratum environment are achieved, simulation and research of a low-permeability reservoir imbibition physical rule are facilitated, and the experimental system has a good application prospect. The method has important scientific significance and industrial value for improving the recovery ratio of an oil field.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas reservoir engineering, and particularly to a microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs. Background Art

[0002] The technology of deep tapping potential and enhancing oil recovery in old oilfields is an important guarantee for the stable production of oilfields. The geological reserves exploited in the low-permeability oil reservoirs in Changqing account for 18.4%, and the annual oil production accounts for 26.5%, which are important components for the stable production and increased production of the Changqing Oilfield. The waterflooding calibrated oil recovery in low-permeability oil reservoirs is relatively low (23.4%), and it is in the middle-high water cut development stage, which is the main battlefield for enhancing oil recovery in old oilfields. Basic research on the imbibition physical laws of low-permeability reservoir rocks has important scientific significance and industrial value for oilfields to enhance oil recovery. Existing displacement devices for simulating formation imbibition have problems such as being non-visual, difficult to conduct quantitative research, unable to withstand high temperature and high pressure, and relatively large simulated pore scales, making it difficult to simulate the true formation conditions of low-permeability reservoir rocks, resulting in a large error between the simulation results and the actual laws of formation imbibition displacement. In this paper, aiming at the actual formation parameters of low-permeability reservoirs in Changqing, a microscopic seepage visualization experimental system is provided, which improves the above problems and realizes the capture and observation of relevant information of water and oil close to the true formation environment of low-permeability reservoirs, contributing to the simulation and research of the imbibition physical laws of low-permeability oil reservoirs.

[0003] Patent document CN109827884B discloses "a true sandstone high-temperature and high-pressure visualization seepage experiment device and method". This device can carry out visualization seepage mechanism experiments, but the microscopic visualization model used is processed from true sandstone, and its light transmittance is poor, making it difficult to conduct quantitative experiments.

[0004] Patent document CN112730196A discloses "a high-temperature and high-pressure microscopic visualization flow device and experimental method". This device can conduct visualization experiments of oil-water mutual displacement to statistically obtain the microscopic displacement efficiency of the core, but it cannot achieve the micro-nano level.

[0005] Patent document CN110715889A discloses "a porous medium low-pressure displacement microscopic visualization observation system", which is a porous medium low-pressure displacement microscopic visualization observation system that can simultaneously realize dual monitoring of flow rate and pressure while controlling the flow rate or pressure of microfluids in the porous medium, but it cannot simulate displacement under high-pressure environments.

[0006] Patent application number CN114272963A discloses "a microscopic visualization chip, experimental device and method for simulating CO2 huff and puff", which introduces a microscopic visualization chip for simulating the actual pore throat structure area of shale pore structure, but it cannot withstand high temperature and high pressure.

[0007] Currently, only the above-mentioned similar technologies have been retrieved. The existing patent methods mainly have the following problems: (1) The conventional micro-visualization displacement system at normal temperature and pressure cannot withstand high temperature and pressure and cannot simulate the situation under real formation conditions; (2) The high-temperature and high-pressure visualization seepage experiment device cannot be combined with a visual micro-model, has poor light transmittance, and is difficult to conduct quantitative experiments. (3) The pore scale of the micro-model chip is relatively large, and there is a gap in the simulation within the micro-scale confined space of the formation. Summary of the Invention

[0008] The object of the present invention is to provide a micro-visualization system for simulating microfluidic displacement in low-permeability reservoirs. Through the glass wet etching-thermocompression bonding micro-model manufacturing technology, aiming at the low-permeability reservoir conditions in the Changqing Oilfield, a micro-seepage visualization experiment system is provided, which realizes the capture and observation of relevant information of water and oil close to the real formation environment, helps to simulate and study the imbibition physical laws in low-permeability oil reservoirs, and has important scientific significance and industrial value for improving the oil recovery rate in oilfields.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] The present invention provides a micro-visualization system for simulating microfluidic displacement in low-permeability reservoirs. The system includes: a console, a micro-visualization high-temperature and high-pressure autoclave, a gas-liquid pressurization system, and a microfluidic chip; wherein,

[0011] The console is connected to the micro-visualization high-temperature and high-pressure autoclave through an electric wire;

[0012] The console is connected to the gas-liquid pressurization system through an electric wire;

[0013] The micro-visualization high-temperature and high-pressure autoclave is connected to the gas-liquid pressurization system through a gas-liquid pipeline;

[0014] The microfluidic chip can be directly placed inside the micro-visualization high-temperature and high-pressure autoclave.

[0015] Furthermore, the console includes a computer; the computer is used to control the gas-liquid pressurization system, push the liquid into the microfluidic chip in the micro-visualization high-temperature and high-pressure autoclave, and then conduct a displacement experiment.

[0016] Furthermore, the micro-visualization high-temperature and high-pressure autoclave includes: a visual chamber, a confining pressure pump, a backpressure valve, a buffer, and a backpressure pump; wherein,

[0017] The visual chamber is connected to the confining pressure pump through a gas-liquid pipeline;

[0018] The confining pressure pump and the backpressure pump are connected to the computer through an electric wire;

[0019] The visual chamber is connected to the backpressure pump through a gas-liquid pipeline, and a backpressure valve and a buffer are sequentially arranged between the visual chamber and the backpressure pump.

[0020] Further, the gas-liquid boosting system includes: a piston container, an ISCO pump, a pressure regulating valve, a safety valve, a gas storage tank, and a boosting pump; wherein,

[0021] The ISCO pump, the boosting pump, and the computer are connected by electric wires.

[0022] The ISCO pump is connected to the piston container through a gas-liquid pipeline, and the piston container is connected to the visual chamber through a gas-liquid pipeline.

[0023] The pressure regulating valve, the gas storage tank, and the boosting pump are sequentially connected by a gas-liquid pipeline, and a safety valve is arranged between the pressure regulating valve and the gas storage tank.

[0024] Further, the boosting pump is connected to a nitrogen cylinder through a gas-liquid pipeline, which is used to provide a gas source for the system, transfer pressure, and regulate pressure.

[0025] Further, the microfluidic chip is a square chip with a size of 40*40 mm, and the center hole distance is 32 mm ± 0.5 mm.

[0026] The technical effects and advantages of the present invention:

[0027] (1) The micro-model chip fabricated by the glass wet etching-thermal compression bonding micro-model manufacturing technology of the present invention is transparent and visible, insensitive to organic solutions, and can conveniently capture and observe relevant information.

[0028] (2) The micro-model chip system of the present invention can manufacture a pore network system composed of pores with a size of 5 microns, and truly simulate the underground pore network or porous media system, and can realize the displacement simulation of water and oil close to the real formation environment of low-permeability reservoirs (100 nanometers - 10 microns).

[0029] (3) The temperature tolerance range of the experimental system of the present invention can reach 150 °C (temperature control accuracy ± 0.5 °C); the experimental pressure (injection pressure, confining pressure, backpressure) can reach 32 Mpa (pressure accuracy 0.1% F.S.), and can physically simulate the fluid phase change in micro-nano porous media under high temperature and high pressure conditions of low-permeability reservoirs (> 15 MPa, > 80 °C).

[0030] (4) Through this system, three different imbibition processes of reverse, spontaneous, and forced can be carried out to simulate different water flooding operation conditions in the oil production process, so as to realize the optimization of the imbibition process.

[0031] (5) The microscopic visualization system and method for simulating microfluidic displacement in low-permeability reservoirs of the present invention are simple to operate, facilitating the conduct of basic research on the imbibition physical laws of low-permeability reservoir rocks, and having important scientific significance for enhancing oil recovery in low-permeability oilfields.

[0032] Other features and advantages of the present invention will be described in the following specification, and will, in part, be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and attained by the structure pointed out in the specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 It is a structural diagram of a microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs of the present invention;

[0035] Figure 2 It is a schematic diagram of a microfluidic chip of the present invention;

[0036] Figure 3 For the present invention Figure 2 A partial enlarged view of the microfluidic chip in the present invention;

[0037] Figure 4 It is a brightness map of the displacement result of the microfluidic chip of the present invention;

[0038] In the reference numerals of the drawings, 1 is a control console; 11 is a computer; 2 is a microscopic visualization high-temperature and high-pressure autoclave; 21 is a visible chamber; 22 is an confining pressure pump; 23 is a back pressure valve; 24 is a buffer; 25 is a back pressure pump; 3 is a gas-liquid pressurization system; 31 is a piston container; 32 is an ISCO pump; 33 is a pressure regulating valve; 34 is a safety valve; 35 is a gas storage tank; 36 is a booster pump; 4 is a microfluidic chip. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0040] To address the deficiencies of the prior art, the present invention discloses a microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs. Figure 1 The following is a structural diagram of a microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs according to the present invention, as Figure 1 shown. The system includes: a control console 1, a microscopic visualization high-temperature and high-pressure autoclave 2, a gas-liquid pressurization system 3, and a microfluidic chip 4. Among them,

[0041] the control console 1 is electrically connected to the confining pressure pump 22 and the back pressure pump 25 of the microscopic visualization high-temperature and high-pressure autoclave 2 through electric wires;

[0042] the control console 1 is electrically connected to the ISCO pump 32 and the booster pump 36 of the gas-liquid pressurization system 3 through electric wires;

[0043] the microscopic visualization high-temperature and high-pressure autoclave 2 is connected to the gas-liquid pressurization system 3 through a gas-liquid pipeline;

[0044] the microfluidic chip 4 can be directly placed in the visual chamber 21 of the microscopic visualization high-temperature and high-pressure autoclave 2.

[0045] Further, the control console 1 includes: a computer 11.

[0046] Further, the microscopic visualization high-temperature and high-pressure autoclave 2 includes: a visual chamber 21, a confining pressure pump 22, a back pressure valve 23, a buffer 24, and a back pressure pump 25. Among them, the visual chamber 21 is connected to the confining pressure pump 22 through a gas-liquid pipeline; the confining pressure pump 22 and the back pressure pump 25 are electrically connected to the computer 11 through electric wires; the visual chamber 21 is connected to the back pressure pump 25 through a gas-liquid pipeline, and a back pressure valve 23 and a buffer 24 are sequentially arranged between the visual chamber 21 and the back pressure pump 25.

[0047] Further, a plurality of conventional valves are provided in the microscopic visualization high-temperature and high-pressure autoclave 2 for connecting or disconnecting pipelines.

[0048] Further, the gas-liquid pressurization system 3 includes: a plurality of piston containers 31, an ISCO pump 32, a pressure regulating valve 33, a safety valve 34, a gas storage tank 35, and a booster pump 36. Among them, the ISCO pump 32 and the booster pump 36 are electrically connected to the computer 11 through electric wires; the ISCO pump 32 is connected to the piston container 31 through a gas-liquid pipeline, and the piston container 31 is connected to the visual chamber 21 through a gas-liquid pipeline; the pressure regulating valve 33, the gas storage tank 35, and the booster pump 36 are sequentially connected through a gas-liquid pipeline, and a safety valve 34 is arranged between the pressure regulating valve 33 and the gas storage tank 35; the booster pump 36 is connected to a nitrogen cylinder through a gas-liquid pipeline. The pressure regulating valve 33 is used to adjust the pressure and flow rate of the medium; the safety valve 34 is used to discharge the excess medium when the medium pressure exceeds the specified value to ensure the safety of the pipeline system and equipment.

[0049] Furthermore, a plurality of conventional valves are provided in the gas-liquid boosting system 3 for connecting or disconnecting pipelines.

[0050] It should be noted that in the gas-liquid boosting system 3, the number of piston containers 31 and ISCO pumps 32 can be increased or decreased according to experimental conditions, but the number of piston containers 31 is at least ≥ 3.

[0051] Furthermore, the system can place the microfluidic chip 4 into the microscopic visualization high-temperature and high-pressure autoclave 2 to physically simulate the fluid phase change in the micro-nano porous medium under high-temperature and high-pressure conditions. The experimental temperature range can reach 150 °C (temperature control accuracy ±0.5 °C); the experimental pressure (injection pressure, confining pressure, back pressure) can reach 32 Mpa (pressure accuracy 0.1% F.S.); the microfluidic chip 4 that can be placed is a square chip with a size of 40 * 40 mm, and the center hole distance is 32 mm ±0.5 mm; the confining pressure and back pressure can automatically track the injection pressure for upward and downward adjustment.

[0052] Furthermore, Figure 2 is a schematic diagram of the microfluidic chip of the present invention; Figure 3 For the present invention Figure 2 The partial enlarged view of the microfluidic chip in Figure 2-3 As shown, the microfluidic chip 4 is obtained by washing a 4-inch round thick glass substrate with acetone and clean water, spin-coating positive photoresist onto the glass substrate; placing the previously designed and printed pore structure template on the photoresist for UV exposure, and washing away the unexposed part with a developer after exposure; placing the substrate in an electron beam deposition device for coating with a thin protective metal; cleaning the remaining photoresist, and performing wet etching with a hydrofluoric acid buffer solution; removing the metal protective layer after etching; finally, covering the glass substrate with another 4-inch glass wafer of the same size, and putting it into a hot press bonding machine for hot press bonding at high temperature to seal the channels for fluid flow inside. Its characteristics are fully transparent, high-pressure resistant, with a pore scale in the micron level, and having stable physical and chemical properties such as being insensitive to organic solutions and not deforming.

[0053] The present invention also discloses a displacement method for a microscopic visualization system for simulating microfluidic displacement. This method is implemented in a microscopic visualization system for simulating microfluidic displacement as described above, and includes the following steps:

[0054] First, according to the observation needs, a fluorescent dye can be added to the oil phase to facilitate differentiation under a microscope. Before the experiment, the basic physical parameters of the selected liquid are measured first, and then the fabricated microfluidic chip 4 is placed on the microscope stage and fixed in a highly transparent and flat quartz glass dish for the experiment.

[0055] After saturating with oil, the aqueous phase is slowly injected into a glass dish until the entire microfluidic chip 4 is just submerged, and imbibition displacement is carried out, and the video recording is started to record the experimental process. Specifically, the computer 11 in the console 1 is used to control the gas-liquid pressurization system 3 (where the piston container 31 is used to store liquids such as oil and water), and the liquid is pushed into the microfluidic chip 4 in the microscopic visualization high-temperature and high-pressure autoclave 2, and then the displacement experiment is carried out.

[0056] During the imbibition process, through a fluorescence microscope, rapid identification and statistics can be carried out through a computer software program, and it is easy to capture the occurrence forms of each oil droplet and water and infer their thermodynamic properties.

[0057] Embodiment:

[0058] The present invention will be further described below in conjunction with the embodiments and the drawings.

[0059] The Changqing low-permeability reservoir has small pore scales (100 nm - 15 μm), high formation temperature and pressure (>12 MPa, >70 °C), and it is difficult to produce the crude oil in the reservoir matrix, resulting in low oil recovery. As an important oil production mechanism in the development of low-permeability reservoirs, imbibition can improve the production degree of the crude oil in the reservoir matrix. The microfluidic displacement microscopic visualization simulation is carried out by using the device of the present invention to study the optimal water flooding conditions, including the following steps:

[0060] (1) First, use AutoCAD software to design the pore structure. The depth of the porous medium is 5 μm, and the pore throats are 8 - 20 μm (different sizes of pore throats can be obtained by redesigning the arrangement of particles). When designing, the right porous medium is completely open and connected to the atmosphere as the inlet for reverse imbibition, and the fluid is injected from the injection port at the left end.

[0061] (2) Place the designed and printed pore structure template on the photoresist for UV exposure. After exposure, wash away the unexposed part with a developer, and carry out wet etching with a hydrofluoric acid buffer solution; after etching, clean and remove the metal protective layer; finally, cover another 4-inch glass wafer of the same size above the glass base and put it into a thermal compression bonding machine for thermal compression bonding at high temperature.

[0062] (3) Use tetradecane as the oil phase, and add a fluorescent dye (nile red) to the oil phase as needed for easy distinction under the microscope.

[0063] (4) Place the fabricated microfluidic chip 4 on the microscope stage and fix it in a highly transparent and flat quartz glass dish, and then put it into the high-temperature and high-pressure autoclave 2 for experiments. After saturating with oil, slowly inject the aqueous phase into the glass dish until the entire model is just submerged, and carry out spontaneous and forced imbibition experiments, and start recording the experimental process by turning on the video recording.

[0064] (5) During the experiment, a 1X lens was used to observe the global imbibition of the model, and 4X-10X lenses were used to observe the local imbibition details. During the imbibition process, through a fluorescence microscope and a computer software program, rapid identification and statistics can be carried out, and the occurrence forms (volume, topological structure, surface area, free interface curvature, pore occupancy number, etc.) of each oil droplet and water can be easily captured, and their thermodynamic properties (capillary pressure Pc, total surface energy F) can be deduced.

[0065] (6) Select some iconic experimental processes, and select key time points during the imbibition process for analysis of the brightness map (the bright color is the oil phase and the dark color is the water phase) to examine the fluid displacement conditions during different imbibition processes. Figure 4 The brightness map of the displacement result of the microfluidic chip of the present invention is as Figure 4 shown. It can be seen that the preferential outflow paths of oil and water during the imbibition process. In the preferential path of oil, the continuous oil phase occupies most of the pores, and the continuous water phase occupies most of the throats. The displacement volume can be calculated by the area method.

[0066] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs, characterized in that, The system includes: a console (1), a micro-visualization high-temperature and high-pressure autoclave (2), a gas-liquid pressurization system (3), and a microfluidic chip (4); wherein, The console (1) is connected to the micro-visualization high-temperature and high-pressure autoclave (2) through an electric wire; The console (1) is connected to the gas-liquid pressurization system (3) through an electric wire; The micro-visualization high-temperature and high-pressure autoclave (2) is connected to the gas-liquid pressurization system (3) through a gas-liquid pipeline; The microfluidic chip (4) can be directly placed inside the micro-visualization high-temperature and high-pressure autoclave (2).

2. A microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs according to claim 1, characterized in that The console (1) includes a computer (11); the computer (11) is used to control the gas-liquid pressurization system (3), and push the liquid into the microfluidic chip (4) in the micro-visualization high-temperature and high-pressure autoclave (2), and then conduct a displacement experiment.

3. A microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs according to claim 1 or 2, characterized in that, The micro-visualization high-temperature and high-pressure autoclave (2) includes: a visual chamber (21), a confining pressure pump (22), a back pressure valve (23), a buffer (24), and a back pressure pump (25); wherein, The visual chamber (21) is connected to the confining pressure pump (22) through a gas-liquid pipeline; The confining pressure pump (22) and the back pressure pump (25) are connected to the computer (11) through an electric wire; The visual chamber (21) is connected to the back pressure pump (25) through a gas-liquid pipeline, and a back pressure valve (23) and a buffer (24) are sequentially arranged between the visual chamber (21) and the back pressure pump (25).

4. A microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs according to claim 2, characterized in that The gas-liquid pressurization system (3) includes: a piston container (31), an ISCO pump (32), a pressure regulating valve (33), a safety valve (34), a gas storage tank (35), and a booster pump (36); wherein, The ISCO pump (32) and the booster pump (36) are connected to the computer (11) through an electric wire; The ISCO pump (32) is connected to the piston container (31) through a gas-liquid pipeline, and the piston container (31) is connected to the visual chamber (21) through a gas-liquid pipeline; The pressure regulating valve (33), the gas storage tank (35), and the booster pump (36) are sequentially connected through a gas-liquid pipeline, and a safety valve (34) is arranged between the pressure regulating valve (33) and the gas storage tank (35).

5. A microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs according to claim 4, characterized in that The booster pump (36) is connected to a nitrogen cylinder through a gas-liquid pipeline, and is used to provide a gas source for the system, transfer pressure, and regulate pressure.

6. A microscopic visualization system for simulating microfluidic displacement in low-permeability reservoirs according to claim 1, characterized in that, The microfluidic chip (4) is a square chip with a size of 40*40 mm, and the center hole distance is 32 mm ± 0.5 mm.

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