CN113138425A - Logging-while-drilling electromagnetic wave data acquisition method and device - Google Patents
Logging-while-drilling electromagnetic wave data acquisition method and device Download PDFInfo
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Abstract
The invention discloses a logging-while-drilling electromagnetic wave data acquisition method, which comprises the following steps: performing frequency reduction processing on the electromagnetic wave feedback signal to obtain a signal to be processed containing the phase and amplitude of the feedback signal; continuously sampling the signal to be processed by utilizing a first sampling time interval; and calculating phase difference and amplitude ratio information corresponding to the feedback signal in each calculation period in real time according to k sampling point data in the calculation period of the signal to be processed, wherein actual time corresponding to a first number of sampling points for continuous sampling is recorded, the actual time is compared with first time, whether the value of a first timer for generating sampling time intervals needs to be adjusted is diagnosed according to the comparison result, and the first time is the product of the first number and the first sampling time intervals. The invention keeps the phase position of the sampling point on the same phase position relative to the feedback signal before mixing, so that the formation data acquired by the logging-while-drilling instrument in the long-time working process is continuously, reliably and effectively.
Description
Technical Field
The invention relates to the technical field of logging while drilling, in particular to a method and a device for acquiring electromagnetic wave data of logging while drilling.
Background
The logging-while-drilling technology is a technology for identifying formation information and boundary distance information in a real-time drilling process and providing service for evaluating hydrocarbon reservoirs and optimizing drilling tracks. In recent years, logging while drilling technology has been rapidly developed, and not only some original measurement methods have been improved, but also many new logging while drilling methods have appeared. Wherein a bit resistivity instrument (RAB) provides azimuthal gamma and real-time resistivity images; and secondly, carrying out quantitative imaging logging at multiple detection depths, such as a resistivity image generated by RAB and a density imaging image measured by a VISION system.
At present, three international petroleum technical service companies focus on the development direction of logging while drilling in the logging field to develop logging while drilling instruments. The instrument can provide parameters such as neutron porosity, lithologic density, resistivity of multiple detection depths, gamma ray, drilling azimuth, well deviation, tool face and the like, and can basically meet the requirements of stratum evaluation, geological steering and drilling engineering application. These instruments come in various combinations and specifications, depending on the needs of the user, one common combination being MWD + gamma + resistivity, which generally provides geosteering services and, in combination with porosity data of adjacent formations, may also be used for formation evaluation.
One core technology in the MWD + gamma + resistivity combined logging-while-drilling technology is to obtain the resistivity of a stratum by calculating phase difference and amplitude ratio information of electromagnetic wave signals, and because the frequency of the electromagnetic wave signals is high, generally 400KHz and 2MHz, high-frequency signals are directly sampled, and high hardware resources are occupied, so that the AD sampling rate and Flash storage are greatly challenged.
In the prior art, a frequency mixer is generally used to perform frequency reduction processing on a high-frequency electromagnetic wave signal fed back from a formation, and then an electronic processor device is used to perform multipoint sampling on each calculation period, so as to calculate phase difference and amplitude ratio information of the electromagnetic wave signal by using a plurality of sampling point data in the same calculation period, thereby obtaining resistivity information of the formation. However, when multi-point sampling is performed, due to the error of an internal device (such as a crystal oscillator) of the processor, a certain difference exists between the sampling frequency after frequency division and a theoretical value, and further deviation is generated between the actual phase of the electromagnetic wave signal fed back by the formation and the phase of the sampled signal, so that the accuracy of subsequent calculation of the phase difference and the amplitude ratio of the electromagnetic wave is influenced.
Therefore, there is a need in the art for a method for performing a phase offset compensation process on the collected data of the electromagnetic wave before calculating the phase difference and the amplitude ratio of the electromagnetic wave signal, so as to eliminate the phase offset between the sampled data and the actual feedback signal caused by the device error inside the processor.
Disclosure of Invention
In order to solve the technical problem, the invention provides a logging-while-drilling electromagnetic wave data acquisition method, which comprises the following steps: receiving an electromagnetic wave feedback signal in real time and carrying out frequency reduction processing on the signal to obtain a signal to be processed containing feedback signal phase and amplitude information; setting a first timer for generating a first sampling time interval, and continuously sampling the signal to be processed by using the first sampling time interval, wherein the period of the signal to be processed is k times of the first sampling time interval; and calculating phase difference and amplitude ratio information of the feedback signal in real time according to k sampling point data in a calculation period corresponding to the signal to be processed, wherein actual time corresponding to a first number of sampling points preset by continuous sampling is recorded, the actual time is compared with first time, whether the value of the first timer needs to be adjusted or not is diagnosed on the basis of the actual time, so that phase offset generated after the feedback signal is sampled due to self error of a processor is compensated, and the first time is the product of the first number and the first sampling time interval.
Preferably, the method further comprises: and setting a second timer for generating a transmitting antenna switching time interval, and switching different types of electromagnetic wave signals to be transmitted to the stratum at a position where a drill bit arrives at a real-time position in the drilling process according to the transmitting antenna switching time interval, wherein the transmitting antenna switching time interval is at least more than 200 times of the first sampling time interval.
Preferably, when the electromagnetic wave signal is switched, after a preset delay time is maintained, data of a preset second number of continuous sampling points are acquired and stored in a data memory.
Preferably, in comparing the actual time with the first time, and based on this, diagnosing whether the adjustment of the value of the first timer is required, the method includes: judging whether the absolute value of the difference value between the actual time and the first time exceeds a preset error threshold value, if so, continuing to judge whether the difference value is a positive number, and if so, subtracting 1 from the value of the first timer; and if the value is negative, adding 1 to the value of the first timer.
Preferably, the delay time is less than and close to half of the transmit antenna switching time interval.
Preferably, in the step of recording the actual time corresponding to the first number of sampling points of the consecutive samples, the method comprises: and setting a first timer for monitoring the actual time and controlling the first timer to start timing, controlling the first timer to be closed when the number of the sampling data continuously acquired at present reaches the first number, diagnosing whether the deviation compensation is needed, and restarting the first timer after the compensation adjustment is completed.
In another aspect, the present invention further provides a logging-while-drilling electromagnetic wave data collecting apparatus, which processes the collected electromagnetic wave signals by using the method as described above, so as to use the processed electromagnetic wave signals for phase difference and amplitude ratio calculation, the apparatus comprising: the electromagnetic wave signal receiving circuit is used for receiving an electromagnetic wave feedback signal in real time; the mixing circuit is used for carrying out frequency reduction processing on the feedback signal to obtain a signal to be processed containing feedback signal phase and amplitude information; the sampling circuit is used for continuously sampling the signal to be processed by utilizing a first sampling time interval, and the period of the signal to be processed is k times of the first sampling time interval; the central processing unit is used for setting a first timer used for generating the first sampling time interval, calculating phase difference and amplitude ratio information of the feedback signal in real time according to k sampling point data in a calculation period corresponding to the signal to be processed, recording actual time corresponding to a first number of sampling points preset by continuous sampling, comparing the actual time with the first time, and diagnosing whether the value of the first timer needs to be adjusted or not on the basis of the actual time so as to compensate phase deviation generated after the feedback signal is sampled due to self error of the processor, wherein the first time is the product of the first number and the first sampling time interval.
Preferably, the apparatus further comprises: an electromagnetic wave signal transmitting circuit for switching different types of electromagnetic wave signals to be transmitted to the formation at a real-time location of arrival of the drill bit during drilling according to a transmit antenna switching time interval generated by a second timer within the central processor, wherein the transmit antenna switching time interval is at least greater than 200 times the first sampling time interval.
Preferably, when the electromagnetic wave signal is switched by the electromagnetic wave signal transmitting circuit, the central processing unit is further configured to obtain data of a preset second number of consecutive sampling points after keeping a preset delay time, and store the data in a data storage connected to the central processing unit.
Preferably, the central processing unit is further configured to determine whether an absolute value of a difference between the actual time and the first time exceeds a preset error threshold, if so, continue to determine whether the difference is a positive number, and if so, subtract 1 from the value of the first timer; and if the value is negative, adding 1 to the value of the first timer.
Compared with the prior art, one or more embodiments in the above scheme can have the following advantages or beneficial effects:
the invention discloses a logging-while-drilling electromagnetic wave data acquisition method and device. The method and the device solve the problem of inaccurate calculation of the phase difference and the amplitude ratio of later-period electromagnetic waves caused by errors of AD sampling time intervals due to system clock errors generated by a central processing unit. The invention is provided with the first timer and the second timer which can be adjusted at any time, and utilizes the first timer to monitor the accumulated error of the AD sampling time interval in real time, so as to carry out clock (phase) deviation compensation by the first timer after the accumulated error reaches the threshold value. Therefore, the phase position of the sampling point is always kept at the same phase position relative to the electromagnetic wave feedback signal before mixing, so that the amplitude and phase information of the electromagnetic wave signal are accurately recorded, and the formation data acquired by the logging-while-drilling instrument in the long-time working process is still reliable and effective. In other words, the invention enables the logging-while-drilling instrument to keep the calculation accuracy of the equivalent electromagnetic wave phase difference and amplitude ratio in the long-time working process, thereby providing real-time and reliable resistivity data in the drilling process, and having important significance for implementing high-precision drilling.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
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The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a step diagram of a logging-while-drilling electromagnetic wave data acquisition method according to an embodiment of the present application.
FIG. 2 is a schematic diagram of an electromagnetic wave data acquisition method for logging while drilling according to an embodiment of the present disclosure.
Fig. 3 is a flowchart illustrating an implementation of the method for acquiring electromagnetic wave data during logging while drilling according to the embodiment of the present application.
Fig. 4 is a schematic structural diagram of the logging-while-drilling electromagnetic wave data acquisition device according to the embodiment of the present application.
Fig. 5 is a circuit diagram of an implementation of the electromagnetic wave data acquisition device for logging while drilling according to the embodiment of the present application.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
The logging-while-drilling technology is a technology for identifying formation information and boundary distance information in a real-time drilling process and providing service for evaluating hydrocarbon reservoirs and optimizing drilling tracks. In recent years, logging while drilling technology has been rapidly developed, and not only some original measurement methods have been improved, but also many new logging while drilling methods have appeared. Wherein a bit resistivity instrument (RAB) provides azimuthal gamma and real-time resistivity images; and secondly, carrying out quantitative imaging logging at multiple detection depths, such as a resistivity image generated by RAB and a density imaging image measured by a VISION system.
At present, a core technology in the MWD + gamma + resistivity combined logging-while-drilling technology is to calculate phase difference and amplitude ratio information of electromagnetic wave signals to obtain the resistivity of a stratum, and because the frequency of the electromagnetic wave signals is high, generally 400KHz and 2MHz, high-frequency signals are directly sampled and occupy high hardware resources, so that the AD sampling rate and Flash storage are greatly challenged.
In the prior art, a frequency mixer is generally used to perform frequency reduction processing on a high-frequency electromagnetic wave signal fed back from a formation, and then an electronic processor device is used to perform multipoint sampling on each calculation period, so as to calculate phase difference and amplitude ratio information of the electromagnetic wave signal by using a plurality of sampling point data in the same calculation period, thereby obtaining resistivity information of the formation. However, when multi-point sampling is performed, due to the error of an internal device (such as a crystal oscillator) of the processor, a certain difference exists between the sampling frequency after frequency division and a theoretical value, and further deviation is generated between the actual phase of the electromagnetic wave signal fed back by the formation and the phase of the sampled signal, so that the accuracy of subsequent calculation of the phase difference and the amplitude ratio of the electromagnetic wave is influenced.
Therefore, there is a need in the art for a method for performing a phase offset compensation process on the collected data of the electromagnetic wave before calculating the phase difference and the amplitude ratio of the electromagnetic wave signal, so as to eliminate the phase offset between the sampled data and the actual feedback signal caused by the device error inside the processor.
In order to solve the technical problem, the invention arranges a first timer for generating a first sampling time clock in a central processing unit, utilizes a first controller to monitor the time of the continuous sampling process of the electromagnetic wave feedback signal subjected to frequency reduction processing in real time, adjusts the clock count value in the first timer when the monitored real-time error exceeds a preset error threshold value, and continuously samples the electromagnetic wave feedback signal subjected to frequency reduction processing subsequently by utilizing a first sampling time interval after adjustment, thereby compensating the phase offset generated after the electromagnetic wave feedback signal is sampled due to the self error of the processor.
In addition, in order to obtain more stable and accurate sampling point data, the acquired sampling point data does not need to be stored when the current electromagnetic wave signal transmitter starts to transmit electromagnetic waves to the stratum at the real-time position reached by the drill bit in the drilling process, and a certain amount of sampling point data is acquired after the preset delay time is reached so as to ensure that more stable sampling data is acquired, thereby being beneficial to obtaining a more accurate calculation result of electromagnetic wave signal phase difference and amplitude ratio information.
Fig. 4 is a schematic structural diagram of the logging-while-drilling electromagnetic wave data acquisition device according to the embodiment of the present application. As shown in fig. 4, the apparatus of the present invention includes: the electromagnetic wave signal receiving circuit 100, the mixing circuit 200, the sampling circuit 300, the central processing unit 400, the electromagnetic wave signal transmitting circuit 500 and the waveform generator 600. The electromagnetic wave signal receiving circuit 100 is configured to receive an electromagnetic wave feedback signal in real time. The mixer circuit 200 is configured to mix the first signal with the original natural frequency and the electromagnetic wave feedback signal, and then perform a frequency reduction process to obtain a signal to be processed containing phase and amplitude information of the feedback signal. The sampling circuit 300 is configured to continuously sample the signal to be processed with a first sampling time interval. Wherein the time period of the signal to be processed is k times (k is a positive integer, preferably k is 4) the first sampling time interval. The central processor 400 is provided with a first timer T2 and a second timer T1. The first timer T2 is configured to generate a clock signal representing a first sampling interval using the first frequency division. The second timer T1 is used to generate a clock signal characterizing the transmit antenna switching time interval using the second division number. The central processing unit 400 is configured to obtain phase and amplitude data of the electromagnetic wave reflected signal corresponding to each sampling point according to k sampling points in a calculation period (time period of the signal to be processed) corresponding to the signal to be processed, and based on the phase and amplitude data, calculate phase difference and amplitude ratio information corresponding to the electromagnetic wave feedback signal in each calculation period in real time. The electromagnetic wave signal transmitting circuit 500 is used for switching the electromagnetic wave (transmitting) signals with different transmitting frequencies according to the transmitting antenna switching time interval generated by the second timer T1, so as to transmit the electromagnetic wave (transmitting) signals with corresponding frequencies to the stratum where the drill bit arrives at the real-time position in the drilling process. Wherein the transmit antenna switching time interval is at least greater than 200 times the first sampling time interval. The waveform generator 600 is used for generating the first signal of the natural original frequency under the control of the central processing unit 400 and sending the first signal to the mixer circuit 200.
Fig. 5 is a circuit diagram of an implementation of the electromagnetic wave data acquisition device for logging while drilling according to the embodiment of the present application. The apparatus of the present invention will be described in detail with reference to fig. 4 and 5. Firstly, the acquisition device comprises a plurality of signal receiving paths, each signal receiving path is connected with a central processing unit (U1)400, and the acquisition device is used for carrying out series of processing such as frequency reduction and sampling on a high-frequency electromagnetic wave feedback signal received in real time to obtain corresponding sampling point data, and transmitting the data to the central processing unit 400 for subsequent phase difference and amplitude ratio information calculation processing. In the embodiment of the invention, each path of signal receiving path has the same structure and comprises a receiving antenna, a first preprocessing circuit, a mixer, a second preprocessing circuit and an AD converter which are connected in sequence. It should be noted that, the number of signal receiving paths configured is not specifically limited in the present invention, and those skilled in the art can set the number according to actual needs. Preferably, the number of signal receiving paths configured with reference to fig. 5 is two. The following is a description of a specific structure of one of the signal receiving paths.
Further, the electromagnetic wave signal receiving circuit 100 includes receiving antennas R1, R2, and a signal preprocessing circuit. The receiving antennas R1 and R2 are used for receiving high-frequency electromagnetic wave feedback signals representing the formation resistivity in the logging-while-drilling process in real time. The first preprocessing circuit is configured to perform preprocessing including RC filtering and signal amplification on the received high-frequency electromagnetic wave feedback signal to obtain a high-frequency electromagnetic wave feedback signal that can be input to the mixer circuit 200.
The mixer circuit 200 includes a mixer U6. The mixer U6 is connected to the first preprocessing circuit, and is configured to down-convert the high-frequency electromagnetic wave feedback signal and the first signal received from the first preprocessing circuit, and output a signal to be processed at 2 kHz.
The sampling circuit 300 comprises a second pre-processing circuit and AD converters U12, U13. The second preprocessing circuit is correspondingly connected with the output end of the mixer U6 and is used for respectively and correspondingly filtering, amplifying and conditioning the signals to be processed of 2kHz through the RC filter, the signal amplifiers U8 and U9 and the signal conditioners U11 and U10, and adjusting the signals to be processed of 2kHz into the signals to be processed in the range suitable for sampling by the AD converter. The AD converters U12, U13 are configured to continuously sample the (conditioned) signal to be processed input from the signal conditioners U11, U10 under control of a first sampling interval, the sampling interval time (first sampling interval) being controlled by a first timer T2.
The electromagnetic wave signal transmitting circuit 500 includes 6 transmitting antennas (TR1, TR2, TR3, TR4, TR5, TR6), and multiplexers U14 respectively connected to the 6 antennas. Wherein, each transmitting antenna corresponds to a corresponding transmitting target. Specifically, the 6 transmitting antennas are respectively: a near antenna (TR1) with a first transmission frequency can be transmitted, a near antenna (TR2) with a second transmission frequency can be transmitted, a middle antenna (TR2) with a first transmission frequency can be transmitted, a middle antenna (TR4) with a second transmission frequency can be transmitted, a far antenna (TR5) with a first transmission frequency can be transmitted, a far antenna (TR6) with a second transmission frequency can be transmitted. The multiplexer U14 also has 6 selection channels, which are respectively connected to 6 transmit antennas. The multiplexer U14 is used for selecting the corresponding channel under the control of the switching time interval of the transmitting antenna, so as to transmit an electromagnetic wave transmitting signal meeting the current transmitting target to the stratum at the position where the drill bit reaches the real-time position in the drilling process by using the transmitting antenna of the corresponding channel. At this time, the second timer T1 is used to control the multiplexer U14 to switch the channels of different transmitting antennas according to the self-generated transmitting antenna switching time interval, so that each adjacent transmitting antenna switching time period can transmit the electromagnetic wave transmitting signals with different frequencies and different source distances. Preferably, the first frequency of the electromagnetic wave emission signal is 2 MHz; the second frequency of the electromagnetic wave transmission signal is 500 KMHz. It should be noted that, referring to fig. 5, in an actual application process, after passing through the drilling fluid and the formation, the electromagnetic wave transmitting signal is received by the receiving antenna, so as to obtain an electromagnetic wave feedback signal, but the frequency of the electromagnetic wave feedback signal is consistent with the frequency of the electromagnetic wave transmitting signal.
For example: switching a channel of TR1 to a channel of TR2, a channel of TR2 to a channel of TR3, a channel of TR3 to a channel of TR4, a channel of TR4 to a channel of TR5, a channel of TR5 to a channel of TR6, a channel of TR6 to a channel of TR1, and repeating the cycle in sequence at regular intervals of a fixed switching time interval 2T; or reverse circulation.
Further, the waveform generator 600 is used for generating a first signal which can be a natural frequency of the mixer U6 under the control of the cpu 400, and outputting the signal to the mixer U6 in the mixer circuit 200. Wherein the frequency of the first signal corresponds to the frequency of the electromagnetic wave emission signal. Preferably, when the frequency of the electromagnetic wave emission signal is 2MHz, the frequency of the first signal is 2.002 MHz; when the frequency of the electromagnetic wave emission signal is 500KHz, the frequency of the first signal is 502 KHz.
As shown in fig. 5, the central processor U1 selects an antenna TR1 (or TR2/TR3/TR4/TR5/TR6) to transmit high frequency electromagnetic wave signals, and selects a corresponding transmission frequency of 2MHz (or 500kHz) through a multiplexer U14; electromagnetic wave transmitting signals pass through the drilling fluid and the stratum and are received by receiving antennas R1 and R2; 2MHz signals received by R1 are sent to a first input end of a mixing circuit U6 after passing through a filtering and amplifying circuit U2 and a U3; the 2MHz signal received by R2 is filtered and amplified by U4 and U5, and then is sent to the second input end of the mixing circuit U6. The waveform generator U7 generates a first 2.002MHz signal and feeds the signal to two inputs of the mixer circuit U6, respectively. The mixer U6 outputs two paths of 2kHz signals, and the first path of signal receiving path sends 2kHz signals to be processed to the AD converter U12 for sampling after passing through the amplifying circuit U9 and the signal conditioning circuit U10; the second path of signal receiving path sends the signals to be processed of 2kHz to the AD converter U13 for sampling after passing through the amplifying circuit U8 and the signal conditioning circuit U11. The central processor U1 controls the waveform generator U7 to output a waveform representing a first signal having a frequency of 2.002MHz (or 502kHz) through the pins RG1, RG2, and RG3, controls the sampling interval time of the AD converter U13 through the pins RD2, RD3, and RD4, and reads data, and controls the sampling interval time of the AD converter U12 through the pins RD5, RD6, and RD 7.
The logging-while-drilling electromagnetic wave data acquisition device according to the embodiment of the present invention provides a corresponding application environment for the following logging-while-drilling electromagnetic wave data acquisition method, and after the description of the acquisition device, the logging-while-drilling electromagnetic wave data acquisition method (hereinafter referred to as "acquisition method") according to the embodiment of the present invention is described next based on the device. Fig. 1 is a step diagram of a logging-while-drilling electromagnetic wave data acquisition method according to an embodiment of the present application. FIG. 2 is a schematic diagram of an electromagnetic wave data acquisition method for logging while drilling according to an embodiment of the present disclosure. The acquisition method according to the present invention will be described with reference to fig. 1 and 2.
First, in step S110, the electromagnetic wave signal receiving circuit 100 receives the high-frequency electromagnetic wave feedback signal in real time, and performs a frequency reduction process on the currently received high-frequency electromagnetic wave feedback signal by using a mixer circuit to obtain a signal to be processed containing phase and amplitude information of the feedback signal, and then the process proceeds to step S120. Generally, the frequency of the high-frequency electromagnetic wave feedback signal is 2MHz or 500KMHz, and the frequency of the signal to be processed output by the mixing circuit after the frequency reduction processing is 2 kHz.
Step S120 the central processor 400 sets a first timer T2 for generating a first sampling time interval with which the AD converters U12, U13 within the sampling circuit 200 are controlled to successively sample the signal to be processed (at the first sampling time interval) at (2 kHz) by the AD converters, so as to proceed to step S130. Wherein the time period of the signal to be processed is k times (k is a positive integer, preferably k is 4) the first sampling time interval. In practical applications, the time period corresponding to the frequency of the signal to be processed after the down-conversion process (which may be referred to as a down-conversion time interval) is generally a calculation period of the central processing unit 400 during which the phase difference and the amplitude ratio of the electromagnetic wave signal are calculated. The first sampling time interval is a time period corresponding to the acquisition of one sampling point in one calculation period.
In order to improve the accuracy of the calculation result of the phase difference and amplitude ratio information of the electromagnetic wave signal, it is common to generate the final calculation result (phase difference and amplitude ratio information) by performing multi-point (k) sampling within one calculation period. For this reason, in the embodiment of the present invention, when data point sampling is performed, the sampling time interval is determined to be 1/k times of the down-conversion time interval, so that k pieces of sampling point data (phase and amplitude data) are collected in one calculation period. In the embodiment of the present invention, preferably, the central processor 400 calculates the phase difference and amplitude ratio information of the electromagnetic wave signal by using a four-point sampling algorithm (k is 4), so as to obtain the resistivity information of the formation. For example: the first timer T2 controls the sampling interval time dt of the AD converter using the first sampling interval it generates, so that the AD converter samples a point every dt, and sends a sampling point data (the phase and amplitude data of the electromagnetic wave reflection signal corresponding to the sampling point) to the central processor. If the frequency corresponding to the down-conversion time interval is 2kHz and k is 4, the current first sampling time interval is 125 μ s and the frequency corresponding to the first sampling time interval is 8 kHz.
Step S130, the central processing unit 400 calculates phase difference and amplitude ratio information of the electromagnetic wave feedback signal representing the formation resistivity information in each calculation period in real time by using a multipoint sampling algorithm according to k sampling point data in the calculation period corresponding to the signal to be processed.
In order to solve the above-mentioned error of the internal devices (e.g. the crystal oscillator providing the system clock) of the cpu 400 in the prior art, the sampling clock actually provided to the sampling circuit has a phase deviation from the sampling clock that should be obtained theoretically, that is, the first sampling time interval dt actually provided to the AD converter by the first timer T2 is close to 125 μ s, not exactly 125 μ s. Thus, the electromagnetic wave feedback signal received by the receiving antenna and the sampled sampling point data generate phase deviation. In this case, for the measurement while drilling technique with a very high real-time requirement, if the deviation is not corrected in time, a larger accumulated phase deviation is generated after accumulation of a plurality of calculation periods, and at this time, the accuracy of the final calculation result of the phase difference and amplitude ratio information is seriously affected, so that reliable formation resistivity data cannot be obtained. For this reason, the embodiment of the present invention utilizes the following step S140 to perform real-time monitoring and timely correction on the deviation.
Step S140, the central processing unit 400 records actual (monitoring) time corresponding to the first number (n) of continuous sampling points, compares the current actual monitoring time with the first time CNT, and diagnoses whether the value of the first timer T2 needs to be adjusted according to the comparison result, so as to compensate for phase offset generated after sampling the electromagnetic wave feedback signal due to the error of the processor itself, thereby continuously sampling the subsequent signal to be processed according to the first sampling time interval after the offset adjustment processing. The first time CNT is a product of the first number n and the first sampling time interval dt, and refers to a time required for theoretically receiving and reading n sampling points.
It should be noted that the setting of the first number is very critical, and if the setting is too large, the accuracy of the calculation result of the final electromagnetic wave signal phase difference and amplitude ratio information due to the accumulated deviation amount will be caused, and if the setting is too small, the accumulated deviation will be too small to be recognized, and it will be difficult to determine whether the clock compensation process needs to be performed on the first timer T2 (it will be difficult to determine the accurate timing of the accurate clock compensation process). Therefore, in the embodiment of the present invention, preferably, the first time for continuously sampling the first number of sampling point data is at least a time corresponding to 5-10 switching time intervals of the transmitting antenna, that is, 10T (the switching time interval of the transmitting antenna is 2T), where T is approximately equal to the time for continuously sampling 100 sampling point data. Further, n is an integer of 1000 or more and 2000 or less.
Before the step S140 is executed, the cpu 400 needs to set a first timer T3 for recording the first time CNT and control the first timer T3 to start. It should be noted that when the accuracy of the first sampling interval dt is high, the value of n may be set to be larger.
Further, a first register PR2 is disposed in the first timer T2, the register PR2 counts with the change of the system clock pulse of the central processing unit 400, and when the current count value reaches the (first) frequency division number corresponding to the first timer T2, the first register PR2 controls the first timer T2 to generate a sampling pulse to sample a point. Thus, the first timer T2 generates a clock signal having a first sampling time as a frequency under the control of the first register PR2, and generates one sampling pulse at every first sampling time interval. The value of the first timer T2 refers to the real-time count value of the system clock pulses of its internal first register PR 2.
Further, referring to fig. 2, in the step S140, during the recording of the actual time corresponding to the continuous sampling of the first number of sampling points, the central processing unit 400 further sets a first timer T3 for monitoring the actual time, and controls the start of the first timer T3 to start timing, the central processing unit 400 counts the number of sampling point data acquired in real time during the continuous sampling, when the number of the sampling point data acquired continuously reaches the first number, the central processing unit 400 controls the first timer T3 to be turned off (stop timing), diagnoses whether the offset compensation is required, and restarts the first timer T3 after the compensation adjustment is completed or it is determined that the compensation adjustment is not required. In this way, the first timer T3 is used to monitor the actual time and compensate and adjust the accumulated phase deviation in time during the process of acquiring data of n sampling points.
More specifically, in the process of comparing the actual monitoring time with the first time in step S140 and diagnosing whether the value of the first timer T2 needs to be adjusted according to the comparison result, it is further required to determine whether the absolute value of the difference between the current actual time and the first time exceeds a preset error threshold. If the difference value exceeds the preset value, whether the current difference value is a positive number or not is continuously judged, and if the difference value is the positive number, the value of the first timer T2 is reduced by 1. If the current difference is negative, 1 is added to the value of the first timer T2. It should be noted that the error threshold is preferably a time corresponding to one system clock period of the cpu 400, that is, a time corresponding to one system clock period obtained by dividing the system clock by the first division number (for example, 100 ns). In addition, if the absolute value of the current difference does not exceed the error threshold, the process returns to step S120, and the AD converter is continuously controlled to continuously sample the analog signal to be processed at 2kHz and monitor the corresponding actual time in real time, so as to calculate the phase difference and amplitude ratio information of the electromagnetic wave signal by using the multi-point sampling algorithm according to the read sampling point data in step S130.
For example, for a 2kHz (analog) signal to be processed, if the first sampling time interval dt should be 125 μ s and the setting of dt is controlled by the first register PR2 in the first timer T2, the current clock pulse count value recorded by PR2 is decremented by 1 if CNT is larger than 125n and incremented by 1 if CNT is smaller than 125 n.
Thus, the first timer T2 and the first timer T3 which can be flexibly adjusted are provided in the embodiment of the present invention, the first timer T3 is used to monitor the phase deviation which may be generated during the logging while drilling process which is performed for a long time, and after the deviation reaches the error threshold which affects the subsequent calculation result of the electromagnetic wave signal phase difference and amplitude ratio information, the phase deviation compensation processing is performed by adjusting the real-time counting value of the first register in the first timer T2, so that the problems in the prior art are solved, and the high accuracy and the data continuous reliability of the phase and amplitude values of the electromagnetic wave signal recorded by the long-time logging while drilling technology are ensured.
Furthermore, according to the requirements of the logging while drilling technology, in order to obtain more accurate and detailed resistivity information of the underground stratum, different types of electromagnetic wave transmitting signals need to be continuously transmitted to the underground stratum in the process of drilling. The types of the electromagnetic wave emission signals include: the antenna comprises a near antenna, a middle antenna, a far antenna and a far antenna, wherein the near antenna is used for transmitting a first type of electromagnetic wave transmission signal with a first transmission frequency, the near antenna is used for transmitting a second type of electromagnetic wave transmission signal with a second transmission frequency, the middle antenna is used for transmitting a third type of electromagnetic wave transmission signal with the first transmission frequency, the middle antenna is used for transmitting a fourth type of electromagnetic wave transmission signal with the second transmission frequency, the far antenna is used for transmitting a fifth type of electromagnetic wave transmission signal with a first transmission frequency, and the far antenna is used for transmitting a sixth type of electromagnetic wave transmission signal with the second transmission frequency. For this purpose, the present invention further uses step S150 to switch the electromagnetic wave signal types at each transmitting antenna switching time interval according to a preset sequence (for example, from the first type to the sixth type and back to the first type, and then sequentially circulating, or from the sixth type to the first type and back to the sixth type, and then sequentially circulating).
Step S150 the central processor 400 sets a second timer T1 for generating a transmit antenna switching time interval, and switches the electromagnetic wave signals of different types according to a preset sequence according to the transmit antenna switching time interval, so as to be transmitted to the formation where the drill bit arrives at a real-time position during the drilling process. Wherein the transmit antenna switching time interval 2T is at least greater than 200 times the first sampling time interval dt. Specifically, the central processing unit 400 is provided therein with a clock signal capable of generating a clock signal indicating the switching time interval of the transmitting antenna.
A corresponding second register is arranged in the first timer T2, the register also counts along with the change of the system clock pulse of the central processing unit 400, when the current counting value reaches the (second) frequency division number corresponding to the second timer T1, the second register controls the second timer T1 to generate a switching pulse to perform channel switching control on a multiplexer in the electromagnetic wave signal transmitting circuit 500 connected with the central processing unit 400, so that the electromagnetic wave signal transmitting circuit 500 switches from transmitting one type of electromagnetic wave transmitting signal to transmitting the other type of electromagnetic wave transmitting signal according to a preset sequence. Thus, the second timer T1 generates a clock signal having a frequency of the transmission antenna switching time under the control of the second register, and generates one switching pulse at every transmission antenna switching time interval. The value of the second timer T1 refers to the real-time count value of the system clock pulses of its internal first register PR 2.
Further, since the types of the electromagnetic wave signals transmitted by the electromagnetic wave signal transmitting circuit 500 are continuously switched during the measurement while drilling in the well, not all the received electromagnetic wave feedback signals are stable and reliable, in other words, not all the received and read sampling point data can be beneficial to calculating accurate electromagnetic wave signal phase difference and amplitude ratio information. Therefore, in the embodiment of the present invention, during the transmission of the electromagnetic wave transmission signal of the current type, the sampling point data representing the current formation resistivity state information is collected stably and reliably in step S160.
In step S160, when the electromagnetic wave emission signal is switched (from each antenna switching time), after the preset delay time is maintained, the central processing unit 400 obtains the data of a second number of consecutive sampling points, and stores the data into a data memory (e.g., a FLASH memory) connected to the central processing unit 400. Because there is no synchronous signal between the continuous sampling process and the signal transmitting process of the AD converter, if the sampled data is stored too early, the data before the current type of transmitting signal may be obtained, resulting in the phenomenon of data update being not timely; if the sampled data is stored too late, it is likely that the current type of transmission signal has switched to the next type, causing data loss, and therefore the timing of data storage is critical. Preferably, the delay time is about half of the transmit antenna switching time interval, and more particularly, is less than and close to half of the transmit antenna switching time interval. In addition, the second number is the total number of the sampling point data stored for the current type of transmission signal, and the size of the number is not particularly limited in the present invention, and is preferably the number (for example, 40) of the sampling point data acquired in a quarter time period less than the switching time interval of the transmission antenna.
For example, when storing the sampling point data, the central processing unit 400 stores 40 data points obtained by AD continuous sampling into the Flash memory after maintaining the predetermined delay time T from the time of each antenna transmission switching, that is, the sampling point data is stored in 10 calculation cycles at a time.
As shown in fig. 2, the central processor U1(S201) controls the waveform generator U7 to output a 2.002MHz (or 502kHz) first signal, simultaneously starts the second timer T1(203) by starting the second register (the register for starting the second timer constructed when the second timer is set) to operate S202, and starts the first timer T2(207) by starting the first register (the register for starting the first timer constructed when the first timer is set) to operate S206. S203, the second timer T1 switches the transmitting antenna every other transmitting antenna switching time 2T, where the transmitting antenna switching time interval 2T is much longer than the AD sampling interval time dt, and generally T is 100 × dt. S207 the first timer T2 sets the frequency division factor for the 4MHz system clock signal to 500 via the first register PR2, i.e. sets the first sampling time interval dt to 125 ±. Δ μ S, which means that dt cannot be exactly equal to 125 μ S in hardware, but only to an approximation, and the AD converter continuously samples the 2kHz signal to be processed at the first sampling time interval dt. S208, the first timer T3 counts the actual monitoring time corresponding to 1000 consecutive AD sampling points to be CNT, if CNT is greater than 125ms (125 μ S × n, n is 1000), the cpu U1 decrements the value of the first register PR2 by 1, and repeats this step until CNT is 125 ms; s209 if CNT is <125ms, the cpu U1(201) increments the value of the first register PR2 by 1, and repeats this step until CNT is 125 ms. When the sampling point data is stored in S205, the central processing unit U1 stores 40 data points continuously sampled by AD into the Flash memory, that is, the sampling point data is stored in 10 calculation cycles at a time, with a delay time T at each antenna transmission time.
Fig. 3 is a flowchart illustrating an implementation of the method for acquiring electromagnetic wave data during logging while drilling according to the embodiment of the present application. As shown in fig. 3, after the program starts, the main function is entered. Step S301 initializes the second timer T1, step S305 initializes the first timer T2, and step S316 initializes the first timer T3, i.e., the count register TMR1 is set to 0, the TMR2 is set to 0, and the TMR3 is set to 0, respectively, and at the same time, the frequency division number of the first register PR2 in the first timer T2 is set to 500, i.e., the frequency of the clock signal representing the first sampling interval after frequency division is 8kHz, i.e., the first sampling interval period is 125 μ S. The central processor 400 controls to start the second timer T1 in step S302 and controls to start the first timer T2 in step S306, i.e., sets T1CON to 1 and T2CON to 1. For the 16-bit second timer T1, the time for entering the interrupt is 16.384ms, and the timing is repeated 61 times to set the switching time interval of the transmitting antenna to 1S (step S303), and the antenna is switched at every 1S to change the type of the electromagnetic wave transmitting signal in step S304. The first sampling interval set by the first timer T2 in step S307 is about 125 μ S, the cpu 400 controls to start the first timer T3 in step S308, i.e., sets T3CON to 1, samples 1 point by the AD converter in step S309, and makes the cpu 400 obtain sample point data of the point.
In addition, step S310 calculates the number of data points for AD sampling from the time when the first timer T3 is started, and if the number of sampled data points is less than 1000 (the first number) data points, it returns to step S309AD to continue sampling data; if the 1000 th data point is sampled, the flow proceeds to step S311, where a count time value CNT is recorded by the first timer T3, and the counting is stopped. If the tolerance threshold of the CNT is 100ns, i.e., within the range of [125ms-100ns, 125ms +100ns ], the AD sampled data is considered valid, and the phase difference and amplitude ratio information calculated by the four-point sampling algorithm has high accuracy. If CNT-125ms >100ns in step S312, the method proceeds to step S313, the value of the first register PR2 of the first timer T2 is decremented by 1, and then the method proceeds to step S308. In step S314, if CNT-125ms < -100ns, the method proceeds to step 315 to add 1 to the value of the first register PR2 of the first timer T2, and then proceeds to step S308. If neither step S312 nor step S314 holds, indicating that CNT is in the range of [125ms-100ns, 125ms +100ns ], then there is no need to change the value of the first register PR2, at which point the phase and amplitude information calculated by the four-point sampling algorithm has a high degree of accuracy.
On the other hand, referring to fig. 4 and 5 again, based on the above-mentioned acquisition method, the present invention further provides a logging-while-drilling electromagnetic wave data acquisition apparatus (hereinafter referred to as "acquisition apparatus") that processes electromagnetic wave signals acquired by the above-mentioned acquisition method, so that the processed electromagnetic wave signals are used for phase difference and amplitude ratio calculation. Wherein, above-mentioned collection system includes: an electromagnetic wave signal receiving circuit 100, a mixer circuit 200, a sampling circuit 300, and a central processing unit 400. The electromagnetic wave signal receiving circuit 100 is used for receiving an electromagnetic wave feedback signal in real time. The mixer circuit 200 is configured to perform frequency reduction processing on the electromagnetic wave feedback signal to obtain a signal to be processed containing phase and amplitude information of the feedback signal. The sampling circuit 300 is configured to continuously sample the signal to be processed with a first sampling time interval. Wherein the time period of the signal to be processed is k times the first sampling time interval.
The central processor 400 is configured to set a first timer for generating a first sampling time interval, and calculate phase difference and amplitude ratio information corresponding to the electromagnetic wave feedback signal in each calculation period in real time according to k sampling point data in the calculation period corresponding to the down-conversion time interval. The central processing unit 400 is further configured to record actual time corresponding to a preset first number of sampling points for continuous sampling, compare the actual time with the first time, and diagnose whether the value of the first timer needs to be adjusted according to a comparison result, so as to compensate for phase offset generated after sampling the electromagnetic wave feedback signal due to an error of the processor. Further, the first time is a product of the first number and the first sampling time interval.
In addition, the above-mentioned collection system further comprises: an electromagnetic wave signal transmitting circuit 500. The electromagnetic wave signal transmitting circuit 500 is used to switch different types of electromagnetic wave (transmit) signals to be transmitted to the formation where the drill bit arrives at a real-time location during the while drilling process, according to the transmit antenna switching time interval generated by the second timer within the central processor 400. Wherein the transmit antenna switching time interval is at least greater than 200 times the first sampling time interval.
Further, when the type of the electromagnetic wave signal is switched by the electromagnetic wave signal transmitting circuit 500, the central processing unit 400 is further configured to obtain data of a second number of consecutive sampling points after the predetermined delay time is maintained, and store the data in the data storage connected to the central processing unit 400.
In addition, the central processing unit 400 is further configured to determine whether an absolute value of a difference between the current actual time and the first time exceeds a preset error threshold, if so, continue to determine whether the current difference is a positive number, and if so, subtract 1 from the value of the first timer; if the value is negative, the value of the first timer is increased by 1.
The invention discloses a logging-while-drilling electromagnetic wave data acquisition method and device. The method and the device solve the problem of inaccurate calculation of the phase difference and the amplitude ratio of later-period electromagnetic waves caused by errors of AD sampling time intervals due to system clock errors generated by a central processing unit. The invention is provided with a first timer and a second timer which can be adjusted at any time, and utilizes the first timer to monitor the accumulated error of the AD sampling time interval in real time, so as to carry out clock (phase) deviation compensation by the first timer after the accumulated error reaches a threshold value. Therefore, the phase position of the sampling point is always kept at the same phase position relative to the electromagnetic wave feedback signal before mixing, so that the amplitude and phase information of the electromagnetic wave signal are accurately recorded, and the formation data acquired by the logging-while-drilling instrument in the long-time working process is still reliable and effective. In other words, the invention enables the logging-while-drilling instrument to keep the calculation accuracy of the equivalent electromagnetic wave phase difference and amplitude ratio in the long-time working process, thereby providing real-time and reliable resistivity data in the drilling process, and having important significance for implementing high-precision drilling.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A logging-while-drilling electromagnetic wave data acquisition method is characterized by comprising the following steps:
receiving an electromagnetic wave feedback signal in real time and carrying out frequency reduction processing on the signal to obtain a signal to be processed containing feedback signal phase and amplitude information;
setting a first timer for generating a first sampling time interval, and continuously sampling the signal to be processed by using the first sampling time interval, wherein the period of the signal to be processed is k times of the first sampling time interval;
calculating the phase difference and amplitude ratio information of the feedback signal in real time according to k sampling point data in a calculation period corresponding to the signal to be processed, wherein,
recording the actual time corresponding to a first number of sampling points preset by continuous sampling, comparing the actual time with the first time, diagnosing whether the value of the first timer needs to be adjusted or not on the basis of the actual time, so as to compensate the phase offset generated after the feedback signal is sampled due to the self error of a processor, wherein the first time is the product of the first number and the first sampling time interval.
2. The method of claim 1, further comprising:
and setting a second timer for generating a transmitting antenna switching time interval, and switching different types of electromagnetic wave signals to be transmitted to the stratum at a position where a drill bit arrives at a real-time position in the drilling process according to the transmitting antenna switching time interval, wherein the transmitting antenna switching time interval is at least more than 200 times of the first sampling time interval.
3. The method according to claim 2, characterized in that when switching the electromagnetic wave signal, after maintaining a preset delay time, data of a preset second number of consecutive sample points are acquired and saved into a data memory.
4. The method according to any one of claims 1 to 3, wherein in the step of comparing the actual time with a first time, based on which it is diagnosed whether an adjustment of the value of the first timer is required, comprises:
judging whether the absolute value of the difference value between the actual time and the first time exceeds a preset error threshold value, if so, continuing to judge whether the difference value is a positive number, and if so, subtracting 1 from the value of the first timer; and if the value is negative, adding 1 to the value of the first timer.
5. The method of claim 3, wherein the delay time is less than and approximately half of the transmit antenna switching time interval.
6. The method according to any one of claims 1 to 5, wherein in the step of recording the actual time corresponding to the first number of sampling points of consecutive samples, comprises:
and setting a first timer for monitoring the actual time and controlling the first timer to start timing, controlling the first timer to be closed when the number of the sampling data continuously acquired at present reaches the first number, diagnosing whether the deviation compensation is needed, and restarting the first timer after the compensation adjustment is completed.
7. An electromagnetic wave data acquisition device for logging while drilling, which is characterized in that the device performs phase deviation compensation processing on the acquired electromagnetic wave signals by using the method as claimed in any one of claims 1-6, so as to use the processed electromagnetic wave signals for phase difference and amplitude ratio calculation, and the device comprises:
the electromagnetic wave signal receiving circuit is used for receiving an electromagnetic wave feedback signal in real time;
the mixing circuit is used for carrying out frequency reduction processing on the feedback signal to obtain a signal to be processed containing feedback signal phase and amplitude information;
the sampling circuit is used for continuously sampling the signal to be processed by utilizing a first sampling time interval, and the period of the signal to be processed is k times of the first sampling time interval;
a central processing unit for setting a first timer for generating the first sampling time interval and calculating the phase difference and amplitude ratio information of the feedback signal in real time according to k sampling point data in a calculation period corresponding to the signal to be processed, wherein,
recording the actual time corresponding to a first number of sampling points preset by continuous sampling, comparing the actual time with the first time, diagnosing whether the value of the first timer needs to be adjusted or not on the basis of the actual time, so as to compensate the phase offset generated after the feedback signal is sampled due to the self error of a processor, wherein the first time is the product of the first number and the first sampling time interval.
8. The apparatus of claim 7, further comprising:
an electromagnetic wave signal transmitting circuit for switching different types of electromagnetic wave signals to be transmitted to the formation at a real-time location of arrival of the drill bit during drilling according to a transmit antenna switching time interval generated by a second timer within the central processor, wherein the transmit antenna switching time interval is at least greater than 200 times the first sampling time interval.
9. The apparatus according to claim 8, characterized in that when said electromagnetic wave signal is switched by said electromagnetic wave signal transmission circuit, wherein,
and the central processing unit is also used for acquiring data of a preset second number of continuous sampling points after keeping the preset delay time, and storing the data into a data memory connected with the central processing unit.
10. The apparatus according to any one of claims 7 to 9,
the central processing unit is further configured to determine whether an absolute value of a difference between the actual time and the first time exceeds a preset error threshold, if so, continue to determine whether the difference is a positive number, and if so, subtract 1 from the value of the first timer; and if the value is negative, adding 1 to the value of the first timer.
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