A method and system for evaluating the uniformity of azimuthal coverage

Abstract

The application provides a method and system for evaluating uniformity of coverage times azimuth angle distribution, and belongs to the field of three-dimensional seismic acquisition observation system design and optimization. The method comprises the following steps: step 1: collecting offset and azimuth angle data of effective coverage of a bin; step 2: calculating a vector opening angle of offset and azimuth angle, and an average value, a standard deviation and a variation coefficient; and step 3: evaluating the uniformity of coverage times azimuth angle distribution by using the vector opening angle of offset and azimuth angle and the variation coefficient. The application is suitable for theoretical research and field production of three-dimensional seismic acquisition observation system design. The application provides a method for quantitative evaluation and optimization of a three-dimensional observation system, has the advantages of being scientific, intuitive and having clear physical meaning, and is suitable for field production and theoretical research, has important significance for quantification and scientification of observation system design, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of three-dimensional seismic acquisition observation system design and optimization, and particularly relates to a method and system for evaluating azimuth distribution uniformity of fold. BACKGROUND

[0002] Application of reflection seismic method to obtain subsurface geological structure and reservoir oil and gas bearing property is one of the most important means in oil and gas exploration process, including three sub-processes of seismic acquisition, seismic data processing and seismic interpretation. In this process, objective observation of deep geological structure and predictive description of reservoir will be affected by many factors, mainly from four aspects:

[0003] Firstly, the influence of near-surface structure on wave propagation, complex near-surface structure leads to complex wave field, and reduces signal-to-noise ratio of seismic acquisition data;

[0004] Secondly, the influence of complex degree of subsurface structure on velocity estimation and migration imaging precision under the condition of low signal-to-noise ratio data;

[0005] Thirdly, the influence of change of reservoir oil and gas bearing property on oil and gas prediction accuracy;

[0006] Finally, effective economic investment, etc.

[0007] These influences are focused on seismic acquisition work to a great extent, especially seismic acquisition observation system design research. On the one hand, compared with seismic data processing and seismic interpretation, seismic acquisition has the characteristics of high cost and non-repeatability; on the other hand, the goal of observation system design and optimization is to obtain conditions and potential for eliminating or improving the complexity of seismic geological conditions, and effectively reduce the cost of seismic acquisition.

[0008] With the deepening of oil and gas exploration and the development and maturity of three-dimensional seismic exploration technology, high-density-super-high-density three-dimensional seismic exploration technology has become one of the important technical countermeasures to solve the complex problems faced by current oil and gas, and has played an important role in subtle oil and gas reservoirs, complex structure oil and gas reservoirs, super-deep fracture-cave or carbonate rock oil and gas reservoirs, and tight sandstone oil and gas reservoirs, unconventional oil and gas reservoirs, etc. Especially in solving the problem of seismic imaging under the condition of complex surface and complex structure seismic geology, the effect is more remarkable.

[0009] There are many key parameters in 3D geometry design, such as bin size, fold, maximum offset, receiver line interval, shot point line interval, etc. Bin size is determined by seismic resolution, fold is determined by signal-to-noise ratio of seismic data and desired signal-to-noise ratio of profile, maximum offset is determined by velocity analysis requirement, receiver line interval and shot point line interval are determined by bin grid, etc. The interval of receiver line and shot point line is related to bin grid and fold.

[0010] For a known 3D model, given bin size and fold, the interval of receiver line and shot point line affects the length and width of layout sheet, and results in many different 3D geometries.

[0011] Two key parameters in quantitative evaluation of geometry are: 1) fold or energy or signal-to-noise ratio of target layer; 2) azimuthal distribution of fold.

[0012] Azimuthal distribution of fold is very important in geometry design and evaluation: 1) from linear stack to area stack, the azimuthal distribution of fold can be understood as multi-azimuth area stack, the more uniform the distribution of receiver points in a certain area, the better the effect of stack, and the more uniform the distribution of fold in offset and azimuth. 2) from 2D geometry to 3D geometry, the azimuthal distribution of fold is the most important change in bin attribute, and the final result is to improve seismic imaging, the same change is also in narrow-azimuth 3D geometry to wide-azimuth 3D geometry. The basic reason is that the uniform distribution of fold in azimuth is beneficial to more accurate noise estimation and suppression, and improves spatial imaging accuracy. The evaluation method of the uniform distribution of fold in azimuth is mostly graphical comparison or qualitative description, and there is no quantitative description method.

[0013] The uniform distribution of fold in azimuth can be understood as the consistency of the angle between two different offset folds in a bin, and any fold in a bin can be regarded as a vector described by offset and azimuth. The angle and coefficient of variation of offset-azimuth vector in a bin can be calculated to quantitatively evaluate the uniform distribution of fold in azimuth, and the result is more accurate and intuitive compared with the conventional offset-azimuth rose diagram in geometry design. SUMMARY

[0014] The present application aims at solving the problems in the prior art, and provides a method and system for evaluating the uniformity of the azimuth distribution of the coverage times, so as to provide a quantitative description method for the design, evaluation and optimization of the three-dimensional observation system, and to meet the quantitative evaluation requirements of the azimuth uniformity of the bin coverage times in the seismic acquisition design.

[0015] The present application is realized by the following technical solutions.

[0016] In a first aspect, the present application provides a method for evaluating the uniformity of the azimuth distribution of the coverage times, which comprises the following steps:

[0017] Step 1: collecting the offset and azimuth data of the effective coverage of the bin;

[0018] Step 2: calculating the opening angle, average value, standard deviation and variation coefficient of the offset-azimuth vector;

[0019] Step 3: evaluating the uniformity of the azimuth distribution of the coverage times by using the opening angle and variation coefficient of the offset-azimuth vector.

[0020] In a further improvement of the present application,

[0021] The operation of step 1 comprises:

[0022] The azimuth of the shot-receiver pair is calculated by using the geodetic coordinates of the shot point and the receiver point, and the azimuth of all the effective coverage shot-receiver pairs of the bin is obtained.

[0023] In a further improvement of the present application,

[0024] The operation of step 1 comprises:

[0025] The offset and azimuth data are obtained by downloading the three-dimensional observation system design software.

[0026] In a further improvement of the present application,

[0027] The opening angle θ of the offset-azimuth vector is calculated by using the following formula in step 2: i :

[0028]

[0029] wherein, is the offset and azimuth function of the shot-receiver pair SR i , and the shot-receiver pair SR i is composed of the shot point S i and the receiver point R i .

[0030] In a further improvement of the present application,

[0031] The step 2 obtains the average value by calculation using the following formula

[0032]

[0033] Wherein, N is the number of coverages.

[0034] A further improvement of the present application is that:

[0035] The step 2 obtains the standard deviation σ by calculation using the following formula:

[0036]

[0037] A further improvement of the present application is that:

[0038] The step 2 obtains the coefficient of variation v by calculation using the following formula:

[0039]

[0040] A further improvement of the present application is that:

[0041] The step 3 includes:

[0042] If the azimuth angle vector opening angles of the offset distances are the same, the smaller the coefficient of variation is, the more uniform the azimuth angle distribution is;

[0043] If the azimuth angle vector opening angles of the offset distances are different, the smaller the azimuth angle vector opening angle of the offset distance is, the more uniform the azimuth angle distribution is.

[0044] The second aspect of the present application provides a system for evaluating the uniformity of the azimuth angle distribution of the number of coverages, which comprises:

[0045] A data acquisition unit for acquiring the offset distance and azimuth angle data of the effective coverage of the bin;

[0046] A calculation unit connected with the data acquisition unit, for calculating the azimuth angle vector opening angle of the offset distance and the average value, the standard deviation and the coefficient of variation;

[0047] An evaluation unit connected with the calculation unit, for evaluating the uniformity of the azimuth angle distribution of the number of coverages by using the azimuth angle vector opening angle of the offset distance and the coefficient of variation.

[0048] The third aspect of the present application provides a computer readable storage medium, which stores at least one computer executable program, and the at least one program makes the computer execute the steps in the method for evaluating the uniformity of the azimuth angle distribution of the number of coverages when executed by the computer.

[0049] Compared with the prior art, the present application has the following beneficial effects:

[0050] This invention is applicable to theoretical research and field production of three-dimensional seismic acquisition and observation systems. It provides a method for quantitative evaluation and optimization of three-dimensional observation systems, which has the advantages of being scientific, intuitive, and having clear physical significance. It is suitable for field production and theoretical research, and is of great significance for the quantification and scientification of observation system design, with broad application prospects. Attached Figure Description

[0051] Figure 1-1 Schematic diagram of the gun-receiver pair vector;

[0052] Figure 1-2 Schematic diagram of surface element vector set;

[0053] Figure 2 A schematic diagram of a triangle or polygon formed by the offset-azimuth vector and the boundary of the surface element;

[0054] Figure 3 A schematic diagram of the vector distribution of a simulated surface element shot-receiver pair.

[0055] Figure 4-1 Schematic diagram of the surface element shot-receiver pair vector distribution of the simulated observation system 1;

[0056] Figure 4-2 Schematic diagram of the surface element shot-receiver pair vector distribution of the simulated observation system 2;

[0057] Figure 5 A flowchart illustrating the steps of the method of this invention. Detailed Implementation

[0058] The present invention will now be described in further detail with reference to the accompanying drawings:

[0059] The principle of this invention is as follows:

[0060] 1. Basic concept of the angle of the (offset distance - azimuth) vector of the shot-receiver pair

[0061] Assume the gun and the checkpoint are S respectively. i (Xsi, Ysi), R i (Xri, Yri), where the center point of the element is M(Xm, Ym). Any shot-receiver pair SR i It constitutes the surface element M. For a given element M, the effective coverage count for a shot-receiver pair SR is calculated using the coordinates of M(Xm, Ym) as the center. i The contribution of the number of times the element is covered is the offset and azimuth function, which can be represented by a vector. Description, such as Figure 1-1 As shown.

[0062] For a surface element M with N coverage times, it can be viewed as a set consisting of many shot-receiver pairs, such asFigure 1-2 is denoted as:

[0063]

[0064] The angle between two adjacent shot-receiver vectors is defined as the opening angle of the shot-receiver vector. For convenience, the opening angle between and is denoted as θ1, and is denoted as θ2, …, and According to the vector product formula, the opening angles of two adjacent vectors satisfy:

[0065]

[0066]

[0067] where i = 1, 2, …, N, and i + 1 = 1 when i = N.

[0068] 2. Azimuthal uniformity estimation method of bin coverage times

[0069] It can be seen from Figure 1-2 that the uniformity of the azimuthal distribution of coverage times depends on the variation of the angle between two adjacent vectors, which can be represented by the average value of the angle between two adjacent vectors and the overall variance σ 2 Description, there are:

[0070]

[0071]

[0072] It can be seen from Figure 1-2 that the sum of the opening angles of two adjacent vectors forms a circle with the midpoint of the bin M, so:

[0073]

[0074] or

[0075]

[0076] where N is the coverage times, and are the angle and radian units, respectively.

[0077] Equation (6) or equation (7) is defined as the angular tensor of coverage times, and the reciprocal of its physical meaning can be understood as the coverage times of unit angle or radian in the bin.

[0078] 3. Extension algorithm for azimuthal uniformity estimation

[0079] The vector Two vectors intersecting with the bin boundary at an angle of θ1 A triangle or polygon is constructed with the bin boundary, defined as M s1 , M s2 , …, With M si , the average of the polygon area formed by the adjacent two vectors and the bin boundary And the total variance Describes the change of the angle between the adjacent two vectors, and its physical meaning can be expressed as the effective area of the first azimuth angle coverage control, as shown in Figure 2 .

[0080] Figure 2 Offset-distance-azimuth vector and bin boundary triangle or polygon schematic diagram

[0081] Similarly, for the bin M with N times of coverage, it can be regarded as a set of polygons composed of many adjacent two vector and bin boundaries, denoted as:

[0082]

[0083] Where: i = 1, 2, …, N, when i = N, i + 1 = 1.

[0084] The average value of the polygon area formed by the adjacent two vectors and the bin boundary Is:

[0085]

[0086] As can be seen from Figure 2 , is equal to the size of the bin M B , that is:

[0087]

[0088]

[0089] Where: R I , the receiving trace interval; S I , the shot point interval.

[0090] The reciprocal of formula (10) is the industry-defined shot density, which represents the average coverage times per unit area in its physical meaning.

[0091] The total variance of the polygon area formed by the adjacent two vectors and the bin boundary Is:

[0092]

[0093] Theoretically, the difference of the influence of the number of coverage on the bin is reflected.

[0094] For the convenience of calculation, the offset-azimuth vector can be simply considered as intersecting with a circle with the center point M(Xm, Ym) of the bin as the origin and the length of the bin as the radius (for square bin, the radius is half of the offset; for non-square bin, the radius is the offset and the number of coverage is the sum of the single bin), that is,

[0095]

[0096]

[0097] Formula 14 has the same meaning as formula 10.

[0098] As can be seen from the above, the result of the uniformity estimation of the azimuth distribution has practical physical meaning.

[0099] For the change of the uniformity of the number of coverage, the coefficient of variation can be used, that is,

[0100]

[0101] In the formula, The opening angle of the offset-azimuth vector, X, the average value of the opening angle of the offset-azimuth vector, for example, if the angle average value is used, the formula is as follows:

[0102]

[0103] Figure 3 In order to simulate the distribution of the vector of the 36 times of coverage, a bin with a size of 20x20 and a center point coordinate of (10, 10) is used, and the coordinates of the shot-receiver pair relative to the center point of the bin are shown in Table 1, which shows the calculation results of the relative coordinates of the shot-receiver pair and the opening angle of the vector of the simulation of the observation system 1.

[0104] The calculation results show that when the number of bin coverage is 36 and the effective opening angle of the bin is 10°, the standard deviations of the radian, angle and area are 0.0055, 18.057 and 13.751 respectively, and the coefficient of variation is 43.096%.

[0105] The above analysis results are applied to the comparison of three-dimensional observation systems.

[0106] When the average value of the vector angle is smaller, it means that the number of coverage is higher and the observation system is relatively better. When the standard deviation is smaller, the azimuth distribution of the number of coverage is more uniform and the uniformity of the observation system is better.

[0107] The relative coordinates of the two observation system bin and the calculation results are shown in Table 1 and Table 2, Figure 4-1 and Figure 4-2 The distribution of offset-azimuth vector of the two observation system bins, the observation system bin of the simulation design has 36 times of coverage, and has the same coverage times azimuth tensor. From Figure 4-1 and Figure 4-2 It can be seen that the length of the vector represents the size of the offset, and it can be seen that the observation system 2 has a larger lateral offset than the observation system 1, and the distribution of the coverage times of the middle offset is relatively uniform, and the visual coverage times azimuth distribution is also relatively uniform. In fact, the observation system 2 has a larger standard deviation and coefficient of variation than the observation system 1, the standard deviation of the radian, angle and area of the observation system 2 is 0.0083, 27.1562 and 20.6926, and the coefficient of variation is 52.8661%, which is higher than that of the observation system 1. According to the analysis of the difference between the two, it is not difficult to find that the observation system 2 has almost uniform azimuth coverage times, which leads to uneven distribution of coverage times azimuth.

[0108]

[0109] Table 1

[0110]

[0111] Table 2

[0112] The embodiment of the method for evaluating the uniformity of the coverage times azimuth distribution of the application is as follows:

[0113]

Example one

[0114] As Figure 5 shown, the method of the application comprises:

[0115] Step 1: Collect the offset and azimuth data of the effective coverage bin:

[0116] The data source can directly calculate the azimuth of the shot-receiver pair by calculating the azimuth of the shot-receiver pair according to the conventional seismic measurement formula of the azimuth of the shot-receiver pair according to the geodetic coordinates of the shot and the receiver, and obtaining the azimuth of all effective coverage shot-receiver pairs of the bin. It can also be obtained by downloading a three-dimensional observation system design software. In the application of three-dimensional observation system evaluation and optimization, for the multiple three-dimensional observation systems to be determined, the azimuth of the shot-receiver pair of the same full coverage range (or bin, or sub-area) of each three-dimensional observation system should be calculated.

[0117] The calculated or downloaded shot-receiver azimuth data of the bin is arranged in NESW direction.

[0118] In step 1, the azimuth and attribute analysis of the surface element designed by the three-dimensional observation system design software is downloaded to obtain the highest efficiency. The downloaded data should include the coverage frequency and azimuth angle distribution data of all surface elements in a sub-area.

[0119] In step 2, the vector opening angle and the average value, standard deviation and coefficient of variation are calculated. According to the method provided by the present application, the vector opening angle and the average value, standard deviation and coefficient of variation of the vector opening angle are calculated respectively.

[0120] The offset-azimuth vector opening angle θ is calculated by the following formula i :

[0121]

[0122] Wherein, is the offset and azimuth angle function of the shot-receiver pair SR i , and the shot-receiver pair SR i is composed of the shot point S i (Xsi, Ysi) and the receiver point R i (Xri, Yri).

[0123] The average value is calculated by the following formula:

[0124]

[0125] Wherein, N is the coverage frequency;

[0126] The standard deviation is calculated by the following formula:

[0127]

[0128] The coefficient of variation is calculated by the following formula:

[0129]

[0130] The above is calculated in degrees. Similarly, radians and area can also be used to obtain the average value, standard deviation, coefficient of variation, etc.

[0131] In step 2, the average value, standard deviation and coefficient of variation of the shot-receiver pair opening angle are calculated in degrees, radians or area units, which have similar physical meanings and can obtain the same conclusions. The calculation in degrees is relatively simple.

[0132] Step 3: analysis and evaluation.

[0133] General principle: the same vector opening angle indicates the same coverage frequency, and the smaller the coefficient of variation, the more uniform the azimuth angle distribution;

[0134] Different vector opening angles indicate different coverage frequencies, and the smaller the opening angle, the higher the coverage frequency, and the more uniform the azimuth angle distribution.

[0135] In step 3, the variation coefficient is used to describe the uniformity of the azimuth distribution of the observation system for a given three-dimensional observation system, and the greater the variation coefficient, the more uneven the azimuth distribution of the coverage times. When the method is applied to the comparison and evaluation of the observation system, the average angle and the variation coefficient of the vector of the shot-receiver pair of a subarea and all the surface elements of the subarea are calculated, the average angle and the variation coefficient of the subarea and the surface element are counted, and the uniformity of the azimuth distribution of the coverage times of the observation system is evaluated according to the size of the variation coefficient. When the method is applied to the optimization of the observation system, the average angle of the vector of the shot-receiver pair of a subarea and all the surface elements of the subarea is calculated, the average angle and the variation coefficient of the subarea and the surface element are counted, and the optimization of the observation system is realized by adjusting the shot line distance and changing the azimuth distribution of the subarea or the surface element under the condition of maintaining a certain range of coverage times.

[0136] The application provides an evaluation method for the uniformity of the azimuth distribution of the effective coverage of a three-dimensional surface element, which has the advantages of clear physical meaning, scientific and intuitive data-based description compared with graphic comparison or qualitative evaluation, and is suitable for field production and theoretical research.

[0137] The application also provides a system for evaluating the uniformity of the azimuth distribution of the coverage times, and the implementation of the system is as follows:

[0138] Example 2

[0139] The system comprises:

[0140] A data acquisition unit is configured to acquire offset and azimuth data of the effective coverage of the surface element.

[0141] A calculation unit is connected with the data acquisition unit and is configured to calculate the vector angle, the average value, the standard deviation and the variation coefficient of the offset and azimuth.

[0142] An evaluation unit is connected with the calculation unit and is configured to evaluate the uniformity of the azimuth distribution of the coverage times by using the vector angle and the variation coefficient of the offset and azimuth.

[0143] The application also provides a computer-readable storage medium, and the implementation of the computer-readable storage medium is as follows:

[0144] Example 3

[0145] The computer readable storage medium stores at least one program executable by the computer, and the at least one program, when executed by the computer, causes the computer to perform the steps in the method for evaluating the azimuth angle distribution uniformity of the coverage times.

[0146] The application is based on the statistical analysis principle of the vector opening angle. Since the reciprocal of the vector opening angle in the unit of area has the same physical meaning as the unit area coverage density, the statistical value of the vector opening angle can objectively reflect the change of the azimuth angle attribute parameter of the surface element. In theory, the size of the vector opening angle represents the level of the effective coverage times; the size of the coefficient of variation of the vector opening angle represents the change of the azimuth angle distribution uniformity of the coverage times.

[0147] Finally, it should be noted that the above technical solutions are only one embodiment of the application, and for those skilled in the art, on the basis of the application disclosed application method and principle, various types of improvements or modifications can be easily made, and are not limited to the method described in the above embodiment of the application, therefore, the above described method is only preferred, and does not have the meaning of limitation.

Claims

1. A method of evaluating the uniformity of the azimuthal distribution of the number of coverages, characterized in that: The method comprises: Step 1: collecting offset and azimuth data of effective coverage of a bin; Step 2: Calculate the average value, standard deviation and coefficient of variation of the azimuth angle vector opening angle of offset distance; the azimuth angle vector opening angle of offset distance is calculated by the following formula : wherein, is the offset and azimuth function of the shot-receiver pair SR i is the offset and azimuth function of the shot-receiver pair SR i is composed of a shot point S i and a receiver point R i , i = 1，2，…，N when i=N , i+1=1, N is the number of coverages; Step 3: evaluating uniformity of azimuth distribution of coverage times by using vector opening angle of offset and azimuth, and coefficient of variation, comprising: If the vector opening angles of offset and azimuth are the same, the smaller the coefficient of variation is, the more uniform the azimuth distribution is; If the vector opening angles of offset and azimuth are different, the smaller the vector opening angle of offset and azimuth is, the more uniform the azimuth distribution is.

2. The method of evaluating the uniformity of the azimuthal distribution of the number of coverages according to claim 1, characterized in that: The operation of step 1 comprises: Azimuth of shot and receiver is obtained by calculating geodetic coordinates of shot and receiver, and azimuth of all effective coverage shot-receiver pairs of a bin is obtained.

3. The method of evaluating the azimuthal uniformity of the number of coverages according to claim 1, characterized in that: The operation of step 1 comprises: Offset and azimuth data are obtained by downloading from 3D observation system design software.

4. The method of evaluating the azimuthal uniformity of coverage according to claim 1, wherein: The step 2 uses the following formula to calculate the average value : wherein N is the number of coverages.

5. The method of evaluating the azimuthal uniformity of the number of coverages according to claim 4, characterized in that: The step 2 utilizes the following formula to obtain the standard variance : 。 6. The method of evaluating the azimuthal uniformity of the number of coverages according to claim 5, characterized in that: The step 2 utilizes the following formula to obtain the coefficient of variation v : 。 7. A system for evaluating the uniformity of azimuthal coverage, characterized in that: The system comprises: A data acquisition unit for collecting offset and azimuth data of effective coverage of a bin; A computing unit connected with the data acquisition unit, used for calculating the average value, standard deviation and variation coefficient of the opening angle of the vector of the offset distance azimuth angle; the opening angle of the vector of the offset distance azimuth angle is calculated by the following formula : wherein, is the offset and azimuth function of the shot-receiver pair SR i is the offset and azimuth function of the shot-receiver pair SR i consists of a shot point S i and a receiver point R i , i = 1，2，…，N when i=N , i+1=1, N is the number of coverages; An evaluation unit connected with the calculation unit, for evaluating uniformity of azimuth distribution of coverage times by using vector opening angle of offset and azimuth, and coefficient of variation, comprising: If the vector opening angles of offset and azimuth are the same, the smaller the coefficient of variation is, the more uniform the azimuth distribution is; If the vector opening angles of offset and azimuth are different, the smaller the vector opening angle of offset and azimuth is, the more uniform the azimuth distribution is.

8. A computer-readable storage medium, characterized in that: The computer readable storage medium stores at least one computer executable program, and the at least one program is executed by the computer to make the computer execute steps in the method for evaluating uniformity of azimuth distribution of coverage times according to any one of claims 1-6.

Images