Pre-stack time migration method, device and equipment for down-going wave seismic data and medium

Abstract

The present disclosure provides a pre-stack time migration method and device for downgoing wave seismic data, and belongs to the technical field of seismic exploration. The method comprises: obtaining seismic data collected by an acquisition device at a plurality of geophones; obtaining a plurality of channels of downgoing wave seismic data based on the seismic data; calculating a travel time of each channel of the downgoing wave seismic data with the sea level as a reference surface; and performing migration on the plurality of channels of downgoing wave seismic data according to the calculated travel time of each channel of the downgoing wave seismic data. In the embodiment of the present disclosure, the travel time of the downgoing wave seismic data is calculated with the sea level as a reference surface, which can make the calculated travel time of the downgoing wave seismic data more accurate and improve the migration accuracy of the downgoing wave seismic data.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of seismic exploration, and particularly relates to a downgoing wave seismic data pre-stack time migration method, device, equipment and medium. BACKGROUND

[0002] In the technical field of seismic exploration, pre-stack time migration is an important method for seismic wave imaging. The principle of the method is to form a common imaging point seismic data gather by migrating multiple seismic data acquired at the sea bottom to the real imaging point position, and then stacking, so as to improve the accuracy of imaging of the underground medium. In the process of migrating the seismic data, the travel time of downgoing wave seismic data is used. The propagation path of the downgoing wave seismic data includes two segments of the shot point to the imaging point and the imaging point to the receiver point, wherein the imaging point to the receiver point includes the imaging point to the sea level and the sea level to the receiver point, and the travel time of the downgoing wave seismic data is the time length used by the downgoing wave seismic data to propagate from the shot point to the receiver point according to the propagation path.

[0003] In the related art, the travel time of the downgoing wave seismic data is calculated by using the following formula:

[0004] (wherein, t S is the travel time of the shot point to the imaging point; t G is the travel time of the imaging point to the receiver point.)

[0005] In the formula, t is the one-way vertical time at the imaging point corresponding to the sea level as the reference surface, x s is the horizontal distance from the shot point to the imaging point, x g is the horizontal distance from the receiver point to the imaging point, d is the depth of the sea bottom where the receiver point is located, v s is the root mean square velocity at the imaging point corresponding to the sea level as the reference surface, v w is the velocity of seawater, and v r is the root mean square velocity at the imaging point corresponding to the sea bottom surface as the reference surface.

[0006] In the process of implementing the present disclosure, the inventors found that the prior art at least has the following problems:

[0007] In the formula for calculating the travel time of the imaging point to the receiver point, v w is the seawater velocity with the sea level as the reference surface, v r is the root mean square velocity with the sea bottom surface as the reference surface, t is the one-way vertical time at the imaging point with the sea level as the reference surface, v w , v r , and t use different reference surfaces. When the right triangle formula is solved, (t+d / v w ) and (xs v r ) are different, so that the calculated travel time of the imaging point to the detection point is inaccurate, and the calculated travel time of the downgoing wave seismic data is inaccurate, which affects the precision of migration of the downgoing wave seismic data. SUMMARY

[0008] The embodiments of the present disclosure provide a pre-stack time migration method and device of downgoing wave seismic data, which can improve the accuracy of calculating the travel time of the downgoing wave seismic data, and further improve the precision of migration of the downgoing wave seismic data. The technical solutions are as follows:

[0009] In a first aspect, a pre-stack time migration method of downgoing wave seismic data is provided, the method comprising:

[0010] obtaining seismic data collected by a collection device at a plurality of detection points, the plurality of detection points being located on a sea bottom surface, each detection point being provided with a collection device, the collection device being used to collect a seismic wave reflected by a sea bottom formation and emitted by a launch device at a shot point, to obtain the seismic data, the shot point being located on a sea level; based on the seismic data, obtaining a plurality of channels of downgoing wave seismic data; calculating a travel time of each channel of the downgoing wave seismic data from the shot point to an imaging point according to a root mean square velocity of the imaging point with the sea level as a reference surface; calculating a travel time of each channel of the downgoing wave seismic data from the imaging point to an intersection of a horizontal line passing through a corresponding detection point and a reflection line passing through the imaging point according to the root mean square velocity of the imaging point with the sea level as the reference surface; calculating a travel time of each channel of the downgoing wave seismic data from the intersection to a mirror point of the corresponding detection point according to a seawater velocity with the sea level as the reference surface; taking a sum of the calculated travel time of each channel of the downgoing wave seismic data from the shot point to the imaging point, the travel time of the imaging point to the intersection, and the travel time of the intersection to the corresponding detection point as a travel time of each channel of the downgoing wave seismic data;

[0011] migrating the plurality of channels of the downgoing wave seismic data according to the calculated travel time of each channel of the downgoing wave seismic data.

[0012] Optionally, the calculating of the travel time of each channel of the downgoing wave seismic data from the shot point to the imaging point according to the root mean square velocity of the imaging point with the sea level as the reference surface comprises: calculating the travel time of each channel of the downgoing wave seismic data from the shot point to the imaging point according to the following formula:

[0013]

[0014] wherein t1 is the travel time of each channel of the downgoing wave seismic data from the shot point to the imaging point, x sis a horizontal distance from the shot point to the imaging point, v is a corresponding sea level reference plane based root mean square velocity at the imaging point;

[0015] The calculating the travel time of each trace of the down-going wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point according to the sea level reference plane based root mean square velocity at the imaging point comprises: calculating the travel time of each trace of the down-going wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point according to the following formula:

[0016]

[0017] wherein t2 is the travel time of each trace of the down-going wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point, t is a corresponding one-way vertical time at the imaging point in the sea level reference plane, d is a depth of the seabed where the receiver point is located, v is a corresponding sea level reference plane based root mean square velocity at the imaging point, x g is a horizontal distance from the receiver point to the imaging point, OR is a horizontal distance from the intersection of the horizontal line passing through the receiver point and the reflection line passing through the imaging point to the receiver point;

[0018] The calculating the travel time of each trace of the down-going wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point according to the sea level reference plane based root mean square velocity at the imaging point comprises: calculating the travel time of each trace of the down-going wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point according to the following formula:

[0019]

[0020] wherein t3 is the travel time of each trace of the down-going wave seismic data from the intersection to the mirror point of the corresponding receiver point, OR is a horizontal distance from the intersection of the horizontal line passing through the receiver point and the reflection line passing through the imaging point to the receiver point, d is a depth of the seabed where the receiver point is located, v w is a sea water velocity.

[0021] Optionally, the method further comprises: spacing a plurality of velocity values within a set velocity range; and calculating the travel time corresponding to each of the velocity values by using the following formula:

[0022]

[0023] wherein x s is a horizontal distance from the shot point to the imaging point, x gis a horizontal distance from the detection point to the imaging point, d is a depth of the seabed where the detection point is located, v is one of the plurality of velocity values, and t is a corresponding one-way vertical time at the imaging point with respect to a sea level reference surface; determining an amplitude value of multi-channel downgoing wave seismic data participating in imaging of the imaging point according to the calculated travel time corresponding to each of the velocity values; and stacking the determined amplitude value of the multi-channel downgoing wave seismic data corresponding to each of the velocity values to obtain a plurality of stacked amplitude values; and taking a velocity value corresponding to a maximum stacked amplitude value in the plurality of stacked amplitude values as a root mean square velocity of the imaging point with respect to the sea level reference surface.

[0024] Optionally, the migration of each of the downgoing wave seismic data according to the calculated travel time of each of the downgoing wave seismic data includes: determining an amplitude value of downgoing wave seismic data corresponding to the travel time of each of the downgoing wave seismic data according to a corresponding relationship and the travel time of each of the downgoing wave seismic data, the corresponding relationship being a corresponding relationship between a signal waveform of seismic data collected by the acquisition device and time; calculating an average value of the amplitude values of the multi-channel downgoing wave seismic data; and placing the average value at a position of the imaging point.

[0025] Optionally, the migration of each of the downgoing wave seismic data according to the calculated travel time of each of the downgoing wave seismic data includes: determining an amplitude value of downgoing wave seismic data corresponding to the travel time of each of the downgoing wave seismic data according to a corresponding relationship and the travel time of each of the downgoing wave seismic data, the corresponding relationship being a corresponding relationship between a signal waveform of seismic data collected by the acquisition device and time; and placing the determined amplitude value of each of the downgoing wave seismic data at a position of the imaging point.

[0026] In a second aspect, a pre-stack time migration device for downgoing wave seismic data is provided, and the device includes:

[0027] The acquisition module is configured to acquire seismic data collected by acquisition devices at a plurality of detection points, the plurality of detection points being located on a sea bottom surface, each detection point being provided with an acquisition device, the acquisition device being configured to collect seismic waves reflected by a sea bottom formation and emitted by an emission device at a shot point, to obtain the seismic data, the shot point being located on a sea level; the processing module is configured to obtain multi-channel downgoing wave seismic data based on the seismic data; the calculation module is configured to calculate a travel time of each channel of the downgoing wave seismic data from the shot point to an imaging point according to a root mean square velocity of the imaging point with a sea level as a reference surface; calculate a travel time of each channel of the downgoing wave seismic data from the imaging point to an intersection of a horizontal line passing through a corresponding detection point and a reflection line passing through the imaging point according to the root mean square velocity of the imaging point with the sea level as the reference surface; calculate a travel time of each channel of the downgoing wave seismic data from the intersection to a mirror point of the corresponding detection point according to a seawater velocity with the sea level as the reference surface; and sum the calculated travel time of each channel of the downgoing wave seismic data from the shot point to the imaging point, the travel time of the imaging point to the intersection, and the travel time of the intersection to the corresponding detection point as a travel time of each channel of the downgoing wave seismic data; and the migration module is configured to migrate the multi-channel downgoing wave seismic data according to the calculated travel time of each channel of the downgoing wave seismic data.

[0028] Optionally, the calculation module is further configured to calculate the travel time of each channel of the downgoing wave seismic data from the shot point to the imaging point according to the following formula:

[0029]

[0030] wherein t1 is the travel time of each channel of the downgoing wave seismic data from the shot point to the imaging point, x s is a horizontal distance from the shot point to the imaging point, and v is the corresponding root mean square velocity of the imaging point with the sea level as the reference surface.

[0031] The calculation module is configured to calculate the travel time of each channel of the downgoing wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding detection point and the reflection line passing through the imaging point according to the following formula:

[0032]

[0033] wherein t2 is the travel time of each channel of the downgoing wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding detection point and the reflection line passing through the imaging point, t is a one-way vertical time of the imaging point with the sea level as the reference surface, d is a sea bottom depth of the detection point, v is the corresponding root mean square velocity of the imaging point with the sea level as the reference surface, and x gOR is the horizontal distance from the intersection point of the horizontal line through the receiver point and the reflection line through the imaging point to the receiver point;

[0034] The travel time of each trace of the down-going wave seismic data from the intersection point to the mirror point of the corresponding receiver point is calculated according to the following formula:

[0035]

[0036] wherein t3 is the travel time of each trace of the down-going wave seismic data from the intersection point to the mirror point of the corresponding receiver point, OR is the horizontal distance from the intersection point of the horizontal line through the receiver point and the reflection line through the imaging point to the receiver point, d is the depth of the seabed where the receiver point is located, v is one of the plurality of speed values, and t is the one-way vertical time at the imaging point with the sea level as the reference surface; the amplitude value of the plurality of traces of the down-going wave seismic data participating in imaging of the imaging point is determined according to the calculated travel time corresponding to each of the speed values; the amplitude values of the plurality of traces of the down-going wave seismic data corresponding to each of the determined speed values are stacked to obtain a plurality of stacked amplitude values; and the speed value corresponding to the maximum stacked amplitude value in the plurality of stacked amplitude values is taken as the root mean square speed of the imaging point with the sea level as the reference surface. w is the seawater speed.

[0037] Optionally, the computing module is further configured to take a plurality of speed values at intervals in a set speed range; and the travel time corresponding to each of the speed values is calculated according to the following formula:

[0038]

[0039] wherein x s is the horizontal distance from the shot point to the imaging point, x g is the horizontal distance from the receiver point to the imaging point, d is the depth of the seabed where the receiver point is located, v is one of the plurality of speed values, and t is the one-way vertical time at the imaging point with the sea level as the reference surface; the amplitude value of the plurality of traces of the down-going wave seismic data participating in imaging of the imaging point is determined according to the calculated travel time corresponding to each of the speed values; the amplitude values of the plurality of traces of the down-going wave seismic data corresponding to each of the determined speed values are stacked to obtain a plurality of stacked amplitude values; and the speed value corresponding to the maximum stacked amplitude value in the plurality of stacked amplitude values is taken as the root mean square speed of the imaging point with the sea level as the reference surface.

[0040] Optionally, the migration module is further configured to determine the amplitude value of the down-going wave seismic data corresponding to the travel time of each of the plurality of traces of the down-going wave seismic data according to the corresponding relationship and the travel time of each of the plurality of traces of the down-going wave seismic data, the corresponding relationship being the corresponding relationship between the signal waveform of the seismic data collected by the acquisition device and time; calculate the average value of the amplitude values of the plurality of traces of the down-going wave seismic data; and place the average value at the imaging point position.

[0041] Optionally, the migration module is further configured to determine an amplitude value of the down-going wave seismic data corresponding to the travel time of each trace of the down-going wave seismic data according to a corresponding relationship between a signal waveform of the seismic data collected by the acquisition device and time, and place the determined amplitude value of each trace of the down-going wave seismic data at the position of the imaging point.

[0042] In a third aspect, a computer device is provided, comprising: a processor; a memory for storing processor-executable instructions; wherein the processor is configured to execute the method of the first aspect.

[0043] In a fourth aspect, a computer-readable storage medium is provided, which, when instructions in the computer-readable storage medium are executed by a processor of a computer device, enables the computer device to execute the method of the first aspect.

[0044] The technical scheme provided by the embodiments of the present disclosure has the following beneficial effects:

[0045] In the embodiments of the present disclosure, the travel time of the down-going wave seismic data is the travel time from a shot point to an imaging point in a seabed formation, the travel time from the imaging point to a sea surface, and the travel time from the sea surface to a receiver point. When calculating the travel time of the down-going wave seismic data from the imaging point to the receiver point, the root-mean-square velocity corresponding to the seabed surface as a reference surface at the imaging point is modified to the root-mean-square velocity corresponding to the seabed surface as a reference surface, that is, the travel time of the down-going wave seismic data is calculated with the sea surface as a reference surface, which can make the calculation of the travel time of the down-going wave seismic data from the imaging point to the receiver point more accurate, and further can make the calculated travel time of the down-going wave seismic data more accurate, and improve the migration accuracy of the down-going wave seismic data. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical schemes in the embodiments of the present disclosure, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0047] Figure 1 is a scene schematic diagram of collecting seismic data provided by the embodiments of the present disclosure;

[0048] Figure 2 is a flowchart of a pre-stack time migration method of down-going wave seismic data provided by the embodiments of the present disclosure;

[0049] Figure 3 is a schematic diagram of a result of pre-stack time migration of down-going wave seismic data provided by the embodiments of the present disclosure;

[0050] Figure 4 This is a schematic diagram of another result of pre-stack time migration of down-wave seismic data provided in an embodiment of this disclosure;

[0051] Figure 5 This is a schematic diagram of the structure of a pre-stack time migration device for down-wave seismic data provided in an embodiment of this disclosure;

[0052] Figure 6 This is a structural block diagram of a computer device provided in an embodiment of this disclosure. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0054] To facilitate understanding of the embodiments of this disclosure, we will first introduce the scenario of acquiring seismic data in the embodiments of this disclosure.

[0055] Figure 1 This is a schematic diagram illustrating a scenario for acquiring seismic data, provided in an embodiment of this disclosure. See also... Figure 1 A gun point S is set on the sea surface, and multiple receiver points R are set on the seabed. Figure 1 The illustration uses one shot point S and one receiver point R as an example. In actual applications, there is one shot point S and multiple receiver points R. The positional arrangement of the shot point S and the multiple receiver points R is fixed, and the multiple receiver points R move as the shot point S moves.

[0056] The system includes a shot point S equipped with equipment for transmitting seismic waves. Each geophone point R is equipped with acquisition equipment to collect seismic waves reflected from the seabed strata, thus obtaining seismic data. A single shot emitted by the equipment at shot point S contains multiple seismic waves. These waves propagate to the seabed strata, are reflected at imaging point M, and then propagate to the seabed surface where they are collected by acquisition equipment at multiple geophone points R. All multiple shots emitted by the equipment at shot point S are collected by acquisition equipment at multiple geophone points R. In some examples, the equipment at shot point S emits one or more shots at a single location, which are then collected by acquisition equipment at multiple geophone points R. The equipment at shot point S and the acquisition equipment at multiple geophone points R then move to the next location to emit and collect data. For a single shot emitted by the equipment at shot point S, each acquisition equipment at geophone point R collects one seismic wave reflected from the seabed strata within that shot, obtaining seismic data. The seismic data collected by acquisition equipment at multiple geophone points R corresponding to the same shot constitutes a single-shot seismic data record.

[0057] In some embodiments, the acquisition device is an OBN (Ocean bottom node). The OBN is a four-component geophone arranged on the sea floor, which is composed of four component geophones. One of the component geophones is a pressure geophone for recording a pressure component. The other three component geophones are velocity geophones for recording three vertical velocity components.

[0058] Figure 2 is a flowchart of a pre-stack time migration method of downgoing wave seismic data provided by an embodiment of the present disclosure. The method can be executed by a computer device, such as a computer, etc. Referring to Figure 2 , the method comprises:

[0059] In step 201, seismic data collected by acquisition devices at a plurality of geophones is obtained.

[0060] The seismic data is collected by the acquisition devices arranged at the plurality of geophones R. After the transmitting device at the shot point S transmits a shot data, the acquisition device at each geophone R collects a seismic wave reflected by the seabed strata after the shot data, to obtain a seismic data. The computer device can obtain the seismic data collected by the plurality of acquisition devices by communicating with the acquisition devices arranged at the plurality of geophones R.

[0061] When the acquisition device is an OBN, the collected seismic data includes a pressure component P, a velocity component X, a velocity component Y, and a velocity component Z, wherein the velocity component X and the velocity component Y are parallel to the sea level, and the velocity component Z is perpendicular to the sea level.

[0062] In step 202, a plurality of downgoing wave seismic data is obtained based on the seismic data.

[0063] In the embodiment of the present disclosure, the acquisition device at each geophone R collects a plurality of seismic data, each of which is from a different shot data transmitted by the shot point S. The seismic data collected by the acquisition device at the geophone R includes upgoing wave seismic data and downgoing wave seismic data. The propagation path of the upgoing wave seismic data includes two segments of the shot point to the imaging point and the imaging point to the geophone, and the propagation path of the downgoing wave seismic data includes three segments of the shot point to the imaging point, the imaging point to the sea level, and the sea level to the geophone. That is, the reflected wave collected by the geophone and propagating from down to up is the upgoing wave seismic data, and the reflected wave collected by the geophone and propagating from up to down is the downgoing wave seismic data. As shown in Figure 1As shown, in the embodiments of the present disclosure, the propagation path of the downgoing seismic data is divided into three sections, i.e., a shot point S to an imaging point M, the imaging point M to a point O, and the point O to a point R', wherein the point O is the intersection of the horizontal line of the receiver point R and the reflection line MR' of the imaging point M, and the point R' is the mirror image point of the receiver point R with the sea level as the mirror image interface. The propagation path of the seismic wave from the sea level to the receiver point R is equivalent to the path from the sea level to the mirror image point R' of the receiver point R. Since only the downgoing seismic data is needed in the embodiments of the present disclosure, the seismic data collected by the acquisition device needs to be processed to obtain the downgoing seismic data.

[0064] Exemplarily, the process of processing the seismic data includes:

[0065] First step: the pressure component P in the seismic data is de-noised, deconvoluted and amplitude matched to obtain the processed pressure component P. The vertical velocity component Z in the three mutually perpendicular velocity components X, Y and Z in the seismic data is de-noised, deconvoluted and amplitude matched to obtain the processed vertical velocity component Z.

[0066] Second step: the downgoing seismic data is determined according to the processed pressure component P and the processed vertical velocity component Z.

[0067] Exemplarily, the processed pressure component P and the processed vertical velocity component Z in the first step are separated by formula (1) to obtain the downgoing seismic data.

[0068] U = (P - p c Z) / 2 (1)

[0069] In formula (1), U represents the downgoing seismic data, P is the processed pressure component, Z is the processed vertical velocity component, p is the density of water, and c is the sound wave velocity.

[0070] In the embodiments of the present disclosure, the multi-channel downgoing seismic data is the multi-channel downgoing seismic data participating in the same imaging point M and within the offset aperture range of the imaging point M.

[0071] The offset aperture range refers to the distance range from the imaging point M. The coordinates of the shot point S are known, and the multi-channel downgoing seismic data refers to the multi-channel downgoing seismic data corresponding to the multi-shot data emitted by the shot point S in the offset aperture range.

[0072] The offset aperture range is an empirical value. Exemplarily, the coordinates of the imaging point M are (Px, Py), wherein Px-Dx < Px < Px+Dx, Py-Dy < Py < Py+Dy, and the values of Dx and Dy are between 5000 meters and 6000 meters.

[0073] In step 203, the travel time of each down-going wave seismic data from the shot point to the imaging point is calculated according to the root mean square velocity at the imaging point with the sea level as the reference surface.

[0074] In some examples, the travel time of each down-going wave seismic data from the shot point to the imaging point is calculated according to the following formula:

[0075]

[0076] In formula (2), t1 is the travel time of each down-going wave seismic data from the shot point to the imaging point, x s is the horizontal distance from the shot point to the imaging point, and v is the corresponding root mean square velocity at the imaging point with the sea level as the reference surface.

[0077] In step 204, the travel time of each down-going wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding geophone point and the reflection line passing through the imaging point is calculated according to the root mean square velocity at the imaging point with the sea level as the reference surface.

[0078] In some examples, the travel time of each down-going wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding geophone point and the reflection line passing through the imaging point is calculated according to the following formula:

[0079]

[0080] In formula (3), t2 is the travel time of each down-going wave seismic data from the imaging point to the intersection of the horizontal line passing through the corresponding geophone point and the reflection line passing through the imaging point, t is the corresponding one-way vertical time at the imaging point with the sea level as the reference surface, d is the depth of the sea bottom where the geophone point is located, v is the corresponding root mean square velocity at the imaging point with the sea level as the reference surface, x g is the horizontal distance from the geophone point to the imaging point, and OR is the horizontal distance from the intersection of the horizontal line passing through the geophone point and the reflection line passing through the imaging point to the geophone point.

[0081] In step 205, the travel time of each down-going wave seismic data from the intersection to the mirror point of the corresponding geophone point is calculated according to the seawater velocity with the sea level as the reference surface.

[0082] In some examples, the travel time of each down-going wave seismic data from the intersection to the mirror point of the corresponding geophone point is calculated according to the following formula:

[0083]

[0084] In formula (4), t3 is the travel time of each down-going wave seismic data from the intersection to the mirror point of the corresponding geophone point, OR is the horizontal distance from the intersection of the horizontal line passing through the geophone point and the reflection line passing through the imaging point to the geophone point, d is the depth of the sea bottom where the geophone point is located, v wis the velocity of the seawater.

[0085] Since the coordinates of the shot point S, the imaging point M and the receiver point R are known, x s can be obtained from the coordinates of the shot point S and the coordinates of the imaging point M, x g can be obtained from the coordinates of the imaging point M and the coordinates of the receiver point R. d can be measured by the seismic detector. w is an empirical value, and exemplarily, given v w is 1500 m / s. OR can be calculated according to formula (5) as follows:

[0086]

[0087] In formula (5), OR represents the horizontal distance between the intersection point of the horizontal line of the receiver point and the reflection line of the imaging point, t represents the one-way vertical time corresponding to the imaging point with the sea level as the reference surface, v represents the root mean square velocity corresponding to the imaging point with the sea level as the reference surface, and h represents the distance between the shot point and the receiver point.

[0088] v is obtained through velocity analysis, and in some embodiments, the velocity analysis process is as follows:

[0089] Firstly, for a certain imaging point M, a plurality of velocity values are taken at intervals in a set velocity range.

[0090] The velocity range is an empirical value, and exemplarily, the velocity range is set to 3000 km / s-5000 km / s, and the velocity interval is set to 50 km / s.

[0091] Secondly, the travel time corresponding to each velocity value is calculated by using the following formula:

[0092]

[0093] In formula (6), x s is the horizontal distance from the shot point to the imaging point, x g is the horizontal distance from the receiver point to the imaging point, d is the depth of the seabed where the receiver point is located, v is one of the plurality of velocity values, and t is the one-way vertical time corresponding to the imaging point with the sea level as the reference surface.

[0094] Thirdly, the amplitude value of the multi-channel downgoing wave seismic data participating in the imaging of the imaging point is determined according to the calculated travel time corresponding to each velocity value.

[0095] Fourthly, the amplitude values of the multi-channel downgoing wave seismic data corresponding to each determined velocity value are stacked to obtain a plurality of stacked amplitude values.

[0096] In the fifth step, the speed value corresponding to the maximum superimposed amplitude value in the plurality of superimposed amplitudes is taken as the root-mean-square speed value of the imaging point corresponding to the sea level reference plane.

[0097] It should be noted that in the embodiments of the present disclosure, each geological layer in the seabed geological profile has a plurality of imaging points, and the root-mean-square speed value of the imaging point corresponding to the sea level reference plane is obtained by performing speed analysis on part of the imaging points. The root-mean-square speed value of the imaging point corresponding to the sea level reference plane can be obtained by the inverse distance interpolation method. For example, the seabed geological profile includes 100 geological layers, and each geological layer is provided with 10 imaging points. The root-mean-square speed value of the first, tenth, twentieth, thirtieth, fortieth, fiftieth, sixtieth, seventieth, eightieth, ninetieth and hundredth imaging points of the first, tenth, twentieth, thirtieth, fortieth, fiftieth, sixtieth, seventieth, eightieth, ninetieth and hundredth geological layers can be calculated according to the speed analysis method. The root-mean-square speed values of the imaging points between the first and tenth imaging points in the first geological layer can be calculated by the inverse distance interpolation method according to the root-mean-square speed difference between the first and tenth imaging points.

[0098] In step 206, the sum of the travel time of each down-going wave seismic data from the shot point to the imaging point, the travel time of the imaging point to the intersection point, and the travel time of the intersection point to the corresponding geophone is taken as the travel time of each down-going wave seismic data.

[0099] In step 207, the multi-channel down-going wave seismic data is migrated according to the calculated travel time of each down-going wave seismic data.

[0100] In some embodiments, migrating the multi-channel down-going wave seismic data includes:

[0101] In the first step, the amplitude value of the down-going wave seismic data corresponding to the travel time of each down-going wave seismic data is determined according to the corresponding relationship and the travel time of each down-going wave seismic data.

[0102] For example, the corresponding relationship is the corresponding relationship between the signal waveform of the seismic data collected by the acquisition device and the time. The corresponding relationship between the signal waveform of the seismic data collected by the acquisition device and the time is recorded in the acquisition device at each geophone. The data obtained by the computer device from each acquisition device includes the seismic data collected by the acquisition device and the corresponding relationship between the signal waveform of the seismic data and the time.

[0103] According to the travel time of the downgoing wave seismic data and the corresponding relationship between the signal waveform of the seismic data collected by the corresponding acquisition device and the time, the accurate amplitude value of the downgoing wave seismic data can be obtained, and then the migration result according to the accurate amplitude value of the downgoing wave seismic data is more accurate.

[0104] In the second step, the average value of the amplitude values of the multi-channel downgoing wave seismic data is calculated.

[0105] In the third step, the average value is placed at the position of the imaging point M.

[0106] After the calculated average value of the amplitude of the multi-channel downgoing wave seismic data is placed at the position of the imaging point M, the migration of the multi-channel downgoing wave seismic data is completed.

[0107] The amplitude value of the seismic data represents the energy of the seismic wave. The physical meaning of migration is to send the collected reflected seismic wave back to the reflection point position to make it image at the reflection point position.

[0108] Since the amplitude values of the multi-channel downgoing wave seismic data are directly placed at the imaging point M, the amplitude value at the imaging point M is large, and the large amplitude value will affect the imaging quality at the imaging point M. Therefore, placing the average amplitude value of the multi-channel downgoing wave seismic data at the imaging point can balance the amplitude values of the multi-channel downgoing wave seismic data, so that the imaging at the imaging point M will not be affected by the sum of the amplitude values of the multi-channel downgoing wave seismic data, and the imaging quality can be improved.

[0109] In other embodiments, the migration of the multi-channel downgoing wave seismic data comprises: determining the amplitude value of the downgoing wave seismic data corresponding to the travel time of each channel of downgoing wave seismic data according to the corresponding relationship and the travel time of each channel of downgoing wave seismic data, the corresponding relationship being the corresponding relationship between the signal waveform of the seismic data collected by the acquisition device and the time; and placing the determined amplitude value of each channel of downgoing wave seismic data at the position of the imaging point. Without affecting the imaging quality of the imaging point, the amplitude values of the multi-channel downgoing wave seismic data can be directly placed at the imaging point M.

[0110] Figure 3 the geological profile obtained by using the method of the related art for pre-stack time migration of downgoing wave seismic data, Figure 4 the geological profile obtained by using the method provided in the embodiments of the present disclosure for pre-stack time migration of downgoing wave seismic data. By comparison Figure 3 and Figure 4 it is found that Figure 4 each channel of the geological profile in Figure 3 is smoother than each channel of the geological profile in Figure 4 the stratum line in the black frame in Figure 3The horizon in the middle black line frame is smoothed. It is proved that the imaging accuracy according to the method of the embodiment of the present disclosure is better than that of the related art.

[0111] In the embodiment of the present disclosure, the travel time of the downgoing wave seismic data is from the shot point to the imaging point of the seabed formation, and the travel time from the imaging point to the receiver point. When calculating the travel time of the downgoing wave seismic data from the imaging point to the receiver point, the root mean square velocity corresponding to the seabed surface as the reference surface at the imaging point is modified to the root mean square velocity with the sea surface as the reference surface, that is, the travel time of the downgoing wave seismic data is calculated with the sea surface as the reference surface, which can make the calculation of the travel time of the downgoing wave seismic data from the imaging point to the receiver point according to the triangular formula more accurate, and further can make the calculated travel time of the downgoing wave seismic data more accurate, and improve the migration accuracy of the downgoing wave seismic data.

[0112] Figure 5 is a structural block diagram of a pre-stack time migration device 500 of downgoing wave seismic data provided by the embodiment of the present disclosure. As shown in the figure, the device comprises an acquisition module 501, a processing module 502, a calculation module 503 and a migration module 504. Figure 5

[0113] The acquisition module 501 is configured to acquire seismic data collected by an acquisition device at a plurality of receiver points, wherein the plurality of receiver points are located on a seabed surface, each receiver point is provided with an acquisition device, the acquisition device is configured to collect a seabed formation reflected seismic wave emitted by a launch device at a shot point to obtain the seismic data, and the shot point is located on a sea surface. The processing module 502 is configured to obtain a plurality of downgoing wave seismic data based on the seismic data. The calculation module 503 is configured to calculate a travel time of each downgoing wave seismic data from the shot point to an imaging point according to a root mean square velocity with the sea surface as the reference surface at the imaging point. The calculation module 503 is configured to calculate a travel time of each downgoing wave seismic data from the imaging point to an intersection point of a horizontal line passing through a corresponding receiver point and a reflection line passing through the imaging point according to the root mean square velocity with the sea surface as the reference surface at the imaging point. The calculation module 503 is configured to calculate a travel time of each downgoing wave seismic data from the intersection point to a mirror point of the corresponding receiver point according to a seawater velocity with the sea surface as the reference surface. The calculation module 503 is configured to take a sum of the calculated travel time of each downgoing wave seismic data from the shot point to the imaging point, the travel time of the imaging point to the intersection point and the travel time of the intersection point to the corresponding receiver point as the travel time of each downgoing wave seismic data. The migration module 504 is configured to migrate the plurality of downgoing wave seismic data according to the calculated travel time of each downgoing wave seismic data.

[0114] Optionally, the calculation module 503 is further configured to calculate the travel time of each downgoing wave seismic data from the shot point to the imaging point according to the following formula: ​

[0115]

[0116] wherein t1 is the travel time of each trace of the down-going wave seismic data from the shot point to the imaging point, x s is the horizontal distance from the shot point to the imaging point, and v is the corresponding root-mean-square velocity at the imaging point with respect to a sea level reference surface;

[0117] The travel time of each trace of the down-going wave seismic data from the imaging point to the intersection of the horizontal line through the corresponding receiver point and the reflection line through the imaging point is calculated according to the following formula:

[0118]

[0119] wherein t2 is the travel time of each trace of the down-going wave seismic data from the imaging point to the intersection of the horizontal line through the corresponding receiver point and the reflection line through the imaging point, t is the one-way vertical time at the imaging point, d is the depth of the seabed at the receiver point, v is the corresponding root-mean-square velocity at the imaging point with respect to a sea level reference surface, x g is the horizontal distance from the receiver point to the imaging point, and OR is the horizontal distance from the intersection of the horizontal line through the receiver point and the reflection line through the imaging point to the receiver point;

[0120] The travel time of each trace of the down-going wave seismic data from the intersection to the mirror point of the corresponding receiver point is calculated according to the following formula:

[0121]

[0122] wherein t3 is the travel time of each trace of the down-going wave seismic data from the intersection to the mirror point of the corresponding receiver point, OR is the horizontal distance from the intersection of the horizontal line through the receiver point and the reflection line through the imaging point to the receiver point, d is the depth of the seabed at the receiver point, and v w is the sea water velocity.

[0123] Optionally, the computing module 503 is further configured to take multiple velocity values at intervals within a set velocity range, and calculate the travel time corresponding to each of the velocity values according to the following formula:

[0124]

[0125] wherein x s is the horizontal distance from the shot point to the imaging point, and x gis a horizontal distance from the detection point to the imaging point, d is a depth of the seabed where the detection point is located, v is one of the plurality of velocity values, and t is a corresponding one-way vertical time of a sea level reference surface at the imaging point; determining an amplitude value of multi-channel downgoing wave seismic data participating in imaging of the imaging point according to the calculated travel time corresponding to each of the velocity values; stacking the determined amplitude value of the multi-channel downgoing wave seismic data corresponding to each of the velocity values to obtain a plurality of stacked amplitude values; and taking a velocity value corresponding to a maximum stacked amplitude value in the plurality of stacked amplitude values as a root mean square velocity of the sea level reference surface corresponding to the imaging point.

[0126] Optionally, the migration module 504 is further configured to determine an amplitude value of downgoing wave seismic data corresponding to a travel time of each of the multi-channel downgoing wave seismic data according to a corresponding relationship between a signal waveform of seismic data collected by the acquisition device and time and the travel time of each of the multi-channel downgoing wave seismic data, calculate an average value of the amplitude values of the multi-channel downgoing wave seismic data, and place the average value at the imaging point.

[0127] Optionally, the migration module 504 is further configured to determine an amplitude value of downgoing wave seismic data corresponding to a travel time of each of the multi-channel downgoing wave seismic data according to a corresponding relationship between a signal waveform of seismic data collected by the acquisition device and time and the travel time of each of the multi-channel downgoing wave seismic data, and place the determined amplitude value of each of the multi-channel downgoing wave seismic data at the imaging point.

[0128] It should be noted that the prestack time migration device 500 of downgoing wave seismic data provided in the above embodiments is only used as an example to divide the above functional modules when performing prestack time migration on downgoing wave data. In actual applications, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the prestack time migration device 500 of downgoing wave seismic data provided in the above embodiments and the prestack time migration method embodiment of downgoing wave seismic data belong to the same concept, and the specific implementation process is described in detail in the method embodiment, which will not be repeated here.

[0129] Figure 6 is a structural block diagram of a computer device provided by the embodiments of the present disclosure. As shown in Figure 6 the device includes a processor 601 and a memory 602.

[0130] Processor 601 may include one or more processing cores, such as a quad-core processor, an octa-core processor, etc. Processor 601 may be implemented using at least one hardware form selected from DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), and PLA (Programmable Logic Array). Processor 601 may also include a main processor and a coprocessor. The main processor, also known as a CPU (Central Processing Unit), is used to process data in the wake-up state; the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, processor 601 may integrate a GPU (Graphics Processing Unit), which is responsible for rendering and drawing the content to be displayed on the screen. In some embodiments, processor 601 may also include an AI (Artificial Intelligence) processor, which is used to handle computational operations related to machine learning.

[0131] The memory 602 may include one or more computer-readable storage media, which may be non-transitory. The memory 602 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices or flash memory devices. In some embodiments, the non-transitory computer-readable storage media in the memory 602 is used to store at least one instruction, which is executed by the processor 601 to implement the pre-stack time migration method for down-wave seismic data provided in the embodiments of this application.

[0132] Those skilled in the art will understand that Figure 6 The structure shown does not constitute a limitation on the computer device and may include more or fewer components than shown, or combine certain components, or use different component arrangements.

[0133] This invention also provides a non-transitory computer-readable storage medium, which, when the instructions in the storage medium are executed by the processor of a computer device, enables the computer device to execute the pre-stack time migration method for down-wave seismic data provided in this application.

[0134] A computer program product containing instructions, when run on a computer, causes the computer to execute the pre-stack time migration method for down-wave seismic data provided in the embodiments of this application.

[0135] The above merely describes optional embodiments of the present disclosure, and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A pre-stack time migration method for down-wave seismic data, characterized in that, The method includes: Seismic data is acquired from acquisition devices at multiple geophone points located on the seabed. Each geophone point is equipped with an acquisition device, which is used to acquire seismic waves emitted by a firing device at a shot point and reflected by the seabed strata to obtain the seismic data. The shot point is located at sea level. Based on the aforementioned seismic data, multichannel downwave seismic data were obtained; Based on the root mean square velocity at the imaging point relative to sea level, calculate the travel time of each downwave seismic data track from the shot point to the imaging point; Based on the root mean square velocity at the imaging point with sea level as the reference surface, calculate the travel time of each downwave seismic data track from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point. Based on the seawater velocity relative to sea level, calculate the travel time of each downwave seismic data track from the intersection point to the mirror point of the corresponding receiver point; The sum of the calculated travel time of each downwave seismic data track from the shot point to the imaging point, the travel time of the imaging point to the intersection point, and the travel time of the intersection point to the corresponding receiver point is taken as the travel time of each downwave seismic data track. The multi-channel downwave seismic data is offset based on the calculated travel time of each channel of the downwave seismic data. The step of calculating the travel time of each downwave seismic data track from the shot point to the imaging point based on the root mean square velocity at the imaging point relative to sea level includes: calculating the travel time of each downwave seismic data track from the shot point to the imaging point according to the following formula: Where t1 is the travel time of each downwave seismic data stream from the shot point to the imaging point, and x s Let v be the horizontal distance from the shot point to the imaging point, and v be the root mean square velocity at the imaging point relative to the sea level. The step of calculating the travel time of each downwave seismic data track from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point, based on the root mean square velocity at the imaging point with sea level as the reference plane, includes: calculating the travel time of each downwave seismic data track from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point according to the following formula: Where t2 is the travel time of each downwave seismic data path from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point; t is the one-way vertical time at the imaging point relative to sea level; d is the seabed depth at the receiver point; v is the root mean square velocity at the imaging point relative to sea level; and x... g OR is the horizontal distance from the detector point to the imaging point, and OR is the horizontal distance between the intersection of the horizontal line passing through the detector point and the reflection line passing through the imaging point and the detector point. The step of calculating the travel time of each downwave seismic data track from the intersection point to the mirror point of the corresponding receiver point based on the seawater velocity with sea level as the reference surface includes: calculating the travel time of each downwave seismic data track from the intersection point to the mirror point of the corresponding receiver point according to the following formula: Where t3 is the travel time of each downwave seismic data path from the intersection point to the corresponding mirror point of the receiver, OR is the horizontal distance between the receiver and the intersection point of the horizontal line passing through the receiver and the reflection line passing through the imaging point, d is the seabed depth where the receiver is located, and v w The speed of the seawater.

2. The method according to claim 1, characterized in that, The method further includes: Take multiple speed values ​​at intervals within a set speed range; The travel time for each speed value is calculated using the following formula: Where, x s x is the horizontal distance from the shot point to the imaging point. g d is the horizontal distance from the detector point to the imaging point, v is the seabed depth where the detector point is located, v is one of the multiple velocity values, and t is the one-way vertical time at the imaging point with the sea level as the reference plane. Based on the travel time corresponding to each of the calculated velocity values, the amplitude values ​​of the multichannel downwave seismic data participating in the imaging of the imaging point are determined; The amplitude values ​​of the multiple down-wave seismic data corresponding to each determined velocity value are superimposed to obtain multiple superimposed amplitude values; The velocity value corresponding to the maximum superimposed amplitude among the multiple superimposed amplitude values ​​is taken as the root mean square velocity of the imaging point with sea level as the reference surface.

3. The method according to claim 1, characterized in that, The step of migrating each downwave seismic data track based on the calculated travel time of each track includes: Based on the correspondence and the travel time of each downwave seismic data track, the amplitude value of the downwave seismic data corresponding to the travel time of each downwave seismic data track is determined. The correspondence is the relationship between the signal waveform and time of the seismic data acquired by the acquisition device. Calculate the average amplitude values ​​of the multichannel downwave seismic data; Place the average value at the location of the imaging point.

4. The method according to claim 1, characterized in that, The step of migrating each downwave seismic data track based on the calculated travel time of each track includes: Based on the correspondence and the travel time of each downwave seismic data track, the amplitude value of the downwave seismic data corresponding to the travel time of each downwave seismic data track is determined. The correspondence is the relationship between the signal waveform and time of the seismic data acquired by the acquisition device. The amplitude value of each downwave seismic data point is determined and placed at the location of the imaging point.

5. A pre-stack time migration device for down-wave seismic data, characterized in that, The device includes: The acquisition module is used to acquire seismic data collected by acquisition devices at multiple geophone points located on the seabed. Each geophone point is equipped with an acquisition device, which is used to acquire seismic waves emitted by a firing device at a shot point and reflected by the seabed strata to obtain the seismic data. The shot point is located at sea level. The processing module is used to obtain multi-channel down-current seismic data based on the seismic data; The calculation module is used to calculate the travel time of each downwave seismic data track from the shot point to the imaging point based on the root mean square velocity at the imaging point relative to sea level; to calculate the travel time of each downwave seismic data track from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point based on the root mean square velocity at the imaging point relative to sea level; to calculate the travel time of each downwave seismic data track from the intersection point to the mirror point of the corresponding receiver point based on the seawater velocity relative to sea level; and to use the sum of the calculated travel times of each downwave seismic data track from the shot point to the imaging point, the travel time from the imaging point to the intersection point, and the travel time from the intersection point to the corresponding receiver point as the travel time of each downwave seismic data track. The offset module is used to offset the multi-channel downwave seismic data according to the calculated travel time of each channel of the downwave seismic data; The calculation module is also used to calculate the travel time of each downwave seismic data from the shot point to the imaging point according to the following formula: Where t1 is the travel time of each downwave seismic data stream from the shot point to the imaging point, and x s Let v be the horizontal distance from the shot point to the imaging point, and v be the root mean square velocity at the imaging point relative to the sea level. The travel time of each downwave seismic data track from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point is calculated using the following formula: Where t2 is the travel time of each downwave seismic data path from the imaging point to the intersection of the horizontal line passing through the corresponding receiver point and the reflection line passing through the imaging point; t is the one-way vertical time at the imaging point relative to sea level; d is the seabed depth at the receiver point; v is the root mean square velocity at the imaging point relative to sea level; and x... g OR is the horizontal distance from the detector point to the imaging point, and OR is the horizontal distance between the intersection of the horizontal line passing through the detector point and the reflection line passing through the imaging point and the detector point. The travel time of each downwave seismic data stream from the intersection point to the mirror point of the corresponding receiver point is calculated using the following formula: Where t3 is the travel time of each downwave seismic data path from the intersection point to the corresponding mirror point of the receiver, OR is the horizontal distance between the receiver and the intersection point of the horizontal line passing through the receiver and the reflection line passing through the imaging point, d is the seabed depth where the receiver is located, and v w The speed of the seawater.

6. The apparatus according to claim 5, characterized in that, The offset module is also used to determine the amplitude value of the downwave seismic data corresponding to the travel time of each downwave seismic data according to the correspondence and the travel time of each downwave seismic data. The correspondence is the correspondence between the signal waveform and time of the seismic data acquired by the acquisition device. Calculate the average amplitude value of the multichannel downwave seismic data; place the average value at the imaging point location.

7. A computer device, characterized in that, include: processor; Memory used to store processor-executable instructions; The processor is configured to perform the method as described in any one of claims 1 to 4.

8. A computer-readable storage medium, characterized in that, When the instructions in the computer-readable storage medium are executed by the processor of a computer device, the computer device is able to perform the method as described in any one of claims 1 to 4.

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