Deeply buried pipeline positioning method and system based on magnetic gradient value
By using an effective magnetization tilt angle calculation method based on magnetic gradient values, the burial depth and location of the target pipeline can be directly analyzed using single-hole measurement data. This solves the problems of low measurement accuracy, poor safety, and uncontrollable cost in existing technologies, and achieves efficient and reliable deep-buried pipeline positioning.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN SURVEYING & MAPPING INST CO LTD
- Filing Date
- 2026-04-15
- Publication Date
- 2026-06-16
AI Technical Summary
Existing technologies have low measurement accuracy, poor safety, low efficiency, uncontrollable costs, and high dependence on manual identification in the detection of deeply buried metal pipelines, which poses risks, especially in the detection of high-risk pipelines.
By introducing an effective magnetization tilt angle calculation method and utilizing the vertical magnetic gradient characteristic value of a single borehole, the burial depth of the target pipeline and its lateral distance and absolute positional relationship with the borehole can be directly analyzed. Precise positioning can be achieved using single-bore measurement, reducing the need for multi-bore combined and iterative calculations.
It improves detection accuracy and safety, reduces engineering costs and time, reduces reliance on manual identification, and achieves efficient and reliable positioning of deeply buried pipelines.
Smart Images
Figure CN122018017B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of geophysical exploration and underground pipeline detection technology, specifically relating to a method and system for locating deeply buried pipelines based on magnetic gradient values. Background Technology
[0002] The in-well magnetic gradient method is an important technique for detecting deeply buried metal pipelines. For underground pipelines containing metallic materials at considerable depths, conventional electromagnetic induction methods are insufficient. In-well detection technology, by placing the receiving device directly into the borehole, effectively shortens the signal propagation path and significantly improves the quality of deep signal acquisition. The receiver acquires high-frequency signals as it gradually descends along the borehole, generating a signal depth profile excited by the target pipeline. In a uniform soil layer without ferromagnetic materials, the magnetic field strength should theoretically be uniform. However, if ferromagnetic materials are present, an abnormal magnetic field will be formed around the target pipeline under the magnetization effect of the background geomagnetic field. This abnormal magnetic field will exhibit a significant acceleration range as the distance between the probe and the pipeline changes. Therefore, the spatial location of the target pipeline can be determined by observing the changes in its magnetic anomaly, especially the distribution of the gradient value of the vertical component.
[0003] Currently, the data post-processing tools for deep-buried pipeline detection instruments based on well magnetic gradient characteristic values in China are relatively rudimentary. The estimation of pipeline location and burial depth mainly relies on manual curve identification, followed by drilling to gradually approach the horizontal projection position of the target pipeline until the drilling position can collide with the target pipeline. Chinese patent CN108241174A discloses a method for detecting deep-buried metal pipelines. The steps are as follows: first, collect the original design and construction data; then, arrange several cross-sections perpendicular to the pipeline direction within the pipeline estimation range. Each detection cross-section is centered on the pipeline estimation position, with 5 to 8 boreholes arranged perpendicular to its direction. The position and elevation of all boreholes are measured; next, the probe of the magnetic gradient meter is placed inside the casing, and the boreholes are initially detected using the magnetic gradient method. Then, two to three precision boreholes are arranged on the pipeline cross-section. These precision boreholes are guided by gravity to lower the drill rod until they fully contact the pipeline surface. Finally, the burial depth of the pipeline contact point is accurately determined by measuring the length of the drill rod.
[0004] The detection method has low scientific measurement accuracy, high requirements for working conditions, poor safety when the target pipeline is a high-risk pipeline, low efficiency of the gradual approach method, poor cost controllability, and high dependence on manual identification. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for precise positioning of deeply buried pipelines based on the characteristic values of the vertical magnetic gradient of a single borehole. This method improves the detection process, introduces an effective magnetization inclination angle calculation method, and utilizes the extreme value characteristic values extracted from the single-bore gradient curve to directly analyze the burial depth of the target pipeline and its lateral distance and absolute positional relationship with the borehole.
[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:
[0007] A method for locating deeply buried pipelines based on magnetic gradient values includes the following steps:
[0008] 1) Information acquisition: Obtain the geomagnetic field parameters of the construction area and the preliminary horizontal azimuth of the target pipeline, and calculate the effective magnetization inclination angle of the target pipeline in the radial plane perpendicular to the direction.
[0009] 2) Extreme distance calculation: The vertical magnetic gradient sequence is collected in a single-hole measuring well near the target pipeline and an observation curve is formed. The depth value corresponding to the extreme value is extracted from the observation curve and the extreme distance is calculated.
[0010] 3) Solve for the absolute value of the horizontal distance: Based on the preset pipeline magnetic field model, combine the effective magnetization inclination angle and the extreme distance to construct a theoretical relationship and obtain the absolute value of the horizontal distance between the target pipeline and the single-hole measuring well.
[0011] 4) Determine the horizontal orientation symbol: Generate the theoretical curve of the vertical magnetic gradient based on the absolute value of the horizontal distance and the preset initial depth. Compare the morphological characteristics of the observed curve and the theoretical curve between the extreme values. If they are consistent, the horizontal distance between the target pipeline position and the borehole is not negative; otherwise, the horizontal distance is negative.
[0012] 5) Burial depth inversion: Based on the horizontal distance with positive and negative signs, the depth value corresponding to the extreme value, and the effective magnetization inclination angle, the accurate burial depth of the target pipeline is calculated by inversion.
[0013] Preferably, For effective magnetization tilt angle, ,in, The initial horizontal azimuth of the target pipeline. For the geomagnetic field inclination, It is the magnetic declination; Horizontal spacing
[0014] ;
[0015] The extreme distance, , These are the depth values corresponding to the extreme values, and z 1>z 2 Calculate the burial depth of the target pipeline The inversion formula is, ,
[0016] , ; It is a dimensionless parameter.
[0017] Preferably, the theoretical curve for generating the vertical magnetic gradient is... The calculation formula is as follows:
[0018] ,
[0019] Horizontal spacing , For relative depth, , The horizontal coordinates and depth values of the target pipeline center. For effective magnetization tilt angle, The effective magnetic moment per unit length, The horizontal coordinates and depth values of the probe. is the vacuum permeability.
[0020] Preferably, the step of comparing the consistency of the morphological features includes:
[0021] Extract the extreme values and corresponding depth values of the observed curve and the theoretical curve respectively, and calculate the extreme value ratio of the curves based on the corresponding gradient values;
[0022] The point-by-point sequential marker parameters of the observed curve and the theoretical curve between extreme values are calculated respectively. By analyzing the change law of the sign of the point-by-point sequential marker parameters in the depth sounding sequence, the shape of the entire curve is compressed into a global sequential marker.
[0023] If the extreme values of the observed curve and the theoretical curve are within the same range and the global order markers are equal, then the morphological characteristics are considered to be consistent; otherwise, they are inconsistent.
[0024] Preferably, the global sequence flag is set to mutually exclusive values for the two symbols according to the order in which the extreme values appear along the direction of increasing depth.
[0025] Preferably, step 2) of acquiring the vertical magnetic gradient sequence includes:
[0026] Preliminary on-site survey of the target pipeline's route to obtain an estimated burial depth. A single-hole measuring well is drilled at the plane projection mark;
[0027] The diameter of the single-hole measuring well is not less than 8 cm, and the drilling depth is not less than 1.5 m. ;
[0028] The magnetic gradient meter probe was lowered to the bottom of the well at a constant speed, and the vertical component magnetic induction intensity and depth data were collected simultaneously, with a sampling interval of no more than 0.05m.
[0029] Preferably, the information acquisition step in step 1) includes:
[0030] The magnetic inclination of the geomagnetic field is obtained based on the international geomagnetic reference field model or local geomagnetic station data. I And magnetic declination D ;
[0031] A metal pipeline detector was used for on-site reconnaissance to preliminarily determine the approximate route and burial depth of the target pipeline, and to obtain its initial horizontal azimuth. .
[0032] Preferably, the theoretical curve in the formula Take the estimated burial depth from the survey Or 10m.
[0033] A system for implementing the aforementioned method for locating deeply buried pipelines based on magnetic gradient values, characterized in that it includes,
[0034] The information acquisition module is used to obtain the geomagnetic field parameters of the construction area and the initial horizontal azimuth of the target pipeline, and to calculate the effective magnetization inclination angle of the target pipeline in the radial plane perpendicular to the direction.
[0035] The extreme distance calculation module is used to collect vertical magnetic gradient sequences in single-hole measurement wells near the target pipeline and form observation curves, extract the depth values corresponding to the extreme values from the observation curves, and calculate the extreme distance.
[0036] The module for solving the absolute value of the horizontal distance is used to construct a theoretical relationship based on the preset pipeline magnetic field model, combined with the effective magnetization inclination angle and the extreme distance, and to obtain the absolute value of the horizontal distance between the target pipeline and the single-hole measuring well.
[0037] The horizontal orientation symbol module is used to generate a theoretical curve of the vertical magnetic gradient based on the absolute value of the horizontal distance and the preset initial depth. The observed curve and the theoretical curve are compared for consistency in their morphological characteristics between extreme values. If they are consistent, the horizontal distance between the target pipeline position and the borehole is not negative; otherwise, the horizontal distance is negative.
[0038] The burial depth inversion module is used to calculate the precise burial depth of the target pipeline based on the horizontal distance with positive and negative signs, the depth value corresponding to the extreme value, and the effective magnetization inclination angle.
[0039] The advantages and beneficial effects of this invention are as follows:
[0040] This invention first introduces prior information to overcome ambiguity, proposing a priori calculation method based on geographic information and the target pipeline alignment. This replaces the traditional approach of directly inverting from collected data curves, effectively reducing inversion uncertainty and enhancing the method's stability. Moreover, inversion can be performed from a single well, requiring only the vertical gradient data of one borehole. The target pipeline location parameters are directly calculated using analytical formulas, eliminating the need for multi-well combinations or complex iterations, significantly reducing engineering costs and time, and further minimizing the possibility of pipeline damage. Simultaneously, morphological verification is performed using extreme value ratios, without relying on interpretation experience, resulting in high accuracy. The spatial location inversion formula essentially takes into account all curve morphological characteristic parameters, further enhancing the reliability of the inversion results. Attached Figure Description
[0041] Figure 1 This is a schematic diagram of the pipeline magnetic field model.
[0042] Figure 2 This is a schematic diagram of the effective magnetic tilt angle model for a pipeline.
[0043] Figure 3 This is a comparison curve of magnetic gradients.
[0044] Figure 4 This is a flowchart illustrating the specific implementation of the present invention.
[0045] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation
[0046] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.
[0047] The theoretical basis of this invention is described in general. First, a forward model consistent with engineering practice is established, such as... Figure 1 As shown, an infinitely long horizontal cylinder is used to simulate the target pipeline, and a coordinate system consistent with engineering surveying practices is established: the Z-axis is vertically upward and positive, the X-axis is horizontal and perpendicular to the pipeline direction, and the Y-axis is parallel to the pipeline direction.
[0048] Using Poisson's equation, we can deduce the vertical component of the magnetic field of the guide wire. and its vertical gradient The analytical expression, derived from the vertical gradient The theoretical curve of the vertical magnetic gradient is obtained, which is referred to as the theoretical curve in this invention.
[0049] (1)
[0050] (2)
[0051] Horizontal spacing Let be the vertical component of the pipeline's magnetic field. , For relative depth, , The horizontal coordinates and depth values of the target pipeline center. For effective magnetization tilt angle, The effective magnetic moment per unit length, The probe's horizontal coordinates and depth values are... The permeability of free space, The distance is the straight-line distance from the probe to the center of the target pipeline. The method of the present invention is applicable to the detection of metal pipelines at various depths and has higher economic efficiency in the detection of deeply buried pipelines, especially deep buried pipelines and ultra-deep pipelines.
[0052] To avoid direct inversion from the data To address the ambiguity arising from this, this invention proposes a method based on geographic information and the approximate route of deeply buried pipelines. Calculation methods, such as Figure 2 As shown, an infinitely long horizontal cylinder is used to simulate the target pipeline, establishing a coordinate system consistent with geographical orientation: with north, east, and down as the coordinate axes, and the three axes perpendicular to each other. First, based on the geographical location of the construction area, the geomagnetic field is used... T magnetic inclination Magnetic declination Assume that after the target pipeline is magnetized by the Earth's magnetic field, it generates a magnetic moment vector parallel to the direction of the Earth's magnetic field T. ; the magnetic moment vector Projecting onto a radial plane perpendicular to the pipeline's direction yields the components within that plane. Then divide the portion Decomposed into horizontal components With vertical component Therefore, the effective magnetization tilt angle in the radial plane of the target pipeline can be derived. The calculation formula is:
[0053] (3)
[0054] The horizontal lateral distance inversion derivation of the target pipeline based on a single well feature value is as follows, using the vertical magnetic gradient curve acquired from the well. (Hereinafter referred to as the observation curve, i.e., the curve formed by actual measurement data) Feature values are extracted from the observation curve. The observation curve will have two extreme values: a maximum and a minimum. The closer the drilling location is to the target pipeline, the greater the deviation of these two extreme values from the mean. If no maximum or minimum value appears, it indicates that the drilling data is invalid, meaning the distance to the target pipeline is too far and exceeds the calculable range. (See Appendix) Figure 3 When the probe descends to near the burial depth of the target pipeline, the vertical magnetic gradient curve (observation curve) is observed. Dramatic fluctuations will occur, with the vertical magnetic gradient value deviating significantly from its approximate mean. This allows for the extraction of the two extreme values: let the depth corresponding to the left extreme value be... Its gradient value is The right-hand extreme value corresponds to a depth of Its gradient value is .
[0055] The extreme distance can be obtained: Introducing dimensionless parameters Substituting into the magnetic gradient formula (2) and taking the derivative, the effective magnetization tilt angle has been calculated. In this case, find the dimensionless parameter corresponding to the extreme values of the derivative. There are two solutions:
[0056] , (4)
[0057] Based on the geometric relationship between the extreme points and the target pipeline parameters, the depth values corresponding to the two extreme points on the left and right sides of the theoretical curve are obtained as follows:
[0058] (5)
[0059] (6)
[0060] The horizontal distance between the target pipeline and the well can be solved. :
[0061] (7)
[0062] At this time, the horizontal distance cannot be known. The sign, i.e., the absolute positional relationship between the target pipeline and the well, can be determined by comparing the similarity between the gradient theoretical curve constructed by the theoretical model and the vertical magnetic gradient observation curve of the field data in the portion between extreme values. Therefore, the extreme value ratio of the vertical magnetic gradient observation curve of the field data is first calculated. :
[0063] (8)
[0064] To complete the comparison with the observed curve, the formation of the theoretical curve requires two initial conditions: the horizontal distance between the target pipeline and the wellbore. (The sign of the arrow needs to be known) and the depth value of the target pipeline. The target pipeline burial depth has no impact on the morphology of the section between extreme values; the value can be selected from the estimated burial depth obtained from the survey. If the reconnaissance results are unsatisfactory, it can be directly set to 10m. Take its absolute value and use the formulas in (3)-(5) to calculate the extreme value ratio R of the vertical magnetic gradient theoretical curve:
[0065] (9)
[0066] Simultaneously, a point-by-point sequential flag parameter is introduced for the theoretical curve. By analyzing the depth sounding sequence The pattern of sign changes compresses the shape of the entire curve into a global sequence marker. The global order flag is set according to the order in which the maximum and minimum values appear. You can set two mutually exclusive values for the symbols, or you can choose to set two different values. For example, = +1 indicates that the abnormal curve first shows a maximum value and then a minimum value. =-1 indicates that the outlier curve first appears as a minimum and then as a maximum. Similarly, the global order flag for observing the curve is... The same definition The value of .
[0067] If and and or
[0068] and and Time; (10)
[0069] The observed curve and the theoretical curve share the same morphological characteristics, which confirms that the target pipeline position and the wellbore satisfy the given conditions in the constructed model coordinate system. The relationship is as follows. Otherwise, it can be proven that the observed curve and the theoretical curve have inconsistent morphological characteristics, that is, the target pipeline location and the drilling interval satisfy the following. The relationship, that is .
[0070] The depth of the target pipeline can be obtained using formulas (4) to (6). ;
[0071] (11)
[0072] like Figure 4 As shown, a method for locating deeply buried pipelines based on magnetic gradient values according to the present invention includes the following steps:
[0073] 1) Information Acquisition: Obtain the geomagnetic field parameters of the construction area and the preliminary horizontal azimuth of the target pipeline, and calculate the effective magnetization inclination of the target pipeline in the radial plane perpendicular to its direction. , Generally, during the initial survey of the target pipeline route, metal pipeline detectors, such as the Radeon PCM+ (Pipeline Current Mapper), are used for on-site reconnaissance. This is generally effective for detecting deeply buried pipelines, allowing for a preliminary determination of the general route and burial depth of the target pipeline, marking its planar projection position on-site, and roughly determining its horizontal azimuth. Furthermore, based on the geographical coordinates of the construction area, the magnetic inclination of the geomagnetic field is obtained from the International Geomagnetic Reference Field (IGRF) model or local geomagnetic station data. Magnetic declination The globally accepted and industry-standard calculation benchmark is the International Geomagnetic Reference Field (IGRF), which is updated every 5 years by the International Association for Geomagnetism and Upper Atmosphere Physics (IAGA). It can fit the global main magnetic field distribution through spherical harmonic function expansion to calculate geomagnetic elements at any geographical location and time. The accuracy of magnetic declination and magnetic inclination is better than 0.1°, which fully meets the needs of engineering exploration.
[0074] 2) Acquire the vertical magnetic gradient sequence in a single-well measurement well near the target pipeline and form an observation curve. Calculate the extreme value distance from the depth values corresponding to the two extreme points of the observation curve; that is, measure and obtain the system's vertical magnetic gradient sequence in a single-well measurement well near the target pipeline. Based on the observed curves, single-hole measurement drilling generally does not require auxiliary measurement drilling; the target pipeline can be determined with just one well, which is fundamentally different from existing technologies that require multiple measurement wells. The depth values corresponding to two extreme points are selected from the magnetic gradient observation curve, and these two extreme points are denoted as... Given that z1>z2, calculate the extreme distance. , Specifically, the first step is to conduct a reconnaissance of the target pipeline to obtain its approximate location and burial depth. The approximate location of the pipeline is marked on-site with paint or wooden stakes, and the burial depth is estimated. Then, drilling and surveying are carried out. Vertical wells are drilled at the marked locations left during the reconnaissance phase, with a borehole diameter of at least 8 cm and a depth generally not less than 1.5 meters. The magnetic gradient meter probe was lowered to the bottom of the well at a constant speed, and the vertical component of the magnetic induction intensity was collected simultaneously. (The magnetic gradient meter will simultaneously calculate the magnetic gradient value of the vertical component) and depth z, and the sampling interval should not be greater than 0.05m.
[0075] 3) Solving for the absolute value of the horizontal distance: Based on the preset pipeline magnetic field model, and combined with the effective magnetization inclination angle and extreme distance, a theoretical relationship containing dimensionless parameters is constructed to calculate the absolute value of the horizontal distance between the target pipeline and the single-hole measuring well. Specifically, the horizontal distance between the target pipeline and the well is... ,in, .
[0076] 4) Determine the horizontal orientation sign: Based on the absolute value of the horizontal distance and the preset initial depth, generate a theoretical curve of the vertical magnetic gradient. Compare the morphological characteristics of the observed curve and the theoretical curve between extreme values. If they match, the horizontal distance is not negative; otherwise, the horizontal distance between the target pipeline position and the borehole is negative. That is, let the horizontal distance be... The theoretical curve of the vertical magnetic gradient is generated, and the morphological characteristics of the interval between the extreme values of the theoretical curve and the observed curve are judged to be consistent. If they are consistent, the target pipeline position and the borehole satisfy the horizontal distance requirement. ,in, This indicates that the wellbore coincides with the target pipeline; otherwise, the target pipeline location and the borehole meet the horizontal lateral distance requirement. The steps for determining whether morphological features are consistent include:
[0077] Extract the extreme values and corresponding gradient values of the observed curve and the theoretical curve respectively, and calculate the ratio of the extreme values of the curves from the corresponding gradient values;
[0078] The point-by-point sequential marker parameters of the observed curve and the theoretical curve in the interval between extreme values are calculated respectively. By analyzing the change law of the sign of the point-by-point sequential marker parameters in the depth sounding sequence, the shape of the entire curve is compressed into a global sequential marker.
[0079] If the extreme values of the observed curve and the theoretical curve are within the same range and the global order markers are equal, then the morphological characteristics are considered to be consistent; otherwise, they are inconsistent.
[0080] 5) Burial Depth Inversion: Based on the horizontal distance with positive and negative signs, the depth values corresponding to extreme values, and the dimensionless parameters obtained from the effective magnetization inclination angle, the precise burial depth of the target pipeline is calculated by inversion. The formula is , , ; It is a dimensionless parameter.
[0081] This invention introduces prior information to overcome ambiguity: it proposes a prior calculation method based on geographic information and the target pipeline orientation, replacing the traditional approach of directly inverting from collected data curves. This effectively reduces the uncertainty of the inversion and enhances the stability of the method. Inversion can be performed using a single well, making it highly efficient and economical: requiring only the vertical gradient data from one well, the target pipeline location parameters are directly calculated using analytical formulas, eliminating the need for multi-well collaboration or complex iterations, significantly reducing engineering costs and time. Furthermore, the accuracy is controllable and the process is complete: morphological verification is performed using extreme value ratios, without relying on interpretation experience, resulting in high accuracy; the spatial location inversion formula basically takes into account all morphological feature parameters in the magnetic gradient curve, leading to higher reliability of the inversion results.
[0082] Furthermore, the steps for obtaining the observation curve include a data preprocessing step, which involves filtering and denoising the original discrete detection data, and outputting the system's vertical magnetic gradient sequence through differential calculation or direct instrument output. Then, the observation curve is generated by plotting multiple vertical gradient values of the vertical magnetic gradient sequence. This is achieved using a data visualization tool such as Excel to generate a line chart.
[0083] This invention effectively suppresses noise interference and improves the accuracy and stability of vertical magnetic gradient data by filtering and denoising the raw detection data. Furthermore, the gradient sequence is plotted as an observation curve that varies with depth, which intuitively presents the morphological characteristics of magnetic anomalies, facilitates rapid analysis of extreme value order, and provides reliable morphological constraints for subsequent target pipeline positioning and parameter inversion. At the same time, it is compatible with multiple gradient acquisition methods and has good versatility and practicality.
[0084] Furthermore, this invention also discloses a system for implementing the aforementioned method for locating deeply buried pipelines based on magnetic gradient values, comprising,
[0085] The information acquisition module is used to obtain the geomagnetic field parameters of the construction area and the initial horizontal azimuth of the target pipeline, and to calculate the effective magnetization inclination angle of the target pipeline in the radial plane perpendicular to the direction.
[0086] The extreme distance calculation module is used to collect vertical magnetic gradient sequences in single-hole measurement wells near the target pipeline and form observation curves, extract the depth values corresponding to extreme points from the observation curves, and calculate the extreme distance.
[0087] The module for solving the absolute value of the horizontal distance is used to construct a theoretical relationship based on the preset pipeline magnetic field model, combined with the effective magnetization inclination angle and the extreme distance, and to obtain the absolute value of the horizontal distance between the target pipeline and the single-hole measuring well.
[0088] The horizontal orientation symbol module is used to generate a theoretical curve of the vertical magnetic gradient based on the absolute value of the horizontal distance and the preset initial depth. The observed curve and the theoretical curve are compared for consistency in the extreme value range. If they are consistent, the horizontal distance between the target pipeline position and the borehole is not negative; otherwise, the horizontal distance is negative.
[0089] The burial depth inversion module is used to calculate the precise burial depth of the target pipeline based on the horizontal distance with positive and negative signs, the depth value corresponding to the extreme point, and the effective magnetization inclination angle.
[0090] This invention effectively narrows the solution space by introducing prior constraints such as the geomagnetic field and the target pipeline orientation, overcoming the multi-solution problem of traditional inversion methods and improving the stability and accuracy of subsequent calculations. Only single-well detection data is needed to directly analyze the lateral distance parameters of the target pipeline, eliminating the need for multi-well combinations or complex iterations, significantly reducing on-site drilling costs and operational complexity. Through automated comparison of curve morphology features, the horizontal orientation of the target pipeline relative to the well logging is intelligently determined, overcoming identification errors caused by reliance on human experience. Finally, by integrating lateral distance and feature depth with orientation information, high-precision inversion of the absolute burial depth of the target pipeline is achieved. Closed-loop calculation of parameters in each stage ensures high reliability of the three-dimensional spatial positioning results.
[0091] Specific example: In a heating upgrade project in Tianjin, one section involves a pipeline that needs to cross a 300mm diameter steel high-pressure gas pipeline that spans a road. The location and burial depth are unknown. A survey line is set up on site to cross the gas pipeline. It is planned to drill four wells along the survey line for data acquisition. Two wells are arranged on each side of the target pipeline. After drilling wells K1, K2, and K3, the fourth well encounters the target pipeline during the excavation process. The true location and burial depth of the target pipeline can be obtained from this. This example is used to verify the magnetic gradient method in the well of the present invention.
[0092] The magnetic inclination of the Earth's magnetic field in the Tianjin area was obtained through research. Magnetic declination The general route of the target pipeline was determined through on-site reconnaissance. The effective magnetization tilt angle can be obtained from the above parameters. Then, the accuracy of the inversion results of the three well magnetic gradient data was verified. The characteristic parameters obtained from the observation curves of the three wells K1, K2 and K3 and the inversion results are shown in Table 1 below:
[0093] Table 1. Comparison of inversion results for three wells, K1, K2, and K3.
[0094]
[0095] Based on the spatial location of the target pipeline obtained from the fourth well, the burial depth of the target pipeline is -11.42m, and the mean square error of the inversion result is 0.03m. The actual lateral distances from the three wells are 0.52m, 0.70m, and -0.40m, respectively, with mean square errors of 0.05m. All of the above inversion results are better than the accuracy requirements for fine detection of the target pipeline.
[0096] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.
Claims
1. A method for locating deeply buried pipelines based on magnetic gradient values, characterized in that, Includes the following steps, 1) Information acquisition: Obtain the geomagnetic field parameters of the construction area and the preliminary horizontal azimuth of the target pipeline, and calculate the effective magnetization inclination angle of the target pipeline in the radial plane perpendicular to the direction. 2) Extreme distance calculation: The vertical magnetic gradient sequence is collected in a single-hole measuring well near the target pipeline and an observation curve is formed. The depth value corresponding to the extreme value is extracted from the observation curve and the extreme distance is calculated. 3) Solve for the absolute value of the horizontal distance: Based on the preset pipeline magnetic field model, combine the effective magnetization inclination angle and the extreme distance to construct a theoretical relationship and obtain the absolute value of the horizontal distance between the target pipeline and the single-hole measuring well. 4) Determine the horizontal orientation symbol: Generate the theoretical curve of the vertical magnetic gradient based on the absolute value of the horizontal distance and the preset initial depth. Compare the morphological characteristics of the observed curve and the theoretical curve between the extreme values. If they are consistent, the horizontal distance between the target pipeline position and the borehole is not negative; otherwise, the horizontal distance is negative. 5) Burial depth inversion: Based on the horizontal distance with positive and negative signs, the depth value corresponding to the extreme value, and the effective magnetization inclination angle, the accurate burial depth of the target pipeline is calculated by inversion.
2. The method for locating deeply buried pipelines based on magnetic gradient values as described in claim 1, characterized in that, For effective magnetization tilt angle, ,in, The initial horizontal azimuth of the target pipeline. For the geomagnetic field inclination, It is the magnetic declination; Horizontal spacing ; The extreme distance, , z 1 、z 2 These are the depth values corresponding to the extreme values, and z 1 >z 2 Calculate the burial depth of the target pipeline The inversion formula is, , , ; It is a dimensionless parameter.
3. The method for locating deeply buried pipelines based on magnetic gradient values as described in claim 2, characterized in that, Theoretical curve for generating vertical magnetic gradient The calculation formula is as follows: ， Horizontal spacing , For relative depth, , 、 The horizontal coordinates and depth values of the target pipeline center. For effective magnetization tilt angle, The effective magnetic moment per unit length, The horizontal coordinates and depth values of the probe. is the vacuum permeability.
4. The method for locating deeply buried pipelines based on magnetic gradient values as described in claim 1, characterized in that, The steps for comparing the consistency of the morphological features include: Extract the extreme values and corresponding depth values of the observed curve and the theoretical curve respectively, and calculate the extreme value ratio of the curves based on the corresponding gradient values; The point-by-point sequential marker parameters of the observed curve and the theoretical curve between extreme values are calculated respectively. By analyzing the change law of the sign of the point-by-point sequential marker parameters in the depth sounding sequence, the shape of the entire curve is compressed into a global sequential marker. If the extreme values of the observed curve and the theoretical curve are within the same range and the global order markers are equal, then the morphological characteristics are considered to be consistent; otherwise, they are inconsistent.
5. The method for locating deeply buried pipelines based on magnetic gradient values as described in claim 4, characterized in that, Based on the order in which the extreme values appear along the direction of increasing depth, the global sequence flag is set to a value that is mutually exclusive between the two symbols.
6. The method for locating deeply buried pipelines based on magnetic gradient values as described in claim 1, characterized in that, The step of acquiring the vertical magnetic gradient sequence in step 2) includes: Preliminary on-site survey of the target pipeline's route to obtain an estimated burial depth. A single-hole measuring well is drilled at the plane projection mark; The diameter of the single-hole measuring well is not less than 8 cm, and the drilling depth is not less than 1.5 m. ; The magnetic gradient meter probe was lowered to the bottom of the well at a constant speed, and the vertical component magnetic induction intensity and depth data were collected simultaneously, with a sampling interval of no more than 0.05m.
7. The method for locating deeply buried pipelines based on magnetic gradient values as described in claim 1, characterized in that, The information acquisition step in step 1) includes: The magnetic inclination of the geomagnetic field is obtained based on the international geomagnetic reference field model or local geomagnetic station data. I And magnetic declination D ; A metal pipeline detector was used for on-site reconnaissance to preliminarily determine the approximate route and burial depth of the target pipeline, and to obtain its initial horizontal azimuth. .
8. The method for locating deeply buried pipelines based on magnetic gradient values as described in claim 3, characterized in that, Theoretical curve in the formula Take the estimated burial depth from the survey Or 10m.
9. A system for implementing the method for locating deeply buried pipelines based on magnetic gradient values as described in any one of claims 1-8, characterized in that, include, The information acquisition module is used to obtain the geomagnetic field parameters of the construction area and the initial horizontal azimuth of the target pipeline, and to calculate the effective magnetization inclination angle of the target pipeline in the radial plane perpendicular to the direction. The extreme distance calculation module is used to collect vertical magnetic gradient sequences in single-hole measurement wells near the target pipeline and form observation curves, extract the depth values corresponding to the extreme values from the observation curves, and calculate the extreme distance. The module for solving the absolute value of the horizontal distance is used to construct a theoretical relationship based on the preset pipeline magnetic field model, combined with the effective magnetization inclination angle and the extreme distance, and to obtain the absolute value of the horizontal distance between the target pipeline and the single-hole measuring well. The horizontal orientation symbol module is used to generate a theoretical curve of the vertical magnetic gradient based on the absolute value of the horizontal distance and the preset initial depth. The observed curve and the theoretical curve are compared for consistency in their morphological characteristics between extreme values. If they are consistent, the horizontal distance between the target pipeline position and the borehole is not negative; otherwise, the horizontal distance is negative. The burial depth inversion module is used to calculate the precise burial depth of the target pipeline based on the horizontal distance with positive and negative signs, the depth value corresponding to the extreme value, and the effective magnetization inclination angle.