CN104123449A - Subregion local variable-density non-equidistant dual mesh division method for complex mountainous region - Google Patents
Subregion local variable-density non-equidistant dual mesh division method for complex mountainous region Download PDFInfo
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Abstract
The invention relates to a subregion local variable-density non-equidistant dual mesh division method for a complex mountainous region. The method comprises the steps that an overall model framework of the complex mountainous region is established according to the earth surface elevation and the calculated region range, the whole model framework is divided through square coarse meshes in sequence, a complex earth surface nearby region is divided through variable-density densified non-equidistant meshes, a seismic origin nearby region is divided through variable-density densified meshes, and other regions are divided through dual uniformly-multiplied densified meshes. By means of the meshes, the complex earth surface morphology and the distribution conditions of complex media nearby the earth surface can be depicted accurately and subtly, the boundary conditions nearby the complex earth surface can be achieved accurately and stably, the problem of a large error nearby a source point can be solved on the premise of not substantially increasing the calculated amount, the calculating efficiency can be improved substantially on the premise of guaranteeing the calculating accuracy, and spending of too much mesh generation cost, an extra storage space and extra calculated amount are not needed.
Description
Technical field
The present invention relates to a kind of grid cutting algorithm for complex dielectrics model in the technology such as a kind of geophysics field Seismic wave numerical modeling, data processing, especially for the fine grid blocks subdivision method of Complex Mountain model.
Background technology
Complicated mountain region geologic condition brings a lot of thorny difficult problems usually can to the technology such as Complex Mountain regional earthquake ripple numerical simulation, data processing.For the mesh generation technology of Complex Mountain model, it is a basic and critical technology of the character such as the precision that affects the technology such as Seismic wave numerical modeling, data processing under Complex Mountain Conditions, efficiency, stability
At present, the mesh generation to Complex Mountain model, conventionally adopts evenly single ladder grid, not isometric net, curvilinear grid etc.Near the complicated earth surface boundary condition of accurately the portraying of the complicated earth surface form to Complex Mountain model and near surface complex dielectrics distribution situation, numerical evaluation and focus, in the important technical links such as processing of the larger problem of error, above-mentioned evenly single grid is all difficult to the effect obtaining.First, ladder grid is actually surface configuration is carried out to a kind of stepped approximate processing, this approximate processing except surface configuration is portrayed inaccurate, also can cause the problems such as the local boundary diffraction of seismic wave field and angle point scattering, secondly, although evenly single not isometric net has accurately been located elevation position, earth's surface, also be easy to the realization of earth's surface boundary condition, but compare with near encryption grid near surface, it cannot carry out more meticulous portraying to surface configuration and near surface complex dielectrics, finally, although curvilinear grid is to propose for being easy to realize of complicated earth surface place boundary condition, but it cannot carry out more meticulous portraying to surface configuration and near surface complex dielectrics equally, and the generation of curvilinear grid need to spend extra a large amount of grid manufacturing cost conventionally, in addition Seismic wave numerical modeling technology can run into the unsettled problem of numerical value conventionally at this grid, especially very complicated at surface configuration, when local surface elevation change is very violent, the stability that the grid that this grid generation technology is difficult for obtaining generates quality and Numerical Implementation is more difficult to guarantee.
< < Chinese Journal of Geophysics > > 05 phase in 2005 discloses " the double-grid methods of wide corner reflection seimic travel time simulation " such as Zhao Aihua, attempt improving the method that Wide-angle reflection data is explained efficiency and reliability herein simultaneously, the tree method when minimum of using double-grid to calculate wide corner reflection seimic travel time and raypath is walked, double-grid method is only calculated macrolattice node in uniform dielectric inside, at velocity variations point, focal point and geophone station region, calculate little grid node simultaneously, at interfacial boundary point, use the wavelet propagation regions larger than medium internal node, the model calculation shows, the block uniform dielectric model of stratiform for large scale, guaranteeing that, under the condition of precision, the counting yield of the double-grid ray-tracing scheme proposing significantly improves than single grid method herein.
< < Advances in Geophysics > > 04 phase in 2006 discloses " tetrahedron subdivision resistivity three-dimensional finite element simulation under MODEL OVER COMPLEX TOPOGRAPHY " such as Lv Yuzeng, topographic relief is very large to resistivity effects, resistivity anomaly under MODEL OVER COMPLEX TOPOGRAPHY is explained and is received a lot of concerns always, a kind of tetrahedral grid cross-division method has been proposed herein, the grid of subdivision is interlaced, make the grid of subdivision there is diversity, ground electric model in energy simulate complex-terrain situation. simultaneously, from the satisfied equation in point source field, the finite element numerical simulation algorithm under 3 D complex topographic condition of having derived herein, and worked out calculation procedure, example shows, this method is effective, computational accuracy is high.
< < China's coal field geology > > 02 phase in 2006 discloses " Probe into Dissecting Refraction Method Statics Processing under Complicated Surface Conditions " such as Li Xiaobin, by analyzing the problem of using conventional static correction disposal route to expose in complex area, propose to adopt the vertical subdivision method of refraction wave to carry out static correction to seismic data, model near surface refraction wave subdivision model, with the vertical grid of equidistant or unequal-interval, refraction wave is divided into several unit, the refraction wave speed of each unit is approximately a constant, between different units, the variation of speed has reflected the horizontal change of whole near surface formation speed, when practical application, can utilize multiple single shot records orthogonal solving method speed of being correlated with.
China University Of Petroleum Beijing's 2012 Master's thesis disclose Xie Jinping and " under relief surface condition, have become grid forward simulation ".First be the processing for free boundary under relief surface condition, studied vacuum method herein and broad sense virtual image method combines to process the method on this border, at relief surface place, not directly to process normal stress, but to shearing stress Direct Sampling, its efficiency is improved; To adopt the elastic wave staggered-mesh finite difference discrete equations for elastic waves of assigning to again, also introduced and become the efficiency that grid improves relief surface forward simulation, earth's surface local mesh reflnement is processed, earth's surface Local grid step-length is less, relatively overall fine grid blocks difference is obviously raised the efficiency simultaneously, has saved calculating internal memory.Adopt high-order staggered-mesh difference analogue, during near border, adopt step-by-step Degree Reduction to process, at boundary, realize free boundary condition.
While in fact, Complex Mountain model being carried out to mesh generation, need to solve following several key problem: 1. how complicated earth surface form and the distribution of near surface complex dielectrics are accurately described subtly; 2. the technology such as Seismic wave numerical modeling, data processing that how to realize at the boundary condition at complicated earth surface place accurate stable; 3. how to process near the larger problems of technology error focus such as numerical simulation, data processing; 4. how to solve the huge problems of technique computes amount such as numerical simulation, data processing.
Summary of the invention
Object of the present invention is just, for above-mentioned existing evenly single ladder grid, the defect of the grid such as isometric net, curvilinear grid not, to provide local change of a kind of subregion for Complex Mountain region to encrypt equidistant double-grid subdivision method.
The present invention by the following technical programs and step realize:
A, according to earth's surface elevation and zoning scope, build the block mold framework in Complex Mountain region;
B, adopt the above-mentioned model framework of square coarse grid subdivision that uniform mesh spacing is larger;
C, remove the above part in earth's surface of step b grid, but retain the accurate location of earth's surface on mesh lines, and then near earth's surface, form not isometric net;
D, from earth's surface, from the close-by examples to those far off to above-mentioned coarse grid according to (2
n, 2
n-1, 2
n-2..., 2) and the level of encryption of the exponential damping local variable density of carrying out grid is encrypted, and then near the part forming earth's surface becomes refined net;
E, from the focal point of appointment, from the close-by examples to those far off to the grid of above-mentioned steps d according to (2
n, 2
n-1, 2
n-2..., 2) and the cipher mode of the exponential damping local variable density of carrying out grid is encrypted, and then near the part forming source point becomes refined net;
F, the grid beyond steps d and e encryption section is carried out to uniform 2
ndoubly encrypt, grid before the grid of this encryption section and this step forms double-grid, when numerical evaluation, double-grid is the subdivision grid of whole model, the grid of step e is computing grid, and the result of calculation in this step on refined net node is by the result of calculation on the contiguous computing grid in part is carried out to interpolation calculation gained.
Described 2
nn in doubly encrypting is encryption exponent.Encryption exponent n is comprehensively determined by computational accuracy, counting yield and memory space.
Beneficial effect: 1. near change earth's surface is encrypted not isometric net and can meticulously be portrayed exactly complicated earth surface form and near surface complex dielectrics distribution situation; 2. be conducive to numerical simulation, data processing etc. and realize accurately and stably near boundary condition earth's surface; 3. near change refined net focal point is conducive to increase under the prerequisite of calculated amount in little amplitude, solves near the larger problems of technology error source point such as numerical simulation, data processing; 4. the double-grid in whole region can, guaranteeing, under the prerequisite of computational accuracy, to increase substantially the counting yield of numerical simulation, data processing etc., can also increase substantially the depth-sampling rate of some data processing techniques simultaneously; 5. whole grid cutting algorithm is without the grid manufacturing cost of overspending, simultaneously when numerical evaluation also without the extra storage space of overspending with assess the cost.
Accompanying drawing explanation
The local change of accompanying drawing 1 subregion encrypted flow process and the schematic diagram that not equidistant double-grid is set up;
Accompanying drawing 2 adopts mesh generation of the present invention through the revised Marmousi model of relief surface;
Accompanying drawing 3 adopts mesh generation SEG relief surface Foothill model of the present invention.
Embodiment
Below in conjunction with accompanying drawing and embodiment, further illustrate the specific embodiment of the present invention.As shown in Fig. 1 schematic flow sheet, for the local change of subregion in Complex Mountain region, encrypting the not embodiment of equidistant double-grid subdivision technology is following steps:
A, as shown in Fig. 1 step a, according to earth's surface elevation and zoning scope, build the block mold framework in Complex Mountain region;
B, as shown in Fig. 1 step b, adopt the above-mentioned model framework of square coarse grid subdivision that uniform mesh spacing is larger;
C, as shown in Fig. 1 step c, remove the above part in earth's surface of step b grid, but retain the accurate location of earth's surface on mesh lines, and then near earth's surface, form not isometric net;
D, as shown in Fig. 1 steps d, from earth's surface, from the close-by examples to those far off to above-mentioned coarse grid according to (2
n, 2
n-1, 2
n-2..., 2) and the level of encryption of the exponential damping local variable density of carrying out grid is encrypted, and then near the part forming earth's surface becomes refined net;
E, as shown in Fig. 1 step e, from the focal point of appointment, from the close-by examples to those far off to the grid of above-mentioned steps d according to (2
n, 2
n-1, 2
n-2..., 2) and the cipher mode of the exponential damping local variable density of carrying out grid is encrypted, and then near the part forming source point becomes refined net;
F, the grid beyond steps d and e encryption section is carried out to uniform 2
ndoubly encrypt, grid before the grid of this encryption section and this step forms double-grid, when numerical evaluation, double-grid is the subdivision grid of whole model, the grid of step e is computing grid, and the result of calculation in this step on refined net node is by the result of calculation on the contiguous computing grid in part is carried out to interpolation calculation gained.
Described 2
nn in doubly encrypting is encryption exponent.Encryption exponent n is comprehensively determined by computational accuracy, counting yield and memory space.
Embodiment 1
As shown in Figure 2, introduce one classical Marmousi model process is added to earth's surface revised complicated earth surface Marmousi model, this model surface relief is relatively very violent.While adopting mesh generation technology of the present invention to carry out subdivision to it, the mesh spacing of establishing the larger square coarse grid of step b employing is h.When near to earth's surface, grid carries out index encryption, exponential factor maximum is got n=4, the spacing from the nearest grid in earth's surface is h/16, and each index encryption factor (is respectively n=4,3,2) regional extent of corresponding mesh refinement is from earth's surface, to start successively to extend not more than the scope of 1.0h, 1.5h, 2.0h downwards respectively.When near to focus, grid carries out index encryption, same exponential factor maximum is got n=4, the spacing from the nearest grid of focus is h/16, and each index encryption factor (is respectively n=4,3,2) respectively the regional extent of corresponding mesh refinement for take the outward extending donut successively that width that focus is the center of circle is 2h.Finally, when step f forms double-grid, to the multiple of the level of encryption at double of square coarse grid, be 2, the mesh spacing of double-grid is h/2.The subdivision result of analysis chart 2 is known: the form that the mesh generation technology that the present invention proposes can be portrayed complicated earth surface relatively subtly, the complex distributions situation of near surface medium also can be described subtly, and can also carry out variable density encryption near grid focus simultaneously.
Embodiment 2
As shown in Figure 3, model is classical SEG relief surface Foothill model, and some region surface elevation change of this model are relatively violent.When same employing mesh generation technology of the present invention is carried out subdivision to it, the mesh spacing of establishing the larger square coarse grid of step b employing is h.When near to earth's surface, grid carries out index encryption, exponential factor maximum is got n=4, the spacing from the nearest grid in earth's surface is h/16, and each index encryption factor (is respectively n=4,3,2) regional extent of corresponding mesh refinement is from earth's surface, to start successively to extend not more than the scope of 1.0h, 1.5h, 2.0h downwards respectively.When near to focus, grid carries out index encryption, same exponential factor maximum is got n=4, the spacing from the nearest grid of focus is h/16, and each index encryption factor (is respectively n=4,3,2) respectively the regional extent of corresponding mesh refinement for take the outward extending donut successively that width that focus is the center of circle is 2h.Finally, when step f forms double-grid, to the multiple of the level of encryption at double of square coarse grid, be 2, the mesh spacing of double-grid is h/2.The subdivision result of analysis chart 3 is known: the form that the mesh generation technology that the present invention proposes can be portrayed complicated earth surface relatively subtly, the complex distributions situation of near surface medium also can be described subtly, and can also carry out variable density encryption near grid focus simultaneously.
Claims (2)
1. local change of the subregion in Complex Mountain region encrypted not equidistant double-grid subdivision method, it is characterized in that, comprises the following steps:
A, according to earth's surface elevation and zoning scope, build the block mold framework in Complex Mountain region;
B, the model framework that adopts square coarse grid subdivision step a that uniform mesh spacing is larger to build;
C, remove the above part in earth's surface of step b grid, but retain the accurate location of earth's surface on mesh lines, and then near near surface, form not isometric net;
D, from earth's surface, from the close-by examples to those far off to above-mentioned coarse grid according to (2
n, 2
n-1, 2
n-2..., 2) and the level of encryption of the exponential damping local variable density of carrying out grid encrypts, and the part that forms near surface becomes refined net;
E, from the focal point of appointment, from the close-by examples to those far off to the grid of steps d according to (2
n, 2
n-1, 2
n-2..., 2) and exponential damping cipher mode carries out the local variable density of grid and encrypts, and near the part forming source point becomes refined net;
F, the grid beyond steps d and e encryption section is carried out to uniform 2
ndoubly encrypt, grid before the grid of this encryption section and this step forms double-grid, when numerical evaluation, double-grid is the subdivision grid of whole model, the grid of step e is computing grid, and the result of calculation in this step on refined net node is by the result of calculation on the contiguous computing grid in part is carried out to interpolation calculation gained.
2. according to local change of the subregion in Complex Mountain claimed in claim 1 region, encrypt equidistant double-grid subdivision method, it is characterized in that, in step c, e and f 2
nn be encryption exponent.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106772590A (en) * | 2017-03-17 | 2017-05-31 | 中国地质科学院地球物理地球化学勘查研究所 | A kind of free earth's surface finite-difference forward modeling system and method that acutely rises and falls |
| CN107315192A (en) * | 2016-04-26 | 2017-11-03 | 中国石油化工股份有限公司 | The analogy method of elastic wave field numerical value based on two-dimentional isotropic medium |
| CN111948708A (en) * | 2019-10-18 | 2020-11-17 | 中国石油大学(北京) | Seismic wave field forward modeling method for dipping in undulating surface of boundary |
| CN112230277A (en) * | 2020-09-30 | 2021-01-15 | 山东大学 | Tunnel seismic wave propagation numerical simulation method and system based on cylindrical coordinate system |
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| CN102183790A (en) * | 2011-02-12 | 2011-09-14 | 中国石油大学(华东) | Elastic wave forward simulation technology based on space-time dual-variable grid |
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| CN102183790A (en) * | 2011-02-12 | 2011-09-14 | 中国石油大学(华东) | Elastic wave forward simulation technology based on space-time dual-variable grid |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107315192A (en) * | 2016-04-26 | 2017-11-03 | 中国石油化工股份有限公司 | The analogy method of elastic wave field numerical value based on two-dimentional isotropic medium |
| CN106772590A (en) * | 2017-03-17 | 2017-05-31 | 中国地质科学院地球物理地球化学勘查研究所 | A kind of free earth's surface finite-difference forward modeling system and method that acutely rises and falls |
| CN111948708A (en) * | 2019-10-18 | 2020-11-17 | 中国石油大学(北京) | Seismic wave field forward modeling method for dipping in undulating surface of boundary |
| CN112230277A (en) * | 2020-09-30 | 2021-01-15 | 山东大学 | Tunnel seismic wave propagation numerical simulation method and system based on cylindrical coordinate system |
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