KR101410511B1 - land seismic imaging apparatus - Google Patents

Abstract

A ground-based elastic-wave imaging technique of a Laplace domain is disclosed. A large number of water depths are distributed in a lattice pattern at 150-250 m intervals in the measurement area. Each of the water drills is buried in excavated excavated underground and filled with cement.

Description

Background of the Invention Field of the Invention [0001] The present invention relates to a land seismic imaging apparatus,

The present invention relates to terrestrial acoustic wave imaging techniques, and more particularly to imaging techniques for modeling underground structures through waveform inversion in the Laplace domain.

The imaging technique of the underground structure by waveform inversion is known. For example, an invention was invented by the present inventor and filed with the Korean Intellectual Property Office on Jun. 17, 2009, and registered as a patent No. 1,092,668 on Dec. 5, 2011. This invention is also filed in U. S. Patent Application No. 12 / 817,799.

According to this, the modeling parameters of the underground structure are obtained by using the measurement data measured by the receiver through the reflected wave after the low frequency signal transmitted from the transmission source passes through the underground structure. The coefficients of the wave equation consist of modeling parameters such as the density of the underground medium in which this wave propagates. The modeling parameters of the wave equation are calculated by waveform inversion. Waveform inversion is computed by iteratively updating the modeling parameters in a direction that minimizes the residual function of the difference between the modeling data and the measurement data, which is the solution to the wave equation.

Conventional land seismic data acquisition techniques have generated sources in the ground and detected waves in a grid placed on the ground. In this case, the acoustic wave signal is contaminated by source-receiver coupling, and also includes a surface wave such as a Rayleigh wave. This makes precise waveform inversion difficult.

This paper proposes a data acquisition method for the ground seismic survey which can exclude adverse effects due to source - receiver coupling.

According to an aspect of the present invention, a ground-based elastic-wave imaging apparatus includes a transmission source buried in the ground, a grid disposed in a measurement area, buried in excavation holes drilled underground, And modeling parameters of the wave equation in the Laplace domain are obtained. The modeling parameters in the direction of minimizing the residual function regarding the difference between the modeling data, which is the solution of the wave equation applying the current modeling parameter, and the measurement data measured at the receiver, A waveform inversion section for obtaining a modeling parameter by repeating the updating of the modeling parameter and an underground structure imaging section for imaging the underground structure from the calculated modeling parameter.

According to another aspect, a drill hole in which the drill holes are buried can be drilled to a depth of 10-20m underground. In addition, the excavation holes in which these drills are buried can be drilled to a depth of 0.2-1.2 m from the surface of the underground rock.

According to another aspect, the excavation holes in which the excavators are buried may be arranged on a lattice having a distance of 150 to 250 m from each other.

According to one aspect, the method for acquiring the ground seismic exploration data may include a step of burying a plurality of water depth distributors in a lattice form at intervals of 150-250 m in a measurement target area, and buried in excavation holes drilled underground .

According to yet another aspect, a method for acquiring ground-based seismic exploration data comprises the steps of excavating a plurality of excavation holes in a lattice to a depth of 10-20m underground, installing a precipitator in the excavation holes, And cementing up to depth.

Furthermore, the method for acquiring the ground seismic exploration data may further include the step of buried the transmission source in the ground.

According to another aspect, drill holes can be drilled to a depth of 0.2-1.2 m from the surface of the underground rock.

According to another aspect, the source can be buried in a drilling hole 10-20 meters deep underground.

According to another aspect, the excavation hole in which the transmission source is buried is excavated to a depth of 0.2-1.2 m from the surface of the underground rock, but can be excavated to a shallower depth than the excavator in which the excavator is installed.

As the water depths are buried in the excavation hole, the adverse effect due to the transmission source-water depth coupling can be reduced and the surface wave can be ignored.

Furthermore, when the Laplace domain waveform inversion is applied, the number of water jets can be reduced because the interval between the water jets is much wider than that of the prior art. Therefore, although it takes a lot of cost to excavate individual receivers, by reducing the number of receivers, the overall data acquisition cost does not increase or can be reduced significantly.

FIG. 1 is a view for explaining a method of acquiring ground-based seismic exploration data according to an embodiment.
2 is a block diagram illustrating a schematic configuration of an underground structure imaging apparatus according to an embodiment.

The foregoing and further aspects of the present invention will become more apparent through the following embodiments. In the following, these aspects will be described in detail with reference to the embodiments described with reference to the accompanying drawings.

FIG. 1 is a view for explaining a method of acquiring ground-based seismic exploration data according to an embodiment. As shown in the figure, according to one aspect, in the method for acquiring the ground seismic exploration data, a plurality of water depths are distributed in a lattice form in a measurement target area, and buried in excavation holes drilled underground. When viewed on a plan view, excavation holes are excavated in a two-dimensional manner on a lattice of a shape such as a rectangle or rhombus. Where the drill holes can be excavated in a lattice with a spacing (D _G ) of 150-250 m. Typically, in ground-based seismic surveys, surveyors are placed at 10-50m intervals. In the waveform inversion of the Laplace region, the output image is not greatly different even if the interval between the water depths is widened. Also, in the Laplacian region, a sufficiently long measurement time greatly affects the accuracy of the output image. For example, the measurement time is preferably 10 seconds or more. Since the water depths are embedded in the excavation hole, not the surface, adverse effects due to the coupling of the source and receiver can be reduced and surface waves can be ignored.

According to another aspect, the method for acquiring the ground seismic exploration data includes the steps of excavating a plurality of excavation holes in a lattice form at a depth of 10-20 m (D1) under the ground, installing a water depth in the excavation holes, Cementing it to at least some depth. Preferably, the drill holes can be further excavated from the surface of the underground rock to a depth of 0.2-1.2 meters (D2).

As shown, the drill holes are excavated underground and are excavated to a depth of 10-20m underground to fully exclude adverse effects due to source-receiver coupling. The water depths 30 are buried in the excavated excavated to the underground rock, so that the wave can be measured more precisely. In geophysical surveys, the geophone 30 may be a magnetic displacement sensor, an acceleration sensor, or the like. In recent years, radio receivers 30 are also used in wireless types in which cables are not connected.

When a water column is installed in a drilling hole, its upper part is filled with cement. The drill hole may be completely filled with cement up to the surface of the earth, and only a part of the lower part of the drill hole may be filled in consideration of cost.

According to another aspect, the method for acquiring the ground seismic exploration data may further include a step of burying the transmission source in the ground. The excavation hole for the burial of the transmission source is excavated together with the excavation hole for the burial of the excavators. According to one aspect, the transmission source may be buried in a drilling hole 10-20 meters deep underground. The sender may be buried after the burrows are buried, or buried before that. According to another aspect, the transmission source can be buried on the rock by excavating the excavation ball to the underground rock. The excavation hole in which the transmission source is buried is excavated to the depth of 0.2-1.2 m from the surface of the underground rock, but can be excavated to a shallower depth than the excavator in which the excavator is installed.

Transmitting sources include dynamite, explosives such as Tovex, also called seismogel, or accelerating drops of weight using a thumper truck, Vibroseis, and the like may be used. When a source is buried in a drilling rig, the use of explosives such as Tovex should be considered in an easy way or the impact of the environment.

2 is a block diagram showing a schematic configuration of a ground-based elastic-wave imaging apparatus according to an embodiment. The ground-based elastic-wave imaging apparatus according to an embodiment includes a transmission source 10, a plurality of water depths 30, a waveform inversion unit 300, and a imaging unit 500. The transmission source 10 can be buried underground. The plurality of water receivers 30 are distributed in a lattice pattern in the measurement target area and are embedded in the measurement target area. Each water column is buried in excavated excavated underground. Since these have been described with reference to FIG. 1, detailed description is omitted.

The waveform inversion section 300 obtains a modeling parameter of the wave equation in the Laplace domain. The waveform inversion unit 300 obtains the modeling parameter by repeating updating of the modeling parameter in a direction that minimizes the residual function related to the difference between the modeling data, which is the solution of the wave equation to which the current modeling parameter is applied, and the measurement data measured at the receiver. The imaging unit 500 images the underground structure from the modeling parameters thus calculated.

Each block shown in the drawing of FIG. 2 may be implemented in computer program code. These blocks may represent functions implemented in each program code, and the meaning of these blocks and how they are implemented will be apparent to those skilled in the art. Similarly, it should be understood by those skilled in the art that each block is functionally distinct, but may be slightly overlapping or mixed in program code.

A method for obtaining a medium parameter that minimizes the residual by waveform inversion from the wave equation is disclosed in, for example, the prior application filed by the present applicant. The modeling parameters are updated to minimize the residual function of the difference between the modeling data, which is the solution of the wave equation to which the current modeling parameter is applied, and the measurement data measured at the receiver. When the magnitude of the residual function converges below a certain level, then the modeling parameter value is output to the structure data of the medium.

The underground structure imaging unit 500 images the underground structure from the modeling parameters calculated by the waveform inversion unit 300. According to a further aspect, the underground structure imaging unit 500 can color-image and output the underground structure from the calculated modeling parameters. It is possible to map the velocity value or density value value by position in color and output it as a color image.

According to another aspect, the waveform inversion unit 300 includes a modeling data calculation unit 330 that obtains modeling data of the Laplace domain by solving the wave equation in the Laplace domain with given source information, A residual function calculation unit 370 for obtaining a residual function related to the residual of the model equation calculated by the residual function calculator 370 and a residual function calculating unit 370 for calculating a residual function of the current wave equation, And a modeling parameter calculator 310 for outputting the current modeling parameter as a final output value if it is supplied to the modeling data calculator 330.

The modeling parameter calculation unit 310 has a parameter value of the initial model of the underground structure. The initial value may be arbitrarily set. The modeling data calculation unit 330 calculates modeling data that can be detected at each reception point when a wave caused by an equivalent transmission source propagates to the underground structure specified by the modeling parameters. The modeling data can be obtained by solving the wave equation specified by the modeling parameters using a numerical method such as finite element method or finite difference method.

The residual function calculator 370 calculates an error between the measurement data stored in the memory 390 and the modeling data calculated from an arbitrary initial model. The residual function is a function for calculating this error. For example, the residual function can be selected in various ways, such as L2 norm, difference of log value of two values, power of p, and integral value. If the error is larger than the predetermined value, the modeling parameter calculation unit 310 updates the modeling parameter in a direction in which the error decreases. This is done by calculating the gradient of the residual function for each model parameter to yield a model parameter that minimizes the residual function. If the error is larger than the predetermined value, the updating of the modeling parameter is repeated. If the error is smaller than the predetermined value, the modeling parameter at that time is determined as the final modeling parameter for the underground structure and output to the outside. The modeling parameters correspond to the coefficients of the wave equation, for example, velocity, density, etc. in the underground medium.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The appended claims are intended to cover such modifications.

10: transmitting source 20: ground surface
30: water column 40: bedrock
50: Cement
300: waveform inversion unit 310: modeling parameter calculation unit
330: modeling data calculation unit 350: measurement data processing unit
370: residual function calculation unit 390: memory
500: Underground structure visualizer

Claims (11)

A transmission source embedded in the ground;
They are distributed in a lattice form with 150-250m intervals between each other in the measurement area and excavated to a depth deeper than the depth at which the source is embedded and which is 10-20m deep underground and 0.2-1.2m deep from the surface of underground rock. A plurality of water depth sensors buried in the balls and sensing a wave generated in the transmission source and passing through the ground;
The modeling parameters of the wave equation in the Laplace domain are obtained, and the updating of the modeling parameters is repeated in the direction of minimizing the residual function regarding the difference between the modeling data, which is the solution of the wave equation using the current modeling parameter, A waveform inversion unit for obtaining a modeling parameter;
A visualization unit for imaging the underground structure from the calculated modeling parameters;
And a ground surface.
The apparatus of claim 1, wherein the waveform inversion unit comprises:
A modeling data calculation unit for obtaining modeling data of the Laplace domain by solving the wave equation in the Laplace domain with given source information;
A residual function calculator for obtaining a residual function of the residual of the data obtained by converting the measurement data into the Laplace domain and the modeling data calculated by the modeling data calculator;
If the value of the residual function calculated by the residual function calculator is equal to or greater than the reference value, the modeling parameter of the current wave equation is updated to minimize the residual function and supplied to the modeling data calculator. And a modeling parameter calculation unit.
delete delete delete Excavation of a large number of excavation holes at a distance of 150-250 m to the measurement area at a depth of 10-20m below the ground and 0.2-1.2m below the surface of the underground rock, ;
Installing a water jug in the excavation holes;
Filling each of said excavation holes with cement to at least some depth;
Wherein the method comprises the steps of:
delete 7. The method of claim 6, wherein the obtaining method comprises:
Burying a transmission source in a basement;
Further comprising the steps of:
delete delete The method according to claim 8, wherein the excavation hole in which the transmission source is embedded is excavated to a depth of 0.2 to 1.2 m from the surface of the underground rock, and excavated at a shallower depth than the excavation hole in which the excavator is installed.

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