Gravity high edge and mass high edge measuring device and method based on transient electromagnetic method

Abstract

The invention discloses a device and a method for measuring a gravity high edge and a mass high edge based on a transient electromagnetic method. The method comprises the following steps: uniformly winding an optical fiber on the outer side of a sleeve; the annular array probe is arranged on the surface of the transmitting probe; the transmitting probe is connected with the transmitting circuit, the transmitting circuit supplies a square wave excitation signal to the transmitting probe, and the annular receiving probe receives a direct electromagnetic signal and an eddy current signal around an optical fiber, amplifies the signals and then transmits the signals to the master control circuit for acquisition and processing; the annular array probe, the transmitting probe, the transmitting circuit and the main control circuit are connected and then move in the sleeve; the accelerometer is arranged on the outer side of the transmitting probe. The gravity high edge and the quality high edge can be recognized through the annular array probe composed of the accelerometer and the sensor, too many complex electromagnetic compatibility problems are not involved in hardware, convenience is provided for instrument maintenance, and the device has the advantages of being high in performance and easy to maintain, is practical in the field of oil exploration and can efficiently execute detection tasks.

Description

Technical Field

[0001] The invention belongs to the technical field of target detection of petroleum geological exploration instruments, and relates to a device and method for measuring gravity high side and mass high side based on transient electromagnetic method. Background Art

[0002] Well section perforation is an essential production process for oil and gas production. In the case of blind shooting, it is very easy to cause damage to the optical cable close to the outer wall of the casing, which seriously limits the application scope of the optical cable laid outside the casing. However, although the existing outside-pipe optical fiber detection technology is relatively intuitive, it is impossible to observe the outside-pipe optical cable through the casing wall because its detection distance is limited to the inner wall of the casing. Secondly, the current detection technology will have a huge error when there are other metal substances on the pipe wall or the casing wall is damaged or defective, and it is impossible to accurately judge the position of the outside-pipe optical cable in the downhole casing. Then its perforation operation will easily damage the outside-pipe optical cable. In order to accurately identify the position of the downhole optical cable, the patent "A MOT-1 optical fiber receiving and transmitting system" proposes to obtain the specific position of the optical fiber by measuring the high quality edge of the downhole target, but the MOT instrument measurement is single-point discontinuous, and once the MOT instrument deflects in the well, the downhole casing cannot rotate, resulting in the inability to accurately identify the position of the optical fiber. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that the MOT instrument measurement in the prior art is single-point discontinuous and once the MOT instrument is deflected underground, the optical fiber position cannot be accurately identified, and to provide a gravity high-side and mass high-side measurement device and method based on transient electromagnetic method.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A device for measuring gravity high side and mass high side based on transient electromagnetic method, comprising: an optical cable, a casing, a measuring instrument and an accelerometer;

[0006] The optical fiber is evenly wound on the outside of the casing; the measuring instrument includes a ring array probe, a transmitting probe, a transmitting circuit and a main control circuit; the ring array probe is arranged on the surface of the transmitting probe; the transmitting probe is connected to the transmitting circuit, the transmitting circuit supplies the transmitting probe with a square wave excitation signal, the ring receiving probe receives the direct electromagnetic signal and eddy current signal around the optical fiber, and after amplifying, sends the amplified signal to the main control circuit for collection and processing; after the ring array probe, the transmitting probe, the transmitting circuit and the main control circuit are connected, they move inside the casing; the accelerometer is arranged on the outside of the transmitting probe.

[0007] A further improvement of the present invention is:

[0008] Furthermore, the annular array probe includes a plurality of probe groups; each probe group includes a plurality of sensors, and adjacent sensors in the same probe group have a fixed angle difference; the sensors with the same number in a probe group and the previous probe group have a fixed angle difference.

[0009] Furthermore, there are several groups of accelerometers, with two in each group; the accelerometers in each group are installed step by step on both sides of the transmitting probe.

[0010] Furthermore, the model of the accelerometer is ADXL354 accelerometer; the accelerometer is used to calibrate the error caused by the deflection of the measuring instrument due to external forces in a vertical well.

[0011] A method for determining the gravity high side and mass high side based on the transient electromagnetic method includes:

[0012] Place the annular array probe outside the transmitting probe, connect the transmitting probe and the transmitting circuit, connect the control pin of the transmitting circuit and the control pin of the main control board. After completing the electrical connection, debug the excitation signal of the transmitting probe. The transmitting circuit supplies a square wave excitation signal to the transmitting probe. The annular receiving probe receives the direct electromagnetic signal and eddy current signal around the optical fiber, and after amplification, gives them to the main control circuit for acquisition and processing; after the annular array probe, the transmitting probe, the transmitting circuit and the main control circuit are connected, move inside the casing; attach the optical fiber to the casing shell, rotate the optical fiber, and observe the signal of the receiving array element; decompose the signals of each group of receiving arrays, and use the accelerometer to correct the angle error of the instrument. After completing the correction, conduct multiple groups of experiments to verify the measurement performance of the instrument for the optical fiber; complete the overall joint debugging of the instrument on the ground.

[0013] Furthermore, the square wave excitation signal is 5V.

[0014] Furthermore, the transmitting circuit supplies a square wave excitation signal to the transmitting probe. The annular receiving probe receives the direct electromagnetic signal and eddy current signal around the optical fiber, and after amplification, gives them to the main control circuit for acquisition and processing. Specifically: the transmitting probe generates a primary magnetic field in space. When the positive pulse is turned off, a circular induced current will be generated around the optical fiber outside the casing and a secondary magnetic field will be generated; an induced electromotive force will be generated on the annular receiving probe, and the relative distance information and azimuth of the optical cable outside the pipe will be obtained by using the induced electromotive force.

[0015] Furthermore, using the induced electromotive force to obtain the relative distance information and azimuth of the optical cable outside the pipe, specifically: establish a transient electromagnetic multi-well exploration model, introduce the magnetic vector potential A, and solve the magnetic scalar potential V by the finite element method or the boundary element method m , as shown in formula (1):

[0016]

[0017] Among them, the solution formula for the magnetic vector potential A is: If there is a steady-state current in the model, the magnetic vector potential A must be solved, as shown in formula (2);

[0018]

[0019] Through the magnetic vector potential A, calculate And the current J is calculated simultaneously by applying or by augmenting the previous electric scalar potential and current equations; when moving to the time domain, solve formula (3):

[0020]

[0021] Apply a positive pulse excitation of a bipolar transient pulse signal on the transmitting probe. The transmitting probe generates a primary magnetic field in space. When this positive pulse is turned off, a circular induced current will be generated around the downhole casing and a secondary magnetic field will be generated. An induced electromotive force will be generated on the receiving probe and is calculated through formula (4):

[0022]

[0023] Furthermore, an angle error correction is carried out on the instrument with the help of an accelerometer. Specifically: The signal measured by the sensor at the high side of the mass is the magnetic signal generated by the target itself, denoted as sensor No. 0. It is stipulated that the sensor located at the high side of gravity is the position of the initial sensor. Based on the accelerometer, the offset angle of the initial sensor position is calculated. Combining the angular difference between the initial sensor and sensor No. 0 at this time, the azimuth of the target at the high side of the mass can be obtained. The specific calculation formula is:

[0024] The absolute azimuth of the optical fiber = the relative azimuth measured by sensor No. 0 and the initial sensor + the azimuth of the accelerometer.

[0025] Furthermore, the accuracy of the GMR sensors in the circular array is:

[0026]

[0027] Among them, represents its detection accuracy, and n represents the number of sensors in the circular array probe.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention receives the direct electromagnetic signal and eddy current signal around the optical fiber through a circular array probe composed of sensors, amplifies them, and then collects and processes them by the main control circuit; this probe array improves the accuracy of detecting the high side of the mass, and the approximate azimuth of the target on the outer wall of the casing can be obtained by measuring the high side of the mass.

[0030] Furthermore, the present invention can effectively reduce the missed detection of damaged casings. By adding an identification algorithm for the high side of gravity, the downhole target identification algorithm process can be more accurately improved. The transient electromagnetic detection method adopted by the present invention effectively utilizes a bipolar periodic signal to generate a primary field signal source. At the same time, when the adjacent positive and negative pulse signals receive DC stable interference, the elimination of DC bias can be achieved overall.

[0031] The present invention can complete the identification of the high side of gravity and the high side of mass only through the annular array probe composed of an accelerometer and a sensor. There are not too many complex electromagnetic compatibility problems in the hardware, which provides convenience for instrument maintenance. It has the characteristics of "high performance and easy maintenance" and is relatively practical in the field of oil exploration and can efficiently perform detection tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a schematic diagram of the position distribution of the downhole optical cable;

[0034] Figure 2 It is a schematic diagram of the primary field of the instrument transmitting probe;

[0035] Figure 3 It is a schematic diagram of the distribution of accelerometers on the instrument transmitting probe;

[0036] Figure 4 It is a schematic diagram of the detection data conversion format process. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0039] It should be noted that like reference numerals and letters denote like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

[0040] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship in which the product of the invention is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0041] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0042] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they 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 or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0043] The present invention will be further described in detail below with reference to the figures:

[0044] See Figure 1 、 Figure 2 and Figure 3 , the present invention discloses a device for measuring gravity high side and mass high side based on transient electromagnetic method, including: optical cable, casing, measuring instrument and accelerometer;

[0045] The optical fiber is evenly wound outside the casing; the measuring instrument includes a ring array probe, a transmitting probe, a transmitting circuit and a main control circuit; the ring array probe is arranged on the surface of the transmitting probe; the transmitting probe is connected to the transmitting circuit, and the transmitting circuit supplies a square wave excitation signal to the transmitting probe. The ring receiving probe receives the direct electromagnetic signal and eddy current signal around the optical fiber, amplifies them and then gives them to the main control circuit for acquisition and processing; after the ring array probe, the transmitting probe, the transmitting circuit and the main control circuit are connected, they move inside the casing; the accelerometer is arranged outside the transmitting probe.

[0046] The annular array probe includes a plurality of probe groups; each probe group includes a plurality of sensors, and adjacent sensors in the same probe group have a fixed angle difference; the probe group has a fixed angle difference from the sensors with the same number in the previous probe group.

[0047] There are several groups of accelerometers, with two in each group; the accelerometers in each group are installed stepwise on both sides of the transmitting probe.

[0048] The model of the accelerometer is ADXL354 accelerometer; the accelerometer is used to calibrate the error caused by the deflection of the measuring instrument due to external forces in the vertical well. The sensor is a GMR sensor.

[0049] A method for determining the gravity high side and mass high side based on the transient electromagnetic method includes: placing the annular array probe outside the transmitting probe, connecting the transmitting probe and the transmitting circuit, connecting the control pin of the transmitting circuit and the control pin of the main control board, debugging the excitation signal of the transmitting probe after completing the electrical connection, the transmitting circuit supplying a square wave excitation signal to the transmitting probe, the annular receiving probe receiving the direct electromagnetic signal and the eddy current signal around the optical fiber, and amplifying them and then collecting and processing them by the main control circuit; after the annular array probe, the transmitting probe, the transmitting circuit and the main control circuit are connected, they move inside the casing; attaching the optical fiber to the casing shell, rotating the optical fiber, and observing the signal of the receiving array element; decomposing the signals of each group of receiving arrays, and correcting the angle error of the instrument with the help of the accelerometer, and after completing the correction, conducting multiple groups of experiments to verify the measurement performance of the instrument for the optical fiber; completing the overall joint debugging of the instrument on the ground. The square wave excitation signal is 5V.

[0050] The transmitting circuit supplies a square wave excitation signal to the transmitting probe, the annular receiving probe receives the direct electromagnetic signal and the eddy current signal around the optical fiber, and amplifies them and then collects and processes them by the main control circuit. Specifically: the transmitting probe generates a primary magnetic field in space. When the positive pulse is turned off, a circular induced current will be generated around the optical fiber outside the casing and a secondary magnetic field will be generated; an induced electromotive force will be generated on the annular receiving probe, and the relative distance information and azimuth of the optical cable outside the pipe will be obtained by using the induced electromotive force.

[0051] Using the induced electromotive force to obtain the relative distance information and azimuth of the optical cable outside the pipe, specifically: establishing a transient electromagnetic multi-well exploration model, introducing the magnetic vector potential A, and solving the magnetic scalar potential V by the finite element method or the boundary element method m , as shown in formula (1):

[0052]

[0053] Among them, the solution formula of the magnetic vector potential A is: if there is a steady current in the model, the magnetic vector potential A must be solved, as shown in formula (2);

[0054]

[0055] Calculate through the magnetic vector potential A And the current J is calculated simultaneously by applying or by augmenting the previous electric scalar potential and current equations; when moving to the time domain, solve formula (3):

[0056]

[0057] Apply a positive pulse excitation of a bipolar transient pulse signal on the transmitting probe. The transmitting probe generates a primary magnetic field in space. When this positive pulse is turned off, a circular induced current will be generated around the downhole casing and a secondary magnetic field will be generated. An induced electromotive force will be generated on the receiving probe and is calculated through formula (4):

[0058]

[0059] Carry out angle error correction on the instrument with the help of an accelerometer. Specifically: the signal measured by the sensor at the high side of the mass is the magnetic signal generated by the target itself, denoted as the No. 0 sensor. It is stipulated that the sensor located at the high side of gravity is the position of the initial sensor. Based on the accelerometer, calculate the offset angle of the initial sensor position. Combining the angular difference between the initial sensor and the No. 0 sensor at this time, the azimuth of the target at the high side of the mass can be obtained. The specific calculation formula is:

[0060] The absolute azimuth of the optical fiber = the relative azimuth measured by the No. 0 sensor and the initial sensor + the azimuth of the accelerometer.

[0061] The accuracy of the GMR sensors in the circular array is:

[0062]

[0063] Among them, represents its detection accuracy, and n represents the number of sensors in the table.

[0064] Example:

[0065] The mass distribution of the casing is usually uniform. Based on the target, the mass distribution at a certain point will increase. Therefore, the location where the mass distribution changes is defined as the high-mass side. By measuring the high-mass side, the target can be detected. Combining with the gravity high side of the instrument, the position of the sensor at the gravity high side can be obtained. From this sensor, the position of the sensor at the high-mass side, that is, the azimuth of the target, can be deduced. In order to improve the detection accuracy of the instrument, the present invention proposes a receiving probe distribution structure of a circular array probe. The circular array probe is composed of 32 GMR sensors, and the sensors directly measure the high-mass side. The process of deducing the high-mass side sensor from the gravity high side requires the assistance of an ADXL354 accelerometer. At the position of the gravity high side, the output of the accelerometer is 0 degrees. The offset angle between the high-mass side and the gravity high side can be obtained through the offset angle output by the accelerometer.

[0066] The working principle of a method for determining the gravity high side and the high-mass side based on the transient electromagnetic method is as Figure 1 and as Figure 2 shown, including a primary emission field, a secondary eddy current field, a casing with a uniform mass distribution, and an optical fiber attached to the surface. The measuring instrument includes a transmitting probe, a circular array receiving probe, a transmitting circuit, and a main control circuit. When the measuring instrument is working normally, the transmitting probe is connected to the transmitting circuit. The transmitting circuit supplies a square wave excitation signal with a magnitude of 5V to the transmitting probe. The circular receiving probe receives the direct electromagnetic signal and the eddy current signal around the optical fiber, amplifies them, and then gives them to the main control circuit for acquisition and processing. The distribution of the targets on the outer wall of the casing is drawn through three-dimensional imaging software, and the position of the target is at the high-mass side.

[0067] In Figure 1 , the optical cable is generally attached to the outer wall of the downhole casing, and the circular array probe is attached to the outside of the transmitting probe. The secondary field generated around the downhole optical fiber is fed back to the surface of the sensor, thereby generating an induced electromotive force, which contains information about the downhole optical fiber.

[0068] In Figure 2 , the number of turns of the coil and the winding method of each group of transmitting probes are determined through simulation and experiment.

[0069] Since the measuring instrument will tilt in the horizontal wellbore and it is difficult to maintain a relatively horizontal attitude with the wellbore wall, during the downhole measurement process, the measuring instrument will cause the sensor to be unable to accurately obtain the relative method of the downhole optical fiber due to the inclination angle generated with the wellbore wall. Therefore, an ADXL354 accelerometer needs to be installed on the measuring instrument to assist the GMR sensor for positioning. The installation position is as Figure 3The accelerometer uses the built-in suspended ball to generate a reaction force on the inclined surface, thereby obtaining the voltage value on a certain component. The sensor has six reference axes, namely ±x, ±y, and ±z; the inclined tool surface angle is obtained by calibrating the output of the three axes. In terms of installation position, the accelerometers are divided into 4 groups, with 2 accelerometers in each group. The installation position of every 2 accelerometers is installed in a stepped manner. The specific installation positions are as follows: Figure 3 .

[0070] Figure 3 It is the distribution of accelerometers on the instrument transmitting probe. Since the instrument will deviate in the horizontal wellbore, in order to obtain the offset downhole, the relative orientation measured by the GMR array probe is used to obtain the absolute orientation of the optical cable.

[0071] In the vertical well, a ring array composed of GMR sensors replaces the single receiving probe to complete the measurement of the high side of the casing quality outside the vertical well tubing without deflecting the instrument as much as possible. Since the instrument will deflect due to external forces in the vertical well, in order to calibrate the error caused by the deflection, it is necessary to measure the deflection angle through an accelerometer and calculate the absolute orientation of the optical fiber through formula (5).

[0072] The basis of this method is the transient electromagnetic method. A bipolar excitation signal needs to be applied externally. By receiving the signal of the secondary eddy current field of the target at the high-quality side, an induced electromotive force is generated, and the target information is obtained through the induced electromotive force. The specific steps are as follows:

[0073] (1) When the positive pulse excitation of the bipolar transient pulse signal is applied to the transmitting probe, the transmitting probe generates a primary magnetic field in space. When the positive pulse is turned off, a circular induced current and a secondary magnetic field are generated around the optical fiber outside the casing. An induced electromotive force is generated on the receiving coil, which is calculated by formula (1). The induced electromotive force is used to obtain the relative distance information and orientation of the optical cable outside the casing. The specific implementation method includes:

[0074] A transient electromagnetic cluster well detection model is established, and the magnetic vector potential A is introduced. The finite element method or boundary element method can be used to solve the magnetic scalar potential V m , as shown in formula (1):

[0075]

[0076] Once there is a steady-state current in the model, the magnetic vector potential A must be solved, as shown in equation (2).

[0077]

[0078] The magnetic vector potential is used to calculate And the current J can be calculated simultaneously by applying or by augmenting the previous electric scalar potential and current equations. When moving to the time domain, the following equations are solved:

[0079]

[0080] A forward pulse excitation of a bipolar transient pulse signal is applied to the transmitting probe. The transmitting probe generates a primary magnetic field in space. When the forward pulse is turned off, a circular induced current is generated around the downhole casing and a secondary magnetic field is generated. An induced electromotive force will be generated on the receiving probe and can be calculated through formula (4):

[0081]

[0082] The GMR sensor directly measures the secondary eddy current field generated at the high side of the mass. The signals detected by the sensors located at different positions in the circular array are inconsistent. In the area at and near the high side of the mass, it can be seen that the curve drawn by the electromagnetic signal will have an obvious offset. Since the directly measured magnetic signal and eddy current signal exist simultaneously, the signal measured by the sensor at the high side of the mass is the magnetic signal generated by the target itself, denoted as the No. 0 sensor. The signals measured near the high side of the mass are the eddy current signals generated around the target. Since the intensity of the eddy current signal is greater than the intensity of the magnetic signal at these points, the sensor directly collects the eddy current signal. These sensors are sequentially denoted as the No. 1 sensor and the No. 2 sensor.

[0083] It is usually stipulated that the position of the sensor located at the high side of gravity is the position of the initial sensor. However, due to the inclination and other situations when the instrument goes down the well, the position of the initial sensor will shift. Then, there will be an error in using the angular difference between the initial sensor and the No. 0 sensor to locate the position of the high side of the mass. At this time, it is necessary to use the ADXL354 accelerometer to calculate the offset angle of the position of the initial sensor, and combine the angular difference between the initial sensor and the No. 0 sensor at this time to obtain the azimuth of the high side of the mass target. The specific calculation formula is:

[0084] The absolute azimuth of the optical fiber = the relative azimuth measured by the No. 0 sensor and the initial sensor + the azimuth of the accelerometer.

[0085] See Figure 4 , the circular array designed by this method is distributed on the surface of the transmitting probe where it is located and is divided into 4 probe groups in total. The 32 GMR sensors of the probe in probe group A have a difference of 11.25 degrees between adjacent sensors. The sensors with the same number on probe group A and probe group B have a difference of 11.25 degrees, and so on. Probe group B and probe group C each have a difference of 11.25 degrees on this basis. A complete high side of the mass detection system can be formed by the four groups of probes A, B, C, and D. This design can not only enable each group of probes to work independently, but also has relatively uniform detection probes for all directions on 360 degrees.

[0086] The specific steps are as follows:

[0087] Arrange the annular array receiving probes on the probe of the instrument according to the preset spatial positions. First, place the sensor in the corresponding groove of the skeleton, and then press the sensor tightly so that the sensor base is closely attached to the surface of the groove. Use fusible glue to seal the four sides of the sensor base for fixation, and complete the sensor loading of the four groups of probes in a similar way.

[0088] Connect the transmitting probe and the transmitting circuit. Connect the control pin of the transmitting circuit and the control pin of the main control board. After completing the electrical connection, debug the excitation signal of the transmitting probe, attach the optical fiber to the instrument shell, and rotate the optical fiber to observe the signals of the receiving array elements.

[0089] After completing the above debugging, decompose the signals of each group of receiving arrays, and use the inclinometer platform to correct the angle error of the instrument. After completing the correction, conduct multiple groups of experiments to verify the measurement performance of the instrument for the optical fiber.

[0090] After completing the debugging of the above sub-modules, complete the overall joint debugging of the instrument on the ground.

[0091] This method uses a magnetic core winding as the transmitting probe that can emit a primary magnetic field, and uses an annular array receiving probe as the probe for receiving signals. The radial detection range is controlled by changing the size and material parameters of the probe. The receiving sensor needs to be closely attached to the inner wall of the casing, and the purpose of this is to more accurately identify small damage differences.

[0092] According to the basic detection principle of the transient electromagnetic method, the outer-casing optical cable detection system based on GMR sensors needs to first emit an electromagnetic pulse, that is, a primary field signal. When the secondary field signals containing the optical cable, collar, casing, etc. are reflected back into the instrument, the instrument needs to be able to receive and process this electromagnetic signal and upload it to the ground chassis for data display.

[0093] In the signal receiving and processing part, since the response voltage amplitude of the GMR sensor varies from 0V to 0.3V under the excitation of the magnetic field, and the output form is differential output at both ends, the analog signal output by the GMR is amplified differentially by an instrument.

[0094] The accelerometer can measure the acceleration of an object in three directions, providing information on three different components in the X, Y, and Z directions. The system attitude acquisition circuit then uses this information to calculate the deflection angles of the instrument in three directions inside the pipe, so as to obtain the angular offset of the initial sensor inside the instrument.

[0095] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A device for measuring the gravity high side and mass high side based on the transient electromagnetic method, characterized in that, Including: Optical cable, sleeve, measuring instrument and accelerometer; The optical fiber is evenly wound around the outside of the sleeve; the measuring instrument includes an annular array probe, a transmitting probe, a transmitting circuit and a main control circuit; the annular array probe is arranged on the surface of the transmitting probe; the transmitting probe is connected to the transmitting circuit, and the transmitting circuit supplies a square wave excitation signal to the transmitting probe. The annular receiving probe receives the direct electromagnetic signal and eddy current signal around the optical fiber, and after amplification, gives them to the main control circuit for acquisition and processing; after the annular array probe, the transmitting probe, the transmitting circuit and the main control circuit are connected, they move inside the sleeve; the accelerometer is arranged outside the transmitting probe.

2. The gravity high side and mass high side measuring device based on the transient electromagnetic method according to claim 1, wherein The annular array probe includes a plurality of probe groups; each probe group includes a plurality of sensors, and adjacent sensors in the same probe group have a fixed angle difference; the probe group has a fixed angle difference from the sensors with the same number in the previous probe group.

3. The gravity high side and mass high side measuring device based on the transient electromagnetic method according to claim 2, characterized in that, The accelerometers are in several groups, with two in each group; the accelerometers in each group are installed stepwise on both sides of the transmitting probe.

4. The gravity high side and mass high side measuring device based on the transient electromagnetic method according to claim 3, characterized in that, The model number of the accelerometer is ADXL354 accelerometer; the accelerometer is used to calibrate the error caused by the deflection of the measuring instrument due to external forces in the vertical well.

5. A method for measuring the gravity high side and mass high side based on the transient electromagnetic method, characterized in that, Including: Place the annular array probe outside the transmitting probe, connect the transmitting probe and the transmitting circuit, connect the control pin of the transmitting circuit and the control pin of the main control board. After completing the electrical connection, debug the excitation signal of the transmitting probe. The transmitting circuit supplies a square wave excitation signal to the transmitting probe. The annular receiving probe receives the direct electromagnetic signal and eddy current signal around the optical fiber, and after amplification, gives them to the main control circuit for acquisition and processing; after the annular array probe, the transmitting probe, the transmitting circuit and the main control circuit are connected, they move inside the sleeve; attach the optical fiber to the outer shell of the sleeve, rotate the optical fiber, and observe the signals of the receiving array elements; decompose the signals of each receiving array, and use the accelerometer to correct the angular error of the instrument. After completing the correction, conduct multiple groups of experiments to verify the measurement performance of the instrument for the optical fiber; complete the overall joint debugging of the instrument on the ground.

6. The method for determining the gravity high side and mass high side based on the transient electromagnetic method according to claim 5, characterized in that The square wave excitation signal is 5V.

7. The method for determining the gravity high side and mass high side based on the transient electromagnetic method according to claim 5, wherein The transmitting circuit supplies a square wave excitation signal to the transmitting probe. The annular receiving probe receives the direct electromagnetic signal and eddy current signal around the optical fiber, and after amplification, gives them to the main control circuit for acquisition and processing. Specifically: the transmitting probe generates a primary magnetic field in space. When the positive pulse is turned off, a circular induced current will be generated around the optical fiber outside the sleeve and a secondary magnetic field will be generated; an induced electromotive force will be generated on the annular receiving probe, and the relative distance information and azimuth of the optical cable outside the pipe will be obtained by using the induced electromotive force.

8. The method for determining the gravity high side and mass high side based on the transient electromagnetic method according to claim 7, wherein, The relative distance information and azimuth of the optical cable outside the pipe are obtained by using the induced electromotive force, specifically: a transient electromagnetic multi-well detection model is established, the magnetic vector potential A is introduced, and the magnetic scalar potential V is solved by the finite element method or the boundary element method m , as shown in formula (1): Among them, the solution formula for the magnetic vector potential A is: when there is a steady-state current in the model, the magnetic vector potential A must be solved, as shown in formula (2); Calculate through the magnetic vector potential A And the current J is calculated simultaneously by applying or by augmenting the previous electric scalar potential and current equations; when moving to the time domain, solve formula (3): Apply a positive pulse excitation of a bipolar transient pulse signal to the transmitting probe. The transmitting probe generates a primary magnetic field in space. When the positive pulse is turned off, a circular induced current will be generated around the downhole casing and a secondary magnetic field will be generated. An induced electromotive force will be generated on the receiving probe and is calculated by formula (4):

9. The method for determining the gravity high side and mass high side based on the transient electromagnetic method according to claim 8, characterized in that, The angle error correction of the instrument by means of an accelerometer is specifically as follows: the signal measured by the sensor at the high side of the mass is the magnetic signal generated by the target itself, denoted as the No. 0 sensor. It is stipulated that the sensor located at the high side of gravity is the position of the initial sensor. Based on the accelerometer, the offset angle of the initial sensor position is calculated, and the azimuth of the target at the high side of the mass can be obtained by combining the angular difference between the initial sensor and the No. 0 sensor at this time. The specific calculation formula is as follows: The absolute azimuth of the optical fiber = the relative azimuth measured by the No. 0 sensor and the initial sensor + the accelerometer azimuth.

10. The method for determining the gravity high side and mass high side based on the transient electromagnetic method according to claim 9, characterized in that, The accuracy of the GMR sensors in the ring array is: Among them, represents its detection accuracy, and n represents the number of sensors in the annular array probe.

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