Structural-Permeability Coupling Simulation Device, System and Analysis Method for Fault Zone

Abstract

The present invention discloses a structure-permeability coupling simulation device, system and analysis method for a fault zone, belonging to the field of geological simulation of oil and gas reservoirs. The simulation device includes a deformation simulation system, a fluid injection system and a terminal control system. The terminal control system controls the deformation simulation system to deform, so as to form a fault zone in the formation, simulate the formation process of the fault zone, and a fluid injection system is provided, which can inject fluid during the formation process of the fault zone or after complete deformation, so as to realize the whole process of simulating the migration and accumulation of fluid in the formation and the fault zone, and thus determine the continuity of shale smear and the relative permeability of the fault zone according to the fluid migration and accumulation process. The critical value for maintaining the continuity of shale smear can also be determined by using the shale smear continuity characterization algorithm based on the fault zone structure characteristic data obtained from multiple experiments, and at the same time, the control factors of shale smear continuity and fault zone permeability are analyzed, providing a basis for fault sealing evaluation and oil and gas exploration and development.

Description

Technical Field

[0001] The present invention relates to the field of geological simulation of oil and gas reservoirs, and in particular to a structure-permeability coupling simulation device, system and analysis method for a fault zone. Background Art

[0002] In oil and gas-bearing basins, the permeability of faults plays a crucial role in the migration, accumulation and distribution of oil and gas. Under actual geological conditions, a fault is not a simple plane, but a zone with a certain structure in three-dimensional space, so it is called a fault zone. The permeabilities of fault zones with different structures are significantly different. Changes in the structure of the fault zone often lead to changes in its permeability, thereby affecting the control of fluid migration and accumulation by the fault. Therefore, the analysis of the coupling relationship between the structural characteristics and permeability characteristics of the fault zone is an important basis for studying the control of fluid migration and accumulation by faults. The research on the structure and permeability of the fault zone can be carried out by field outcrop measurement and core sampling of the underground fault zone. However, these two research methods are greatly affected by the observation range, and the control effects of various factors on the permeability of the fault zone cannot be quantitatively considered, making it difficult to apply to the actual underground geological conditions. By carrying out physical simulation experiments similar to underground geological conditions, the influence of the limitation of the observation range can be avoided, and the coupling relationship between the structural characteristics and permeability characteristics of the fault zone can be quantitatively analyzed under the condition of changing any single influencing factor. However, although the existing fault zone simulation technologies can simulate the formation of the fault zone, they do not simulate the control effect of the fault zone on fluid migration and accumulation through experiments. At present, the determination of the permeability of the fault zone in the experimental simulation method can only be qualitatively judged by observing the macroscopic deformation results, which often leads to large misjudgments of the final results. Especially for the continuity of shale smear in the fault zone, the observation and description of the appearance characteristics cannot truly determine the critical value size. Therefore, such experimental results are often difficult to apply to actual research. In order to more accurately judge the permeability of the fault zone and the continuity of shale smear in the fault zone, the simulation experimental device must be able to simulate the formation of the fault zone structure and also have the functions of fluid injection and fluid migration and accumulation monitoring. Summary of the Invention

[0003] The object of the present invention is to provide a structure-permeability coupling simulation device, system and analysis method for a fault zone, which can realize the simulation of the formation of the fault zone and the process of oil and gas migration and accumulation, and analyze the permeability characteristics and control factors of fault zones with different structures.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A structure-permeability coupling simulation device for a fault zone, comprising: a deformation simulation system, a fluid injection system and a terminal control system;

[0006] The deformation simulation system and the fluid injection system are both connected to the terminal control system;

[0007] The terminal control system is used to set the fault slip rate, the total fault slip displacement, the fluid injection rate, and the fluid injection volume;

[0008] After laying the formation in the deformation simulation system, the terminal control system is used to control the deformation simulation system to deform according to the fault slip rate and the total fault slip displacement, so as to form a fault zone in the formation; the terminal control system is also used to control the fluid injection system to inject fluid into the formation laid in the deformation simulation system to simulate the whole process of fluid migration and accumulation in the formation and the fault zone.

[0009] A structure-permeability coupling simulation system of a fault zone, comprising: a photographing device and the above-mentioned structure-permeability coupling simulation device of the fault zone;

[0010] The photographing device is connected to the terminal control system in the structure-permeability coupling simulation device of the fault zone;

[0011] The photographing device is used to photograph the fault zone evolution image after the terminal control system controls the deformation simulation system to start deforming according to the fault slip rate and the total fault slip displacement; the terminal control system is used to identify the fault zone according to the fault zone evolution image and analyze the formation and evolution process of the fault zone by using the PIV particle image velocimetry technique;

[0012] The photographing device is also used to photograph the fluid migration and accumulation process image in the formation and the fault zone during the process of injecting fluid into the formation; the terminal control system is also used to determine the continuity of the mudstone smear layer and the permeability of the fault zone according to the migration and accumulation process image; the terminal control system is also used to determine the critical value for the mudstone smear to remain continuous and the control factors for the continuity of the mudstone smear layer and the permeability of the fault zone according to the fault zone structure characteristic data;

[0013] The photographing device is also used to photograph the mudstone smear layer image on the fault plane during the dissection of the fault zone structure; the terminal control system is also used to determine whether there are cavities or cracks inside the mudstone smear layer according to the mudstone smear layer image.

[0014] A structure-permeability coupling simulation and analysis method of a fault zone, the simulation and analysis method is applied to the above-mentioned structure-permeability coupling simulation system of the fault zone, and the simulation and analysis method includes:

[0015] Select a fault block with a preset fault dip angle and set it in the structure-permeability coupling simulation device of the fault zone;

[0016] According to the preset experimental stratigraphic model, lay each stratum from bottom to top within the fault block, and inject pure water into the laid stratum until the water injection stops after reaching the highest water level line;

[0017] Control the deformation of the fault block according to the fault slip rate and the total fault slip displacement, so as to form a fault zone in the stratum, and photograph the stratum during the deformation process to obtain the fault zone evolution image;

[0018] After the fault zone is formed, inject colored kerosene into the stratum according to the preset fluid injection rate and fluid injection volume, and photograph the migration and accumulation process images of the colored kerosene in the stratum and the fault zone during the oil injection process;

[0019] According to the fault zone evolution image, use the PIV particle image velocimetry technology to identify the fault zone and analyze the formation and evolution process of the fault zone;

[0020] Excavate and dissect the fault zone structure, photograph the mudstone smear layer image on the fault plane, and determine whether there are cavities or cracks developed inside the mudstone smear layer according to the mudstone smear layer image;

[0021] According to the migration and accumulation process image, determine the continuity of the mudstone smear layer and the permeability of the fault zone;

[0022] Conduct multiple experiments by changing the preset experimental stratigraphic model, fault slip rate and total fault slip displacement, and according to the fault zone structure characteristic data after each experiment, use the mudstone smear continuity characterization algorithm to determine the critical value for the mudstone smear to remain continuous, and at the same time analyze and obtain the control factors for the mudstone smear continuity and the fault zone permeability.

[0023] Optionally, conduct multiple experiments by changing the preset experimental stratigraphic model, fault slip rate and total fault slip displacement, and according to the fault zone structure characteristic data after each experiment, use the mudstone smear continuity characterization algorithm to determine the critical value for the mudstone smear to remain continuous, specifically including:

[0024] Conduct multiple experiments by changing the preset experimental stratigraphic model, fault slip rate and total fault slip displacement, and record the fault zone structure characteristic data after each experiment; the fault zone structure characteristic data includes the minimum thickness of the mudstone smear;

[0025] According to the fault zone structure characteristic data after each experiment, adopt a variety of mudstone smear continuity characterization algorithms to calculate the characterization coefficient values of each mudstone smear layer corresponding to each mudstone smear continuity characterization algorithm;

[0026] Use the statistical method to draw a scatter diagram of the correlation between the characterization coefficient value and the minimum thickness of the mudstone smear;

[0027] According to the scatter plot, select the characterization coefficient with the greatest correlation with the minimum thickness of shale smear as the optimal characterization parameter for the continuity of shale smear;

[0028] Statistically analyze the relationship between the continuity of shale smear and the optimal characterization parameter to obtain the critical value for the continuity of shale smear, which is used as the critical value for fault zone sealing.

[0029] Optionally, it further includes:

[0030] Control the deformation of the fault block according to the fault slip rate, and at the same time inject colored kerosene into the formation according to the preset fluid injection rate and fluid injection volume, and obtain the formation change images during the deformation process in real time;

[0031] When it is observed that colored kerosene leakage starts to occur in the fault zone, stop the deformation and determine the current fault throw as the critical fault throw for leakage in the fault zone.

[0032] According to the specific embodiments provided by the present invention, the following technical effects are disclosed:

[0033] The structure-permeability coupling simulation device, system and analysis method for the fault zone in the embodiments of the present invention. The terminal control system controls the deformation simulation system to deform, so as to form a fault zone in the formation, simulate the formation process of the fault zone, and a fluid injection system is set up, which can inject fluid during the formation process of the fault zone or after complete deformation, so as to realize the whole process of simulation of fluid migration and accumulation in the formation and the fault zone, and thus determine the continuity of shale smear and the relative permeability of the fault zone according to the fluid migration and accumulation process. The critical value for the continuity of shale smear can also be determined by using the shale smear continuity characterization algorithm based on the fault zone structure characteristic data obtained from multiple experiments. At the same time, the control factors of shale smear continuity and fault zone permeability are analyzed, providing a basis for fault sealing evaluation and oil and gas exploration and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0035] Figure 1 It is a schematic structural diagram of a structure-permeability coupling simulation device for a fault zone provided by an embodiment of the present invention;

[0036] Figure 2 It is a schematic diagram of the terminal control system provided by an embodiment of the present invention;

[0037] Figure 3Flowchart of a method for simulating and analyzing the structure-permeability coupling of a fault zone provided by an embodiment of the present invention;

[0038] Figure 4 More specific step block diagram of a method for simulating and analyzing the structure-permeability coupling of a fault zone provided by an embodiment of the present invention;

[0039] Figure 5 Internal friction angle of the saturated water river sand sample used in an embodiment of the present invention And cohesion C parameter determination diagram;

[0040] Figure 6 Completion result diagrams of formation laying and fault deformation of three groups of experiments in an embodiment of the present invention;

[0041] Figure 7 Final migration and accumulation result diagrams after kerosene injection of three groups of experiments in an embodiment of the present invention;

[0042] Figure 8 PIV particle image velocimetry technology analysis diagram of the formation evolution process of the fault zone in Experiment 3 of an embodiment of the present invention;

[0043] Figure 9 Distribution pattern diagram of the upper mudstone smear layer on the fault plane in Experiment 2 of an embodiment of the present invention;

[0044] Figure 10 Scatter diagram of the correlation between the minimum thickness of mudstone smear, mudstone smear coefficient value (SSF), and fault gouge ratio value (SGR) of three groups of experiments in an embodiment of the present invention;

[0045] Figure 11 Statistical histogram of the correlation between the mudstone smear coefficient value (SSF) and fault gouge ratio value (SGR) and continuity of three groups of experiments in an embodiment of the present invention.

[0046] Symbol description:

[0047] Load-bearing platform - 1, waterproof outer box - 2, transmission shaft - 3, fixed base - 4, fault block - 5, scale ruler - 6, highest water level line - 7, digital servo motor - 8, speed-displacement sensor - 9, peristaltic pump - 10, fluid pipeline - 11, fluid injection hole - 12. Detailed implementation manners

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0049] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] Embodiment 1

[0051] As Figure 1 shown, the embodiment of the present invention provides a structure-permeability coupling simulation device for a fault zone, including: a deformation simulation system, a fluid injection system, and a terminal control system.

[0052] Both the deformation simulation system and the fluid injection system are connected to the terminal control system. The terminal control system is used to set the fault slip rate, the total fault slip displacement, the fluid injection rate, and the fluid injection volume. After laying the formation in the deformation simulation system, the terminal control system is used to control the deformation simulation system to deform according to the fault slip rate and the total fault slip displacement, so as to form a fault zone in the formation; the terminal control system is also used to control the fluid injection system to inject fluid into the formation laid in the deformation simulation system to simulate the entire process of fluid migration and accumulation in the formation and the fault zone.

[0053] Among them, the deformation simulation system includes: a fault block 5, a transmission shaft 3, a scale 6, a highest water level line 7, a waterproof outer box 2, and a digital servo motor 8. Both the fault block 5 and the transmission shaft 3 are arranged inside the waterproof outer box 2; the front outer wall of the waterproof outer box 2 is made of a transparent material; a scale 6 is provided on the left side of the front outer wall of the waterproof outer box 2, and a highest water level line 7 is provided on the upper part of the front outer wall of the waterproof outer box 2. The digital servo motor 8 is connected to the fault block 5 through the transmission shaft 3; the digital servo motor 8 is electrically connected to the terminal control system. The scale 6 is used to determine the water level and the thickness of the laid formation. Lay the formation in the fault block 5, and use the fluid injection system to inject pure water into the laid formation until the water injection stops when reaching the highest water level line 7; after the formation is completely water-saturated, the digital servo motor 8, under the control of the terminal control system, makes the fault block 5 deform according to the fault slip rate and the total fault slip displacement through the transmission shaft 3, so as to form a fault zone in the formation. The fluid injection system also injects colored kerosene into the laid formation under the control of the terminal control system to simulate the entire process of fluid migration and accumulation in the formation and the fault zone. The front outer wall of the waterproof outer box 2 is used to facilitate the observation of the formation evolution process of the fault zone and the entire process of colored kerosene migration and accumulation.

[0054] The highest water level line 7 is used to determine the water injection height during the experiment.

[0055] Refer to Figure 1, the fault block 5 includes: a hanging wall and a footwall. The hanging wall includes a first vertical plate, a first parallel bottom plate, and a first inclined plate; one end of the first parallel bottom plate is connected to one end of the first vertical plate, and the other end of the first parallel bottom plate is connected to one end of the first inclined plate; the first parallel bottom plate is connected to the transmission shaft 3. The footwall includes a second vertical plate, a second parallel bottom plate, and a second inclined plate; one end of the second parallel bottom plate is connected to one end of the second vertical plate, and the other end of the second parallel bottom plate is connected to one end of the second inclined plate; the other end of the second inclined plate is fixed to the bottom of the waterproof outer box 2. The first vertical plate and the second vertical plate are oppositely arranged in the vertical direction, one side of the first inclined plate is in contact with one side of the second inclined plate, and under the traction of the transmission shaft 3, the first parallel bottom plate drives the first inclined plate to slide freely along the second inclined plate.

[0056] The deformation simulation system further includes: a fixed base 4, a load-bearing platform 1, and a velocity-displacement sensor 9. The footwall is fixed on the fixed base 4, and at the same time, the fixed base 4 is fixed to the bottom of the waterproof outer box 2. The digital servo motor 8 and the velocity-displacement sensor 9 are both arranged inside the load-bearing platform 1, and the waterproof outer box 2 is fixed on the load-bearing platform 1. The velocity-displacement sensor 9 is connected to the terminal control system, and the velocity-displacement sensor 9 is used to measure the sliding rate and sliding displacement of the hanging wall and transmit them to the terminal control system.

[0057] The fault dip angle of the fault block 5 is 30 ° , 45 ° , 60 ° , 75 ° There are four combinations, which can be selected according to the experimental design requirements. The fault dip angle refers to the angle between the second inclined plate and the bottom of the waterproof outer box 2.

[0058] The fluid injection system includes: a peristaltic pump 10 and a plurality of fluid conduits 11. The peristaltic pump 10 is arranged inside the load-bearing platform 1; a plurality of fluid injection holes 12 are opened on the outer wall of the waterproof outer box 2, the first vertical plate, and the second vertical plate. One fluid injection hole 12 on the outer wall of the waterproof outer box 2 and one fluid injection hole 12 on the first vertical plate are connected to the peristaltic pump 10 through a fluid conduit 11. One fluid injection hole 12 on the outer wall of the waterproof outer box 2 and one fluid injection hole 12 on the second vertical plate are connected to the peristaltic pump 10 through a fluid conduit 11. The peristaltic pump 10 is connected to the terminal control system; the peristaltic pump 10 is used to pump fluid into the fault block 5 through the fluid conduits 11 under the control of the terminal control system.

[0059] Exemplarily, both the left and right outer walls (the first vertical plate and the second vertical plate) of the waterproof outer box 2 and the fault block 5 are provided with 3 columns × 8 rows of fluid injection holes 12. The fluid injection holes 12 without inserted fluid conduits 11 are in a sealed state.

[0060] Specifically, the fluid delivery pipeline 11 is made of a non-lipophilic material, thereby reducing the influence of pipeline viscous force on fluid injection.

[0061] As Figure 2 shown, the terminal control system includes: a digital servo motor 8 control program and a peristaltic pump 10 control program, which can control the fault slip rate, total slip displacement, fluid injection rate and injection volume through computer software programs.

[0062] The simulation device of the present invention is particularly suitable for simulating soft sediment fault zones.

[0063] The embodiments of the present invention have the following beneficial effects:

[0064] 1. The experimental device of the present invention is easy to operate and has a high degree of visualization, and can simulate the whole process of the formation of fault zones with different dips under different formation structures, different deformation rates and different deformation displacements.

[0065] 2. The front outer wall of the experimental device of the present invention is designed to be transparent for easy observation of the formation and evolution process of the fault zone and the analysis of the fault zone structure. At the same time, the present invention uses PIV particle image velocimetry technology to identify the fault zone structure and analyze the formation and evolution process of the fault zone.

[0066] 3. The whole process of the formation of the fault zone simulated by the present invention can be completed under the condition of complete water saturation. At the same time, the experimental device of the present invention is provided with a fluid injection system, which can inject fluid during the formation of the fault zone or after complete deformation, so as to realize the whole process of the migration and accumulation of the simulated fluid in the formation and the fault zone, and the continuity of mudstone smear and the relative permeability of the fault zone can be determined according to the fluid migration and accumulation process.

[0067] Embodiment 2

[0068] The embodiment of the present invention provides a structure-permeability coupling simulation system for a fault zone, including: a photographing device and a structure-permeability coupling simulation device for a fault zone in Embodiment 1.

[0069] The photographing device is connected to the terminal control system in the structure-permeability coupling simulation device for a fault zone.

[0070] The photographing device is used to photograph the evolution images of the fault zone after the terminal control system controls the deformation simulation system to start deforming according to the fault slip rate and the total fault slip displacement; the terminal control system is used to identify the fault zone according to the evolution images of the fault zone and analyze the formation and evolution process of the fault zone by using PIV particle image velocimetry technology.

[0071] The photographing device is also used to photograph the image of the migration and accumulation process of the fluid in the formation and the fault zone during the process of injecting the fluid into the formation; the terminal control system is also used to determine the continuity of the mudstone smear layer and the permeability of the fault zone according to the image of the migration and accumulation process; the terminal control system is also used to determine the critical value for the mudstone smear to remain continuous and the control factors for the continuity of the mudstone smear layer and the permeability of the fault zone according to the structural characteristic data of the fault zone.

[0072] The photographing device is also used to photograph the image of the mudstone smear layer on the fault plane when analyzing the structure of the fault zone; the terminal control system is also used to determine whether there are voids or cracks inside the mudstone smear layer according to the image of the mudstone smear layer.

[0073] Embodiment III

[0074] The embodiment of the present invention provides a method for simulating and analyzing the structure-permeability coupling of a fault zone. The simulation and analysis method is applied to the structure-permeability coupling simulation system of the fault zone in Embodiment II, as Figure 3 shown, the simulation and analysis method includes:

[0075] Step 1: Select a fault block 5 with a preset fault dip angle and place it in the structure-permeability coupling simulation device of the fault zone.

[0076] The fault dip angles of the fault block 5 are a total of 30 ° , 45 ° , 60 ° , 75 ° There are four combinations. Before the experiment starts, select the fault block 5 with the corresponding dip angle according to the experimental design requirements and load it into the model device. The specific operation is to fix the footwall of the selected fault block 5 on the fixed base 4 using a screw rod, connect the bottom of the hanging wall to the transmission shaft 3 using a screw rod, and then restore the initial displacement of the fault sliding block to zero to ensure that the bottom plates of the footwall and hanging wall of the fault block 5 are on the same horizontal line before the simulation experiment starts.

[0077] Step 2: Lay each formation in the fault block 5 from bottom to top according to the preset experimental formation model, and inject pure water into the laid formation until the water injection stops after reaching the highest water level line 7.

[0078] According to the preset experimental model design, lay each formation in the fault block 5 from bottom to top. In order to make the kerosene injected later migrate along the formation towards the fault direction, the formation attitude needs to be laid in an inclined shape or high in the middle and low on both wings.

[0079] After the formation is laid, inject pure water into the waterproof outer box 2, keep the water level rising uniformly and slowly, ensure that the laid formation is completely wetted by water, and stop the water injection after the water level reaches the highest water level line 7.

[0080] Step 3: Control the fault block 5 to deform according to the fault slip rate and the total displacement of the fault slip, so that a fault zone is formed in the stratum, and photograph the stratum during the deformation process to obtain an evolution image of the fault zone.

[0081] After the formation is completely saturated with water, the fault deformation rate and final displacement size are set in the terminal control system according to the experimental design requirements. After the deformation begins, photos are taken at equal time intervals to record the fault deformation process.

[0082] Step 4: After the fault zone is formed, colored kerosene is injected into the formation according to the pre-set fluid injection rate and fluid injection amount, and images of the migration and accumulation process of the colored kerosene in the formation and fault zone are captured during the injection process.

[0083] After the fault is formed, colored kerosene is injected into the designated stratum according to the injection rate designed in the experiment. It should be noted that the injection rate should not be too high to prevent the clay layer from rupturing. During the injection process, photos are taken at equal intervals to record the kerosene migration and accumulation process.

[0084] Step 5: Based on the fault zone evolution image, the PIV particle image velocimetry technique is used to identify the fault zone and analyze the formation and evolution process of the fault zone.

[0085] After the experiment is completed, the deformation rate and deformation displacement set by the terminal control system are recorded, and photos taken at equal time intervals from the beginning to the end of deformation are collected. The PIV particle image velocimetry technology is used to identify the fault zone and analyze the formation and evolution process of the fault zone.

[0086] Step 6: Excavate and dissect the fault zone structure, take an image of the mudstone smear layer on the fault plane, and determine whether cavities or cracks are developed inside the mudstone smear layer based on the image of the mudstone smear layer.

[0087] Read and record the relevant data of the fault zone structural characteristics such as the mudstone layer thickness, fault distance, and minimum thickness of the mudstone smear after the experimental deformation, and then excavate and dissect the fault zone structure. First, the water in the sand box is completely drained, and then the sand layer overlying the mudstone layer is peeled off layer by layer. In this process, the overlying thick sand layer is first removed with a shovel. To prevent human damage to the mudstone smear layer, a hair dryer is used to slowly blow away the sand attached to the mudstone layer when peeling close to the mudstone layer until the mudstone smear layer is completely exposed. Then observe and take pictures to record the structure and morphology of the mudstone smear layer on the fault plane to determine whether there are cavities or cracks inside the smear layer.

[0088] Step 7: Based on the migration and accumulation process image, determine the continuity of the mudstone smear layer and the permeability of the fault zone.

[0089] By observing the migration and accumulation of kerosene after encountering a fault, the continuity of shale smear and the permeability of the fault zone are determined. If kerosene migrates across the fault zone (kerosene leakage), it indicates that the shale smear developed within the fault zone loses continuity, and the fault zone is in a leakage state, showing relatively high permeability characteristics. If kerosene forms an accumulation due to being blocked by the fault zone (kerosene does not leak), it indicates that the shale smear developed within the fault zone is continuous, and the fault zone is in a closed state, showing relatively low permeability characteristics.

[0090] Step 8: Conduct multiple experiments by changing the preset experimental formation model, fault slip rate, and total fault slip displacement. According to the fault zone structure characteristic data after each experiment, use the shale smear continuity characterization algorithm to determine the critical value for the shale smear to remain continuous, and simultaneously analyze and obtain the control factors of shale smear continuity and fault zone permeability.

[0091] After determining the continuity of the shale smear and the permeability of the fault zone based on the leakage situation of kerosene, for existing shale smear continuity characterization algorithms, such as the shale smear factor (SSF) and the gouge ratio (SGR), calculate the actual values of the corresponding characterization algorithms, and use statistical methods to draw a scatter plot of the correlation between the actual values calculated by each characterization algorithm and the minimum thickness of the shale smear. Select the optimal characterization parameter for shale smear continuity according to the correlation between the two. Then, statistically analyze the relationship between the shale smear continuity and the actual values of the optimal characterization parameter to obtain the critical value for the shale smear to remain continuous and the critical values for the fault zone to be closed / leaky. On this basis, conduct experiments by changing experimental conditions such as the formation composition, deformation rate, and fault zone displacement, and the control factors of shale smear continuity and fault zone permeability can be analyzed.

[0092] The injection of colored kerosene in Step 4 can also be carried out during the formation of the fault. According to one experiment, the critical fault displacement for the fault to leak can be determined. The specific process is as follows: Control the fault block 5 to deform at the fault slip rate, and at the same time inject colored kerosene into the formation according to the preset fluid injection rate and fluid injection volume, and obtain the formation change images during the deformation in real time. When it is observed that the colored kerosene starts to leak in the fault zone, stop the deformation, and determine the current fault displacement as the critical fault displacement for the fault zone to leak.

[0093] Such as Figure 4 As shown below, a more specific implementation process of the structure-permeability coupling simulation and analysis method for the fault zone is provided.

[0094] (1) Prepare experimental materials

[0095] Prepare the experimental materials required for formation laying according to the experimental design requirements. In this embodiment, river sand is selected as sandstone, and clay is selected as shale. Two dyes, red and yellow, are used to color kerosene respectively, and at the same time, a sufficient amount of pure water is prepared.

[0096] (2) Testing the physical properties and mechanical properties parameters of experimental materials

[0097] Before the experiment starts, test and record the density and viscosity of kerosene and pure water, the particle size, porosity, permeability and mechanical properties parameters of the experimental materials required for the formation laying. Among them, the strength of mechanical properties is characterized by the internal friction angle. The larger the internal friction angle, the greater the shear strength. In this embodiment, a strain direct shear apparatus is used to test the shear strength τ under different normal stresses σ n , and then according to the Coulomb-Mohr failure criterion to determine the internal friction angle and cohesion C. Figure 5 The figure shows the determination diagram of the internal friction angle and cohesion C parameters of the saturated water and river sand sample in this embodiment. The shear strength τ corresponds to Figure 5 the vertical coordinate shear stress in Figure 5 The angle between the tangent of the circle in and the horizontal axis is the internal friction angle The intersection point of the tangent of the circle and the vertical axis is the cohesion C. Table 1 shows the determination results of the relevant parameters of the kerosene and pure water used in this embodiment, and Table 2 shows the determination results of the physical properties and mechanical properties parameters of the experimental materials required for the formation laying in this embodiment.

[0098] Table 1 Determination results of relevant parameters of kerosene and pure water

[0099]

[0100] Table 2 Determination results of physical properties and mechanical properties parameters of experimental materials required for formation laying

[0101]

[0102] (3) Loading the fault block 5 required for the experiment and restoring the initial displacement

[0103] According to the experimental design requirements and experimental purposes, select the fault block 5 that meets the dip angle requirements. The fault dip angles of the fault block 5 are 30 ° , 45 ° , 60 ° , 75 ° There are four combinations in total. In this embodiment, the fault block 5 with a dip angle of 60 ° is selected. The specific operation is to fix the footwall of the selected fault block 5 on the fixed base 4 using a screw rod, connect the bottom of the hanging wall to the transmission shaft 3 using a screw rod, and then restore the initial displacement of the fault sliding block to zero, ensuring that the bottom plates of the footwall and hanging wall of the fault block 5 are on the same horizontal line before the simulation experiment starts.

[0104] (4) Laying the formation according to the preset experimental model

[0105] According to the preset experimental model design, each stratum is laid sequentially from bottom to top within the fault block 5. To enable the kerosene injected later to migrate along the stratum towards the fault direction, the attitude of the stratum needs to be laid in an inclined shape or with a higher middle and lower wings. A total of three groups of simulation experiments were conducted in this embodiment: Experiment 1, Experiment 2, and Experiment 3. The strata laid in Experiment 1 and Experiment 3 are the same. The laying results of the three groups of experiments are as Figure 6 shown. The mudstone layer is Figure 6 the three light - colored curved layers in

[0106] (5) Saturate the stratum with water

[0107] After the stratum is laid, pure water is injected into the waterproof outer box 2, and the water level is kept rising uniformly and slowly to ensure that the laid stratum is completely wetted by water. Stop injecting water after the water level reaches the highest water level line 7.

[0108] (6) Simulate the formation of the fault

[0109] After the stratum is completely saturated with water, set the deformation displacement magnitude and deformation rate in the terminal control system according to the experimental design requirements. In this embodiment, the deformation displacements set in Experiment 1, Experiment 2, and Experiment 3 are 9 cm, 9 cm, and 6.5 cm respectively, and the deformation rate is set to 1.6 mm / min. Take photos at equal time intervals to record the fault deformation process after the deformation starts. The final deformation results of the three groups of experiments are as Figure 6 shown.

[0110] (7) Inject colored kerosene and observe the process of kerosene migration and accumulation

[0111] After the fault is formed, inject colored kerosene into the specified stratum at the oil injection rate designed in the experiment. It should be particularly noted that the oil injection rate should not be too large to prevent the clay layer from cracking. In this embodiment, yellow kerosene is injected first in each group of experiments, and after the yellow kerosene migration and accumulation are completed, red kerosene is injected. The oil injection rate is 0.05 ml / min, and photos are taken at equal time intervals during the oil injection process to record the process of kerosene migration and accumulation. The final oil injection results of the three groups of experiments are as Figure 7 shown.

[0112] (8) Analysis of the formation and evolution process of the fault zone

[0113] Record the deformation rate and deformation displacement set in the terminal control system, collect the photos taken at equal time intervals from the start to the end of the deformation process, and then use the PIV particle image velocimetry technology to identify the fault zone and analyze the formation and evolution process. As Figure 8The figure shows the fault zone formation evolution process analysis diagram of Experiment 3 in this embodiment. In the initial stage of experimental deformation, although the fault zone cannot be identified macroscopically, the PIV image shows that a nearly vertical bottom leader fault is first formed at the bottom of the sand box, while the middle activity is still very weak and no fault is formed. At the same time, a top leader fault with a fault attitude nearly consistent with that of fault block 5 is also developed at the top of the sand box; then, as the fault throw gradually increases, another new fault zone appears on the right side of the bottom leader fault and propagates rapidly upward; when the fault throw is 4.3 cm, the sandstone and mudstone layers in the right fault zone are significantly thinned due to the strong shear action, and The pre-existing fault on the left side was weak in activity, so the sandstone and mudstone layers were only slightly thinned, and the mudstone layer in the middle began to develop mudstone smears first. The PIV image showed that the branch fault on the left side approached the fault on the right side, almost connecting to form a unified fault zone. When the fault distance reached 6.5 cm, shear-type mudstone smears of different thicknesses had developed in the right fault zone, and the fault zone on the left side had been in a weakly active state for a long time, with only a certain degree of shearing. The PIV image showed that the branch fault on the left side in the previous stage had completely lost its activity, and the main branch fault on the right side was connected to the top fault to form a fault zone consistent with the fault attitude of fault block 5.

[0114] (9) Analysis of fault zone structure

[0115] Read and record the relevant data of the fault zone structural characteristics such as the thickness of the mudstone layer, fault distance, and minimum thickness of the mudstone smear after the experimental deformation, and then excavate and dissect the fault zone structure. First, the water in the sandbox is completely drained, and then the sand layer overlying the mudstone layer is peeled off layer by layer. In this process, the overlying thick sand layer is first removed with a shovel. In order to prevent artificial damage to the mudstone smear layer, the sand attached to the mudstone layer is slowly blown away with a hair dryer when peeling close to the mudstone layer until the mudstone smear layer is completely exposed. Then observe and take pictures to record the structure and morphology of the mudstone smear layer on the fault plane to determine whether there are cavities or cracks inside the smear layer. Figure 9 This is the distribution morphology of the upper mudstone smear layer on the fault plane of Experiment 2 in this embodiment. Multiple steps can be seen on the fault plane, indicating the segmented characteristics of the fault plane, and no voids and cracks are found macroscopically, indicating that the continuity of the smear is relatively good.

[0116] (10) Determination of mudstone smear continuity and fault zone permeability

[0117] By observing the migration and accumulation of kerosene after encountering faults, the continuity of shale smear and the permeability of fault zones are determined. If kerosene migrates across the fault zone (kerosene leakage), it indicates that the shale smear developed within the fault zone has lost continuity, and the fault zone is in a leakage state, showing relatively high permeability characteristics; if kerosene accumulates due to being blocked by the fault zone (kerosene does not leak), it indicates that the shale smear developed within the fault zone is continuous, and the fault zone is in a closed state, showing relatively low permeability characteristics. According to this method, the leakage situation of kerosene is statistically analyzed, and based on this, it is judged whether the corresponding shale smear is continuous. Table 3 records the leakage situation of kerosene in three groups of experiments in this embodiment and the judged continuity of shale smear accordingly.

[0118] (11) Data statistics and analysis of the coupling relationship between "structure - permeability" of fault zones

[0119] After determining the continuity of shale smear and the permeability of fault zones based on the leakage situation of kerosene, the SSF values and SGR values of shale smear for each layer are calculated according to the shale smear factor (SSF) and shale gouge ratio (SGR) formulas. The calculation formula for SSF is: SSF = Throw / Thickness, where Throw is the fault throw and Thickness is the thickness of a single shale layer; the calculation formula for SGR is: SGR = ∑(Thickness) / Throw, where Throw is the fault throw and ∑(Thickness) is the cumulative shale layer thickness passing through a certain point. The final calculation results are shown in Table 3. Then, using statistical methods, scatter plots of the correlation between the minimum shale smear thickness and SSF values and SGR values are respectively drawn. The statistical results are as Figure 10 shown. Figure 10 Part (a) in Figure 10 shows the scatter plot of the correlation between the minimum shale smear thickness and SSF values, Figure 10 and part (b) shows the scatter plot of the correlation between the minimum shale smear thickness and SGR values. Taking the scatter plot of Experiment 1 shown in part (a) of Figure 10 as an example, each point in Experiment 1 corresponds to the correlation between the minimum shale smear thickness and SSF values for a point selected in the shale smear layer. The results show that as the SSF value gradually increases, the minimum shale smear thickness gradually decreases, and there is a good correlation between the two, while the correlation between the SGR value and the minimum shale smear thickness is poor. Therefore, in this embodiment, SSF is more suitable than SGR for characterizing the development of shale smear.

[0120] On this basis, as shown in Figure 11 , the correlation between the SSF values and SGR values of each layer of smear and the smear continuity is respectively statistically analyzed and made into a histogram. Figure 11 Part (a) in Figure 11Part (b) in it shows the correlation histogram between the SGR value and the smear continuity. The statistical result shows that the critical value of smear continuity can be determined according to the SSF value, while this critical value cannot be determined according to the SGR value, which is consistent with the conclusion obtained from the previous analysis of the correlation between the minimum shale smear thickness and the SSF value and the SGR value. Therefore, the critical value for the fault zone to maintain sealing can be determined by using the statistical relationship between the SSF value and the smear continuity. In this embodiment, the critical SSF value for the shale smear to maintain continuity is between 5.171 - 5.534. When the SSF value is lower than 5.171, the shale smear remains continuous. At this time, the corresponding minimum shale smear thickness is relatively large, and the fault zone is in a sealed state, showing relatively low permeability characteristics. When the SSF value is higher than 5.534, the shale smear loses continuity. At this time, the corresponding minimum shale smear thickness is relatively small, and the fault zone is in a leakage state, showing relatively high permeability characteristics. When the SSF value is between 5.171 and 5.534, there is a risk that the shale smear loses continuity.

[0121] Table 3 Record Table of Kerosene Leakage Situation and SSF Values and SGR Values of Each Shale Smear Layer

[0122]

[0123]

[0124] In Table 3, E1, E2, and E3 respectively represent Experiment 1, Experiment 2, and Experiment 3, and C1, C2, and C3 represent three shale smear layers.

[0125] The beneficial effect of the embodiment of the present invention is that in this embodiment, the formation and evolution process of the fault zone structure is analyzed by combining the PIV particle image velocimetry technology, and the structural characteristics of the fault zone, such as sandstone entrainment and the thickness of the shale smear layer, etc., are described in detail. At the same time, according to the migration and accumulation process of kerosene, the continuity of the shale smear layer and the relative permeability of the fault zone are determined, and the critical value for the shale smear to maintain continuity and the critical value for fault sealing / leakage are defined. On this basis, by changing the composition and deformation conditions of the laid formation for experiments, the control factors of shale smear continuity and fault zone permeability can be analyzed. The fault sealing / leakage critical value and its control factors obtained according to the present invention can be used in the actual research of fault sealing evaluation and oil and gas exploration and development.

[0126] The embodiment of the present invention has the following beneficial effects:

[0127] 1. Based on the quantitative description of the structural characteristics of the fault zone, the present invention can determine the parameters suitable for characterizing the shale smear continuity according to the correlation between the numerical values of each shale smear continuity characterization algorithm and the minimum shale smear thickness.

[0128] 2. The present invention can determine the critical value for the fault zone to remain sealed by statistically characterizing the relationship between the numerical value of the shale smear continuity parameter and the leakage / preservation in the fault zone. By repeating the experiment by changing parameters such as the formation composition of the laid layer, the deformation rate, and the displacement of the fault zone, the control factors of shale smear continuity and fault zone permeability can be obtained.

[0129] The various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0130] Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for simulating and analyzing the structure-permeability coupling of a fault zone, characterized in that The simulation and analysis method is applied to a structure-permeability coupling simulation system for a fault zone. The structure-permeability coupling simulation system includes: a photographing device and a structure-permeability coupling simulation device for the fault zone; The simulation and analysis method includes: Select a fault block with a preset fault dip angle and place it in the structure-permeability coupling simulation device for the fault zone; According to a preset experimental stratigraphic model, lay each stratum in the fault block from bottom to top in sequence, and inject pure water into the laid stratum until the water injection stops after reaching the highest water level line; Control the fault block to deform according to the fault slip rate and the total fault slip displacement, so as to form a fault zone in the stratum, and photograph the stratum during the deformation process to obtain an image of the evolution of the fault zone; After the fault zone is formed, inject colored kerosene into the stratum according to the preset fluid injection rate and fluid injection volume, and photograph the migration and accumulation process of the colored kerosene in the stratum and the fault zone during the oil injection process; According to the fault zone evolution image, use the PIV particle image velocimetry technology to identify the fault zone and analyze the formation and evolution process of the fault zone; Excavate and dissect the structure of the fault zone, photograph the shale smear layer image on the fault plane, and determine whether there are cavities or fractures developed inside the shale smear layer according to the shale smear layer image; Determine the continuity of the shale smear layer and the permeability of the fault zone according to the migration and accumulation process image; Conduct multiple experiments by changing the preset experimental stratigraphic model, fault slip rate and total fault slip displacement, and according to the fault zone structure characteristic data after each experiment, use the shale smear continuity characterization algorithm to determine the critical value for the shale smear to remain continuous, and at the same time analyze and obtain the control factors for the shale smear continuity and the fault zone permeability.

2. The structure-permeability coupling simulation and analysis method of the fault zone according to claim 1, characterized in that Conduct multiple experiments by changing the preset experimental stratigraphic model, fault slip rate and total fault slip displacement, and according to the fault zone structure characteristic data after each experiment, use the shale smear continuity characterization algorithm to determine the critical value for the shale smear to remain continuous, specifically including: Conduct multiple experiments by changing the preset experimental stratigraphic model, fault slip rate and total fault slip displacement, and record the fault zone structure characteristic data after each experiment; the fault zone structure characteristic data includes the minimum thickness of the shale smear; According to the fault zone structure characteristic data after each experiment, use a variety of shale smear continuity characterization algorithms to calculate the characterization coefficient values of each shale smear layer corresponding to each shale smear continuity characterization algorithm; Use statistical methods to draw a scatter plot of the correlation between the characterization coefficient value and the minimum thickness of the shale smear; According to the scatter plot, select the characterization coefficient with the greatest correlation with the minimum thickness of the shale smear as the optimal characterization parameter for the shale smear continuity; Statistically analyze the relationship between the shale smear continuity and the optimal characterization parameter to obtain the critical value for the shale smear to remain continuous, and use it as the critical value for the fault zone to be sealed.

3. The structure-permeability coupling simulation and analysis method of the fault zone according to claim 1, characterized in that It also includes: Control the fault block to deform according to the fault slip rate, and at the same time inject colored kerosene into the stratum according to the preset fluid injection rate and fluid injection volume, and obtain the stratum change image during the deformation process in real time; When it is observed that colored kerosene leakage starts to occur in the fault zone, stop the deformation and determine the current fault offset as the critical fault offset at which leakage occurs in the fault zone.

4. The structural-permeability coupling simulation and analysis method for a fault zone according to claim 1, characterized in that The structure-permeability coupling simulation device for the fault zone includes: a deformation simulation system, a fluid injection system, and a terminal control system; Both the deformation simulation system and the fluid injection system are connected to the terminal control system; The terminal control system is used to set the fault slip rate, the total fault slip displacement, the fluid injection rate, and the fluid injection volume; After laying the formation in the deformation simulation system, the terminal control system is used to control the deformation simulation system to deform according to the fault slip rate and the total fault slip displacement, so as to form a fault zone in the formation; the terminal control system is also used to control the fluid injection system to inject fluid into the formation laid in the deformation simulation system to simulate the whole process of fluid migration and accumulation in the formation and the fault zone.

5. The structure-permeability coupling simulation and analysis method for a fault zone according to claim 4, characterized in that The deformation simulation system includes: a fault block, a transmission shaft, a scale ruler, a highest water level line, a waterproof outer box, and a digital servo motor; Both the fault block and the transmission shaft are arranged inside the waterproof outer box; the front outer wall of the waterproof outer box is made of transparent material; a scale ruler is provided on the left side of the front outer wall of the waterproof outer box, and a highest water level line is provided on the upper part of the front outer wall of the waterproof outer box; The digital servo motor is connected to the fault block through the transmission shaft; the digital servo motor is electrically connected to the terminal control system; The scale ruler is used to determine the water level and the thickness of the laid formation; Lay the formation in the fault block, and use the fluid injection system to inject pure water into the laid formation until the water injection stops when reaching the highest water level line; after the formation is completely water-saturated, the digital servo motor, under the control of the terminal control system, makes the fault block deform according to the fault slip rate and the total fault slip displacement through the transmission shaft, so as to form a fault zone in the formation; The fluid injection system also injects colored kerosene into the laid formation under the control of the terminal control system to simulate the whole process of fluid migration and accumulation in the formation and the fault zone; The front outer wall of the waterproof outer box is used to facilitate the observation of the formation and evolution process of the fault zone and the whole process of colored kerosene migration and accumulation.

6. The structural-permeability coupling simulation and analysis method of the fault zone according to claim 5, characterized in that The fault block includes: an upper plate and a lower plate; The upper plate includes a first vertical plate, a first parallel bottom plate, and a first inclined plate; one end of the first parallel bottom plate is connected to one end of the first vertical plate, and the other end of the first parallel bottom plate is connected to one end of the first inclined plate; the first parallel bottom plate is connected to the transmission shaft; The lower plate includes a second vertical plate, a second parallel bottom plate, and a second inclined plate; one end of the second parallel bottom plate is connected to one end of the second vertical plate, and the other end of the second parallel bottom plate is connected to one end of the second inclined plate; the other end of the second inclined plate is fixed to the bottom of the waterproof outer box; The first vertical plate and the second vertical plate are arranged opposite to each other in the vertical direction, one side of the first inclined plate is in contact with one side of the second inclined plate, and the first parallel bottom plate drives the first inclined plate to slide freely along the second inclined plate under the traction of the transmission shaft.

7. The structural-permeability coupling simulation and analysis method of the fault zone according to claim 6, characterized in that The deformation simulation system further includes: a fixed base, a load-bearing platform, and a velocity-displacement sensor; The lower plate is fixed on the fixed base, and at the same time the fixed base is fixed to the bottom of the waterproof outer box; Both the digital servo motor and the velocity-displacement sensor are arranged inside the load-bearing platform, and the waterproof outer box is fixed on the load-bearing platform; The velocity-displacement sensor is connected to the terminal control system. The velocity-displacement sensor is used to measure the sliding rate and sliding displacement of the upper plate and transmit them to the terminal control system.

8. The structure-permeability coupling simulation and analysis method of the fault zone according to claim 7, characterized in that The fluid injection system includes: a peristaltic pump and a plurality of fluid conduits; The peristaltic pump is arranged inside the load-bearing platform; a plurality of fluid injection holes are provided on the outer wall of the waterproof outer box, the first vertical plate, and the second vertical plate; One fluid injection hole on the outer wall of the waterproof outer box and one fluid injection hole on the first vertical plate are connected to the peristaltic pump through a fluid conduit; One fluid injection hole on the outer wall of the waterproof outer box and one fluid injection hole on the second vertical plate are connected to the peristaltic pump through a fluid conduit; The peristaltic pump is connected to the terminal control system; the peristaltic pump is used to pump the fluid into the fault block through the fluid conduit under the control of the terminal control system.

9. The method for simulating and analyzing the structure-permeability coupling of a fault zone according to claim 4, wherein The fault dip angles of the fault blocks are 30°, 45°, 60°, and 75°.

10. The structural-permeability coupling simulation and analysis method for a fault zone according to claim 1, wherein The photographing device is connected to the terminal control system in the structure-permeability coupling simulation device of the fault zone; The photographing device is used to photograph the evolution image of the fault zone after the terminal control system controls the deformation simulation system to start deforming according to the fault sliding rate and the total fault sliding displacement; the terminal control system is used to identify the fault zone based on the evolution image of the fault zone and analyze the formation and evolution process of the fault zone; The photographing device is also used to photograph the migration process image of the fluid in the formation and the fault zone during the process of injecting the fluid into the formation; the terminal control system is also used to determine the continuity of the mudstone smear layer and the permeability of the fault zone based on the migration process image; the terminal control system is also used to determine the critical value for the mudstone smear to remain continuous and the control factors for the continuity of the mudstone smear layer and the permeability of the fault zone based on the fault zone structure characteristic data; The photographing device is also used to photograph the mudstone smear layer image on the fault plane during the dissection of the fault zone structure; the terminal control system is also used to determine whether there are cavities or fractures developed inside the mudstone smear layer based on the mudstone smear layer image.

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