A downhole tubing positioning and centralizing device and method

Abstract

The present application relates to the technical field of downhole tubing positioning and centralizing, and particularly relates to a downhole tubing positioning and centralizing device and method. The present application first acquires a first magnetic signal of a cable connected to a centralizer when the cable passes through a first magnetic reader during lowering, and a second magnetic signal when the cable passes through a second magnetic reader; then acquires the cable lowering speed at each moment, further combines the total number of the second magnetic signals to acquire the lowering depth of the centralizer at each moment, and further adjusts the cable lowering speed in real time until the centralizer is lowered to a preset target depth and stops and centralizes. The present application continuously marks the magnetic marker points in the cable lowering process based on the magnetic marker measurement method to calculate the lowering depth, and evaluates the cable lowering speed by means of the misalignment magnetic reading time length between different magnetic readers to supplement the calculation of the cable lowering depth which has been lowered but the magnetic marker cannot accurately measure, to accurately position the centralizer, thereby improving the positioning and centralizing accuracy of the downhole tubing.

Description

Technical Field

[0001] This invention relates to the field of downhole tubing positioning and straightening technology, specifically to a downhole tubing positioning and straightening device and method. Background Technology

[0002] In the development of low-permeability tight oil reservoirs, in order to ensure the accurate placement of fracturing tools during segmented fracturing of tubing, it is usually necessary to connect a centralizer to the front end of the tool to assist in positioning and centralization. The traditional method usually involves monitoring the descent length of the centralizer connecting cable for positioning. Accurate positioning of the centralizer is an important link to ensure the success of segmented fracturing operations and improve the efficiency of oilfield development.

[0003] Currently, the Martin-Dick magnetic marker method is generally used to measure the length of the centralizer connecting cable in the well to determine the descent depth of the centralizer. However, in the actual measurement process, not only is it necessary to properly calibrate the cable in advance, but the complex downhole environment may also cause the magnetic signal to be lost or distorted, making it impossible for the Martin-Dick magnetic marker to effectively transmit data, which in turn leads to errors in the measurement data and makes it impossible to accurately and in real time locate and centralize the downhole tubing. Summary of the Invention

[0004] To address the technical problem of poor positioning and straightening accuracy of downhole tubing, the present invention aims to provide a positioning and straightening device and method for downhole tubing, the specific technical solution of which is as follows: A method for positioning and straightening downhole tubing, the method comprising: The system acquires the first magnetic signal when the cable connected to the stabilizer passes the first magnetic reader during the lowering process, and the second magnetic signal when it passes the second magnetic reader; wherein the second magnetic reader is located after the first magnetic reader, and the two magnetic readers read magnetic signals synchronously. At each moment during the cable lowering process, based on the misalignment characteristics between the first magnetic signal and the second magnetic signal, the reading misalignment time of the second magnetic reader relative to the first magnetic reader is obtained, and combined with the positional distance between the first magnetic reader and the second magnetic reader, the cable lowering speed is obtained; During the cable lowering process, the lowering depth of the stabilizer at each moment is obtained based on the time interval between each moment and the moment corresponding to the nearest previous second magnetic signal, as well as the cable lowering speed and the total number of second magnetic signals. The cable lowering speed is adjusted in real time according to the lowering depth until the stabilizer is lowered to the preset target depth and then stopped and positioned for stabilization.

[0005] Furthermore, a first demagnetizer for demagnetizing the cable and a first magnetizer for magnetizing the cable are installed before the first magnetizer; the first demagnetizer is located before the first magnetizer; a second demagnetizer for demagnetizing the cable and a second magnetizer for magnetizing the cable are installed below the second magnetizer; the second demagnetizer is located before the second magnetizer; starting from the second magnetizer, whenever a preset number of second magnetic signals are read, the second magnetizer magnetizes the cable once.

[0006] Furthermore, the method for obtaining the magnetic misalignment duration includes: At each moment during the cable lowering process, the time sequences of the first magnetic signal and the second magnetic signal are fitted respectively; a first subsequence of a preset length is obtained from the starting point of the first magnetic signal time sequence along the time sequence direction, and a second subsequence of a preset length is obtained from the ending point of the second magnetic signal time sequence along the reverse time sequence direction, with the first subsequence and the second subsequence having the same sequence direction; Based on the distribution characteristics of the first magnetic signal in the first sub-sequence, an anti-interference weight is obtained; based on the difference between the first sub-sequence and the second sub-sequence, a sequence synchronization coefficient is obtained; the sequence synchronization coefficient is weighted using the anti-interference weight to obtain the misalignment synchronization coefficient between the first sub-sequence and the second sub-sequence. Change the preset length to obtain the misalignment synchronization coefficient under each preset length; obtain the magnetic reading misalignment duration according to the preset length corresponding to the maximum misalignment synchronization coefficient.

[0007] Further, the magnetic misalignment duration is obtained based on the preset length corresponding to the maximum misalignment synchronization coefficient, including: The preset length corresponding to the maximum misalignment synchronization coefficient is taken as the synchronous magnetic reading length; the sequence length of the first magnetic signal timing sequence is subtracted from the synchronous magnetic reading length, and then divided by the magnetic reading frequency of the first magnetic reader to obtain the magnetic reading misalignment duration.

[0008] Furthermore, the method for obtaining the cable lowering speed includes: The positional distance between the first and second magnetic reading devices is taken as the magnetic reading misalignment distance; at each moment during the cable lowering process, the magnetic reading misalignment distance is divided by the magnetic reading misalignment duration to obtain the instantaneous speed of the cable; Based on the magnetic misalignment duration at each moment and the magnetic misalignment duration at the previous adjacent moment, the trend weight of the cable descent speed is obtained; the instantaneous speed of the cable is weighted using the trend weight to obtain the cable lowering speed.

[0009] Furthermore, the method for obtaining the trend weight includes: The ratio of the magnetic misalignment duration at the previous adjacent time point to the magnetic misalignment duration at each time point is used as the trend weight, where the magnetic misalignment duration at the previous adjacent time point is the numerator.

[0010] Furthermore, the method for obtaining the depth of descent includes: At each moment during the cable lowering process, a first lowering depth is obtained based on the positional distance between the first magnetizer and the second magnetizer, and the total number of magnetizers applied by the second magnetizer; a second lowering depth is obtained based on the positional distance between the first magnetizer and the second magnetizer, and the remainder after dividing the total number of second magnetic signals by a preset number; a third lowering depth is obtained based on the time interval between each moment and the moment corresponding to the most recent second magnetic signal, and the cable lowering speed. The sum of the first, second, and third lowering depths is taken as the lowering depth of the stabilizer.

[0011] Furthermore, the method for obtaining the third depth includes: Between each time point and the time point corresponding to the most recent second magnetic signal, the integral of the cable lowering speed at all times is taken as the third lowering depth.

[0012] Furthermore, the method for adjusting the cable lowering speed includes: When the lowering depth of the stabilizer is less than the preset deceleration depth, it does not interfere with the cable lowering speed; when the lowering depth of the stabilizer is greater than or equal to the preset deceleration depth, the cable lowering speed is reduced to the preset speed; wherein, the preset deceleration depth is less than the preset target depth.

[0013] A positioning and straightening device for downhole tubing includes a straightening body and a positioning and straightening system; the positioning and straightening system is used to perform the steps in the positioning and straightening method for downhole tubing.

[0014] The present invention has the following beneficial effects: This invention first acquires the first magnetic signal of the cable connected to the stabilizer when it passes the first magnetic sensor and the second magnetic signal when it passes the second magnetic sensor during the cable lowering process, providing a data foundation for subsequent analysis. Then, at each moment during the cable lowering process, based on the misalignment characteristics between the first and second magnetic signals, the misalignment time of the second magnetic sensor relative to the first magnetic sensor is acquired. This, combined with the positional distance between the first and second magnetic sensors, allows for the acquisition of the cable lowering speed, preparing for subsequent supplementary calculations of the cable descent depth, which has already descended but cannot be accurately measured by the magnetic markers. During the cable lowering process, based on... Based on the time interval between each moment and its nearest corresponding moment of the second magnetic signal, and the cable lowering speed and the total number of second magnetic signals (where the total number of second magnetic signals can be considered as the total number of magnetic marker points), the descent depth is calculated using the magnetic marking method. This is then combined with the descent depth assessed based on the cable lowering speed to comprehensively obtain the centralizer's descent depth at each moment. The cable lowering speed is then adjusted in real-time according to the descent depth to accurately position the centralizer, avoiding repeated adjustments that could affect positioning efficiency. The centralizer is lowered to a preset target depth, at which point positioning and centralization are achieved. This invention uses a magnetic marking measurement method to continuously mark magnetic marker points during cable descent for descent depth calculation. It also uses the staggered reading time between different magnetic readers to assess the cable descent speed, supplementing the calculation of cable descent depths that have already been lowered but cannot be accurately measured by magnetic markers. This accurately positions the centralizer, thereby improving the accuracy of positioning and centralizing downhole tubing. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a structural diagram of a centralizer provided in one embodiment of the present invention; Figure 2 A flowchart illustrating a method for positioning and straightening a downhole tubing according to an embodiment of the present invention; Figure 3 This is a schematic diagram showing the composition and distribution of magnetic components in a magnetic marker measurement system provided in one embodiment of the present invention.

[0017] The following are the labels in the diagram: 1. Upper connector; 2. Central tube; 3. Moving piston; 4. Connecting sleeve; 5. Fixed piston; 6. Locking ring; 7. Cone; 8. Outer sleeve; 9. Straightening body; 10. Guide head. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a downhole tubing positioning and straightening device and method proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] The following description, in conjunction with the accompanying drawings, details the specific scheme of the positioning and straightening device and method for downhole tubing provided by the present invention.

[0021] The implementation scenario targeted by this invention is as follows: the cable is lowered by a ground winch or other device, thereby driving the centralizer and fracturing tools connected to the end of the cable to descend inside the oil pipe. The lowering depth of the cable or centralizer is measured in real time during the lowering process until it is accurately lowered to the preset target position and then stopped and positioned for centralization.

[0022] Please see Figure 1 The diagram shows a structural diagram of a centralizer provided in one embodiment of the present invention.

[0023] The centralizer mainly consists of an upper connector 1, a central tube 2, a moving piston 3, a connecting sleeve 4, a fixed piston 5, a locking ring 6, a cone 7, an outer sleeve 8, a centralizer 9, and a guide head 10. The connection relationships of each component are as follows: the upper connector 1 is fixed to the upper end of the central tube 2 by a threaded connection; the upper end of the moving piston 3 is placed outside the upper connector 1; the lower end of the moving piston 3 is fixed to the upper end of the connecting sleeve 4 by a threaded connection; the lower end of the connecting sleeve 4 is fixed to the cone 7 by a threaded connection; the fixed piston 5 is fixed to the middle of the central tube 2 by a threaded connection and is placed inside the connecting sleeve 4; the cone 7 and the locking ring 6 are threaded to the outer wall of the central tube 2; the lower end of the outer sleeve 8 is fixed to the upper end of the centralizer 9 by a threaded connection; the lower end of the centralizer 9 is fixed to the outer wall of the guide head 10 by a connection; and the inner side of the guide head 10 is fixed to the lower end of the central tube 2 by a threaded connection.

[0024] The upper end of the central tube 2 is connected to the upper connector 1, and the lower end is connected to the guide head 10. A sand discharge mechanism is provided at the lower part of the central tube 2. The upper outer wall of the central tube 2 is connected to the fixed piston 5 by a thread. The upper end of the moving piston 3 is placed outside the upper connector 1. The lower end of the moving piston 3 is connected to the upper end of the connecting sleeve 4 by a thread. The connecting sleeve 4 is placed outside the fixed piston. The fixed piston 5, the moving piston 3, the inner side of the outer sleeve 8, and the upper outer side of the central tube 2 form an air cavity under the action of the sealing mechanism, which can realize the fixed-point start-up, positioning and straightening function. The lower end of the connecting sleeve 4 is connected to the cone 7 by a thread. The cone 7 is equipped with a locking mechanism inside, which can realize the locking function after the cone moves down. The lower end of the cone 7 is equipped with a conical surface structure, and a protective mechanism with a certain angle is designed at the end. During the downward movement of the cone 7, the conical surface plays a guiding role, and the protective mechanism plays a limiting role. The centralizing body 9 is connected to the outside of the guide head 10 by a thread. The upper end of the centralizing body 9 is connected to the lower end of the outer sleeve 4 by a thread. The outer sleeve 8 has a four-lobed structure and is separate from the cone, which facilitates well entry. The middle part of the outer casing 8 is designed with a positioning and straightening mechanism. After the tool is inserted into the well to a certain depth, due to the presence of the air cavity, the cone moves downward under the action of pressure difference. The protection mechanism contacts the upper end of the outer casing 8, and the positioning and straightening function of the positioning and straightening mechanism is activated.

[0025] Please see Figure 2 The diagram illustrates a flowchart of a downhole tubing positioning and straightening method according to an embodiment of the present invention, specifically including: Step S1: Obtain the first magnetic signal when the cable connected to the stabilizer passes the first magnetic reader during the lowering process, and the second magnetic signal when it passes the second magnetic reader; wherein the second magnetic reader is located after the first magnetic reader, and the two magnetic readers read magnetic signals synchronously.

[0026] In one embodiment of the present invention, a magnetic marker measurement system is first installed between the ground winch and the wellhead. The magnetic marker measurement system includes at least a first magnetic reader and a second magnetic reader, with the second magnetic reader located after the first magnetic reader. The cable is lowered by the ground winch.

[0027] Considering that the cable lowered by the ground winch may have residual magnetic signals, in order to eliminate the interference of residual magnetic signals on the current measurement, the magnetic marking measurement system must first demagnetize the cable; after demagnetization, the cable should be magnetized immediately so that magnetic marks can be applied to the cable, in preparation for subsequent reading of the magnetic marks to calculate the cable lowering depth (length).

[0028] Based on this, in a preferred embodiment of the present invention, a first demagnetizer for demagnetizing the cable and a first magnetizer for magnetizing the cable are installed before the first magnetizer; the first demagnetizer is located before the first magnetizer.

[0029] It also considers installing a magnetizer after the second magnetizer. Starting from the second magnetizer, the second magnetizer magnetizes the cable once every time a preset number of second magnetic signals are read. This not only provides a certain degree of verification supplement to the first magnetizer, but also provides a basis for calculating the cable laying depth from another time scale or perspective. The second demagnetizer installed before the second magnetizer can work in conjunction with the first demagnetizer to eliminate the cable's magnetic properties during cable retrieval, avoiding magnetic contamination during subsequent laying tests.

[0030] Based on this, in a preferred embodiment of the present invention, a second demagnetizer for demagnetizing the cable and a second magnetizer for magnetizing the cable are further installed below the second magnetic reader; the second demagnetizer is located before the second magnetizer; starting from the second magnetic reader, the second magnetizer magnetizes the cable once every time a preset number of second magnetic signals are read. The preset number is 40, but the implementer can customize it.

[0031] Please see Figure 3 It shows a schematic diagram of the composition and distribution of magnetic components in a magnetic marker measurement system provided by an embodiment of the present invention; Figure 3 In the process, the magnetic marker measurement system includes a total of 6 magnetic elements: two demagnetizers, two magnetizers, and two magnetizers; the black lines represent cables and indicate the positional intervals between adjacent magnetic elements; the cable passes through the first demagnetizer → first magnetizer → first magnetizer → second magnetizer → second demagnetizer → second magnetizer between the surface winch and the wellhead; the end of the cable is connected to the centralizer and fracturing tools, and begins to be lowered at the wellhead.

[0032] It should be noted that in the magnetic marker measurement system, the first demagnetizer and the second demagnetizer are normally open and used to demagnetize the cable. At the beginning of the cable descent, the first magnetizer first magnetizes the cable points it passes through and marks them with magnetic tags. After magnetization, the first magnetizer automatically enters the condition trigger state, that is, whenever the second magnetizer reads a magnetic tag peak value, it triggers the first magnetizer to immediately perform a magnetization. In this embodiment, the first magnetizer performs instantaneous magnetization, and the length of the magnetized area of ​​the magnetic mark made during each magnetization is no more than 5mm in the axial direction of the cable. In this embodiment, it is 2mm. The cable portion between adjacent magnetic mark points marked by the first magnetizer remains in a non-magnetized or weakly magnetized state to ensure that the cable has a discrete point magnetization distribution along the axial direction of the cable during the descent process. This avoids the first and second magnetizers reading the same magnetic mark intensity, which would prevent the descent measurement from being performed.

[0033] Taking the first cable point on the cable that passes the first magnetizer as an example (wherein, the cable point has already been demagnetized by the first demagnetizer before the cable is lowered); the first magnetizer magnetizes the demagnetized cable point and marks it with a magnetic mark. When the magnetic mark point (the cable point marked by the first magnetizer) passes the first and second magnetizers, the corresponding magnetic mark peak value will be detected respectively; when the second magnetizer reads a magnetic mark peak value, the first magnetizer will mark a second magnetic mark point at the cable passage point, and so on. Furthermore, starting from the cable lowering process, the first and second magnetic readers can be synchronized to read magnetic signals, and the reading frequency of both readers can be set to 100Hz. The implementer can also adjust the reading frequency according to the actual application. Thus, during the cable lowering process, the first magnetic signal read by the first magnetic reader and the second magnetic signal read by the second magnetic reader can be obtained at each moment.

[0034] Each moment refers to the synchronous magnetic reading moment of the magnetic reader. Both the first magnetic signal and the second magnetic signal contain the magnetic mark peak corresponding to the magnetic mark point on the lowering cable and the weak magnetic signal of the cable section between adjacent magnetic mark points.

[0035] Step S2: At each moment during the cable lowering process, based on the misalignment characteristics between the first magnetic signal and the second magnetic signal, obtain the reading magnetic misalignment time of the second magnetic reader relative to the first magnetic reader, and combine it with the positional distance between the first magnetic reader and the second magnetic reader to obtain the cable lowering speed.

[0036] Considering the installation distance between the first and second magnetic reading devices, the magnetic signal intensities read by the two devices at the same time during the cable lowering process are usually different, that is, the first magnetic signal and the second magnetic signal have certain spatiotemporal misalignment characteristics; and considering that the traditional Martin-Dike magnetic marking method tends to provide phased feedback, it usually estimates the approximate lowering depth of the cable based on the number of marking points, lacking continuous and real-time monitoring, it is difficult to accurately calculate the lowering depth of the cable when it is lowered to a non-marking point. The spatiotemporal misalignment between the first and second magnetic signals can help assess the time interval between the arrival of the same magnetic marker point at the first and second magnetic reading devices. This allows for the analysis of the cable lowering speed by combining the positional distance between the first and second magnetic reading devices. The cable lowering speed can, to some extent, compensate for the phased deficiencies of the Martin-Dike magnetic marking method, providing an instantaneous reference for the lowering depth from the perspective of dynamic cable lowering, thus preparing for subsequent accurate calculation of the cable lowering depth.

[0037] Based on this, the embodiments of the present invention first analyze the misalignment characteristics at each moment during the cable lowering process to determine the reading magnetic misalignment duration of the second magnetic reader relative to the first magnetic reader; wherein, the reading magnetic misalignment duration quantifies the spatiotemporal misalignment characteristics between the first magnetic signal and the second magnetic signal, and characterizes the time interval between the arrival of the same magnetic marker point at the first magnetic reader and the second magnetic reader; then, combined with the positional distance between the first magnetic reader and the second magnetic reader, the cable lowering speed is obtained.

[0038] Preferably, in one embodiment of the present invention, at each moment during the cable lowering process, to facilitate subsequent misalignment feature analysis between the first magnetic signal and the second magnetic signal, the time series corresponding to the first magnetic signal and the second magnetic signal are first fitted respectively; considering that the same magnetic marker point passes through the first magnetic reader first and then the second magnetic reader, the second magnetic signal corresponding to the same magnetic marker point usually lags behind the first magnetic signal. Therefore, subsequences of the same length can be continuously obtained from both ends of the time series corresponding to the first magnetic signal and the second magnetic signal. The difference between the two subsequences can help measure the misalignment matching situation, thereby helping to determine whether the two subsequences correspond to the same magnetic marker point or cable segment; considering that in the subsequence matching process, it is usually desirable to perform misalignment matching analysis on magnetic marker points with larger magnetic signal intensity to avoid baseline noise affecting the matching accuracy; based on this, the method for obtaining the magnetic reading misalignment duration includes: At each moment during the cable lowering process, the time sequences of the first magnetic signal and the second magnetic signal are fitted respectively; a first subsequence of a preset length is obtained from the starting point of the first magnetic signal time sequence along the time sequence direction, and a second subsequence of a preset length is obtained from the ending point of the second magnetic signal time sequence along the reverse time sequence direction, with the first subsequence and the second subsequence having the same sequence direction; Based on the distribution characteristics of the first magnetic signal in the first subsequence, obtain the anti-interference weight; based on the difference between the first subsequence and the second subsequence, obtain the sequence synchronization coefficient; use the anti-interference weight to weight the sequence synchronization coefficient to obtain the misalignment synchronization coefficient between the first subsequence and the second subsequence; Change the preset length to obtain the misalignment synchronization coefficient for each preset length; obtain the magnetic reading misalignment duration based on the preset length corresponding to the maximum misalignment synchronization coefficient.

[0039] Specifically, taking any moment during the cable lowering process as an example, up to that moment, all the first magnetic signals are used as sequence elements and sorted in time sequence (ordered chronologically) to obtain the first magnetic signal time sequence; similarly, the second magnetic signal time sequence is obtained; then, a preset length i is set, and the first i corresponding subsequences of the first magnetic signals in the first magnetic signal time sequence are extracted to obtain the first subsequence; the last i corresponding subsequences of the second magnetic signals in the second magnetic signal time sequence are extracted to obtain the second subsequence; wherein, the sequence direction of the first subsequence and the second subsequence are both time directions.

[0040] It should be noted that the preset length i needs to be determined in conjunction with the duration up to that moment. In this embodiment, the value range of the preset length i is [0.2T, T], where T is the duration up to that moment. The implementer can also adjust the value range of the preset length.

[0041] Then, the mean of all non-zero sequence elements in the first subsequence is divided by the largest sequence element in the first subsequence to obtain the anti-interference weight. The larger the non-zero sequence element, the stronger the magnetic signal in the first subsequence, the less affected by the baseline noise, and the larger the anti-interference weight. The Euclidean distance between the first and second subsequences is negatively correlated and normalized, for example, by mapping it to the exponential function exp(-x) with the natural constant e as the base, to obtain the sequence synchronization coefficient. Then, the anti-interference weight is multiplied by the sequence synchronization weight, and the product is used as the misalignment synchronization coefficient between the first and second subsequences. The smaller the Euclidean distance, the smaller the difference between the first and second subsequences, and the greater the possibility of misalignment synchronization of the subsequences.

[0042] By changing the preset length i, the misalignment synchronization coefficient between the first subsequence and the second subsequence can be obtained for each preset length.

[0043] In a preferred embodiment of the present invention, the preset length corresponding to the maximum misalignment synchronization coefficient is taken as the synchronous magnetic reading length; the misalignment matching effect between the two sub-sequences under the synchronous magnetic reading length is the best, and it is more likely to represent the magnetic signal sub-sequences corresponding to the same cable segment; then, the sequence length of the first magnetic signal time sequence can be subtracted from the synchronous magnetic reading length and divided by the magnetic reading frequency of the first magnetic reader to obtain the magnetic reading misalignment duration; the sequence length of the first magnetic signal time sequence minus the synchronous magnetic reading length is the sequence misalignment length, and the sequence misalignment length divided by the magnetic reading frequency can obtain the magnetic reading misalignment duration.

[0044] In other embodiments of the present invention, the implementer may also use cross-correlation analysis to evaluate the reading misalignment duration, that is: calculate the cross-correlation function between the first magnetic signal time sequence and the second magnetic signal time sequence, extract the time lag corresponding to the cross-correlation peak, and the time lag is the sequence misalignment length. Then, divide the sequence misalignment length by the reading frequency of the first magnetic reader to obtain the reading misalignment duration. Cross-correlation analysis is a known technique and will not be described in detail here.

[0045] The magnetic misalignment time represents the time difference when the same magnetic marker passes the first and second magnetic readers. After obtaining the magnetic misalignment time, the cable descent speed can be calculated by combining the positional distance between the first and second magnetic readers, which prepares for the subsequent calculation of the cable descent depth.

[0046] Preferably, in one embodiment of the present invention, considering that distance divided by time can yield speed, and the trend of speed change can also provide a speed reference to some extent; therefore, the method for obtaining the cable lowering speed includes: The positional distance between the first and second magnetic reading devices is taken as the magnetic reading misalignment distance; at each moment during the cable lowering process, the magnetic reading misalignment distance is divided by the magnetic reading misalignment duration to obtain the instantaneous speed of the cable; The trend weight of the cable descent speed is obtained by comparing the magnetic misalignment duration at each moment with the magnetic misalignment duration at the previous adjacent moment; the instantaneous speed of the cable is then weighted using the trend weight to obtain the cable descent speed.

[0047] In other embodiments, the implementer may also directly use the instantaneous speed of the cable as the cable lowering speed.

[0048] In a preferred embodiment of the present invention, considering that the calculated magnetic misalignment time at the previous adjacent moment is less than the magnetic misalignment time at the current moment, it indicates that the cable descent speed at the previous adjacent moment was relatively faster, and the cable has a certain deceleration trend at this moment, so the cable speed may be relatively low; based on this, a ratio can be used to measure the cable trend weight, which reflects the trend of the cable descent speed and provides a certain reference for evaluating the cable speed; the method for obtaining the cable trend weight includes: The ratio of the magnetic misalignment duration at the previous adjacent time point to the magnetic misalignment duration at each time point is used as the trend weight, where the magnetic misalignment duration at the previous adjacent time point is the numerator and the magnetic misalignment duration at each time point is the denominator.

[0049] It should be noted that, due to the spatial difference between the two magnetic readers, the reading misalignment time at each moment cannot be 0, and the denominator is always meaningful.

[0050] Step S3: During the cable lowering process, based on the time interval between each moment and the moment corresponding to the nearest previous second magnetic signal, as well as the cable lowering speed and the total number of second magnetic signals, the lowering depth of the stabilizer at each moment is obtained, and the cable lowering speed is adjusted in real time according to the lowering depth until the stabilizer is lowered to the preset target depth and then stopped and positioned for stabilization.

[0051] Considering that direct calculation based on the integral of the cable descent speed during the entire cable lowering process may have cumulative speed errors, thus affecting the calculation results; however, calculating the number of magnetic markers marked on the cable by the magnetic marker measurement system (which can also be regarded as the total number of the first magnetic signals or the total number of the second magnetic signals) can reliably measure the descent depth; at the same time, if at a certain moment the cable segment passing through the second magnetic reader may be between adjacent markers, there may be some cable segments that are not read and recorded by the second magnetic reader, making it impossible to estimate the descent depth corresponding to the cable segment, while the cable descent speed can help in the assessment; Based on this, after obtaining the cable lowering speed, the embodiments of the present invention further obtain the lowering depth of the centralizer at each moment according to the time interval between each moment and the moment corresponding to the nearest previous second magnetic signal, as well as the total number of cable lowering speeds and second magnetic signals; wherein, the cable lowering speed and the time interval are used to evaluate the approximate lowering depth of the cable segment that the magnetic marker measurement system cannot estimate, and then the lowering depth can be comprehensively evaluated by combining the magnetic marker measurement results.

[0052] Considering that the second magnetizer can help measure the total number of magnetic markers read by the second magnetizer in stages (i.e., the second magnetizer magnetizes the cable once every time a preset number of second magnetic signals are read), the number of magnetizations by the second magnetizer can also help assess the descent depth; the installation distance between the second magnetizer and the first magnetizer is 0.5m, which means that the cable descends by 0.5m for every magnetic marker read by the second magnetizer. Therefore, every time a preset number of 40 second magnetic signals are read or the second magnetizer magnetizes once, it means that the cable has descended by 20m. For example, at a certain moment, the second magnetic reader reads 60 second magnetic signals (the actual descent depth of the cable may exceed the 60th magnetic marker point, falling between the 60th and 61st magnetic marker points). The second magnetic injector will then inject magnetism once, and the cable will descend 20m, allowing for the assessment of the first descent depth. The remaining 20 second magnetic signals are not included in the first descent depth. Therefore, based on the logic that each magnetic marker point read by the second magnetic reader corresponds to a 0.5m cable descent, the second descent depth corresponding to these 20 second magnetic signals can be assessed. Furthermore, considering that when the descent depth falls between the 60th and 61st magnetic marker points, the portion of the cable exceeding the 60th magnetic marker point cannot be accurately determined based on the magnetic markers, the time interval between the previous second magnetic signal acquisition moment and this moment can be considered as the descent time for that portion of the cable. This time interval, combined with the cable descent speed, can be used to integrally assess the third descent depth. The sum of the descent depths of these three parts is the total descent depth. Based on this, in a preferred embodiment of the present invention, the method for obtaining the depth of descent includes: At each moment during the cable lowering process, the first lowering depth is obtained based on the positional distance between the first magnetizer and the second magnetizer, and the total number of magnetizers applied by the second magnetizer; the second lowering depth is obtained based on the positional distance between the first magnetizer and the second magnetizer, and the remainder after dividing the total number of second magnetic signals by a preset number; the third lowering depth is obtained based on the time interval between each moment and the moment corresponding to the most recent second magnetic signal, and the cable lowering speed; the sum of the first lowering depth, the second lowering depth, and the third lowering depth is taken as the lowering depth of the stabilizer.

[0053] In a preferred embodiment of the present invention, the method for obtaining the third depth includes: Between each time point and the time point corresponding to the most recent second magnetic signal, the integral of the cable lowering speed at all times is taken as the third lowering depth.

[0054] It should be noted that the number of magnetizations by the second magnetizer is recorded by an independent counter (such as counting the pulses of the drive circuit of the second magnetizer), which is a well-known technical method and will not be elaborated further.

[0055] Specifically, the positional distance between the first magnetizer and the second magnetizer is multiplied by a preset number, such as 40, and then multiplied by the total number of magnetizers of the second magnetizer to obtain the first lowering depth; the positional distance between the first magnetizer and the second magnetizer is multiplied by the remainder after dividing the total number of second magnetic signals by the preset number to obtain the second lowering depth; the change curve of the lowering speed of the cable at each moment is fitted between each moment and the moment corresponding to the most recent second magnetic signal, and the definite integral is calculated (a well-known technique, which will not be elaborated here) to obtain the third lowering depth; then the sum of the three is taken as the lowering depth of the cable or the stabilizer.

[0056] At each moment during the cable lowering process, after obtaining the lowering depth of the cable or the stabilizer, the cable lowering speed can be adjusted in real time according to the lowering depth until the stabilizer is lowered to the preset target depth and then stopped and positioned for stabilization. Precise depth positioning can reduce the positioning time of the stabilizer and improve the positioning and stabilization effect.

[0057] Preferably, in one embodiment of the present invention, the method for adjusting the cable lowering speed includes: When the lowering depth of the stabilizer is less than the preset deceleration depth, it does not interfere with the cable lowering speed; when the lowering depth of the stabilizer is greater than or equal to the preset deceleration depth, the cable lowering speed is reduced to the preset speed; wherein, the preset deceleration depth is less than the preset target depth.

[0058] It should be noted that in this embodiment, the preset target depth is the target descent depth of the stabilizer. In this embodiment, it is set to 400 meters, so the preset deceleration depth is 398m. That is, at a position 2m above the preset target depth, the cable descent speed is reduced to a preset speed, which is less than or equal to 1m / min. In this embodiment, the value is 0.5m / min.

[0059] When the preset target depth is reached, the control cable stops descending, and the stabilizer and tools also stop descending. Due to the presence of the air cavity, under the action of pressure difference, the cone 7 drives the connecting sleeve 4, the moving piston 3, and the locking ring 6 to move downward along the outer wall of the central tube 2. When the protective mechanism of the cone 7 contacts the upper end of the outer sleeve 8, it stops moving under the limiting action of the protective mechanism. The locking ring 6 inside the cone 7 will lock onto the teeth of the outer wall of the central tube 2 that mate with the locking ring 6, and the stabilizing function of the positioning and stabilizing mechanism of the outer sleeve 8 will be officially activated.

[0060] Based on the same inventive concept, the present invention also proposes a positioning and straightening device for downhole tubing, including a straightening device body and a positioning and straightening system; the positioning and straightening system is used to perform a positioning and straightening method for downhole tubing described in steps S1-S3 above.

[0061] In summary, this invention acquires the first magnetic signal of the cable connected to the centralizer when it passes the first magnetic sensor and the second magnetic signal when it passes the second magnetic sensor during the cable descent process. Then, at each moment during the cable descent, based on the misalignment characteristics between the first and second magnetic signals, the misalignment time of the second magnetic sensor relative to the first magnetic sensor is obtained. Combined with the positional distance between the first and second magnetic sensors, the cable descent speed is obtained. Furthermore, based on the time interval between each moment and the moment corresponding to the nearest previous second magnetic signal, and the total number of second magnetic signals and the cable descent speed, the descent depth of the centralizer at each moment is obtained. The cable descent speed is adjusted in real time according to the descent depth until the centralizer reaches a preset target depth and is then positioned and centralized. This invention uses a magnetic marker measurement method to continuously mark magnetic marker points during the cable descent process to calculate the descent depth. It also uses the misalignment reading time between different magnetic sensors to evaluate the cable descent speed, supplementing the calculation of the descent depth of the cable that has already descended but cannot be accurately measured by the magnetic markers. This accurately positions the centralizer, thereby improving the accuracy of positioning and centralizing downhole tubing.

[0062] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0063] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for positioning and straightening downhole tubing, characterized in that, The method includes: The system acquires the first magnetic signal when the cable connected to the stabilizer passes the first magnetic reader during the lowering process, and the second magnetic signal when it passes the second magnetic reader; wherein the second magnetic reader is located after the first magnetic reader, and the two magnetic readers read magnetic signals synchronously. At each moment during the cable lowering process, based on the misalignment characteristics between the first magnetic signal and the second magnetic signal, the reading misalignment time of the second magnetic reader relative to the first magnetic reader is obtained, and combined with the positional distance between the first magnetic reader and the second magnetic reader, the cable lowering speed is obtained; During the cable lowering process, the lowering depth of the stabilizer at each moment is obtained based on the time interval between each moment and the moment corresponding to the nearest previous second magnetic signal, as well as the cable lowering speed and the total number of second magnetic signals. The cable lowering speed is adjusted in real time according to the lowering depth until the stabilizer is lowered to the preset target depth and then stopped and positioned for stabilization. The method for obtaining the magnetic read misalignment duration includes: At each moment during the cable lowering process, the time sequences of the first magnetic signal and the second magnetic signal are fitted respectively; a first subsequence of a preset length is obtained from the starting point of the first magnetic signal time sequence along the time sequence direction, and a second subsequence of a preset length is obtained from the ending point of the second magnetic signal time sequence along the reverse time sequence direction, with the first subsequence and the second subsequence having the same sequence direction; Based on the distribution characteristics of the first magnetic signal in the first sub-sequence, an anti-interference weight is obtained; based on the difference between the first sub-sequence and the second sub-sequence, a sequence synchronization coefficient is obtained; the sequence synchronization coefficient is weighted using the anti-interference weight to obtain the misalignment synchronization coefficient between the first sub-sequence and the second sub-sequence. Change the preset length to obtain the misalignment synchronization coefficient for each preset length; obtain the magnetic reading misalignment duration based on the preset length corresponding to the maximum misalignment synchronization coefficient. Obtaining the anti-interference weights includes: dividing the mean of all non-zero sequence elements in the first subsequence by the largest sequence element in the first subsequence to obtain the anti-interference weights; Obtaining the misalignment synchronization coefficient includes: normalizing the Euclidean distance between the first subsequence and the second subsequence with negative correlation to obtain the sequence synchronization coefficient; then multiplying the anti-interference weight and the sequence synchronization weight, and using the product as the misalignment synchronization coefficient between the first subsequence and the second subsequence; The magnetic misalignment duration is obtained based on the preset length corresponding to the maximum misalignment synchronization coefficient, including: The preset length corresponding to the maximum misalignment synchronization coefficient is taken as the synchronous magnetic reading length; the sequence length of the first magnetic signal timing sequence is subtracted from the synchronous magnetic reading length, and then divided by the magnetic reading frequency of the first magnetic reader to obtain the magnetic reading misalignment duration.

2. The method for positioning and straightening downhole tubing according to claim 1, characterized in that, Before the first magnetic reader, there is a first demagnetizer for demagnetizing the cable and a first magnetizer for magnetizing the cable; the first demagnetizer is located before the first magnetizer; below the second magnetic reader, there is a second demagnetizer for demagnetizing the cable and a second magnetizer for magnetizing the cable; the second demagnetizer is located before the second magnetizer; starting from the second magnetic reader, whenever a preset number of second magnetic signals are read, the second magnetizer magnetizes the cable once.

3. The method for positioning and straightening downhole tubing according to claim 1, characterized in that, The method for obtaining the cable lowering speed includes: The positional distance between the first and second magnetic reading devices is taken as the magnetic reading misalignment distance; at each moment during the cable lowering process, the magnetic reading misalignment distance is divided by the magnetic reading misalignment duration to obtain the instantaneous speed of the cable; Based on the magnetic misalignment duration at each moment and the magnetic misalignment duration at the previous adjacent moment, the trend weight of the cable descent speed is obtained; the instantaneous speed of the cable is weighted using the trend weight to obtain the cable lowering speed.

4. The method for positioning and straightening downhole tubing according to claim 3, characterized in that, The methods for obtaining the trend weights include: The ratio of the magnetic misalignment duration at the previous adjacent time point to the magnetic misalignment duration at each time point is used as the trend weight, where the magnetic misalignment duration at the previous adjacent time point is the numerator.

5. The method for positioning and straightening downhole tubing according to claim 2, characterized in that, The method for obtaining the depth of descent includes: At each moment during the cable lowering process, a first lowering depth is obtained based on the positional distance between the first magnetizer and the second magnetizer, and the total number of magnetizers applied by the second magnetizer; a second lowering depth is obtained based on the positional distance between the first magnetizer and the second magnetizer, and the remainder after dividing the total number of second magnetic signals by a preset number; a third lowering depth is obtained based on the time interval between each moment and the moment corresponding to the most recent second magnetic signal, and the cable lowering speed. The sum of the first, second, and third lowering depths is taken as the lowering depth of the stabilizer.

6. The method for positioning and straightening downhole tubing according to claim 5, characterized in that, The method for obtaining the third depth includes: Between each time point and the time point corresponding to the most recent second magnetic signal, the integral of the cable lowering speed at all times is taken as the third lowering depth.

7. The method for positioning and straightening downhole tubing according to claim 5, characterized in that, The method for adjusting the cable lowering speed includes: When the lowering depth of the stabilizer is less than the preset deceleration depth, it does not interfere with the cable lowering speed; when the lowering depth of the stabilizer is greater than or equal to the preset deceleration depth, the cable lowering speed is reduced to the preset speed; wherein, the preset deceleration depth is less than the preset target depth.

8. A positioning and straightening device for downhole tubing, comprising a straightening body, characterized in that, It also includes a positioning and straightening system; the positioning and straightening system is used to perform the steps in the positioning and straightening method for a downhole tubing as described in any one of claims 1 to 7.

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