A method for accurately locating pipeline defects based on gyroscopes and shielded geomagnetic fields

Abstract

The present invention proposes a method for accurately locating pipeline defects based on a gyroscope and a shielded geomagnetic field, which belongs to the field of long-distance oil and gas pipeline defect detection. The method includes two major steps: using a gyroscope to measure the rotation angle of the pipe cleaner, and cooperating with a magnetic flux leakage detection system to obtain the precise position of the pipeline defect; using a magnetometer to measure the shielded geomagnetic field in the pipeline to secondary determine the rotation angle, thereby correcting the gyroscope data. The present invention can directly use the magnetic field information in the pipeline to locate defects, avoiding interference from the geological environment, solving the problem of error accumulation of the gyroscope, and enhancing the positioning accuracy of long-distance oil and gas pipeline defects. At the same time, the method is low-cost and high-efficiency.

Description

Technical Field

[0001] The present invention relates to the field of defect detection, and in particular to a defect locating method which utilizes a gyroscope to locate the defect and utilizes a magnetometer to perform secondary determination of pipeline defects. Background Art

[0002] When long-distance oil and gas transmission is carried out, corrosion perforation, fatigue cracking and external force damage may cause minor defects in the oil and gas pipelines, especially the pipeline ring welding point has always been the weakest part of the pipeline. Cracks are likely to cause oil and gas leakage and lead to safety accidents. Therefore, it is necessary to conduct regular inspections and assessments of long-distance oil and gas pipelines. Magnetic leakage internal detection technology is currently the most widely used and mature technology because it has low requirements for the operating environment, does not require coupling, and is economical.

[0003] Magnetic flux leakage detection technology uses the changes in magnetic induction lines at pipeline defects to detect and quantify the nature and quality of defects. Existing pipeline defect positioning includes mileage wheel positioning and clock positioning. Among them, mileage wheel positioning is a major internal detection positioning method, which can obtain the distance from the defect detected by the magnetic flux leakage detector to the pipe mouth, thereby locating the defect to a certain pipeline section. However, due to the insufficient accuracy of the gyroscope, clock positioning, which can locate the defect to a specific point on the section, is generally not used in actual projects. The main application point of the gyroscope in the existing pipeline magnetic flux leakage internal inspection system is pipeline trajectory drawing. The reason is that the defect detection distance of long-distance oil and gas pipelines is too long, and the gyroscope error will continue to accumulate, resulting in erroneous results.

[0004] Therefore, finding a method to accurately locate pipeline defects that can eliminate gyroscope errors is of great significance to the operation and maintenance of oil and gas pipelines. Summary of the invention

[0005] When performing magnetic flux leakage detection of defects, since the detection distance of long-distance oil and gas pipelines is generally very long, the errors measured by gyroscopes will continue to accumulate. In order to overcome the above defects, the present invention proposes a method for indirectly measuring the rotation angle of the pig using a shielded geomagnetic field to correct the gyroscope error.

[0006] The present invention is achieved through the following technical solutions:

[0007] A pipeline defect detection method based on a gyroscope and a shielded geomagnetic field, the steps of which include:

[0008] Step A: Accurately locate the defect:

[0009] A1, using a gyroscope installed on the pig to measure the pig's rotation angle α;

[0010] A2, calculate the defect position by combining the rotation angle α measured in step A1 with the position of the Hall element in the magnetic flux leakage detection system;

[0011] Step B: calibrate the gyroscope data:

[0012] B1, install the three-axis gyroscope and the three-axis magnetometer on the pig and realize synchronous rotation;

[0013] B2, combining the local real-time geomagnetic field and the inherent shielding coefficient of the pipeline, decomposes the shielded geomagnetic field onto the pipeline coordinate axis;

[0014] B3, using a three-axis magnetometer to measure the magnetic field information in the pipeline when the pig rotates at an angle of α;

[0015] B4, according to the conversion relationship between the coordinate axes of the three-axis magnetometer and the coordinate axes of the pipeline, a set of equations is established to indirectly calculate the rotation angle α of the pipeline pig;

[0016] B5, by comparing the rotation angle indirectly measured by the three-axis magnetometer with the rotation angle directly measured by the gyroscope, the gyroscope data can be corrected.

[0017] Furthermore, in step A1, the main working principle of the gyroscope is to first use the gyroscope to measure the rotation angular velocity of the pipe cleaner, and then obtain the rotation angle α of the pipe cleaner after one integration;

[0018] Further, in step A2, there are 24 Hall elements in the magnetic flux leakage detection system, which are numbered 1 to 24, and the angles between the lines connecting adjacent Hall elements and the center O are equal, which is 15°; the specific position of the defect in a certain ring segment relative to the center O can be calculated using the following formula:

[0019] (y p ,z p )=(r p sin(α+β),r p cos(α+β))

[0020] In the formula, y p ,z p are the radial and vertical coordinates of the defect respectively; r p is the inner radius of the pipe at the defect; β is the angle between the Hall element numbered 1 and the Hall element numbered n that detects the defect in the rotation direction;

[0021] Furthermore, in step B2, the rectangular coordinate system Ox of the pipeline is set p y p z p , set the pipeline coordinate axis to (B px ,B py,B pz ), use the following formula to decompose the geomagnetic field Be:

[0022]

[0023] In the formula, e xp is parallel to the axis x p The unit vector, e yp is parallel to the y axis p The unit vector, e zp is parallel to the axis z p Unit vector of |B e | is the modulus of the geomagnetic field; δ is the geomagnetic field Be and x p y p The angle between the two planes; Φ is the geomagnetic field Be at x p y p Projection of the plane and x p The attenuation coefficient S1 is the ratio of the external magnetic field to the internal magnetic field along the radial direction of the pipeline; the attenuation coefficient S2 is the ratio of the external magnetic field to the internal magnetic field along the axial direction of the pipeline;

[0024] Further, in step B3, when the pig rotates at an angle of α, a three-axis magnetometer is used to measure the magnetic field in the pipeline. The magnetic field coordinates in the pipeline measured by the three-axis magnetometer are (B mx ,B my ,B mz );

[0025] Further, in step B4, the coordinate axes of the three-axis magnetometer and the axes of the three-axis gyroscope are initially set to be parallel in sequence; when the pig rotates at an angle of α, the value of α is indirectly calculated by the following formula:

[0026]

[0027] The solution is:

[0028]

[0029] In the formula, B mx ,B my ,B mz They are the coordinate values ​​of the radial, axial and vertical directions of the three-axis magnetometer respectively;

[0030] The beneficial effects brought by the present invention are:

[0031] The present invention adopts a three-axis magnetometer to measure the shielded geomagnetic field, indirectly obtains the rotation angle of the pipe cleaner, and corrects the measurement angle of the gyroscope, thereby solving the problem of error accumulation of the gyroscope. This method can also be used to solve the difficult problem of accurate positioning of defects in long-distance oil and gas pipelines. It is also an economical and efficient detection method that reduces pipeline maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of accurate detection of pipeline defects;

[0033] Figure 2 It is a decomposed diagram of the Earth's magnetic field;

[0034] Figure 3 It is a schematic diagram of magnetometer coordinates and pipeline coordinates; DETAILED DESCRIPTION

[0035] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0036] The present invention uses a gyroscope to measure the rotation angle of the pipe cleaner, and then combines the defect properties detected by the magnetic flux leakage detection system and the data of the odometer to locate the pipeline defect; then uses a three-axis magnetometer to measure the shielded geomagnetic field to indirectly calculate the rotation angle of the pipe cleaner; finally, the rotation angle measured by the gyroscope is compared and corrected with the rotation angle measured indirectly. The method includes two steps: accurately locating the defect and correcting the gyroscope data:

[0037] Step A: Accurately locate the defect:

[0038] A1, using a gyroscope installed on the pig to measure the pig's rotation angle α;

[0039] A2, calculate the defect position by combining the rotation angle α measured in step A1 with the position of the Hall element in the magnetic flux leakage detection system;

[0040] Step B: calibrate the gyroscope data:

[0041] B1, install the three-axis gyroscope and the three-axis magnetometer on the pig and realize synchronous rotation;

[0042] B2, combining the local real-time geomagnetic field and the inherent shielding coefficient of the pipeline, decomposes the shielded geomagnetic field onto the pipeline coordinate axis;

[0043] B3, using a three-axis magnetometer to measure the magnetic field information in the pipeline when the pig rotates at an angle of α;

[0044] B4, according to the conversion relationship between the coordinate axes of the three-axis magnetometer and the coordinate axes of the pipeline, a set of equations is established to indirectly calculate the rotation angle α of the pipeline pig;

[0045] B5, by comparing the rotation angle indirectly measured by the three-axis magnetometer with the rotation angle directly measured by the gyroscope, the gyroscope data can be corrected.

[0046] Step A1) Install the gyroscope on the pig, wherein the pig consists of two parts, the front end is the rotation angle measurement part of the pig, including the gyroscope and the magnetometer, and the rear end is the leakage magnetic detection system part of the pig, including the Hall element; wherein the gyroscope is coaxial with the pig and can rotate synchronously with the pig. When the pig rotates, the rotation angle α of the pig can be measured by the gyroscope, see Figure 1 , which includes a gyroscope (1), a three-axis magnetometer (2), a universal joint (3), a magnetic flux leakage detection system (4), a Hall element (5), and a long-distance pipeline (6);

[0047] Step A2) The rotation angle α measured in step A1 can be used to obtain the distance between the defect detected by the magnetic flux leakage detector and the pipe opening by the odometer wheel positioning method. The defect coordinates can be calculated relative to the position of the ring segment center 0 by combining the rotation angle α and the position of the Hall element that detects the defect. There are 24 Hall elements in the magnetic flux leakage detection system, which are numbered 1 to 24. The angles between the lines connecting adjacent Hall elements and the center O are equal, which is 15°. The specific position of the defect in a certain ring segment relative to the center O can be calculated using the following formula:

[0048] (y p ,z p )=(r p sin(α+β),r p cos(α+β))

[0049] In the formula, y p ,z p are the radial and vertical coordinates of the defect respectively; r p is the inner radius of the pipe at the defect; β is the angle between the Hall element numbered 1 and the Hall element numbered n that detects the defect in the rotation direction;

[0050] Step B: Correct the gyroscope data:

[0051] Step B1) installing the three-axis magnetometer on the pig, and the three-axis magnetometer is coaxial with the pig and can rotate synchronously with the pig;

[0052] Step B2) Use a three-axis magnetometer to measure the shielded geomagnetic field Be in the pipeline, and decompose the shielded geomagnetic field onto the pipeline coordinate axis, see Figure 2 The rectangular coordinate system of the pipeline is Oxp y p z p , the coordinate axis of the geomagnetic field decomposed into the pipeline is (B px ,B py ,B pz ), the geomagnetic field Be can be decomposed using the following formula:

[0053]

[0054] In the formula, e xp is parallel to the axis x p The unit vector, e yp is parallel to the y axis p The unit vector, e zp is parallel to the axis z p Unit vector of |B e | is the modulus of the geomagnetic field; δ is the geomagnetic field Be and x p y p The angle between the two planes; Φ is the geomagnetic field Be at x p y p Projection of the plane and x p The attenuation coefficient S1 is the ratio of the external magnetic field to the internal magnetic field along the radial direction of the pipeline; the attenuation coefficient S2 is the ratio of the external magnetic field to the internal magnetic field along the axial direction of the pipeline;

[0055] Step B3) When the pig rotates at an angle of α, a three-axis magnetometer is used to measure the magnetic field information in the pipeline. The magnetic field coordinates in the pipeline measured by the three-axis magnetometer are (B mx ,B my ,B mz );

[0056] Step B4) By measuring the magnetic field information in the pipeline in step B3, the rotation angle α of the pipeline pig can be indirectly calculated, see Figure 3 Initially, the coordinate axes of the three-axis magnetometer and the axes of the three-axis gyroscope are set to be parallel. When the pig rotates at an angle of α, the value of α is indirectly calculated by the following formula:

[0057]

[0058] The solution is:

[0059]

[0060] In the formula, B mx ,B my ,B mz are the coordinate values ​​of the radial, axial and vertical directions of the three-axis magnetometer respectively; B px ,B py ,B pzThey are the coordinate values ​​of the radial, axial and vertical directions of the pipeline decomposed from the geomagnetic field;

[0061] In the formula, since the calibration of the attenuation coefficient requires the known size and direction of the pipeline, in practice, the various parameters of the long-distance oil and gas pipelines put into use are basically determined, and the technology for determining the direction of the pipeline in engineering is also very mature, so the calculation of the rotation angle can be determined;

[0062] Step B5) By comparing the rotation angle measured by the gyroscope in step A1 with the rotation angle indirectly measured by the magnetometer in step B4, the angle measured by the gyroscope can be corrected to prevent the serious consequences caused by the wrong rotation angle due to the accumulation of gyroscope errors.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for accurately locating pipeline defects based on a gyroscope and a shielded geomagnetic field, the steps comprising: Step A: Accurately locate the defect: A1, using a gyroscope installed on the pig to measure the pig's rotation angle α; A2, calculating the defect position by combining the rotation angle α measured in step A1 and the position of the Hall element in the magnetic flux leakage detection system; Step B: calibrate the gyroscope data: B1, install the three-axis gyroscope and the three-axis magnetometer on the pig and realize synchronous rotation; B2, using a three-axis magnetometer to measure the shielded geomagnetic field Be inside the pipeline, combined with the local real-time geomagnetic field, the direction of the pipeline and the inherent attenuation coefficient, the shielded geomagnetic field is decomposed onto the pipeline coordinate axis; B3, using a three-axis magnetometer to measure the magnetic field information in the pipeline when the pig rotates at an angle of α; B4, according to the conversion relationship between the coordinate axes of the three-axis magnetometer and the coordinate axes of the pipeline, a set of equations is established to indirectly calculate the rotation angle α of the pig; B5, comparing the rotation angle indirectly measured by the three-axis magnetometer with the rotation angle directly measured by the gyroscope, and correcting the gyroscope data; In step B2, set the rectangular coordinate system of the pipeline to Ox p y p z p , set the coordinate axis of the geomagnetic field decomposed on the pipeline to (B px ,B py ,B pz ), B px ,B py ,B pz The geomagnetic field is decomposed into the radial, axial and vertical coordinate values ​​of the pipeline respectively, and the geomagnetic field Be is decomposed using the following formula: In the formula, e xp is parallel to the axis x p The unit vector, e yp is parallel to the y axis p The unit vector, e zp is parallel to the axis z p Unit vector of |B e | is the modulus of the geomagnetic field; δ is the geomagnetic field Be and x p y p The angle between the two planes; Φ is the geomagnetic field Be at x p y p Projection of the plane and x p The attenuation coefficient S1 is the ratio of the external magnetic field to the internal magnetic field along the radial direction of the pipeline; the attenuation coefficient S2 is the ratio of the external magnetic field to the internal magnetic field along the axial direction of the pipeline; In step B4, the three-axis magnetometer coordinate axes (B mx ,B my ,B mz ) is parallel to each axis of the three-axis gyroscope. When the pig rotates at an angle of α, the value of α is indirectly calculated by the following formula: The solution is: In the formula, B mx ,B my ,B mz They are the radial, axial and vertical coordinate values ​​of the three-axis magnetometer respectively.

Images