A method for suppressing interference noise between adjacent wells in fiber optic data

Abstract

This invention relates to the field of geophysical exploration seismic data processing technology. It discloses a method for suppressing noise interference from adjacent wells in fiber optic data processing. The method includes several steps: determining the data acquisition well, acquiring seismic data from the fiber optic well, identifying noise from adjacent wells in the fiber optic seismic data processing area, acquiring formation velocity in the exploration area, simulating noise curves from adjacent wells, and suppressing noise interference from adjacent wells. This invention can effectively recover seismic data information from fiber optic wells and improve the reliability of in-well seismic data.

Description

Technical Field

[0001] This invention relates to the field of geophysical exploration seismic data processing technology, specifically to a method for suppressing interference noise from adjacent wells in fiber optic data. Background Technology

[0002] In recent years, distributed optical fiber sensing (DAS) technology has matured, among which the fiber optic vertical seismic profiling method (DAS-VSP) has become an important means of acquiring well seismic data due to its advantages such as full-section coverage, high density, high efficiency, high temperature resistance, high pressure resistance, and low cost. Fiber optic well seismic technology can provide high-precision reservoir parameters, improve the fine description of reservoirs around wells, and provide dynamic monitoring capabilities for oil and gas reservoirs. A large amount of fiber optic well seismic data has been collected in multiple exploration areas both domestically and internationally. Unlike surface seismic data, surface noise such as surface waves has a smaller impact in well seismic data, but some unique noises exist, such as wellbore waves, casing waves, and adjacent well noise. Adjacent well noise is caused by vibrations generated during nearby drilling operations; it has high energy, and its apparent velocity is close to that of the effective wave. At the same time, the signal-to-noise ratio of current fiber optic recording data is relatively low, thus posing a significant challenge to well seismic data processing. To address the unique problem of adjacent well drilling interference in well seismic data, a convenient and practical fitting noise suppression method is needed. Summary of the Invention

[0003] The purpose of this invention is to provide a method for suppressing interference noise from adjacent wells in optical fiber data, which can effectively recover seismic data information in optical fiber wells and improve the reliability of seismic data in wells.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following solution:

[0005] A method for suppressing interference noise from adjacent wells in fiber optic data transmission includes at least two working wells. The working well used for seismic data acquisition in the fiber optic well is defined as the first working well. During the data acquisition process in the first working well, other adjacent working wells undergoing drilling operations are defined as the second working wells. The second working wells are equipped with drill bits. The method also includes the following steps:

[0006] Step S1: Collect seismic data from the fiber optic well in the first working well; the seismic data from the fiber optic well refers to standard seismic data that meets the requirements of industry standard SYT 5454-2017.

[0007] Step S2: Analyze the seismic data from the fiber optic well acquired in Step S1 with the drilling dynamics in the second working well to identify adjacent well noise data in the seismic data from the fiber optic well.

[0008] The drilling dynamics include the distance between the second working well and the first working well, the depth of the drill bit in the second working well, and the drilling rig operation time in the second working well;

[0009] Step S3: In the seismic data from the fiber optic well acquired in step S1, the first arrival of the downlink direct wave is picked out, and the formation velocity in the exploration area is calculated based on the first arrival.

[0010] Step S4: Using the formation velocity in the exploration area obtained in step S3, combined with the distance between the second working well and the first working well used to identify noise in step S2, and the depth of the drill bit in the second working well, calculate the noise curve of the adjacent well.

[0011] Step S5: Based on the adjacent well noise curve obtained in step S4, perform adjacent well noise suppression on the seismic data in the fiber optic wells in step S1 to obtain the processed data. Finally, restore the data according to the adjacent well noise curve to obtain the final seismic data after adjacent well noise suppression.

[0012] Furthermore, in the method of suppressing adjacent well noise in step S5, the seismic data in the fiber optic well obtained in step S1 is flattened along the adjacent well noise curve obtained in step S4, and then the flattened data is separated.

[0013] Furthermore, the data separation process employs multi-channel median filtering. Multi-channel median filtering is a commonly used method for processing borehole seismic data. When the noise from adjacent wells is close to the apparent velocity of the effective wavefield, this method is considered the optimal wavefield separation method.

[0014] Furthermore, the data flattening process employs a method of calibrating the seismic data in the fiber optic well with the corresponding noise data of the adjacent well after flattening the noise curve of the adjacent well.

[0015] Furthermore, the method for identifying seismic data in fiber optic wells in step S2 employs a method that combines preset empirical characteristics of noise wave fields with drilling dynamics for analysis.

[0016] Furthermore, in step S3, the method for picking the first arrival of the downlink direct wave employs a method that identifies and obtains the relationship between the time and depth of the first arrival wave in the well seismic data.

[0017] Furthermore, the velocity calculation method for the strata in the exploration area uses the depth difference of the first arrival wave divided by the time difference to obtain the velocity of the strata in the exploration area.

[0018] Furthermore, the method for calculating the adjacent well noise curve in step S4 can be either directly calculated using trigonometric functions or obtained through forward modeling using commonly used seismic processing software.

[0019] The beneficial effects of this invention are as follows:

[0020] By employing this noise suppression method, the seismic data information in fiber optic wells can be effectively recovered, thus improving the reliability of the seismic data in wells. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the observation system in this embodiment;

[0022] Figure 2 The data represents the seismic data collected from the first working well in Example 1. The horizontal axis represents the number of traces, which is dimensionless, with a depth interval of 10m between each trace. The vertical axis represents time, in milliseconds.

[0023] Figure 3 This is a schematic diagram of first arrival picking of well seismic data in Example 1, where the horizontal axis represents the number of traces (dimensionless), the depth interval between each trace is 10m, and the vertical axis represents time (ms).

[0024] Figure 4 This is a schematic diagram of the adjacent well noise curve for Example 1, where the horizontal axis represents the number of channels (dimensionless), the depth interval between each channel is 10m, and the vertical axis represents time (ms).

[0025] Figure 5 This is the data after suppressing noise from adjacent wells in Example 1, where the horizontal axis represents the number of channels (dimensionless), the depth interval between channels is 10m, and the vertical axis represents time (ms).

[0026] Figure 6 This is a logical relationship diagram of the method steps in this embodiment.

[0027] The attached diagrams are as follows: 1. First working well; 2. Second working well; 3. Cable car; 4. Optical fiber; 5. Drill bit; 6. Derrick; 7. Noise data of adjacent wells; 8. Downward direct wave; 9. Upward direct wave; 10. Initial arrival of downward direct wave; 11. Noise curve of adjacent wells. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0029] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "longitudinal," "lateral," "horizontal," "inner," "outer," "front," "rear," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0030] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "have," "install," "connect," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] Example 1

[0032] A method for suppressing interference noise between adjacent wells in fiber optic data, such as Figure 6 As shown, the specific steps include determining the data acquisition well, acquiring seismic data from fiber optic wells, identifying adjacent well noise in fiber optic seismic data, acquiring formation velocity in the exploration area, simulating adjacent well noise curves, and suppressing adjacent well noise interference. Figure 1 As shown, the system includes two working wells. The working well used for seismic data acquisition in the fiber optic cable 4 is defined as the first working well 1. The fiber optic cable 4 is deployed in the first working well 1 via a cable car 3 for data acquisition. During the data acquisition process in the first working well 1, the other working well adjacent to it that is used for drilling is defined as the second working well 2. The second working well 2 is equipped with a drill bit 5, and a derrick 6 connected to the drill bit 5 is installed above the second working well 2. The system also includes the following steps:

[0033] Step S1: Acquire seismic data from the fiber optic well in the first working well 1. The seismic data from the fiber optic well is as follows: Figure 2 As shown, the data includes adjacent well noise data, downward traveling wave, and upward traveling wave. The stronger in-phase axis between 0ms and 500ms in the figure is the downward traveling wave, and what is seen above it is adjacent well noise. The seismic data in the fiber optic well refers to standard seismic data that meets the requirements of industry standard SYT5454-2017.

[0034] Step S2: Analyze the seismic data from the fiber optic well acquired in Step S1 with the drilling dynamics in the second working well 2 to identify adjacent well noise data in the seismic data from the fiber optic well, such as... Figure 2 As shown, the noise from adjacent wells exhibits a distinct convex and undulating pattern, which is clearly identifiable.

[0035] The noise from adjacent wells or the interference noise from adjacent wells is caused by activities such as drilling in adjacent wells. It has a significant impact on the signal-to-noise ratio of the data collected in the well. Before the straight wave (effective wave) is delivered, strong and regular background noise can be seen.

[0036] The drilling dynamics include the distance between the second working well 2 and the first working well 1, the depth of the drill bit 5 in the second working well 2, and the drilling rig operation time of the second working well 2;

[0037] Step S3: In the fiber optic borehole seismic data acquired in step S1, the first arrival of the downlink direct wave is picked. The first arrival of the downlink direct wave in the borehole seismic data is picked as follows: Figure 3 As shown, the formation velocity in the exploration area is calculated based on the first arrival of the downlink direct wave;

[0038] Step S4: Using the formation velocity in the exploration area obtained in Step S3, combined with the distance between the second working well 2 and the first working well 1 used for noise identification in Step S2, and the depth of the drill bit 5 in the second working well 2, the adjacent well noise curve is calculated using time-distance curve picking or forward simulation methods. The adjacent well noise curve is shown below. Figure 4 As shown;

[0039] The aforementioned time-distance curve picking refers to obtaining the noise curve of adjacent wells by visually tracking the same phase axis for some data with strong noise from adjacent wells. This curve consists of two sets of data: time and distance (depth).

[0040] The process of forward modeling the noise curve of adjacent wells refers to the process of establishing a geological model based on the previous step velocity and then performing forward modeling using commonly used seismic processing software.

[0041] The time-distance curve picking and forward modeling methods mentioned above are both existing technologies.

[0042] Step S5: Based on the adjacent well noise curve obtained in Step S4, perform adjacent well noise suppression on the seismic data in the fiber optic wells from Step S1 to obtain processed data. Finally, restore the data according to the adjacent well noise curve to obtain the final adjacent well noise-suppressed seismic data. The adjacent well noise-suppressed data is shown below. Figure 5 As shown.

[0043] The method for suppressing adjacent well noise in step S5 involves flattening the seismic data in the fiber optic wells obtained in step S1 along the adjacent well noise curve obtained in step S4, and then performing data separation processing on the flattened data.

[0044] The data separation process employs multi-channel median filtering. Multi-channel median filtering is a commonly used method for processing borehole seismic data. When the noise from adjacent wells is close to the apparent velocity of the effective wavefield, this method is considered the optimal wavefield separation method.

[0045] The data flattening process employs a method of calibrating the seismic data in the fiber optic well with the corresponding noise data of the adjacent well after flattening the noise curve of the adjacent well.

[0046] The method for identifying seismic data in fiber optic wells in step S2 employs an analysis that combines preset empirical characteristics of the noise wave field with drilling dynamics. The preset empirical characteristics of the noise wave field are as follows: Figure 5 As shown, it has a smooth, flat surface.

[0047] The method for picking up the first arrival of the downlink direct wave in step S3 adopts a method of identifying and obtaining the relationship between the time and depth of the first arrival wave in the well seismic data.

[0048] The velocity calculation method for the strata in the exploration area is to divide the depth difference of the first arrival wave by the time difference to obtain the velocity of the strata in the exploration area.

[0049] The method for calculating the adjacent well noise curve in step S4 can be either by directly calculating using trigonometric functions or by using forward modeling with commonly used seismic processing software.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for suppressing adjacent well interference noise in fiber optic data transmission, characterized in that: It includes at least two working wells, wherein the working well for seismic data acquisition in the fiber optic (4) well is defined as the first working well (1), and other working wells adjacent to it that are conducting drilling work during the data acquisition process of the first working well (1) are defined as the second working well (2), and also includes the following steps: Step S1: Collect seismic data from the optical fiber (4) in the first working well (1); Step S2: Analyze the seismic data in the fiber optic (4) well collected in step S1 with the drilling dynamics in the second working well (2) to identify the adjacent well noise data (7) in the seismic data in the fiber optic (4) well. The drilling dynamics include the distance between the second working well (2) and the first working well (1), the depth of the drill bit (5) in the second working well (2), and the drilling rig operation time of the second working well (2); Step S3: In the seismic data of the fiber optic (4) well obtained in step S1, pick out the first arrival of the downlink direct wave (10) and calculate the formation velocity of the exploration area based on the first arrival; Step S4: Using the formation velocity of the exploration area obtained in step S3, combined with the distance between the second working well (2) and the first working well (1) used to identify noise in step S2, and the depth of the drill bit (5) in the second working well (2), the noise curve of the adjacent well (11) is calculated. Step S5: According to the adjacent well noise curve (11) obtained in step S4, the adjacent well noise of the seismic data in the fiber (4) well in step S1 is suppressed to obtain the processed data. Finally, the data is restored according to the adjacent well noise curve (11) to obtain the final adjacent well noise suppressed seismic data.

2. The method for suppressing inter-well interference noise in fiber optic data according to claim 1, characterized in that: The method for suppressing adjacent well noise in step S5 involves flattening the seismic data in the fiber optic (4) well obtained in step S1 along the adjacent well noise curve (11) obtained in step S4, and then performing data separation processing on the flattened data.

3. The method for suppressing inter-well interference noise in fiber optic data according to claim 2, characterized in that: The data separation process is performed using a multi-channel median filtering method.

4. The method for suppressing adjacent well interference noise in optical fiber data according to claim 2, characterized in that: The data flattening process employs a method of calibrating the seismic data in the fiber optic (4) well with the corresponding noise data (7) of the adjacent well after flattening the adjacent well noise curve (11).

5. The method for suppressing inter-well interference noise in fiber optic data according to claim 1, characterized in that: The method for identifying seismic data in the fiber optic (4) well in step S2 adopts a method that combines the preset empirical characteristics of the noise wave field with the drilling dynamics for analysis.

6. The method for suppressing adjacent well interference noise in optical fiber data according to claim 1, characterized in that: The method for picking the first arrival of the downlink direct wave (10) in step S3 adopts a method of identifying and obtaining the relationship between the time and depth of the first arrival wave in the well seismic data.

7. The method for suppressing inter-well interference noise in fiber optic data according to claim 5, characterized in that: The velocity calculation method for the strata in the exploration area is to divide the depth difference of the first arrival wave by the time difference to obtain the velocity of the strata in the exploration area.

8. The method for suppressing inter-well interference noise in fiber optic data according to claim 1, characterized in that: The method for calculating the adjacent well noise curve (11) in step S4 can be obtained by directly calculating it using trigonometric functions or by using commonly used seismic processing software for forward modeling.

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