CO2 flooding and burying simulation device and method for multi-layer ultra-low permeability oil and gas reservoir containing dynamic cracks

Abstract

The invention discloses a CO2 flooding and burying simulation device and method for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic cracks, relates to the technical field of CCUS oil and gas field development, and solves the problem that related technologies of a three-dimensional physical simulation method do not consider the dynamic cracks. Compared with an existing CO2 displacement experiment, the CO2 displacement simulation device for the multi-layer ultra-low permeability oil and gas reservoir containing the dynamic fractures can achieve simulation research of the dynamic fractures, and control over the property, the number and the opening limit pressure of the dynamic fractures can be achieved; the simulation development of the three-dimensional multi-layer ultra-low permeability reservoir containing the dynamic fracture is realized; direct verification of dynamic crack parameters and production dynamic characteristics is realized; the method can support the research on the influence of the property, scale and state of the dynamic fracture on the oil displacement efficiency and the burying amount during multi-layer combined injection, and has the obvious advantages of visualization and verifiability in combination with a CT scanning method.

Description

Technical Field

[0001] The present invention relates to the field of CCUS oil and gas fields, and in particular to a CO2 flooding simulation device and method for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures. Background Art

[0002] Ultra-low permeability reservoirs have low permeability, strong heterogeneity, and relatively developed fractures, which are significantly different from other geological storage bodies in CCUS. They show different characteristics during the injection of carbon dioxide for burial. The study of dynamic fractures is an important topic for understanding the seepage law, distribution characteristics, and storage effect of carbon dioxide in the formation. These fractures are controlled by the current geostress field. With the increase of injection volume and the increase of bottom hole pressure, they continue to extend toward the production well until they are connected with the pressure fractures of the production well. These new and effective fractures are called dynamic fractures.

[0003] Dynamic fractures affect the design of the coordinated CO2 flooding scheme at the bottom surface: (1) There are almost no fractures in the early stage of gas injection, and fractures are difficult to identify and determine parameters, which affects the early well network deployment and the formulation of gas injection technology policies. (2) The dynamic changes of fractures cause the migration of the dominant flow layer segment, which enhances the heterogeneity of the oil layer. (3) The existence of dynamic fractures makes the oil layer production more complicated and reduces the degree of production. In short, CO2 has strong fluidity, and the existence of dynamic fractures will profoundly affect the flow law and distribution characteristics of injected CO2. Understanding and studying the influence of dynamic fractures is an important prerequisite for optimizing engineering parameters and enhancing the effect of CO2 flooding.

[0004] At present, the research on dynamic fractures mainly includes numerical simulation methods and physical methods. Numerical simulation methods can study the dynamic fracture problem of reservoirs on a three-dimensional scale by establishing a virtual model, such as a characterization method for dynamic fractures in low permeability reservoirs. Due to the invisibility of the reservoir, the prediction results of numerical simulation cannot be directly verified. Therefore, it is necessary to use experimental methods to conduct a verifiable direct study on the characteristics of dynamic fractures. Another example is a physical testing device for dynamic fractures in low permeability reservoirs, which realizes the study of the causes of dynamic fractures based on one-dimensional flow of cores. And a dynamic fracture determination method and device for a pore roar channel network model in displacement simulation can study the impact of dynamic fractures on development on a small-scale two-dimensional plane. However, these studies cannot directly study the impact of dynamic fractures on reservoir development on a three-dimensional scale. On the other hand, many technologies related to three-dimensional physical simulation methods do not consider the problem of dynamic fractures, such as a three-dimensional physical simulation experimental device and a method for simulating the development of tight oil reservoirs, and a three-dimensional physical simulation system for periodic injection and production of gas storage reservoirs. Summary of the invention

[0005] CCUS carbon dioxide geological storage is a long-term process. Dynamic fractures are an important factor that cannot be ignored in the process of gas injection and long-term storage. They have an important impact on the design of gas injection parameters and pressure control levels. However, there is currently a lack of methods to directly study and verify dynamic fractures on a three-dimensional reservoir scale. The present invention designs simulation components of dynamic fractures, designs the distribution direction, distribution quantity and starting pressure of dynamic fracture simulation components according to the fracture description parameters of oil and gas reservoir engineering, and combines the production and experimental methods of indoor ultra-low permeability three-dimensional physical model devices to achieve a directly verifiable study of the influence of dynamic fractures.

[0006] A CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures, the device comprises two cap layers, n reservoir layers, n-1 interlayers, m dynamic fracture simulation devices, n flow control devices and n metering devices, and a flow injection pipeline; the reservoir layer is a physical model containing a dynamic fracture device or not containing a dynamic fracture device, and the interlayer is a physical model without dynamic fractures; an interlayer and a reservoir layer are a group of rectangular parallelepiped physical models of the same shape, the reservoir layer and the interlayer are placed alternately up and down, the reservoir layer of each group of dynamic fracture physical models comprises at least one dynamic fracture simulation component to form a dynamic fracture simulation device, and the left and right ends of the reservoir of each group of dynamic fracture simulation devices are respectively The same number of cylindrical holes as the number of dynamic fracture simulation components is drilled, the left end of the reservoir of each group of dynamic fracture simulation devices is connected to the control valve of the corresponding flow control device, and the right end of the reservoir of each group of dynamic fracture simulation devices is connected to the flow metering device; wherein, the dynamic fracture simulation components are pre-buried in a cylindrical groove reserved in the reservoir of each dynamic fracture simulation device, and after pre-buried, the dynamic fracture simulation device is cast and fixed with the proportioned reservoir cement, and the interlayer and the reservoir of the dynamic fracture simulation device are alternately placed to form a physical model group, and the cap layer is used to form n layers of CO2 flooding buried simulation devices with n reservoirs and n-1 interlayers to seal the bottom and the top respectively; wherein, n≥2, m≥1;

[0007] When the control valve of the flow control device at the left end of the reservoir I of the first group of physical models is opened and the bottom control valve is closed, the fluid injection pipeline is injected with the displacement medium CO2 gas at a constant temperature of 20℃~100℃ and a displacement pressure of 2.5MPa~30MPa, and oil displacement is carried out, and the first metering device is opened to measure the amount of oil displaced, the outlet pressure and the amount of CO2 discharged, and the time and related data are recorded;

[0008] When the control valve of the flow control device at the left end of the reservoir II of the second group of physical models is opened and the bottom control valve is closed, the left end control valve of the first group of physical models is closed and the bottom control valve is opened, the fluid injection pipeline is injected with the displacement medium CO2 gas at a constant temperature of 20℃~100℃ and a displacement pressure of 2.5MPa~30MPa, and oil displacement is carried out, the second metering device is opened, and the amount of oil displaced, the outlet pressure and the amount of CO2 discharged are measured, and the time and related data are recorded;

[0009] By analogy, when the nth flow control device is connected to the nth reservoir of the nth group of physical models, the nth meter records the data of the nth group of physical models; when the control pressure of each group of physical models is consistent, the recorded data are the experimental data of the same pressure driving burial of n reservoirs; when the control pressure of each group of physical models is inconsistent, the experimental data of different pressure driving burial of the first, second, ..., n reservoirs are recorded in sequence.

[0010] Preferably, the cover layer is used for packaging the bottom and top of the physical simulation model, and the cover layer is made of acrylic board; after the finished cover layer is alternately placed with the reservoir layer and the interlayer, polyvinyl alcohol PVA adhesive is used on the outside for gluing and sealing; the reservoir layer is made of cement, gypsum, and quartz sand of 40-80 mesh, which are bonded according to a certain mass ratio, wherein the mass ratio of reservoir I is 1:1:2, the mass ratio of reservoir II is 1:1:3, and the mass ratio of reservoir III is 1:1:4;

[0011] The interlayer is made of cement and gypsum in a bonding mass ratio of 1:1;

[0012] The dynamic fracture simulation device manufactures an artificial high-permeability core column according to the required specifications. The size of the artificial high-permeability core column ranges from φ2.5cm to 10cm. The length of the artificial high-permeability core column is 8cm to 50cm. Quartz sand 1mm to 2mm is used. The cement, gypsum, and quartz sand bonding mass ratio is 1:1:3. The artificial high-permeability core column 4 after solidification and cutting is used to manufacture a dynamic fracture simulation component and is loaded into the dynamic fracture simulation component groove reserved in the reservoir. Then, the mixture of cement and gypsum is poured and fixed; wherein, the cement and gypsum mass ratio is 1:1;

[0013] The flow control device is used to control the pressure of n reservoirs, and the pressure adjustment range is 2.5MPa to 30MPa.

[0014] Preferably, each group of physical models injects CO2 into the control valve of the flow control device, and the control valve is provided at the bottom and right side of the flow control device, and is opened in one direction alone when in use;

[0015] The metering device is a reservoir oil output metering device or a pressure metering device or a CO2 emission metering device.

[0016] Preferably, the dynamic fracture simulation device is assembled by inserting a dynamic fracture simulation component into a dynamic fracture groove reserved in a reservoir; the dynamic fracture simulation component is composed of a filter plate 1, a sealing baffle 2, a spring component 3, an artificial high-permeability core column 4, a cementing and fixing glue 5, and a shell 6;

[0017] The artificial high permeability core column 4 is cylindrical, and a spring component 3 is installed at each end. The spring component 3 is placed into the frame of the artificial high permeability core column when the artificial high permeability core column is manufactured, and is welded and fixed at the outer connection between the spring component 3 and the two ends of the artificial high permeability core column (4), and the welded assembly is sleeved and fixed on the frame of the artificial high permeability core column 4; the other ends of the two spring components 3 are sleeved with the sealing baffles 2 respectively, and are fixed by welded screw nuts, and the sealing baffles 2 are located at the supporting points in the shell 6; the prepared artificial high permeability core column 4 and the shell 6 are connected and sealed by a bonding fixing glue 5; the two filter plates 1 are respectively fixedly assembled at the outer supporting points at the two ends of the shell 6;

[0018] The condition for selecting the spring length of the spring component is: the length of deformation when the spring is subjected to a preset pressure value.

[0019] Preferably, the working principle of the dynamic fracture simulation device is as follows: the dynamic fracture simulation device is pre-buried in a reserved groove when the reservoir is made, and the dynamic fracture simulation reservoir contains the buried characteristics of dynamic fractures. When the internal and external pressures of the dynamic fracture simulation device are balanced, the spring is in the original state, and it can be known from Hooke's law:

[0020] F=-kx (1)

[0021]

[0022] In the above formula: k – spring coefficient;

[0023] X——stretched or compressed length, cm;

[0024] P——spring pressure, N / mm;

[0025] F——tensile force or compressive force on the spring, N;

[0026] δ——tensile or compressive amount, mm;

[0027] The dynamic fracture simulation component in the original state is in a sealed state. When there is a pressure difference at both ends of the spring and the pressure is greater than the calculated spring pressure P, the left sealing baffle moves to the right, the compression spring shrinks to the right, the left channel opens, and the fluid passes through the artificial high-permeability core, simulating the injection of fluid into the fracture. Under the action of pressure, the right spring stretches to the right, the right sealing baffle moves to the right, and the right channel opens.

[0028] Preferably, the filter plate 1 is used to prevent reservoir cement and fluid impurities from entering the interior of the component; the sealing baffle 2 supports the spring component and moves under the pressure difference to simulate the opening and closing of the crack; the spring component 3 simulates the crack opening pressure; the artificial high permeability core 4 simulates the dynamic fracture equivalent permeability medium; the bonding glue 5 fixes the artificial high permeability core 4 and the shell and plays a sealing role at the same time; the shell 6 is poured to seal the core component to prevent the fluid from flowing from the edge of the core and prevent the formation of a high permeability channel at the edge.

[0029] The present invention provides a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures, which solves the problem that the relevant technologies of the three-dimensional physical simulation method do not consider the dynamic fractures. According to the on-site geological knowledge and dynamic development characteristics of the ultra-low permeability reservoir, the present invention designs a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures. Compared with the existing CO2 displacement experiment, the device can realize the simulation research of dynamic fractures, and can realize the control of the properties, quantity and opening limit pressure of dynamic fractures; realize the simulation development of three-dimensional multi-layer ultra-low permeability oil reservoirs containing dynamic fractures; realize the direct verification of dynamic fracture parameters and production dynamic characteristics; can support the study of the influence of the properties, scale and state of dynamic fractures on the oil recovery efficiency and burial volume during multi-layer joint injection, and combined with the CT scanning method, it has the obvious advantages of visualization and verifiability.

[0030] In another aspect, the present invention provides a CO2 flooding simulation method for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures, the method comprising a single reservoir flooding experimental method, a multi-reservoir same pressure flooding experimental method, a multi-reservoir different pressure flooding experimental method and a multi-reservoir dynamic fracture flooding experimental method;

[0031] The steps of the single reservoir flooding experiment are as follows:

[0032] Step 1: Prepare simulated formation water and simulated crude oil for the experiment;

[0033] Step 2: The multilayer physical device without dynamic cracks is placed in a constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C;

[0034] Step 3: Saturate formation water, saturate reservoirs I, II, ..., and n of the physical model group in turn; first close the inlet valves of reservoirs II, ..., and n, use constant flow displacement mode, let the saturated formation water pass through reservoir I alone, and stop at 20PV. Then saturate reservoirs II, ..., and n in turn;

[0035] Step 4: Saturate the formation crude oil. To ensure full saturation, saturate reservoir I, reservoir II, ..., reservoir n in sequence. First, close the inlet valves of the control valves of reservoir II, ..., reservoir n, and use a constant flow displacement method to allow saturated formation water to pass through reservoir I alone until no water is produced, and record the water output; then saturate reservoir II, ..., reservoir n in sequence, and record the water output.

[0036] Step 6: The displacement medium CO2 gas is kept at a constant temperature of 80°C and a displacement pressure of 13MPa, and is injected into the gas well through a fluid injection pipeline;

[0037] Step 7: Close the bottom control valve of the first flow control device, open the right control valve to allow CO2 gas to enter the reservoir to drive oil, open the first metering device, measure the amount of oil displaced, the outlet pressure and the amount of CO2 discharged, and record the time and related data;

[0038] Step 8: Close the right control valve of the first flow control device and open the bottom control valve; close the bottom control valve of the second flow control device and open the right control valve; allow CO2 gas to enter reservoir II to drive oil, open the second metering device, measure the amount of oil driven, outlet pressure and CO2 discharge, and record the time and related data;

[0039] Step 9: Close the right control valve of the first flow control device and open the bottom control valve. Close the right control valve of the second flow control device and open the bottom control valve; close the bottom control valve of the third flow control device and open the right control valve to allow CO2 gas to enter reservoir III for oil displacement. Open the third metering device to measure the amount of oil displaced, outlet pressure and CO2 discharge, and record the time and related data.

[0040] Similarly, close the right control valves of n-1 flow control devices in turn, and open the n-1 bottom control valves; open the right control valve of the nth flow control device to allow CO2 gas to enter reservoir n to drive oil, open the nth metering device, measure the displaced oil volume, outlet pressure and CO2 emission, and record the time and related data.

[0041] Preferably, the device also includes a multi-reservoir same-pressure driving experiment, the steps of which are as follows:

[0042] Step 2-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment;

[0043] Step 2-2: The multi-layer physical device without dynamic fractures is placed in a constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. A pressure regulator is used at the inlet end of the first and second flow control devices to control the pressure to be the same at 13MPa for oil displacement, and the first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the CO2 emission, and record the relevant data respectively.

[0044] Preferably, the multi-reservoir different pressure flooding experimental method comprises the following steps:

[0045] Step 3-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment;

[0046] Step 3-2: The multi-layer physical device without dynamic fractures is placed in the constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. Pressure regulators are used at the inlet ends of the first and second flow control devices to control the pressure from reservoir I to reservoir III to 10MPa, 13MPa, and 16MPa, respectively, to carry out oil displacement, and the first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the amount of CO2 discharged, and record the relevant data respectively.

[0047] Preferably, in one embodiment, the multi-reservoir dynamic fracture flooding experimental method comprises the following steps:

[0048] Step 4-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment;

[0049] Step 4-2: The multi-layer physical device of dynamic fractures is placed in the constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. A pressure regulator is used at the inlet end of the flow control device to control the same pressure of 13MPa. Under pressure, all fracture channels are opened for oil displacement. The first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the CO2 emission, and record the relevant data respectively.

[0050] The present invention provides a CO2 flooding simulation device and method for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures, which solves the problem that the relevant technologies of the three-dimensional physical simulation method do not consider the dynamic fractures. According to the on-site geological knowledge and dynamic development characteristics of the ultra-low permeability reservoir, the present invention designs a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures. Compared with the existing CO2 displacement experiment, the device can realize the simulation study of dynamic fractures, and can realize the control of the properties, quantity and opening limit pressure of dynamic fractures; realize the simulation development of three-dimensional multi-layer ultra-low permeability oil reservoirs containing dynamic fractures; realize the direct verification of dynamic fracture parameters and production dynamic characteristics; can support the study of the influence of the properties, scale and state of dynamic fractures on the oil recovery efficiency and burial volume during multi-layer joint injection, and combined with the CT scanning method, it has the obvious advantages of visualization and verifiability. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of an embodiment of a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures;

[0052] Figure 2a-1 A front view and left view of a dynamic fracture simulation component of a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir with dynamic fractures;

[0053] Figure 2a-2 A shape diagram of the connection between the baffle and the spring component of a dynamic fracture simulation component of a CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs with dynamic fractures

[0054] Figure 2a-3 A three-dimensional diagram of the spring component of the dynamic fracture simulation component of a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir with dynamic fractures

[0055] Figure 2b A schematic diagram of a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures and a reservoir containing dynamic fractures;

[0056] Figure 3 A single reservoir oil production efficiency diagram of a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir with dynamic fractures;

[0057] Figure 4 A CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs with dynamic fractures, with three layers of injection and production at the same pressure at the same time;

[0058] Figure 5 A CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs with dynamic fractures, with three layers of simultaneous injection and production at different pressures;

[0059] Figure 6 A CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs with dynamic fractures shows the injection and production efficiency diagram of three layers with the same pressure (including dynamic fractures);

[0060] Figure 7 A CO2 storage mass ratio diagram of different reservoir combinations and injection and production methods in a CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs with dynamic fractures;

[0061] Figure 8 Schematic diagram of the structure of a CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures. DETAILED DESCRIPTION

[0062] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0063] On the one hand, the present invention provides a CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures, such as Figure 8 As shown, the device includes 2 cap layers, n reservoir layers, n-1 interlayers, m dynamic fracture simulation devices, n flow control devices, n metering devices, and flow injection pipelines; the reservoir layer is a physical model that includes a dynamic fracture device or does not include a dynamic fracture device, and the interlayer is a physical model without a dynamic fracture; an interlayer and a reservoir layer are a group of rectangular physical models of the same shape, and the reservoir layer and the interlayer layer are placed alternately up and down. The reservoir layer of each group of dynamic fracture physical models contains at least one dynamic fracture simulation component to form a dynamic fracture simulation device, and the left and right ends of the reservoir layer of each group of dynamic fracture simulation devices are respectively drilled with the dynamic fracture simulation component The left end of the reservoir of each group of dynamic fracture simulation devices is connected to the control valve of the corresponding flow control device, and the right end of the reservoir of each group of dynamic fracture simulation devices is connected to the flow metering device; wherein, the dynamic fracture simulation component is pre-buried in a cylindrical groove reserved in the reservoir of each dynamic fracture simulation device, and after pre-buried, the dynamic fracture simulation device is cast and fixed with the proportioned reservoir cement, and the interlayer and the reservoir of the dynamic fracture simulation device are alternately placed to form a physical model group, and the cap layer is used to form n layers of CO2 flooding buried simulation devices with n reservoirs and n-1 interlayers to seal the bottom and the top respectively; wherein, n≥2, m≥1;

[0064] When the control valve of the flow control device at the left end of the reservoir I of the first group of physical models is opened and the bottom control valve is closed, the fluid injection pipeline is injected with the displacement medium CO2 gas at a constant temperature of 20℃~100℃ and a displacement pressure of 2.5MPa~30MPa, and oil displacement is carried out, and the first metering device is opened to measure the amount of oil displaced, the outlet pressure and the amount of CO2 discharged, and the time and related data are recorded;

[0065] When the control valve of the flow control device at the left end of the reservoir II of the second group of physical models is opened and the bottom control valve is closed, the left end control valve of the first group of physical models is closed and the bottom control valve is opened, the fluid injection pipeline is injected with the displacement medium CO2 gas at a constant temperature of 20℃~100℃ and a displacement pressure of 2.5MPa~30MPa, and oil displacement is carried out, the second metering device is opened, and the amount of oil displaced, the outlet pressure and the amount of CO2 discharged are measured, and the time and related data are recorded;

[0066] By analogy, when the nth flow control device is connected to the nth reservoir of the nth group of physical models, the nth meter records the data of the nth group of physical models; when the control pressure of each group of physical models is consistent, the recorded data are the experimental data of the same pressure driving burial of n reservoirs; when the control pressure of each group of physical models is inconsistent, the experimental data of different pressure driving burial of the first, second, ..., n reservoirs are recorded in sequence.

[0067] In one embodiment, the cover layer is used for packaging the bottom and top of the physical simulation model, and the cover layer is made of acrylic board; after the finished cover layer is alternately placed with the reservoir layer and the interlayer, polyvinyl alcohol (PVA) adhesive is used on the outside for gluing and sealing;

[0068] The reservoir is formed by cement, gypsum, and quartz sand of 40-80 meshes in a certain mass ratio, wherein the mass ratio of reservoir I is 1:1:2, the mass ratio of reservoir II is 1:1:3, and the mass ratio of reservoir III is 1:1:4;

[0069] The interlayer is made of cement and gypsum in a bonding mass ratio of 1:1;

[0070] The dynamic fracture simulation device manufactures an artificial high-permeability core column according to the required specifications. The size of the artificial high-permeability core column ranges from φ2.5cm to 10cm. The length of the artificial high-permeability core column is 8cm to 50cm. Quartz sand 1mm to 2mm is used. The cement, gypsum, and quartz sand bonding mass ratio is 1:1:3. The artificial high-permeability core column 4 after solidification and cutting is used to manufacture a dynamic fracture simulation component and is loaded into the dynamic fracture simulation component groove reserved in the reservoir. Then, the mixture of cement and gypsum is poured and fixed; wherein, the cement and gypsum mass ratio is 1:1;

[0071] Among them, the flow control device is used to control the pressure of n reservoirs, and the pressure adjustment range is 2.5MPa to 30MPa.

[0072] In one embodiment, each group of physical models injects CO2 into the control valve of the flow control device, and the control valve is provided at the bottom and right side of the flow control device, and is opened in one direction alone when in use;

[0073] The metering device is a reservoir oil output metering device or a pressure metering device or a CO2 emission metering device.

[0074] In one embodiment, a dynamic fracture simulation device is assembled by inserting a dynamic fracture simulation component into a dynamic fracture groove reserved in a reservoir; the dynamic fracture simulation component is composed of a filter plate 1, a sealing baffle 2, a spring component 3, an artificial high-permeability core column 4, a cementing and fixing glue 5, and a shell 6;

[0075] The artificial high permeability core column 4 is cylindrical, and a spring component 3 is installed at each end. The spring component 3 is placed into the frame of the artificial high permeability core column when the artificial high permeability core column is manufactured, and is welded and fixed at the outer connection between the spring component 3 and the two ends of the artificial high permeability core column (4), and the welded assembly is sleeved and fixed on the frame of the artificial high permeability core column 4; the other ends of the two spring components 3 are sleeved with the sealing baffles 2 respectively, and are fixed by welded screw nuts, and the sealing baffles 2 are located at the supporting points in the shell 6; the prepared artificial high permeability core column 4 and the shell 6 are connected and sealed by a bonding fixing glue 5; the two filter plates 1 are respectively fixedly assembled at the outer supporting points at the two ends of the shell 6;

[0076] The condition for selecting the spring length of the spring component is: the length of deformation when the spring is subjected to a preset pressure value.

[0077] It should be noted that the high permeability of artificial high-permeability core columns refers to high permeability. High permeability in the petroleum industry generally refers to more than 1000 millidarcy, 50-1000 millidarcy is medium permeability, and less than 50 millidarcy is low permeability.

[0078] In one embodiment, the working principle of the dynamic fracture simulation device is as follows: the dynamic fracture simulation device is pre-buried in a reserved groove when the reservoir is made, and the dynamic fracture simulation reservoir contains the buried characteristics of the dynamic fracture. When the pressure inside and outside the dynamic fracture simulation device is balanced, the spring is in the original state, and it can be known from Hooke's law:

[0079] F=-kx (1)

[0080]

[0081] In the above formula: k – spring coefficient;

[0082] X——stretched or compressed length, cm;

[0083] P——spring pressure, N / mm;

[0084] F——tensile force or compressive force on the spring, N;

[0085] δ——tensile or compressive amount, mm;

[0086] The dynamic fracture simulation component in the original state is in a sealed state. When there is a pressure difference at both ends of the spring and the pressure is greater than the calculated spring pressure P, the left sealing baffle moves to the right, the compression spring shrinks to the right, the left channel opens, and the fluid passes through the artificial high-permeability core, simulating the injection of fluid into the fracture. Under the action of pressure, the right spring stretches to the right, the right sealing baffle moves to the right, and the right channel opens.

[0087] In one embodiment, the filter plate 1 is used to prevent reservoir cement and fluid impurities from entering the interior of the component; the sealing baffle 2 supports the spring component and moves under the pressure difference to simulate the opening and closing of the crack; the spring component 3 simulates the crack opening pressure; the artificial high permeability core 4 simulates the dynamic fracture equivalent permeability medium; the bonding glue 5 fixes the artificial high permeability core 4 and the shell and plays a sealing role at the same time; the shell 6 is poured to seal the core component to prevent the fluid from flowing from the edge of the core and prevent the formation of a high permeability channel at the edge.

[0088] The present invention provides a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures, which solves the problem that the relevant technologies of the three-dimensional physical simulation method do not consider the dynamic fractures. According to the on-site geological knowledge and dynamic development characteristics of the ultra-low permeability reservoir, the present invention designs a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures. Compared with the existing CO2 displacement experiment, the device can realize the simulation research of dynamic fractures, and can realize the control of the properties, quantity and opening limit pressure of dynamic fractures; realize the simulation development of three-dimensional multi-layer ultra-low permeability oil reservoirs containing dynamic fractures; realize the direct verification of dynamic fracture parameters and production dynamic characteristics; can support the study of the influence of the properties, scale and state of dynamic fractures on the oil recovery efficiency and burial volume during multi-layer joint injection, and combined with the CT scanning method, it has the obvious advantages of visualization and verifiability.

[0089] Another aspect of the present invention provides a method for simulating CO2 flooding in multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures, the method comprising a single reservoir flooding experimental method, a multi-reservoir same pressure flooding experimental method, a multi-reservoir different pressure flooding experimental method and a multi-reservoir dynamic fracture flooding experimental method;

[0090] The steps of the single reservoir flooding experiment are as follows:

[0091] Step 1: Prepare simulated formation water and simulated crude oil for the experiment;

[0092] Step 2: The multilayer physical device without dynamic cracks is placed in a constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C;

[0093] Step 3: Saturate formation water, saturate reservoirs I, II, ..., and n of the physical model group in turn; first close the inlet valves of reservoirs II, ..., and n, use constant flow displacement mode, let the saturated formation water pass through reservoir I alone, and stop at 20PV. Then saturate reservoirs II, ..., and n in turn;

[0094] Step 4: Saturate the formation crude oil. To ensure full saturation, saturate reservoir I, reservoir II, ..., reservoir n in sequence. First, close the inlet valves of the control valves of reservoir II, ..., reservoir n, and use a constant flow displacement method to allow saturated formation water to pass through reservoir I alone until no water is produced, and record the water output; then saturate reservoir II, ..., reservoir n in sequence, and record the water output.

[0095] Step 6: The displacement medium CO2 gas is kept at a constant temperature of 80°C and a displacement pressure of 13MPa, and is injected into the gas well through a fluid injection pipeline;

[0096] Step 7: Close the bottom control valve of the first flow control device, open the right control valve to allow CO2 gas to enter the reservoir to drive oil, open the first metering device, measure the amount of oil displaced, the outlet pressure and the amount of CO2 discharged, and record the time and related data;

[0097] Step 8: Close the right control valve of the first flow control device and open the bottom control valve; close the bottom control valve of the second flow control device and open the right control valve; allow CO2 gas to enter reservoir II to drive oil, open the second metering device, measure the amount of oil driven, outlet pressure and CO2 discharge, and record the time and related data;

[0098] Step 9: Close the right control valve of the first flow control device and open the bottom control valve. Close the right control valve of the second flow control device and open the bottom control valve; close the bottom control valve of the third flow control device and open the right control valve to allow CO2 gas to enter reservoir III for oil displacement. Open the third metering device to measure the amount of oil displaced, outlet pressure and CO2 discharge, and record the time and related data.

[0099] Similarly, close the right control valves of n-1 flow control devices in turn, and open the n-1 bottom control valves; open the right control valve of the nth flow control device to allow CO2 gas to enter reservoir n to drive oil, open the nth metering device, measure the displaced oil volume, outlet pressure and CO2 emission, and record the time and related data.

[0100] In one embodiment, the device further includes a multi-reservoir same pressure driving experiment, the steps of which are as follows:

[0101] Step 2-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment;

[0102] Step 2-2: The multi-layer physical device without dynamic fractures is placed in a constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. A pressure regulator is used at the inlet end of the first and second flow control devices to control the pressure to be the same at 13MPa for oil displacement, and the first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the CO2 emission, and record the relevant data respectively.

[0103] In one embodiment, the multi-reservoir different pressure flooding experimental method comprises the following steps:

[0104] Step 3-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment;

[0105] Step 3-2: The multi-layer physical device without dynamic fractures is placed in the constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. Pressure regulators are used at the inlet ends of the first and second flow control devices to control the pressure from reservoir I to reservoir III to 10MPa, 13MPa, and 16MPa, respectively, to carry out oil displacement, and the first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the amount of CO2 discharged, and record the relevant data respectively.

[0106] In one embodiment, the multi-reservoir dynamic fracture flooding experimental method comprises the following steps:

[0107] Step 4-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment;

[0108] Step 4-2: The multi-layer physical device of dynamic fractures is placed in the constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. A pressure regulator is used at the inlet end of the flow control device to control the same pressure of 13MPa. Under pressure, all fracture channels are opened for oil displacement. The first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the CO2 emission, and record the relevant data respectively.

[0109] The embodiment of the present invention provides a CO2 flooding simulation method for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures, which solves the problem that the related technologies of the three-dimensional physical simulation method do not consider the dynamic fractures. According to the on-site geological knowledge and dynamic development characteristics of the ultra-low permeability reservoir, the present invention designs a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures. Compared with the existing CO2 displacement experiment, it can realize the simulation study of dynamic fractures, and can realize the control of the properties, quantity and opening limit pressure of dynamic fractures; realize the simulation development of three-dimensional multi-layer ultra-low permeability oil reservoirs containing dynamic fractures; realize the direct verification of dynamic fracture parameters and production dynamic characteristics; can support the study of the influence of dynamic fracture properties, scale and state on the oil recovery efficiency and burial volume during multi-layer joint injection, and combined with the CT scanning method, it has the obvious advantages of visualization and verifiability.

[0110] Embodiment 1

[0111] The present invention designs a CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs with dynamic fractures. The device is based on carbon dioxide flooding and simulates the recovery rate and storage volume of multi-reservoir (3-layer, 4-layer, 5-layer) oil and gas reservoirs under dynamic fracture conditions. This embodiment takes the simulation experiment of 3 reservoirs as an example, and the details are as follows:

[0112] The size of the model produced in the embodiment is 50*50*10 cm in length (L)*width (D)*height (H). Two groups of physical models are used in the embodiment, one group without dynamic cracks and one group with dynamic cracks.

[0113] The multi-layer CO2 flooding simulation device designed by the present invention is as follows: Figure 1 As shown, it mainly includes: 2 cap layers, 3 reservoir layers, 2 interlayers, 3 dynamic fracture devices, 3 flow control devices and 3 flow meter devices;

[0114] 1. Separately make cap layer, reservoir layer and interlayer to form a multi-reservoir physical model.

[0115] The reservoir is made of cement, gypsum, and quartz sand (40-80 mesh) in a certain mass ratio, with a mass ratio of 1:1:2 for reservoir I, 1:1:3 for reservoir II, and 1:1:4 for reservoir III. Three cylindrical grooves of φ5×10cm are reserved, which can also be adjusted to other sizes as needed, ranging from φ5 to 10cm and 10 to 50cm in length. The size is 1-2cm larger than the entire dynamic fracture simulation device, so that there is remaining casting space after the subsequent device is placed. At the same time, three corresponding holes are punched at both ends of the reservoir, with a hole diameter of 3 to 10cm. The holes are punched to facilitate the placement of the flow metering device and the flow control device. The cover layer is made of acrylic board, and the interlayer is made of cement and gypsum (bonding mass ratio of 1:1).

[0116] 2. Dynamic crack simulation device

[0117] The artificial high permeability core column 4 uses quartz sand (1-2mm), and the cement, gypsum, and quartz sand bonding mass ratio is 1:1:3. The artificial high permeability core column after solidification and cutting is used to make dynamic fracture simulation components, which are installed in the dynamic fracture groove reserved in the reservoir, and then cast and fixed with a mixture of cement and gypsum, and the cement and gypsum mass ratio is 1:1; a spring with a deformation of 5mm and a pressure of 5MPa is selected, that is, the opening pressure is 5MPa.

[0118] The dynamic crack simulation component shell 6 is a cylindrical hollow column, which can be disassembled into two identical half-fan-shaped columns. After being cured and cut into the required specifications of the artificial high-permeability core column 4, it is installed in the dynamic crack simulation component. First, the artificial high-permeability core column 4 is coated with a bonding adhesive around it and placed in the reserved position in one half of the fan-shaped column of the shell. After the fixing adhesive is firmly bonded, the outer connection between the spring component 3 and the two ends of the artificial high-permeability core column 4 is welded and fixed, and the sealing plate 2 is placed. The sealing plate 2 has a connection with the spring component 3 for fixing with a nut. When installing, you only need to tighten the nut at the connection, and the installation of the sealing plate 2 is completed. After that, it should just be stuck in the inner supporting points at both ends of the shell 6 to form a sealed space inside. Finally, the filter plate 1 is installed on the corresponding outer supporting points of the shell 6, and the other half of the shell is merged with the part that has been assembled. The other half of the artificial high-permeability core column 4 that is not coated with bonding glue is coated with fixing glue, and the contact parts of the two semi-fan-shaped columns are glued together with fixing glue. After they are firmly glued, the dynamic fracture simulation component is assembled and placed in the dynamic fracture groove reserved in the reservoir. Then, it is cast and fixed with a mixture of cement and gypsum to complete the combination between the dynamic fracture simulation component and the reservoir to form a dynamic fracture simulation device.

[0119] 3. Reservoir settings with dynamic fractures

[0120] Three cylindrical grooves (size of φ5×10 cm) were reserved on the reservoir, and the dynamic fracture simulation device was installed. After the dynamic fracture simulation device was placed, cement with reservoir proportion was used for pouring.

[0121] 4. Physical model assembly

[0122] After the finished cover layer, reservoir layer and interlayer are placed alternately, high-strength solidifying glue is used on the outside for gluing and sealing.

[0123] 5. Dynamic crack simulation components such as Figure 2a-1 , Figure 2a-2 , Figure 2a-3 The structure assembly relationship is shown as follows

[0124] The dynamic fracture simulation component is composed of a filter plate 1, a sealing baffle 2, a spring component 3, an artificial high-permeability core 4, a cementing and fixing glue 5, and an outer shell 6; n spring components 4 are respectively installed at both ends of the cylindrical artificial high-permeability core 4, and the spring components are fixedly embedded at both ends of the core through a pre-welded combination sleeve of the spring components after the manufactured core is placed in the outer shell, and the combination sleeve is welded to the outer shell to fix it; the other ends of the two spring components are sleeved with the sealing baffle 2 and fixed by a welded nut; the prepared artificial high-permeability core 4 and the outer shell 6 are connected and sealed with a cementing and fixing glue 5; two filter plates 1 are respectively assembled and fixed at both ends of the dynamic fracture simulation component;

[0125] Table 1 Basic data of artificial high permeability core

[0126]

[0127] The specific steps of the simulation method are as follows:

[0128] 1. Single reservoir flooding experiment:

[0129] Step 1: Prepare simulated formation water and simulated crude oil for the experiment;

[0130] Step 2: The multi-layer physical device without dynamic cracks is placed in the constant temperature system, the pipelines are connected, and the constant temperature box is heated to 80°C;

[0131] Step 3: Saturate the formation water. To ensure full saturation, saturate reservoir I, reservoir II, and reservoir III in sequence.

[0132] First, close the inlet valves of reservoir II and reservoir III, use constant flow displacement mode, let the saturated formation water pass through reservoir I alone, and stop at 20PV. Then saturate reservoir II and reservoir III in turn.

[0133] Step 4: Saturate the formation crude oil. To ensure full saturation, saturate reservoir I, reservoir II, and reservoir III in sequence. First, close the inlet valves of reservoir II and reservoir III, and use a constant flow displacement method to allow saturated formation water to pass through reservoir I alone. Displace until no water is produced, and record the water output. Then saturate reservoir II and reservoir III in sequence, and record the water output.

[0134] Step 6: Keep the displacement medium CO2 gas at a constant temperature of 80°C and a displacement pressure of 13MPa. Figure 1 Fluid is injected into the pipeline gas injection well;

[0135] Step 7: Close the bottom control valve at the first flow control device, open the right control valve, allow CO2 gas to enter reservoir I to drive oil, open the first metering device, measure the amount of oil displaced, outlet pressure and CO2 discharge, and record the time and related data;

[0136] Step 8: Close the right control valve of the first flow control device and open the bottom control valve. Close the bottom control valve of the second flow control device and open the right control valve. Allow CO2 gas to enter reservoir II to drive oil, open the second metering device, measure the amount of oil displaced, outlet pressure and CO2 discharge, and record the time and related data;

[0137] Step 9: Close the right control valve of the first flow control device and open the bottom control valve. Close the right control valve of the second flow control device and open the bottom control valve. Close the bottom control valve of the third flow control device and open the right control valve to allow CO2 gas to enter reservoir III for oil displacement. Open the third metering device to measure the amount of oil displaced, outlet pressure and CO2 discharge, and record the time and related data. The experimental data and Figure 3 The single reservoir oil production efficiency diagram is shown as follows:

[0138] Table 2 Single reservoir oil production efficiency

[0139] Time (min) Reservoir I oil production efficiency Reservoir II oil production efficiency Reservoir III oil production efficiency 0 0 0 0 50 7.21 6.77 6.42 100 13.52 12.58 11.95 150 21.11 19.74 17.72 200 30.34 28.35 26.47 250 39.65 37.62 34.52 300 45.56 42.11 38.92 350 52.34 47.74 43.34 400 56.15 51.32 44.25 450 58.37 51.67 44.47 500 59.95 51.92 44.62

[0140] 2. Multi-reservoir same pressure driving experiment:

[0141] Step 1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment;

[0142] Step 2: Gas Passage Figure 1Fluid is injected into the steam injection well of the pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, the bottom and right control valves of the first flow control device and the second flow control device are opened, CO2 gas is allowed to enter reservoirs I, II and III, a pressure regulator is used at the inlet end, the control pressure is the same as 13MPa, oil displacement is carried out, the first metering device, the second metering device and the third metering device are opened, the oil volume displaced, the outlet pressure and the CO2 discharge are measured, and the relevant data are recorded. The experimental data and Figure 4 The oil production efficiency of three layers is shown by simultaneous injection and production at the same pressure.

[0143] Table 3 Oil production efficiency of three layers with the same pressure and simultaneous injection and production

[0144] min Reservoir I oil production efficiency Reservoir II oil production efficiency Reservoir III oil production efficiency 0 0 0 0 50 7.21 6.67 6.11 100 15.23 12.15 11.14 150 23.29 19.82 18.65 200 35.35 30.95 28.37 250 45.46 40.01 37.76 300 51.56 44.85 42.34 350 57.79 52.54 47.87 400 62.84 56.32 50.28 450 65.56 57.42 51.85 500 66.67 58.44 52.34

[0145] 3. Multi-reservoir different pressure driving experiment:

[0146] Step 1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment;

[0147] Step 2: Gas Passage Figure 1 Fluid was injected into the steam injection well of the pipeline, the bottom control valve of the third flow control device was closed, the right control valve was opened, the bottom and right control valves of the first flow control device and the second flow control device were opened, and CO2 gas was allowed to enter reservoirs Ⅰ, Ⅱ, and Ⅲ. A pressure regulator was used at the inlet end to control the pressure from reservoir Ⅰ to reservoir Ⅲ to 10MPa, 13MPa, and 16MPa, respectively, to drive oil. The first metering device, the second metering device, and the third metering device were opened to measure the amount of oil displaced, the outlet pressure, and the amount of CO2 discharged, and the relevant data were recorded; as shown in Table 4 Experimental data and Figure 5 The oil production efficiency curve of three layers with different pressures is shown in the figure.

[0148] Table 4 Oil production efficiency of three layers with different pressures at the same time

[0149] min Reservoir I Reservoir II Reservoir III 0 0 0 0 50 7.11 6.61 6.10 100 15.54 14.12 13.83 150 23.65 21.82 21.0 200 35.55 32.91 32.34 250 45.45 43.22 41.77 300 51.13 48.84 47.38 350 57.22 53.32 51.82 400 62.14 58.54 56.21 450 64.57 60.03 57.98 500 65.81 60.28 58.31

[0150] 4. Multi-reservoir dynamic fracture flooding experiment:

[0151] Step 1: Clean the physical model and re-saturate the water and oil according to the single reservoir experiment III;

[0152] Step 2: Gas Passage Figure 1In the steam injection well of the liquid injection pipeline, the third bottom control valve is closed, the right control valve is opened, and the first, second bottom and right control valves are opened to allow CO2 gas to enter reservoirs I, II and III. The three reservoirs all contain dynamic fracture simulation devices. A pressure regulator is used at the inlet end, and the control pressure is the same, all of which are 13 MPa. Under this pressure, all fracture channels are opened to drive oil. The first metering device, the second metering device and the third metering device are opened to measure the amount of oil displaced, the outlet pressure and the amount of CO2 discharged, and record the relevant data, as shown in Table 5. Figure 6 The injection and production efficiency curve of three layers with the same pressure (including dynamic fractures) is shown in the figure.

[0153] Table 5 Injection-production efficiency of three layers with the same pressure (including dynamic fractures)

[0154] min Reservoir I Reservoir II Reservoir III 0 0 0 0 50 7.21 6.63 6.21 100 16.32 12.52 11.32 150 25.55 21.81 18.22 200 33.43 30.01 28.44 250 41.0 38.60 37.86 300 47.24 43.85 42.46 350 54.54 50.56 47.88 400 57.56 53.54 50.21 450 58.84 54.44 51.45 500 59.64 54.43 51.35

[0155] 5. Comparison of CO2 storage mass ratios in different flooding experiments

[0156] Through pressure burial experiments with four different reservoir combination injection and production methods, namely single reservoir injection and production, multi-reservoir injection and production at the same pressure, multi-reservoir injection and production at different pressures, and multi-reservoir injection and production at the same pressure (dynamic fracture), the CO2 injection volume at the inlet end and the CO2 discharge volume at the outlet end of each reservoir were recorded, the experimental data were recorded, and the difference between the two was calculated to obtain the CO2 storage mass ratio of each reservoir under the four different injection methods, as shown in Table 6. Figure 7 The CO2 storage mass ratio of injection-production methods in different reservoir combinations is shown in the figure.

[0157] Table 6 CO2 storage mass ratio in pressure flooding experiment with injection and production methods in different reservoir combinations

[0158]

[0159] The embodiment of the present invention provides a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures, which solves the problem that the relevant technologies of the three-dimensional physical simulation method do not consider the dynamic fracture problem. According to the on-site geological knowledge and dynamic development characteristics of the ultra-low permeability reservoir, the present invention designs a CO2 flooding simulation device for a multi-layer ultra-low permeability oil and gas reservoir containing dynamic fractures. Compared with the existing CO2 displacement experiment, it can realize the simulation study of dynamic fractures, and can realize the control of the properties, quantity and opening limit pressure of dynamic fractures; realize the simulation development of three-dimensional multi-layer ultra-low permeability oil reservoirs containing dynamic fractures; realize the direct verification of dynamic fracture parameters and production dynamic characteristics; simulate the actual situation of CO2 flooding under different reservoir pressures, and effectively improve the understanding of the actual recovery rate of multi-layer ultra-low permeability oil and gas reservoirs under CO2 flooding; simulate the actual situation of CO2 storage under different pressure combinations of multiple reservoirs, and play a quantitative role in studying the CO2 storage effect and storage mass ratio of multi-layer ultra-low permeability oil and gas reservoirs; support the study of the influence of dynamic fracture properties, scale and state on oil recovery efficiency and storage volume during multi-layer joint injection, and combine with CT scanning method to achieve obvious advantages of visualization and verification.

Claims

1. A CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures, characterized in that: The device comprises two cap layers, n reservoir layers, n-1 interlayers, m dynamic fracture simulation devices, n flow control devices, n metering devices, and flow injection pipelines; the reservoir layer is a physical model containing a dynamic fracture device or not containing a dynamic fracture device, and the interlayer is a physical model without dynamic fractures; an interlayer and a reservoir layer form a group of rectangular parallelepiped physical models of the same shape, the reservoir layers and interlayers are placed alternately up and down, the reservoir layer of each group of dynamic fracture physical models comprises at least one dynamic fracture simulation component to form a dynamic fracture simulation device, and the left and right ends of the reservoir layer of each group of dynamic fracture simulation devices are respectively drilled with the dynamic fracture simulation component. The left end of the reservoir of each group of dynamic fracture simulation devices is connected to the control valve of the corresponding flow control device, and the right end of the reservoir of each group of dynamic fracture simulation devices is connected to the flow metering device; wherein, the dynamic fracture simulation component is pre-buried in a cylindrical groove reserved in the reservoir of each dynamic fracture simulation device, and after pre-buried, the dynamic fracture simulation device is cast and fixed with the proportioned reservoir cement, and the interlayer and the reservoir of the dynamic fracture simulation device are alternately placed to form a physical model group, and the cap layer is used to form n layers of CO2 flooding buried simulation devices with n reservoirs and n-1 interlayers to seal the bottom and the top respectively; wherein, n≥2, m≥1; When the control valve of the flow control device at the left end of the reservoir I of the first group of physical models is opened and the bottom control valve is closed, the fluid injection pipeline is injected with the displacement medium CO2 gas at a constant temperature of 20℃~100℃ and a displacement pressure of 2.5MPa~30MPa, and oil displacement is carried out, and the first metering device is opened to measure the amount of oil displaced, the outlet pressure and the amount of CO2 discharged, and the time and related data are recorded; When the control valve of the flow control device at the left end of the reservoir II of the second group of physical models is opened and the bottom control valve is closed, the left end control valve of the first group of physical models is closed and the bottom control valve is opened, the fluid injection pipeline is injected with the displacement medium CO2 gas at a constant temperature of 20℃~100℃ and a displacement pressure of 2.5MPa~30MPa, and oil displacement is carried out, the second metering device is opened, and the amount of oil displaced, the outlet pressure and the amount of CO2 discharged are measured, and the time and related data are recorded; By analogy, when the nth flow control device is connected to the nth reservoir of the nth group of physical models, the nth meter records the data of the nth group of physical models; when the control pressure of each group of physical models is consistent, the recorded data are the experimental data of the same pressure driving burial of n reservoirs; when the control pressure of each group of physical models is inconsistent, the experimental data of different pressure driving burial of the first, second, ..., n reservoirs are recorded in sequence.

2. The CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures according to claim 1 is characterized in that: The cover layer is used for packaging the bottom and top of the physical simulation model, and the cover layer is made of acrylic board; after the finished cover layer is alternately placed with the reservoir layer and the interlayer, polyvinyl alcohol (PVA) adhesive is used on the outside for gluing and sealing; The reservoir is formed by cement, gypsum, and quartz sand of 40-80 meshes in a certain mass ratio, wherein the mass ratio of reservoir I is 1:1:2, the mass ratio of reservoir II is 1:1:3, and the mass ratio of reservoir III is 1:1:4; The interlayer is made of cement and gypsum in a bonding mass ratio of 1:1; The dynamic fracture simulation device is used to manufacture an artificial high-permeability core column according to the required specifications. The size of the artificial high-permeability core column is φ2.5 cm to 10 cm. The length of the artificial high-permeability core column is 8 cm to 50 cm. Quartz sand of 1 mm to 2 mm is used. The cement, gypsum and quartz sand bonding mass ratio is 1:1:

3. The artificial high-permeability core column (4) after solidification and cutting is used to manufacture a dynamic fracture simulation component and is loaded into a dynamic fracture simulation component groove reserved in the reservoir. Then, a mixture of cement and gypsum is poured and fixed. The cement and gypsum mass ratio is 1:

1. The flow control device is used to control the pressure of n reservoirs, and the pressure adjustment range is 2.5MPa to 30MPa.

3. The CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures according to claim 1 is characterized in that: Each group of physical models injects CO2 into the control valve of the flow control device, and the control valve is provided at the bottom and right side of the flow control device, and is opened in one direction alone when in use; The metering device is a reservoir oil output metering device or a pressure metering device or a CO2 emission metering device.

4. The CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures according to claim 2 is characterized in that: The dynamic fracture simulation device is assembled by inserting a dynamic fracture simulation component into a dynamic fracture groove reserved in a reservoir; the dynamic fracture simulation component is composed of a filter plate (1), a sealing baffle (2), a spring component (3), an artificial high-permeability core column (4), a cementing and fixing glue (5), and a shell (6); The artificial high-permeability core column (4) is cylindrical, and is provided with a spring component (3) at each end. The spring component (3) is placed into the frame of the artificial high-permeability core column when the artificial high-permeability core column is manufactured, and is welded and fixed at the outer connection between the spring component (3) and the two ends of the artificial high-permeability core column (4), and is welded and assembled to be sleeved on the frame of the artificial high-permeability core column (4) and fixed; the other ends of the two spring components (3) are sleeved on the sealing baffles (2) respectively, and are fixed by welded screw nuts, and the sealing baffles (2) are located at the supporting points inside the shell (6); the prepared artificial high-permeability core column (4) and the shell (6) are connected and sealed by a bonding and fixing glue (5); the two filter plates (1) are respectively fixedly assembled at the outer supporting points at the two ends of the shell (6); The condition for selecting the spring length of the spring component is: the length of deformation when the spring is subjected to a preset pressure value.

5. The CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures according to claim 4 is characterized in that: The working principle of the dynamic fracture simulation device is as follows: the dynamic fracture simulation device is pre-buried in the reserved groove when the reservoir is made. The dynamic fracture simulation reservoir contains the buried characteristics of dynamic fractures. When the pressure inside and outside the dynamic fracture simulation device is balanced, the spring component is in the original state. It can be known from Hooke's law that: F=-kx (1) In the above formula: k – spring coefficient; X——stretched or compressed length, cm; P——spring pressure, N / mm; F——tensile force or compressive force on the spring, N; δ——tensile or compressive amount, mm; The dynamic crack simulation component in the original state is in a sealed state. When there is a pressure difference at both ends of the spring and the pressure is greater than the calculated spring pressure P, the left sealing baffle moves to the right, the compression spring shrinks to the right, the left channel opens, and the fluid passes through the artificial high-permeability core column, simulating the injection of fluid into the crack. Under the action of pressure, the right spring stretches to the right, the right sealing baffle moves to the right, and the right channel opens.

6. The CO2 flooding simulation device for multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures according to claim 4 is characterized in that: The filter plate (1) is used to prevent reservoir cement and fluid impurities from entering the interior of the component; the sealing baffle (2) supports the spring component and moves under the action of pressure difference to simulate the opening and closing of the crack; the spring component (3) simulates the crack opening pressure; the artificial high-permeability core column (4) simulates the dynamic fracture equivalent permeability medium; the cementing and fixing glue (5) fixes the artificial high-permeability core column (4) and the shell and plays a sealing role at the same time; the shell (6) seals the core component after injection to prevent the fluid from flowing from the edge of the core and prevent the formation of a high-permeability channel at the edge.

7. A method for simulating CO2 flooding in multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures, characterized in that: The method includes a single reservoir flooding experiment method, a multi-reservoir same pressure flooding experiment method, a multi-reservoir different pressure flooding experiment method and a multi-reservoir dynamic fracture flooding experiment method; The steps of the single reservoir flooding experimental method are as follows: Step 1: Prepare simulated formation water and simulated crude oil for the experiment; Step 2: The multilayer physical device without dynamic cracks is placed in a constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; Step 3: Saturate formation water, saturate reservoir I, reservoir II, ..., reservoir n of the physical model group in turn; first close the inlet valves of reservoir II, ..., reservoir n, use constant flow displacement mode to make the saturated formation water pass through reservoir I alone, and displace 20PV; saturate reservoir II, ..., reservoir n in turn; Step 4: Saturate the formation crude oil. To ensure full saturation, saturate reservoir I, reservoir II, ..., reservoir n in sequence; first close the inlet valves of the control valves of reservoir II, ..., reservoir n, and use a constant flow displacement method to allow the saturated formation water to pass through reservoir I alone until no water is produced, and record the water output; Saturate reservoir II, ..., reservoir n in sequence and record the water output; Step 6: The displacement medium CO2 gas is kept at a constant temperature of 80°C and a displacement pressure of 13MPa, and is injected into the gas well through a fluid injection pipeline; Step 7: Close the bottom control valve of the first flow control device, open the right control valve to allow CO2 gas to enter the reservoir to drive oil, open the first metering device, measure the amount of oil displaced, the outlet pressure and the amount of CO2 discharged, and record the time and related data; Step 8: Close the right control valve of the first flow control device and open the bottom control valve; close the bottom control valve of the second flow control device and open the right control valve; allow CO2 gas to enter reservoir II to drive oil, open the second metering device, measure the amount of oil driven, outlet pressure and CO2 discharge, and record the time and related data; Step 9: Close the right control valve of the first flow control device and open the bottom control valve; close the right control valve of the second flow control device and open the bottom control valve; close the bottom control valve of the third flow control device and open the right control valve to allow CO2 gas to enter reservoir III to drive oil, open the third metering device, measure the amount of oil driven, outlet pressure and CO2 discharge, and record the time and related data; Similarly, close the right control valves of n-1 flow control devices in turn, and open the n-1 bottom control valves; open the right control valve of the nth flow control device to allow CO2 gas to enter reservoir n to drive oil, open the nth metering device, measure the displaced oil volume, outlet pressure and CO2 emission, and record the time and related data.

8. The method for simulating CO2 flooding in multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures according to claim 7, characterized in that: The multi-reservoir same pressure driving experiment method comprises the following steps: Step 2-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment; Step 2-2: The multi-layer physical device without dynamic fractures is placed in a constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. A pressure regulator is used at the inlet end of the first and second flow control devices to control the pressure to be the same at 13MPa for oil displacement, and the first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the CO2 emission, and record the relevant data respectively.

9. The method for simulating CO2 flooding in multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures according to claim 7, characterized in that: The multi-reservoir different pressure driving experiment method has the following steps: Step 3-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment; Step 3-2: The multi-layer physical device without dynamic fractures is placed in the constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. A pressure regulator is used at the inlet end of the first flow control device and the second flow control device to control the pressure from reservoir I to reservoir III to 10MPa, 13MPa, and 16MPa, respectively, to carry out oil displacement, and the first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the CO2 emission, and record the relevant data respectively.

10. The method for simulating CO2 flooding in multi-layer ultra-low permeability oil and gas reservoirs containing dynamic fractures according to claim 7, characterized in that: The multi-reservoir dynamic fracture flooding experimental method comprises the following steps: Step 4-1: Clean the physical model and saturate it with water and oil again according to the single reservoir experiment; Step 4-2: The multi-layer physical device of dynamic fractures is placed in the constant temperature system, the fluid injection pipeline is connected, and the constant temperature box is heated to 80°C; the gas is injected into the steam well through the fluid injection pipeline, the bottom control valve of the third flow control device is closed, the right control valve is opened, and the bottom and right control valves of the first and second flow control devices are opened to allow CO2 gas to enter reservoirs I, II, and III. A pressure valve regulator is used at the inlet end of the flow control device to control the same pressure of 13MPa. All fracture channels are opened at the same pressure to drive oil. The first metering device, the second metering device, and the third metering device are opened to measure the amount of oil displaced, the outlet pressure, and the CO2 discharge, and the relevant data are recorded respectively.

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