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本文介绍了为深穿透力或高分辨率的地震勘探所研制的一种新的气枪组合震源。这种气枪组合由21支气枪组成,总体积为4,165立方英寸,其操作压力为2,000磅/平方英寸。气枪组合的沉放深度为5至10米,校准检波器放置在震源正下方100米处,以此来记录远场信号。信号为数字记录,采样间隔1毫秒,所用的预采样滤波器的高频截止为124赫,衰减率为72分贝/倍频程。记录到的信号的峰间振幅为49.5巴-米;一次波与气泡的峰间振幅之比为16.7。信号频带(在6分贝点之间测量的)范围是9.5至90赫。从记录道的远场信号中减去拖缆至水面的双程旅行时,便可得出各种拖缆深度对信号的影响。通过对导出的远场信号及其振幅谱的研究,我们可以看到,在进行高分辨率地震勘探时,气枪组合和检波器拖缆都应放置在较浅的深度(5—8米上)。当作深穿透力地震勘探时,低频带中的信号能量十分有用,气枪组合和检波器拖缆应放置在中等深度上(8—12米)。远场信号测试指出,将一个大气枪(1,645立方英寸)加到气枪组合上,在0—90赫的频带内信号能量都有所增加。并将一次波与气泡间的峰值振幅比由11.8改进到16.7。两张地震剖面的比较说明了大气枪可以改善分辨率和穿透力。
This article describes a new combination of airgun sources developed for deep penetration or high resolution seismic exploration. The airsoft gun assembly consists of 21 air guns with a total volume of 4,165 cubic inches and an operating pressure of 2,000 pounds per square inch. Airsoft gun combination depth of 5 to 10 meters, the calibration geophone placed in the 100 meters just below the source, in order to record far-field signals. The signal is digitally recorded at a sampling interval of 1 millisecond and the high-frequency cut-off of the pre-sampling filter used is 124 Hz with a decay rate of 72 dB / octave. The peak-to-peak amplitude of the recorded signal was 49.5 bar-meters; the ratio of the first-order wave to the peak amplitude of the bubble was 16.7. The signal band (measured between 6 dB points) is in the range of 9.5 to 90 Hz. When subtracting the two-way travel of the streamer from the far-field signal of the track to the surface of the water, the effect of various streamer depths on the signal can be derived. By studying the derived far-field signal and its amplitude spectrum, we can see that the air gun assembly and detector streamers should be placed at shallower depth (5-8 m) for high-resolution seismic exploration. . For deep penetrating seismic surveys, the signal energy in the low frequency band is useful, and the airgun assembly and geophone streamers should be placed at medium depth (8-12 m). The far field signal test noted that adding an air gun (1,645 cubic inches) to the airgun assembly increased the signal energy in the 0-90 Hz band. The peak amplitude ratio between primary and bubble was improved from 11.8 to 16.7. The comparison of two seismic profiles shows that the air gun can improve resolution and penetration.