# Method and apparatus of three-dimensional seismic tomography imaging

## A tomography, three-dimensional seismic technology, applied in the field of mine exploration, can solve problems such as inaccurate determination

Active Publication Date: 2018-03-20

ANHUI UNIV OF SCI & TECH

6 Cites 3 Cited by

## AI-Extracted Technical Summary

### Problems solved by technology

[0004] The invention provides a method and device for three-dimensional seismic tomography to overcome the techni...

### Method used

In the present embodiment, a plurality of geophones and a plurality of seismic sources are all set in the high pumping roadway and the bottom pumping roadway of the coal seam, that is, detection points are set on the direction parallel to the coal seam, and also vertical to the setting on the coal seam direction The seismic wave signals received by each geophone can fully reflect the three-dimensional characteristics...

## Abstract

The invention provides a method and apparatus of three-dimensional seismic tomography imaging. The bottom pumping tunnel, the high pumping tunnel and the coal tunnel of a coal seam are each provided with a plurality of detectors and a plurality of focuses. The method of three-dimensional seismic tomography imaging includes the steps: for each focus, acquiring seismic wave signals, emitted from theeach focus, received by all the detectors, after the seismic wave is propagated; and according to the seismic wave signals corresponding to each focus and the path length set, obtaining a propagationvelocity distribution image of P wave in the seismic wave in the space between the bottom pumping tunnel and the high pumping tunnel, wherein the path length set is a set which is formed by the propagated path length of the seismic wave in each network element of the three-dimensional velocity model of the space during the process that the seismic wave transmitted from the predicted focuses arrive at each detector. The image obtained through the method and apparatus of three-dimensional seismic tomography imaging can accurately reflect the construction characteristics of the practical coal seam working surface.

Application Domain

Seismic signal processing

Technology Topic

CoalNetwork element +6

## Image

## Examples

- Experimental program(1)

### Example Embodiment

[0049] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0050] figure 1 Schematic diagram of the layout of the seismic wave transceiver provided by the present invention, figure 2 For the flowchart of Embodiment 1 of the three-dimensional seismic tomography method provided by the present invention, see figure 1 , In the bottom extraction tunnel 1, the high extraction tunnel 2 and the coal tunnel 3 in the coal seam 4, there are multiple geophones 11 and multiple seismic sources 12; in the imaging process, the time when each seismic source is triggered to emit seismic waves is not The number of seismic sources 12 that emit seismic waves at the same time is one; see Figure 1 ~ Figure 2 , The method of this embodiment may include:

[0051] Step S101: For each seismic source, obtain seismic wave signals received by all geophones after the seismic waves emitted by the seismic source have propagated;

[0052] Specifically, the execution subject of this embodiment may be a three-dimensional seismic imaging device, such as a computer. The seismograph obtains the seismic wave signal from the geophone and sends the seismic wave signal to the three-dimensional seismic imaging device. The seismograph may be set in the coal road.

[0053] Such as figure 1 As shown, multiple geophones and multiple seismic sources are set in the bottom-drainage roadway of the coal seam, the high-drainage roadway, and the coal roadway of the coal seam, preferably in the bottom-drainage roadway, the high-drainage roadway and the coal roadway of the coal seam. , The geophone and the seismic source are arranged alternately, that is, a geophone is set between the two seismic sources, and a seismic source is set between the two geophone groups. The number of geophones and seismic sources is not limited in this embodiment.

[0054] Those skilled in the art can understand that, within a certain range, the more the number of geophones and seismic sources, the more accurate and clear the image produced by the three-dimensional seismic tomography method, so that the geological structure of the coal seam face can be analyzed according to the image. The higher the accuracy of the judgment.

[0055] Optionally, in the underground tunnel, the spacing between the geophones is 20m, and the spacing between the seismic sources is 20m; in the high-drawing tunnel, the spacing between the geophones is 20m, and the spacing between the seismic sources is 20m; In coal roadways, the distance between geophones is 20m, and the distance between seismic sources is 20m.

[0056] In the specific imaging process, each seismic source is triggered one by one to emit seismic waves, and each seismic source emits the same seismic waves. For example, if seismic source A is triggered to emit seismic waves, all geophones can receive the seismic wave signal after the seismic wave has propagated, and the three-dimensional seismic imaging device obtains the seismic wave signals received by all the geophones from the seismic source A sent out by the seismic wave; For seismic source A, the seismic wave signals received by each geophone form a common shot gather a. For example, if the number of geophones is 200, there are 200 seismic wave signals in the common shot gather a. Then the B seismic source is triggered to emit seismic waves. At this time, the A seismic source stops sending seismic waves, and all geophones can receive the seismic wave signals after the seismic waves from the B seismic source propagate. The three-dimensional seismic imaging device obtains all the B seismic sources received by the geophones. Send out the seismic wave signal after the seismic wave has propagated; for the B source, the seismic wave signals received by each geophone form a common shot gather b. For example, if the number of geophones is 200, the common shot gather b has 200 Channel seismic signal.

[0057] Those skilled in the art can understand that if the number of seismic sources is 200 and the number of geophones is 200, then one has 200 common shot gathers, and each common shot gather includes 200 seismic waves. signal.

[0058] Step S102: According to all the seismic wave signals and all the path length sets, obtain the propagation velocity distribution image of the P wave in the seismic wave in the space between the underground tunnel and the high extraction tunnel; where each seismic source corresponds to a path length set The path length set is the set of path lengths that the seismic wave propagates in the network elements of the three-dimensional velocity model when the seismic wave from the seismic source is predicted to reach each geophone. The three-dimensional velocity model is the bottom extraction tunnel and the high extraction tunnel. Three-dimensional velocity model of the space between.

[0059] Specifically, before obtaining the propagation velocity distribution image of the P wave in the seismic wave in the space between the bottom-draining roadway and the high-draining roadway according to all the seismic wave signals and all the path length sets, it is also necessary to determine the propagation velocity distribution image of the P-wave The relative positional relationship between the extraction roadway, coal roadway and coal seam and their respective geometric attributes create a three-dimensional velocity model corresponding to the space between the bottom extraction roadway and the high extraction roadway.

[0060] Among them, the relative positional relationship between the bottom drainage roadway, the high drainage roadway, the coal roadway and the coal seam, for example, the bottom drainage roadway is a few meters below the coal seam, which angle of the bottom drainage roadway is in the coal seam, and the high drainage roadway is a few meters above the coal seam. At which angle of the coal seam is the high-drainage roadway and so on.

[0061] The geometric attributes can be, for example, the length, width, and height of the bottom-drainage roadway, the length, width, and height of the high-drainage roadway, the thickness of the coal seam, the length, width, and height of the coal roadway, and so on. Among them, the thickness of the coal seam close to the coal road can be obtained by measurement, and the thickness of the coal seam far away from the coal road can be obtained by prediction.

[0062] The specific creation algorithm of the three-dimensional velocity model can adopt the method in the prior art, which will not be repeated in this embodiment.

[0063] After creating a three-dimensional velocity model of the space between the under-extraction tunnel and the high-extraction tunnel, for each seismic source, according to the three-dimensional velocity model, the spatial location of the seismic source, and the spatial location of each geophone, it is predicted that the seismic waves emitted by the seismic source will reach each location. In the process of the geophone, the path length of the seismic wave propagating in each network element of the three-dimensional velocity model, and each path length constitutes a path length set. In other words, each source corresponds to a path length set.

[0064] Specifically, according to the three-dimensional velocity model, the spatial location of the seismic source, and the spatial location of each geophone, the path length of the seismic wave propagating in each network element of the three-dimensional velocity model during the process of the seismic wave emitted by the seismic source reaching each geophone is predicted, include:

[0065] (1) Perform three-dimensional meshing on the three-dimensional velocity model of the space between the bottom-extraction tunnel and the high-extraction tunnel to obtain the network elements of the three-dimensional velocity model;

[0066] (2) Using the ray tracing algorithm, according to the spatial location of the seismic source and the spatial location of each geophone, predict the path of the seismic wave propagating in each network element of the three-dimensional velocity model when the seismic wave emitted by the seismic source reaches each geophone. length.

[0067] Wherein, the three-dimensional meshing is performed on the three-dimensional velocity model of the space between the under-extraction roadway and the high-extraction roadway, and the method for obtaining each network element of the three-dimensional velocity model is a method in the prior art, which will not be repeated in this embodiment; The network element is a cube grid.

[0068] The following uses the straight ray tracing method as an example to describe the method of obtaining the path length set corresponding to a seismic source.

[0069] When a seismic source emits a seismic wave, all geophones can receive the seismic wave signal after the seismic wave has propagated. Therefore, corresponding to different geophones, the propagation path of the seismic wave is different.

[0070] For source A, geophone a, according to the three-dimensional coordinates of source A in the three-dimensional velocity model and the coordinates of geophone a in the three-dimensional velocity model, obtain the slope K of the ray passing through source A and geophone a, and simulate this ray Is the path of the seismic wave from source A to the geophone a; the coordinates of the intersection point between the ray and each network element of the three-dimensional velocity model are obtained according to the slope K. If the ray has no intersection point with a certain network element, it can be considered that the ray and the The intersection coordinates of the network elements are all (0,0,0). According to the coordinates of the intersection of the ray and the network elements of the three-dimensional velocity model, using Euler’s formula, the propagation path length d of each network element in the process of reaching the geophone of A can be predicted. ij , Where i indicates that a detector is the i-th detector, j=1, 2, ..., J, and J is the total number of network elements. If the a geophone is the fifth geophone and the total number of network elements is 100, the propagation path length d in each network element in the process of the seismic wave emitted by A seismic source reaching the a geophone is measured ij Includes: (d 51 , D 52 ,...,D 100 ); if the fifth network element does not intersect the ray passing through the source A and the geophone a, then d 55 =0, and so on.

[0071] According to the above method, the propagation path length in each network element in the process of the seismic waves emitted by the A seismic source reaching each geophone can be obtained. Therefore, the path length set of a seismic source can be expressed as {d ij |i=1,2,……,I,j=1,2,……,J}, I is the total number of detectors. If I=200 and the number of network elements is 100, the path length of a seismic source includes 2000 path lengths.

[0072] Those skilled in the art can understand that if the number of seismic sources is 100, there are 100 path length sets.

[0073] Correspondingly, according to all seismic wave signals and all path length sets, the propagation velocity distribution image of the P wave in the seismic wave in the space between the underground tunnel and the high tunnel is obtained, including:

[0074] For each seismic source, according to the seismic signal received by each geophone, pick up the travel time of the P wave to each geophone, and each travel time forms a travel time set;

[0075] According to all travel time sets and all path length sets, the propagation velocity distribution image of the seismic wave P wave in the space between the underground tunnel and the high tunnel is obtained.

[0076] Specifically, the P wave in the seismic wave is the wave that first reaches the geophone, and can also be called the first arrival wave.

[0077] The seismic wave emitted by each source corresponds to a travel time set, and the travel time set of a source can be expressed as {T i |i=1,2,……,I}, I is the total number of detectors. Corresponding to the seismic wave emitted by a seismic source, T i It represents the travel time for the P wave in the seismic wave to reach the i-th geophone; if I=200, a travel time set includes 200 travel times.

[0078] Those skilled in the art can understand that if the number of seismic sources is 100, there are 100 travel time sets.

[0079] Among them, according to all travel time sets and all path length sets, the propagation velocity distribution image of the seismic wave P wave in the space between the underground tunnel and the high tunnel is obtained, including:

[0080] (1) For each seismic source, according to the travel time set corresponding to the seismic wave emitted by the seismic source and the path length set corresponding to the seismic source, the slowness corresponding to the propagation speed of the P wave of the seismic wave in each network element is obtained. Degrees make up the slowness set;

[0081] Specifically, for each seismic source, according to the travel time set corresponding to the seismic wave emitted by the seismic source and the path length set corresponding to the seismic source, an algorithm based on the joint iterative reconstruction technique is used to obtain the corresponding propagation velocity of the seismic wave in each network element. Slowness

[0082] The initial value of the slowness set corresponding to the next triggered seismic source is the slowness set corresponding to the currently triggered seismic source obtained by using an algorithm based on the joint iterative reconstruction technique.

[0083] The specific algorithm is as follows:

[0084] For the first triggered seismic source A, write its corresponding path length set in the form of the following matrix D, which is a matrix with I rows and J columns:

[0085]

[0086] Among them, each row in the D matrix represents the path length of the propagation path of each network element of the three-dimensional velocity model when the seismic wave emitted by the predicted source A reaches one of the geophones; for example, the first line is the seismic wave emitted by the source A The length of the propagation path of each network element in the three-dimensional velocity model when reaching the first geophone.

[0087] The travel time set of the seismic wave emitted by the first triggered source A is written in the form of the following matrix T, which is a matrix with row I and column I

[0088]

[0089] Among them, each row in the T matrix represents the travel time of the predicted P wave in the seismic wave from source A to reach one of the geophones; T i Represents the travel time of the P wave in the seismic wave from the predicted source A to reach the i-th geophone.

[0090] In seismic tomography, the travel time of P wave can be considered mathematically as the linear integral of slowness along the direction of seismic wave propagation. Reconstruction of discrete images during inversion calculation can get:

[0091]

[0092] Among them, L i Is the path length of the i-th ray (that is, the total length of the propagation path of the seismic wave from the simulated seismic source to the i-th geophone); V(x,y,z) is the seismic wave propagation velocity in three-dimensional space; S( x,y,z) is the corresponding slowness; d ij Is the length of the ray in the i-th ray that falls in the j-th grid (that is, the length of the path propagated in the j-th network element of the three-dimensional velocity model when the seismic wave from the seismic source reaches the i-th geophone ); I is the total number of rays (that is, the total number of detectors); J is the total number of network elements.

[0093] Therefore, the following matrix equation can be obtained:

[0094]

[0095] Among them, S j Is the slowness of seismic wave propagation in j network elements.

[0096] Solve the above matrix equation to get The slowness of seismic wave propagation in each network element can be obtained, and the speed of seismic wave propagation in each network element can be obtained accordingly.

[0097] The above matrix equations are often solved by joint iterative reconstruction technology, and the formula is:

[0098]

[0099] Among them, k=0, 1..., is the number of iterations.

[0100] That is, first matrix S A Assign an initial value S 0 ,Substitute the above matrix equation to calculate D×S 0 Get matrix T 0 , At this time (d i , S 0 )=T i 0 , And then get S according to the second line in formula one 1 , Repeat the calculation process until ||S k+1 -S k || ∞ A =S k+1 , Ε is the preset error.

[0101] For the triggered source B, according to the path length set corresponding to source B and the travel time set corresponding to the seismic wave emitted by source B, according to the same method described above, the matrix S corresponding to the slowness set of the seismic wave propagation in each network element is calculated B , At this time, calculate the matrix S B When, assign S B The initial value of is the matrix S calculated based on the path length set corresponding to source A and the travel time set corresponding to the seismic wave emitted by source A A.

[0102] Repeat the above process until the path length set corresponding to the last triggered source C and the travel time set corresponding to the seismic wave emitted by source C are calculated to obtain the matrix S corresponding to the slowness set of the seismic wave propagating in each network element C. Matrix S C Each slowness value in is the final slowness of the seismic wave propagating in each network element, and accordingly, the speed of the seismic wave propagating in each network element is finally obtained.

[0103] (2) According to the slowness set corresponding to the last triggered seismic source, the propagation velocity distribution image of the P wave in the seismic wave in the space between the underground tunnel and the high tunnel is obtained.

[0104] According to the slowness set corresponding to the last triggered seismic source, the velocity of the seismic wave propagating in each network element is obtained; then according to the velocity of the seismic wave propagating in each network element, it is obtained that the P wave in the seismic wave is in the bottom tunnel and the high tunnel. The propagation velocity distribution image in the space between.

[0105] image 3 The actual geological structure diagram provided by the present invention, Figure 4 To adopt the method of the present invention image 3 A slice map of the geological structure in the 3D seismic tomography.

[0106] See image 3 , image 3 The black part AA is the coal seam working face, which can be seen to have an undulating structure or fault.

[0107] See Figure 4 , Figure 4 The medium black area BB has two parts, and there is a fault between the two black areas, indicating that the image formed by the three-dimensional seismic tomography method of the present invention is relatively accurate, and the image formed can accurately reflect the structural characteristics of the actual coal seam face.

[0108] In this embodiment, multiple detectors and multiple seismic sources are set in both the high-drainage roadway and the bottom-drainage roadway of the coal seam, that is, detection points are set in the direction parallel to the coal seam, and detection points are also set in the direction perpendicular to the coal seam. , The seismic wave signal received by each geophone can fully reflect the three-dimensional characteristics of the coal seam. Therefore, according to all the seismic wave signals received by each geophone, the P wave in the obtained seismic wave is in the space between the underground tunnel and the high tunnel The image of the propagation velocity distribution in is relatively accurate and clear, and the resulting image can accurately reflect the structural characteristics of the actual coal face.

[0109] In the three-dimensional seismic tomography method provided in this embodiment, multiple geophones and multiple seismic sources are set in the bottom drainage roadway, high drainage roadway of the coal seam, and the coal roadway of the coal seam; during the imaging process, each seismic source is The time of triggering the seismic wave is different and there is only one seismic source at the same time; the three-dimensional seismic tomography method includes: for each, acquiring the seismic wave signal received by all geophones from the seismic wave sent by the seismic source after propagation; All seismic wave signals and all path length sets are used to obtain the propagation velocity distribution image of the P wave in the seismic wave in the space between the underground tunnel and the high tunnel; where each source corresponds to a path length set, and the path length set It is a collection of the path lengths of the seismic waves propagating in the network elements of the three-dimensional velocity model when the seismic waves from the seismic source are predicted to reach the geophones. The three-dimensional velocity model is the space between the bottom and high-extraction tunnels. Three-dimensional velocity model. With the three-dimensional seismic tomography method provided in this embodiment, the obtained seismic wave propagation velocity distribution image is relatively accurate and clear, and the resulting image can accurately reflect the structural features of the actual coal face.

[0110] Figure 5 It is a schematic structural diagram of Embodiment 1 of the three-dimensional seismic tomography apparatus provided by the present invention, such as Figure 5 As shown, the device of this embodiment may include: an acquisition module 51 and an imaging module 52; wherein, corresponding to each seismic source, the acquisition module 51 is used to acquire seismic wave signals received by all geophones from the seismic wave transmitted by the seismic source; The imaging module 52 is used to obtain the propagation velocity distribution image of the P wave in the seismic wave in the space between the underground tunnel and the high tunnel according to all the seismic wave signals and all the path length sets; wherein, each seismic source corresponds to one Path length set. The path length set is a collection of path lengths that the seismic waves propagate in the network elements of the three-dimensional velocity model when the seismic waves from the predicted seismic source reach each geophone. The three-dimensional velocity model is the bottom-exhausted tunnel and the high-exhausted tunnel. Three-dimensional velocity model of the space between. Among them, multiple geophones and multiple seismic sources are set in the bottom drainage roadway of the coal seam, the high drainage roadway and the coal roadway of the coal seam. During the imaging process, the seismic waves are triggered at different times and the seismic waves are emitted at the same time. The number of seismic sources is one.

[0111] Among them, the imaging module 52 is specifically used to: for each seismic source, according to the seismic wave signal received by each geophone, pick up the travel time of the P wave to each geophone, and each travel time forms a travel time set; according to the sum of all travel time sets All the path lengths are set, and the image of the propagation velocity distribution of the P wave in the seismic wave in the space is obtained.

[0112] The imaging module 52 is specifically used for: For each seismic source, according to the travel time set corresponding to the seismic wave emitted by the seismic source and the path length set corresponding to the seismic source, obtain the slowness corresponding to the propagation speed of the P wave of the seismic wave in each network element, each of which is slow The slowness set is composed of degrees; according to the slowness set corresponding to the last triggered seismic source, the propagation velocity distribution image of the P wave of the seismic wave in space is obtained.

[0113] The device in this embodiment can be used to implement the technical solutions of the foregoing method embodiments, and its implementation principles and technical effects are similar, and will not be repeated here.

[0114] Image 6 It is a schematic structural diagram of Embodiment 2 of the three-dimensional seismic tomography apparatus provided by the present invention, such as Image 6 As shown, the device of this embodiment is Figure 5 On the basis of the shown device structure, it may further include: a creation module 53 and a path length acquisition module 54;

[0115] The creation module 53 is used to create a three-dimensional velocity model based on the relative positional relationship between the bottom drainage roadway, the high drainage roadway, the coal roadway and the coal seam and their respective geometric attributes;

[0116] The path length acquisition module 54 is used for each seismic source, according to the three-dimensional velocity model, the spatial location of the seismic source, and the spatial location of each geophone, to predict that the seismic waves from the seismic source will reach each geophone, and the seismic waves will be in each network of the three-dimensional velocity model. The path length propagated in the element, each path length composes the path length set.

[0117] The path length acquisition module 54 is specifically used to: perform three-dimensional meshing of the three-dimensional velocity model to obtain the network elements of the three-dimensional velocity model; use the ray tracing algorithm to predict the origin of the seismic source according to the spatial location of the seismic source and the spatial location of each geophone The path length of the seismic wave propagating in each network element of the three-dimensional velocity model when the seismic wave reaches each geophone.

[0118] The device in this embodiment can be used to implement the technical solutions of the foregoing method embodiments, and its implementation principles and technical effects are similar, and will not be repeated here.

[0119] A person of ordinary skill in the art can understand that all or part of the steps in the foregoing method embodiments can be implemented by a program instructing relevant hardware. The aforementioned program can be stored in a computer readable storage medium. When the program is executed, it executes the steps including the foregoing method embodiments; and the foregoing storage medium includes: ROM, RAM, magnetic disk, or optical disk and other media that can store program codes.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand: It is still possible to modify the technical solutions described in the foregoing embodiments, or equivalently replace some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. range.

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