【作者】 王鹏伟；

【导师】 王修田； 张训华；

【作者基本信息】 中国海洋大学 ， 地质工程， 2011， 硕士

【摘要】 多次波是声地层剖面中的主要干扰之一,其能量一般很强且分布广泛,往往会掩盖一次反射有效信号,若不对其进行有效压制,极易导致错误的地质解释。由于目前的声地层剖面探测主要采用单道采集方式,且采集频率很高,致使常规的多次波压制方法难以达到令人满意的效果。因此,若要在声地层剖面上进行多次波的压制处理,只能考虑在单道剖面上能够奏效的压制技术。但由于声地层剖面往往是一个具有一定偏移距的单道声波剖面,一般不能简单地将其等同于一个零偏移距的地震剖面而直接对多次波进行压制处理。本文对符合二维观测的水平界面与倾斜界面两类模型进行了较为详细的理论与实验分析,得出了具有指导意义的重要结论:①当地下反射界面为水平界面时,非零偏移距的全程n次多次波的旅行时与一次反射波的旅行时仍具有固定的比例关系,但其总是小于相应一次波旅行时的n倍;②当地下反射界面为倾斜界面时,非零偏移距的全程多次波的旅行时与一次反射波的旅行时不再具有固定的比例关系,因而其在时间域的视倾角也不再与一次反射波的视倾角成固定的比例关系;③非零偏移距与零偏移距全程多次波的时距差异,随偏移距的增大而增大,但随探测深度的增大而减小。在理论与实验分析的基础上,本文应用MBP软件系统对声地层剖面中的多次波进行了追踪、调整和分频压制处理。通过大量的实验,总结出了适合于声地层剖面多次波衰减的处理流程。处理结果表明:经多次波压制处理后的剖面质量明显改善,有效构造的连续性变好,相应资料的信噪比大大提高。此外,本文还探讨了适合于声地层剖面的整体处理流程。在对多次波进行压制的基础上,进一步通过偏移归位、主能量脉冲反褶积以及剖面能量均衡等处理,可获得更高质量的声地层剖面。更多还原

【Abstract】 As one of the main types of noises on the acoustic sub-bottom profile, the multiple can usually have strong energy, widely exist, and even conceal the primary wave from view. Without being attenuated effectively, it may lead to wrong geological interpretations.At present, the single-trace layout with high frequency sampling is the main data acquisition approach in the sub-bottom profile detection. This may lead to poor result by using the conventional multiple attenuation techniques. Therefore, only the techniques which can be effective on the single-trace profile should be considered instead. However, since that an acoustic sub-bottom profile is usually acquired with a source-receiver offset, it should hardly be identical to a zero-offset seismic section, and these techniques may not directly be used on the non-zero offset profile.Based upon the detailed theoretical and experimental analyses of the horizontal and dipping sub-interface models suitable for two-dimension observation with non-zero offset, the following important guidable conclusions are deduced:①For a horizontal sub-interface, there is still a fixed ratio between the travel time of the nth order long-path multiple and n times of that of the primary wave, and the former is always smaller than the later;②For a dipping interface, there is no longer a fixed ratio for the travel time. Therefore, the ratio of the apparent dip between the long-path multiple and the primary wave in the time domain is also no longer fixed;③The time-distance difference between the long-path multiple of non-zero offset and that of zero offset becomes greater as the offset gets longer, but smaller as the detective depth gets deeper.On the basis of theoretical and experimental analysis, the MBP processing software is used for multiple tracing and adjustment, and attenuation on a sub-bottom profile with different frequency range. A multiple attenuation flow which may be suitable for the acoustic sub-bottom profile is integrated based upon quite a number of experiments. The result after multiple suppressing shows the good quality of the profiles with significantly improved event continuity of primary waves and highly enhanced signal to noise ratio.In addition, a full flow which may be suitable for the total processing of acoustic sub-bottom profile is also discussed. After multiple attenuating, a much higher quality profile can be obtained by using further processing such as migration and main energy spiking deconvolution.更多还原