A method and system for predicting gas invasion during drilling

Abstract

The present invention discloses a method and system for predicting gas invasion during drilling, including: continuously collecting audio signals in the wellbore liquid column during drilling; receiving audio signals, and performing spectrum analysis on the signals, determining the degree of sound wave attenuation in different frequency bands according to the spectrum analysis results, and judging whether gas invasion occurs underground based on the results; outputting and responding to gas invasion diagnosis results. The present invention can accurately predict early gas invasion phenomena without the need to arrange testing or monitoring instruments underground, and the implementation method is simple, safe and reliable, and the construction cost is low.

Description

Technical Field

[0001] The invention relates to the field of petroleum engineering, and in particular to a method and a system for predicting early gas invasion phenomena during a drilling process. Background Art

[0002] Gas invasion during drilling construction refers to the invasion of formation gas into the wellbore and its return to the ground with the drilling fluid. It is one of the most harmful underground complex situations. When the pressure of the drilling fluid column in the wellbore is less than the pressure of the formation fluid, the gas-bearing gas in the formation will invade the wellbore and gas invasion will occur. Since the pressure of the drilling fluid column in the wellbore decreases with the decrease of depth, the volume of the gas invading the wellbore continues to expand during the ascent process, displacing more and more drilling fluid volume, causing the bottom hole drilling fluid pressure to drop rapidly, and more formation fluid will invade the wellbore, causing the gas invasion to worsen sharply. Therefore, the earlier the gas invasion is discovered, the easier it is to deal with it. In the actual drilling operation, it is necessary to detect the gas invasion phenomenon in a timely and accurate manner so that corresponding treatment can be carried out as soon as possible to reduce the harm caused by gas invasion. Therefore, early monitoring of gas invasion is extremely important.

[0003] There are three main methods for monitoring gas intrusion currently in use: (1) Gas logging, which monitors the gas content in the drilling fluid that flows back to the ground to determine whether there is gas intrusion into the drilling fluid. However, this method cannot achieve early detection of gas intrusion. When serious gas intrusion occurs, the degree of gas intrusion is already rapidly deteriorating when gas is detected on the ground. (2) Ultrasonic detection. Ultrasonic transceiver equipment is installed in the wellbore to continuously monitor parameters such as the intensity of ultrasonic waves in the drilling fluid. The changes in ultrasonic parameters caused by gas intrusion can be used to identify gas intrusion. However, in order to achieve early detection, the ultrasonic transceiver must be installed at a deeper well depth. Therefore, it must be combined with fast signal transmission equipment, resulting in high application costs. (3) Using logging information to use Bayesian network analysis to determine gas intrusion risk. This method does not directly detect gas intrusion, and its accuracy is heavily dependent on historical data and historical risk records, which is prone to false alarms and missed alarms. Moreover, gas intrusion will only cause significant changes in logging information when it develops to a more serious level, making it difficult to achieve early gas intrusion detection. (4) Acoustic phase monitoring. Usually, when gas invasion occurs, the propagation speed of sound waves in the drilling fluid will change, which will cause the phase of the sound waves continuously monitored in the return drilling fluid at the wellhead to change. This method is subject to a lot of noise interference, especially when used in deeper wells. It is difficult to eliminate the noise interference from the severely attenuated sound wave signal, and the monitoring accuracy is limited.

[0004] To sum up, the main problems of the existing methods are: A. The accuracy of gas intrusion monitoring is not high, resulting in many false alarms and missed alarms; B. The detection of early gas intrusion phenomena is not timely enough; C. The equipment investment cost is high. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for predicting gas intrusion during drilling, comprising: step one, continuously collecting audio signals in the wellbore liquid column during drilling; step two, receiving the audio signals, and performing spectrum analysis on the audio signals, determining the degree of sound wave attenuation in different frequency bands according to the spectrum analysis results, and based on this, judging whether gas intrusion occurs in the well; step three, outputting and responding to the gas intrusion diagnosis results.

[0006] Preferably, in step one, an information acquisition module arranged in the return fluid in the drilling casing at or near the wellhead is used to collect in real time the audio signal in the sound wave transmission channel formed by the drilling pipe string and the return fluid, wherein the information acquisition module adopts a hydrophone.

[0007] Preferably, in step 2, according to the sound wave attenuation degrees of the different frequency bands, the average sound wave attenuation degree within the first frequency range and the average sound wave attenuation degree within the second frequency range are calculated respectively, and based on this, it is determined whether gas intrusion occurs underground, wherein the upper limit value of the first frequency range is lower than the lower limit value of the second frequency range.

[0008] Preferably, further, within a preset time threshold, if the average sound wave attenuation degree within the second frequency range is continuously lower than the average sound wave attenuation degree within the first frequency range, it indicates that gas invasion occurs underground.

[0009] Preferably, the average sound wave intensity of each frequency band and its corresponding average sound wave intensity derivative value are calculated according to the spectrum analysis result, and the average sound wave intensity derivative value is used to represent the degree of sound wave attenuation in the current frequency band.

[0010] On the other hand, a system for predicting gas invasion during drilling is provided. The system uses the method described above to predict early gas invasion during downhole drilling. The system includes: an information acquisition module, which is used to continuously collect audio signals in the wellbore liquid column during drilling; a gas invasion analysis module, which is used to receive the audio signal and perform spectrum analysis on the audio signal, determine the degree of sound wave attenuation in different frequency bands according to the spectrum analysis results, and based on this, judge whether gas invasion occurs in the well; a result output module, which outputs and responds to the gas invasion diagnosis result.

[0011] Preferably, further, the information acquisition module is arranged in the return fluid in the drilling casing at the wellhead or near the wellhead, and is used for real-time acquisition of the audio signal obtained from the sound wave transmission channel formed by the drilling pipe string and the return fluid, wherein the information acquisition module adopts a hydrophone.

[0012] Preferably, the gas intrusion analysis module is further used to calculate the average sound wave attenuation degree within the first frequency range and the average sound wave attenuation degree within the second frequency range according to the sound wave attenuation degrees in the different frequency bands, and based on this, determine whether gas intrusion occurs underground, wherein the upper limit value of the first frequency range is lower than the lower limit value of the second frequency range.

[0013] Preferably, the gas intrusion analysis module includes: a phenomenon diagnosis unit, which is used to indicate that gas intrusion occurs underground if the average sound wave attenuation degree in the second frequency range is continuously lower than the average sound wave attenuation degree in the first frequency range within a preset time threshold.

[0014] Preferably, the air intrusion analysis module includes: a frequency band attenuation degree generation unit, which is used to calculate the average sound wave intensity of each frequency band and its corresponding average sound wave intensity derivative value according to the spectrum analysis results, and use the average sound wave intensity derivative value to represent the sound wave attenuation degree of the current frequency band.

[0015] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0016] The present invention obtains the audio signal at the wellhead and performs spectrum analysis on it. According to the attenuation degree of the sound amplitude in different frequency bands, the early gas invasion phenomenon can be accurately predicted. There is no need to arrange testing or monitoring instruments underground. The implementation method is simple, safe and reliable, and the construction cost is low.

[0017] Although the present invention will be described below in conjunction with some exemplary implementations and methods of use, it should be understood by those skilled in the art that it is not intended to limit the present invention to these embodiments. On the contrary, it is intended to cover all substitutes, modifications and equivalents within the spirit and scope of the present invention defined by the appended claims.

[0018] Other advantages, objectives, and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the following description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0020] Figure 1The figure is a step diagram of a method for predicting gas invasion during drilling according to an embodiment of the present invention.

[0021] Figure 2 The present invention is a flow chart of a gas invasion phenomenon prediction and analysis process in a method for predicting gas invasion phenomenon in a drilling process according to an embodiment of the present application.

[0022] Figure 3 Schematic diagram of the application environment of the system for predicting gas invasion during drilling according to an embodiment of the present application.

[0023] Figure 4 This is a schematic diagram of the structure of a system for predicting gas invasion during drilling according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0025] In addition, the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be performed in an order different from that shown here.

[0026] Gas invasion during drilling construction refers to the invasion of formation gas into the wellbore and its return to the ground with the drilling fluid. It is one of the most harmful underground complex situations. When the pressure of the drilling fluid column in the wellbore is less than the pressure of the formation fluid, the gas-bearing gas in the formation will invade the wellbore and gas invasion will occur. Since the pressure of the drilling fluid column in the wellbore decreases with the decrease of depth, the volume of the gas invading the wellbore continues to expand during the ascent process, displacing more and more drilling fluid volume, causing the bottom hole drilling fluid pressure to drop rapidly, and more formation fluid will invade the wellbore, causing the gas invasion to worsen sharply. Therefore, the earlier the gas invasion is discovered, the easier it is to deal with it. In the actual drilling operation, it is necessary to detect the gas invasion phenomenon in a timely and accurate manner so that corresponding treatment can be carried out as soon as possible to reduce the harm caused by gas invasion. Therefore, early monitoring of gas invasion is extremely important.

[0027] There are three main methods for monitoring gas intrusion currently in use: (1) Gas logging, which monitors the gas content in the drilling fluid that flows back to the ground to determine whether there is gas intrusion into the drilling fluid. However, this method cannot achieve early detection of gas intrusion. When serious gas intrusion occurs, the degree of gas intrusion is already rapidly deteriorating when gas is detected on the ground. (2) Ultrasonic detection. Ultrasonic transceiver equipment is installed in the wellbore to continuously monitor parameters such as the intensity of ultrasonic waves in the drilling fluid. The changes in ultrasonic parameters caused by gas intrusion can be used to identify gas intrusion. However, in order to achieve early detection, the ultrasonic transceiver must be installed at a deeper well depth. Therefore, it must be combined with fast signal transmission equipment, resulting in high application costs. (3) Using logging information to use Bayesian network analysis to determine gas intrusion risk. This method does not directly detect gas intrusion, and its accuracy is heavily dependent on historical data and historical risk records, which is prone to false alarms and missed alarms. Moreover, gas intrusion will only cause significant changes in logging information when it develops to a more serious level, making it difficult to achieve early gas intrusion detection. (4) Acoustic phase monitoring. Usually, when gas invasion occurs, the propagation speed of sound waves in the drilling fluid will change, which will cause the phase of the sound waves continuously monitored in the return drilling fluid at the wellhead to change. This method is subject to a lot of noise interference, especially when used in deeper wells. It is difficult to eliminate the noise interference from the severely attenuated sound wave signal, and the monitoring accuracy is limited.

[0028] In order to solve the above problems, the present invention proposes a method and system for predicting gas invasion during drilling. During normal drilling, the sound transmitted to the ground along the wellbore fluid column has certain audio characteristics. When gas invasion occurs underground, the bubbles in the drilling fluid have an attenuation effect on the propagation of sound waves. Since the sound waves with a wavelength greater than the diameter of the bubbles are diffracted and their attenuation degree is relatively small, the lower the frequency of the sound wave, the smaller the attenuation degree, and the higher the frequency of the sound wave, the greater the attenuation degree. Therefore, the method and system use an information acquisition module set at or near the wellhead to collect audio signals containing drilling status information (the drilling status here refers to whether gas invasion occurs) transmitted through the wellbore fluid column in real time, and calculate the (average) sound wave attenuation degree of different frequency bands by performing spectrum analysis on the signal. When the attenuation degree of the high-frequency band part is greater than the attenuation degree of the low-frequency band part, it is judged that gas invasion has occurred at this time. In this way, since the time required for the bottom hole sound wave to transmit the audio signal containing the drilling status information to the ground along the drilling pipe and perform gas invasion phenomenon analysis is much shorter than the time for the bubbles generated in the drilling fluid to rise to the wellhead when the gas invasion phenomenon occurs, the present invention can accurately predict the early gas invasion phenomenon by analyzing the attenuation degree of the sound amplitude in different frequency bands, and there is no need to arrange testing or monitoring instruments underground, and the implementation method is simple, safe and reliable, and the construction cost is low.

[0029] Before describing the specific implementation steps of the present invention, the implementation principle of the present invention is first described. In the actual downhole drilling process, the sound generated by the rock breaking of the drill bit at the bottom of the well can be transmitted to the ground through the drilling pipe string. Since the wellbore fluid (wellbore fluid column) constitutes a good sound wave transmission channel, it can transmit sound waves very well. Therefore, the sound generated at the bottom of the well can still maintain a certain intensity when it is transmitted to the ground, which is used for audio analysis. Specifically, in the normal drilling process, the sound transmitted to the ground has certain audio characteristics, and when downhole gas invasion occurs, corresponding bubbles will be generated in the drilling fluid, which have a blocking effect on the propagation of sound waves, so that the amplitude of the sound waves will be significantly attenuated, but the degree of attenuation of sound waves in different frequency bands is different. Further, for sound waves with a wavelength greater than the diameter of the bubble, due to the diffraction phenomenon, the attenuation degree of the sound wave amplitude is relatively small, so the lower the frequency part of the sound wave, the smaller the attenuation degree, and the higher the frequency part, the greater the attenuation degree. In addition, since the gas invading the wellbore is rising, the volume of the bubble continues to increase due to the pressure drop, which will cause the attenuation amplitude of the high-frequency part of the sound wave to increase rapidly. Therefore, by recording the attenuation degree of different frequency components of the acoustic wave signal in the drilling casing transmitted to the ground and detecting in real time whether the attenuation amplitude of the high-frequency part increases, it can be known whether gas intrusion occurs.

[0030] In addition, although the cuttings carried in the drilling fluid will also cause sound wave attenuation, the particle size distribution of the cuttings is relatively stable over a certain period of time and will not cause a continuous increase in the attenuation of sound waves in higher frequency bands like gas invasion.

[0031] Embodiment 1

[0032] Figure 1 FIG. 1 is a step diagram of a method for predicting gas invasion during drilling according to an embodiment of the present invention. Figure 1 As shown, in step S110, the information acquisition module 41 collects the audio signal in the wellbore liquid column that represents the current gas invasion state (whether gas invasion occurs) in the well during the drilling process in real time (continuously) at a preset time interval. In step S120, the information analysis module 42 receives the above-mentioned real-time collected audio signal, and performs real-time spectrum analysis on the audio signal, determines the degree of sound wave attenuation in different frequency bands according to the spectrum analysis results, and judges whether gas invasion occurs in the well based on this. Then, enter step S130, output and respond to the gas invasion diagnosis result, so as to prompt the staff whether gas invasion occurs at present.

[0033] Figure 2 Flow chart of the gas invasion phenomenon prediction and analysis process in the method for predicting gas invasion phenomenon in the drilling process according to the embodiment of the present application. Figure 2As shown, through steps S201 to S207, the audio signal fed back from the bottom of the well is collected in real time and a real-time spectrum analysis is performed to determine whether gas invasion occurs (diagnostic result) and to perform corresponding output. Specifically, in step S201, within each collection time interval, the information collection module 41 collects the audio signal in the sound wave transmission channel formed by the drilling string and the return fluid. The audio signal represents the sound wave signal corresponding to the sound generated by the rock breaking of the drill bit at the bottom of the well, and can reflect the drilling status at the bottom of the well (the drilling status here refers to whether gas invasion occurs). Among them, the information collection module 41 is set in the return fluid in the drilling casing at the wellhead or near the wellhead.

[0034] It should be noted that the present invention does not specifically limit the device used in the information acquisition module 41 , and those skilled in the art may select it according to actual conditions. Preferably, in the embodiment of the present invention, the information acquisition module 41 uses a hydrophone.

[0035] After the audio signal is collected, the process proceeds to step S202, and frequency spectrum analysis is performed on the audio signal collected within the current collection time interval through steps S202 to 206. According to the sound wave attenuation degrees in different frequency bands, the average sound wave attenuation degrees within the first frequency range and the average sound wave attenuation degrees within the second frequency range are calculated respectively. Based on this, it is determined whether gas intrusion occurs underground, so as to analyze and diagnose whether gas intrusion currently occurs underground.

[0036] Further, step S202 receives the above audio signal in real time and performs spectrum analysis on it to obtain corresponding frequency and sound wave intensity (sound wave amplitude) change curve information. The present invention does not specifically limit the spectrum analysis method, and those skilled in the art can select it according to actual conditions. Preferably, in the embodiment of the present invention, the spectrum analysis method adopts the fast Fourier transform method.

[0037] Usually, the sound of the downhole drilling process corresponds to a certain effective detection frequency range. In the embodiment of the present invention, it is necessary to divide this effective detection frequency range into a corresponding number of frequency segments containing different frequency ranges according to the preset frequency interval segment. For example, when the current effective detection frequency range is 0 to 10000 Hz and the frequency interval segment is 1000 Hz, the effective frequency range can be divided into 10 segments, and the frequency span of each frequency segment is 1000 Hz. The range of the first frequency segment is 0 to 1000 Hz, the range of the second frequency segment is 1000 to 2000 Hz, and the range of the third frequency segment is 2000 to 3000 Hz... and so on.

[0038] Then, the process proceeds to step S203, and according to the above spectrum analysis results, the average sound wave intensity of each frequency band and the derivative value of the average sound wave intensity of the frequency band are calculated, and the derivative value of the average sound wave intensity is used to represent the degree of sound wave attenuation of the current frequency band. Since the corresponding audio signal is collected in each signal collection time interval, it is necessary to perform spectrum analysis on the audio signal collected in each time interval, and further record the average sound wave intensity of each frequency band in the time interval and the derivative value of the average sound wave intensity of the frequency band according to the spectrum analysis results in the current time interval, so each continuous time interval is subjected to the same processing to achieve the purpose of continuously recording the average sound wave intensity and its derivative in different frequency bands.

[0039] Further, after calculating the sound wave attenuation degree of each frequency segment within the current acquisition time interval, enter step S204, and calculate the average sound wave attenuation degree within the first frequency range according to the sound wave attenuation degrees of different frequency segments. Among them, the first frequency range represents the frequency range of the low-frequency characteristic part in the audio signal, that is, it refers to the frequency range corresponding to the frequency segment with a smaller frequency range value in the above-mentioned effective detection frequency range. Further, if the above-mentioned effective detection frequency range is divided into a corresponding number of frequency segments containing different frequency ranges according to a preset frequency interval segment, and arranged in order from low to high according to the frequency segment values, preferably, the first half of the different frequency segments in the effective detection frequency range can be divided into the first frequency range. Specifically, according to the sound wave attenuation degrees of different frequency segments within the first frequency range, based on this, these sound wave attenuation degrees are averaged and processed to obtain the corresponding average sound wave attenuation degree within the first frequency range.

[0040] Further, proceed to step S205, and calculate the average sound wave attenuation degree within the second frequency range according to the sound wave attenuation degree of different frequency bands. Wherein, the second frequency range represents the frequency range of the high-frequency characteristic part in the audio signal, that is, the frequency range corresponding to the frequency band with a larger frequency range value in the above-mentioned effective detection frequency range. Further, if the above-mentioned effective detection frequency range is divided into a corresponding number of frequency bands containing different frequency ranges according to a preset frequency interval segment, and arranged in order from low to high according to the frequency band value, preferably, the second half of the different frequency bands in the effective detection frequency range can be divided into the second frequency range, that is, the frequency band that does not belong to the first frequency range. It can be seen from this that the upper limit frequency value corresponding to the first frequency range in the embodiment of the present invention is less than the lower limit frequency value corresponding to the second frequency range.

[0041] Specifically, according to the sound wave attenuation degrees of different frequency bands within the second frequency range, based on this, these sound wave attenuation degrees are averaged to obtain the average sound wave attenuation degree within the corresponding second frequency range.

[0042] Next, after continuously recording the sound wave attenuation degree corresponding to the low-frequency part of the audio signal and the sound wave attenuation degree corresponding to the high-frequency part of the audio signal within the preset time threshold, whether gas invasion occurs in the well is diagnosed until the time threshold is reached, and then the process goes to step S206. Specifically, step S206 determines whether the average sound wave attenuation degree in the second frequency range is continuously lower than the average sound wave attenuation degree in the first frequency range within the preset time threshold according to the average sound wave attenuation degree in the first frequency range and the average sound wave attenuation degree in the second frequency range. Based on this, whether gas invasion occurs in the current well is diagnosed, and the corresponding gas invasion diagnosis result is obtained.

[0043] It should be noted that the present invention does not specifically limit the value of the time threshold, and those skilled in the art may set it according to actual conditions. Preferably, in the embodiment of the present invention, the time threshold is 5s.

[0044] Specifically, in one embodiment, within a preset time threshold, if the average sound wave attenuation degree within the second frequency range obtained in the above step S205 is continuously lower than the average sound wave attenuation degree within the first frequency range obtained in the above step S204, it indicates that gas intrusion has occurred underground, and accordingly an effective warning signal indicating the occurrence of underground gas intrusion (gas intrusion diagnosis result) is generated.

[0045] In another embodiment, within a preset time threshold, if the average sound wave attenuation degree within the second frequency range obtained in the above step S205 is not continuously lower than the average sound wave attenuation degree within the first frequency range obtained in the above step S204, it indicates that no gas intrusion has occurred in the current well, and accordingly an invalid warning signal (gas intrusion diagnosis result) is generated indicating that no gas intrusion has occurred in the well.

[0046] Finally, after obtaining the gas intrusion diagnosis result, the process proceeds to step S207. Step S207 receives the gas intrusion diagnosis result, responds to it, and outputs it. In the event of gas intrusion, an effective warning signal is responded to by a warning device (not shown, such as a buzzer, an indicator light, etc.) to prompt the staff, so that the staff can perform manual detection or perform corresponding countermeasures for the underground gas intrusion situation.

[0047] In this way, the above technical solution is used to calculate (continuously calculate) in real time the average sound wave intensity and its derivative value in each frequency segment within each acquisition time interval, calculate the average sound wave attenuation degree within the first frequency range within each acquisition time interval, and calculate the average sound wave attenuation degree within the second frequency range within each acquisition time interval. Furthermore, by continuously processing the acquisition time intervals contained in the preset time threshold and recording the calculation results (the average sound wave attenuation degree within the first frequency range and the average sound wave attenuation degree within the second frequency range), the underground gas invasion phenomenon is diagnosed, thereby completing real-time monitoring of early gas invasion situations.

[0048] Embodiment 2

[0049] Based on the above-mentioned embodiment 1, a specific example of a method for predicting gas invasion during drilling process proposed by the present invention is given.

[0050] (1) A hydrophone is installed in the ground drilling casing, and the collected audio signals are transmitted to the information analysis module 42 in the industrial computer via a signal transmission cable.

[0051] (2) Start the industrial computer and run the analysis program. The analysis program continuously performs fast Fourier transform processing on the audio signal and divides the obtained spectrum into a frequency band of 1000 Hz. The frequency band from 0 to 10000 Hz is divided into 10 frequency bands, which are numbered from 1 to 10 from low to high. The average sound intensity of each frequency band and the derivative of the average sound intensity with respect to time are recorded.

[0052] (3) Drilling operation begins, and the analysis program continuously monitors the sound intensity derivative of each frequency band. When the average value of the sound intensity derivative of frequency bands 6 to 10 is found to be less than the average value of the sound intensity derivative of frequency bands 1 to 5 for 5 consecutive seconds, it is determined that gas intrusion has occurred.

[0053] Embodiment 3

[0054] Based on the methods corresponding to the first and second embodiments of the present invention, the present invention further proposes a system for predicting gas invasion during drilling, which uses the above-described method to predict early gas invasion during downhole drilling. Figure 3 Schematic diagram of the application environment of the system for predicting gas invasion during drilling according to an embodiment of the present application. Figure 4 This is a schematic diagram of the structure of the system for predicting gas invasion during drilling according to an embodiment of the present application. Figure 3 and Figure 4 The above system will be described in detail.

[0055] like Figure 3 , Figure 4As shown, the system includes: an information acquisition module 41, an information analysis module 42 and a result output module 43. Among them, the information acquisition module 41 is set in the return fluid in the wellhead drilling casing, and is implemented according to the above step S110, and is configured to collect the audio signal in the wellbore liquid column that represents the real-time gas invasion situation in the well during the drilling process in real time (continuously) at a preset time interval. The information analysis module 42 is integrated in the well (ground) industrial control computer and is connected to the above information acquisition module 41 through a signal transmission cable. It is implemented according to the above step S120, and is configured to receive the audio signal and perform spectrum analysis on the audio signal. According to the spectrum analysis results, the degree of sound wave attenuation in different frequency bands is determined, and based on this, it is judged whether gas invasion occurs in the well. The result output module 43 is a warning device (not shown, such as a buzzer, indicator light, etc.), which is connected to the above ground industrial control computer. It is implemented according to the above step S130, and is configured to output and respond to the gas invasion diagnosis result.

[0056] Specifically, refer to Figure 4 The information acquisition module 41 preferably adopts a hydrophone, which is further implemented according to the above step S201 and is configured to collect in real time the audio signal obtained from the sound wave transmission channel formed by the drilling string and the return fluid.

[0057] The information analysis module 42 includes: a frequency analysis unit 421, a frequency band attenuation degree generation unit 422, a first average sound wave attenuation degree generation unit 423, a second average sound wave attenuation degree generation unit 424, and a phenomenon diagnosis unit 425, which is further implemented according to the above steps S202 to S206, and is configured to calculate the average sound wave attenuation degree within the first frequency range and the average sound wave attenuation degree within the second frequency range according to the sound wave attenuation degrees of different frequency bands, and based on this, determine whether gas intrusion occurs in the well, wherein the upper limit value of the first frequency range is lower than the lower limit value of the second frequency range.

[0058] Furthermore, the frequency analysis module 421 is implemented according to the above step S202 and is configured to receive the above audio signal in real time and perform spectrum analysis on it to obtain corresponding frequency and sound wave intensity (sound wave amplitude) change curve information.

[0059] The frequency band attenuation degree generating unit 422 is implemented in accordance with the above-mentioned step S203 and is configured to calculate the average sound wave intensity of each frequency band and the derivative value of the average sound wave intensity of the frequency band according to the above-mentioned spectrum analysis results, and use the derivative value of the average sound wave intensity to represent the sound wave attenuation degree of the current frequency band.

[0060] The first average sound wave attenuation degree generating unit 423 is implemented according to the above step S204 and is configured to calculate the average sound wave attenuation degree within the first frequency range according to the sound wave attenuation degrees of different frequency bands.

[0061] The second average sound wave attenuation degree generating unit 424 is implemented according to the above step S205 and is configured to calculate the average sound wave attenuation degree within the second frequency range according to the sound wave attenuation degrees of different frequency bands.

[0062] The phenomenon diagnosis unit 425 is implemented according to the above step S206, and is configured to determine whether the average sound wave attenuation degree in the second frequency range is continuously lower than the average sound wave attenuation degree in the first frequency range within a preset time threshold according to the average sound wave attenuation degree in the first frequency range and the average sound wave attenuation degree in the second frequency range, and based on this, diagnose whether gas invasion occurs in the current well and obtain corresponding gas invasion diagnosis results. In one embodiment, if the average sound wave attenuation degree in the second frequency range obtained by the second average sound wave attenuation degree generation unit 424 is continuously lower than the average sound wave attenuation degree in the first frequency range obtained by the first average sound wave attenuation degree generation unit 423 within the preset time threshold, it indicates that gas invasion occurs in the well.

[0063] The result output module 43 is implemented according to the above step S207 and is configured to receive the gas intrusion diagnosis result, respond to it and output it. In the event of gas intrusion, the staff is prompted through a warning device (not shown, such as a buzzer, indicator light, etc.), so that the staff can perform manual detection or implement corresponding response measures for the underground gas intrusion situation.

[0064] In summary, the present invention relates to an audio signal collection and analysis method for early warning of gas intrusion during drilling. During the drilling process, the sound waves in the wellbore casing are collected, the sound intensity of different frequency bands is continuously analyzed, the derivative is calculated, and the sound intensity derivatives of the low-frequency band and the high-frequency band are continuously compared; when the sound wave intensity derivative of the high-frequency band is lower than the sound wave intensity derivative of the low-frequency band for a period of time, it is judged that gas intrusion has occurred. The present invention does not need to arrange instruments underground, the system is mainly composed of ground instruments, the arrangement and implementation method is simple, safe and reliable, and the construction cost is low. Furthermore, the monitoring results of the present invention are independent of the performance of the drilling fluid used, can eliminate the interference of rock cuttings, and have a higher accuracy rate. In addition, the present invention can detect complex situations underground earlier, and there is no need to wait until the gas invading the wellbore rises to the ground, and the gas intrusion phenomenon can be discovered based on the sound waves transmitted to the ground.

[0065] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for predicting gas invasion during drilling, characterized in that: include: Step 1: Use an information collection module in the return fluid in the drilling casing at or near the wellhead to continuously collect audio signals in the wellbore fluid column during the drilling process. The audio signal represents the sound wave signal corresponding to the sound generated by the rock breaking of the drill bit at the bottom of the well to reflect the drilling status at the bottom of the well; Step 2: Receive the audio signal and perform spectrum analysis on the audio signal, determine the attenuation of sound waves in different frequency bands according to the spectrum analysis results, and based on this, judge whether gas invasion occurs underground, including: According to the attenuation of the sound waves in the different frequency bands, the average attenuation of the sound waves in the first frequency range and the average attenuation of the sound waves in the second frequency range are calculated respectively, and within a preset time threshold, if the average attenuation of the sound waves in the second frequency range is continuously lower than the average attenuation of the sound waves in the first frequency range, it indicates that gas invasion occurs in the well, wherein the upper limit value of the first frequency range is lower than the lower limit value of the second frequency range, In the step 2, it includes: According to the effective detection frequency range of the audio signal, the effective detection frequency range is divided into different frequency segments according to the preset frequency interval segments and the sound wave attenuation degree of each frequency segment is calculated; According to the frequency segment values, all the frequency segments are arranged in polarity from low to high, the first half of the different frequency segments in the effective detection frequency range is divided into a first frequency range, so as to use the first frequency range to represent the frequency range of the low-frequency characteristic part of the audio signal, and the second half of the different frequency segments in the effective detection frequency range is divided into a second frequency range, so as to use the second frequency range to represent the frequency range of the high-frequency characteristic part of the audio signal; The average sound wave attenuation degree of the first frequency range is obtained by calculating the average value of the sound wave attenuation degrees of different frequency segments within the first frequency range, and the average sound wave attenuation degree of the second frequency range is obtained by calculating the average value of the sound wave attenuation degrees of different frequency segments within the second frequency range; Step 3: Output and respond to gas intrusion diagnosis results.

2. The method for predicting gas invasion during drilling according to claim 1, characterized in that: In the step 1, the audio signal in the acoustic wave transmission channel formed by the drilling string and the return fluid is collected in real time, wherein the information collection module uses a hydrophone.

3. The method for predicting gas invasion during drilling according to claim 1, characterized in that: In the step 2, the average sound wave intensity of each frequency band and its corresponding average sound wave intensity derivative value are calculated according to the spectrum analysis result, and the average sound wave intensity derivative value is used to represent the degree of sound wave attenuation in the current frequency band.

4. A system for predicting gas invasion during drilling, characterized in that: The system uses the method according to any one of claims 1 to 3 to predict the early gas invasion phenomenon in the downhole drilling process, and the system comprises: An information acquisition module is provided in the return fluid in the drilling casing at or near the wellhead, and is used to continuously acquire the audio signal in the wellbore fluid column during the drilling process. The audio signal represents the sound wave signal corresponding to the sound generated by the rock breaking of the drill bit at the bottom of the well to reflect the drilling status at the bottom of the well; A gas intrusion analysis module, which is used to receive the audio signal, perform spectrum analysis on the audio signal, determine the attenuation degree of sound waves in different frequency bands according to the spectrum analysis result, and based on this, judge whether gas intrusion occurs in the well; The result output module outputs and responds to the gas intrusion diagnosis results. The gas invasion analysis module is further used to calculate the average sound wave attenuation degree within the first frequency range and the average sound wave attenuation degree within the second frequency range according to the sound wave attenuation degree of the different frequency bands, and within a preset time threshold, if the average sound wave attenuation degree within the second frequency range is continuously lower than the average sound wave attenuation degree within the first frequency range, it indicates that gas invasion occurs underground, wherein the upper limit value of the first frequency range is lower than the lower limit value of the second frequency range, The air intrusion analysis module is further used to divide the effective detection frequency range into different frequency segments according to the preset frequency interval segment according to the effective detection frequency range of the audio signal and calculate the sound wave attenuation degree of each frequency segment, and then arrange all the frequency segments in polarity from low to high according to the frequency segment values, divide the first half of the different frequency segments in the effective detection frequency range into a first frequency range, so that the first frequency range can be used to represent the frequency range of the low-frequency characteristic part of the audio signal, and divide the second half of the different frequency segments in the effective detection frequency range into a second frequency range, so that the second frequency range can be used to represent the frequency range of the high-frequency characteristic part of the audio signal, and finally, by calculating the average value of the sound wave attenuation degree of different frequency segments within the first frequency range, the average sound wave attenuation degree of the first frequency range is obtained, and by calculating the average value of the sound wave attenuation degree of different frequency segments within the second frequency range, the average sound wave attenuation degree of the second frequency range is obtained.

5. The system for predicting gas invasion during drilling according to claim 4, characterized in that: The information acquisition module is also used to collect in real time the audio signal obtained from the sound wave transmission channel formed by the drilling pipe string and the return fluid, wherein the information acquisition module adopts a hydrophone.

6. The system for predicting gas invasion during drilling according to claim 5, characterized in that: The gas intrusion analysis module includes: The frequency band attenuation degree generating unit is used to calculate the average sound wave intensity of each frequency band and its corresponding sound wave average intensity derivative value according to the spectrum analysis result, and use the sound wave average intensity derivative value to represent the sound wave attenuation degree of the current frequency band.

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