Buried pipeline depth positioning method based on two-dimensional body magnetic anomaly characteristics

Abstract

The invention relates to a buried pipeline depth positioning method based on a two-degree body magnetic anomaly characteristic, and the method employs a three-component magnetic sensor for measurement, and can achieve the determination of the depth of a buried pipeline through a single measurement line on the premise of determining the azimuth angle of the pipeline. A buried pipeline is regarded as a two-dimensional body, a deviation ratio can be determined by solving a gradient value of a horizontal component magnetic anomaly curve of a single measuring line, presetting a pipeline burial depth value and calculating a magnetic dip angle, a magnetic declination angle and a pipeline azimuth angle according to measurement data, and the measurement accuracy is improved. After the distance between the horizontal coordinates corresponding to the maximum value and the minimum value of the magnetic anomaly gradient value of the single measuring line is obtained through the method, the actual pipeline burial depth value is calculated through a deviation ratio calculation formula. According to the method provided by the invention, the measurement data measured by the three-component magnetic sensor are fully utilized, the positioning result is more accurate, and the extra error caused by the need of pole-changing operation in other methods is overcome. The defect that the measuring line must be perpendicular to the axis direction of the pipeline when the pipeline burial depth is calculated through other methods is overcome, and the working efficiency is higher.

Description

Technical Field

[0001] The invention belongs to the field of buried metal pipeline positioning, and in particular refers to a buried pipeline depth positioning method based on two-dimensional body magnetic anomaly characteristics. Background Art

[0002] Oil and gas pipelines are key carriers of energy transportation. If the exact spatial position of existing pipelines cannot be accurately determined, it is very easy to damage underground pipelines during construction, resulting in serious consequences. Magnetic detection is a passive detection method. Compared with active detection, it is easier to operate and is not affected by weather factors. There is no need to clean the pipes during the measurement process. With the development of magnetic measurement technology, from total field and its gradient to three-component measurement and then to full tensor magnetic gradient measurement, the measured data is becoming more and more abundant, and methods for pipeline positioning are emerging in an endless stream. The existing method based on a single total field sensor has the advantage that it measures scalar data and is insensitive to attitude changes and vibration noise. The disadvantage is that the measurement data is single, and if you want to accurately locate the target body, you need to increase the number of sensors or increase the number of measurement lines for multiple measurements. Three-component magnetic measurement and full tensor magnetic measurement can obtain more measurement information. Compared with three-component magnetic measurement, full tensor magnetic measurement has higher requirements for the installation accuracy of magnetic sensors, higher costs, and shallower detection depth. Therefore, the present invention performs measurement based on a three-component magnetic sensor, but the existing methods based on three-component magnetic measurement have the following disadvantages: prior information is required to ensure that the measurement line is perpendicular to the pipeline axis direction; magnetic pole operation is required, thereby introducing additional errors and affecting positioning accuracy. Summary of the invention

[0003] The purpose of the present invention is to address the limitations of the existing technology for locating buried metal pipelines based on three-component magnetism, especially the problem that the existing method requires prior information and requires magnetic pole operation to introduce additional errors, and to provide a buried pipeline depth positioning method based on two-dimensional body magnetic anomaly characteristics.

[0004] The present invention is achieved in this way.

[0005] A method for locating the depth of a buried pipeline based on two-dimensional body magnetic anomaly characteristics, the method comprising:

[0006] The inertial navigation system is used to obtain the three-axis attitude angle transformation data of the measurement system for error correction of the three-component magnetic data and conversion of the three-component magnetic data to the geographic coordinate system;

[0007] Calculate the gradient value of the horizontal component of the three-component magnetic survey data after error correction, and determine the position distance of the horizontal coordinate corresponding to the maximum gradient value and the minimum gradient value of the horizontal component;

[0008] The magnetic inclination and declination of the measurement site are obtained through three-component magnetic survey data, and the azimuth of the buried pipeline to the geographic north is calculated through the position coordinates of the same magnetic anomaly data;

[0009] Substituting magnetic inclination, magnetic declination and pipeline azimuth into the magnetic anomaly forward model, the deviation rate is obtained by simulating magnetic anomaly data;

[0010] The actual buried depth of the pipeline can be inferred from the deviation rate.

[0011] Furthermore, when the magnetic inclination is 90 degrees, the distance between the coordinate positions corresponding to the maximum gradient value and the minimum gradient value of the horizontal component of the magnetic anomaly of the pipeline is the buried depth of the pipeline.

[0012] Furthermore, obtaining the magnetic inclination and declination of the measurement location through three-component magnetic survey data includes:

[0013] Magnetic inclination

[0014] Magnetic declination:

[0015] B x is the x-direction component of the three-component magnetic survey data, B y is the component in the y direction of the three-component magnetic survey data; B z is the component in the z direction of the three-component magnetic data.

[0016] Furthermore, before measuring, after determining the geographic north direction, measure along two survey lines perpendicular to the geographic north direction and record the coordinates of the peak point of the magnetic anomaly;

[0017] according to Get the pipeline azimuth. x, x 0 is the east position coordinate, y, y 0 is the north position coordinate, x 0 ,y 0 is the position coordinate of the maximum point of the magnetic anomaly curve.

[0018] Furthermore, the pipeline burial depth is inferred from the deviation rate, and the calculation formula of the deviation rate δ is:

[0019] Among them, l is the distance between the horizontal component's maximum and minimum gradient positions on the horizontal coordinate, and H is the buried depth of the pipeline.

[0020] Furthermore, the gradient is obtained by interpolating the magnetic anomaly horizontal component data into equally spaced data and obtaining the gradient value of the magnetic anomaly horizontal component data by difference.

[0021] Furthermore, the deviation rate between the position distance and the preset pipeline burial depth is calculated according to the magnetic inclination, magnetic declination and pipeline azimuth, including:

[0022] Substitute the magnetic inclination, magnetic declination and pipeline azimuth into the magnetic anomaly forward model, simulate the magnetic anomaly horizontal component data according to the magnetic anomaly forward model, obtain the gradient value of the magnetic anomaly horizontal component data by difference, and obtain the horizontal component position distance corresponding to the maximum gradient value and the minimum gradient value according to the gradient value of the magnetic anomaly horizontal component data;

[0023] The deviation rate is calculated based on the location distance and the preset pipeline burial depth.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] Compared with the traditional method, the buried pipeline depth positioning method of the present invention does not require prior information and can calculate the buried pipeline depth with at least two measuring lines, thereby greatly improving work efficiency.

[0026] Compared with the traditional positioning algorithm, the buried pipeline depth positioning method of the present invention does not need to perform magnetic pole positioning, thus avoiding the additional error introduced by magnetic pole positioning and improving the positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the buried pipeline azimuth calculation principle provided by an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of the principle of a method for locating the buried depth of a buried pipeline provided by an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of location distance provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] A method for locating the depth of a buried pipeline based on two-dimensional body magnetic anomaly characteristics, the method comprising:

[0032] The inertial navigation system is used to obtain the three-axis attitude angle transformation data of the measurement system for error correction of the three-component magnetic data and conversion of the three-component magnetic data to the geographic coordinate system;

[0033] Calculate the gradient value of the horizontal component of the three-component magnetic survey data after error correction, and determine the position distance of the horizontal coordinate corresponding to the maximum gradient value and the minimum gradient value of the horizontal component;

[0034] The magnetic inclination and declination of the measurement site are obtained through three-component magnetic survey data, and the azimuth of the buried pipeline to the geographic north is calculated through the position coordinates of the same magnetic anomaly data;

[0035] Substituting magnetic inclination, magnetic declination and pipeline azimuth into the magnetic anomaly forward model, the deviation rate is obtained by simulating magnetic anomaly data;

[0036] The actual buried depth of the pipeline can be inferred from the deviation rate.

[0037] The method of the present invention calculates the azimuth of the buried pipeline and the geographic north direction through the position coordinates of the same magnetic anomaly data; the deviation rate of the position distance and the actual buried depth of the pipeline under different magnetic inclinations, magnetic declinations, and pipeline azimuths can be determined through theoretical calculation. That is, the ratio of the deviation of the position distance and the actual buried depth of the pipeline to the actual buried depth, the deviation rate is consistent under different pipeline buried depths, the same magnetic inclination, magnetic declination and pipeline azimuth, so through the above process, after calculating the magnetic inclination, magnetic declination and pipeline azimuth from the measurement data, the deviation rate is calculated by simulating the magnetic anomaly and presetting the pipeline buried depth, and then the actual pipeline buried depth is inferred from the deviation rate obtained by the simulation calculation. The present invention uses that when the magnetic inclination is 90 degrees, the coordinate position distance corresponding to the maximum gradient value and the minimum gradient value of the horizontal component of the magnetic anomaly of the two-dimensional pipeline is the pipeline buried depth. When the magnetic inclination is not 90 degrees, the pipeline buried depth value can be preset after calculating the magnetic inclination, magnetic declination and pipeline azimuth to calculate the deviation rate, and then the pipeline buried depth value is inferred. After determining the pipeline azimuth, the method of the present invention can accurately locate the buried depth of the pipeline through the data of a single survey line, greatly improving the detection efficiency, avoiding the additional error introduced by the magnetic pole, and improving the positioning accuracy.

[0038] The specific implementation process of the present invention includes:

[0039] S1. The magnetic measurement system is equipped with a three-component magnetometer, an inertial navigation system, and a synchronous magnetic attitude data acquisition device. The three-component magnetometer and the inertial navigation system are installed on a non-magnetic platform for data acquisition. The acquisition system is used to correct the errors of the measured attitude data and magnetic anomaly data, and the magnetic measurement data is converted to the geographic coordinate system.

[0040] S2. Calculate the magnetic inclination and declination based on the three-component magnetic survey data.

[0041] Magnetic inclination

[0042] Magnetic declination

[0043] S3. Calculate the pipeline azimuth. Before measuring, determine the geographic north direction, measure along two survey lines perpendicular to the geographic north direction, and record the coordinates of the magnetic anomaly peak point.

[0044] according to Get the pipe azimuth, see Figure 1 shown.

[0045] S4. Substituting the magnetic inclination, magnetic declination and pipeline azimuth into the pipeline magnetic anomaly forward model, the deviation rate can be obtained. The deviation rate refers to the ratio of the deviation between the position distance and the actual burial depth to the actual burial depth. In the pipeline magnetic anomaly forward model, the pipeline coordinate system is established with the center point of the buried pipeline as the coordinate origin, and the magnetic anomaly generated by the pipeline is calculated by the Poisson formula of the gravity magnetic potential field. When the pipeline burial depth H is equal to the survey line position y, the gradient value of the horizontal component is the largest at this time. Based on this principle, the pipeline burial depth can be determined. Consider the general situation when the magnetic inclination is not 90 degrees, and consider the influence of the pipeline azimuth. Define the angle between the pipeline and the geographic north direction as the angle of the pipeline azimuth. Establish a geographic coordinate system, convert the magnetic anomaly generated in the pipeline coordinate system to the geographic coordinate system through the rotation matrix, calculate the position distance of the horizontal coordinate corresponding to the maximum gradient value and the minimum gradient value of the magnetic anomaly horizontal component under different magnetic inclination, magnetic declination and pipeline azimuth, and find that the deviation rate is consistent under different burial depths, the same magnetic inclination, magnetic declination and pipeline azimuth. Therefore, the deviation rate can be calculated by presetting the pipeline burial depth value. The deviation rate calculation formula is:

[0046]

[0047] l is the distance between the maximum and minimum values ​​of the horizontal component gradient curve and the horizontal coordinate, and H is the buried depth of the pipeline.

[0048] The horizontal component data of magnetic anomaly are interpolated into equally spaced data, and the gradient value of the horizontal component data of magnetic anomaly is obtained by difference. The position coordinate corresponding to the maximum value of the magnetic gradient data curve is separated from the position coordinate corresponding to the minimum value.

[0049] In the present invention, the pipeline magnetic anomaly forward model is used. The pipeline coordinate system is established with the center point of the buried pipeline as the coordinate origin, and the magnetic anomaly generated by the pipeline is calculated using the Poisson formula of the gravity magnetic potential field. The gravitational potential of an object with a volume of v and uniform density is:

[0050]

[0051] G is the gravitational constant, ρ is the density, and r is the distance between the observation point and the object.

[0052] The magnetic potential of the same uniformly magnetized object is:

[0053]

[0054] M is the magnetization vector.

[0055] T is the geomagnetic field, κ is the magnetic susceptibility of the pipeline, μ 0 Magnetic permeability of vacuum.

[0056] Substituting the gravitational potential calculation formula into the magnetic potential calculation formula, we get:

[0057]

[0058] pass Calculate the magnetic field, where μ 0 is the magnetic permeability of vacuum.

[0059] The three-component magnetic field expression calculated above is:

[0060]

[0061] H ax represents the horizontal x-direction component of the magnetic anomaly, represents the horizontal y-direction component, and Z a Represents the vertical component of the magnetic anomaly, V xx represents the partial derivative of the gravitational potential V in the x direction, V yx represents the partial derivative of the gravitational potential V in the y direction in the x direction, V zx represents the partial derivative of the gravitational potential V in the z direction in the x direction;

[0062] in

[0063] I is the magnetic inclination, D is the magnetic declination.

[0064] For a two-dimensional body, that is, an object with infinite length along the strike direction, its burial depth, cross-sectional shape, and magnetization characteristics are all stable along the horizontal strike direction. In this case, its field in the spatial rectangular coordinate system is only related to the coordinates (y, z) and has nothing to do with x. Here, the x direction is consistent with the direction of the pipeline strike. The expression of its three-component magnetic field becomes:

[0065]

[0066] The gravitational potential of a horizontal cylinder is expressed as:

[0067] V=-2GρSlnr

[0068] S is the cross-sectional area of ​​the pipe, x, y, z are the coordinates of the observation plane, x 0 ,y 0 、z 0 is the pipeline plane coordinate.

[0069] After taking the second partial derivative of the gravitational potential expression of the horizontal cylinder, substitute it into the three-component magnetic anomaly expression of the two-dimensional body:

[0070]

[0071] H is the preset pipeline burial depth.

[0072] When the magnetic inclination is 90 degrees, we can get

[0073]

[0074] It can be seen from this that when the pipeline burial depth H is equal to the survey line position y, the horizontal component H ay The gradient value of is the largest at this time. Based on this principle, the buried depth of the pipeline can be determined. The principle diagram is as follows Figure 2 As shown. Consider the general situation when the magnetic inclination is not 90 degrees, and consider the influence of the pipeline azimuth. Define the angle between the pipeline and the geographic north direction as the angle of the pipeline azimuth. Establish a geographic coordinate system, convert the magnetic anomaly generated in the pipeline coordinate system to the geographic coordinate system through the rotation matrix, and calculate the position distance of the horizontal coordinate corresponding to the maximum gradient value and the minimum gradient value of the horizontal component of the magnetic anomaly under different magnetic inclinations, magnetic declinations, and pipeline azimuths. It is found that the deviation rate is consistent under different burial depths, the same magnetic inclination, magnetic declination, and pipeline azimuth. Therefore, after calculating the magnetic inclination, magnetic declination, and pipeline azimuth from the measured data, the deviation rate can be calculated by presetting the pipeline burial depth value through the above-mentioned pipeline magnetic anomaly forward model. The deviation rate calculation formula is:

[0075]

[0076] According to the measured three-component magnetic survey data, the horizontal component data of magnetic anomaly are interpolated into equally spaced data, and the gradient value of the horizontal component data of magnetic anomaly is obtained by difference.

[0077] According to the measured three-component magnetic survey data, the horizontal component gradient curve maximum and minimum corresponding to the horizontal coordinate position distance is obtained, such as Figure 3 The pipeline burial depth H is obtained by the deviation rate calculation formula.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for locating the depth of buried pipelines based on the second-dimensional body magnetic anomaly characteristics, characterized in that: The method includes: The inertial navigation system is used to obtain the three-axis attitude angle transformation data of the measurement system for error correction of the three-component magnetic data and conversion of the three-component magnetic data to the geographic coordinate system; Calculate the gradient value of the horizontal component of the three-component magnetic survey data after error correction, and determine the position distance of the horizontal coordinate corresponding to the maximum gradient value and the minimum gradient value of the horizontal component; The magnetic inclination and declination of the measurement site are obtained through three-component magnetic survey data, and the azimuth of the buried pipeline to the geographic north is calculated through the position coordinates of the same magnetic anomaly data; Substituting magnetic inclination, magnetic declination and pipeline azimuth into the magnetic anomaly forward model, the deviation rate is obtained by simulating magnetic anomaly data; The actual buried depth of the pipeline can be inferred from the deviation rate.

2. The method for locating the depth of buried pipelines based on the second-degree body magnetic anomaly characteristics according to claim 1 is characterized in that: When the magnetic inclination is 90 degrees, the distance between the coordinate positions corresponding to the maximum gradient value and the minimum gradient value of the horizontal component of the pipeline's magnetic anomaly is the buried depth of the pipeline.

3. The method for locating the depth of buried pipelines based on the second-degree body magnetic anomaly characteristics according to claim 1 is characterized in that: The magnetic inclination and declination of the measurement site are obtained through three-component magnetic survey data, including: Magnetic inclination Magnetic declination: B x is the x-direction component of the three-component magnetic survey data, B y is the component in the y direction of the three-component magnetic survey data; B z is the component in the z direction of the three-component magnetic data.

4. The method for locating the depth of buried pipelines based on the second-degree body magnetic anomaly characteristics according to claim 1 is characterized in that: Before measuring, determine the geographic north direction, measure along two survey lines perpendicular to the geographic north direction, and record the coordinates of the peak point of the magnetic anomaly; according to The pipeline azimuth is obtained, x and x0 are the east position coordinates, y and y0 are the north position coordinates, and x0 and y0 are the position coordinates of the maximum value point of the magnetic anomaly curve.

5. The method for locating the depth of buried pipelines based on the second-degree body magnetic anomaly characteristics according to claim 1, characterized in that: The pipeline burial depth can be inferred from the deviation rate. The calculation formula of the deviation rate δ is: Among them, l is the distance between the horizontal component's maximum and minimum gradient positions on the horizontal coordinate, and H is the buried depth of the pipeline.

6. The method for locating the depth of buried pipelines based on the second-degree body magnetic anomaly characteristics according to claim 1 is characterized in that: The gradient is obtained by interpolating the horizontal component data of the magnetic anomaly into equally spaced data and then calculating the gradient value of the horizontal component data of the magnetic anomaly by difference.

7. The method for locating the depth of buried pipelines based on the second-degree body magnetic anomaly characteristics according to claim 1, characterized in that: The deviation rate between the position distance and the preset pipeline burial depth is calculated based on the magnetic inclination, magnetic declination and pipeline azimuth, including: Substitute the magnetic inclination, magnetic declination and pipeline azimuth into the magnetic anomaly forward model, simulate the magnetic anomaly horizontal component data according to the magnetic anomaly forward model, obtain the gradient value of the magnetic anomaly horizontal component data by difference, and obtain the horizontal component position distance corresponding to the maximum gradient value and the minimum gradient value according to the gradient value of the magnetic anomaly horizontal component data; The deviation rate is calculated based on the location distance and the preset pipeline burial depth.

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