单道地震资料处理方法研究及其在平潭海域的应用

发布时间：2018-10-26 06:35

【摘要】：海洋单道地震勘探以其配置灵活、简便高效的优势,在海洋区域地质调查、近海工程物探等领域得到了广泛的应用。数据采集时,激发震源和接收电缆拖曳于船后一定深度的海水中,调查船以一定速度沿设计的测线航行,震源按一定时间间隔激发,一次激发形成一个地震道,震源与检波器组中心点距离较短,得到的地震记录通常能够较为直观地反映地下地层结构。但由于海上单道地震记录存在着各种各样的干扰波,如多次波、虚反射、环境噪声等,这些干扰波都会或多或少地影响资料解释,因此必须了解干扰波的来源、形成机制及传播规律,研究单道地震资料处理方法,提高资料处理技术。本文对海洋地震勘探方法、海上单道地震勘探常用的电火花震源与接收电缆、海上单道地震记录中常见干扰波的形成机制进行了阐述,以平潭海域的实际调查资料为数据基础,首先利用地震记录中背景噪声与震源子波的频率特征差异进行滤波,然后利用直达波提取地震子波并进行相关滤波,通过对单道地震资料的分析、处理,提高地震剖面的信噪比和分辨率,最后利用钻孔沉积物分析结果对地震层序进行了划分,得到了以下几点认识:1)海洋地震勘探以调查船为载体,船舶及船载设备产生的噪声贯穿着整个地震勘探工作,不同船型、船速以及不同海域引起的背景噪声对地震记录的影响也有所不同。通过“只记录不激发”的采集方式获得地震勘探的背景噪声资料,并对其进行频谱分析,得出该工区地震记录背景噪声的频率范围在35~140Hz,而采用的电火花震源的有效频率范围在180~2000Hz,二者可在频域分开,故可以利用背景噪声与震源子波的频率特性差异来选择频域滤波参数,最大限度地保留有效信号。2)由于水体对地震波的吸收作用相对较弱,且直达波的传播距离相对较短、传播稳定、受污染少,原始地震记录中的直达波能量较强,波形形变较小,因此可以利用直达波提取地震子波。而由于海洋勘探环境的复杂多变性,利用直达波提取地震子波时首先需要消除随机因素的影响,可先利用相关法拾取各道的直达波,将各道提取的直达波进行叠加再平均,通过平均的手段消除随机因素的影响,最后以平均的结果作为提取的地震子波。3)提取的地震子波与反射波的相关性强,而与其它干扰波的相关性弱,因此可以利用提取的地震子波进行相关滤波,提高地震记录的信噪比。进行相关滤波时,相关子波长度不宜超过地震子波的延时。而相关滤波前对地震记录先进行带通滤波能够有效地克服低频水波干扰对相关处理的影响。地震资料解释通常需要结合地质钻孔、地球物理测井等资料。利用测线附近取得的钻孔沉积物样品的分析测试结果,对沉积层序进行划分,根据以往经验,沉积物声速设为1600m/s,将柱状样长度转换为地震波旅行时,与处理后的时间剖面进行对比,并结合反射同相轴的接触关系,识别出4个主要反射界面。
[Abstract]:The marine single-channel seismic exploration has the advantages of flexible, simple and effective configuration, and has been widely used in the fields of marine area geology survey, offshore engineering geophysical exploration and so on. When the data is collected, the excitation source and the receiving cable are towed in seawater at a certain depth after the ship is towed, the survey ship is sailing along the designed test line at a certain speed, the seismic source is excited at a certain time interval, a seismic channel is excited at one time, the distance between the seismic source and the center point of the detector group is shorter, The resulting seismic records can generally reflect the subsurface formations more visually. However, due to the existence of various kinds of interference waves, such as multiple wave, virtual reflection, environmental noise, etc., these interference waves will influence the interpretation of data more or less, so it is necessary to understand the source, formation mechanism and propagation law of the interference wave. To study the method of seismic data processing in single channel and to improve the data processing technology. In this paper, the formation mechanism of common interference waves in marine seismic exploration method, marine single channel seismic exploration, electric spark source and receiving cable, sea single channel seismic record is expounded, and the actual survey data in Pingtan sea area is the data base. firstly, filtering the difference between the background noise and the frequency characteristic of the seismic source sub-wave in the earthquake record, extracting the seismic sub-wave by using the direct wave and carrying out relevant filtering, analyzing and processing the single-channel seismic data, improving the signal-to-noise ratio and the resolution of the seismic section, Finally, the seismic layer sequence is divided by using borehole sediment analysis results, and the following points are obtained: 1) the noise generated by ship and ship loading equipment is penetrated through the whole seismic exploration work, different ship types, The influence of ship velocity and background noise caused by different sea areas on seismic records is also different. acquiring the background noise data of seismic exploration through the acquisition mode of the 鈥淩ecord non-excitation only鈥，

本文编号：2294864