Improved uplink and downlink wave field joint deconvolution method and device

Abstract

The invention discloses an improved uplink and downlink wave field joint deconvolution method and device, and belongs to the technical field of seismic exploration processing. The invention provides an improved uplink and downlink wave field joint deconvolution method and device based on the construction of a wave field propagation model of a real propagation process of an uplink and downlink wave field which more accords with reality, and the method comprises the steps: enabling the uplink wave field to move downwards for the water depth of two detection points, and then adaptively subtracting the uplink wave field from a downlink wave field, thereby obtaining a deconvolution model of the real propagation process of the uplink and downlink wave field; and then solving an inverse matrix of the result, and finally solving a stratum reflection coefficient by convolution of the inverse matrix and an upgoing wave field. The improved uplink and downlink wave field joint deconvolution method provided by the invention is simple, convenient and easy to implement, can effectively eliminate noise generated in a traditional method, and improves the signal-to-noise ratio of seismic data. The method can be applied to the field of seismic data processing.

Description

Technical Field

[0001] The invention belongs to the field of seismic exploration processing, and relates to an uplink and downlink wave field joint deconvolution method, in particular to an improved uplink and downlink wave field joint deconvolution method and device. Background Art

[0002] The joint deconvolution of uplink and downlink wave fields is a water layer multiple wave attenuation technology in the field of seismic data processing. It is widely used in the multiple wave suppression of seismic data from submarine cables (OBCs) or ocean bottom nodes (OBNs). Four component detectors are usually used to receive seismic data from OBCs or OBNs, which contain water layer multiple waves at the shot point end and the detection point end. The existence of these water layer multiple waves seriously affects the final imaging effect of the seismic data, and thus affects the final structural interpretation. Usually, people use the dual-detection synthesis technology to eliminate the water layer multiple waves at the detection point end, while the water layer multiple waves at the shot point end are mostly eliminated using the joint deconvolution of uplink and downlink wave fields.

[0003] The basic principle of the uplink and downlink wavefield joint deconvolution technology currently popular in the industry is that the uplink wavefield is a theoretical model of the convolution of the downlink wavefield and the formation reflection coefficient, and the formation reflection coefficient is obtained by joint deconvolution of the uplink and downlink wavefields. Through research, it is found that this model will generate a large number of false signals when obtaining the formation reflection coefficient, resulting in an inability to accurately describe the propagation characteristics of the wavefield, and thus cannot well describe the basic characteristics of the uplink and downlink wavefields received by the detection point. Summary of the invention

[0004] The present invention is based on the discovery that the upgoing wavefield in the seabed is the convolution of the source wavelet, the water depth and the formation reflection coefficient, and the downgoing wavefield is the sum of the convolution of the source wavelet and the water depth and the water depth of two detection points shifted downward from the upgoing wavefield. The formation reflection coefficient obtained based on this model can overcome the deficiency of the existing upgoing and downgoing wavefield joint deconvolution technology in generating a large number of false signals when obtaining the formation reflection coefficient.

[0005] Therefore, the object of the present invention is to provide an improved uplink and downlink wave field joint deconvolution method, which can effectively eliminate the influence of water layer multiple wave interference at the shot point end and improve the signal-to-noise ratio of seismic data.

[0006] Another object of the present invention is to provide a device for applying the improved uplink and downlink wavefield joint deconvolution method, which is beneficial to the promotion and application of the improved uplink and downlink wavefield joint deconvolution method.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] An improved uplink and downlink wavefield joint deconvolution method, the method comprises the following steps performed in sequence:

[0009] S1. Separate the upgoing wave field UP and the downgoing wave field DOWN in the seismic data;

[0010] S2. Shift the upgoing wave field UP down by two detection points by the water depth H to form UP*(-2H);

[0011] S3. adaptively subtract UP*(-2H) from the downlink wave field DOWN to obtain the matrix Z;

[0012] S4. Find the inverse matrix Z of matrix Z -1 ;

[0013] S5. Set the upgoing wave field UP and Z -1 Perform convolution to obtain the formation reflection coefficient R.

[0014] As a first limitation to the invention of an improved uplink and downlink wavefield joint deconvolution method,

[0015] In step S1, the seismic data includes submarine cable seismic data or submarine node seismic data;

[0016] The separation method includes separation by double-detection synthesis technology.

[0017] As a second limitation of the invention of an improved uplink and downlink wavefield joint deconvolution method, in step S1, after the separation, it also includes removing ghost waves at the detection point end.

[0018] As a third limitation of the invention of an improved uplink and downlink wavefield joint deconvolution method, in step S2, the method of moving down the water depth H of the two detection points includes moving the initial position in the seismic trace to a time of 2H / V and extending the trace head;

[0019] Among them, H is the water depth and V is the propagation speed of the earthquake source in the water.

[0020] As a fourth limitation of the invention of an improved uplink and downlink wavefield joint deconvolution method, in step S5, the formula for obtaining the formation reflection coefficient R is as shown in formulas 1 to 4,

[0021] UP=W*H*R Formula 1

[0022] Z=DOWN-UP*(-2H) Formula 2

[0023] Z*Z -1 =E Formula 3

[0024] R=UP*Z -1 Formula 4

[0025] Where W is the source wavelet, which belongs to the downgoing wave field; H is the water depth, which provides time shift; DOWN is the downgoing wave field; UP is the upgoing wave field; E is the unit matrix; and R is the formation reflection coefficient.

[0026] The present invention also provides a device for applying the above-mentioned improved upgoing and downgoing wavefield joint deconvolution method, the device comprising an upgoing wavefield and downgoing wavefield separation module, an upgoing wavefield downward movement module, an adaptive subtraction module, a matrix inversion module, a formation reflection coefficient obtaining module and a central control module;

[0027] The upgoing wavefield and downgoing wavefield separation module is used to separate the upgoing wavefield UP and the downgoing wavefield DOWN from the submarine cable seismic data or the submarine node seismic data through the double-detection synthesis technology;

[0028] The upgoing wavefield downward shifting module is used to shift the upgoing wavefield UP downward by two detection points water depth H to form UP*(-2H);

[0029] The adaptive subtraction module is used to adaptively subtract UP*(-2H) from the downlink wave field DOWN to obtain a matrix Z;

[0030] The matrix inversion module is used to obtain the inverse matrix Z of the matrix Z. -1 ;

[0031] The formation reflection coefficient obtaining module is used to convert the upgoing wave field UP and Z -1 Perform convolution to obtain the formation reflection coefficient R;

[0032] The central control module is used to control the signal flow and data processing in the upgoing wavefield and downgoing wavefield separation module, the upgoing wavefield downward movement module, the adaptive subtraction module, the matrix inversion module and the formation reflection coefficient obtaining module.

[0033] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0034] ① The traditional upgoing and downgoing wavefield joint deconvolution technology is based on the theoretical model that the upgoing wavefield is the convolution of the downgoing wavefield and the formation reflection coefficient; while the present invention considers that the upgoing wavefield is the convolution of the source wavelet, the water depth and the formation reflection coefficient, and the downgoing wavefield is the sum of the convolution of the source wavelet and the water depth and the water depth of two detection points down the upgoing wavefield, and a new wavefield propagation model is constructed based on this; compared with the traditional model, the present invention takes the convolution of the source and the water depth into consideration when constructing the downgoing wavefield model, and the constructed model is more in line with the actual propagation process of the upgoing and downgoing wavefields;

[0035] ② Based on the construction of a new wave field propagation model, the present invention establishes a new joint deconvolution method of upgoing and downgoing wave fields, that is, after the upgoing wave field is shifted down by two detection points in water depth, it is matched and subtracted from the downgoing wave field, and then the inverse matrix of the above result is obtained, and finally the above inverse matrix and the upgoing wave field are convolved to obtain the formation reflection coefficient; the result obtained by this method theoretically only has the formation reflection coefficient, and will not generate redundant noise like the original model, so the purpose of eliminating the multiple waves in the water layer at the shot point end can be achieved;

[0036] ③ The improved uplink and downlink wavefield joint deconvolution method provided by the present invention can effectively eliminate the noise generated by the traditional uplink and downlink wavefield joint deconvolution method and improve the signal-to-noise ratio of seismic data.

[0037] ④ The improved uplink and downlink wave field joint deconvolution method provided by the present invention is easy to implement and operate in exploration, and is conducive to popularization and application.

[0038] In summary, based on constructing a wave field propagation model that is more in line with the actual propagation process of the upgoing and downgoing wave fields, the present invention provides an improved upgoing and downgoing wave field joint deconvolution method and device, the method comprising adaptively subtracting the upgoing wave field from the downgoing wave field after it is shifted down by two detection point water depths, then calculating the inverse matrix of the above result, and finally convolving the inverse matrix with the upgoing wave field to obtain the formation reflection coefficient. The improved upgoing and downgoing wave field joint deconvolution method provided by the present invention is simple and easy to implement, and can also effectively eliminate the noise generated in the traditional method and improve the signal-to-noise ratio of seismic data.

[0039] The invention provides an improved uplink and downlink wave field joint deconvolution method and device, which can be applied to the field of seismic data processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Figure 1 This is a schematic diagram of the uplink and downlink wave field propagation model proposed by the present invention in Embodiment 1 of the present invention;

[0042] Figure 2 This is a flow chart of an improved uplink and downlink wavefield joint deconvolution method in Embodiment 1 of the present invention;

[0043] Figure 3 This is a schematic diagram of a traditional theoretical model in Example 1 of the present invention;

[0044] Figure 4 It is a schematic diagram of obtaining the formation reflection coefficient by the uplink and downlink wave field joint deconvolution method based on the traditional theoretical model in Example 1 of the present invention;

[0045] Figure 5It is a schematic diagram of obtaining the formation reflection coefficient for reconstructing the disk by using the up-and-down wave field joint deconvolution method constructed based on the traditional theoretical model in Example 1 of the present invention;

[0046] Figure 6 It is a schematic diagram of the process of obtaining the double-layer reflection coefficient by the uplink and downlink wave field joint deconvolution method constructed based on the traditional theoretical model in Example 1 of the present invention;

[0047] Figure 7 A result diagram of obtaining three-layer reflection coefficients using the uplink and downlink wave field joint deconvolution method based on the traditional theoretical model in Example 1 of the present invention;

[0048] Figure 8 The improved uplink and downlink wavefield joint deconvolution method in Example 1 of the present invention is used to obtain the three-layer reflection coefficient result diagram;

[0049] Fig. 9 The seismic single shot record diagram obtained by applying the traditional up-and-down wave field joint deconvolution method in Example 1 of the present invention;

[0050] Fig.10 A seismic single shot record obtained by applying the improved uplink and downlink wave field joint deconvolution method in Example 1 of the present invention;

[0051] Fig.11 A structural block diagram of an apparatus for applying an improved upgoing and downgoing wavefield joint deconvolution method provided in Example 2 of the present invention, wherein: 1-central control module, 2-upgoing wavefield and downgoing wavefield separation module, 3-upgoing wavefield downward movement module, 4-adaptive subtraction module, 5-matrix inversion module, 6-formation reflection coefficient obtaining module. DETAILED DESCRIPTION

[0052] The present invention will be further described in detail below by means of specific embodiments in combination with the accompanying drawings. It should be understood that the described embodiments are preferred examples of the present invention and are only used to explain the present invention and do not limit the present invention.

[0053] Example 1 An improved uplink and downlink wavefield joint deconvolution method

[0054] (I) The present invention summarizes a new uplink and downlink wave field propagation model by carefully analyzing and studying the seismic waves received by the seabed geophone and their propagation process; the schematic diagram of the uplink and downlink wave field propagation model proposed by the present invention is shown in Figure 1 As shown, the present invention considers that the upgoing wave field is the convolution of the source wavelet, the water depth and the formation reflection coefficient, and the downgoing wave field is the convolution of the source wavelet and the water depth and the sum of the water depths of two detection points shifted downward by the upgoing wave field;

[0055] By reverse analysis of the propagation model, an improved uplink and downlink wave field joint deconvolution processing method is obtained. The method specifically includes the following steps performed in sequence:

[0056] S1. On OBC seismic data or OBN seismic data, the upgoing wave field and the downgoing wave field are separated by double detection synthesis technology, and after removing the ghost wave at the detection point, the upgoing wave field UP and the downgoing wave field DOWN are obtained;

[0057] S2. Calculate the time 2H / V, where H is the depth of seawater and V is the propagation speed of the earthquake source in seawater;

[0058] Move the initial position in the seismic trace to the time of 2H / V, and extend the trace head by at least 2H / V;

[0059] That is, the upgoing wave field UP is moved down by two detection points with a water depth of H to form UP*(-2H);

[0060] S3. adaptively subtract UP*(-2H) from the downlink wave field DOWN to obtain the matrix Z;

[0061] S4. Find the inverse matrix Z of matrix Z -1 ;

[0062] S5. Set the upgoing wave field UP and Z -1 Perform convolution to obtain the formation reflection coefficient R;

[0063] The formulas used to calculate the formation reflection coefficient R are shown in formulas 1 to 4.

[0064] UP=W*H*R Formula 1

[0065] Z=DOWN-UP*(-2H) Formula 2

[0066] Z*Z -1 =E Formula 3

[0067] R=UP*Z -1 Formula 4

[0068] Where W is the source wavelet, which belongs to the downgoing wave field; H is the water depth, which provides time shift; DOWN is the downgoing wave field; UP is the upgoing wave field; E is the unit matrix; and R is the formation reflection coefficient.

[0069] (II) In order to investigate the difference between the improved uplink and downlink wavefield joint deconvolution method provided by the present invention and the uplink and downlink wavefield joint deconvolution method established based on the traditional theoretical model, the following experiment was conducted.

[0070] (1) The influence of different methods on the formation reflection coefficient

[0071] The up-down wavefield joint deconvolution technology currently popular in the industry mostly builds theoretical models based on the content of the article "Surface multiple attenuation by up-down wavefield deconvolution" published by Brunellière J et al. at the 2004 SEG Annual Meeting. Its basic principle is that the up-down wavefield is the convolution of the down-down wavefield and the formation reflection coefficient, and the purpose of obtaining the formation reflection coefficient is achieved through the joint deconvolution of the up-down wavefield. The schematic diagram of the traditional theoretical model is shown in the figure below. Figure 3 As shown, the formula for calculating the formation reflection coefficient based on the theoretical model in the comparison document is shown in formulas 5 to 6.

[0072] U=D*R Formula 5

[0073]

[0074] Where U is the upgoing wave field; D is the downgoing wave field; and R is the formation reflection coefficient.

[0075] The schematic diagram of the up-and-down wave field joint deconvolution method based on the traditional theoretical model to obtain the formation reflection coefficient is shown in the figure. Figure 4 As shown, the present invention simulates a single-layer formation by pulse signals, and reconstructs the process of obtaining the formation reflection coefficient by the up-and-down wave field joint deconvolution method based on the traditional theoretical model, as shown in the schematic diagram. Figure 5 As shown. Figures 4-5 It can be seen that the single-layer reflection coefficient result obtained by the uplink and downlink wave field joint deconvolution method based on the traditional theoretical model is correct.

[0076] Because the structure of the seabed strata is complex, it is not one layer but multiple layers. Therefore, the present invention uses pulse signal simulation to expand the original single layer into double and triple layers, and further obtains the double-layer reflection coefficient and triple-layer reflection coefficient based on the up-down wave field joint deconvolution method constructed based on the traditional theoretical model. The schematic diagram of the process of obtaining the double-layer reflection coefficient based on the up-down wave field joint deconvolution method constructed based on the traditional theoretical model is as follows Figure 6 As shown in the figure, the uplink and downlink wave field joint deconvolution method based on the traditional theoretical model is used to obtain the three-layer reflection coefficient. Figure 7 shown.

[0077] Depend on Figures 6-7 It can be seen that when the traditional uplink and downlink wave field joint deconvolution method is used to obtain the two-layer reflection coefficient or the three-layer reflection coefficient, the obtained double-layer reflection coefficient and the three-layer reflection coefficient both have a lot of noise, which cannot accurately describe the propagation characteristics of seismic waves, and thus cannot truly reflect the seabed geological structure.

[0078] The original single-layer stratum is extended into double and triple layers through pulse signal simulation, and the improved uplink and downlink wave field joint deconvolution method proposed in the present invention is applied to obtain the double-layer reflection coefficient and triple-layer reflection coefficient. The result of obtaining the triple-layer reflection coefficient by the method proposed in the present invention is shown in the figure below: Figure 8 As shown. Figure 8 It can be seen that the formation reflection coefficient obtained by the improved uplink and downlink wavefield joint deconvolution method proposed in the present invention does not have noise, which is consistent with the uplink and downlink wavefield propagation characteristics at the detection point end.

[0079] Depend on Figures 7-8 The comparison of the results shows that the improved uplink and downlink wave field joint deconvolution method proposed in the present invention effectively eliminates the noise generated by the traditional method, improves the signal-to-noise ratio of the seismic data, and also shows that the theoretical model of this method can well describe the propagation characteristics of seismic waves.

[0080] (2) The impact of different up- and down-going wave field joint deconvolution methods on seismic processing results

[0081] The formation reflection coefficient obtained by the traditional up-and-down wave field joint deconvolution method contains residual tails (such as Figure 7 The seismic single shot record obtained by this method is shown in Fig. 9 As shown;

[0082] The formation reflection coefficient (such as Figure 8 The seismic single shot record obtained by this method is shown in Figure 2. Fig.10 shown.

[0083] Depend on Figures 9-10 It can be seen that the seismic single-shot record obtained by applying the traditional uplink and downlink wavefield joint deconvolution method has remnants of multiple waves, resulting in false phase axes; while the seismic single-shot record obtained by applying the improved uplink and downlink wavefield joint deconvolution method proposed in the present invention can effectively avoid the defects of multiple wave remnants or false phase axes.

[0084] Embodiment 2: A device using an improved uplink and downlink wavefield joint deconvolution method

[0085] This embodiment provides a device using an improved uplink and downlink wavefield joint deconvolution method. The block diagram of the device is as follows: Fig.11 As shown, it includes an upgoing wavefield and a downgoing wavefield separation module 2, an upgoing wavefield downward movement module 3, an adaptive subtraction module 4, a matrix inversion module 5, a formation reflection coefficient obtaining module 6 and a central control module 1, which are specifically as follows:

[0086] (1) The upgoing wavefield and downgoing wavefield separation module 2 is used to separate the upgoing wavefield and the downgoing wavefield from the submarine cable seismic data or the submarine node seismic data by using the double detection synthesis technology, and after removing the ghost waves at the detection point end, the upgoing wavefield UP and the downgoing wavefield DOWN are obtained;

[0087] (2) The upgoing wave field downward movement module 3 is used to move the upgoing wave field UP downward by two detection points water depth H to form UP*(-2H);

[0088] (3) The adaptive subtraction module 4 is used to adaptively subtract UP*(-2H) from the downlink wave field DOWN to obtain the matrix Z;

[0089] (4) The matrix inversion module 5 is used to obtain the inverse matrix Z of the matrix Z -1 ;

[0090] (5) The formation reflection coefficient obtaining module 6 is used to convert the upgoing wave field UP and Z -1 Convolution is performed to obtain the formation reflection coefficient R; the formula used to obtain the formation reflection coefficient R is shown in formulas 1 to 4.

[0091] UP=W*H*R Formula 1

[0092] Z=DOWN-UP*(-2H) Formula 2

[0093] Z*Z -1 =E Formula 3

[0094] R=UP*Z -1 Formula 4

[0095] Where W is the source wavelet, which belongs to the downgoing wave field; H is the water depth, which provides time shift; DOWN is the downgoing wave field; UP is the upgoing wave field; E is the unit matrix; and R is the formation reflection coefficient.

[0096] (6) The central control module 1 is used to control the signal flow and data processing in the upgoing wavefield and downgoing wavefield separation module 2, the upgoing wavefield downward movement module 3, the adaptive subtraction module 4, the matrix inversion module 5 and the formation reflection coefficient calculation module 6.

[0097] The above description is only an optional embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. An improved uplink and downlink wavefield joint deconvolution method, characterized in that: The method comprises the following steps performed in sequence: S1. Separate the upgoing wave field UP and the downgoing wave field DOWN in the seismic data; S2. Shift the upgoing wave field UP down by two detection points by the water depth H to form UP*(-2H); S3. adaptively subtract UP*(-2H) from the downlink wave field DOWN to obtain the matrix Z; S4. Find the inverse matrix Z of matrix Z -1 ; S5. Set the upgoing wave field UP and Z -1 Perform convolution to obtain the formation reflection coefficient R.

2. The improved uplink and downlink wavefield joint deconvolution method according to claim 1, characterized in that: In step S1, the seismic data includes submarine cable seismic data or submarine node seismic data; The separation method includes separation by double-detection synthesis technology.

3. The improved uplink and downlink wavefield joint deconvolution method according to claim 1, characterized in that: In step S1, after the separation, the ghost waves at the detection point end are also removed.

4. The improved uplink and downlink wavefield joint deconvolution method according to claim 1, characterized in that: In step S2, The method of moving the water depth H of the two detection points downward includes moving the initial position in the seismic trace to a time of 2H / V and extending the trace head; wherein H is the water depth and V is the propagation speed of the earthquake source in the water.

5. An improved uplink and downlink wavefield joint deconvolution method according to any one of claims 1 to 4, characterized in that: In step S5, the formula for obtaining the formation reflection coefficient R is shown in formulas 1 to 4, UP=W*H*R Formula 1 Z=DOWN-UP*(-2H) Formula 2 Z*Z -1 =E Formula 3 R=UP*Z -1 Formula 4 Where W is the source wavelet, which belongs to the downgoing wave field; H is the water depth, which provides time shift; DOWN is the downgoing wave field; UP is the upgoing wave field; E is the unit matrix; and R is the formation reflection coefficient.

6. A device using an improved uplink and downlink wavefield joint deconvolution method according to any one of claims 1 to 5, characterized in that: The device includes an upgoing wave field and a downgoing wave field separation module, an upgoing wave field downward movement module, an adaptive subtraction module, a matrix inversion module, a formation reflection coefficient obtaining module and a central control module; The upgoing wavefield and downgoing wavefield separation module is used to separate the upgoing wavefield UP and the downgoing wavefield DOWN from the submarine cable seismic data or the submarine node seismic data through the double-detection synthesis technology; The upgoing wavefield downward shifting module is used to shift the upgoing wavefield UP downward by two detection points water depth H to form UP*(-2H); The adaptive subtraction module is used to adaptively subtract UP*(-2H) from the downlink wave field DOWN to obtain a matrix Z; The matrix inversion module is used to obtain the inverse matrix Z of the matrix Z. -1 ; The formation reflection coefficient obtaining module is used to convert the upgoing wave field UP and Z -1 Perform convolution to obtain the formation reflection coefficient R; The central control module is used to control the signal flow and data processing in the upgoing wavefield and downgoing wavefield separation module, the upgoing wavefield downward movement module, the adaptive subtraction module, the matrix inversion module and the formation reflection coefficient obtaining module.

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