A method for simulating regional noise in seismic exploration forward modeling

Abstract

The present invention discloses a method for simulating the noise in a work area for seismic forward modeling. The coordinates of the geophones at each geophone point in the work area are obtained through the seismic acquisition observation system; the noise-free seismic forward modeling data is obtained by using the seismic forward modeling algorithm; random noise sample data is collected by arranging stations in the work area; the mean value and variance of the random noise sample data of each station are calculated; the mean value and variance of the random noise at the geophone at each geophone point are obtained by interpolation; the random noise at the geophone at each geophone point is generated; the positions of the noise sources in the work area are investigated and stations are arranged near the noise sources to record the active noise sample data; the characteristic values of the active noise propagation are analyzed; the active noise record at the geophone at each geophone point is generated; and the random noise and the active noise at the geophone at each geophone point are appended to the seismic forward modeling data. The present invention makes the seismic forward modeling closer to the actual data by adding simulated noise conforming to the noise characteristics of the work area to the seismic forward modeling result.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas seismic exploration, and in particular to a method for simulating field noise for seismic forward modeling. Background Art

[0002] At present, the oil and gas seismic exploration technology has entered the high-density stage. Facing increasingly complex geological problems, the seismic acquisition technology is the key link to improve the quality of seismic exploration from the source of seismic data. The design of the acquisition geometry is an important part of the seismic acquisition technology, which directly determines the ability of seismic data to solve complex geological problems. With the development of seismic exploration, the design of the acquisition geometry has also shifted from the conventional design based on CMP attributes to the design oriented to geological targets. Conducting seismic forward modeling through building a 3D geological model and evaluating the acquisition geometry according to the results of seismic forward modeling is the current trend of technological development. In addition, seismic forward modeling has many other applications. For example, the effectiveness of new seismic data processing algorithms can be verified through forward modeling data. Seismic forward modeling is also often used in seismic data interpretation, and some abnormal phenomena in seismic data can be explained through forward modeling data.

[0003] Currently, the seismic data obtained by seismic forward modeling technology do not consider the actual noise in the field, and noise is an important factor affecting the seismic processing results. Only by considering the influence of the actual noise in the field can a more objective understanding be obtained.

[0004] Therefore, it is urgent to develop a method for simulating field noise for seismic forward modeling to solve the above technical problems. Summary of the Invention

[0005] The object of the present invention is to solve the deficiencies existing in the prior art, and provide a method for simulating field noise for seismic forward modeling, which adds simulated noise conforming to the field noise characteristics to the results of seismic forward modeling to make the seismic forward modeling closer to the actual data.

[0006] To achieve the above object, the present invention is implemented according to the following technical solution:

[0007] A method for simulating field noise for seismic forward modeling includes the following steps:

[0008] Step 1, obtaining the coordinates of the geophones at each geophone point in the field through the seismic acquisition geometry;

[0009] Step 2, obtaining noise-free seismic forward modeling data by using a seismic forward modeling algorithm;

[0010] Step 3, arranging stations in the field to collect random noise sample data;

[0011] Step 4, calculate the mean and variance of the random noise sample data for each station;

[0012] Step 5, interpolate to obtain the mean and variance of the random noise at the geophone of each geophone point;

[0013] Step 6, generate the random noise at the geophone of each geophone point;

[0014] Step 7, investigate the locations of the noise sources in the survey area and arrange stations near the noise sources to record the active noise sample data;

[0015] Step 8, analyze the characteristic values of the active noise propagation;

[0016] Step 9, generate the active noise record at the geophone of each geophone point;

[0017] Step 10, append the random noise and active noise at the geophone of each geophone point to the seismic forward modeling data.

[0018] Furthermore, in Step 6, generating the random noise at the geophone of each geophone point is carried out according to the following formula:

[0019] Z = a + b * u(0,1),

[0020] where z is the simulated random noise, a is the mean of the random noise obtained by interpolation, b is the variance of the random noise obtained by interpolation, and u(0,1) is the uniformly distributed noise with a mean of 0 and a variance of 1.

[0021] Furthermore, in Step 7, the noise sources in the surveyed area include but are not limited to drill rigs, pumping units, and mechanical interferences. The stations are arranged in an approximately straight line starting from the noise sources in the survey area and extending far away.

[0022] Furthermore, in Step 8, the specific characteristic values include: the position coordinates of the noise source, the depth of the noise source, the propagation speed of the noise, the frequency of the noise, and the energy attenuation formula of the noise source.

[0023] Furthermore, in Step 9, generating the active noise record at the geophone of each geophone point is represented by the following formula:

[0024]

[0025] where f(t) is the simulated noise, A is the energy at the geophone of the geophone point, w(t) is the noise waveform, l is the straight-line distance from the geophone of the geophone point to the noise source, and v is the propagation speed of the noise.

[0026] Furthermore, in Step 2, the seismic forward modeling algorithm used is one of the ray tracing, Gaussian beam, and wave equation methods.

[0027] Furthermore, in step 3, the station used has a data storage function capable of continuously recording data for a long period of time.

[0028] Furthermore, in step 5, the interpolation method used includes but is not limited to the following spatial interpolation methods: weighted inverse distance method, nearest neighbor method, and Kriging method.

[0029] Furthermore, the propagation speed of the noise is obtained by fitting the first arrival time and propagation distance of the sample active noise recorded at the station.

[0030] Furthermore, the energy attenuation formula of the noise source is expressed by the following formula:

[0031] A=A 0 e -br

[0032] Where A is the energy value of the active noise at the detector of the detection point, A 0 is the amplitude when the noise propagation distance is 0, r is the straight-line distance from the detector to the noise source at the detection point, and b is the attenuation index, which is obtained by fitting the sample active noise energy and propagation distance recorded by the station.

[0033] Compared with the prior art, the present invention adds simulated noise that conforms to the noise characteristics of the work area into the seismic exploration forward modeling results to make the seismic forward modeling closer to the actual data. This can solve the problem that conventional seismic forward modeling records lack objectivity in observation system evaluation, seismic data processing method effect testing, etc. due to the lack of real and reliable noise, and the results obtained are more real and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the observation system template for the Dongying A work area of ​​Shengli Oilfield.

[0035] Figure 2 Distribution of stations for collecting field noise samples in Dongying A work area of ​​Shengli Oilfield.

[0036] Figure 3 This is the random noise of the samples collected from the A work area in Dongying, Shengli Oilfield.

[0037] Figure 4 Forward simulation seismic data for the Dongying A work area of ​​Shengli Oilfield.

[0038] Figure 5 The forward modeling data with simulated random noise was added to the Dongying A area of ​​Shengli Oilfield.

[0039] Figure 6 This is the observation system template for the Dongying B work area of ​​Shengli Oilfield.

[0040] Figure 7For the distribution of field noise sample collection stations in the Dongying B work area of Shengli Oilfield.

[0041] Figure 8 For the sample drill rig noise collected in the Dongying B work area of Shengli Oilfield.

[0042] Figure 9 For the forward modeling data with simulated drill rig noise added in the Dongying B work area of Shengli Oilfield.

[0043] Figure 10 For the seismic data actually collected in the Dongying B work area of Shengli Oilfield.

[0044] Figure 11 For the flow chart of the present invention. Detailed implementation manners

[0045] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0046] Embodiment 1

[0047] Apply the present invention to a 3D seismic acquisition observation system design project of Sinopec Shengli Oilfield. This work area is located in Dongying City, Shandong Province. Figure 1 For the observation system template of the Dongying A work area of Shengli Oilfield; the detailed implementation manners are as Figure 11 shown:

[0048] Step 1, obtain the geophone coordinates of each geophone point in the work area through the seismic acquisition observation system;

[0049] Step 2, use the seismic forward modeling algorithm to obtain noise-free seismic forward modeling data; the seismic forward modeling algorithm used can be any one of the ray tracing, Gaussian beam, and wave equation methods; the obtained noise-free seismic forward modeling data conforms to the SEG-Y standard, and the coordinates of each geophone point are placed in the trace header. If it is data in other formats, the geophone coordinates corresponding to each trace of data also need to be provided;

[0050] Step 3, arrange stations in the work area to collect random noise sample data; the stations used must have the function of data storage and be able to continuously record data for a long time; the stations should be distributed as evenly as possible within the designed geophone range to ensure the reliability of subsequent processing. Figure 2 For the distribution of field noise sample collection stations in the Dongying A work area of Shengli Oilfield;

[0051] Step 4, calculate the mean and variance of the random noise sample data of each station; continuous data within the same time period as the actual construction time should be intercepted;

[0052] Step 5: Interpolate to obtain the mean and variance of the random noise at the geophone of each detection point. The interpolation methods used include, but are not limited to, the following spatial interpolation methods: weighted inverse distance method, nearest neighbor method, Kriging method, etc.

[0053] Step 6: Generate the random noise at the geophone of each detection point according to the following formula:

[0054] Z = a + b * u(0,1)

[0055] where z is the simulated random noise, a is the mean of the random noise obtained by interpolation, b is the variance of the random noise obtained by interpolation, and u(0,1) is the uniformly distributed noise with a mean of 0 and a variance of 1.

[0056] Step 7: Investigate the positions of the noise sources in the survey area and arrange stations near the noise sources to record the active noise sample data. The investigated noise sources include, but are not limited to, drill rigs, pumping units, mechanical interferences, etc. The stations are arranged in an approximately straight line starting from the noise sources and extending far away. Figure 3 The sample random noise collected for Area A of Dongying in Shengli Oilfield.

[0057] Step 8: Analyze the characteristic values of the active noise propagation. The specific characteristic values include the following: the position coordinates of the noise source, the depth of the noise source, the propagation speed of the noise, the frequency of the noise, the energy attenuation formula of the noise source, etc. Among them, the propagation speed of the noise is obtained by fitting the first arrival time and propagation distance of the sample active noise recorded by the stations. The energy attenuation formula of the noise source is expressed by the following formula:

[0058] A = A 0 e -br

[0059] where A is the energy value of the active noise at the geophone of the detection point, A 0 is the amplitude when the noise propagation distance is 0, r is the straight-line distance from the geophone of the detection point to the noise source, b is the attenuation exponent, and b is obtained by fitting the sample active noise energy and propagation distance recorded by the stations.

[0060] Step 9: Generate the active noise record at the geophone of each detection point. The generated simulated active noise record can be expressed by the following formula:

[0061]

[0062] where f(t) is the simulated noise, A is the energy at the geophone of the detection point, w(t) is the noise waveform, l is the straight-line distance from the geophone of the detection point to the noise source, and v is the propagation speed of the noise.

[0063] Step 10, append the random noise and active noise at the geophone of each detection point to the seismic forward modeling data. The energy ratio between the seismic forward modeling data and the noise simulation data is set according to the required signal-to-noise ratio. Figure 4 It is the forward modeled seismic data of Area A in Dongying of Shengli Oilfield.

[0064] Figure 5 It is the forward modeling data with simulated random noise added for Area A in Dongying of Shengli Oilfield. By comparing Figure 4 and Figure 5 , it can be seen that the result obtained by the method of the present invention is quite similar to the actual seismic data of the work area, indicating that the present invention adds simulated noise conforming to the noise characteristics of the work area to the forward modeling result of seismic exploration, making the seismic forward modeling closer to the actual data.

[0065] Example 2

[0066] Apply the present invention to a 3D seismic acquisition observation system design project of Shengli Oilfield of Sinopec. This work area is located in Dongying City, Shandong Province. Figure 6 It is the observation system template of Area B in Dongying of Shengli Oilfield; the specific implementation method is as Figure 11 shown:

[0067] Step 1, obtain the geophone coordinates of each detection point in the work area through the seismic acquisition observation system;

[0068] Step 2, use the seismic forward modeling algorithm to obtain noise-free seismic forward modeling data; the seismic forward modeling algorithm used can be any one of the ray tracing, Gaussian beam, and wave equation methods; the obtained noise-free seismic forward modeling data conforms to the SEG-Y standard, and the coordinates of each detection point are placed in the trace header. If it is data in other formats, the geophone coordinates corresponding to each trace data also need to be provided;

[0069] Step 3, arrange stations in the work area to collect random noise sample data; the stations used must have the function of data storage and be able to continuously record data for a long time; the stations should be distributed as evenly as possible within the designed geophone range to ensure the reliability of subsequent processing. Figure 7 It is the distribution of field noise sample collection stations in Area B in Dongying of Shengli Oilfield;

[0070] Step 4, calculate the mean and variance of the random noise sample data of each station; the continuous data within the time period same as the actual construction time should be intercepted;

[0071] Step 5, interpolate to obtain the mean and variance of the random noise at the geophone of each detection point; the interpolation methods used include but are not limited to the following spatial interpolation methods: weighted inverse distance method, nearest neighbor method, Kriging method, etc.;

[0072] Step 6: Generating random noise at the geophone of each detection point is carried out according to the following formula:

[0073] Z = a + b * u(0, 1)

[0074] where z is the simulated random noise, a is the mean value of the random noise obtained by interpolation, b is the variance of the random noise obtained by interpolation, and u(0, 1) is the uniformly distributed noise with a mean of 0 and a variance of 1;

[0075] Step 7: Investigating the positions of noise sources in the survey area and arranging stations near the noise sources to record active noise sample data; the investigated noise sources include but are not limited to drills, pumping units, mechanical interferences, etc. The stations are arranged in an approximately straight line starting from the noise sources and extending outward; Figure 8 The sample drill noise collected for Work Area B in Dongying of Shengli Oilfield;

[0076] Step 8: Analyzing the characteristic values of the propagation of active noise. The specific characteristic values include the following: the position coordinates of the noise source, the depth of the noise source, the propagation speed of the noise, the frequency of the noise, the energy attenuation formula of the noise source, etc. Among them, the propagation speed of the noise is obtained by fitting the first arrival time and propagation distance of the sample active noise recorded by the stations; the energy attenuation formula of the noise source is expressed by the following formula:

[0077] A = A 0 e -br

[0078] where A is the energy value of the active noise at the geophone of the detection point, A 0 is the amplitude when the noise propagation distance is 0, r is the straight-line distance from the geophone of the detection point to the noise source, and b is the attenuation exponent, which is obtained by fitting the sample active noise energy and propagation distance recorded by the stations;

[0079] Step 9: Generating the active noise record at the geophone of each detection point. The generated simulated active noise record can be expressed by the following formula:

[0080]

[0081] where f(t) is the simulated noise, A is the energy at the geophone of the detection point, w(t) is the noise waveform, l is the straight-line distance from the geophone of the detection point to the noise source, and v is the propagation speed of the noise;

[0082] Step 10: Appending the random noise and active noise at the geophone of each detection point to the seismic forward modeling data. The energy ratio of the seismic forward modeling data and the noise simulation data is set according to the required signal-to-noise ratio, Figure 9 The forward modeling data with simulated drill noise added for Work Area B in Dongying of Shengli Oilfield.

[0083] Figure 10 It is the seismic data actually collected from the Dongying B work area of Shengli Oilfield. By comparing Figure 9 and Figure 10 , it can be seen that the results obtained by the method of the present invention are comparable to the actual seismic data of the work area, indicating that the present invention adds simulated noise conforming to the noise characteristics of the work area to the forward simulation results of seismic exploration, making the seismic forward simulation closer to the actual data.

[0084] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A method for simulating noise in a work area for seismic forward modeling, characterized in that, it includes the following steps: Step 1, obtain the coordinates of the geophones at each geophone point in the work area through the seismic acquisition observation system; Step 2, use the seismic forward modeling algorithm to obtain noise-free seismic forward modeling data; Step 3, arrange stations in the work area to collect random noise sample data; Step 4, calculate the mean and variance of the random noise sample data at each station; Step 5, interpolate to obtain the mean and variance of the random noise at the geophones at each geophone point; Step 6, generate random noise at the geophones at each geophone point; Step 7, investigate the locations of the noise sources in the work area and arrange stations near the noise sources to record active noise sample data; Step 8, analyze the characteristic values of the propagation of active noise; Step 9, generate records of active noise at the geophones at each geophone point; Step 10, append the random noise and active noise at the geophones at each geophone point to the seismic forward modeling data; In the said Step 6, generating random noise at the geophones at each geophone point is carried out according to the following formula: Z = a + b*u(0,1), where, z is the simulated random noise, a is the mean of the random noise obtained by interpolation, b is the variance of the random noise obtained by interpolation, and u(0,1) is the uniformly distributed noise with a mean of 0 and a variance of 1; In the said Step 8, the specific characteristic values include: the position coordinates of the noise source, the depth of the noise source, the propagation speed of the noise, the frequency of the noise, the energy attenuation formula of the noise source; In the said Step 9, generating records of active noise at the geophones at each geophone point is represented by the following formula: where, f(t) is the simulated noise, A is the energy at the geophone at the geophone point, w(t) is the noise waveform, l is the straight-line distance from the geophone at the geophone point to the noise source, and v is the propagation speed of the noise.

2. The method for simulating noise in a work area for seismic forward modeling according to claim 1, characterized in that: In the said Step 7, the investigated noise sources in the work area include but are not limited to drill rigs, pumping units, and mechanical interferences, and the stations are arranged in an approximately straight-line manner starting from far away from the noise sources in the work area.

3. The method for simulating noise in a work area for seismic forward modeling according to claim 1, characterized in that: In Step 2, the seismic forward modeling algorithm used is one of the three methods of ray tracing, Gaussian beam, and wave equation.

4. The method for simulating noise in a work area for seismic forward modeling according to claim 1, characterized in that: In Step 3, the stations adopted have a data storage function that can continuously record data for a long time.

5. The method for simulating noise in a work area for seismic forward modeling according to claim 1, characterized in that: In Step 5, the interpolation methods adopted include but are not limited to the following spatial interpolation methods: weighted inverse distance method, nearest neighbor method, Kriging method.

6. The method for simulating noise in a work area for seismic forward modeling according to claim 4, characterized in that: The propagation speed of the noise is obtained by fitting the first arrival time and propagation distance of the sample active noise recorded by the stations.

7. The method for simulating noise in a work area for forward modeling in seismic exploration according to claim 4, characterized in that: the energy attenuation formula of the noise source is expressed by the following formula: A = A 0 e -br Among them, A is the energy value of the active noise at the geophone of the detection point, A 0 is the amplitude when the noise propagation distance is 0, r is the straight-line distance from the geophone of the detection point to the noise source, and b is the attenuation exponent, which is obtained by fitting the active noise energy and propagation distance of the samples recorded by the station.

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