CN104123449B - 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 one of technology such as geophysics field Seismic wave numerical modeling, data processing is directed to again
The grid cutting algorithm of miscellaneous dielectric model, in particular for the fine grid blockses subdivision method of Complex Mountain model.
Background technology
Complicated mountain region geological conditions usually can give the technology band such as Complex Mountain regional seismic wave numerical simulation, data processing
Carry out a much thorny difficult problem.For the mesh generation technology of Complex Mountain model, then it is seismic wave under impact Complex Mountain Conditions
One basic and critical technology of the properties such as the precision of the technology such as numerical simulation, data processing, efficiency, stability
At present, the mesh generation to Complex Mountain model, generally using uniformly single ladder network, non-uniformity interval,
Curvilinear grid etc..Accurately the portraying of the complicated earth surface form to Complex Mountain model and near surface complex dielectricss distribution situation,
In the important technical links such as process of the larger problem of error near the complicated earth surface boundary condition of numerical computations and focus, above-mentioned equal
Even single grid is all difficult to the effect having obtained.First, ladder network be actually surface configuration carried out a kind of stepped
Approximate process, this approximate processing except surface configuration is portrayed inaccurate in addition to, also can cause the local boundary of seismic wave field
The problems such as diffraction and angle point scatter；Secondly, although uniformly single non-uniformity interval has been accurately positioned earth's surface elevation location, also easily
In the realization of ground condition, but compared with the encryption grid near near surface, it cannot be to surface configuration and near-earth
Table complex dielectricss carry out more fine portraying；Finally, although curvilinear grid is being easy to of boundary condition at complicated earth surface
Realize and propose, but it equally cannot carry out more fine portraying to surface configuration and near surface complex dielectricss, and bent
The generation of wire grid typically requires and spends extra substantial amounts of mess generation cost, and Seismic wave numerical modeling technology is in this net in addition
Lattice would ordinarily be encountered the unstable problem of numerical value, especially surface configuration is very complicated, local surface elevation change very violent when,
This grid generation technology is difficult the mess generation quality having obtained and the stability of Numerical Implementation is more difficult to ensure.
《Chinese Journal of Geophysics》05 phase in 2005 discloses the " dual network that Wide-angle reflection seismic ripple is simulated when walking such as Zhao Aihua
Lattice method ", attempts improving the method that Wide-angle reflection data explains efficiency and reliability, that is, using double-grid meter herein simultaneously
Calculate Wide-angle reflection seismic ripple when walking and ray path minimum travel-time tree algorithm, doubly strongly degenerate only calculates inside uniform dielectric
Big grid node, in velocity variations point, focal point and geophone station region, calculates small grid node simultaneously；Make in interface boundary point
With the wavelet propagation regions bigger than media interior node, the model calculation shows, the stratiform for large scale is block uniformly
Dielectric model, under conditions of ensureing precision, the computational efficiency of proposed double-grid ray-tracing procedure is than single net
Lattice method significantly improves.
《Advances in Geophysics》04 phase in 2006 discloses " the Tetrahedron subdivision resistance under MODEL OVER COMPLEX TOPOGRAPHY such as Lv Yuzeng
Rate three-dimensional finite element simulation ", hypsography is very big to resistivity effects, the resistivity anomaly solution under MODEL OVER COMPLEX TOPOGRAPHY
Release and be constantly subjected to a lot of concerns, this paper presents a kind of tetrahedral grid cross-division method, the grid of subdivision is interlaced,
The grid of subdivision is made to have a multiformity, can the preferable simulation intricately earth-electricity model in the case of shape. meanwhile, full from point source field
The equation of foot sets out, finite element numerical simulation algorithm under 3 D complex orographic condition of having derived herein, and has worked out calculation procedure,
Example shows, this method is effective, and computational accuracy is high.
《Chinese coal field geology》02 phase in 2006 discloses Li Xiaobin etc. " at complex near surface conditionss dissecting refraction method statics
Reason Research on Methods ", by analyzing the problem being exposed in complex area using conventional static correction processing method, is proposed using refraction
Ripple vertical subdivision method carries out static correction to seismic data, initially sets up near surface refracted wave subdivision model, with equidistantly or
The vertical grid of spacing is divided into several units refracted wave, and the refraction wave velocity of each unit is approximately a constant, and different
Between unit, the change of speed then reflects the cross directional variations of whole near surface formation speed, can utilize multiple single-shots in practical application
Record dependent quadrature solving speed.
China University Of Petroleum Beijing 2012 Master's thesis discloses Xie Jinping " Moving grids forward simulation under the conditions of relief surface ".First
Before this for the process of free boundary under the conditions of relief surface, have studied vacuum method herein and broad sense virtual image method combines to process
The method on this border, is not directly to process direct stress at relief surface, but sampling direct to shearing stress is so as to efficiency has one
Fixed raising；It is that discrete equations for elastic waves is come using elastic wave staggering mesh finite-difference again, also introduce Moving grids to improve
The efficiency of relief surface forward simulation, is processed to earth's surface local mesh reflnement, and earth's surface Local grid step-length is less, simultaneously relatively complete
Office's fine grid blockses difference significantly improves efficiency, saves calculating internal memory.Using high-order staggered-mesh difference analogue, during close border
Processed using step-by-step Degree Reduction, realize free boundary condition in boundary.
In fact, carrying out to Complex Mountain model needing during mesh generation to solve several key problems as follows：1. how right
Complicated earth surface form and the distribution of near surface complex dielectricss carry out accurately subtly describing；2. how to realize seismic wave accurate stable
Boundary condition at complicated earth surface for the technology such as numerical simulation, data processing；3. the skills such as numerical simulation, data processing how are processed
The larger problem of art error near focus；4. how to solve the problems, such as that the technology amount of calculation such as numerical simulation, data processing is huge.
Content of the invention
The purpose of the present invention is that for above-mentioned existing uniformly single ladder network, non-uniformity interval, curvilinear grid
Deng the defect of grid, a kind of local of the subregion for Complex Mountain region is provided to become encryption Unequal distance double-grid subdivision method.
The present invention by the following technical programs and step realize：
A, the block mold framework according to earth's surface elevation and zoning scope structure Complex Mountain region；
B, using the larger above-mentioned model framework of square coarse grid subdivision of uniform mesh spacing；
C, remove the earth's surface above section of step b grid, but retain accurate location on grid lines for the earth's surface, and then on ground
Table is formed about non-uniformity interval；
D, from earth's surface, from the close-by examples to those far off to above-mentioned coarse grid according to (2n,2n-1,2n-2..., 2) encryption of exponential damping
Degree carries out the local variable density encryption of grid, and then forms the local change refined net of adjacent ground surface；
E, from specified focal point, from the close-by examples to those far off to the grid of above-mentioned steps d according to (2n,2n-1,2n-2..., 2) refer to
The cipher mode of number decay carries out the local variable density encryption of grid, and then the local being formed near source point becomes refined net；
F, uniform 2 are carried out to the grid beyond step d and e encryption partnEncryption again, the grid of this encryption part and basis
Grid protocol double-grid before step, in numerical computations, double-grid is the subdivision grid of whole model, step e
Grid is to calculate grid, and the result of calculation on refined net node in this step is by the meter that calculate grid on neighbouring to local
Calculate result and carry out interpolation calculation gained.
Described 2nN in encrypting again is encryption exponent.Encryption exponent n is comprehensive by computational accuracy, computational efficiency and amount of storage
Close and determine.
Beneficial effect：1. adjacent ground surface change encryption non-uniformity interval can finely portray exactly complicated earth surface form and
Near surface complex dielectricss distribution situation；2. numerical simulation, data processing etc. is conducive to accurately and stably to realize the side of adjacent ground surface
Boundary's condition；3. the change refined net near focal point is conducive to, on the premise of not increasing considerably amount of calculation, solving Numerical-Mode
The larger problem of the technology such as plan, data processing error near source point；4. the double-grid of whole region can ensure to calculate
On the premise of precision, increase substantially the computational efficiency of numerical simulation, data processing etc., can also increase substantially simultaneously
The depth-sampling rate of data processing technique；5. whole grid cutting algorithm, without the mess generation cost of overspending, exists simultaneously
Without the extra memory space of overspending and calculating cost during numerical computations.
Brief description
Accompanying drawing 1 subregion local becomes flow process and the schematic diagram that encryption Unequal distance double-grid is set up；
Accompanying drawing 2 adopts the mesh generation of the present invention through relief surface revised Marmousi model；
Accompanying drawing 3 adopts the mesh generation SEG relief surface Foothill model of the present invention.
Specific embodiment
Further illustrate the specific embodiment of the present invention below in conjunction with the accompanying drawings with embodiment.As Fig. 1 schematic flow sheet
Shown, the subregion local for Complex Mountain region becomes the specific embodiment of encryption Unequal distance double-grid partitioning techniques into such as
Lower step：
A, as shown in Fig. 1 step a, build the block mold in Complex Mountain region according to earth's surface elevation and zoning scope
Framework；
B, as shown in Fig. 1 step b, using the above-mentioned model frame of square coarse grid subdivision that uniform mesh spacing is larger
Frame；
C, as shown in Fig. 1 step c, remove the earth's surface above section of step b grid, but retain standard on grid lines for the earth's surface
Really position, and then form non-uniformity interval in adjacent ground surface；
D, as shown in Fig. 1 step d, from earth's surface, from the close-by examples to those far off to above-mentioned coarse grid according to (2n,2n-1,2n-2,…,2)
The level of encryption of exponential damping carries out the local variable density encryption of grid, and then forms the local change refined net of adjacent ground surface；
E, as shown in Fig. 1 step e, from specified focal point, from the close-by examples to those far off to the grid of above-mentioned steps d according to (2n,
2n-1,2n-2..., 2) cipher mode of exponential damping carries out the local variable density encryption of grid, and then form the office near source point
Portion becomes refined net；
F, uniform 2 are carried out to the grid beyond step d and e encryption partnEncryption again, the grid of this encryption part and basis
Grid protocol double-grid before step, in numerical computations, double-grid is the subdivision grid of whole model, step e
Grid is to calculate grid, and the result of calculation on refined net node in this step is by the meter that calculate grid on neighbouring to local
Calculate result and carry out interpolation calculation gained.
Described 2nN in encrypting again is encryption exponent.Encryption exponent n is comprehensive by computational accuracy, computational efficiency and amount of storage
Close and determine.
Embodiment 1
As shown in Fig. 2 introducing one to classical Marmousi model through adding the revised complicated earth surface of earth's surface
Marmousi model, this model surface relief is relatively very violent.When subdivision is carried out to it using the mesh generation technology of the present invention,
If the mesh spacing of the larger square coarse grid that step b adopts is h.Refer to when adjacent ground surface grid is entered with row index encryption
Number factor maximum takes n=4, and that is, the spacing from the nearest grid of earth's surface is h/16, and each index encryption factor (respectively n=4,
3,2) respectively the regional extent of corresponding mesh refinement be start gradually to extend downwardly at earth's surface less than 1.0h, 1.5h,
The scope of 2.0h.When near to focus, grid enters row index encryption, same exponential factor maximum takes n=4, that is, nearest from focus
The spacing of grid is h/16, and the region model of each index encryption factor (respectively n=4,3,2) corresponding mesh refinement of difference
Enclose the donut stretching out successively being width with focus as the center of circle as 2h.Finally, form double-grid in step f
When, the multiple to the level of encryption at double of square coarse grid is 2, and that is, the mesh spacing of double-grid is h/2.Analysis Fig. 2's
Subdivision result understands：Mesh generation technology proposed by the present invention can portray the form of complicated earth surface opposite fine, also can essence
Carefully describe the complex distributions situation of near surface medium, variable density encryption can also be carried out to the grid near focus simultaneously.
Embodiment 2
As shown in figure 3, model is classical SEG relief surface Foothill model, some region earth's surface elevations of this model
Change is relatively violent.Same when subdivision is carried out to it using the mesh generation technology of the present invention, if step b adopt larger just
The mesh spacing of square coarse grid is h.Adjacent ground surface grid is entered row index encryption when exponential factor maximum take n=4, that is, from
The spacing of the nearest grid of earth's surface is h/16, and each index encryption factor (respectively n=4,3,2) corresponding mesh refinement respectively
Regional extent be to start gradually to extend downwardly the scope less than 1.0h, 1.5h, 2.0h at earth's surface.Net near to focus
When lattice enter row index encryption, same exponential factor maximum takes n=4, and that is, the spacing from the nearest grid of focus is h/16, and each refers to
The regional extent of corresponding mesh refinement is that the width with focus as the center of circle is to number encryption factor (respectively n=4,3,2) respectively
The donut stretching out successively of 2h.Finally, when step f forms double-grid, to the one-tenth of square coarse grid extraordinarily
The multiple of close degree is 2, and that is, the mesh spacing of double-grid is h/2.The subdivision result of analysis Fig. 3 understands：Proposed by the present invention
Mesh generation technology can portray the form of complicated earth surface opposite fine, and the complexity that also can subtly describe near surface medium is divided
Cloth situation, can also carry out variable density encryption to the grid near focus simultaneously.
Claims (2)
1. a kind of subregion local in Complex Mountain region becomes encryption Unequal distance double-grid subdivision method it is characterised in that including
Following steps：
A, the block mold framework according to earth's surface elevation and zoning scope structure Complex Mountain region；
B, the model framework being built using larger square coarse grid subdivision step a of uniform mesh spacing；
C, remove the earth's surface above section of step b grid, but retain accurate location on grid lines for the earth's surface, and then near surface
It is formed about non-uniformity interval；
D, from earth's surface, from the close-by examples to those far off to above-mentioned coarse grid according to (2n,2n-1,2n-2..., 2) level of encryption of exponential damping enters
The local variable density encryption of row grid, the local forming near surface becomes refined net；
E, from specified focal point, from the close-by examples to those far off to the grid of step d according to (2n,2n-1,2n-2..., 2) exponential damping adds
Close mode carries out the variable density encryption of grid local, forms the local near focal point and becomes refined net；
F, uniform 2 are carried out to the grid beyond step d and e encryption partnEncryption again, the grid of this encryption part and this step
Grid protocol double-grid before, in numerical computations, double-grid is the subdivision grid of whole model, the grid of step e
For calculating grid, the result of calculation on refined net node in this step is by the calculating knot that calculate grid on neighbouring to local
Fruit carries out interpolation calculation gained.
2. become encryption Unequal distance double-grid subdivision method according to the subregion local in the Complex Mountain region described in claim 1,
It is characterized in that, 2 in step d, e and fnN be encryption exponent.
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| CN107315192B (en) * | 2016-04-26 | 2019-07-05 | 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 |
| CN106772590B (en) * | 2017-03-17 | 2018-10-12 | 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 |
| CN111948708B (en) * | 2019-10-18 | 2021-09-28 | 中国石油大学(北京) | Seismic wave field forward modeling method for dipping in undulating surface of boundary |
| CN112230277B (en) * | 2020-09-30 | 2021-10-29 | 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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