六种岩性海底地震波透射能量AVA特征研究  

A research on AVA characteristics of seismic transmission energy at seafloor of six lithologies

作　　者：杨正华[1] 朱光明[1] 袁伟[1] 

机构地区：[1]长安大学地测学院地球物理系,陕西西安710054

出　　处：《石油地球物理勘探》2011年第4期501-505,667+491,共5页Oil Geophysical Prospecting

摘　　要：海上地震勘探中的海底透射波能量分布特征影响勘探方案设计和数据处理。针对此问题，基于流…固界面反射和透射系数及能量方程等理论，探讨了淤泥、凝灾岩、粉砂岩、粗砂岩、石灰岩和花岗岩等六种岩性海底的透射波能量随入射角的变化特征。研究结果表明，随着入射角变化，不同岩性海底的透射波能量分布差异很大：①淤泥，小于临界角（49。）时有利于透射纵波勘探，大于临界角时有利于透射转换波勘探；②凝灰岩，入射角≤65。时有利于透射纵波勘探，入射角在40。～80。范围时，有利于透射转换波勘探；③粉砂岩和粗砂岩，在小于临界角（分别为61°～55。）时，有利于透射纵波勘探；④石灰岩和花岗岩，透射纵波能量在小于第一l临界角（分别约为14。和18。）时为l0％～30％；透射横波在第一临界角（同上）和第二临界角（分别约为28。和34。）之间约为40％，大干第二临界角后透射波消失，故此类岩性不利于海上勘探。Energy distribution of transmitted compression wave at seafloor has an influence upon exploration scheme design and data processing.As for this issue,this paper discusses variation characteristics of transmitted wave energy of 6 types of seafloor with different lithologies(silt,tuff,powder-grained sandstone,coarse-grained sandstone,limestone and granite) with respect to the incident angle,which is based on theories like coefficients of liquid-solid interface and energy function.The situations of transmitted wave energy distribution turn out with great differences in terms of different seafloors and the same conditions of acquisition: 1) For sea-floor of silt,it is beneficial for transmitted compression wave exploration when incident angle does not go over the critical angle(49°),otherwise transmitted converted-wave exploration is more effective.2) For sea-floor of tuff,it is beneficial for transmitted compression wave exploration when incident angle is not bigger than 65°,while transmitted converted-wave exploration is more effective when incident angle is between 40° and 80°.3) For sea-floor of powder-grained sandstone and coarse-grained sandstone,it is beneficial for transmitted compression wave exploration when incident angle does not go over the critical angle(powder-grained sandstone 61°,coarse-grained sandstone 55°).4) For sea-floor of limestone and granite,10%~30% of the energy is distributed to transmitted compression wave when incident angle is smaller than the first critical angle(limestone 14°,granite 18°),while transmitted converted wave takes nearly 40% of the energy when incident angle is between the first and the second critical angle(limestone 28°,granite 34°).The transmitted wave disappears after the second critical angle.This type of seafloor is not beneficial for exploration.

关 键 词：AVA地震勘探 海底岩性 临界角 流一固界面 地震波能量 

分 类 号：P631[天文地球—地质矿产勘探]