A braided river type identification method

Abstract

The present invention relates to a braided river type identification method, and belongs to the field of seismic exploration technology. The method comprises: obtaining well logging data and a seismic attribute plane of a target area; determining the position of the braided river channel center, the channel edge, and the floodplain according to the well logging data of the target area; calibrating the seismic attribute plane using the position data, and determining the channel center seismic attribute range, the channel edge seismic attribute range, and the floodplain seismic attribute range; converting the seismic attribute plane into a sedimentary phase plane in combination with each seismic attribute range; determining the channel center width and channel edge width of each braided river on the sedimentary phase plane map; and determining the braided river type according to the channel center width and channel edge width of the braided river. The present invention quantitatively analyzes each seismic attribute range, enhances the objectivity of identifying different braided river types, reduces the risk of human subjectivity, and improves the accuracy of braided river type classification.

Description

Technical Field

[0001] The invention relates to a braided river type identification method and belongs to the technical field of seismic exploration. Background Art

[0002] The braided river channel is wide and shallow, sometimes separates and sometimes merges, frequently migrates, and wanders unsteadily. Although the riverbed is unstable, it is constrained by the paleo-geomorphology during the sedimentary period. The channel types of braided rivers include valley-enclosed braided rivers and open low-lying area deposited braided rivers. The center of the channel of the valley-enclosed braided river is concentrated in the low-lying terrain, and its width accounts for a small ratio of the riverbed width; the channel of the open low-lying area deposited braided river frequently migrates, has strong heterogeneity, and its channel center width accounts for a large ratio of the riverbed width. Efficient identification of braided river types is an essential foundation for oil exploration and development.

[0003] There are several methods for identifying braided river types in the prior art:

[0004] Method ①, based on the drilling data of the study area, the braided river type is determined by logging phase and macroscopic sedimentary phase. However, this method is highly practical in mining areas with high well density, but has weak ability to classify braided river types in exploration areas with low well density, making the braided river type identification inaccurate.

[0005] Method ②, based on the drilling and seismic data in the study area, the braided river type is comprehensively determined by logging phase, sedimentary phase and seismic attributes. This method realizes the identification of braided river types through qualitative analysis of seismic attributes. However, qualitative analysis is mainly based on personal sensory knowledge of geology and seismology. The accuracy of the results is highly dependent on personal experience. In addition, the braided river type is determined by personal experience, which is highly subjective, resulting in low accuracy in braided river type identification.

[0006] In summary, the identification results of existing braided river type identification methods are not accurate. Summary of the invention

[0007] The purpose of this application is to provide a braided river type identification method to solve the problem of inaccurate identification in existing methods.

[0008] To achieve the above objectives, the present application proposes a technical solution for a braided river type identification method, comprising the following steps:

[0009] 1) Obtain well logging data and seismic attribute planes in the target area; determine the location of the braided river channel center, channel edge and floodplain based on the well logging data in the target area;

[0010] 2) Using the location data obtained from the well logging data to calibrate the seismic attribute plane, determine the seismic attribute range of the river center, the river edge, and the floodplain in the seismic attribute plane;

[0011] 3) Convert the seismic attribute plane into the sedimentary phase plane in combination with the range of each seismic attribute;

[0012] 4) Determine the center width and edge width of each braided river on the sedimentary facies plane map;

[0013] 5) The type of braided river is determined based on the center width and edge width of the braided river channel. The types of braided rivers include valley-enclosed braided rivers and open low-lying area sedimentary braided rivers.

[0014] The beneficial effect of the technical solution of the braided river type identification method of the present invention is that the present invention uses logging data to quantitatively analyze the seismic attribute range corresponding to the river center, the seismic attribute range corresponding to the river edge, and the seismic attribute range corresponding to the floodplain, and obtains a specific seismic attribute range, and then converts the seismic attribute plane into a sedimentary phase plane in combination with each seismic attribute range, and then divides the river center, the river edge, and the floodplain in the sedimentary phase plane to obtain the width of the river center and the river edge, and finally realizes the identification of the braided river type according to the width of the river center and the river edge. The present invention quantitatively analyzes each seismic attribute range, enhances the objectivity of identifying different braided river types, reduces the risk of human subjectivity, and improves the accuracy of braided river type classification.

[0015] Furthermore, in order to solve the problem of dividing overlapping areas, in the step 2), if there are overlapping areas among the seismic attribute ranges of the river center, the river edge, and the floodplain, the boundary values ​​between the river center, the river edge, and the floodplain are determined in the overlapping areas to divide the river center, the river edge, and the floodplain.

[0016] Furthermore, the median value of the seismic attribute in the overlapping area is used as the boundary value between the river center, river edge, and floodplain.

[0017] Furthermore, in order to improve the accuracy of identification, in the step 5), the center width and the edge width of the braided river are summed to obtain the channel width, and the ratio of the center width to the channel width is calculated. The braided river with a ratio greater than or equal to a set threshold is a braided river deposited in an open low-lying area, and the braided river with a ratio less than the set threshold is a braided river sandwiched by a valley.

[0018] Furthermore, based on experience, the set threshold is 0.6.

[0019] Furthermore, the seismic attribute plane in step 1) is a seismic attribute plane that qualitatively characterizes the development of braided river sand bodies.

[0020] Furthermore, in order to accurately determine the range of each seismic attribute, the seismic attribute values ​​of the area where each well passing through the center of the river is located are counted in the calibrated seismic attribute plane, and the seismic attribute values ​​of each well passing through the center of the river are formed into a river center seismic attribute interval, and the river center seismic attribute interval is used as the river center seismic attribute range; the seismic attribute values ​​of the area where each well passing through the edge of the river is located are counted, and the seismic attribute values ​​of each well passing through the edge of the river are formed into a river edge seismic attribute interval, and the river edge seismic attribute interval is used as the river edge seismic attribute range; the seismic attribute values ​​of the area where each well passing through the floodplain is located are counted, and the seismic attribute values ​​of each well passing through the floodplain are formed into a floodplain seismic attribute interval, and the floodplain seismic attribute interval is used as the floodplain seismic attribute range.

[0021] Furthermore, in order to more intuitively determine the range of each earthquake attribute, a histogram is used to determine the earthquake attribute range of the river center, the river edge, and the floodplain.

[0022] Furthermore, the seismic attributes include amplitude, phase, or frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of the braided river type identification method of the present invention;

[0024] Figure 2 It is a plan view of the seismic amplitude attributes of the target area of ​​the present invention;

[0025] Figure 3 It is a schematic diagram of the sedimentary phase plane of the target area of ​​the present invention;

[0026] Figure 4 It is a plan view of the river channel types in the target area of ​​the present invention. DETAILED DESCRIPTION

[0027] Braided river type identification method embodiment:

[0028] The main idea of ​​the present invention is that, in order to improve the accuracy of braided river type identification, the present invention first uses logging data to determine the positions of the river center, the river edge and the floodplain, and then calibrates the seismic attribute plane according to the determined positions, quantitatively determines the seismic attribute range of the river center, the river edge and the floodplain in the seismic attribute plane, and converts the seismic attribute plane into a sedimentary phase plane in combination with each seismic attribute range, and finally obtains the river center width and river edge width of the braided river in the sedimentary phase plane to accurately identify the braided river type.

[0029] Specifically, the braided river type identification method is as follows: Figure 1 As shown, the following steps are included:

[0030] 1) Obtain well logging data and seismic attribute planes in the target area; determine the location of the braided river channel center, channel edge, and floodplain based on the well logging data in the target area.

[0031] Well logging data is data for each well. Whether a well passes through the center of the river, the edge of the river or the floodplain, its well logging data is different. Therefore, the well logging data can reflect whether the well passes through the center of the river, the edge of the river or the floodplain. Based on the location of the well, the location of part of the river center, the edge of the river and the floodplain can be determined. This location only represents that the area at this location is the center of the river, the edge of the river or the floodplain. If the number of wells is not enough, it can only reflect that the area at this location is the center of the river, the edge of the river or the floodplain, and cannot reflect the scope of the center of the river, the edge of the river and the floodplain.

[0032] Seismic attributes include amplitude, phase, frequency, or related parameters related to amplitude, phase, and frequency. There are many seismic attributes, which are not listed here one by one. The seismic attribute plane used here is a seismic attribute plane that qualitatively characterizes the development of braided river sand bodies. As other implementation methods, the seismic attribute plane can reflect the seismic attributes to realize the division of the river center, river edge, and floodplain according to the seismic attribute range. The present invention does not limit the specific form of the seismic attribute plane.

[0033] 2) Using the position data obtained in step 1), calibrate the seismic attribute plane, and then determine the seismic attribute range of the river center, the river edge, and the floodplain in the seismic attribute plane.

[0034] The process of determining the range of each seismic attribute includes:

[0035] In the calibrated seismic attribute plane, the seismic attribute value of the area where each well passing through the center of the river channel is located is counted, and the seismic attribute value of each well passing through the center of the river channel is used to form a river channel center seismic attribute interval using a histogram, and the river channel center seismic attribute interval is used as the river channel center seismic attribute range;

[0036] In the calibrated seismic attribute plane, the seismic attribute value of each well passing through the river channel is counted, and the seismic attribute value of each well passing through the river channel is used to form a river channel edge seismic attribute interval using a histogram, and the river channel edge seismic attribute interval is used as the river channel edge seismic attribute range;

[0037] The seismic attribute values ​​of each well passing through the floodplain are counted in the calibrated seismic attribute plane, and the seismic attribute values ​​of each well passing through the floodplain are used to form a floodplain seismic attribute interval using a histogram, and the floodplain seismic attribute interval is used as the floodplain seismic attribute range.

[0038] 3) If there are overlapping areas among the seismic attribute ranges of the river center, the river edge, and the floodplain, the boundary values ​​among the river center, the river edge, and the floodplain shall be determined in the overlapping areas to divide the river center, the river edge, and the floodplain.

[0039] The demarcation value here is the median value of the seismic attribute in the overlapping area. Taking the overlapping area between the center and the edge of the river as an example, the calculation process of the demarcation value is explained in detail:

[0040] Find the maximum and minimum values ​​of the seismic attributes in the overlapping area, and take the average of the maximum and minimum values ​​directly as the median of the seismic attribute.

[0041] Of course, as other implementation methods, the weights of the river center and the river edge in the overlapping area can also be determined by a specific attribute range, and then the boundary value between the river center and the river edge can be determined. The present invention does not limit the specific calculation method of the boundary value.

[0042] Of course, when the obtained seismic attribute ranges do not have overlapping areas, in order to ensure the continuity of the divided areas, the boundary values ​​of each seismic attribute range are taken as the median values ​​of the seismic attribute values ​​for different areas. For example: the seismic attribute range of the river center is (X1, X2), the seismic attribute range of the river edge is (X3, X4), and the seismic attribute range of the floodplain is (X5, X6); then (X2+X3) / 2 is used as the dividing line between the river center and the river edge, and (X4+X5) / 2 is used as the dividing line between the river edge and the floodplain.

[0043] At the same time, if there are fewer wells in the target area, resulting in fewer samples, you can also refer to empirical values, which include the minimum seismic attribute value in the center of the river channel and the maximum seismic attribute value in the floodplain to determine the demarcation value, and then redefine the range of each seismic attribute.

[0044] 4) Based on the range and demarcation values ​​of each seismic attribute, the seismic attribute plane is converted into a sedimentary phase plane.

[0045] 5) Determine the center width and edge width of each braided river on the sedimentary phase plane map, sum the center width and edge width to get the channel width, and calculate the braided river attribute index i.

[0046] The braided river attribute index is the ratio of the center width of the river channel to the width of the river channel, that is:

[0047] Braided river attribute index = river center width / river width.

[0048] 6) Braided river attribute index i is greater than or equal to the set threshold i n The braided river is a braided river deposited in an open low-lying area, and the braided river attribute index i is less than the set threshold i n The braided river is a braided river sandwiched between valleys.

[0049] Taking the identification of braided river channel types in a certain area as an example, the process of determining the threshold setting is explained:

[0050] The target study area covers 45km 2 , the number of wells that encountered the target layer is 13, and the whole area is fully covered by 3D seismic. The sedimentary facies of the target layer in the target study area is braided river, and the sedimentary subfacies are river channel and floodplain. The river channel types are river valley clamped braided river type and open low-lying area deposited braided river type. The width of the river channel of the river valley clamped braided river is between 0.5 km and 2 km, and its braided river attribute index is between 0.3 and 0.6; the width of the river channel of the braided river deposited in the open low-lying area is between 1.5 km and 4 km, and its braided river attribute index is between 0.7 and 0.9, so the threshold is set to 0.6.

[0051] Of course, the setting method of setting the thresholds for different target areas can also be set based on experience, and the present invention does not impose any limitation on this.

[0052] Taking the above target study area as an example, the braided river type identification method of the present invention is described in detail, and the specific steps are as follows:

[0053] 1. The logging phase of the Shihezi Group in each well is converted into river channel location data. The data types are braided river channel center, river channel edge, and floodplain. The data format is dat.

[0054] 2. In Figure 2 The seismic attribute values ​​corresponding to each well are extracted from the seismic amplitude attribute plane diagram shown in FIG. 1 . The specific values ​​are shown in Table 1 . The data format is dat.

[0055] Table 1 Seismic attribute values ​​for each well

[0056]

[0057] 3. Filter out the seismic data corresponding to the center of the river channel from the data in steps 1 and 2. The data format is dat.

[0058] 4. Use the data from step 3 to make a seismic attribute histogram. From the histogram, get the seismic attribute range corresponding to the river center, which is -14 to -35.

[0059] 5. Follow the method of steps 3 to 4 to obtain the earthquake attribute range of the river edge, which is -8 to -12.

[0060] 6. Follow the method of steps 3 to 4 to obtain the earthquake attribute range of the floodplain, which is -6 to 4.

[0061] 7. Due to the small number of sample points in this area, there is no overlapping area between the seismic attribute ranges of the river center and the river edge. The minimum seismic attribute value of the river center is the minimum value of the seismic attribute -44. The median value of -13, the maximum seismic attribute value of the river center obtained in step 3 and the minimum seismic attribute value -12 obtained in step 4, is taken as the maximum value of the seismic attribute range of the river center and also the minimum seismic attribute value of the river boundary. When the seismic attribute value is -13, it is the center of the river, that is, the seismic attribute x range of the river center is: -13≥x≥-42.

[0062] 8. Since there are fewer sample points in this area, there is no overlapping area between the river channel edge and the floodplain seismic attribute range. The median value of -7, which is the maximum seismic attribute value of the river channel edge obtained in step 4 and the minimum seismic attribute value of -6 obtained in step 5, is taken as the maximum value of the seismic attribute range of the river channel edge and also the minimum seismic attribute value of the floodplain. When the seismic attribute value is -7, it is the river channel edge, that is, the range of the seismic attribute x of the river channel edge is: -7≥x>-13.

[0063] 9. The maximum earthquake attribute value of the floodplain is the maximum value of the earthquake attribute 5, and the range of the earthquake attribute x of the floodplain is: 5≥x>-7.

[0064] 10. Use the seismic attribute boundary values ​​and ranges of the river center, river edge, and floodplain to convert the seismic attribute plane map into a sedimentary facies plane map, see Figure 3 shown.

[0065] 11. Count the center width of each braided river channel on the sedimentary phase plane map to obtain the center width data of each river channel in the dat format.

[0066] 12. Count the width of the edge of each braided river channel on the sedimentary phase plane map to obtain the center edge data of each channel in the dat format.

[0067] 13. Use the data obtained in steps 11 and 12 to calculate the width of each river channel in the format of dat.

[0068] 14. Based on the ratio of the center of the braided river channel to the channel width, the braided river attribute index i is obtained.

[0069] 15. Braided rivers are classified according to the braided river attribute index. A braided river with an attribute index less than 0.6 is a valley-sandwich braided river, and a braided river with an attribute index greater than or equal to 0.6 is a braided river deposited in an open low-lying area. Figure 4 shown.

[0070] In the above embodiment, the braided river attribute index is the ratio of the center width of the river channel to the width of the river channel, and this ratio is used as the basis for judging the type of the braided river. As other implementations, the ratio of the center width of the river channel to the edge width of the river channel can also be used as the basis for judging the type of the braided river. The present invention does not limit this.

[0071] In the above embodiment, in order to intuitively reflect the range of each earthquake attribute, a histogram is used to determine the range of each earthquake attribute. As other implementation methods, it can also be considered that the earthquake attribute range is determined by directly viewing the data, or the earthquake attribute range is determined by other statistical methods. The present invention does not limit this.

[0072] The present invention quantitatively determines the relationship between sedimentary phases and seismic attributes from the perspective of data analysis, and then determines the braided river type from the braided river attribute index, thereby enhancing the objectivity of identifying different braided river types and reducing the risk of human subjectivity.

Claims

1. A braided river type identification method, characterized in that: The following steps are involved: 1) Obtain well logging data and seismic attribute planes in the target area; determine the location of the braided river channel center, channel edge and floodplain based on the well logging data in the target area; 2) Using the location data obtained from the well logging data to calibrate the seismic attribute plane, determine the seismic attribute range of the river center, the river edge, and the floodplain in the seismic attribute plane; 3) Convert the seismic attribute plane into the sedimentary phase plane in combination with the range of each seismic attribute; 4) Determine the center width and edge width of each braided river on the sedimentary facies plane map; 5) The type of braided river is determined based on the center width and edge width of the braided river channel. The types of braided rivers include valley-enclosed braided rivers and open low-lying area sedimentary braided rivers.

2. The braided river type identification method according to claim 1, characterized in that: In the step 2), if there are overlapping areas among the seismic attribute ranges of the river center, the river edge, and the floodplain, the boundary values ​​among the river center, the river edge, and the floodplain are determined in the overlapping areas to divide the river center, the river edge, and the floodplain.

3. The braided river type identification method according to claim 2, characterized in that: The median value of the seismic attribute in the overlapping area is used as the boundary value between the river center, river edge, and floodplain.

4. The braided river type identification method according to claim 1, characterized in that: In the step 5), the channel width is obtained by summing the channel center width and channel edge width of the braided river, and the ratio of the channel center width to the channel width is calculated. A braided river with a ratio greater than or equal to a set threshold is a braided river deposited in an open low-lying area, and a braided river with a ratio less than the set threshold is a braided river sandwiched by a valley.

5. The braided river type identification method according to claim 4, characterized in that: The threshold value is set to 0.

6.

6. The braided river type identification method according to claim 1, characterized in that: The seismic attribute plane in step 1) is a seismic attribute plane that qualitatively characterizes the development of braided river sand bodies.

7. The braided river type identification method according to claim 1, characterized in that: In the calibrated seismic attribute plane, the seismic attribute values ​​of the area where each well passing through the center of the river is located are counted, and the seismic attribute values ​​of each well passing through the center of the river are formed into a river center seismic attribute interval, and the river center seismic attribute interval is used as the river center seismic attribute range; the seismic attribute values ​​of the area where each well passing through the edge of the river is located are counted, and the seismic attribute values ​​of each well passing through the edge of the river are formed into a river edge seismic attribute interval, and the river edge seismic attribute interval is used as the river edge seismic attribute range; the seismic attribute values ​​of the area where each well passing through the floodplain is located are counted, and the seismic attribute values ​​of each well passing through the floodplain are formed into a floodplain seismic attribute interval, and the floodplain seismic attribute interval is used as the floodplain seismic attribute range.

8. The braided river type identification method according to claim 7, characterized in that: The histogram is used to determine the range of seismic attributes in the center of the river channel, the edge of the river channel, and the floodplain.

9. The braided river type identification method according to claim 1, characterized in that: The seismic attributes include amplitude, phase, or frequency.

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