A modeling method and device for muddy interlayers at meandering river point dams

Abstract

The present invention relates to a modeling method and device for muddy interlayers at point-bars of a meandering river, the method comprising: obtaining geological parameters of a meandering river, generating a river channel vector midline including a plurality of control points, and calculating the curvature of each control point; simulating the river channel and muddy interlayers of the meandering river according to the river channel vector midline and the geological parameters to obtain a meandering river grid model; and eroding the muddy interlayers using a preset ellipsoid removal algorithm to obtain a meandering river point-bar muddy interlayer river channel model. The present invention depicts the interlayers of a meandering river, can more realistically display the geomorphic features of the meandering river, and can simulate the erosion process of the muddy interlayers using a preset ellipsoid removal algorithm, can more objectively and accurately simulate the interlayers of the meandering river, and provides a reliable theoretical tool for the study of meandering rivers.

Description

Technical Field

[0001] The invention relates to the technical field of geological modeling, and in particular to a modeling method and device for muddy interlayers at point bars in meandering rivers. Background Art

[0002] Fluvial reservoirs are the focus of current reservoir research and the main target of development, adjustment and potential tapping. Meandering river reservoirs refer to underground reservoirs formed in meandering river systems, in which sediments brought by river movement accumulate and deposit in the riverbed or riverbank area, eventually forming geological layers with certain storage capacity. The formation of meandering river reservoirs is closely related to the geomorphic characteristics of meandering rivers. Meandering rivers are generally single-channel rivers with a sinuosity index >1.5, relatively stable channels and low width / depth ratios. Lateral erosion and accumulation cause the riverbed to migrate toward the concave bank, and point sand bars are formed on the convex bank. Mud interlayers have a great influence on the vertical permeability of reservoirs. 0.01-0.1 meter thick shale-rich mudstone and sandstone interlayer inclusions (i.e., shale vertical cover) exist on the bottom surface of river channels and channel belts and on the top surface of lobes and lobate complexes, which have an important influence on the reservoir properties of clastic reservoirs such as turbidites, shallow marine facies and fluvial reservoirs.

[0003] As the core content of modern reservoir description research, domestic and foreign scholars have carried out a lot of research on modeling methods and applications. The target-based modeling method (Fluvsim) designed by CV Deutsch can better characterize the genetic relationship of different reservoir structural units and is an important fluvial reservoir modeling method. This method can quantitatively describe the configuration of fluvial reservoirs based on the research of fluvial sedimentation. Different from the traditional target-based method, the Fluvsim method has the following characteristics: 1. It has a clear and reversible coordinate hierarchy system; 2. It controls the geometric shape of the target body by input parameters that reflect geological significance; 3. It can accurately control the phase ratio in the vertical direction. However, since the curvature of the meandering river will affect the retention and erosion of the lateral accumulation layer, and the curvature of the river channel is different at different locations, it is necessary to differently characterize the retention and erosion of the mud interlayer, and then erode the interlayer according to the retention degree of the interlayer, so as to simulate the mud interlayer more objectively and reasonably.

[0004] Therefore, it is necessary to propose a modeling method and device for mud interlayers in meandering river point bars, which can characterize the mud interlayers in combination with the geomorphic characteristics of the meandering river, simulate the migration process of the meandering river, and further simulate the erosion of the interlayers, so as to characterize the mud interlayers in meandering river point bars more objectively and reasonably. Summary of the invention

[0005] In view of this, the present invention provides a modeling method and device for mudstone interlayers in meandering river point bars, so as to solve the technical problem that the existing river simulation model is unable to effectively create and simulate the erosion of mudstone interlayers in meandering river point bars, resulting in a lack of accurate research tools for reservoir research on meandering rivers and an inability to provide theoretical guidance for the development of meandering river reservoirs.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a modeling method for muddy interlayers at point bars in meandering rivers, comprising:

[0008] Acquire geological parameters of the meandering river, determine a river channel vector centerline including a plurality of control points according to the geological parameters, and calculate the curvature of each control point on the vector centerline;

[0009] Establishing an initial grid model, assigning values ​​to the initial grid model according to the river channel vector centerline and geological parameters, simulating the river channel and mud interlayer of the meandering river, and obtaining a meandering river grid model;

[0010] The mud interlayer in the meandering river grid model is stripped by using a preset ellipsoid removal algorithm to obtain a meandering river point-bar mud interlayer channel model.

[0011] Furthermore, the initial grid model is assigned values ​​according to the river channel vector centerline and geological parameters, and the river channel and mud interlayer of the meandering river are simulated, including:

[0012] Determine the range of the river channel in the initial grid model according to the center line of the river channel vector, and group all grids within the range of the river channel, each group of grids having the same plane coordinates;

[0013] The number of grids occupied by mudstone interlayers is determined according to the geological parameters, several grids with the smallest longitudinal coordinate index in each group of grids are modified into mudstone phases, and the mudstone interlayers in the meandering river grid model are simulated based on the mudstone phases.

[0014] Furthermore, the method further comprises:

[0015] Simulating the migration process of the meandering river according to the curvature of each control point to obtain multi-stage river channels and mud interlayers;

[0016] The preset ellipsoid removal algorithm is used to erode the mud interlayer of each period in the meandering river grid model.

[0017] Furthermore, the migration process of the meandering river is simulated according to the curvature of each control point to obtain multiple river channels and muddy interlayers, including:

[0018] The migration process of the meandering river includes multiple migration phases, and each migration phase includes multiple migration iterations;

[0019] Determine a migration coefficient according to the curvature of each control point, and calculate the transformed position of the control point after a single migration under the migration coefficient;

[0020] Calculating the migration distance of the river channel according to the transformed position and the original position of the control point, and accumulating the migration distance after each river channel migration to obtain a cumulative migration distance;

[0021] When the cumulative migration distance exceeds a preset distance threshold, a layer of mud interlayer is simulated in the meandering river grid model to obtain a first-stage river channel and mud interlayer;

[0022] The multi-stage migration process of the meandering river is simulated to obtain multi-stage river channels and mud interlayers.

[0023] Furthermore, the method further comprises:

[0024] After a single migration, the distance between any two control points is calculated. When the distance between any two control points is less than the preset river channel width, all control points between the two control points are removed, and the two control points are directly connected to form a new vector centerline;

[0025] Among them, the multiple control points that are removed are connected to form an abandoned river channel, and the abandoned river channel does not migrate or change.

[0026] Furthermore, the migrated muddy interlayer in the meandering river grid model is denuded using a preset ellipsoid removal algorithm, including:

[0027] generating an ellipsoid in the meandering river grid model, removing muddy interlayers within the ellipsoid, and simulating the erosion process of the muddy interlayers;

[0028] Each time the muddy interlayer within the ellipsoid is removed is an iteration. After each iteration, the mud content of the muddy interlayer in the meandering river grid model is calculated. When the mud content is reduced to a preset content threshold, the iteration is stopped.

[0029] Further, based on the curvature of the control point, a random simulation algorithm is used to interpolate in the meandering river network model space to generate a three-dimensional probability field;

[0030] The center position of the ellipsoid is determined according to the three-dimensional probability field.

[0031] Furthermore, the curvature includes a curvature direction and a curvature magnitude;

[0032] Calculating the curvature of each control point on the vector midline includes:

[0033] Determine a circumscribed circle according to each control point and two control points adjacent to the control point;

[0034] The reciprocal of the radius of the circumscribed circle is the curvature of the control point, and the direction from the center of the circumscribed circle to the control point is the curvature direction.

[0035] In a second aspect, the present invention further provides a modeling device for muddy interlayers at a meandering river point bar, comprising:

[0036] An analysis and calculation module, used for obtaining geological parameters of a meandering river, determining a river channel vector center line including a plurality of control points according to the geological parameters, and calculating the curvature of each control point on the vector center line;

[0037] A model building module is used to build an initial grid model, assign values ​​to the initial grid model according to the river channel vector centerline and geological parameters, simulate the river channel and mud interlayer of the meandering river, and obtain a meandering river grid model;

[0038] The erosion simulation module is used to erode the mud interlayer in the meandering river grid model using a preset ellipsoid removal algorithm to obtain a meandering river point-bar mud interlayer river channel model.

[0039] In a third aspect, the present invention further provides a computer-readable storage medium for storing computer-readable programs or instructions, which, when executed by a processor, can implement the steps in the modeling method of mud interlayers at meandering river point bars in any of the above-mentioned implementation methods.

[0040] The present invention provides a modeling method for muddy interlayers at point-bars of meandering rivers. First, a river channel vector midline is established based on the geological parameters of the meandering river, and the curvature of each control point on the vector midline is calculated; secondly, the initial grid model is assigned according to the river channel vector midline and the geological parameters, and the river channel and muddy interlayers of the meandering river are simulated to obtain a meandering river grid model; finally, the erosion process of the muddy interlayers is simulated using a preset ellipsoid removal algorithm to obtain a final meandering river point-bar muddy interlayer river channel model. The method of the present invention depicts the river channel and interlayers of the meandering river. By adding muddy interlayers on the basis of river channel simulation, the geomorphic features of the meandering river can be more realistically displayed. According to the law of erosion and retention of lateral accumulation body layers in practice, a corresponding algorithm is designed to simulate the erosion process of muddy interlayers, thereby simulating the interlayers of the meandering river more objectively and accurately, providing a reliable theoretical tool for the study of meandering rivers. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of the Fluvsim method for depicting river channel objects using the river channel centerline;

[0042] Figure 2 A method flow chart of an embodiment of a modeling method for muddy interlayers at point bars in meandering rivers provided by the present invention;

[0043] Figure 3 A schematic diagram of the structure of an embodiment of a river vector midline provided by the present invention;

[0044] Figure 4 A schematic diagram of an embodiment of curvature calculation provided by the present invention;

[0045] Figure 5 A schematic diagram of an embodiment of assigning values ​​to a grid provided by the present invention;

[0046] Figure 6 A cross-sectional schematic diagram of an embodiment of a river channel migration process provided by the present invention;

[0047] Figure 7 A schematic diagram of an embodiment of a river channel truncation process provided by the present invention;

[0048] Figure 8 A schematic diagram of an embodiment of a meandering river point-bar muddy interlayer channel model obtained after erosion simulation of muddy interlayer provided by the present invention;

[0049] Fig. 9 A structural schematic diagram of an embodiment of a modeling device for muddy interlayers at point bars in meandering rivers provided by the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0051] Before introducing the embodiments of the present invention, the inventive concept of the present application is first described.

[0052] Meandering river reservoir refers to the underground reservoir formed in the meandering river system, in which the sediments brought by the river movement accumulate and settle in the riverbed or riverbank area, eventually forming a geological layer with a certain storage capacity. The reservoir is generally sandstone, in which oil and gas resources are contained, and the non-reservoir is mudstone, which will block the extraction of oil and gas, so the mud interlayer has a greater impact on the recovery rate of clastic reservoirs. 0.01-0.1 meter thick shale-rich mudstone and sandstone interlayer inclusions, that is, shale cap, exist on the bottom surface of rivers and channel belts and the top surface of lobes and lobes, which have an important impact on the reservoir properties of clastic reservoirs such as turbidites, shallow marine phases and river reservoirs.

[0053] When muddy interlayers are present in large quantities (generally covering more than 50% to 70% of the area), they need to be modeled and characterized in the channel model. Proper representation of these boundary shales in the simulation model is critical, but not all geological modeling methods can create muddy interlayers in static models, and there is still a lack of a standard workflow for creating muddy interlayers.

[0054] In the prior art, the target-based hierarchical simulation Fluvsim algorithm is often used to characterize the geometric morphology of river channels. The ideal model of the river channel characterized by the Fluvsim method includes three types of sedimentary phases, namely river channel filling, natural levee, and breach fan, in addition to the background phase, which can fully reflect the vertical and planar superposition and combination of various sedimentary bodies. The geometric morphology of the target body of various phase types can be controlled by parameter files. The parameters are generally determined by geological research, mainly including field outcrops, earthquakes, well logging, sedimentary simulation experiments, geological knowledge bases and other related information.

[0055] like Figure 1 As shown in the figure, the basic idea of ​​the Fluvsim method is: generate a number of channel centerline nodes according to the main direction of the river channel, connect the channel centerline nodes to form the channel centerline, and then establish a channel profile along the channel centerline. The channel profile is horizontally lengthened and accumulated in the main direction of the river channel, thereby establishing a three-dimensional river model.

[0056] Under the influence of lateral erosion and accumulation, the riverbed of the meandering river migrates to the concave bank, and a point bar is formed on the convex bank. As the meandering river channel continues to migrate laterally, the sand bodies on the inner bank of the point bar continue to accumulate laterally to form multiple lateral accumulation bodies. With the periodic flooding, fine-grained mud or silt deposits are formed on the edge and bottom of the lateral accumulation body at the end of the previous flood period. When the next flood peak arrives, the previous fine-grained deposits will be scoured, and fine-grained deposits will be formed again when the flood peak subsides. This cycle repeats and forms a meandering river point bar separated by lateral accumulation layers between multiple lateral accumulation bodies.

[0057] Based on the Fluvsim method, this application adds the simulation of the lateral accumulation layer of the point-bar and removes the simulation of the natural levee and the breach fan, thereby focusing on the geomorphological characteristics of the meandering river and demonstrating the influence of the mud interlayer on the reservoir seepage capacity during the lateral migration of the point-bar. In addition, the retention and erosion of the lateral accumulation layer of the meandering river have certain laws. According to the laws, the corresponding modeling algorithm is developed to characterize the retention and erosion of the lateral accumulation layer, thereby establishing a more accurate and objective river reservoir model, providing a theoretical basis for the study of the reservoir of the meandering river.

[0058] The present invention provides a modeling method, device, electronic device and computer-readable storage device for mud interlayers at point bars in a meandering river, which are respectively described below.

[0059] Combination Figure 2As shown, a specific embodiment of the present invention discloses a modeling method for muddy interlayers at point bars of meandering rivers, comprising:

[0060] Step S101, obtaining geological parameters of a meandering river, determining a river channel vector centerline including a plurality of control points according to the geological parameters, and calculating the curvature of each control point on the vector centerline;

[0061] Step S102, establishing an initial grid model, assigning values ​​to the initial grid model according to the river channel vector centerline and geological parameters, simulating the river channel and mud interlayer of the meandering river, and obtaining a meandering river grid model;

[0062] Step S103: using a preset ellipsoid removal algorithm to erode the muddy interlayer in the meandering river grid model to obtain a meandering river point-bar muddy interlayer channel model.

[0063] Compared with the prior art, the method of this embodiment firstly establishes the channel vector centerline based on the geological parameters of the meandering river, and calculates the curvature of each control point on the vector centerline; secondly, the initial grid model is assigned according to the channel vector centerline and the geological parameters, and the channel and mud interlayer of the meandering river are simulated to obtain the meandering river grid model; finally, the erosion process of the mud interlayer is simulated using the preset ellipsoid removal algorithm to obtain the final meandering river point bar mud interlayer channel model. The method of the present invention depicts the channel and interlayer of the meandering river, and by adding mud interlayers on the basis of the channel simulation, the geomorphological characteristics of the meandering river can be more realistically displayed; according to the law of erosion and retention of the lateral accumulation body layer of the meandering river in practice, a corresponding algorithm is designed to simulate the erosion process of the mud interlayer, so as to simulate the meandering river interlayer more objectively and accurately, and provide a reliable theoretical tool for the study of meandering river reservoirs.

[0064] As a specific embodiment, step S101 refers to the idea of ​​using the center line to represent the river channel in the Fluvsim method, and implements river channel simulation in the form of vector center line. The geological parameters of the meandering river include the initial point, azimuth, control point spacing, maximum offset distance and total length.

[0065] Combine the following Figure 3 The method of generating a vector median line is described.

[0066] The initial point is the center line of the river, i.e. the first point of the vector line. Figure 3 The hollow circle represents the location of the initial point;

[0067] The azimuth indicates the main direction of the river channel. The initial point is taken as the coordinate origin, the east (E) direction is 0 degrees, and the angle corresponding to the main direction rotated counterclockwise is the azimuth.

[0068] The control point spacing indicates the spacing of the river control points in the main direction. The distance between the scales in the main direction of the river vector line diagram is the control point spacing. A control point will be generated at a certain interval along the main direction of the river.

[0069] The maximum offset distance indicates the maximum distance from the control point to the main direction. It is used to limit the control point to a certain range on both sides of the main direction axis. The maximum offset distance also determines the curvature of the river channel. A river channel control point is generated at every control point spacing along the main direction of the river channel. The distance of the control point deviating from the main direction is sampled between the negative maximum offset distance and the positive maximum offset distance, and is generally generated by a random function.

[0070] The total length indicates the farthest range of the river channel extension. When the distance between the generated river channel control point and the initial point is greater than the total length of the river channel, the generation of the next river channel control point will stop. At this point, the initial control point of the centerline of the river channel is generated.

[0071] Furthermore, based on the initial control point of the river centerline, the vector centerline is smoothed and encrypted to obtain the river centerline point set, which is a collection of a series of spatial point coordinates, which is the river centerline vector we ultimately need. The vector centerline can quantitatively represent the river centerline. Once the vector centerline is determined, the spatial position and basic form of the meandering river can be determined.

[0072] In a preferred embodiment, the curvature includes a curvature direction and a curvature magnitude;

[0073] Calculating the curvature of each control point on the vector midline includes:

[0074] Determine a circumscribed circle according to each control point and two control points adjacent to the control point;

[0075] The reciprocal of the radius of the circumscribed circle is the curvature of the control point, and the direction from the center of the circumscribed circle to the control point is the curvature direction.

[0076] As a specific embodiment, after the river channel vector centerline is generated, the curvature needs to be calculated for each control point on the vector centerline. The curvature represents the curvature of the river channel, including two quantitative parameters: the curvature direction and the curvature magnitude. The curvature calculation method for a single control point is as follows:

[0077] Except for the first and last control points, each control point on the vector midline has two adjacent control points. The current control point and the two adjacent control points can form a circumscribed circle. The curvature is the inverse of the radius of the circumscribed circle, and the curvature direction is from the center of the circle to the current control point.

[0078] It should be noted that if the current control point and two adjacent control points are collinear and there is no circumscribed circle, the curvature is 0 and the curvature has no direction. The larger the curvature, the more curved the centerline of the river.

[0079] like Figure 4 As shown, the small circle on the solid line represents the control point, the large dotted circle represents the circumscribed circle, the small solid circle inside the circumscribed circle represents the center of the circumscribed circle, and the arrow represents the direction of curvature.

[0080] In a preferred embodiment, in step S102, the initial grid model is assigned values ​​according to the river channel vector center line and geological parameters, and the river channel and mud interlayer of the meandering river are simulated, including:

[0081] Determine the range of the river channel in the initial grid model according to the center line of the river channel vector, and group all grids within the range of the river channel, each group of grids having the same plane coordinates;

[0082] The number of grids occupied by mudstone interlayers is determined according to the geological parameters, several grids with the smallest longitudinal coordinate index in each group of grids are modified into mudstone phases, and the mudstone interlayers in the meandering river grid model are simulated based on the mudstone phases.

[0083] As a specific embodiment, a channel profile is established along the center line of the channel. The channel profile is horizontally lengthened and accumulated in the main direction of the channel, so as to establish a three-dimensional channel model based on the initial grid model, and the three-dimensional model is gridded. The channel profile morphology at each channel centerline control point is determined. The channel profile morphology includes the channel depth, the channel top width, and the channel bottom width. These three parameters are set by the user as geological parameters. Each grid within the channel range is traversed, and the grid is assigned a value according to the positional relationship between the grid and the channel: when the grid is in the channel, it is assigned a channel phase, otherwise it is a non-channel phase.

[0084] like Figure 5 As shown in the figure, the solid line represents the center line of the river channel, and the distance between the dashed line and the solid line represents the maximum width of the river channel on the plane. When the center point of the grid is within the dashed line, the grid is considered to be inside the river channel. Specifically, the grid can be regarded as a point, and the river channel can be regarded as a line with a certain width. According to the distance formula from the point to the line segment, the distance from the grid to the center line of the river channel can be calculated. If the distance is greater than half the width of the river channel, the grid is outside the river channel. If the distance is less than half the width of the river channel, it is further judged on the section.

[0085] The calculation formula of river channel profile parameters is as follows:

[0086]

[0087] Among them, w(y) is the width of the river, c v (y) is the local curvature, is the maximum curvature.

[0088] When a(y)≤0.5, the depth of the channel base below the channel top is:

[0089]

[0090] Among them, b(y)=-ln(2) / ln(a(y)), w∈[0,w(y)];

[0091] When a(y)>0.5, the depth of the channel base below the channel top is:

[0092]

[0093] Among them, c(y)=-ln(2) / ln(1-a(y)),

[0094] The above judgment method can be used to determine whether the grid is within the river channel, thereby assigning a value to the grid.

[0095] As a specific embodiment, after each river channel simulation is completed, a layer of mud interlayer is simulated at the bottom of the river channel. The specific method is: according to the mudstone interlayer thickness parameter in the geological parameters input by the user, combined with the size of the three-dimensional model grid, calculate how many grids the mudstone interlayer should occupy (based on experience, generally 1-2 grids).

[0096] River migration is generally divided into two parts, lateral migration and vertical migration, which are often carried out simultaneously. Lateral migration is calculated on a plane, and the control point moves along the curvature direction. The size of the movement is related to the size of the curvature. By analyzing the actual sedimentation situation, the greater the curvature (i.e., the more curved the river channel), the faster the migration rate. In actual processing, the single migration distance at the most curved and straight parts of the river channel is inconsistent. Generally, the migration step length at the most curved part is given, and the migration conversion coefficient is calculated for other places based on the curvature.

[0097] Assume that the original coordinates of the control point are (x, y, z) and the curvature direction is (v x ,v y ,0), the curvature is c, and the single migration coefficient is k xy , then: after the plane migration, the new coordinates of the control point are (x+v x *c*k xy ,y+v y *c*k xy ,z).

[0098] In the vertical direction, the migration is usually superimposed upwards, and the migration coefficient k can also be defined z , after vertical migration, the new coordinates of the control point are (x+v x *c*kxy ,y+v y *c*k xy ,z+k z ).

[0099] When simulating a single channel, we traverse all grids within the single channel range to assign values ​​to the grids, and determine which grids belong to the channel and which do not. Here, we group all grids belonging to the channel, and each group of grids has the same plane coordinates, that is, the same XY coordinates. According to the number of grids occupied by mudstone interlayers, the n grids with the smallest Z coordinate index in each group of grids are modified to mudstone phases, thereby achieving the purpose of adding mud interlayers in the channel simulation.

[0100] As the meandering river channel continues to migrate laterally, the sand bodies on the inner bank of the point-bar continue to accumulate laterally to form multiple lateral accumulation bodies. Accompanied by periodic floods, fine-grained mud or silt deposits are formed at the edge and bottom of the lateral accumulation body at the end of the previous flood period. When the next flood peak arrives, the previous fine-grained deposits are scoured, and fine-grained deposits will be formed again when the flood peak recedes. This cycle repeats and forms a meandering river point bar separated by lateral accumulation layers between multiple lateral accumulation bodies. In order to characterize the influence of mud interlayers on the reservoir seepage capacity during the lateral migration of the meandering river point bar, it is necessary to simulate the migration process of the meandering river.

[0101] In a preferred embodiment, the method further comprises:

[0102] Simulating the migration process of the meandering river according to the curvature of each control point to obtain multi-stage river channels and mud interlayers;

[0103] The preset ellipsoid removal algorithm is used to erode the mud interlayer of each period in the meandering river grid model.

[0104] In a preferred embodiment, the migration process of the meandering river is simulated according to the curvature of each control point to obtain multiple river channels and muddy interlayers, including:

[0105] The migration process of the meandering river includes multiple migration phases, and each migration phase includes multiple migration iterations;

[0106] Determine a migration coefficient according to the curvature of each control point, and calculate the transformed position of the control point after a single migration under the migration coefficient;

[0107] Calculating the migration distance of the river channel according to the transformed position and the original position of the control point, and accumulating the migration distance after each river channel migration to obtain a cumulative migration distance;

[0108] When the cumulative migration distance exceeds a preset distance threshold, a layer of mud interlayer is simulated in the meandering river grid model to obtain a first-stage river channel and mud interlayer;

[0109] The multi-stage migration process of the meandering river is simulated to obtain multi-stage river channels and mud interlayers.

[0110] As a specific example, Figure 6 As shown, Figure 6 The middle is a cross section of the river channel. In each period of the river channel, the bottom of each column is modified to a mudstone interlayer represented by a space. Figure 6 It can be seen that the river channel migration period is two periods, indicating that the river channel has migrated for two periods (after two periodic floods). The figure shows a three-stage river channel, and the mudstone interlayers of the previous period will be covered by the river channel deposited later. However, the migration algorithm performs more than two migrations, because the migration step size should be small enough to ensure a smooth transition of the migration process.

[0111] The migration step size (the average migration distance of the river nodes after the migration algorithm is executed once) is related to the grid size and is generally set to a single grid size. The curvature direction and curvature size need to be recalculated each time the migration process is iterated. This can ensure a smooth transition of the migration and avoid distortion of the river morphology.

[0112] It should be noted that mud interlayers are not simulated after each migration during the river migration process. The form of interlayers is related to the periodic flooding effect. We decide whether to simulate interlayers based on the cumulative migration distance of the river. When the cumulative migration distance of the river exceeds the user input value, an interlayer is simulated. During the migration iteration process, only the river vector centerline is updated, and no grid update is performed.

[0113] When it is necessary to simulate the river channel and interlayer, a grid update is performed. Figure 6 Two phases of river migration were performed, with several migrations performed in each phase. After one phase was completed, grid assignment was performed to simulate the river channel and interlayer. By simulating the migration of meandering rivers, the influence of mud interlayers on the reservoir seepage capacity during the lateral migration of meandering river point bars was characterized, thereby more realistically depicting the structure of meandering rivers.

[0114] In a preferred embodiment, the method further comprises:

[0115] After a single migration, the distance between any two control points is calculated. When the distance between any two control points is less than the preset river channel width, all control points between the two control points are removed, and the two control points are directly connected to form a new vector centerline;

[0116] Among them, the multiple control points that are removed are connected to form an abandoned river channel, and the abandoned river channel does not migrate or change.

[0117] As a specific embodiment, when the river channel performs the above migration process, the curvature of the river channel will gradually increase, and the river channel control points will gradually approach each other. When the distance between the river channel control points is less than the river channel width (the cutoff threshold is input by the user, generally the river channel width), the river channel will be straightened to form an oxbow lake. After the control points are cut off, the river channel is abandoned, and no water flows through it. The migration process stops and the migration algorithm is no longer executed.

[0118] Therefore, the algorithm adds the distance judgment between control points, such as Figure 7 As shown, each time the river migration is iterated, the distance between the control points is checked. If the distance between any two control points is less than a given threshold, the river is truncated, all control points between the two control points are removed, and the current two control points are directly connected to form a new vector centerline.

[0119] In order to simulate the process of erosion and retention of muddy interlayers, in a preferred embodiment, a preset ellipsoid removal algorithm is used to erode the migrated muddy interlayers in the meandering river grid model, including:

[0120] generating an ellipsoid in the meandering river grid model, removing muddy interlayers within the ellipsoid, and simulating the erosion process of the muddy interlayers;

[0121] Each time the muddy interlayer within the ellipsoid is removed is an iteration. After each iteration, the mud content of the muddy interlayer in the meandering river grid model is calculated. When the mud content is reduced to a preset content threshold, the iteration is stopped.

[0122] It should be noted that during the migration of meandering rivers, the deposition and erosion of mud interlayers occur continuously. In order to simplify the actual situation, the retention and erosion of mud interlayers are simulated by the ellipsoid removal method. Specifically, the ellipsoid is expressed by the formula:

[0123]

[0124] Among them, a, b, and c are the semi-axis parameters of the ellipsoid, which are specified by the user. After the migration simulation of the meandering river is completed, an ellipsoid is generated within the meandering river model, and the mud interlayer in the ellipsoid is removed to simulate the erosion process of the mud interlayer in the actual situation.

[0125] At each iteration, the coordinates (x, y, z) of the mud layer grid are substituted into the ellipsoid equation for calculation. If the value is < 1, the mud layer is removed and replaced by the river channel inside the ellipsoid. The center position (x 0 ,y 0 ,z 0) to remove muddy interlayers at different positions. Each time an ellipsoid is generated is an iteration. After each iteration, the percentage of muddy interlayers is determined. When the mud content is reduced to a preset value, the iteration is stopped.

[0126] As a specific embodiment, it can be confirmed through modern sedimentation, flume experiments and other means that the degree of retention of mud interlayers in different parts of the river channel is different. Erosion mainly occurs in the outer bend of the channel, and deposition occurs in the inner bend. The deposition here does not only refer to the deposition of shale cover, but also refers to the deposition of river sand and shale layer. If the shale cover is deposited after a flow period and the next flow is erosive, then the possibility of shale cover erosion occurring in the outer bend of the river channel is higher. Therefore, the center position of the ellipsoid in the removal algorithm cannot be completely random. Generally speaking, the erosion holes of the shale cover are more likely to occur in the outer bend of the river channel. A Gaussian probability field is established based on the position and curvature of the river channel, and the ellipsoid is more likely to be generated at a location with high curvature.

[0127] In a preferred embodiment, based on the curvature of the control points, a random simulation algorithm is used to interpolate in the meandering river network model space to generate a three-dimensional probability field;

[0128] The center position of the ellipsoid is determined according to the three-dimensional probability field.

[0129] like Figure 8 As shown, Figure 8 The final meandering river point-bar muddy interlayer channel model obtained after erosion simulation of the muddy interlayer is shown.

[0130] In order to better implement the modeling method of the meandering river point bar mud interlayer in the embodiment of the present invention, based on the modeling method of the meandering river point bar mud interlayer, correspondingly, please refer to Fig. 9 , Fig. 9 The present invention provides a schematic structural diagram of an embodiment of a modeling device for a meandering river point-bar muddy interlayer. The modeling device 900 for a meandering river point-bar muddy interlayer provided by the embodiment of the present invention includes:

[0131] The analysis and calculation module 901 is used to obtain geological parameters of the meandering river, determine a river channel vector center line including a plurality of control points according to the geological parameters, and calculate the curvature of each control point on the vector center line;

[0132] The model building module 902 is used to build an initial grid model, assign values ​​to the initial grid model according to the river channel vector center line and geological parameters, simulate the river channel and mud interlayer of the meandering river, and obtain the meandering river grid model;

[0133] The erosion simulation module 903 is used to erode the muddy interlayer in the meandering river grid model using a preset ellipsoid removal algorithm to obtain a meandering river point-bar muddy interlayer river channel model.

[0134] It should be noted here that the corresponding device 900 provided in the above embodiment can implement the technical solutions described in the above method embodiments. The specific implementation principles of the above modules or units can refer to the corresponding contents in the above method embodiments, which will not be repeated here.

[0135] This embodiment further provides a computer-readable storage medium on which a modeling program for muddy interlayers at point-bars in meandering rivers is stored. When the modeling program for muddy interlayers at point-bars in meandering rivers is executed by a processor, the steps in the above embodiment can be implemented.

[0136] The present invention provides a modeling method and device for mud interlayers at point bars of a meandering river. Firstly, a river channel vector centerline is established based on the geological parameters of the meandering river, and the curvature of each control point on the vector centerline is calculated; secondly, an initial grid model is assigned according to the river channel vector centerline and the geological parameters, and the river channel and mud interlayers of the meandering river are simulated to obtain a meandering river grid model; finally, a preset ellipsoid removal algorithm is used to simulate the erosion process of the mud interlayer to obtain a final meandering river point bar mud interlayer river channel model.

[0137] The method of the present invention depicts the channel and interlayer of a meandering river. By adding mud interlayers on the basis of channel simulation, the geomorphic features of the meandering river can be more realistically displayed. By simulating the migration process of the meandering river, the influence of the mud interlayers on the seepage capacity of the reservoir during the lateral migration of the meandering river point bar can be characterized. According to the law of erosion and retention of lateral accumulation body layers in practice, a corresponding algorithm is designed to simulate the erosion process of the mud interlayers, thereby simulating the meandering river interlayers more objectively and accurately, and providing a reliable theoretical tool for the study of meandering river reservoirs.

[0138] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A modeling method for muddy interlayers at meandering river point bars, characterized in that: include: Acquire geological parameters of the meandering river, determine a river channel vector centerline including a plurality of control points according to the geological parameters, and calculate the curvature of each control point on the vector centerline; Establishing an initial grid model, assigning values ​​to the initial grid model according to the river channel vector centerline and geological parameters, simulating the river channel and mud interlayer of the meandering river, and obtaining a meandering river grid model; The mud interlayers in the meandering river grid model are eroded by using a preset ellipsoid removal algorithm to obtain a meandering river point-bar mud interlayer river channel model; specifically, the method comprises: generating an ellipsoid in the meandering river grid model, removing the mud interlayers within the ellipsoid, and simulating the erosion process of the mud interlayers; each removal of the mud interlayers within the ellipsoid is an iteration, and after each iteration, the mud content of the mud interlayers in the meandering river grid model is calculated, and the iteration is stopped when the mud content is reduced to a preset content threshold; based on the curvature of the control point, a random simulation algorithm is used to interpolate in the meandering river network model space to generate a three-dimensional probability field; the center position of the ellipsoid is determined according to the three-dimensional probability field.

2. The modeling method of meandering river point bar mud interlayer according to claim 1, characterized in that: The initial grid model is assigned values ​​according to the river channel vector center line and geological parameters, and the river channel and mud interlayer of the meandering river are simulated, including: Determine the range of the river channel in the initial grid model according to the center line of the river channel vector, and group all grids within the range of the river channel, each group of grids having the same plane coordinates; The number of grids occupied by mudstone interlayers is determined according to the geological parameters, several grids with the smallest longitudinal coordinate index in each group of grids are modified into mudstone phases, and the mudstone interlayers in the meandering river grid model are simulated based on the mudstone phases.

3. The modeling method of meandering river point bar mud interlayer according to claim 1, characterized in that: Also includes: Simulating the migration process of the meandering river according to the curvature of each control point to obtain multi-stage river channels and mud interlayers; The preset ellipsoid removal algorithm is used to erode the mud interlayer of each period in the meandering river grid model.

4. The modeling method of meandering river point bar mud interlayer according to claim 3 is characterized in that: The migration process of the meandering river is simulated according to the curvature of each control point to obtain multiple river channels and muddy interlayers, including: The migration process of the meandering river includes multiple migration phases, and each migration phase includes multiple migration iterations; Determine a migration coefficient according to the curvature of each control point, and calculate the transformed position of the control point after a single migration under the migration coefficient; Calculating the migration distance of the river channel according to the transformed position and the original position of the control point, and accumulating the migration distance after each river channel migration to obtain a cumulative migration distance; When the cumulative migration distance exceeds a preset distance threshold, a layer of mud interlayer is simulated in the meandering river grid model to obtain a first-stage river channel and mud interlayer; The multi-stage migration process of the meandering river is simulated to obtain multi-stage river channels and mud interlayers.

5. The modeling method of meandering river point bar mud interlayer according to claim 4, characterized in that: Also includes: After a single migration, the distance between any two control points is calculated. When the distance between any two control points is less than the preset river channel width, all control points between the two control points are removed, and the two control points are directly connected to form a new vector centerline; Among them, the multiple control points that are removed are connected to form an abandoned river channel, and the abandoned river channel does not migrate or change.

6. The modeling method of meandering river point bar mud interlayer according to claim 1, characterized in that: The curvature includes a curvature direction and a curvature magnitude; Calculating the curvature of each control point on the vector midline includes: Determine a circumscribed circle according to each control point and two control points adjacent to the control point; The reciprocal of the radius of the circumscribed circle is the curvature of the control point, and the direction from the center of the circumscribed circle to the control point is the curvature direction.

7. A modeling device for muddy interlayers at meandering river point bars, characterized in that: include: An analysis and calculation module, used for obtaining geological parameters of a meandering river, determining a river channel vector center line including a plurality of control points according to the geological parameters, and calculating the curvature of each control point on the vector center line; A model building module is used to build an initial grid model, assign values ​​to the initial grid model according to the river channel vector centerline and geological parameters, simulate the river channel and mud interlayer of the meandering river, and obtain a meandering river grid model; The erosion simulation module is used to use a preset ellipsoid removal algorithm to erode the mud interlayer in the meandering river grid model to obtain a meandering river point-bar mud interlayer river channel model; specifically, it includes: generating an ellipsoid in the meandering river grid model, removing the mud interlayer within the ellipsoid, and simulating the erosion process of the mud interlayer; each time the mud interlayer within the ellipsoid is removed is an iteration, and after each iteration, the mud content of the mud interlayer in the meandering river grid model is calculated, and the iteration is stopped when the mud content is reduced to a preset content threshold; based on the curvature of the control point, a random simulation algorithm is used to interpolate in the meandering river network model space to generate a three-dimensional probability field; the center position of the ellipsoid is determined according to the three-dimensional probability field.

8. A computer-readable storage medium, characterized in that: Used to store computer-readable programs or instructions, which, when executed by a processor, can implement the steps in the modeling method of mud interlayers at point bars in meandering rivers as described in any one of claims 1 to 6.

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