Intelligent drill string duplex information transmission system and method based on ADSL communication

Abstract

This invention relates to the field of drilling communication technology, specifically to an intelligent drill string duplex information transmission system and method based on ADSL communication. It includes: a channel modeling module identifying deep fading frequency bands based on drill string joint parameters; a resource allocation module establishing a spectrum mapping table from deep fading subcarriers to available subcarriers and determining a bit allocation scheme; a rotation compensation module establishing a phase offset prediction model; a data transmission module performing duplex transmission based on the spectrum mapping table and phase pre-compensation; and an adaptive update module periodically updating parameters and switching operating modes through predictive failure detection. This invention solves the problem of deep fading and time-varying rotation coupling in drill string segmented channels through a joint reflection channel modeling and rotation prediction compensation mechanism, thereby improving transmission reliability and spectral efficiency.

Description

Technical Field

[0001] This invention relates to the field of drilling communication technology, specifically to an intelligent drill string duplex information transmission system and method based on ADSL communication. Background Technology

[0002] The demand for high-speed downhole data transmission in measurement while drilling (MSW) technology is becoming increasingly urgent. The drill string, as the physical channel for transmitting downhole data, has become a key technical approach. However, the multi-joint structure and continuous rotation characteristics of the drill string channel pose serious challenges to the communication system.

[0003] Existing drill string communication technologies face two major challenges: First, the segmented channel formed by multiple joints in the drill string generates frequency-selective deep fading. Traditional ADSL systems only employ subcarrier shutdown strategies to address this fading, resulting in significant waste of spectrum resources. Second, the continuous rotation of the drill string causes time-varying channel parameters. Existing solutions track these changes by increasing training overhead, but real-time detection increases the system burden and is difficult to adapt to high-speed rotation conditions. Current technologies lack a joint processing mechanism for channel modeling and rotational coupling effects that addresses the reflection characteristics of drill string joints. Summary of the Invention

[0004] This invention provides an intelligent drill string duplex information transmission system and method based on ADSL communication, which solves the problems of transmission reliability and spectral efficiency caused by deep fading and rotational time-varying coupling in multi-joint segmented channels of drill strings.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses an intelligent drill string duplex information transmission system based on ADSL communication, comprising:

[0007] The channel modeling module is used to obtain the number of drill string segments, the length of each segment, and the impedance parameters at the joint. Based on the length of each segment and the impedance parameters, it calculates the round-trip time delay of the joint reflected signal and identifies the deep fading frequency band formed by the superposition of multiple reflections at the joint.

[0008] The resource allocation module is used to measure the channel quality parameters of each ADSL subcarrier, establish a spectrum mapping table from deep fading subcarriers to available subcarriers, and determine the bit allocation scheme based on the deep fading frequency band, the spectrum mapping table, and the channel quality parameters.

[0009] The rotation compensation module is used to detect the rotation angle and rotation frequency of the drill string, calculate the channel phase offset based on the rotation angle, establish a phase offset prediction model, and determine the update cycle.

[0010] The data transmission module is used to modulate the data according to the bit allocation scheme and the spectrum mapping table, and perform phase pre-compensation according to the phase offset before transmitting the data through the drill string in a duplex manner.

[0011] An adaptive update module is used to periodically re-detect the rotation angle and update the phase offset according to the update period, re-measure the channel quality parameters and update the spectrum mapping table and bit allocation scheme.

[0012] As a preferred embodiment of the present invention, the identification of the deep fading frequency band formed by multiple reflections superimposed from the connector includes:

[0013] Calculate the distance from each joint to the signal transmission point based on the length of each section of the drill string;

[0014] The round-trip time of the signal reaching each joint and being reflected back to the sending point is calculated based on the propagation speed of electromagnetic waves in the drill string.

[0015] Calculate the phase difference of the reflected signals at different frequencies based on the round-trip time delay difference of the reflected signals from adjacent joints;

[0016] Identify phase difference as The frequencies corresponding to odd multiples of the frequency are used as notch frequencies, and deep fading bands are formed from the notch frequencies.

[0017] As a preferred embodiment of the present invention, the establishment of the spectrum mapping table from deep fading subcarriers to available subcarriers specifically includes:

[0018] Traverse all deep fading subcarriers located in the deep fading frequency band from low to high frequency;

[0019] For each deep fading subcarrier, search the spectrum for available subcarriers with channel quality parameters higher than a preset quality threshold;

[0020] Calculate the weighted value of the frequency spacing and channel quality parameters between deep fading subcarriers and available subcarriers;

[0021] The available subcarriers with the optimal weighting values ​​are selected to establish a mapping relationship with the deep fading subcarriers. The frequencies before mapping, after mapping, and the frequency difference between the two are recorded as the frequency shift carrier frequencies, forming a spectrum mapping table.

[0022] As a preferred embodiment of the present invention, the step of determining the bit allocation scheme based on the deep fading frequency band, the spectrum mapping table, and the channel quality parameters specifically includes:

[0023] For available subcarriers that are not mapped by deep fading subcarriers, the modulation order is directly assigned according to the channel quality parameters;

[0024] For available subcarriers mapped by deep fading subcarriers, the total carrying capacity is calculated based on the channel quality parameters;

[0025] The remaining capacity is obtained by subtracting the capacity occupied by the original data from the total capacity.

[0026] When the remaining carrying capacity is insufficient to carry the mapped data, the modulation order of the original data is reduced to release the carrying capacity;

[0027] The modulation order of the mapped data is determined based on the adjusted remaining carrying capacity and the priority of the mapped data, thus forming a bit allocation scheme.

[0028] As a preferred embodiment of the present invention, the resource allocation module further includes:

[0029] The proportion of subcarriers in the deep fading frequency band to the total number of ADSL subcarriers is statistically analyzed.

[0030] When the proportion of deep fading subcarriers is lower than the first threshold, the spectrum mapping table is disabled, and all subcarriers are directly allocated bits according to the channel quality parameters.

[0031] When the proportion of deep fading subcarriers is between the first threshold and the second threshold, the spectrum mapping table is activated to map the data of deep fading subcarriers to available subcarriers for transmission.

[0032] When the proportion of deep fading subcarriers exceeds the second threshold, reduce the overall ADSL transmission rate or switch to low-frequency subcarriers for communication.

[0033] The first and second thresholds are dynamically adjusted based on the drill string rotation frequency; the higher the rotation frequency, the lower the values ​​of the two thresholds.

[0034] As a preferred embodiment of the present invention, the establishment of the phase offset prediction model specifically includes:

[0035] The parasitic capacitance change is calculated based on the geometric relationship between the rotation angle and the distance from the well wall. The channel phase offset is then calculated based on the parasitic capacitance change, and a functional relationship between the phase offset and the rotation angle is established.

[0036] At the beginning of each update cycle, the actual current rotation angle is detected as the initial angle;

[0037] Based on the drill string rotation frequency, a time function is established that allows the rotation angle to change linearly with time.

[0038] Substituting the time function of the rotation angle into the functional relationship between the phase offset and the rotation angle, we obtain a prediction function for the phase offset changing over time.

[0039] At any point within the update cycle, the real-time phase offset is calculated by substituting the current time into the prediction function.

[0040] As a preferred embodiment of the present invention, the determination of the update cycle specifically includes:

[0041] Calculate the time period for one revolution of the drill string based on the rotation frequency;

[0042] The maximum allowable phase error is determined based on the cumulative phase offset.

[0043] Calculate the range of rotation angles corresponding to the maximum phase error;

[0044] The time interval corresponding to the rotation angle range is used as the update period of the prediction model.

[0045] As a preferred embodiment of the present invention, the data transmission module further includes:

[0046] The spectrum mapping table is applied for data modulation in both uplink and downlink transmissions;

[0047] Real-time monitoring of the remaining carrying capacity of available subcarriers in the uplink and downlink;

[0048] When the remaining carrying capacity of the available subcarriers in the uplink is sufficient, the data of the deep fading subcarriers in the downlink is preferentially mapped to the uplink time slots of the available subcarriers in the uplink.

[0049] When the remaining carrying capacity of the available subcarriers in the downlink is sufficient, the data of the deep fading subcarriers in the uplink is preferentially mapped to the downlink time slots of the available subcarriers in the downlink.

[0050] The priority of cross-link mapping is dynamically adjusted based on the real-time ratio of uplink to downlink traffic.

[0051] As a preferred embodiment of the present invention, the adaptive update module further includes:

[0052] At the end of each update cycle, the phase offset calculated by the prediction function is compared with the actual detected phase offset, and the prediction error is calculated.

[0053] When the prediction error exceeds a preset error threshold, it is marked as a prediction failure event;

[0054] Count the number of predicted failure events occurring within a continuously preset number of update cycles;

[0055] When the number of failures exceeds the preset failure threshold, the drill string is determined to be in a non-uniform rotation state. The update cycle is shortened and the mode is switched to direct measurement mode. In direct measurement mode, the rotation angle is actually detected each time to calculate the phase offset without using the prediction function.

[0056] Once the number of failures decreases to a normal range, the update cycle is gradually extended and the system is restored to the predictive model mode.

[0057] This invention also proposes an intelligent drill string duplex information transmission method based on ADSL communication, comprising:

[0058] Obtain the number of drill string segments, the length of each segment, and the impedance parameters at the joint. Calculate the round-trip time delay of the joint reflected signal based on the length of each segment and the impedance parameters, and identify the deep fading frequency band formed by the superposition of multiple reflections at the joint.

[0059] Measure the channel quality parameters of each ADSL subcarrier, establish a spectrum mapping table from deep fading subcarriers to available subcarriers, and determine the bit allocation scheme based on the deep fading frequency band, spectrum mapping table, and channel quality parameters;

[0060] The rotation angle and frequency of the drill string are detected, the channel phase offset is calculated based on the rotation angle, a phase offset prediction model is established, and the update period is determined.

[0061] The data is modulated according to the bit allocation scheme and the spectrum mapping table, and after phase pre-compensation based on the phase offset, full-duplex data transmission is performed through the drill string.

[0062] According to the update cycle, the rotation angle is periodically re-detected and the phase offset is updated, the channel quality parameters are re-measured and the spectrum mapping table and bit allocation scheme are updated.

[0063] The beneficial effects of this invention are:

[0064] 1. This invention identifies deep fading frequency bands by calculating the phase difference through the round-trip time difference of the joint reflection, and moves the deep fading subcarrier data to the available subcarriers for transmission by combining the spectrum mapping mechanism. Compared with the traditional ADSL system's method of shutting down fading subcarriers, this improves spectrum utilization. Furthermore, it dynamically adjusts the transmission strategy according to the proportion of deep fading and the rotation frequency to adapt to the complex scenario of multi-joint segmented channels and rotation conditions coupled in drill string.

[0065] 2. This invention establishes a phase offset prediction function based on the geometric relationship between rotation angle and parasitic capacitance. It achieves adaptive switching between prediction mode and direct measurement mode through a prediction failure detection mechanism. This reduces detection overhead during uniform rotation and improves compensation accuracy during non-uniform rotation, thus balancing the real-time performance and accuracy of time-varying channel compensation during drill string rotation.

[0066] 3. This invention proposes a cross-link resource dynamic scheduling mechanism, which maps the deep fading subcarrier data of one link to the idle subcarrier of the opposite link for transmission based on the real-time ratio of uplink and downlink traffic, thereby breaking through the resource limitation of spectrum mapping within a single link and improving the overall throughput by utilizing the uplink and downlink resource asymmetry of the duplex system. Attached Figure Description

[0067] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0068] Figure 1 This is a schematic diagram of the structure of an intelligent drill string duplex information transmission system based on ADSL communication according to the present invention;

[0069] Figure 2 This is a flowchart illustrating an intelligent drill string duplex information transmission method based on ADSL communication according to the present invention. Detailed Implementation

[0070] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0071] Example 1: As Figure 1 As shown, the present invention discloses an intelligent drill string duplex information transmission system based on ADSL communication, comprising:

[0072] The channel modeling module is used to obtain the number of drill string segments, the length of each segment, and the impedance parameters at the joint. Based on the length of each segment and the impedance parameters, it calculates the round-trip time delay of the joint reflected signal and identifies the deep fading frequency band formed by the superposition of multiple reflections at the joint.

[0073] Furthermore, the identification of the deep fading frequency band formed by multiple reflections superimposed from the connector includes:

[0074] Calculate the distance from each joint to the signal transmission point based on the length of each section of the drill string;

[0075] The round-trip time of the signal reaching each joint and being reflected back to the sending point is calculated based on the propagation speed of electromagnetic waves in the drill string.

[0076] Calculate the phase difference of the reflected signals at different frequencies based on the round-trip time delay difference of the reflected signals from adjacent joints;

[0077] Identify phase difference as The frequencies corresponding to odd multiples of the frequency are used as notch frequencies, and deep fading bands are formed from the notch frequencies.

[0078] Specifically, first, obtain the basic parameters of the drill string, including the number of drill string segments. Length of each section of the drill string And the impedance parameters at each connector. Impedance parameters include the characteristic impedance at the connector. Characteristic impedance of drill string body These parameters can be obtained through actual measurement using an impedance meter or a vector network analyzer.

[0079] Calculate the distance from each joint to the signal transmission point based on the length of each drill string section. The distance from each connector to the sending point is:

[0080] ;

[0081] Based on the propagation speed of electromagnetic waves in the drill string Calculate the round-trip time delay of the signal reaching each connector and being reflected back to the sending point. Also calculate the propagation speed of the electromagnetic wave in the drill string. The relative permittivity of the drill string material It is determined that, for steel drill strings, the propagation speed is approximately... . No. The round-trip time delay for each connector is:

[0082] ;

[0083] It should be noted that due to impedance discontinuities at the joints of the drill string, the signal will be partially reflected at the joints. The reflected signals from adjacent joints will superimpose during transmission, and deep fading will occur when the phase difference meets certain conditions.

[0084] Based on the round-trip time delay difference of the reflected signals from adjacent joints Calculate different frequencies Phase difference of the reflected signal below:

[0085]

[0086] Identify phase difference as The frequency corresponding to an odd multiple of the frequency is taken as the notch frequency. That is, when At that time, among them If the integer is non-negative, the reflected signals from adjacent connectors are out of phase, resulting in destructive interference and deep fading. The formula for calculating the notch filter frequency is:

[0087] ;

[0088] Since the drill string contains multiple joints, the reflected signals from these joints will generate multiple notch frequency ranges. By combining the notch frequencies of all joint pairs, the frequency bands in the channel frequency response whose attenuation exceeds a preset attenuation threshold (usually set to 20dB) are identified as deep fading bands.

[0089] Through the channel modeling process described above, the frequency-selective fading characteristics of the drill string channel can be accurately predicted, providing a basis for subsequent resource allocation.

[0090] The resource allocation module is used to measure the channel quality parameters of each ADSL subcarrier, establish a spectrum mapping table from deep fading subcarriers to available subcarriers, and determine the bit allocation scheme based on the deep fading frequency band, the spectrum mapping table, and the channel quality parameters.

[0091] Furthermore, the establishment of the spectrum mapping table from deep fading subcarriers to available subcarriers specifically includes:

[0092] Traverse all deep fading subcarriers located in the deep fading frequency band from low to high frequency;

[0093] For each deep fading subcarrier, search the spectrum for available subcarriers with channel quality parameters higher than a preset quality threshold;

[0094] Calculate the weighted value of the frequency spacing and channel quality parameters between deep fading subcarriers and available subcarriers;

[0095] The available subcarriers with the optimal weighting values ​​are selected to establish a mapping relationship with the deep fading subcarriers. The frequencies before mapping, after mapping, and the frequency difference between the two are recorded as the frequency shift carrier frequencies, forming a spectrum mapping table.

[0096] Specifically, firstly, the channel quality parameters of each ADSL subcarrier are measured. These parameters include the signal-to-noise ratio (SNR) and channel gain (H(f)). The measurement process employs the standard ADSL channel estimation method: the transmitter sends a known training sequence on each subcarrier, and the receiver demodulates the received signal in the frequency domain using a Fast Fourier Transform (FFT). This signal is then compared with the known training sequence to calculate the channel gain (H(f)) and SNR. ADSL uses Discrete Multitone Modulation (DMT), dividing the spectrum into multiple subcarriers.

[0097] It should be noted that this invention establishes a spectrum mapping mechanism from deep fading subcarriers to usable subcarriers, which moves the data of subcarriers affected by deep fading to subcarriers with good channel quality for transmission.

[0098] The algorithm iterates through all deep fading subcarriers located within the deep fading frequency band, from lowest to highest frequency. A deep fading subcarrier is defined as one with a signal-to-noise ratio below a preset threshold. The subcarrier, the threshold is set according to the system bit error rate requirements.

[0099] For the A deep-fading subcarrier is used to search the spectrum for channel quality parameters that are higher than a preset quality threshold. Available subcarriers. Quality threshold. Determined based on the target bit error rate requirement, for the target bit error rate to Application scenarios, The corresponding signal-to-noise ratio threshold is preferably 15-20dB.

[0100] Calculate the first The deep fading subcarrier and the first Weighted value among candidate available subcarriers:

[0101] ;

[0102] in and These are the frequencies of the deep fading subcarriers and the available subcarriers, respectively. The signal-to-noise ratio of the available subcarriers. and These are the weighting coefficients. To reflect the influence of frequency spacing, the preferred value range is 0.01-0.1; The weight reflecting channel quality is preferably set between 0.5 and 2.0, with higher values ​​indicating higher reliability requirements. The larger the value, the greater the complexity of frequency shifting. The reciprocal of the signal-to-noise ratio (SNR) reflects the carrying capacity of available subcarriers.

[0103] Establish a mapping relationship between the available subcarrier with the smallest weighted value and the deep fading subcarrier:

[0104] ;

[0105] Record frequency before mapping Mapped frequency and the frequency difference between the two As a frequency shifter, a carrier frequency is formed to create a spectrum mapping table.

[0106] It should be noted that the spectrum mapping is implemented as follows: the transmitting end modulates the data originally allocated to the deep fading subcarriers onto the mapped available subcarriers according to the spectrum mapping table; the receiving end demodulates the data from the corresponding available subcarriers according to the spectrum mapping table. This process, within the ADSL DMT modulation framework, is achieved by adjusting the data placement position of each subcarrier during the inverse Fourier transform (IFFT), without requiring additional analog frequency shifting circuitry.

[0107] Furthermore, the step of determining the bit allocation scheme based on the deep fading frequency band, the spectrum mapping table, and channel quality parameters specifically includes:

[0108] For available subcarriers that are not mapped by deep fading subcarriers, the modulation order is directly assigned according to the channel quality parameters;

[0109] For available subcarriers mapped by deep fading subcarriers, the total carrying capacity is calculated based on the channel quality parameters;

[0110] The remaining capacity is obtained by subtracting the capacity occupied by the original data from the total capacity.

[0111] When the remaining carrying capacity is insufficient to carry the mapped data, the modulation order of the original data is reduced to release the carrying capacity;

[0112] The modulation order of the mapped data is determined based on the adjusted remaining carrying capacity and the priority of the mapped data, thus forming a bit allocation scheme.

[0113] Specifically, the bit allocation scheme for each subcarrier is determined based on the deep fading frequency band, the spectrum mapping table, and the channel quality parameters.

[0114] For available subcarriers not mapped by deep-fading subcarriers, the modulation order is directly assigned based on channel quality parameters. Using a water-filling algorithm, the modulation order is... The number of bits for each subcarrier is:

[0115] ;

[0116] in The signal-to-noise ratio gap is related to the target bit error rate and the coding scheme.

[0117] For available subcarriers mapped by deeply fading subcarriers, both the original data and the mapped data need to be carried simultaneously. The total carrying capacity is calculated based on channel quality parameters.

[0118] ;

[0119] in This refers to the subcarrier bandwidth.

[0120] Subtract the capacity occupied by the original data from the total capacity. The remaining load-bearing capacity is obtained as follows:

[0121] ;

[0122] The carrying capacity required for the mapped data The amount of data originally on the deep-fading subcarrier and the target modulation scheme are determined. When the remaining carrying capacity is insufficient to carry the mapped data, i.e. This involves reducing the modulation order of the original data to free up carrying capacity. The amount of modulation order reduction is:

[0123] ;

[0124] The modulation order of the mapped data is determined based on the adjusted remaining carrying capacity and the priority of the mapped data, forming a complete bit allocation scheme.

[0125] Furthermore, the resource allocation module also includes:

[0126] The proportion of subcarriers in the deep fading frequency band to the total number of ADSL subcarriers is statistically analyzed.

[0127] When the proportion of deep fading subcarriers is lower than the first threshold, the spectrum mapping table is disabled, and all subcarriers are directly allocated bits according to the channel quality parameters.

[0128] When the proportion of deep fading subcarriers is between the first threshold and the second threshold, the spectrum mapping table is activated to map the data of deep fading subcarriers to available subcarriers for transmission.

[0129] When the proportion of deep fading subcarriers exceeds the second threshold, reduce the overall ADSL transmission rate or switch to low-frequency subcarriers for communication.

[0130] The first and second thresholds are dynamically adjusted based on the drill string rotation frequency; the higher the rotation frequency, the lower the values ​​of the two thresholds.

[0131] Specifically, the number of subcarriers in the deep fading frequency band is counted. Averaging the total number of ADSL subcarriers proportion Different transmission strategies are adopted based on this ratio:

[0132] when At this time, the proportion of deep fading subcarriers is low, so the spectrum mapping table is disabled, and all subcarriers are directly allocated bits according to channel quality parameters to avoid mapping overhead.

[0133] when When this happens, the spectrum mapping table is activated to map data from deeply fading subcarriers to available subcarriers for transmission, making full use of spectrum resources.

[0134] when When the proportion of deep fading subcarriers is too high, the mapping mechanism is difficult to compensate effectively. In this case, the overall transmission rate of ADSL should be reduced or the communication should be switched to low-frequency subcarriers.

[0135] It should be noted that drill string rotation alters channel characteristics and affects deep fading distribution. This is based on the drill string rotation frequency. Dynamically adjust threshold and :

[0136] ;

[0137] ;

[0138] in and This is the baseline threshold under static conditions. The preferred value is 0.15-0.20. The preferred value is 0.40-0.50, which means that mapping is disabled when the deep fading ratio is below 15%-20%, and the speed is reduced or the frequency band is switched when it is above 40%-50%. and The attenuation coefficient reflects the degree of influence of the rotation frequency on the threshold. It is determined through experimental calibration or simulation optimization based on drill string structure parameters and wellbore conditions. Under conditions with higher rotation frequencies, to ensure system stability, and The larger the value, the faster the threshold decreases.

[0139] The rotation compensation module is used to detect the rotation angle and rotation frequency of the drill string, calculate the channel phase offset based on the rotation angle, establish a phase offset prediction model, and determine the update cycle.

[0140] Furthermore, the establishment of the phase offset prediction model specifically includes:

[0141] The parasitic capacitance change is calculated based on the geometric relationship between the rotation angle and the distance from the well wall. The channel phase offset is then calculated based on the parasitic capacitance change, and a functional relationship between the phase offset and the rotation angle is established.

[0142] At the beginning of each update cycle, the actual current rotation angle is detected as the initial angle;

[0143] Based on the drill string rotation frequency, a time function is established that allows the rotation angle to change linearly with time.

[0144] Substituting the time function of the rotation angle into the functional relationship between the phase offset and the rotation angle, we obtain a prediction function for the phase offset changing over time.

[0145] At any point within the update cycle, the real-time phase offset is calculated by substituting the current time into the prediction function.

[0146] Specifically, a gyroscope or rotary encoder is used to detect the rotation angle of the drill string. and rotation frequency The sensor is fixedly mounted on the rotating part at the top of the drill string. It transmits the rotation angle data in real time to the surface control unit on the non-rotating part of the wellhead via a brush-type slip ring, or a non-contact angle sensor mounted on the non-rotating support at the wellhead can be used to directly measure the drill string rotation angle. The rotation angle represents the angle of rotation of the drill string relative to its initial position, and the rotation frequency represents the number of revolutions the drill string makes per second.

[0147] The rotation of the drill string causes a periodic change in the distance between the drill string outer wall and the well wall, resulting in changes in parasitic capacitance, which in turn leads to channel phase shift.

[0148] According to the rotation angle The change in parasitic capacitance is calculated based on the geometric relationship between the drill string and the wellbore. Let the outer radius of the drill string be... The well radius is The eccentricity between the drill string axis and the wellbore axis is Then the distance from the outer wall of the drill string to the well wall is:

[0149] ;

[0150] Parasitic capacitance is inversely proportional to distance, and the change in parasitic capacitance is:

[0151] ;

[0152] in The initial parasitic capacitance, Initial distance. Initial parasitic capacitance. This can be measured using an impedance analyzer while the drill string is stationary; for typical... Drill string in In the well, It is approximately 80-150 pF / m, with the specific value depending on the dielectric constant of the drilling mud in the wellbore. Total channel capacitance. This is the cumulative parasitic capacitance along the entire length of the drill string, which is approximately 240-450 nF for a 3000-meter drill string.

[0153] The channel phase offset is calculated based on the change in parasitic capacitance. The relationship between the channel phase offset and the change in parasitic capacitance is as follows:

[0154] ;

[0155] in For signal frequency, Total channel capacitance. A functional relationship between phase offset and rotation angle is established based on the above relationships. .

[0156] It should be noted that real-time detection of rotation angle will increase system overhead. This invention establishes a phase offset prediction model and calculates the phase offset through a prediction function within the update cycle.

[0157] At the beginning of each update cycle Actual detection of the current rotation angle As the initial angle.

[0158] Based on the drill string rotation frequency Establish a time function in which the rotation angle changes linearly with time:

[0159] ;

[0160] Substituting the time function of the rotation angle into the functional relationship between the phase offset and the rotation angle... The prediction function for the phase offset as a function of time is obtained:

[0161] ;

[0162] At any time during the update cycle The real-time phase offset is calculated by substituting the current time into the prediction function. This is used for subsequent phase pre-compensation.

[0163] Furthermore, the determination of the update cycle specifically includes:

[0164] Calculate the time period for one revolution of the drill string based on the rotation frequency;

[0165] The maximum allowable phase error is determined based on the cumulative phase offset.

[0166] Calculate the range of rotation angles corresponding to the maximum phase error;

[0167] The time interval corresponding to the rotation angle range is used as the update period of the prediction model.

[0168] Specifically, the prediction model is based on the assumption of uniform rotation, which accumulates errors over time and requires periodic updates. The process for determining the update period is as follows:

[0169] According to the rotation frequency Calculate the time period for one revolution of the drill string:

[0170] ;

[0171] The maximum permissible phase error is determined based on the cumulative phase offset. The maximum phase error is set according to the phase demodulation accuracy requirements of the system, and is usually set to [value missing]. to .

[0172] Calculate the range of rotation angles corresponding to the maximum phase error. Due to the nonlinear relationship between phase offset and rotation angle, the angle range is obtained through numerical solution. :

[0173] ;

[0174] in This is the derivative of the phase offset with respect to the rotation angle.

[0175] The time interval corresponding to the rotation angle range is used as the update period of the prediction model:

[0176] ;

[0177] A shorter update cycle leads to higher prediction accuracy, but also higher detection overhead. The update cycle determined by the above method minimizes detection overhead while ensuring accuracy.

[0178] The data transmission module is used to modulate the data according to the bit allocation scheme and the spectrum mapping table, and perform phase pre-compensation according to the phase offset before transmitting the data through the drill string in a duplex manner.

[0179] Furthermore, the data transmission module also includes:

[0180] The spectrum mapping table is applied for data modulation in both uplink and downlink transmissions;

[0181] Real-time monitoring of the remaining carrying capacity of available subcarriers in the uplink and downlink;

[0182] When the remaining carrying capacity of the available subcarriers in the uplink is sufficient, the data of the deep fading subcarriers in the downlink is preferentially mapped to the uplink time slots of the available subcarriers in the uplink.

[0183] When the remaining carrying capacity of the available subcarriers in the downlink is sufficient, the data of the deep fading subcarriers in the uplink is preferentially mapped to the downlink time slots of the available subcarriers in the downlink.

[0184] The priority of cross-link mapping is dynamically adjusted based on the real-time ratio of uplink to downlink traffic.

[0185] Specifically, the data to be transmitted is modulated according to the bit allocation scheme and spectrum mapping table determined by the resource allocation module. For data on deeply fading subcarriers, it is moved to the corresponding available subcarriers for modulation according to the spectrum mapping table. Quadrature amplitude modulation (QAM) is used, and the modulation order is determined by the bit allocation scheme.

[0186] Before signal transmission, the phase offset is calculated by the rotation compensation module. Perform phase pre-compensation. For the first... Modulation symbols of each subcarrier The compensated transmission symbol is:

[0187] ;

[0188] Phase precompensation cancels out the channel phase offset caused by drill string rotation, ensuring that the receiver can correctly demodulate the signal.

[0189] The modulated and phase-compensated signal is transmitted in full-duplex mode through the drill string channel. The full-duplex transmission adopts frequency division duplex (FDD) or time division duplex (TDD) mode, with uplink and downlink data occupying different frequency bands or time slots respectively.

[0190] It should be noted that this invention proposes a cross-link resource scheduling mechanism to dynamically allocate spectrum resources between the uplink and downlink, thereby further improving resource utilization.

[0191] Spectrum mapping tables are used for data modulation in both uplink and downlink transmissions. Each uplink and downlink maintains its own spectrum mapping table, which records the mapping relationship between deep fading subcarriers and available subcarriers for each link.

[0192] Real-time monitoring of the remaining carrying capacity of available subcarriers in the uplink and downlink. The remaining carrying capacity of the available subcarriers is:

[0193] ;

[0194] in For total load capacity, This represents the load-bearing capacity already in use.

[0195] When the remaining capacity of the available subcarriers in the uplink is sufficient, i.e. The system prioritizes mapping deep-fading subcarrier data in the downlink to uplink time slots on available uplink subcarriers. In this case, the downlink deep-fading subcarrier data borrows uplink spectrum resources for transmission, avoiding the occupation of available downlink subcarriers.

[0196] When the remaining capacity of the available subcarriers in the downlink is sufficient, i.e. Prioritize mapping deep fading subcarrier data in the uplink to downlink slots of available subcarriers in the downlink.

[0197] Based on upstream business volume Downstream business volume The real-time ratio dynamically adjusts the priority of cross-link mapping. Define the traffic volume ratio:

[0198] ;

[0199] when When upstream traffic is busy, priority is given to upstream transmission, and downlink deep-faded data is preferentially mapped to idle upstream resources. At times, when downlink traffic is heavy, downlink transmission is prioritized, and uplink deep-faded data is mapped to idle downlink resources. Threshold The value is set according to the business type and priority requirements, and is usually between 1.5 and 2.0.

[0200] By dynamically scheduling resources across links, the asymmetry of uplink and downlink resources in the duplex system can be fully utilized to improve spectrum utilization.

[0201] An adaptive update module is used to periodically re-detect the rotation angle and update the phase offset according to the update period, re-measure the channel quality parameters and update the spectrum mapping table and bit allocation scheme.

[0202] Furthermore, the adaptive update module also includes:

[0203] At the end of each update cycle, the phase offset calculated by the prediction function is compared with the actual detected phase offset, and the prediction error is calculated.

[0204] When the prediction error exceeds a preset error threshold, it is marked as a prediction failure event;

[0205] Count the number of predicted failure events occurring within a continuously preset number of update cycles;

[0206] When the number of failures exceeds the preset failure threshold, the drill string is determined to be in a non-uniform rotation state. The update cycle is shortened and the mode is switched to direct measurement mode. In direct measurement mode, the rotation angle is actually detected each time to calculate the phase offset without using the prediction function.

[0207] Once the number of failures decreases to a normal range, the update cycle is gradually extended and the system is restored to the predictive model mode.

[0208] Specifically, the adaptive update module updates according to the update cycle. Parameter updates are performed periodically. At the end of each update cycle, the drill string rotation angle is re-detected, and the initial angle parameters of the phase offset prediction model are updated; the channel quality parameters of each subcarrier, including signal-to-noise ratio (SNR) and channel gain, are re-measured. The spectrum mapping table and bit allocation scheme are recalculated based on the updated channel quality parameters to ensure that the system always adapts to the dynamic changes of the drill string channel.

[0209] It should be noted that during actual drilling, the drill string may encounter abnormal conditions such as non-uniform rotation, vibration, or stuck drill bit, leading to significant errors in the prediction model based on the assumption of uniform rotation. This invention introduces a predictive failure detection and mode switching mechanism to improve the system's robustness under complex operating conditions.

[0210] At the end of each update cycle Compare the phase offset calculated by the prediction function. Phase offset from actual detection Calculate the prediction error:

[0211] ;

[0212] When the prediction error exceeds the preset error threshold When this occurs, it is marked as a predicted failure event. Error threshold. Based on the system's phase demodulation tolerance setting, it is typically set to a value of [value to be filled in]. to This ensures that prediction errors do not affect the correct demodulation of the signal.

[0213] Statistical continuity Number of predicted failure events within each update cycle Parameter M is the length of the failure statistics window, set to a fixed time window. The number of update cycles contained therein, i.e. , The preferred time is 3-5 seconds to ensure coverage of multiple rotation cycles.

[0214] It should be noted that the triggering conditions for prediction failure fall into two categories: first, systematic deviations caused by unstable rotational speed, typically manifested as prediction errors exceeding the standard for multiple consecutive cycles; second, sudden errors caused by occasional vibrations or stuck drill bits, manifested as a sharp increase in error within a single cycle. Statistical analysis... The number of failures within a cycle can effectively distinguish between occasional disturbances and persistent anomalies, avoiding unnecessary mode switching caused by occasional events.

[0215] When the number of failures exceeds the preset failure threshold At that time, that is The drill string is determined to be in a non-uniform rotation state. Failure threshold. It is typically set to 50% to 70% of the statistical window length, i.e. to This balances the system's sensitivity and anti-interference capability. The system shortens its update cycle to 1 / 2 to 1 / 3 of the original cycle and switches to direct measurement mode. In direct measurement mode, the rotation angle is actually detected and the phase offset is calculated before each data transmission. The prediction function is no longer used, thus eliminating the cumulative prediction error.

[0216] When continuous The number of failures within each update cycle has decreased to a normal range, i.e. At that point, it is determined that the drill string has returned to a state of uniform rotation. Parameters To restore the decision window length, it is usually set to To avoid frequent mode switching, the system gradually extends the update cycle, adjusting it to 1.5 times the original cycle, and eventually reverting to the initial update cycle. Then switch back to prediction model mode to reduce detection overhead.

[0217] Through the aforementioned adaptive update mechanism, the system can dynamically adjust its operating mode according to the drill string rotation status and channel changes, minimizing system overhead while ensuring transmission reliability.

[0218] Example 2:

[0219] Example 2 employs the intelligent drill string duplex information transmission method based on ADSL communication of the present invention, applied to deep well drilling in an oilfield. The well depth is over 3000 meters, the drill string consists of 107 segments, each 30 meters long, and the characteristic impedance at the joints is... The characteristic impedance of the drill string body is 55Ω. The Ω is 50. The drill string rotates continuously at 60-80 rpm during drilling. The wellbore diameter is 215.9 mm, the drill string outer diameter is 127 mm, and the eccentricity is approximately 18 mm.

[0220] First, obtain the number of drill string segments, the length of each segment, and the joint impedance parameters, based on the propagation speed of electromagnetic waves in the steel drill string. Calculate the round-trip time delay of the reflected signals from each connector. Based on the time delay difference between reflected signals from adjacent connectors, the deep fading frequency bands are identified as mainly concentrated in two intervals: 1.1MHz to 1.7MHz and 3.4MHz to 4.1MHz. The ADSL system operates in the frequency band from 0.138MHz to 8.832MHz, with a total of 256 subcarriers. Of these, 82 are deep fading subcarriers, accounting for 32% of the total subcarriers. This percentage falls within the threshold range for enabling spectrum mapping; therefore, a spectrum mapping strategy is adopted.

[0221] The signal-to-noise ratio (SNR) of each subcarrier was measured, and a spectral mapping table was established to map the 82 deep-fading subcarriers to available subcarriers with good channel quality. Based on the mapping table and channel quality parameters, a bit allocation scheme was determined. Unmapped available subcarriers were assigned QAM modulation orders 2 to 8, while mapped available subcarriers had their carrying capacity released by reducing their original data modulation order.

[0222] The drill string rotation angle and frequency are detected. The parasitic capacitance change is calculated based on the geometric relationship between the rotation angle and the wellbore distance, and then the channel phase offset is calculated. A phase offset prediction function is established based on an average rotation frequency of 70 revolutions per minute, and the update period is determined to be 0.22 seconds. Data is modulated according to a bit allocation scheme and a spectrum mapping table. Before transmission, phase pre-compensation is performed based on the predicted phase offset, and full-duplex data transmission is achieved through the drill string.

[0223] During the normal drilling phase, the rotation angle is re-detected and the prediction model is updated every 0.22 seconds, and the prediction error remains within a certain range. Within this range, the system's detection frequency is approximately 4.5 times per second. When drilling encounters complex formations, the drill string rotation speed fluctuates to 50-85 revolutions per minute, and the prediction error exceeds [a certain threshold]. If the number of failures within a continuous monitoring window exceeds a set threshold, it is determined to be a non-uniform rotation state. The update cycle is shortened to 0.08 seconds, the detection frequency is increased to 12.5 times / second, and it switches to direct measurement mode, directly detecting the rotation angle and calculating the phase offset before each transmission. After the drill string speed returns to stability, the update cycle is gradually extended and it reverts to predictive mode.

[0224] In an asymmetric service scenario where downlink transmits downhole geological parameters and uplink transmits control commands, the uplink / downlink traffic ratio n=0.4, indicating busy downlink traffic. Since sufficient remaining capacity of the available subcarriers in the downlink is detected, the data from the 16 deep-fading subcarriers in the uplink is mapped to the idle subcarriers in the downlink for transmission.

[0225] During a 48-hour drilling process, the method of this invention was compared with existing ADSL drill string communication methods. Existing methods employ a strategy of directly disabling deep-fading subcarriers and perform channel estimation by periodically sending training sequences with a transmission period of 0.05 seconds. The test results are shown in the table below:

[0226] Table 1 Comparison Test Table

[0227]

[0228] Test results show that the method of the present invention moves deep fading subcarrier data to available subcarriers for transmission through a spectrum mapping mechanism. Compared with the existing method of shutting down deep fading subcarriers, the transmission rate and spectrum efficiency are improved by about 50%. Through phase pre-compensation using a phase offset prediction model, the bit error rate is reduced by more than 60%, verifying the effectiveness of the method of the present invention under actual drilling conditions.

[0229] 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 protection scope of the present invention.

Claims

1. A smart drill string duplex information transmission system based on ADSL communication, characterized in that, include: The channel modeling module is used to obtain the number of drill string segments, the length of each segment, and the impedance parameters at the joint. Based on the length of each segment and the impedance parameters, it calculates the round-trip time delay of the joint reflected signal and identifies the deep fading frequency band formed by the superposition of multiple reflections at the joint. The resource allocation module is used to measure the channel quality parameters of each ADSL subcarrier, establish a spectrum mapping table from deep fading subcarriers to available subcarriers, and determine the bit allocation scheme based on the deep fading frequency band, the spectrum mapping table, and the channel quality parameters. The rotation compensation module is used to detect the rotation angle and rotation frequency of the drill string, calculate the channel phase offset based on the rotation angle, establish a phase offset prediction model, and determine the update cycle. The data transmission module is used to modulate the data according to the bit allocation scheme and the spectrum mapping table, and perform phase pre-compensation according to the phase offset before transmitting the data through the drill string in a duplex manner. An adaptive update module is used to periodically re-detect the rotation angle and update the phase offset according to the update period, re-measure the channel quality parameters and update the spectrum mapping table and bit allocation scheme.

2. The intelligent drill string duplex information transmission system based on ADSL communication according to claim 1, characterized in that, The identification of deep fading frequency bands formed by multiple reflections superimposed from the connector includes: Calculate the distance from each joint to the signal transmission point based on the length of each section of the drill string; The round-trip time of the signal reaching each joint and being reflected back to the sending point is calculated based on the propagation speed of electromagnetic waves in the drill string. Calculate the phase difference of the reflected signals at different frequencies based on the round-trip time delay difference of the reflected signals from adjacent joints; Identify phase difference as The frequencies corresponding to odd multiples of the frequency are used as notch frequencies, and deep fading bands are formed from the notch frequencies.

3. The intelligent drill string duplex information transmission system based on ADSL communication according to claim 1, characterized in that, The establishment of the spectrum mapping table from deep fading subcarriers to available subcarriers specifically includes: Traverse all deep fading subcarriers located in the deep fading frequency band from low to high frequency; For each deep fading subcarrier, search the spectrum for available subcarriers with channel quality parameters higher than a preset quality threshold; Calculate the weighted value of the frequency spacing and channel quality parameters between deep fading subcarriers and available subcarriers; The available subcarriers with the optimal weighting values ​​are selected to establish a mapping relationship with the deep fading subcarriers. The frequencies before mapping, after mapping, and the frequency difference between the two are recorded as the frequency shift carrier frequencies, forming a spectrum mapping table.

4. The intelligent drill string duplex information transmission system based on ADSL communication according to claim 1, characterized in that, The specific steps of determining the bit allocation scheme based on the deep fading frequency band, the spectrum mapping table, and channel quality parameters include: For available subcarriers that are not mapped by deep fading subcarriers, the modulation order is directly assigned according to the channel quality parameters; For available subcarriers mapped by deep fading subcarriers, the total carrying capacity is calculated based on the channel quality parameters; The remaining capacity is obtained by subtracting the capacity occupied by the original data from the total capacity. When the remaining carrying capacity is insufficient to carry the mapped data, the modulation order of the original data is reduced to release the carrying capacity; The modulation order of the mapped data is determined based on the adjusted remaining carrying capacity and the priority of the mapped data, thus forming a bit allocation scheme.

5. The intelligent drill string duplex information transmission system based on ADSL communication according to claim 1, characterized in that, The resource allocation module also includes: The proportion of subcarriers in the deep fading frequency band to the total number of ADSL subcarriers is calculated, and a first threshold and a second threshold are set, wherein the first threshold is less than the second threshold. When the proportion of deep fading subcarriers is lower than the first threshold, the spectrum mapping table is disabled, and all subcarriers are directly allocated bits according to the channel quality parameters. When the proportion of deep fading subcarriers is between the first threshold and the second threshold, the spectrum mapping table is activated to map the data of deep fading subcarriers to available subcarriers for transmission. When the proportion of deep fading subcarriers exceeds the second threshold, reduce the overall ADSL transmission rate or switch to low-frequency subcarriers for communication. The first and second thresholds are dynamically adjusted based on the drill string rotation frequency; the higher the rotation frequency, the lower the values ​​of the two thresholds.

6. The intelligent drill string duplex information transmission system based on ADSL communication according to claim 1, characterized in that, The establishment of the phase offset prediction model specifically includes: The parasitic capacitance change is calculated based on the geometric relationship between the rotation angle and the distance from the well wall. The channel phase offset is then calculated based on the parasitic capacitance change, and a functional relationship between the phase offset and the rotation angle is established. At the beginning of each update cycle, the actual current rotation angle is detected as the initial angle; Based on the drill string rotation frequency, a time function is established that allows the rotation angle to change linearly with time. Substituting the time function of the rotation angle into the functional relationship between the phase offset and the rotation angle, we obtain a prediction function for the phase offset changing over time. At any point within the update cycle, the real-time phase offset is calculated by substituting the current time into the prediction function.

7. The intelligent drill string duplex information transmission system based on ADSL communication according to claim 6, characterized in that, The determination of the update cycle specifically includes: Calculate the time period for one revolution of the drill string based on the rotation frequency; The maximum allowable phase error is determined based on the cumulative phase offset. Calculate the range of rotation angles corresponding to the maximum phase error; The time interval corresponding to the rotation angle range is used as the update period of the prediction model.

8. The intelligent drill string duplex information transmission system based on ADSL communication according to claim 1, characterized in that, The data transmission module further includes: The spectrum mapping table is applied for data modulation in both uplink and downlink transmissions; Real-time monitoring of the remaining carrying capacity of available subcarriers in the uplink and downlink; When the remaining carrying capacity of the available subcarriers in the uplink is sufficient, the data of the deep fading subcarriers in the downlink is preferentially mapped to the uplink time slots of the available subcarriers in the uplink. When the remaining carrying capacity of the available subcarriers in the downlink is sufficient, the data of the deep fading subcarriers in the uplink is preferentially mapped to the downlink time slots of the available subcarriers in the downlink. The priority of cross-link mapping is dynamically adjusted based on the real-time ratio of uplink to downlink traffic.

9. A smart drill string duplex information transmission system based on ADSL communication according to claim 6, characterized in that, The adaptive update module also includes: At the end of each update cycle, the phase offset calculated by the prediction function is compared with the actual detected phase offset, and the prediction error is calculated. When the prediction error exceeds a preset error threshold, it is marked as a prediction failure event; Count the number of predicted failure events occurring within a continuously preset number of update cycles; When the number of failures exceeds the preset failure threshold, the drill string is determined to be in a non-uniform rotation state. The update cycle is shortened and the mode is switched to direct measurement mode. In direct measurement mode, the rotation angle is actually detected each time to calculate the phase offset without using the prediction function. Once the number of failures decreases to a normal range, the update cycle is gradually extended and the system is restored to the phase offset prediction model mode.

10. A method for intelligent drill string duplex information transmission based on ADSL communication, characterized in that, include: Obtain the number of drill string segments, the length of each segment, and the impedance parameters at the joint. Calculate the round-trip time delay of the joint reflected signal based on the length of each segment and the impedance parameters, and identify the deep fading frequency band formed by the superposition of multiple reflections at the joint. Measure the channel quality parameters of each ADSL subcarrier, establish a spectrum mapping table from deep fading subcarriers to available subcarriers, and determine the bit allocation scheme based on the deep fading frequency band, spectrum mapping table, and channel quality parameters; The rotation angle and frequency of the drill string are detected, the channel phase offset is calculated based on the rotation angle, a phase offset prediction model is established, and the update period is determined. The data is modulated according to the bit allocation scheme and the spectrum mapping table, and after phase pre-compensation based on the phase offset, full-duplex data transmission is performed through the drill string. According to the update cycle, the rotation angle is periodically re-detected and the phase offset is updated, the channel quality parameters are re-measured and the spectrum mapping table and bit allocation scheme are updated.

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