Abstract
Early detection of abnormal geological targets during drilling can enhance the safety of petroleum drilling. An impact source equipped with the advantage of long detection distances can recognize lithological interfaces. However, coda waves in the vibration waveform are significant to reflected waves, which are difficult to recognize in the time domain. This paper presents the design of an impact source that includes a hammer, impacted metal, Teflon, and a metal base. With the length and diameter of Teflon kept constant, the effect of the hammer, impacted metal, and metal base on the coda waves was experimentally investigated. According to the preferred metal materials, the effect of the length and diameter of Teflon on coda waves was also experimentally studied. A distance measurement experiment was implemented on 1.2 m sandstone on the basis of the preferred impact source design. The experimental results show that the coda waves are significantly attenuated by the preferred impact source. Moreover, the reflected waves are clearly identified in the time domain. Therefore, the preferred impact source can be used effectively in lithological interface detection.
Highlights
Many abnormal geological structures are encountered by the drill bit, such as fault zones, faults, and caves
Tunnel seismic wave detection technology consists of tunnel seismic prediction, tunnel seismic tomography, and small-offset seismic wave detection
Coda waves in the vibration waveform were significantly attenuated by the preferred impact source. is detection method can improve the resolution of seismic wave detection technology
Summary
On the basis of the preferred metal materials, the effect of Teflon length and diameter on coda waves was experimentally investigated. When the impacted metal is struck by the hammer as shown, vibrations are detected with the time-domain waveform and frequency spectrum shown in Figures 2(a) and 2(b). When the impacted metal is struck by a hammer as shown, vibrations are detected with the time-domain waveform and spectrum shown in Figures 2(c) and 2(d).
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