Overpressure backflow simulation device and simulation method thereof

Abstract

The overpressure backflow simulation device comprises a pressure and liquid supply mechanism, a backflow migration mechanism and an acquisition monitoring mechanism, the pressure and liquid supply mechanism comprises a lifting platform, a water storage container and an oil storage container, the water storage container is arranged on the lifting platform, the lower end of a breather pipe is inserted into the top of the water storage container, and the lower end of the breather pipe is arranged on the oil storage container. The first U-shaped pipe connects the water storage container with the oil storage container, and the oil storage container is connected with a hydrocarbon source rock stratum of the backward flow migration model through a horizontal pipe extending from the lower end of the second U-shaped pipe; the backward flowing and transporting subsystem comprises a water tank and a backward flowing and transporting model, the water tank is provided with a pair of transparent tank walls, the backward flowing and transporting model is immersed in a water body of the water tank, and a horizontal pipe of a second U-shaped pipe is horizontally inserted into a hydrocarbon source rock stratum; the back-filling migration model adopts a sandwich structure, and a hydrocarbon source rock layer, a reservoir and an interlayer are enclosed in the middle by a mudstone closed area. According to the method, the overpressure coefficient is consistent with the stratum, and the influence of the overpressure degree on backward flow migration, filling and reservoir forming can be visually analyzed.

Description

Technical field:

[0001] The present invention relates to the technical field of deep oil and gas exploration, in particular to an overpressure backflow simulation device and a simulation method thereof. Background technology:

[0002] Deep oil and gas exploration is generally underdeveloped and represents a key area of ​​current and future exploration. In a source-reservoir configuration characterized by upper generation and lower storage, downward oil and gas migration is a key factor in the enrichment and accumulation of deep oil and gas. Compared to shallow and medium-layer oil and gas, the dynamic mechanisms and patterns of deep oil and gas migration and accumulation have significantly changed. Physical simulation is a key tool for understanding the characteristics and patterns of backward migration. The article "Physical Simulation Experiments of Deep Oil and Gas Backflow" used an integrated tectonic migration simulation device to study the backward migration of oil along faults. However, overpressure is the driving force behind backward migration, and the experimental device described in the article cannot simulate overpressure environments. Summary of the invention:

[0003] One object of the present invention is to provide an overpressure backflow simulation device, which is used to solve the problem that deep oil and gas backflow simulation in the prior art cannot simulate overpressure environment; another object of the present invention is to provide a simulation method for this overpressure backflow simulation device.

[0004] The technical solution adopted by the present invention to solve its technical problems is as follows: the overpressure backflow simulation device includes a pressure and liquid supply mechanism, a backflow migration mechanism and a collection and monitoring mechanism. The pressure and liquid supply mechanism includes a lifting platform, a water storage container and an oil storage container. The water storage container is arranged on the lifting platform, the lower end of the ventilation pipe is inserted into the top of the water storage container, the first U-shaped tube connects the water storage container and the oil storage container, and the oil storage container is connected to the hydrocarbon source rock layer of the backflow migration model through a horizontal tube extending from the lower end of the second U-shaped tube; the backflow migration subsystem includes a water trough and a backflow migration model, the water trough has a pair of transparent trough walls, and the backflow migration model The U-shaped tube is immersed in the water in the tank, and the horizontal tube of the second U-shaped tube is horizontally inserted into the source rock layer; the backflow migration model adopts a sandwich structure, with the mudstone sealing area surrounding the source rock layer, reservoir layer and interlayer in the middle, the source rock layer is located on the reservoir layer and interlayer, and the reservoir layer and interlayer are set at intervals. Two glass plates sandwich the mudstone sealing area, source rock layer, reservoir layer and interlayer in the middle, and the two glass plates are sealed by a rubber strip. Particles are evenly distributed between the rubber strip and the two glass plates, so that the interior of the model is connected to the surrounding water body; the data collection and monitoring mechanism includes a digital camera and a control computer, and the digital camera is set on the transparent tank wall.

[0005] The method for making the backflow migration model in the above scheme is as follows: first, a rubber strip is laid around the first glass plate, and the horizontal tube of the second U-shaped tube is inserted through the rubber strip and fixed in the source rock layer. Then, a metal partition is used to divide the area surrounded by the rubber strip into a mudstone closed area, an interlayer, a reservoir and a source rock layer, wherein the mudstone closed area is filled with the finest particles, and the interlayer is filled with finer particles. The particle size of the interlayer is smaller than that of all reservoirs. In order to simulate the uniform hydrocarbon expulsion of the source rock, the coarsest particles are filled in the source rock layer; the second glass plate is used to align and cover the first glass plate, knock and vibrate to make the surface of the accumulated particles flat, and the corresponding particles are added to the area where the particles are missing, and the second glass plate is used to cover and knock and vibrate again until all areas are flat, then the metal partition is removed, and particles are evenly sprinkled on the rubber strip, covered with the second glass plate, and the first and second glass plates are fixed with C-shaped clamps on all sides.

[0006] In the above scheme, the lower end of the vent tube is inserted into the top of the water storage container, and the upper end is connected to the atmosphere to ensure that the water surface pressure in the water storage container is atmospheric pressure; one end of the first U-shaped tube is inserted into the bottom of the water storage container, and the other end is inserted into the bottom of the oil storage bottle. A valve is provided on the first U-shaped tube; the oil storage container is filled with both water and oil. One end of the second U-shaped tube is inserted into the top of the oil storage container, and the horizontal tube with the other end is inserted into the hydrocarbon source rock layer.

[0007] In the above scheme, the two glass plates of the backflow migration model are placed corresponding to the transparent tank wall of the water tank.

[0008] In the above scheme, the particles are glass beads.

[0009] In the above solution, the first glass plate and the second glass plate are both made of 5 mm thick tempered glass, the tempered glass is 500 mm long and 500 mm wide; the thickness of the adhesive strip is 2 mm and the width is 10 cm.

[0010] In the above scheme, the metal partition is a 2mm thick copper plate, cut into 2mm wide strips; the inner diameter of the water storage container and the oil storage container is 300mm.

[0011] When the overpressure backflow simulation device in the above scheme is working, the immersion depth of the backflow migration model is adjusted to adjust the pressure P of the saturated water in the backflow migration model. w =ρ w gH1; The source rock layer is filled with oil at a constant pressure through the liquid supply and pressure supply mechanism to simulate the hydrocarbon generation and pressurization of the source rock; the oil-water interface in the oil storage container is on the same horizontal plane as the source rock filling point in the model. According to the principle of the communicating vessel, P o =ρ w The values ​​of gH2 and H2 are continuously adjusted by the lifting platform and the liquid level in the water storage container. The corresponding overpressure coefficient is:

[0012] α=H2 / H1 (Formula 1)

[0013] By increasing the diameters of the water and oil storage containers, the experimental error ΔH2 / H2 is controlled within 1%. When determining the immersion depth of the backflow migration model, the hydrostatic pressure P closest to the reservoir in the backflow migration model must be ensured. w =ρ w gh and reservoir critical displacement pressure P c The ratio is the same as that of the stratum;

[0014] Residual pressure P generated by overpressure e =ρ w g(H2-H1) and reservoir critical displacement pressure P c The ratio is the same, that is:

[0015]

[0016] The uppermost reservoir in the backflow migration is the first to be filled. When calculating the critical displacement pressure of the reservoir, the uppermost reservoir is used as the reference object.

[0017] The simulation method of the above-mentioned overpressure backflow simulation device is as follows:

[0018] Step 1: Use filling experiments to determine the critical displacement pressure P of the reservoir c ;

[0019] Step 2: Determine the overpressure coefficient α of the source rock layer based on the well logging data, and determine the residual pressure P of the source rock by combining the top reservoir depth h1 and the overpressure coefficient. e =ρ w gh1α-1), and calculate the ratio of power to resistance under formation conditions:

[0020] Step 3: Select the particle size of the top reservoir filling particles in the backflow migration model and calculate or measure the corresponding reservoir critical displacement pressure P c When selecting the particle size of other reservoirs, ensure that the ratio of the permeability of each reservoir corresponds to the formation; determine the particle materials and corresponding particle sizes used in each source rock layer and mudstone sealing area, so that the particle size of the source rock layer is larger than that of all reservoir layers, the particle size of the interlayer is smaller than that of all reservoir layers, and the particle size of the mudstone sealing area is smaller than that of the interlayer;

[0021] Step 4: Assemble the backflow migration model;

[0022] Step 5: Combine the formula α=H2H1 and Calculate H1 and H2;

[0023] Step 6: Place the backflow migration model in a water tank, assemble an overpressure backflow simulation device, determine the immersion depth of the backflow migration model in the water tank according to Formula 1, and slowly inject water into the water tank. As the water level rises, the model is evenly saturated by water under the influence of the critical displacement pressure and gravity. Water is injected until the reservoir immersion depth h required for calculation is reached.

[0024] Step 7: Adjust the lifting platform so that H2 reaches the predetermined value;

[0025] Step 8. Turn on the camera, adjust the focus, set the shooting frequency and total number of photos by controlling the computer, and start the timed interval selfie;

[0026] Step 9: Open the valve. Under the action of the water head pressure, the oil enters the source rock layer of the backflow migration model and provides it with a constant pressure to simulate the hydrocarbon generation pressurization and promote the backflow of the oil phase.

[0027] Beneficial effects:

[0028] 1. The present invention provides an overpressure backflow simulation device for simulating the backflow migration and accumulation process of deep oil and gas. Since the backflow migration model is made of transparent glass, the migration and accumulation process can be intuitively displayed and dynamically observed in real time.

[0029] 2. The present invention provides an overpressure backflow simulation method for simulating the migration and accumulation of deep oil and gas. Since the design of the backflow migration model fully takes dynamic similarity into consideration, the ratio of migration motive force and resistance under experimental conditions is the same as the ratio of migration motive force and resistance under formation conditions. The test results can better reflect the backflow migration process in the formation.

[0030] 3. The present invention provides an overpressure backflow simulation method. Under the condition of ensuring dynamic similarity, the overpressure coefficient and the formation remain consistent, so the impact of the overpressure degree on backflow migration and filling can be intuitively analyzed. Description of the drawings:

[0031] Figure 1 Schematic diagram of the overpressure backflow simulation device of the present invention;

[0032] Figure 2 This is the AB section view of the backflow migration model in the figure.

[0033] Figure 3 Schematic diagram of the backflow migration model in the embodiment.

[0034] Figure 4 This is a diagram showing the effect of backflow migration in the embodiment.

[0035] In the figure: 1-lifting platform, 2-water storage container, 21-water, 31-ventilation pipe, 32-first U-shaped tube, 33-second U-shaped tube, 34-valve, 4-oil storage container, 41-oil, 5-water tank, 6-backflow migration model, 61-source rock layer, 62-interlayer, 63-reservoir layer, 64-mudstone sealing area, 65-first glass plate, 66-second glass plate, 67-rubber strip, 7-digital camera, 8-data cable, 9-control computer. Specific implementation method:

[0036] The present invention will be further described below in conjunction with the appended drawings:

[0037] Combine Figures 1-4 As shown, this overpressure backflow simulation device includes a pressure and liquid supply mechanism, a backflow migration mechanism and a collection and monitoring mechanism. The pressure and liquid supply mechanism includes a lifting platform 1, a water storage container 2 and an oil storage container. The water storage container 2 is set on the lifting platform 1. The lower end of the ventilation pipe 31 is inserted into the top of the water storage container 2. The first U-shaped tube 32 connects the water storage container and the oil storage container. The oil storage container is connected to the hydrocarbon source rock layer 61 of the backflow migration model 6 through a horizontal tube extending from the lower end of the second U-shaped tube 33; the backflow migration subsystem includes a water tank 5 and a backflow migration model 6. The water tank 5 has a pair of transparent tank walls. The backflow migration model 6 is immersed in the water body of the water tank. The horizontal tube of the type pipe 33 is horizontally inserted into the hydrocarbon source rock layer 61; the backflow migration model 6 adopts a sandwich structure, with the mudstone sealing area 64 surrounding the hydrocarbon source rock layer 61, the reservoir layer 63 and the interlayer 62 in the middle, the hydrocarbon source layer is located above the reservoir layer and the interlayer, and the reservoir layer 63 and the interlayer 62 are spaced apart. Two glass plates sandwich the mudstone sealing area 64, the hydrocarbon source rock layer 61, the reservoir layer 63 and the interlayer 62 in the middle, and the two glass plates are sealed by a rubber strip 67. Particles are evenly distributed between the rubber strip 67 and the two glass plates, so that the interior of the model is connected to the surrounding water body; the data collection and monitoring mechanism includes a digital camera 7 and a control computer 9, and the digital camera is set on the transparent tank wall.

[0038] The water storage container contains water 21. A vent tube 31 has one end inserted into the top of the container and the other end connected to the atmosphere, ensuring the water surface pressure in the container remains at atmospheric pressure. A first U-shaped tube 32 has one end inserted into the bottom of the water storage container and the other end inserted into the bottom of the oil storage bottle. A valve 34 is provided on the first U-shaped tube. The oil storage container 4 contains both water and oil 41. Because oil has a lower density than water, the oil 41 is above the water. A second U-shaped tube 33 connects the oil storage container to the migration model. One end of the second U-shaped tube is inserted into the top of the oil storage container and the other end is inserted into the source rock layer 61 in the backflow migration model 6.

[0039] The backflow migration mechanism includes a water trough 5 and a backflow migration model 6. The water trough 5 has a pair of transparent sides, allowing clear observation of the backflow migration model 6 within the internal water body. The backflow migration model 6 adopts a sandwich structure, with a planar structure divided into a mudstone sealing area 64, a reservoir 63, an interlayer 62, and a source rock layer 61. The mudstone sealing area surrounds the source rock layer, interlayer, and reservoir layer, and the source rock layer is located above the reservoir and interlayer. When making the model, a rubber strip 67 is first placed around the first glass plate 65. First, one end of the second U-shaped tube 33 is passed through the rubber strip 67 and fixed in the middle of the source rock layer. Then, a metal spacer divides the area surrounded by the rubber strip into a mudstone sealing area, an interlayer area, a reservoir area, and a source rock area. The mudstone sealing area is filled with the finest particles, and the interlayer area is filled with finer particles. To simulate the uniform expulsion of hydrocarbons from the source rock, the source rock area is filled with the coarsest particles, and the granular material is glass microspheres. Align and cover with a second glass plate 66, tap and oscillate to make the surface of the accumulated particles flat, add the corresponding particles in the missing areas, cover again, tap and oscillate to add, until all areas are flat, then remove the metal partition, sprinkle particles evenly on the rubber strip 67, ensure that the interior and surrounding spaces of the model are connected, cover with the second glass plate 66, and fix the first glass plate 65 and the second glass plate 66 with C-clamps on all sides.

[0040] The first glass plate 65 and the second glass plate 66 are 5 mm thick tempered glass with a length × width of 500 mm × 500 mm; the rubber strip is 2 mm thick and 10 cm wide; the metal frame is a 2 mm thick copper plate cut into long strips with a width of 2 mm; the inner diameter of the water storage container 2 and the oil storage container 4 is 300 mm.

[0041] The data acquisition and monitoring mechanism includes a digital camera 7 and a control computer 9, which are connected via a data line 8. The control computer 9 can control the frequency of taking photos and the total number of photos.

[0042] The measurement principle of the present invention is as follows: the backflow migration model 6 is immersed in the water body in the water tank 5. Since the internal space of the backflow migration model 6 is connected to the surrounding water body, the pressure P of the saturated water in the model can be adjusted by adjusting the immersion depth. w =ρ w gH1; In the experimental device, the source rock layer is filled with oil at a constant pressure through the liquid supply and pressure supply mechanism to simulate the hydrocarbon generation and pressurization of the source rock; wherein the oil-water interface in the oil storage container 4 is on the same horizontal plane as the source rock filling point in the model, according to the principle of the communicating vessel, at this time P o =ρ w The values ​​of gH2 and H2 can be continuously adjusted by the height of the liquid level in the lifting platform 1 and the water storage container 2. The corresponding overpressure coefficient is:

[0043] α=H2 / H1 (Formula 1)

[0044] By increasing the diameters of the water storage container 2 and the oil storage container 4, the experimental error ΔH2 / H2 can be controlled within 1%. When determining the immersion depth of the backflow migration model 6, it is necessary to ensure that the hydrostatic pressure P closest to the reservoir in the backflow migration model is w =ρ w gh and critical displacement pressure P c The ratio is the same as that of the formation, and h is the reservoir depth;

[0045] In order to make the simulation effect better reflect the formation conditions, the pressure head H2 should ensure that the ratio of power to resistance under the experimental conditions is consistent with the formation conditions. The residual pressure P generated by the overpressure in the experiment is e =ρ w g(H2-H1) and reservoir critical displacement pressure P c The ratio is the same, that is:

[0046]

[0047] In actual operation, there may be multiple reservoirs, but the uppermost reservoir in the backflow migration is the first to be filled. Therefore, when calculating the critical displacement pressure of the reservoir, the uppermost reservoir is used as the reference object.

[0048] The steps and methods for simulating backflow migration of the present invention include:

[0049] 1. Determine the critical displacement pressure P of the reservoir using filling experiments c ;

[0050] 2. Determine the overpressure coefficient α of the source rock layer based on the well logging data, and determine the residual pressure P of the source rock by combining the top reservoir depth h1 and the overpressure coefficient e =ρ w gh1(α-1), and calculate the ratio of power to resistance under formation conditions:

[0051] 3. Design the partitions of the backflow migration simulation model and make the metal grid;

[0052] 4. First, select the particle size of the topmost reservoir filling particles and calculate or measure its corresponding critical displacement pressure Pc. When selecting the particle size of other reservoirs, ensure that the ratio of the permeability of each reservoir corresponds to the formation;

[0053] 5. Determine the particle materials and corresponding particle sizes used in each source rock layer and mudstone sealing area so that the particle size of the source rock layer is larger than that of all reservoir layers, the particle size of the interlayer is smaller than that of all reservoir layers, and the particle size of the mudstone sealing area is smaller than that of the interlayer;

[0054] 6. Lay the first glass plate 65 flat, attach circular rubber strips around the top surface, and secure the metal spacer in the middle of the area enclosed by the rubber strips.

[0055] 7. Fix one end of the second U-shaped tube 33 in the middle of the designated source rock layer;

[0056] 8. Fill the source rock layer, reservoir layer, interlayer, and mudstone enclosed area separated by the metal grid with different particles, repeatedly flatten and replenish them, and finally evenly sprinkle the granular material on the rubber strip. Remove the metal grid, cover it with the second glass plate 66, and fix the first glass plate 65 and the second glass plate 66 together with C-shaped clamps on all sides;

[0057] 9. Combined formula α=H2H1 and H1 and H2 are calculated.

[0058] 10. Place the backflow migration model in a water tank. Determine the immersion depth of the backflow migration model in the water tank according to Formula 1. Slowly inject water into the water tank. As the water level rises, the model is evenly saturated by water due to the influence of critical displacement pressure and gravity. Inject water until the required source rock immersion depth H1 is reached.

[0059] 11. Adjust the lifting platform so that H2 reaches the predetermined value;

[0060] 12. Use pipelines to connect the backflow migration model, oil storage container and water storage container;

[0061] 13. Turn on the camera, adjust the focus, set the shooting frequency and total number of photos through the computer, and start the timed interval selfie;

[0062] 14. Open valve 34. Under the action of water head pressure, oil enters the source rock layer of the backflow migration model and provides it with a constant pressure, simulating hydrocarbon generation pressure increase and promoting oil phase backflow.

[0063] Example:

[0064] Well A, located in the central area of ​​Subsag A in the Weixinan Sag, was used as the simulation target. The source rock is the oil shale of the Liu 2 Member, with an average burial depth of 4,490 meters and a pressure coefficient of 1.9. The underlying Liu 3 Member serves as the reservoir and conducting layer. Based on physical properties, it is divided into two sub-members: the Upper Liu 3 Member and the Lower Liu 3 Member. The Upper Liu 3 Member features frequent interbedded sandstone and mudstone layers with significant lateral heterogeneity, while the Lower Liu 3 Member comprises a large set of sandstones with good overall connectivity. The Upper Liu 3 Member has a permeability of 0.05 mD and a porosity of 5%. These porosity and permeability parameters remain stable with depth. Thin section analysis reveals that microfractures are well-developed in the Upper Liu 3 Member, providing pathways for oil to flow back through the mudstone.

[0065] 1. Merge the upper reservoir of Liusan into three smaller layers: upper, middle and lower

[0066] 2. Determine the critical displacement pressure P of the uppermost reservoir using filling experiments c =3.24MPa;

[0067] 3. The overpressure coefficient of the source rock layer is α = 1.9. The residual pressure P of the source rock is determined by combining the burial depth of 4490m and the overpressure coefficient. e =39.6MPa, and the ratio of power to resistance under formation conditions is calculated as:

[0068]

[0069] 4. Design a zoning model for backflow migration simulation. The middle area, from top to bottom, consists of the source rock layer, the first sublayer of the upper stream 3, the second sublayer of the upper stream 3, the third sublayer of the upper stream 3, and the reservoir layer below the lower stream 3. The sublayers above the upper stream 3 are laterally blocked, while the lower stream 3 is generally connected. A metal grid is constructed based on the stratigraphic characteristics.

[0070] 5. The physical properties of each layer in the upper subsection of the third section decrease slightly with the increase of burial depth. The filling particle size of the first layer in the upper subsection of the third section is determined to be 30 mesh, and the corresponding critical displacement pressure P is c =725.2Pa; the second and third sublayers in the upper section of stream 3 are filled with 35-mesh and 40-mesh granular materials, respectively. The lower subsection of stream 3 is filled with 30-mesh granular materials, the interlayers and low-permeability barrier zones are filled with 80-mesh granular materials, the source rock layers are filled with 20-mesh granular materials, and the mudstone sealing zone is filled with 120-mesh granular materials.

[0071] 6. Lay the first glass plate 65 flat, attach circular rubber strips around the top surface, and secure the metal spacer in the middle of the area enclosed by the rubber strips.

[0072] 7. Fix one end of the second U-shaped pipe 33 of the pipeline in the middle of the designated source rock layer;

[0073] 8. Fill the source rock layer, the first sublayer above stream 3, the second sublayer above stream 3, the third sublayer above stream 3, the lower stream 3, the interlayer area, the low-permeability barrier zone, and the mudstone sealing area separated by the metal grid with glass beads of 20 mesh, 30 mesh, 35 mesh, 40 mesh, 30 mesh, 80 mesh, 80 mesh, and 120 mesh, respectively. Repeatedly flatten and replenish, remove the metal grid, and finally evenly sprinkle granular material on the rubber strip. Cover with a second glass plate 66, and secure the first and second glass plates 65 and 66 together with C-shaped clamps on all sides.

[0074] 9. Combined formula α=H2 / H1 and The calculated values ​​of H1 and H2 are 1.72m and 0.9m respectively.

[0075] 10. Place the backflow transport model in a water tank. Determine the immersion depth of the backflow transport model in the water tank according to Formula 1. Slowly add water to the water tank. As the water level rises, the model is evenly saturated by the critical displacement pressure and gravity. Add water until the required immersion depth of 0.9 is reached.

[0076] 11. Adjust the lifting platform so that H2 reaches 1.72m;

[0077] 12. Use pipelines to connect the backflow migration model, oil storage container and water storage container;

[0078] 13. Turn on the camera, adjust the focus, and control the computer to set the photo frequency to 1 minute per photo and the total number of photos to 1000, and start the timer interval Selfie;

[0079] 14. Open valve 34. Under the action of water head pressure, oil enters the source rock layer of the backflow migration model and provides it with a constant pressure, simulating hydrocarbon generation pressure increase to promote oil backflow.

[0080] The simulation experiment results show that under the action of overpressure, the oil generated by the oil shale at the bottom of the second member of the Liu family flows back into the lower submember of the third member through the upper submember of the third member of the Liu family. The low permeability zone of the upper submember of the third member of the Liu family provides a shield for oil enrichment and accumulation. After the oil enters the lower submember of the third member of the Liu family, due to the good lateral connectivity of this layer, the oil no longer continues to flow back, but instead mainly migrates laterally.

Claims

1. An overpressure backflow simulation device, characterized in that: The overpressure backflow simulation device includes a pressure and liquid supply mechanism, a backflow migration mechanism, and a collection and monitoring mechanism. The pressure and liquid supply mechanism includes a lifting platform, a water storage container, and an oil storage container. The water storage container is set on the lifting platform, and the lower end of the ventilation pipe is inserted into the top of the water storage container. The first U-shaped tube connects the water storage container and the oil storage container. The oil storage container is connected to the hydrocarbon source rock layer of the backflow migration model through a horizontal tube extending from the lower end of the second U-shaped tube. The backflow migration subsystem includes a water tank and a backflow migration model. The water tank has a pair of transparent tank walls, and the backflow migration model is immersed in the water of the water tank. The horizontal tube of the second U-shaped tube is horizontally inserted into the source rock layer; the backflow migration model adopts a sandwich structure, the mudstone sealing area surrounds the source rock layer, reservoir and interlayer in the middle, the source layer rock is located on the reservoir and interlayer, the reservoir and interlayer are set at intervals, and two glass plates sandwich the mudstone sealing area, source rock layer, reservoir and interlayer in the middle. The two glass plates are sealed by a rubber strip, and particles are evenly distributed between the rubber strip and the two glass plates, so that the interior of the model is connected to the surrounding water body; the data collection and monitoring mechanism includes a digital camera and a control computer, and the digital camera is set on the transparent tank wall.

2. The overpressure backflow simulation device according to claim 1, characterized in that: The method for making the backflow migration model comprises the following steps: first, placing adhesive strips around a first glass plate, inserting a horizontal tube of a second U-shaped tube through the adhesive strips and fixing it in the source rock layer; then, using a metal spacer, dividing the area surrounded by the adhesive strips into a mudstone closed area, an interlayer, a reservoir layer, and a source rock layer; wherein the mudstone closed area is filled with the finest particles, the interlayer is filled with relatively fine particles, and the particle size of the interlayer is smaller than that of all reservoir layers; and to simulate uniform hydrocarbon expulsion from the source rock, the source rock layer is filled with the coarsest particles; aligning and covering the first glass plate with a second glass plate, tapping and oscillating the first glass plate to make the surface of the accumulated particles flat; supplementing the areas where particles are missing with corresponding particles; covering the area with the second glass plate again, tapping and oscillating the area until all areas are flat; then, removing the metal spacer, evenly sprinkling particles on the adhesive strips, covering the area with the second glass plate, and fixing the first and second glass plates with C-shaped clamps on all sides.

3. The overpressure backflow simulation device according to claim 2, characterized in that: The lower end of the vent pipe is inserted into the top of the water storage container, and the upper end is connected to the atmosphere to ensure that the water surface pressure in the water storage container is atmospheric pressure; one end of the first U-shaped tube is inserted into the bottom of the water storage container, and the other end is inserted into the bottom of the oil storage bottle, and a valve is provided on the first U-shaped tube; the oil storage container is filled with water and oil at the same time, one end of the second U-shaped tube is inserted into the top of the oil storage container, and the horizontal tube with the other end is inserted into the hydrocarbon source rock layer.

4. The overpressure backflow simulation device according to claim 3, characterized in that: The two glass plates of the backflow migration model are placed corresponding to the transparent tank wall of the water tank.

5. The overpressure backflow simulation device according to claim 4, characterized in that: The particles are glass beads.

6. The overpressure backflow simulation device according to claim 5, characterized in that: The first glass plate and the second glass plate are both made of 5 mm thick tempered glass, the tempered glass is 500 mm long and 500 mm wide; the thickness of the adhesive strip is 2 mm and the width is 10 cm.

7. The overpressure backflow simulation device according to claim 6, characterized in that: The metal spacer is a 2mm thick copper plate cut into 2mm wide strips; the inner diameters of the water storage container and the oil storage container are both 300mm.

8. The overpressure backflow simulation device according to claim 7, characterized in that: When the overpressure backflow simulation device is working, the saturated water pressure P in the backflow migration model is adjusted by adjusting the immersion depth of the backflow migration model. w =ρ w gH1, H1 is the immersion depth; the source rock layer is filled with oil at a constant pressure through the liquid supply and pressure mechanism to simulate the hydrocarbon generation and pressurization of the source rock; the oil-water interface in the oil storage container is on the same horizontal plane as the source rock filling point in the model. According to the principle of the communicating vessel, P o =ρ w gH2, H2 is the supply pressure head. The value of H2 is continuously adjusted by the lifting platform and the liquid level in the water storage container. The corresponding overpressure coefficient is: α=H2 H1 (Formula 1) By increasing the diameters of the water and oil storage containers, the experimental error ΔH2 H2 is controlled within 1%. When determining the immersion depth of the backflow migration model, the hydrostatic pressure P closest to the reservoir in the backflow migration model must be ensured. w =ρ w gh and reservoir critical displacement pressure P c The ratio is the same as that of the stratum; Residual pressure P generated by overpressure e =ρ w g(H2-H1) and reservoir critical displacement pressure P c The ratio is the same, that is: Where h is the reservoir depth, r is the ratio of power to resistance; The uppermost reservoir in the backflow migration is the first to be filled. When calculating the critical displacement pressure of the reservoir, the uppermost reservoir is used as the reference object.

9. A simulation method for the overpressure backflow simulation device according to claim 8, characterized in that: Step 1: Use filling experiments to determine the critical displacement pressure P of the reservoir c ; Step 2: Determine the overpressure coefficient α of the source rock layer based on the well logging data, and determine the residual pressure P of the source rock by combining the top reservoir depth h1 and the overpressure coefficient. e =ρ w gh1(α-1), and calculate the ratio of power to resistance under formation conditions: Step 3: Select the particle size of the top reservoir filling particles in the backflow migration model and calculate or measure the corresponding reservoir critical displacement pressure P c When selecting the particle size of other reservoirs, ensure that the ratio of the permeability of each reservoir corresponds to the formation; determine the particle materials and corresponding particle sizes used in each source rock layer and mudstone sealing area, so that the particle size of the source rock layer is larger than that of all reservoir layers, the particle size of the interlayer is smaller than that of all reservoir layers, and the particle size of the mudstone sealing area is smaller than that of the interlayer; Step 4: Assemble the backflow migration model; Step 5: Combine the formula α=H2 H1 and Calculate H1 and H2; Step 6: Place the backflow migration model in a water tank, assemble an overpressure backflow simulation device, determine the immersion depth of the backflow migration model in the water tank according to Formula 1, and slowly add water to the water tank. As the water level rises, the model is evenly saturated with water due to capillary force and gravity. Add water until the immersion depth H1 required by the calculation is reached. Step 7: Adjust the lifting platform so that H2 reaches the predetermined value; Step 8. Turn on the camera, adjust the focus, set the shooting frequency and total number of photos by controlling the computer, and start the timed interval selfie; Step 9: Open the valve. Under the action of the water head pressure, the oil enters the source rock layer of the backflow migration model and provides it with a constant pressure to simulate the hydrocarbon generation pressurization and promote the backflow of the oil phase.

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