KR101270885B1 - Method of picking of first arrival time for reliable measurement of the velocity of elastic wave - Google Patents

Abstract

The present invention relates to a method of extracting the super-acoustic wave for the measurement of the elastic wave velocity to enable the accurate measurement of the time when the acoustic wave passes through the sample core, comprising the steps of: sending the elastic wave to the rock core; and receiving the elastic wave received through the rock core. A method of extracting a super-movement, comprising the steps of: (a) setting a reference viewpoint acquisition gap with respect to a received acoustic wave waveform; (b) acquiring a moment at which the received acoustic wave waveform is captured in the reference acquisition gap as a reference time at the time of initial movement; (c) selecting a candidate starting point at the time of starting the swing at a point after the amplitude is stabilized among the preceding points of the starting point in the starting point; (d) further selecting at least one super-viewing time of monitoring at a time point around the candidate time of the time-of-viewing; And (e) extracting the initial starting time at the time point at which the sampling value indicates a value close to 0 by sampling the selected starting time candidate time and the waveform at the monitoring time. Characterized in that it comprises a.

Description

METHOD OF PICKING OF FIRST ARRIVAL TIME FOR RELIABLE MEASUREMENT OF THE VELOCITY OF ELASTIC WAVE}

The present invention relates to a method of extracting ultra-high frequency for measuring seismic velocity, and more particularly, to a method of extracting ultra-high frequency for measuring seismic velocity allowing the measurement of an accurate time when a seismic wave passes through a sample core.

Physical property measurement is a basic technology that is used in a wide range of fields such as energy, resources, geological survey, geological environment and geological disaster, civil engineering and construction, as well as carbon dioxide underground storage and global environmental change research. Based on a clear understanding of the behavior of seismic velocities, it is possible to draw reasonable conclusions about hydrogeological or geothermal properties from a variety of physical exploration data.

Overseas, this foundational technology has been recognized early, and in the case of seismic velocity measurement, studies on seismic velocity changes due to pressure and temperature changes have been made since the 1950s (Hughes and Jones, 1950). In addition, developed countries in Europe, including Germany, have systems for measuring and monitoring physical properties under high temperature and high pressure environments (Lee, et al., 2007).

Conventionally, a device for measuring the seismic velocity has been developed and used (Korean Patent Application No. 2008-0003303). However, in the measurement of the seismic velocity using the device, the problem of the measurement of the initial pulsation excerpted during the excitation of the initial pulsation is longer than it actually is. In addition, since the excitation point is unstable due to noise, the initial observation also increases, and when there is a sudden electrical noise, the excitation point of the initial observation has many unstable parts. There is a problem that can not be achieved.

The present invention has been made to solve the above problems, an object of the present invention is to provide a method for extracting super-acoustic wave for the measurement of the seismic velocity to enable the accurate measurement of the time when the seismic waves pass through the sample core.

According to an aspect of the present invention, the method of extracting the acoustic wave to the rock core and the step of receiving the received acoustic wave through the rock core, the method of extracting at the same time, (a) the reference to the received acoustic wave waveform Setting a viewpoint acquisition gap; (b) acquiring a moment at which the received acoustic wave waveform is captured in the reference acquisition gap as a reference time at the time of initial movement; (c) selecting a candidate starting point at the time of starting the swing at a point after the amplitude is stabilized among the preceding points of the starting point in the starting point; (d) further selecting at least one super-viewing time of monitoring at a time point around the candidate time of the time-of-viewing; And (e) extracting the initial starting time at the time point at which the sampling value indicates a value close to 0 by sampling the selected starting time candidate time and the waveform at the monitoring time. Characterized in that it comprises a.

Preferably, in the step (a), the reference point acquisition gap is set to a level above the average noise level on the basis of the dc offset line that changes from time to time.

Preferably, in step (c), the candidate time of the super-movement movement is selected as a time when the deviation starts from the dc offset line at a stable time point.

Preferably, in the step (d), the super-viewing time of monitoring is characterized in that it is further selected at the time before and after the candidate time of the initial view.

Preferably, in the step (e), the sampling is characterized in that the sampling value is calculated by averaging the measured values for a predetermined time with respect to the waveform of the selected candidate time and the monitoring time.

According to the present invention, there is an effect that can extract accurate and reliable initial movement for measuring the time when the acoustic wave passes through the sample core.

In particular, compared to the conventional extraction method by the gap setting, a large number of candidate time points and monitoring points are selected and sampled to extract the initial injection time, thereby increasing the accuracy and reliability of the extraction.

1 is a view showing an experimental apparatus to which the present invention is applied.
FIG. 2 is a view for explaining a method of extracting the initial motion of the conventional method using the experimental apparatus of FIG. 1. FIG.
Figure 3 is a view for explaining a method of extracting the initial motion of the present invention using the experimental apparatus of Figure 1;
Figure 4 is a view for explaining the comparison between the ultra-modern poetry extracted according to the conventional method and the method of the present invention.
Figure 5 is a flow chart for explaining a method of extracting at the time of superimposition according to the present invention.

Hereinafter, a description will be given in more detail with reference to the accompanying drawings of an embodiment of a method for extracting the ultra-high frequency for measuring the seismic velocity according to the present invention.

1 is a view showing an experimental apparatus to which the present invention is applied.

In the following description, the experimental apparatus of FIG. 1 will be described, and the conventional ultra-collective extraction method using the experimental device will be described by comparing the conventional ultra-collective extraction method according to the present invention.

In addition to other systemic factors that affect the accurate measurement of seismic velocity of rocks, the accurate measurement of the time that the seismic waves pass through the sample core is an important parameter in real measurements. The velocity of a seismic wave through a rock core is calculated from the length of the core and the travel time at which the transmit waveform arrives at the receiver (transducer), where the excerpt from the exact time the seismic wave reaches the receiver is the velocity. This is a very important factor in determining the accuracy of the measurement.

Referring to FIG. 1, an experimental apparatus to which the present invention is applied includes a transmitter 10, a core holder 20, a signal processor 30, and an analysis system 40.

The transmitter 10 is designed to switch the 1,000 V current applied to the high voltage transistor to 1 μsec every time the trigger is performed at 60 Hz. The internal circuit rectifies 220 V to generate a 1000 V DC voltage. The trigger terminal creates a single pulse from a 60 Hz square wave in a mono-stable multivibrator circuit. When triggered by a high voltage transistor, the trigger terminal drops from high voltage to low voltage and then rises to the original 1000 V and takes time. This is about 1 μsec. The high voltage pulse signal thus produced is supplied to the input terminal of the transmission transducer 28a mounted on the core holder 20.

The core holder 20 is to compress the both ends of the rock core (C) at a constant pressure to measure the elastic wave velocity of the rock core (C) while holding the rock core (C) firmly, A support 21 on which the transducer 28a is mounted, a support 23 positioned above the support 21, and positioned between the support 23 and the support 21 are movable up and down, and the transmission transformer A presser bar 22, which is coupled to the producer 28a and a receiver transducer 28b protrudes downward, is installed on the holder 23 so that the pusher 22 is fixed to the holder 23 and the supporter ( It comprises a vertical rotation means for moving up and down between 21).

Here, the connecting rod 400 is inserted into a guide hole formed in the pressing rod 22 to guide the vertical movement of the pressing rod 22, and the rotating means applies a rotational force to the bevel gear to move the moving rod 25 to the axis. Rotated. In response to the rotation of the movable rod 25, the push rod 22 moves up and down to press-fix the rock core C between the transmitting transducer 28a and the receiving transducer 28b.

In addition, the support 21 of the core holder 20 may be provided with a spherical sheet 26 so that the compressive force is orthogonal to the upper and lower surfaces of the rock core (C), the rock while the load cell 27 extracts the initial movement The celebration of the celebration between the core C and the transceiving transducer is detected.

The signal processor 30 includes a terminal board 31, a differential amplifier 32, a digital processor indicator (DPI) 33, and a data acquisition system (DAS) 34.

The terminal board 31 receives information about an external trigger signal from the transmitter 10 and inputs it to the DAS 34.

The differential amplifier 32 is used to amplify the acoustic wave signal received through the rock core C to the receiving transducer 28b and may also function as a bandpass filter to remove noise as necessary. This amplified signal is input to the DAS 34.

The DPI 33 is a device for displaying a load applied to the rock core C. During extraction of the first movement, the DPI 33 receives and displays the congratulations between the rock core C and the transceiving transducer from the lower load cell 27. do. Based on the state just before the rock core (C) and the transceiving transducer are first contacted, the vertical displacement of the receiving transducer (28b) and the resulting load are monitored while the actual load deviates from the desired load by a certain level. By adding downward vertical displacement it is possible to automatically maintain a constant load. The measured load information is input to the DAS 34.

The DAS 34 is capable of multi-channel input and has a resolution of 12 bits. Analysis system by collecting information on the external trigger signal generated from the transmitter 10, information on the acoustic wave signal transmitted from the receiving transducer 28b and information on the load transmitted from the DPI 33 ( 40). The DAS 34 is designed in a 32-bit PCI structure and mounted in a PC slot. It supports Windows Plug and Play, so it can be easily installed and controlled by the program.

On the other hand, the analysis system 40 samples the traveling time in μsec units until the wave transmitted from the transmitting transducer 28a passes through the rock core C and the first arrival reaches the receiving transducer 28b.

Referring to FIG. 2, the conventional method of extracting ultra-high motion using the experimental apparatus is as follows.

The resultant data of FIG. 2 is the measurement of the p-wave initial vortex while applying an 80 kg (110.9 N / cm 2) axial load on an acrylic test piece having a length of 40 mm.

In this method, every time the excerpts are extracted, the gaps that exceed the average noise level are specified based on the dc offset line (the green horizontal line in Fig. 2) that changes frequently (-10 mV in Fig. 2), thereby automatically starting the Ts (T). ₀ ) excerpt.

At this time, the gap can be extracted automatically by specifying the gap properly (the selection of the gap is empirical). However, the larger the gap, the longer the extracted gap is measured.

In addition, since the excitation point T ₀ is unstable in amplitude due to noise, the deviation is large when continuously measuring the initial movement time (see the upper sampling result of FIG. 4), and an abrupt point may be extracted when sudden electrical noise occurs.

That is, continuous experiments are essential to secure a reasonable and accurate first arrival driving time (first arrival time), and in the conventional first extraction time method, the acoustic wave transmitted from the transmission transducer 28a receives the reception transducer 28b. Auto-extraction method to sample the dc offset measured until it reaches to the driving time in μsec unit, and to select the driving time when the signal abnormality is larger than ± gap in mV unit. Was used.

The gap is determined by the experimenter according to the noise level from the received waveform. In general, if the experiment in the room ± gap is set to around 10mV.

The present invention proposes a method of measuring the most reasonable initial driving time by selecting and comparing values near the first driving time by improving a method of automatically extracting the initial initial starting time when the initial driving time more than ± gap appears in the received signal. This improved method shows stable repeatability with small deviations in continuous experiments and can be used as a reliable method for automatic extraction during initial injection.

Referring to FIG. 3, in order to compensate for the anxiety of the previous method of measuring only one excerpt point T ₀ , a gap (−100 mV in FIG. 3) is set at a position after the amplitude is stabilized, followed by driving time backwards first. Find the candidate candidate time T ₁ . If the excerpted superimposition is suitable for the candidate time point T ₁ , the amplitude at the driving time will oscillate below the noise level with each sampling, and the average value measured continuously for a certain time will be close to zero. cross over point). In addition, the accuracy of excerpts was increased by selecting the amplitudes of T ₂ and T ₃ as the additional monitoring time points near the candidate time T ₁ .

Figure 4 shows the conventional method and the ultra-universe excerpt extracted according to the method of the present invention with an average value, according to the conventional method (upper sampling result of Figure 4) compared to the method of the present invention (lower sampling result of Figure 4) First excerpts are largely excerpted and the deviation from the mean is greater.

Now with reference to Figure 5 looks at in detail with respect to the ultra-high excitation method for measuring the seismic velocity according to the present invention.

First, the above-described experimental apparatus is set and the acoustic wave transmitted from the transmitter 10 passes through the rock core C installed in the core holder 20 and is input to the analysis system 40 through the signal processor 30. The received waveform input to the analysis system 40 and displayed is as shown in FIG. 4.

As a gap setting step for acquiring the reference viewpoint in S10, a gap is set for the received waveform. Here, the gap can be relatively stable at a sufficiently stable position where the waveform amplitude is stable. Preferably, the gap is above the average noise level based on the dc offset line (green horizontal line) that changes frequently. It is good to set. In FIG. 5 the gap was set to -100 mV.

Next, as the initial reference time point acquisition step of S20, a moment captured by the gap set in the received waveform is acquired as the initial reference time point T ₀ . This initial reference time T ₀ is the moment when a signal larger than the gap set in step S10 is captured by the receiver.

Next, as a step of selecting the candidate starting time of the hyper-view during S30, the candidate time-of-start candidate T ₁ is selected from the time point after the amplitude is stabilized among the points before the reference time T ₀ . Herein, the candidate time T ₁ at the time of initial motion may be selected between the noise disappearing and the amplitude is stabilized and the reference time T ₀ at the time of initial motion, and preferably, the time at which the amplitude starts to deviate from the dc offset line at the time when the amplitude is stable It is recommended to select the candidate time T ₁ at the time of initial movement.

Here, if the candidate time T ₁ at the time of super-movement is well selected, the amplitude at that time will oscillate within ± noise level at each sampling, and the average of the measured values for a certain period of time will give a cross over point. If you set the candidate time T ₁ at the time of initial movement, you can automatically repeat the measurement later.

Next, as a step of selecting the super-viewing time of the supersonic view of S40, the super-viewing time of the monitoring time T ₂ and T ₃ are further added to the peripheral time points of the candidate time of the super-viewing time T ₁ , and preferably, before and after the time of the initial view of the starting time of the starting time candidate T ₁ . Choose. Considered first arrival at this monitoring time T ₂ and T ₃ may be each set to ± 0.1 micro-sec in the candidate time T ₁ considered the first arrival, these first arrival notice monitoring time does not have to select only the above-described two points, a more stable first arrival is a number selected before and after the first arrival notice candidate time T ₁ to give the extract can be made without departing from the scope of the monitoring point, consider the actual first arrival notice the first arrival notice candidate time and a first arrival. In addition, in order to extract a more accurate ultra-primary poetry, the time interval before and after the initial candidate candidate T ₁ can be more closely spaced, so that a plurality of super-unichronous moni- tor monitoring points can be arranged so that the exact timing of the actual initial poetry can be captured. In FIG. 5, the superimposition monitoring time points T ₂ and T ₃ were respectively selected from ± 0.1 micro-sec of the superimposition candidate time point T ₁ .

Next, as a sampling stage of the candidate starting point and the monitoring time of S50, the measured values of the candidate starting point and the monitoring time of the selected starting point are averaged for a predetermined time. In practice, this sampling value results in a cross over point whose amplitude is close to zero.

Next, as a step of determining the initial startup time of S60, the accurate initial startup time can be determined with respect to the time point at which the sampling value closest to zero is compared by comparing the sampling values.

Figure 4 shows the initial motion taken with the conventional method and the method according to the present invention with the average value. Referring to Figure 4 can be confirmed that the initial excitation repeatedly extracted several times the initial excitation according to the invention shows a stable repeatability.

On the other hand, it can be seen that the conventional method with an average of 14.889 μsec at the time of initial injection is 0.513 μsec (+ 1.04%) longer than the method of the present invention with an average of 14.736 μsec at the time of initial injection, and the deviation from the average value (solid line) is also seen to be large. This difference in the extraction method can be eliminated by correcting using the same extraction method when calculating the system delay.

On the other hand, the method of extracting the super-acoustic wave for measuring the seismic velocity according to the embodiment of the present invention may be implemented in the form of program instructions that can be executed through various electronic means for processing information and recorded in the storage medium. The storage medium may include program instructions, data files, data structures, and the like, alone or in combination.

Program instructions to be recorded on the storage medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of software. Examples of storage media include magnetic media such as hard disks, floppy disks and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic-optical media such as floppy disks. hardware devices specifically configured to store and execute program instructions such as magneto-optical media and ROM, RAM, flash memory, and the like. In addition, the above-described medium may be a transmission medium such as an optical or metal wire, a waveguide, or the like including a carrier wave for transmitting a signal specifying a program command, a data structure, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as devices for processing information electronically using an interpreter or the like, for example, a high-level language code that can be executed by a computer.

The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, an optimal embodiment has been disclosed in the drawings and specification. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

10: transmitter 20: core holder
30: signal processor 40: analysis system

Claims (5)

In the super-movement extracting method comprising the step of transmitting the acoustic wave to the rock core, and receiving the received acoustic wave through the rock core,
(a) setting a reference view acquisition gap with respect to the received acoustic wave waveform;
(b) acquiring a moment at which the received acoustic wave waveform is captured in the reference acquisition gap as a reference time at the time of initial movement;
(c) selecting a candidate starting point at the time of starting the swing at a point after the amplitude is stabilized among the preceding points of the starting point in the starting point;
(d) selecting a first monitoring time point in addition to a peripheral time point of the first starting time candidate time; And
(e) sampling the waveform at each time point at the selected candidate time and monitoring time point, and extracting the first time time at which the sampling value is closest to zero; Ultra-extracting method extract, characterized in that it comprises a.
The method of claim 1,
In the step (a)
And the reference point acquisition gap is set to a level above the average noise level based on a dc offset line that changes frequently.
The method of claim 1,
In the step (c)
And the candidate starting time point is selected as a time point at which the amplitude starts to deviate from the dc offset line at a stable time point.
The method of claim 1,
In the step (d)
The first injection monitoring time point is characterized in that the addition of the first and second candidates, characterized in that additional selection is selected.
The method of claim 1,
In the step (e)
The sampling is a first extraction method characterized in that the sampling value is calculated by averaging the measured values for a predetermined time with respect to the waveform of the candidate time and the monitoring time.

Images