Design method of observation system for continuous wave field acquisition

Abstract

The present invention provides a method for designing an observation system for continuous wavefield acquisition, which includes: step 1, establishing a geological model according to the geological tasks of the work area; step 2, obtaining basic parameters through simulation and demonstration analysis; step 3, analyzing and demonstrating the number of vertical and horizontal coverage; step 4, designing an observation system for continuous and sufficient vertical and horizontal acquisition; and step 5, evaluating the properties of the observation system. The observation system wavefield continuity obtained by adopting the observation system design method for continuous wavefield acquisition is good, which meets the needs of imaging, overcomes the shortcomings of wavefield acquisition of the current beam observation system, makes wavefield acquisition more sufficient and continuous, and is conducive to subsequent OVT domain denoising and fidelity imaging.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a design method of an observation system for continuous wave field acquisition. Background Art

[0002] The design of the observation system is the first step in seismic acquisition. How to choose the right observation system is crucial and determines the success or failure of seismic acquisition imaging. At present, the design form of the observation system is mainly a beam observation system, which adopts several lines and several shots, such as a 40-line 6-shot observation system. The longitudinal receiving track spacing is small, which can meet the needs of full and continuous acquisition of the wave field, while the lateral receiving line spacing is large, generally between 150m-200m. The large receiving line spacing is difficult to meet the needs of full wave field acquisition, so a smaller shot point spacing is used to compensate for it, and a relatively continuous acquisition of the wave field is achieved through lateral rolling. However, this wave field acquisition is only continuous in form and cannot achieve true continuous acquisition, which makes the discontinuity of the wave field in the OVT (OVT is a cross arrangement consisting of a shot line and a receiving line) gather stand out, which is not conducive to the fidelity imaging of the wave field.

[0003] In the Chinese patent application with application number: 201810818677.4, a method for evaluating a seismic exploration data acquisition and observation system in a complex tectonic area is involved, which is characterized by comprising: establishing a geological model based on historical seismic data and historical interpretation data, discretizing the geological model using grid spacing to obtain a grid geological model; establishing multiple sets of seismic exploration data acquisition and observation systems; establishing an initial model of a full waveform inversion model; using each set of seismic exploration data acquisition and observation systems in the multiple sets of seismic exploration data acquisition and observation systems to perform the following steps: using one of the seismic exploration data acquisition and observation systems to perform finite difference forward modeling on the grid geological model in the time and space domain to obtain simulated seismic observation data, wherein the simulated seismic observation data includes forward modeling parameters; performing the following iterative steps: using the same set of seismic exploration data acquisition and observation systems and the forward modeling parameters to perform forward modeling on the initial model to determine the forward direction of the shot point at each moment The invention discloses a method for obtaining a reverse propagation wave field and an initial model simulation data of a propagated seismic wave field and an initial model simulation data; calculating the observation data residual between the simulated seismic observation data and the initial model simulation data; using the initial model, taking the reverse time data of the observation data residual as the source at the detection point for forward simulation, and determining the reverse time propagation wave field of the detection point residual at different times; using the seismic wave field and the reverse time propagation wave field to calculate the velocity update amount; using the velocity update amount to update the initial model; using the updated initial model to continue to perform the iteration steps until the iteration ends when the velocity update amount meets the preset conditions, and obtaining the inversion velocity model; calculating the velocity approximation degree of each grid of the inversion velocity model and the variance of the velocity approximation degree; comparing multiple variances obtained by using multiple sets of seismic exploration data acquisition observation systems to obtain the minimum variance, and the seismic exploration data acquisition observation system corresponding to the minimum variance is the seismic exploration data acquisition observation system that meets the exploration requirements. This patent adopts the forward simulation method to simulate a forward single shot, and then invert the velocity model based on the single shot data, and correct the observation system from the residual of the inverted velocity model and the actual model, and iterates repeatedly to obtain the best observation system, that is, the velocity model inversion result of the single shot simulated by the observation system is the smallest difference from the actual model. The biggest problem of this invention is the simulation efficiency of the three-dimensional wave equation. The amount of data for three-dimensional wave field simulation is extremely large, and it usually takes several days to simulate a shot. For the observation system of the current conventional work area, the workload is at least about 20,000 shots. If three-dimensional wave field simulation is used, the calculation simulation is carried out 24 hours a day, and a large computer is used. It takes a year to simulate an observation system. This method aims to simulate repeatedly through inversion correction after the simulation is completed, so the workload is even greater, far exceeding the actual workload that can be borne at present, and much longer than the actual field work area acquisition time, and it can no longer meet the needs of correctly guiding the design of the observation system.

[0004] To this end, we invented a new wave field continuous acquisition observation system design method to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide a new technology proposed to solve the problem of wavefield discontinuity in wavefield acquisition in current observation systems, and to provide an observation system design method for continuous wavefield acquisition that can meet the requirements of sufficiency and continuity of next-step wavefield acquisition.

[0006] The purpose of the present invention can be achieved through the following technical measures: an observation system design method for continuous wave field acquisition, which includes: step 1, establishing a geological model according to the geological tasks of the work area; step 2, obtaining basic parameters through simulation and demonstration analysis; step 3, analyzing and demonstrating the number of vertical and horizontal coverage; step 4, designing an observation system for continuous and sufficient vertical and horizontal acquisition; step 5, evaluating the attributes of the observation system.

[0007] The purpose of the present invention can also be achieved by the following technical measures:

[0008] In step 1, according to the requirements of the geological task, relevant data are collected and a geological model is established. The collected data include stratigraphic data, velocity, depth, density, and seismic profile of each layer.

[0009] In step 2, the track spacing required for full and continuous acquisition of the wave field is analyzed through forward simulation. The wavelet of the wave field adopts the wavelet extracted from the actual data, and the different track spacings are changed. The track spacing selection changes from small to large in sequence, and the results along the arrangement direction inline and the vertical arrangement direction cross line are analyzed. At the same time, the maximum shot offsets in the inline and cross line directions are changed for simulation analysis to obtain the maximum shot offsets required in these two directions.

[0010] In step 3, based on the signal-to-noise ratio requirements, the number of coverage times and the vertical and horizontal coverage times required by the observation system are demonstrated. The vertical and horizontal coverage times determine the size of the vertical and horizontal shot point spacing.

[0011] In step 4, the basic parameters of the observation system are obtained through the above analysis and demonstration, and these parameters are used to design an observation system for continuous wave field acquisition.

[0012] In step 4, the same receiving point spacing is used in the vertical and horizontal directions. The maximum shot offset in the vertical and horizontal directions adopts the results of the previous demonstration. The shot point in the template is set to 1 shot. The vertical and horizontal shot point spacing is larger, and its specific size is calculated based on the number of coverage times in the vertical and horizontal directions.

[0013] In step 5, after designing the observation system, the properties of the observation system are evaluated and analyzed, requiring that the coverage times of the observation system are evenly distributed and the offset properties meet the uniformity requirements.

[0014] The design method of the observation system for continuous wave field acquisition in the present invention adopts a similar design method to the longitudinal design method in the horizontal direction, and the horizontal receiving point spacing is also set to be smaller, so that the horizontal wave field acquisition is more continuous and sufficient. The horizontal shot point spacing is similar to the longitudinal shot point spacing, but not necessarily exactly the same. A larger shot point spacing is also adopted, which can greatly reduce the number of shot points and reduce the difficulty of construction. The observation system designed by this method has significantly enhanced the continuity and sufficiency of wave field acquisition, which is conducive to improving the fidelity imaging of the wave field. It has been proved in practice that the observation system designed by this method has better wave field continuity, has better wave field continuity display in the OVT domain, and can better perform wave field fidelity imaging. Although the number of detection points used is large, the number of shot points is greatly reduced, reducing the cost of excitation points. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flowchart of a specific embodiment of the method for designing an observation system for continuous wave field acquisition of the present invention;

[0016] Figure 2 This is an observation system diagram obtained by using this method in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0017] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0018] The design method of the wave field continuous acquisition observation system of the present invention comprises the following steps:

[0019] Step 1: Collect relevant data and establish a geological model according to the geological task requirements;

[0020] Step 2: Analyze the track spacing required for full and continuous acquisition of the wave field through forward simulation. The wave field wavelet uses the wavelet extracted from the actual data, and changes the track spacing from small to large, such as 5m, 6m, 7m... The results in the inline and crossline directions need to be analyzed. At the same time, the maximum offset in the inline and crossline directions needs to be changed for simulation analysis to obtain the maximum offset required in these two directions;

[0021] Step 3: According to the signal-to-noise ratio requirement, the number of coverage times and the number of vertical and horizontal coverage times required by the observation system are demonstrated. The vertical and horizontal coverage times determine the size of the vertical and horizontal shot point spacing;

[0022] Step 4, through the above analysis and demonstration, the basic parameters of the observation system are obtained, and these parameters are used to design the observation system for continuous wave field acquisition. This method designs the observation system by using the same receiving point spacing in the vertical and horizontal directions, and the maximum vertical and horizontal offsets use the results of the previous demonstration. The shot point in the template is set to 1 shot, and the vertical and horizontal shot point spacing is relatively large, and its specific size needs to be calculated according to the number of vertical and horizontal coverage times;

[0023] Step 5: After designing the observation system, evaluate and analyze the properties of the observation system, requiring that the coverage times of the observation system are evenly distributed and the offset properties meet the uniformity requirements.

[0024] To facilitate understanding of the solution and effects of the embodiments of the present invention, a specific application example is given below. Those skilled in the art should understand that this example is only for facilitating understanding of the present invention, and any specific details thereof are not intended to limit the present invention in any way.

[0025] In order to make the purpose, features and advantages of the present invention more clearly understood, the following is a detailed description with reference to the accompanying drawings:

[0026] like Figure 1 As shown, Figure 1 A flow chart of a method for designing an observation system for continuous wave field acquisition.

[0027] In step 101, according to the geological task requirements, relevant data are collected, including stratigraphic data, seismic interpretation profiles, velocity density and other data, and a geological model of the work area is established based on these data. The process enters step 102.

[0028] In step 102, the track spacing required for full and continuous acquisition of the wave field is analyzed through forward simulation. The wave field wavelet uses the wavelet extracted from the actual data, and changes different track spacings. The selection of track spacing changes from small to large, such as 5m, 6m, 7m..., and the results in the inline and cross line directions need to be analyzed. At the same time, the maximum shot offset in the inline and cross line directions needs to be changed for simulation analysis to obtain the maximum shot offset required in these two directions. The determined longitudinal and transverse track spacings and the longitudinal and transverse maximum shot offsets determine the size of the array. Go to step 103.

[0029] In step 103, based on the signal-to-noise ratio requirement, the required coverage times and the vertical and horizontal coverage times of the observation system are verified, and the vertical and horizontal coverage times determine the vertical and horizontal shot point spacings. The process proceeds to step 104.

[0030] In step 104, the basic parameters of the observation system are obtained through the above analysis and demonstration, and the observation system for continuous wave field acquisition is designed using these parameters. The method of designing the observation system in this method adopts the same receiving point spacing in the vertical and horizontal directions, and the maximum shot offset in the vertical and horizontal directions adopts the results of the previous demonstration. The shot point in the template is set to 1 shot, and the vertical and horizontal shot point spacing is relatively large, and its specific size needs to be calculated according to the number of vertical and horizontal coverage times. The process enters step 105.

[0031] In step 105, after the observation system is designed, the observation system properties are evaluated and analyzed, requiring that the observation system coverage times are evenly distributed and the offset properties meet the uniformity requirements. The process ends.

[0032] Figure 2 The diagram shows the schematic diagram of the observation system obtained by using this method. The longitudinal and transverse track spacing of the observation system is small, so that the longitudinal and transverse surface elements are determined by the longitudinal and transverse track spacing. The shot points no longer bear the function of the surface elements, making the wave field acquisition more continuous and sufficient.

[0033] The design method of the observation system for continuous wavefield acquisition of the present invention fully considers the requirements of sufficiency and continuity of wavefield acquisition, firstly analyzes the basic parameters of the observation system by using the forward simulation method and the theoretical calculation method, and then designs the observation system capable of continuous wavefield acquisition according to the parameters. The rationality of the present invention has been verified by the actual observation system, and the wavefield continuity of the observation system obtained by the method is good, which meets the requirements of imaging, overcomes the shortcomings of the wavefield acquisition of the current beam observation system, makes the wavefield acquisition more sufficient and continuous, and is conducive to the subsequent OVT domain denoising and fidelity imaging.

[0034] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for designing an observation system for continuous wave field acquisition, characterized in that: The design method of the observation system for continuous wave field acquisition includes: In step 101, according to the geological task requirements, relevant data are collected, including stratigraphic data, seismic interpretation profiles, and velocity density data, and a geological model of the work area is established based on these data; In step 102, the track spacing required for full and continuous acquisition of the wave field is analyzed through forward simulation. The wave field wavelet uses the wavelet extracted from the actual data, and the different track spacings are changed. The track spacing selection is changed from small to large, and the results of the inline and crossline directions are analyzed. At the same time, the maximum offsets in the inline and crossline directions are changed to perform simulation analysis to obtain the maximum offsets required in the two directions. The determined longitudinal and transverse track spacings and the longitudinal and transverse maximum offsets determine the size of the array slice. In step 103, based on the signal-to-noise ratio requirement, the required number of coverages and the vertical and horizontal coverages of the observation system are verified. The vertical and horizontal coverages determine the vertical and horizontal shot point spacings. In step 104, the basic parameters of the observation system are obtained through the above analysis and demonstration, and the observation system for continuous wave field acquisition is designed by using these parameters; the same receiving point spacing is used in the vertical and horizontal directions, and the maximum shot offset in the vertical and horizontal directions is based on the results of the previous demonstration. The shot point in the template is set to 1 shot, and the vertical and horizontal shot point spacing is relatively large, and its specific size needs to be calculated according to the number of vertical and horizontal coverage times; In step 105, after the observation system is designed, the properties of the observation system are evaluated and analyzed, requiring that the coverage times of the observation system are evenly distributed and the offset properties meet the uniformity requirements.

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