利用侵入岩地震相变化特征识别断层

Fault identification with characteristics of seismic facies of intrusive rocks

苏北盆地高邮凹陷北斜坡侵入岩岩性为辉绿岩,辉绿岩与砂泥质围岩间通常存在明显的波阻抗差,在地震剖面上常表现为中低频、强振幅,连续性好的反射特征,导致侵入岩强反射干扰了围岩的反射,造成层位和断层识别困难,但利用其反射特征变化的信息仍可以识别断层。本文通过研究晚期侵入沉积地层的火成岩岩体变化模式和地震反射特征,结合地震正演模拟,建立了侵入岩地震相特征与断层关系的六种典型对应模式,即弯折相与倾向变化对应、错断相与岩体中断对应、陡倾相与断面侵入对应、变频相与厚度变化对应、分叉相与岩体分叉对应、终止相与岩体终止对应,利用该模式结合其他方法进行断层判别,提高了构造解释精度,并且在高邮凹陷北斜坡取得了很好的油气勘探效果。

Lithology of intrusive rocks is diabase in the northern slope of Gaoyou Depression,North Jiangsu Basin.There is difference of wave impedance between the diabase and the arenaceous pelitic wall-rock,which often shows low-medium frequency strong amplitude,and good continuity in seismic sections.These strong reflection characteristics of the intrusive rocks disturb reflections of wall-rock,and make horizon and fault identification more difficult.Based on igneous rock mass change pattern and seismic reflection characteristics of late invasion sedimentary strata and combining seismic forward modeling,this paper describes the six typical relationship modes between characteristics of seismic facies and faults of invasive rocks.These are: bucking facies vs dip angle change,fault facies vs rock mass break,steep facies vs fault plane invasion,frequency conversion facies vs thickness variation,forking facies vs rock mass fork,and ended facies vs rock mass end.We make use of these modes to identify faults combining with other methods.Results show enhanced structure interpretation and great potential for oil and gas exploration in the northern slope of Gaoyou Depression.