Downhole heating paraffin prevention sub device and method based on ultrasonic detection

Abstract

The application discloses a downhole heating and wax-preventing short section device and method based on ultrasonic detection, and belongs to the technical field of oil and gas field development. The downhole heating and wax-preventing short section device comprises a shell and an inner cylinder in the shell, the inner cylinder is in communication with an oil pipe, and a heating system and an ultrasonic detection system are arranged between the shell and the inner cylinder. The downhole heating and wax-preventing short section device is arranged in a wax-prone area of the oil pipe, the ultrasonic detection system is connected with a judgment system, and the heating system is controlled through the judgment system. The ultrasonic detection system periodically emits ultrasonic signals and receives corresponding echo signals, and the waxing state of the oil pipe is detected in a timing mode. The judgment system analyzes the ultrasonic echo signals, extracts multi-dimensional features and quantitatively evaluates the waxing degree. The heating system dynamically adjusts the output power according to the evaluation result, realizes accurate heating of the oil pipe waxing and removes the deposited wax. The application forms an integrated closed-loop monitoring system of waxing detection, evaluation and treatment, and realizes online monitoring and active treatment of the waxing state of the oil pipe.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development technology, and specifically relates to a downhole heating anti-wax sub-section device and method based on ultrasonic detection. Background Technology

[0002] During oil and gas field development, waxes contained in crude oil precipitate and deposit on the inner wall of the tubing as temperature decreases and pressure changes, forming a wax deposit. This wax deposit reduces the effective flow cross-sectional area, increases fluid flow and downhole tool resistance, leading to decreased well production and reduced tool life. In severe cases, it can cause localized well blockage, affecting normal well production.

[0003] Existing research methods mainly focus on electromagnetic wax prevention and thermal energy-driven wax treatment technologies for oil wells. Chinese patent application CN117759202A discloses an intelligent electromagnetic heating wax removal system for oil wells, which uses the tubing as a resistance heating element to melt and remove wax. Chinese patent CN208966274U discloses a self-heating wax prevention and removal device for oil wells, which uses permanent magnets arranged on the sucker rod, combined with external electromagnetic induction heating and resistance heating structures to achieve coordinated magnetic field control and dual heating within the wellbore, thus preventing and removing wax. Both technologies are based on thermal energy-driven technology, focusing on the passive treatment of existing or potential wax deposits. Existing wax monitoring methods mostly rely on indirect judgment based on changes in production parameters, lacking direct, quantitative detection methods for the wax state inside the wellbore, making it difficult to accurately identify and dynamically control the degree of wax deposition. Summary of the Invention

[0004] To address the above problems, this invention provides a downhole heating anti-wax sub-device and method based on ultrasonic detection. It utilizes ultrasonic signal detection to monitor wax buildup in the wellbore at regular intervals. Combined with echo signal analysis, multi-dimensional feature extraction, and a support vector machine model, it quantitatively assesses the degree of wax buildup. Based on the assessment results, it dynamically controls the heating of the wax-covered area in the wellbore, achieving precise control of heating and active removal of wax.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A downhole heating and anti-wax sub is disclosed based on ultrasonic detection. The downhole heating and anti-wax sub is installed in the wax-accumulating area of ​​the tubing. It includes an outer shell that can be connected to the tubing, an inner cylinder in the middle of the outer shell, a heating system between the outer shell and the inner cylinder, a flow channel in the middle of the inner cylinder that communicates with the tubing, and an ultrasonic detection system on the inner wall of the inner cylinder. The ultrasonic detection system is connected to a judgment system, which is also connected to the heating system. The judgment system receives and processes the echo signals from the ultrasonic detection system, performs information identification and analysis, and controls the heating system based on the analysis results.

[0007] Furthermore, the ultrasonic detection system includes multiple ultrasonic transceivers, which are divided into one or more groups and disposed within the ultrasonic sensing layer. The multiple groups of ultrasonic transceivers are arranged at intervals along the length of the inner cylinder. The ultrasonic sensing layer is disposed inside the inner cylinder, and the multiple ultrasonic transceivers in the same group are arranged in a circumferential array along the inner wall of the inner cylinder.

[0008] Furthermore, the judgment system includes a signal receiving module, a signal processing module, an information comparison module, and a control module. The signal receiving module receives echo signals from multiple ultrasonic transceivers, amplifies, filters, and reduces noise in the ultrasonic echo signals, and transmits the signals to the signal processing module. The signal processing module performs digital filtering and envelope sampling on the signals and transmits the processed information to the information comparison module. The information comparison module extracts features from the envelope signals, uses a support vector machine model to identify the wax deposition state based on the feature information, and transmits the identification result to the control module. The control module analyzes the identification result and transmits an execution signal to the heating system.

[0009] Furthermore, the heating system is an electromagnetic coil used to heat the inner cylinder to increase the temperature of the inner wall of the wellbore and achieve the purpose of dewaxing; the electromagnetic coil is controlled by a judgment system.

[0010] Furthermore, the inner cylinder is wrapped with an insulating layer, and the inner cylinder is made of metal; the insulating layer is disposed between the electromagnetic coil and the inner cylinder to prevent short circuits.

[0011] This invention also provides a downhole heating method for preventing wax deposition based on ultrasonic detection, comprising the following steps:

[0012] Step 1: Assemble the above-mentioned downhole heating and anti-wax sub, connect both ends of the downhole heating and anti-wax sub to the tubing, and place the downhole heating and anti-wax sub in the wax-deposited area of ​​the tubing;

[0013] Step 2: The ultrasonic testing system sends ultrasonic waves at specified time intervals and transmits the received corresponding ultrasonic echoes to the judgment system. The judgment system then generates a heating signal based on the echo signal from the ultrasonic testing system.

[0014] Step 3: The digital controller of the heating system generates a target control power input based on the heating signal and sends it to the PID controller. The PID controller calculates the error between the target control power and the real-time feedback power, outputs the control quantity, and generates the corresponding PWM modulation signal. The generated PWM modulation signal is transmitted to the power drive unit. The power drive unit controls the on / off state of the power supply circuit of the electromagnetic coil of the heating system according to the PWM duty cycle and adjusts the input power of the electromagnetic coil. The Hall current sensor is installed in the power supply circuit of the electromagnetic coil to collect the current signal of the coil in real time, calculate the actual current and equivalent power value, and feed it back to the PID controller.

[0015] Step 4: Repeat steps 1, 2, and 3 to continuously monitor the wax deposits in the wellbore. The system identifies the wax deposits and controls the heating system to melt them, thus achieving closed-loop monitoring and cleaning of the wax deposits in the tubing.

[0016] Furthermore, the signal receiving module of the judgment system includes an ultrasonic transducer, a processor, and a memory. The ultrasonic transducer is used to receive ultrasonic echo signals, and the processor is used to call and execute the signal processing program stored in the memory to sequentially perform gain adjustment, bandpass filtering, and noise reduction processing on the echo signals.

[0017] The signal processing module is used to perform digital bandpass filtering and envelope extraction on the processed signal in sequence, and output the envelope signal.

[0018] The output of the signal processing module is connected to the input of the information comparison module. The information comparison module is used to extract the envelope signal, obtain the echo energy change information, and perform multi-dimensional feature extraction based on the envelope signal. The extracted feature data is normalized and differentially processed to generate a standardized feature vector, which is then input into the support vector machine model. The support vector machine model judges the degree of wax deposition. The support vector machine model evaluates the degree of wax deposition in the tubing based on the standard feature vector of the degree of wax deposition and transmits the evaluation result to the control module.

[0019] Furthermore, the multi-dimensional features include time-domain statistical features, energy features, attenuation features, and frequency-domain features. The time-domain statistical features include echo propagation time method, peak arrival time, and echo delay time. The energy features include total energy and segmented energy ratio. The attenuation features include echo amplitude attenuation coefficient and multiple echo attenuation rate. The frequency-domain features include spectral centroid, dominant frequency, bandwidth, and high-frequency energy proportion.

[0020] Furthermore, the support vector machine model compares the real-time monitoring results with the data under the waxing degree standard, outputs the waxing degree judgment result of the tubing, and transmits it to the control module; the control module calculates the corresponding target heating temperature T based on the evaluation result and the function model between the waxing degree and the target heating temperature. The function model is as follows:

[0021]

[0022] In the formula: Normal wellbore temperature, ℃; Maximum safe heating temperature, ℃; The degree of wax buildup is calculated using a comprehensive judgment model; The wax deposition sensitivity coefficient is determined experimentally.

[0023] Finally, the calculated target heating temperature is used to generate a heating signal, which is then transmitted to the heating system.

[0024] The technological advancements achieved by this invention compared to existing technologies are as follows:

[0025] This invention utilizes a downhole heating and anti-wax sub-unit installed in areas of the tubing prone to wax buildup. An ultrasonic detection system periodically emits ultrasonic signals and receives corresponding echo signals to monitor the wax buildup status of the tubing. A judgment system analyzes the ultrasonic echo signals, extracts multi-dimensional features, and quantitatively assesses the degree of wax buildup. The heating system dynamically adjusts its output power based on the assessment results, achieving precise heating and removal of the deposited wax. This invention constructs an integrated closed-loop monitoring system encompassing "monitoring-assessment-control-execution" for wax detection, assessment, and remediation, enabling online monitoring and proactive remediation of tubing wax buildup to improve the stability and efficiency of oil well production. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0027] In the attached diagram:

[0028] Figure 1 This is a schematic diagram of the connection between a downhole heated anti-wax sub based on ultrasonic detection and a judgment system provided in an embodiment of the present invention;

[0029] Figure 2 This is a schematic cross-sectional view of the downhole heating anti-wax sub-section device in an embodiment of the present invention;

[0030] Figure 3 This is a closed-loop control diagram of the heating system in this invention;

[0031] Figure 4 This is the closed-loop monitoring and control diagram of the judgment system in this invention.

[0032] In the picture:

[0033] 1-Outer shell; 2-Inner cylinder; 3-Ultrasonic transceiver; 4-Ultrasonic sensing layer; 5-Electromagnetic coil; 6-Insulation layer; 7-Signal receiving module; 8-Signal processing module; 9-Information comparison module; 10-Control module. Detailed Implementation

[0034] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0035] like Figure 1 , Figure 2 As shown, a downhole heating and wax-prevention sub is provided based on ultrasonic detection. The sub is installed in the wax-prone area of ​​the tubing and includes an outer shell 1 connected to the tubing. An inner cylinder 2 is located in the middle of the outer shell 1. A heating system is located between the outer shell 1 and the inner cylinder 2. A flow channel communicating with the tubing is located in the middle of the inner cylinder 2. An ultrasonic detection system is installed on the inner wall of the inner cylinder 2. The ultrasonic detection system is connected to a judgment system, which is also connected to the heating system. The judgment system receives and processes the echo signals from the ultrasonic detection system, performs information identification and analysis, and controls the heating system based on the analysis results. This scheme uses ultrasonic signals to periodically detect the wax buildup in the tubing. The judgment system analyzes the ultrasonic echo signals, extracts features, and quantitatively assesses the degree of wax buildup. The heating system dynamically adjusts its output power based on the assessment results, forming an integrated closed-loop control system for wax detection, assessment, and treatment. This system enables real-time monitoring, quantitative assessment, precise heating, and intelligent active removal of wax buildup in the tubing. During actual assembly, the downhole heating and anti-wax section device can be installed inside the tubing or between two adjacent tubing sections.

[0036] In its specific design, the ultrasonic detection system includes multiple ultrasonic transceivers 3. These transceivers 3 are arranged in one or more groups within the ultrasonic sensing layer 4. The groups of transceivers 3 are spaced apart along the length of the inner cylinder 2. The ultrasonic sensing layer 4 is located inside the inner cylinder 2, and multiple transceivers 3 in the same group are arranged in a circumferential array along the inner wall of the inner cylinder 2. The ultrasonic sensing layer is made of 316L stainless steel, meeting the requirements of complex downhole conditions and providing excellent structural strength. The ultrasonic transceivers 3 are Olympus V306 water-immersed ultrasonic probes, employing high-temperature, high-pressure ultrasonic transducers. An external sealed metal shell provides waterproofing and pressure resistance, ensuring stable operation under complex downhole conditions and enabling effective transmission and reception of ultrasonic signals. The ultrasonic transceivers 3 transmit detection ultrasonic waves at preset time intervals and receive the returned ultrasonic signals, enabling multi-angle detection of wax deposition distribution on the inner wall of the wellbore, improving the detection range and anti-interference capability. The specific distribution of the ultrasonic transceivers 3 is as follows: Figure 1 , 2 As shown.

[0037] In specific manufacturing, the heating system is an electromagnetic coil 5. When the electromagnetic coil 5 is energized, it generates an alternating magnetic field that acts on the inner cylinder 2. Under the resistance of the inner cylinder 2, Joule heating is generated, thereby increasing the temperature of the inner cylinder 2 and dissolving the wax deposited on the well wall. The electromagnetic coil 5 is connected to a controller, which is controlled by a judgment system. The inner cylinder 2 is wrapped with an insulating layer 6, and the inner cylinder 2 is made of metal. The insulating layer 6 prevents short circuits between the inner cylinder 2 and the electromagnetic coil 5.

[0038] In specific embodiments of the present invention, such as Figure 1As shown, the judgment system includes a signal receiving module 7, a signal processing module 8, an information comparison module 9, and a control module 10. The signal receiving module 7 receives echo signals from multiple ultrasonic transceivers 3, amplifies, filters, and reduces noise in the ultrasonic echo signals, and transmits the signals to the signal processing module 8. The signal processing module 8 performs digital filtering and envelope sampling on the signals and transmits the processed information to the information comparison module 9. The information comparison module 9 extracts features from the envelope signals, uses a support vector machine model to identify the wax deposition state based on the feature information, and transmits the identification result to the control module 10. The control module 10 analyzes the identification result and transmits the execution signal to the heating system. The signal receiving module 7 uses the AFE5808 ultrasonic analog front-end chip to acquire and amplify multiple ultrasonic echo signals; the signal processing module 8 and the information comparison module 9 use the Zynq UltraScale XCZU7EG chip, whose programmable logic part works with the processor system to realize signal processing and information comparison functions, meeting the efficient signal processing requirements of the judgment system; the control module 10 uses the STM32H743 core microcontroller to meet the timing control and power regulation of the heating system, realizing dynamic heating control of the wax deposition area in the oil pipe.

[0039] like Figure 3 As shown, the heating system receives a heating signal from the control module 10. After processing by the digital controller, a target control power is generated and input to the PID controller. The PID controller calculates and outputs the error between the target control power and the feedback power collected and calculated by the Hall current sensor, and generates a corresponding PWM modulation signal. The PWM modulation signal is input to the power drive unit, which controls the duty cycle of the power supply to the electromagnetic coil 5 via the watertight cable to adjust the input power of the electromagnetic coil 5. The watertight cable supplies power to the electromagnetic coil 5, thereby heating the target structure. An insulation layer 6 is installed between the inner cylinder 2 and the electromagnetic coil 5 to prevent short circuits. The Hall current sensor is installed in the power supply circuit of the electromagnetic coil 5 to collect the current signal of the coil in real time, calculate the actual current and equivalent power value, and feed it back to the PID controller to achieve closed-loop control.

[0040] In specific manufacturing, the electromagnetic coil 5 is made of enameled copper wire with an outer insulating varnish film, allowing it to be tightly wound to form an effective electromagnetic coil without short circuits; the insulation layer 6 is made of polyimide material, which meets the requirements of complex downhole working conditions and has good temperature resistance, chemical corrosion resistance, and mechanical strength; the inner cylinder 2 is made of carbon steel N80 material to ensure that eddy currents can be effectively generated under alternating magnetic fields and achieve stable Joule heating, while meeting the engineering requirements of high temperature, high pressure, and corrosive environments downhole; the digital controller is a TMS320F28069 microcontroller, which meets the needs of real-time system control and has a high-performance PWM module to achieve precise adjustment of electromagnetic heating power; the Hall current sensor is an LA 55-P type current sensor to meet the real-time monitoring of the current in the electromagnetic coil 5 circuit; the power drive unit uses an FF50R12KT4 type IGBT module as a power switching device, and works with an IR2110 gate drive chip to achieve drive control of the IGBT, which meets the requirement of converting the PWM modulation signal into high-power power supply to the electromagnetic coil 5, thereby achieving adjustment of heating power.

[0041] This invention also provides a downhole heating method for preventing wax deposition based on ultrasonic detection, comprising the following steps:

[0042] Step 1: Assemble the above-mentioned downhole heating and anti-wax sub-section device, with the outer diameter of the outer shell matching the outer diameter of the connected tubing; connect both ends of the downhole heating and anti-wax sub-section device to the tubing, and place the downhole heating and anti-wax sub-section device in the upper and middle sections of the tubing where wax is easily deposited; multiple sections can be arranged.

[0043] exist Figure 1 In the embodiment shown, 16 ultrasonic transceivers are installed, 8 of which are arranged in an array and evenly distributed in a ring in the inner cylinder flow channel, simultaneously transmitting detection ultrasonic waves according to a preset time interval.

[0044] Step 2: The ultrasonic testing system transmits ultrasonic signals at a frequency of 1 MHz at 5-minute intervals and transmits the corresponding ultrasonic echoes received to the signal receiving module 7 of the judgment system. The judgment system then generates a heating signal based on the echo signals from the ultrasonic testing system. Specifically, this includes the following steps:

[0045] (1) The signal receiving module 7 includes an ultrasonic transducer, a processor and a memory. The ultrasonic transducer is used to receive ultrasonic echo signals. The processor is used to call and execute the signal processing program stored in the memory to perform gain adjustment, bandpass filtering and noise reduction processing on the echo signals in sequence.

[0046] The signal processing program includes a gain adjustment program, a bandpass filtering program, and a noise reduction program. The gain adjustment program is used to perform programmable gain amplification of the ultrasonic echo signal and output a first-stage amplified signal with stable amplitude. The bandpass filtering program is used to perform bandpass filtering on the first-stage amplified signal to extract the effective frequency components of the ultrasonic echo signal, suppress low-frequency drift and high-frequency interference, and output a second-stage filtered signal with improved spectral consistency.

[0047] The noise reduction program is used to perform wavelet transform noise reduction on the second-level filtered signal to remove random noise and retain the transient characteristics of the echo signal, and output a third-level processed signal with improved signal-to-noise ratio and feature stability.

[0048] (2) Signal processing module 8 is used to perform digital bandpass filtering and envelope extraction on the third-level processed signal in sequence, and output the envelope signal;

[0049] Signal processing module 8 uses a 4th-order Butterworth digital bandpass filter to select the frequency band of the ultrasonic echo signal, suppressing out-of-band noise and maintaining signal waveform stability. The filtered signal is then subjected to a Hilbert transform to construct an analytical signal and extract its envelope signal, thereby converting the high-frequency oscillation signal into a low-frequency envelope signal reflecting changes in echo energy, providing a stable data foundation for subsequent wax deposition feature extraction.

[0050] (3) The output of the signal processing module 8 is connected to the input of the information comparison module 9. The information comparison module 9 is used to extract the envelope signal, obtain the echo energy change information, and perform multi-dimensional feature extraction based on the envelope signal. The multi-dimensional features include time-domain statistical features, energy features, attenuation features and frequency-domain features. The time-domain statistical features include echo propagation time, peak arrival time and echo delay time. The energy features include total energy and segmented energy ratio. The attenuation features include echo amplitude attenuation coefficient and multiple echo attenuation rate. The frequency-domain features include spectral centroid, main frequency, bandwidth and high-frequency energy ratio.

[0051] The extracted feature data is normalized and differentially processed to generate standardized feature vectors, which are then input into the support vector machine model.

[0052] (4) The support vector machine model determines the degree of wax deposition; the support vector machine model evaluates the degree of wax deposition in the tubing based on the standard feature vector of the degree of wax deposition, and transmits the evaluation results to the control module 10. Among them, the methods for the support vector machine model to determine the degree of wax deposition in the wellbore include the propagation time method, the echo amplitude attenuation method, the acoustic impedance reflection method, the spectrum change method, and the comprehensive judgment model.

[0053] The method of calculating wax deposition index based on echo amplitude attenuation is based on the propagation attenuation law of ultrasonic waves in a medium, and is achieved by obtaining the current echo amplitude. Initially in a wax-free state As a benchmark, the attenuation coefficient of the underlying medium is considered. and transmission distance To mitigate the impact of signal attenuation, a wax sensitivity coefficient is introduced. The following model for evaluating the degree of wax deposition based on the change in echo amplitude is established:

[0054]

[0055] In the formula: The degree of waxing is an index calculated based on the echo amplitude attenuation method (dimensionless, value 0-1). This is the initial echo amplitude (baseline state without wax buildup); This represents the current detected echo amplitude. L is the attenuation coefficient of the underlying medium, dB / cm (e.g., oil or air); L is the ultrasonic propagation distance, cm.

[0056] Among them, the basic medium attenuation coefficient The preferred value is 0.8 dB / cm, and the preferred ultrasonic propagation distance L is 3 cm.

[0057] Measurement of current echo reflection coefficient based on acoustic impedance reflection method Compared with the reference reflectance without wax deposits A calculation model for judging the degree of wax buildup was constructed by combining the acoustic impedance parameters of oil, wax, and 316L stainless steel:

[0058]

[0059] In the formula: The degree of wax deposition is an index calculated based on the acoustic impedance variation method (dimensionless, value 0-1). The current echo reflection coefficient (dimensionless); The reflectance coefficient is a wax-free reference (dimensionless). Acoustic impedance of the ultrasonic sensing layer, Rayl; Rayl is the acoustic impedance of the equivalent input at the calibrated upper limit.

[0060] Acoustic impedance of ultrasonic sensing layer 4.6×10 7 Rayl's baseline reflection coefficient R0 at the oil-metal interface in the unwaxed state is approximately 0.945. As the degree of wax deposition increases, the echo reflection coefficient R gradually decreases, ranging from 0.8 to 0.96.

[0061] Based on the spectral variation method, the high and low frequency energy distribution and relative changes of ultrasonic signals are analyzed to characterize the spectral migration effect caused by wax deposition. The calculation model for the degree of wax deposition is as follows:

[0062]

[0063] In the formula: This is an index of wax deposition degree calculated based on the spectral variation method (dimensionless, value 0-1); High-frequency energy; Low-frequency energy; This is the baseline value without wax.

[0064] The difference between the current ultrasonic wave propagation time and the propagation time under a wax-free baseline condition is obtained based on the propagation time variation method. This characterizes the change in ultrasonic propagation medium caused by wax deposition. When the ultrasonic medium changes from an oil phase to a wax phase, the different sound velocities cause changes in ultrasonic wave propagation time. A wax deposition characteristic index based on propagation time variation is established.

[0065]

[0066] In the formula: The wax deposition characteristic index (dimensionless, value 0-1) is obtained based on the propagation time variation method. This represents the current measured propagation time of the ultrasonic wave; Ultrasonic propagation time in a wax-free reference state under the same conditions.

[0067] Considering that the propagation of ultrasonic signals is related to pressure and temperature, calibration experiments were conducted under wax-free reference conditions with different combinations of temperature and pressure to establish the correspondence between temperature and pressure parameters in the wax-free reference system.

[0068]

[0069] Note: Measurement conditions: ultrasonic frequency 1 MPa, ultrasonic propagation distance L = 3 cm, acoustic impedance of ultrasonic sensing layer 4.6 × 10⁻⁶ 7 Rayl, oil acoustic impedance 1.2×10 6 Rayl.

[0070] Based on the calculated wax deposition indices, a four-dimensional feature vector is established.

[0071]

[0072] Ultrasonic testing data under different wax deposition levels were obtained experimentally. Four-dimensional feature vectors under different wax deposition levels were used as standard feature vectors to establish a standard sample library for wax deposition levels, and a comprehensive judgment model was established. The results of the standard feature vectors and their corresponding wax deposition level interpretation values ​​are shown in the table below:

[0073]

[0074] The four-dimensional feature vectors obtained in real-time detection are input into a support vector machine (SVM) model. The SVM model classifies the real-time four-dimensional feature vectors, determines the waxing degree interval to which the real-time four-dimensional feature vectors belong, and calculates the Euclidean distance between the real-time four-dimensional feature vectors and the standard feature vectors within that waxing degree interval. The Euclidean distance formula is:

[0075]

[0076] In the formula: Euclidean distance; Real-time echo amplitude attenuation and wax deposition index; The i-th standard echo amplitude attenuation waxing degree index; Real-time acoustic impedance reflection wax deposition index; The i-th standard acoustic impedance reflection wax degree index; Real-time spectrum migration wax deposition index; The i-th standard spectral migration wax deposition index; Real-time propagation time wax deposition index; The i-th standard propagation time wax deposition index.

[0077] The position of the real-time four-dimensional feature vector between adjacent standard vectors is determined based on the calculated Euclidean distance. A distance-weighted interpolation method is then used to calculate the real-time wax deposition level assessment value. The calculation formula is as follows:

[0078]

[0079] In the formula: Real-time wax deposition assessment value; The degree of wax deposition judgment value corresponding to the first standard feature vector; The degree of wax deposition judgment value corresponding to the second standard feature vector; The Euclidean distance between the real-time four-dimensional feature vector and the first standard feature vector; The Euclidean distance between the real-time four-dimensional feature vector and the second standard feature vector;

[0080] The calculated real-time waxing degree judgment value is not limited to the discrete waxing level in the table, but can change continuously in the range of 0 to 1, thereby realizing the quantitative characterization of the waxing degree of the tubing.

[0081] The support vector machine model compares the real-time monitoring results with the data under the wax deposition standard and outputs the wax deposition degree judgment result of the tubing to the control module 10; the control module 10 calculates the corresponding target heating temperature T based on the wax deposition degree assessment result and the function model between the wax deposition degree and the target heating temperature. The mapping function model is as follows:

[0082]

[0083] In the formula: Normal wellbore temperature, ℃; Maximum safe heating temperature, ℃; The degree of wax buildup is calculated using a comprehensive judgment model; The wax deposition sensitivity coefficient is determined experimentally.

[0084] Experimental measurements =40~55℃, =150℃, =0.774. The calculated target heating temperature generates a heating signal, which is transmitted to the heating system to execute the heating operation. The ultrasonic echo signal is fed back at preset time intervals to form a closed-loop monitoring and control.

[0085] Step 3: The digital controller of the heating system generates a target control power input to the PID controller based on the heating signal. The PID controller performs calculations based on the error between the target control power and the real-time feedback power, outputs the control quantity, and generates the corresponding PWM modulation signal. The generated PWM modulation signal is transmitted to the power drive unit. The power drive unit controls the on / off state of the heating system based on the PWM duty cycle and adjusts the input power of the heating system.

[0086] Specifically, it includes the following steps:

[0087] (1) In the heating system, the digital controller generates the target control power based on the heating signal and inputs it to the PID controller. The PID controller performs calculations based on the error between the target control power and the real-time feedback power, outputs the control quantity, and generates the corresponding PWM modulation signal.

[0088] The main function of a PID controller is to eliminate steady-state errors and improve dynamic response through the comprehensive adjustment of proportional (P), integral (I), and derivative (D) parameters. It is typically represented as follows:

[0089]

[0090] In the formula: u(t) is the control output (such as PWM duty cycle); e(t) is the error (the difference between the set value and the actual value); K p K is the proportionality coefficient. iK is the integral coefficient; d is the differential coefficient.

[0091] (2) The generated PWM modulation signal is transmitted to the power drive unit. The power drive unit controls the on / off state of the power supply circuit of the electromagnetic coil 5 according to the PWM duty cycle, thereby adjusting the input power of the electromagnetic coil 5. A Hall current sensor is installed in the power supply circuit of the electromagnetic coil 5 to collect the current signal of the coil in real time, calculate the actual current and equivalent power value, and feed it back to the PID controller. The equivalent power value is calculated using the equivalent resistance model. The equivalent resistance model is as follows:

[0092]

[0093] In the formula: The equivalent resistance of the coil (obtained through calibration), in Ω. The effective current value, in A, is calculated for the Hall sensor.

[0094] (3) A watertight cable supplies power to the electromagnetic coil 5. The electromagnetic coil 5 generates an alternating magnetic field, and the inner cylinder 2 is induced to generate eddy currents in the alternating magnetic field. The eddy currents are converted into Joule heat under the action of the resistance loss of the inner cylinder 2, thereby heating the target structure.

[0095] Step 4: Repeat steps 1, 2, and 3 to continuously monitor the wax deposits in the wellbore. The system identifies the wax deposits and controls the heating system to melt them, thus achieving closed-loop monitoring and cleaning of the wax deposits in the tubing.

[0096] The design concept of this invention is as follows:

[0097] (1) In the detection system, the ultrasonic transceiver 3 sends detection ultrasonic waves and receives ultrasonic echo signals at preset time intervals, and transmits the acquired multiple echo signals to the signal receiving module 7 in the judgment system for processing.

[0098] (2) The signal receiving module 7 in the system amplifies, filters, and reduces noise from multiple echo signals, and transmits the processed signals to the signal processing module 8. The signal processing module 8 performs digital filtering and envelope extraction on the signals, and transmits the processed signals to the information comparison module 9. The information comparison module 9 performs multi-dimensional feature extraction based on the envelope signal, normalizes and differentially processes the extracted feature data, generates a standardized vector, and inputs it into the support vector machine model. It performs quantitative evaluation based on the standard sample of wax deposition degree and transmits the evaluation result to the control module 10. The control module 10 calculates the corresponding target heating temperature based on the function model between the wax deposition degree and the target heating temperature, and generates a heating signal that is transmitted to the heating system.

[0099] Determine the closed-loop monitoring of the system, such as Figure 4As shown, signal receiving module 7 receives multiple ultrasonic echo signals, performs programmable gain amplification on the signals to improve the system signal-to-noise ratio (SNR), and applies bandpass filtering and wavelet denoising to suppress low-frequency drift and high-frequency interference, remove random noise, and preserve the transient characteristics of the echoes, thereby improving the signal-to-noise ratio and the stability of the features. The processed signals are then transmitted to signal processing module 8, which performs fourth-order Butterworth digital bandpass filtering and Hilbert transform on the signals, converting the high-frequency oscillation signals into low-frequency envelope signals characterizing the changes in echo energy, providing a stable data foundation for subsequent feature extraction. The signal is transmitted to the information comparison module 9, where multi-dimensional feature extraction is performed based on the envelope signal, including time-domain statistical features, energy features, and attenuation features. The extracted feature data is normalized and differentially processed to generate a standardized feature vector, which is then input into the support vector machine model. The support vector machine model quantitatively evaluates the degree of waxing based on a standard sample of waxing degree and transmits the result to the control module 10. The control module 10 calculates the target heating temperature based on the evaluation result, generates a heating signal based on the target heating temperature, and transmits it to the heating system to perform the heating operation. The ultrasonic echo signal is fed back at a preset time interval to form a closed-loop monitoring and control.

[0100] (3) After receiving the heating signal, the digital controller in the heating system generates a target control power input to the PID controller based on the heating signal. The PID controller calculates the error between the target control power and the real-time feedback power, outputs the control quantity, and generates a corresponding PWM modulation signal, which is then transmitted to the power drive unit. The drive unit controls the on / off state of the power supply circuit of the electromagnetic coil 5 according to the PWM duty cycle. The Hall current sensor collects the current signal of the coil in real time, calculates the actual current and equivalent power value, and feeds it back to the PID controller.

[0101] In the heating system, the digital controller generates a target control power input based on the heating signal and sends it to the PID controller. The PID controller calculates the error between the target control power and the real-time feedback power, outputs a control quantity, and generates a corresponding PWM modulation signal. This PWM modulation signal is transmitted to the power drive unit, which controls the on / off state of the power supply circuit of the electromagnetic coil 5 according to the PWM duty cycle, thus adjusting the input power of the electromagnetic coil 5. A Hall current sensor is installed in the power supply circuit of the electromagnetic coil 5 to collect the coil's current signal in real time, calculate the actual current and equivalent power value, and feeds it back to the PID controller, thereby achieving closed-loop control.

[0102] This invention utilizes a technology combining ultrasonic timed detection and electromagnetic dynamic heating to prevent reduced production caused by wax deposition in the wellbore. The method uses ultrasonic signal detection combined with a judgment system to quantitatively assess the degree of wax buildup in the tubing, and then removes and dissolves it through a heating system. This not only allows for timed detection of wax deposits in the wellbore, preventing disruption to normal production, but also solves problems such as tool jamming and wear caused by wax buildup, extending tool life. Especially in production wells where wax buildup has occurred or is at high risk, this technology can dynamically adjust heating power and time based on the wax buildup level identification results, achieving intelligent prevention and control of wax buildup in the wellbore.

[0103] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A downhole heating anti-wax sub based on ultrasonic detection, characterized in that: The downhole heating and anti-wax sub is installed in the wax-accumulating area of ​​the tubing. It includes an outer shell that can be connected to the tubing, an inner cylinder inside the outer shell, a heating system between the outer shell and the inner cylinder, a flow channel in the middle of the inner cylinder that communicates with the tubing, and an ultrasonic detection system on the inner wall of the inner cylinder. The ultrasonic detection system is connected to a judgment system, which is connected to the heating system. The judgment system is used to receive and process the echo signal from the ultrasonic detection system, complete information identification and analysis, and control the heating system based on the analysis results.

2. The downhole heating anti-wax sub based on ultrasonic detection according to claim 1, characterized in that: The ultrasonic detection system includes multiple ultrasonic transceivers, which are divided into one or more groups and are located within the ultrasonic sensing layer. The multiple groups of ultrasonic transceivers are arranged at intervals along the length of the inner cylinder. The ultrasonic sensing layer is located inside the inner cylinder, and the multiple ultrasonic transceivers in the same group are arranged in a circumferential array along the inner wall of the inner cylinder.

3. The downhole heating anti-wax sub based on ultrasonic detection according to claim 2, characterized in that: The judgment system includes a signal receiving module, a signal processing module, an information comparison module, and a control module. The signal receiving module receives echo signals from multiple ultrasonic transceivers, amplifies, filters, and reduces noise in the ultrasonic echo signals, and transmits the signals to the signal processing module. The signal processing module performs digital filtering and envelope sampling on the signals and transmits the processed information to the information comparison module. The information comparison module extracts features from the envelope signals, uses a support vector machine model to identify the wax deposition state based on the feature information, and transmits the identification result to the control module. The control module analyzes the identification result and transmits an execution signal to the heating system.

4. The downhole heating anti-wax sub based on ultrasonic detection according to claim 3, characterized in that: The heating system is an electromagnetic coil that heats the inner cylinder and raises the temperature of the inner wall of the well. The electromagnetic coil is controlled by a judgment system and is wound along the length of the inner cylinder.

5. The downhole heating anti-wax sub based on ultrasonic detection according to claim 4, characterized in that: The inner cylinder is wrapped with an insulating layer, and the inner cylinder is made of metal.

6. A downhole heating method for preventing wax deposition based on ultrasonic detection, characterized in that, Includes the following steps: Step 1: Assemble the downhole heating and anti-wax sub as described in any one of claims 3-5, connect both ends of the downhole heating and anti-wax sub to the tubing, and place the downhole heating and anti-wax sub in the wax-deposited area of ​​the tubing; Step 2: The ultrasonic testing system sends ultrasonic waves at specified time intervals and transmits the received corresponding ultrasonic echoes to the judgment system. The judgment system then generates a heating signal based on the echo signal from the ultrasonic testing system. Step 3: The digital controller of the heating system generates a target control power input to the PID controller based on the heating signal. The PID controller performs calculations based on the error between the target control power and the real-time feedback power, outputs the control quantity, and generates the corresponding PWM modulation signal. The generated PWM modulation signal is transmitted to the power drive unit. The power drive unit controls the on / off state of the heating system based on the PWM duty cycle and adjusts the input power of the heating system. Step 4: Repeat steps 1, 2, and 3 to continuously monitor the wax deposits in the wellbore. The system identifies the wax deposits and controls the heating system to melt them, thus achieving closed-loop monitoring and cleaning of the wax deposits in the tubing.

7. The downhole heating wax prevention method based on ultrasonic detection according to claim 6, characterized in that: The signal receiving module of the judgment system includes an ultrasonic transducer, a processor and a memory. The ultrasonic transducer is used to receive ultrasonic echo signals, and the processor is used to call and execute the signal processing program stored in the memory to perform gain adjustment, bandpass filtering and noise reduction processing on the echo signals in sequence. The signal processing module is used to perform digital bandpass filtering and envelope extraction on the processed signal in sequence, and output the envelope signal. The output of the signal processing module is connected to the input of the information comparison module. The information comparison module is used to extract the envelope signal, obtain the echo energy change information, and perform multi-dimensional feature extraction based on the envelope signal. The extracted feature data is normalized and differentially processed to generate a standardized feature vector, which is then input into the support vector machine model. The support vector machine model judges the degree of wax deposition. The support vector machine model evaluates the degree of wax deposition in the tubing based on the standard feature vector of the degree of wax deposition and transmits the evaluation result to the control module.

8. The downhole heating wax prevention method based on ultrasonic detection according to claim 7, characterized in that: The multi-dimensional features include time-domain statistical features, energy features, attenuation features, and frequency-domain features. The time-domain statistical features include echo propagation time, peak arrival time, and echo delay time. The energy features include total energy and segmented energy ratio. The attenuation features include echo amplitude attenuation coefficient and multiple echo attenuation rate. The frequency-domain features include spectral centroid, dominant frequency, bandwidth, and high-frequency energy proportion.

9. The downhole heating wax prevention method based on ultrasonic detection according to claim 8, characterized in that: The methods for judging the degree of wax buildup in oil pipes using the support vector machine model include the propagation time method, the echo amplitude attenuation method, the acoustic impedance reflection method, the spectrum change method, and a comprehensive judgment model.

10. A downhole heating method for preventing wax deposition based on ultrasonic detection according to claim 9, characterized in that: The support vector machine model compares the real-time monitoring results with data under the wax deposition standard and outputs the wax deposition degree judgment result of the tubing to the control module; the control module calculates the corresponding target heating temperature T based on the evaluation result and the function model between the wax deposition degree and the target heating temperature. The function model is as follows: In the formula: Normal wellbore temperature, ℃; Maximum safe heating temperature, ℃; The degree of wax buildup is calculated using a comprehensive judgment model; The wax deposition sensitivity coefficient is determined experimentally.

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