Underground orientation direction judgment method based on giant magnetoresistance effect

Abstract

The invention belongs to the technical field of logging, and discloses an underground orientation direction judgment method based on a giant magnetoresistance effect, and a logging instrument printed circuit board is provided with a giant magnetoresistance sensor; the output voltage Uout + and the output voltage Uout-of the giant magnetoresistive sensor are obtained; and according to the output voltages Uout + and Uout-and in combination with a preset relation curve corresponding to the output voltage of the giant magnetoresistive sensor and the azimuth angle of the underground instrument, obtaining the azimuth angle of the underground instrument. The invention aims to judge the orientation, the drilling mode and the rotating speed of the underground instrument.

Description

Technical Field

[0001] The invention belongs to the technical field of well logging, and in particular relates to a method for determining downhole orientation based on giant magnetoresistance effect. Background Art

[0002] Measurement while drilling (MWD) refers to the process of measuring certain information near the drill bit and transmitting the attitude information of the downhole instrument to the ground without interrupting the normal drilling operation. The attitude information includes the well inclination angle, azimuth and tool face angle. The measurement of these data can accurately and in real time determine the current wellbore trajectory and drill bit position, ensure the quality of the wellbore and adjust the next drilling direction. At present, fluxgate magnetometers are widely used at home and abroad to measure the magnetic field strength component at the location of the downhole instrument, calculate the azimuth of the downhole instrument, and use accelerometers to measure the gravity field at the location of the downhole instrument to calculate the inclination angle and tool face angle of the downhole instrument. However, fluxgate magnetometers are expensive, need to be returned to the factory for calibration regularly, and occupy a large space. This patent uses a giant magnetoresistance sensor to measure the magnetic field strength component at the location of the downhole instrument, and then solves the azimuth of the downhole instrument. In 1988, Professor Fert's research group at the Department of Physics at the University of Paris, France, first discovered the giant magnetoresistance (GMR) effect in Fe / Cr multilayer films. Multilayer film giant magnetoresistance is a layered structure made of alternating non-magnetic metal layers and ferromagnetic metal layers with a thickness of several nanometers. The magnetic moments of atoms in the same magnetic layer are in the same direction, while the magnetic moments of adjacent magnetic layers are antiparallel. The external magnetic field can change the magnetic moments of the magnetic layers. When the magnetic moments of the two magnetic layers are parallel to each other, the scattering of electrons related to spin is minimal, and the giant magnetoresistance (GMR) sensor has the lowest resistance state. When the magnetic moments of the two layers are antiparallel, the scattering related to spin is the strongest, and the giant magnetoresistance (GMR) sensor has the highest resistance state. A slight change in the magnetic field can cause a significant change in resistivity. Since the magnetic field vector of any point in the near-Earth space corresponds to the geographical longitude and latitude of the point and the height from the center of the Earth, under the action of the Earth's magnetic field, the orientation of the downhole instrument where the giant magnetoresistance sensor is located changes, causing the internal resistance value of the sensor to change, and the corresponding output voltage also changes. This characteristic is used to convert the azimuth measurement of the downhole instrument into the output voltage measurement of the giant magnetoresistance sensor, and the azimuth of the downhole instrument is calculated in real time. This method has a simple circuit structure, small space, high sensitivity, stable operation, no need for scale and low cost, and on this basis, it can also realize the judgment of the drilling state (sliding / compound) and rotation speed of the downhole instrument.

[0003] The Chinese patent with the patent number CN102174886B discloses a real-time detection device and method for the depth of coalbed methane horizontal directional drilling. It specifically discloses that the energized coil is powered to generate a magnetic field, and the magnetoresistive sensor detects the change in magnetoresistive resistance to determine whether the drill rod is in the advancing or retreating state, but it cannot determine the direction. The underground directional direction determination method based on the giant magnetoresistive effect has not been used in the field of well logging. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention proposes a method for determining downhole orientation based on the giant magnetoresistance effect and establishes a mathematical model for measuring the attitude of the geomagnetic field sensor, with the aim of obtaining the azimuth, drilling mode and instrument rotation speed of the downhole instrument in real time.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0006] A method for determining downhole orientation based on giant magnetoresistance effect, wherein a giant magnetoresistance sensor is provided on the well logging instrument;

[0007] Obtain the output voltage U of the giant magnetoresistance sensor out+ and U out- ;

[0008] According to the output voltage U out+ and U out- , and combined with the preset relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth of the downhole tool, the azimuth of the downhole tool is obtained.

[0009] Furthermore, the preset relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth angle of the downhole tool includes: the relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth angle of the downhole tool when the downhole tool is at different inclination angles.

[0010] Furthermore, the well logging instrument is also provided with a voltage comparator connected to the giant magnetoresistance sensor;

[0011] The voltage comparator is used to compare the output voltage U out+ and U out- Make comparisons;

[0012] The drilling mode and rotation speed of the downhole instrument are obtained according to the voltage output by the voltage comparator.

[0013] Further, the obtaining the rotation speed of the downhole tool according to the voltage output by the voltage comparator includes:

[0014] generating a square wave signal according to the voltage output by the voltage comparator;

[0015] Obtaining the number of positive pulses corresponding to one rotation of the downhole tool according to the square wave signal;

[0016] Obtaining a positive pulse duty ratio according to the number of positive pulses;

[0017] According to the positive pulse duty cycle and in combination with the preset corresponding relationship between the positive pulse duty cycle and the rotation speed, the rotation speed of the downhole tool is obtained in real time.

[0018] Furthermore, the voltage comparator is connected to the giant magnetoresistance sensor via a conditioning circuit.

[0019] Furthermore, the giant magnetoresistance sensor is welded on a printed circuit board, and the printed circuit board is mounted on a downhole instrument.

[0020] Furthermore, the giant magnetoresistance sensor adopts AAH002-02 giant magnetoresistance sensor, and the voltage comparator adopts rail-to-rail high-speed voltage comparator TS3021H.

[0021] Furthermore, the operating voltage of the giant magnetoresistance sensor is 5V.

[0022] Furthermore, the sensitivity of the giant magnetoresistance sensor is 11mV / Gs to 18mV / Gs.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] The present invention provides a method for determining downhole orientation based on the giant magnetoresistance effect. A giant magnetoresistance sensor is provided on a downhole instrument. By obtaining the output voltage U out+ and U out- , combined with the corresponding relationship curve between output voltage and azimuth, the azimuth of the downhole instrument can be obtained in real time. In different geographical locations, the corresponding external magnetic field (geomagnetic field) vector is different, which causes the output voltage of the giant magnetoresistive sensor to change. By analyzing and calculating the voltage, the azimuth of the downhole instrument can be obtained.

[0025] The downhole directional orientation judgment method based on the giant magnetoresistance effect proposed in the present invention can accurately and real-time obtain downhole instrument drilling engineering parameters and can judge the instrument drilling status (sliding / compound), which reduces costs, improves efficiency, and has good market prospects.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the specific implementation modes of the present invention, the drawings required for use in the description of the specific implementation modes will be briefly introduced below. Obviously, the drawings described below are some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 This is a schematic diagram of the internal structure of the giant magnetoresistive sensor AAH002-02 according to an embodiment of the present invention;

[0029] Figure 2 This is a graph showing the output and temperature performance of the giant magnetoresistance sensor AAH002-02 according to an embodiment of the present invention;

[0030] Figure 3 The sensitive axis direction of the giant magnetoresistance sensor AAH002-02 of the embodiment of the present invention;

[0031] Figure 4 This is a flowchart of a method for determining a downhole instrument drilling mode based on the giant magnetoresistance effect according to an embodiment of the present invention;

[0032] Figure 5 A geodetic coordinate system established for an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the installation method and initial position of the AAH002-02 giant magnetoresistance sensor when the instrument is perpendicular to the ground according to an embodiment of the present invention;

[0034] Figure 7 This is a differential voltage output curve of the giant magnetoresistance sensor when the instrument according to the embodiment of the present invention is perpendicular to the ground;

[0035] Figure 8 The giant magnetoresistance sensor U is when the instrument of the embodiment of the present invention is perpendicular to the ground. out Output curve;

[0036] Fig. 9 U is the voltage output curve when the instrument is perpendicular to the ground out MATLAB fitting results;

[0037] Fig.10 This is a waveform diagram of the voltage output by the voltage comparator when the instrument according to the embodiment of the present invention is perpendicular to the ground;

[0038] Fig.11 This is a differential voltage output curve of the giant magnetoresistance sensor when the inclination angle of the instrument according to the embodiment of the present invention is 30°;

[0039] Fig.12 The giant magnetoresistance sensor U of the instrument according to the embodiment of the present invention when the inclination angle is 30° out Output curve;

[0040] Fig.13 The voltage output curve U is when the instrument is tilted at 30° out MATLAB fitting results;

[0041] Fig.14 This is a waveform diagram of the voltage output of the voltage comparator when the instrument according to the embodiment of the present invention is tilted 30°;

[0042] Fig.15 This is a differential voltage output curve of the giant magnetoresistance sensor when the inclination angle of the instrument in the embodiment of the present invention is 45°;

[0043] Fig.16 The giant magnetoresistance sensor U of the instrument according to the embodiment of the present invention when the inclination angle is 45° out Output curve;

[0044] Fig.17 The voltage output curve U is at a 45° inclination angle of the instrument. out MATLAB fitting results;

[0045] Fig.18 This is a waveform diagram of the voltage output of the voltage comparator when the instrument according to the embodiment of the present invention is tilted 45°;

[0046] Fig.19 This is a differential voltage output curve of the giant magnetoresistance sensor when the inclination angle of the instrument according to the embodiment of the present invention is 60°;

[0047] Fig. 20 The giant magnetoresistance sensor U of the instrument according to the embodiment of the present invention when the inclination angle is 60° out Output curve;

[0048] Fig.21 The voltage output curve U is at an instrument tilt angle of 60° out MATLAB fitting results;

[0049] Fig. 22 This is a waveform diagram of the voltage output of the voltage comparator when the instrument according to the embodiment of the present invention is tilted 60°;

[0050] Fig.23 This is a schematic diagram of the installation method and initial position of the AAH002-02 giant magnetoresistance sensor when the instrument is horizontal on the ground according to an embodiment of the present invention;

[0051] Fig.24 This is a differential voltage output curve of the giant magnetoresistance sensor when the instrument according to the embodiment of the present invention is horizontally placed on the ground and initially faces south;

[0052] Fig.25 The giant magnetoresistance sensor U is shown in the embodiment of the present invention when the instrument is horizontal on the ground and initially faces south. out curve;

[0053] Fig.26 The voltage output curve U is when the instrument is horizontal to the ground and initially faces south. out MATLAB fitting results;

[0054] Fig. 27 This is a waveform diagram of the voltage output by the voltage comparator when the instrument according to the embodiment of the present invention is horizontally placed on the ground and initially faces south;

[0055] Fig.28 It is a differential voltage output curve of the giant magnetoresistance sensor when the instrument of the embodiment of the present invention is horizontal on the ground and initially faces west;

[0056] Fig.29 The giant magnetoresistance sensor U is shown in the embodiment of the present invention when the instrument is horizontal on the ground and initially faces west. out Output curve;

[0057] Fig.30 The voltage output curve U is when the instrument is horizontal to the ground and initially faces west. out MATLAB fitting results;

[0058] Fig.31 This is a waveform diagram of the voltage output by the voltage comparator when the instrument according to the embodiment of the present invention is horizontally located on the ground and initially faces west. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] The present invention proposes a method for determining downhole orientation based on the giant magnetoresistance effect, wherein a giant magnetoresistance sensor is provided on the downhole instrument;

[0061] Get the output voltage U of the giant magnetoresistance sensor out+ and U out- ;

[0062] Please refer to Figure 7 , Fig.11 , Fig.15 , Fig.19 , Fig.24 and Fig.28 As shown, according to the output voltage U out+ and U out- , combined with the preset giant magnetoresistance sensor output voltage U out The relationship curve corresponding to the azimuth of the downhole instrument is used to obtain the azimuth of the downhole instrument. The downhole instrument drilling mode (sliding / compound) and the downhole instrument speed are determined according to the voltage comparator output waveform and the positive pulse duty cycle. Among them, sliding drilling means that the drill does not rotate, and drills directly in the predetermined direction with the drilling pressure, and compound drilling means that the drill rotates. It should be understood that the rotation angle in the figure is the azimuth.

[0063] The multilayer giant magnetoresistance is a layered structure made of alternating non-magnetic metal layers and ferromagnetic metal layers with a thickness of several nanometers. In the absence of an external magnetic field, the magnetic moment directions of atoms in the same magnetic layer are consistent, and the magnetic moments of adjacent magnetic layers are antiparallel. At this time, the resistance value is the largest. When there is an external magnetic field, the magnetic moment directions of all magnetic layers are consistent, and the resistance value is the smallest. When the external magnetic field vector is different, the sensor resistance value is different. The giant magnetoresistance sensor is made using the giant magnetoresistance effect of magnetic materials. The present invention is based on the one-to-one correspondence between the orientation and the geomagnetic field vector. When the orientation of the giant magnetoresistance sensor changes, its internal magnetic moment also changes under the action of the geomagnetic field, thereby causing the internal resistance value of the giant magnetoresistance sensor to change, and then the output voltage of the sensor changes, and the orientation information of the downhole instrument is converted into a voltage signal for measurement, which can realize the orientation judgment of the downhole instrument.

[0064] It should be noted that the relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth angle of the downhole instrument was established in advance through a large number of experiments. The relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth angle of the downhole instrument: the relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth angle of the downhole instrument when the downhole instrument is at different inclination angles.

[0065] In one embodiment, a voltage comparator electrically connected to the giant magnetoresistance sensor is also provided on the downhole instrument. For example, the voltage comparator is connected to the giant magnetoresistance sensor via a conditioning circuit. The method for determining the drilling mode of the downhole instrument based on the giant magnetoresistance effect also includes:

[0066] The output voltage U is measured by a voltage comparator. out+ and U out- Make comparisons;

[0067] The rotation speed of the downhole tool is obtained according to the voltage output by the voltage comparator, specifically:

[0068] generating a square wave signal according to the voltage output by the voltage comparator;

[0069] Please refer to Fig.10 , Fig.14 , Fig.18 , Fig. 22 , Fig. 27 and Fig.31 As shown, the number of positive pulses corresponding to one rotation of the downhole tool is obtained according to the square wave signal;

[0070] The duty ratio of the positive pulse is obtained according to the number of positive pulses;

[0071] According to the positive pulse duty cycle, combined with the preset corresponding relationship between the positive pulse duty cycle and the rotation speed, the rotation speed of the downhole tool is obtained.

[0072] Combination Figure 6 and Fig.23As shown, the giant magnetoresistive sensor 1 is welded on a printed circuit board 2 , and the printed circuit board 2 is mounted on a downhole instrument 3 .

[0073] The present invention changes the traditional downhole instrument's use of fluxgate magnetometers to detect geomagnetic field signals, and provides a new downhole instrument azimuth measurement method, which is low-cost, high-accuracy, small in space, and can be welded on a printed circuit board. The feasibility of the measurement method has been verified through experiments, providing a new measurement method for real-time acquisition of downhole instrument drilling engineering parameters.

[0074] Preferably, the giant magnetoresistance sensor adopts AAH002-02, which is a giant magnetoresistance (GMR) sensor developed by NVE. The device has a measurement range of -3Gs to +3Gs (geomagnetic field range +0.6Gs to -0.6Gs), and the sensor measurement range meets the geomagnetic field range. Sensitivity: 11mV / Gs to 18mV / Gs, working voltage: 5V, and its internal structure is as follows Figure 1 AAH series devices provide omnipolar output, with output in both the positive and negative directions along the sensitive axis. Figure 3 As shown, when the standard sensitive axis of AAH002-02 coincides with the magnetic north pole of the geomagnetic field, the resistance value is the smallest and the output voltage is the largest; when the angle between the sensitive axis and the geomagnetic north pole is 180°, the resistance value is the largest and the output voltage is the smallest, and the output voltage of the giant magnetoresistance sensor changes with the change of the orientation.

[0075] AAH002-02 is internally composed of four identical giant magnetoresistors (GMRs) forming a Wheatstone bridge R1=R2=R3=R4=R, where R1 and R2 are covered and shielded by a material with high magnetic permeability (Permalloy layer), and their resistance values ​​have no response to external magnetic fields, so R1=R2=R; the resistance values ​​of R3 and R4 are affected by the external magnetic field. When the sensor is in an external changing magnetic field environment, the resistance value changes by ΔR, R3=R4=R-ΔR, ΔR is the resistance change of a single GMR when the magnetic induction intensity of the external magnetic field is B, and when the direction of the external magnetic field is the same as the direction of the magnetic moment of the GMR sensor, ΔR is positive, otherwise it is negative; U in is the system power supply voltage, generally 5V, and the output voltage ΔU is:

[0076]

[0077]

[0078]

[0079] Since the giant magnetoresistance ΔR and the magnetic field strength H are in a linear relationship, then:

[0080] ΔR=kH (4)

[0081] The downhole sensor is powered by 5V, and the output voltage ΔU is:

[0082]

[0083] In the formula, k and R are fixed constants. Obviously, within the linear range, the output voltage is proportional to the magnetic field strength.

[0084] The signal processing circuit amplifies and filters the output voltage of the giant magnetoresistance sensor to obtain the final output voltage signal. When the external magnetic field intensity is 0, U out =0V, when the external magnetic field changes, the output voltage of the giant magnetoresistance sensor is U out The waveform is as Figure 2 shown.

[0085] Figure 2 Four measurement results at -40℃, 25℃, 85℃ and 125℃ are shown respectively. When the external magnetic field strength is 0, ΔU is 0V. As the external magnetic field strength changes, the output voltage of the giant magnetoresistance sensor changes. Figure 2 The change shown. Therefore, it is feasible to use giant magnetoresistance sensor to measure the change of weak magnetic field strength. Due to the existence of hysteresis, when the magnetic field strength increases from zero, the magnetization intensity increases to a certain value. At this time, if the magnetic field is slowly reduced, the magnetization intensity does not return to its original state along the original change curve, but changes along another curve.

[0086] When the earth's magnetic field is between -0.5Oe and +0.5Oe, when the downhole instrument where the giant magnetoresistive sensor is located changes its orientation, the giant magnetoresistive sensor outputs a voltage U out+ and U out- changes; when the giant magnetoresistance sensor is stationary, U out+ and U out- The TS3021H rail-to-rail high-speed comparator is used to out+ and U out- By comparison, the drilling mode (compound / sliding) of the downhole tool can be determined and the rotation speed can be obtained. When the downhole tool rotates, the comparator output voltage changes once. When the downhole tool continues to rotate, the comparator outputs a square wave signal. The tool rotation speed can be calculated based on the positive pulse duty cycle of the square wave signal.

[0087] In this embodiment, the geodetic coordinate system is established as follows: Figure 5 As shown in the figure, a three-dimensional coordinate system is formed with the gravity direction as the vertical direction (Z axis), the horizontal plane facing north (X axis) and east (Y axis), AB is the axial direction of the downhole instrument, OB is the projection of the downhole instrument on the horizontal plane, the angle β between OB and the magnetic north of the earth is the azimuth, and the acute angle α between the downhole instrument and the vertical plane is the inclination angle.

[0088] In this embodiment, the schematic diagram of the installation direction of the AAH002-02 giant magnetoresistive sensor on the printed circuit board is as follows: Figure 6 As shown in the figure, the printed circuit board is installed on the downhole instrument frame. When the sensitive axis direction of the giant magnetoresistive sensor coincides with the north pole of the geomagnetic field, the sensor output voltage is maximum. The operating temperature of this series of devices is -50℃~150℃, which can meet the high temperature working requirements of downhole. The working process is as follows Figure 4 shown.

[0089] like Figure 6 As shown, the instrument is perpendicular to the ground plane, the inclination angle is 0°, and the power supply voltage is 5V. out- and U out+ The voltage is shown in Table 1, U out- and U out+ The voltage output curve is as follows Figure 7 As shown. The giant magnetic sensor rotates one circle, U out+ The maximum value corresponds to the geomagnetic South Pole, and the minimum value corresponds to the geomagnetic North Pole; out- The minimum value corresponds to the geomagnetic South Pole, and the maximum value corresponds to the geomagnetic North Pole. The test conditions are: 34°13′49″N, 108°58′9″E, 418.7m above sea level, and air pressure 968.5hPa.

[0090] Table 1 Voltage output when the instrument is perpendicular to the ground and the angle between it and the earth's magnetic field changes

[0091]

[0092]

[0093] U out =U out+ -U out- , U out The output curve is as follows Figure 8 shown.

[0094] Use MATLAB to perform Fourier curve fitting to obtain the azimuth angle x and U out Functional relationship of the measurement point, R 2 The value is 0.99944, and the fitted image is Fig. 9 , the fitting result is:

[0095] U out =0.0198-0.0248cos(0.0181x)-0.0032sin(0.0181x) (6)

[0097] When the instrument is perpendicular to the ground plane, the inclination angle is 0°. When the downhole instrument rotates one circle, the output voltage duty cycle of the comparator is about 0.72T, where T is the time it takes for the instrument to rotate one circle. The voltage output curve is as follows: Fig.10As shown, the downhole tool speed can be obtained according to the duty cycle.

[0098] In one embodiment, when the inclination angle is 30°, the installation method and position of the AAH002-02 giant magnetoresistance sensor remain unchanged, and the output voltage is as shown in Table 2, U out+ and U out- The voltage output curve is as follows Fig.11 As shown, U out =U out+ -U out- , U out The output curve is as follows Fig.12 shown.

[0099] Table 2 Sensor output voltage when the downhole tool inclination angle is 30°

[0100]

[0101]

[0102] Use MATLAB to perform Fourier curve fitting to obtain the azimuth angle x and U out Functional relationship of the measurement point, R 2 The value is 0.99099, and the fitted image is Fig.13 As shown, the fitting results are:

[0103] U out =0.0013+0.0224cos(0.0161x)-0.0085sin(0.0161x)+0.0140cos(0.0322x)-0.0091sin(0.0322x) (7)

[0105] The comparator output waveform is as follows: Fig.14 As shown, when the inclination angle is 30°, the duty cycle of the comparator output voltage is about 0.25×T, where T is the time it takes for the downhole tool to rotate one circle. The rotation speed of the downhole tool can be determined based on the duty cycle.

[0106] In one embodiment, when the downhole tool is inclined at 45°, the installation method and position of the AAH002-02 giant magnetoresistance sensor remain unchanged, and the output voltage is as shown in Table 3, U out+ and U out- The voltage output curve is as follows Fig.15 As shown, U out =U out+ -U out- , U out The output curve is as follows Fig.16 shown.

[0107] Table 3 Sensor output voltage when the downhole instrument inclination angle is 45°

[0108]

[0109]

[0110] Use MATLAB to perform Fourier curve fitting to obtain the azimuth angle x and U out The functional relationship of R 2 The value is 0.87341, and the fitted image is Fig.17 , the fitting result is:

[0111] U out =-0.0005-0.0081cos(0.018x)-0.0033sin(0.018x)-0.0071sin(0.36x)-0.0071cos(0.054x)-0.0035sin(0.054x) (8)

[0113] The comparator output voltage is Fig.18 As shown, the inclination angle is 45°, and the duty cycle of the comparator output voltage is about 0.39×T, where T is the time it takes for the downhole tool to rotate one circle. The tool speed can be obtained based on the positive pulse duty cycle.

[0114] In one embodiment, when the inclination angle is 60°, the installation method and position of the AAH002-02 giant magnetoresistance sensor remain unchanged, and the output voltage is as shown in Table 4, U out+ and U out- The voltage output curve is as follows Fig.19 As shown, U out =U out+ -U out- , U out The output curve is as follows Fig. 20 shown.

[0115] Table 4 Sensor voltage output when the downhole tool inclination angle is 60°

[0116]

[0117]

[0118] Use MATLAB to perform Fourier curve fitting to obtain the azimuth angle x and U out The functional relationship of R 2 The value is 0.97582, and the fitted image is Fig.21 , the fitting result is:

[0119] U out=0.0285-0.0152cos(0.0177x)+0.0234sin(0.0177x)+0.0097cos(0.0354x)+0.0097sin(0.0354x)+0.0045cos(0.0531x)-0.004sin(0.0531x) (9)

[0121] The comparator output voltage is Fig. 22 As shown, when the downhole tool has an inclination angle of 60°, the duty cycle of the comparator output voltage is about 0.56×T, where T is the time it takes for the downhole tool to rotate one circle. The rotation speed can be obtained based on the positive pulse duty cycle.

[0122] In one embodiment, the instrument is placed horizontally on the ground plane, and the AAH002-02 giant magnetoresistance sensor is installed as follows: Fig.23 As shown, when the clockwise rotation is 360° and the supply voltage is 5V, U out+ and U out- The voltage is shown in Table 5, U out+ and U out- The voltage output curve is as follows Fig.24 As shown, U out =U out+ -U out- , U out The output curve is as follows Fig.25 shown.

[0123] Table 5 Sensor voltage output when the instrument is horizontal to the ground

[0124]

[0125]

[0126] Use MATLAB to perform Fourier curve fitting to obtain the azimuth angle x and U out+ Functional relationship of the measurement point, R 2 The value is 0.98902, such as Fig.26 As shown, the fitting results are:

[0127] U out+ =0.0131-0.0114cos(0.0169x)-0.0187sin(0.0169x) (10)

[0128] The voltage comparator output waveform is as follows: Fig. 27 As shown, when the instrument is horizontal and facing west, the output voltage duty cycle is about 0.61×T, where T is the time it takes for the instrument to make one rotation.

[0129] In one embodiment, the instrument is placed horizontally on the ground plane, and the initial direction is southward and then rotated 360° clockwise. The output voltage changes are shown in Table 6 below: out+ and U out- The voltage output curve is as follows Fig.28 As shown, U out =U out+ -U out- , U out The output curve is as follows Fig.29 shown.

[0130] Table 6 Sensor voltage output when the instrument is horizontal to the ground

[0131]

[0132]

[0133] Use MATLAB to perform Fourier curve fitting to obtain the azimuth angle x and U out Functional relationship of the measurement point, R 2 The value is 0.99715, such as Fig.30 As shown, the fitting results are:

[0134] U out =0.0179-0.0188cos(0.0167x)+0.0049sin(0.0167x) (11)

[0135] The comparator output waveform is as follows: Fig.31 As shown, when the instrument is horizontal and facing south, the output voltage duty cycle is about 0.83×T, T is the time for the instrument to rotate one circle, and according to the output voltage waveform, it can be judged that the current downhole instrument is in compound drilling. In the description of the present invention, it should be understood that the terms "upper", "lower", "bottom", "inside", "outside" and the like indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0136] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0137] In the present invention, unless otherwise clearly specified and limited, the terms "connected", "connection" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0138] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0139] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0140] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for determining downhole orientation based on giant magnetoresistance effect, characterized in that: The logging instrument is equipped with a giant magnetoresistance sensor; Obtain the output voltage U of the giant magnetoresistance sensor out+ and U out- ; According to the output voltage U out+ and U out- , and combined with the preset relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth of the downhole tool, the azimuth of the downhole tool is obtained.

2. A method for determining downhole orientation based on giant magnetoresistance effect according to claim 1, characterized in that: The preset relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth angle of the downhole tool includes: the relationship curve between the output voltage of the giant magnetoresistance sensor and the azimuth angle of the downhole tool when the downhole tool has different inclination angles.

3. The method for determining downhole orientation based on giant magnetoresistance effect according to claim 1, characterized in that: The well logging instrument is also provided with a voltage comparator connected to the giant magnetoresistance sensor; The voltage comparator is used to compare the output voltage U out+ and U out- Make comparisons; The drilling mode and rotation speed of the downhole instrument are obtained according to the voltage output by the voltage comparator.

4. A method for determining downhole orientation based on giant magnetoresistance effect according to claim 3, characterized in that: The step of obtaining the rotation degree of the downhole tool according to the voltage output by the voltage comparator comprises: generating a square wave signal according to the voltage output by the voltage comparator; Obtaining the number of positive pulses corresponding to one rotation of the downhole tool according to the square wave signal; Obtaining a positive pulse duty ratio according to the number of positive pulses; According to the positive pulse duty cycle and in combination with the preset corresponding relationship between the positive pulse duty cycle and the rotation speed, the rotation speed of the downhole tool is obtained in real time.

5. The method for determining downhole orientation based on giant magnetoresistance effect according to claim 3, characterized in that: The voltage comparator is connected to the giant magnetoresistance sensor through a conditioning circuit.

6. The method for determining downhole orientation based on giant magnetoresistance effect according to claim 1, characterized in that: The giant magnetoresistance sensor is integrated on a printed circuit board, and the printed circuit board is installed on a well logging instrument.

7. The method for determining downhole orientation based on giant magnetoresistance effect according to claim 1, characterized in that: The giant magnetoresistance sensor adopts the AAH002-02 giant magnetoresistance sensor, and the voltage comparator adopts the rail-to-rail high-speed voltage comparator TS3021H.

8. A method for determining downhole orientation based on giant magnetoresistance effect according to claim 7, characterized in that: The operating voltage of the giant magnetoresistance sensor is 5V.

9. A method for determining downhole orientation based on giant magnetoresistance effect according to claim 8, characterized in that: The sensitivity of the giant magnetoresistance sensor is 11mV / Gs to 18mV / Gs.

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