Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Earth science
Reexamination Certificate
2001-05-18
2004-03-09
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Earth science
C181S116000
Reexamination Certificate
active
06704657
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for accurately measuring propagation (traveling) time of the seismic wave, and more particularly, to a method and an apparatus for accurately determining the detonation time TB (also referred to as “time break”) and the first arrival time (FAT) TR of the first arrival seismic wave (FASW) at the detonation uphole (or detonation point) in the field of seismic exploration.
BACKGROUND OF THE INVENTION
The method and the apparatus used in the prior art have considerable limitation on the determination of the detonation time, the accurate detonation time can not be acquired properly.
It should be noted that the article “Optical fiber time break”, GEOPHSICS V61, No. 1, pp. 294-298,January-February 1996 (ISSN00168033), is worth notice. The technique revealed by this article and the method used therein are the insertion of a optical fiber into the explosive package with an end inserted into the explosive package as the signal detecting end to detect the high light emerged at the explosion of the explosive; and the light signal caused by the explosion is monitored at the other end of the optical fiber, with the output time of the light signal at the monitoring end being the explosion time. This method is both scientific and accurate, without the detection of the signal being subjected to electromagnetic interference (Very strong electromagnetic occurs at ignition), while this method is very good, it is not appropriate for mass production of seismic waves due to its high cost of materials and complicated construction, the cost of which is too high in mass application.
It should be noted that there is another method applicable under special conditions, a conductor is wound around the detonator, upon the detonation of the detonator, and the breaking time of the wire is taken as the detonation time. It should also be noted that this method is subject to strong electromagnetic interference, the detonation time determined by which is not so accurate as the determined by the above-mentioned optical detection method. As with the above-mentioned optical detection method, the construction cost in creases due to the increasing complexity of construction, the cost of which is also cost of which is also too high in mass application.
In addition, it should also be noted that a technique has been used in the recording of the detonation signal, with a detector placed at the detonation point in this technique to pick up the vibration produced in the detonation, then this signal is recorded on the instrument for final analyzing and determining the detonation time.
The technique extensively used by blasters (seismic source synchronizer) is the use of a transformer in the detonation means to couple and output the detonation current signal of the igniting detonator (snap cap, also referred to as “CAP”), and the detonation time is determined by the output current signal. This method can be used to roughly determine the detonation time TB, since there will be a certain delay in the detonation of igniting CAP, therefore, in this method, the “time break” signal is output after a certain delay following the detecting of the detonation current signal to indicate the detection of the detonation time. It can be seen that this method is rough, and thereby that is the limitation of this method which causes the under-improvement of the detonation time detecting method currently massively used in engineering.
In addition, there are following methods to detect the first arrival time of the first arriving wave: automatic fuzzy detection approach; inflexion point approach (differential approach); correlation approach; and extreme approach of correlation between seismic source signal and recording track. The automatic fuzzy detection approach introduces the basic concepts of artificial intelligence into the automatic pick-up of the first arriving waves in the multi-track seismic signals to improve the accuracy, reliability and applicability of detection. The creation of a subordination of function covers the “first arrival approach”, “inflexion (differential) approach”, “seismic focus signal and recording track correlation approach”, “peak value approach” and “adjacent track correlation approach”, after the creation of the subordination function, it is implemented by the following main steps:
(1) analyzing the seismic source sub-wave to obtain necessary parameters;
(2) applying the automatic detecting Chronos method and spatial correlation of the first arriving wave on the first track (or last track) of the record to roughly partition the ranges (or temporal and spatial windows) in which the first arrival resides;
(3) Detecting the first arrival time with various methods in the temporal and spatial window and determining various parameters necessary for determining the subordination function, and calculating corresponding subordination degree;
(4) Determining the first arrival time (automatic fuzzy detection approach) and relative parameters, a threshold &lgr; should be given to each subordination degree based on the characteristics of the first arrival time subordination degree obtained with various approaches, reserving those subordination degrees greater than &lgr; and resetting those less than &lgr;, forming a matrix &bgr; by each of the subordination degrees, and taking the &lgr;-truncated matrix of &bgr;:&bgr;
&lgr;
,&lgr;&egr;[0,1] and letting
S=&bgr;
&lgr;
∩&bgr;
Normalizing S to obtain S′, forming a matrix T
f
=(t
f1
,t
f2
,t
f3
,t
f4
,t
f5
) from the first as rival times obtained by various approaches, and finally we have the first arrival time
t
f
=T
f
·S
′t
(5) Repeating steps (2)-(4) until all the tracks having been detected.
The max error of this approach is 0.6 ms and its mean square error is 0.34 ms.
Inflexion approach (differential approach): There is always a point of max variation, referred to in the Method and Apparatus for Determining the Blaster's Detonation Time and the First arrival time, as point of inflexion, between the arrival time of the direct wave and the jumping of the waveform to the first Extremum point. The tangent at the inflexion paint intersects the time axis at to, and to is defined as the first arrival time of the direct wave.
The time obtained by this approach will be greater than the actual time, the max error is 2.2 ms and its mean square error is 1.09 ms, while the error of this approach is relatively high, the calculation is simple and also applicable to single track record.
Correlation approach (Adjacent tracks correlation): The initial time of the first arrival of the direct wave of a recording track is determined first using the “inflexion approach” or other approaches, then it is correlated with an adjacent track in a temporal window of the direct wave, the time difference &tgr;
0
between the first arrival time of the two tracks is obtained. Having known the first arrival time tx of the reference recording track, the first arrival time of the track to be obtained ty=tx+&tgr;
0
The max error of the time obtained by this approach is 1.2 ms, and its mean square error is 0.58 ms. If there is a relatively high error of the first arrival time tx of the reference recording track, the actual error will be increased.
Extremum approach of the correlation between the seismic focus signal and recording track:
The controllable seismic focus material is the result of one type of correlation, the Extremum point of which reflects the arrival time of the direct wave, therefore, the first arrival time can be determined by finding the maximum value (peak) or minimum value (valley) of the recordings.
The max error of time obtained by this approach is 1.2 ms, and its mean square root error is 0.63 ms.
First arrival-to-first arrival approach, peak(valley)-to-peak(valley) approach:
These two approaches can be used when pulsed seismic sources (e.g., air-gun, spark) are used and monitoring detectors are placed in the vicinity of the seismic source.
The
Liu Xiaoxi
Peng Shulin
Wang Lixin
Zhao Weiwei
Barlow John
China Petroleum & Chemical Corporation
Le Toan M
Pennie & Edmonds LLP
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