倾斜层状TI介质反射波旅行时快速计算  

Rapid calculation of reflected wave travel time in layered TI media with dipping interfaces

作　　者：张建中[1] 安全[1] 于建明 陈龙 ZHANG Jianzhong;AN Quan;YU Jianming;CHEN Long(Inner Mongolia Autonomous Region Seismolo-gical Bureau,Hohhot,Inner Mongolia 010080,China;New Resources Geophysical Exploration Division,BGP Inc.,CNPC,Zhuozhou,Hebei 072751,China)

机构地区：[1]内蒙古自治区地震局,内蒙古呼和浩特010080 [2]东方地球物理公司新兴物探开发处,河北涿州072751

出　　处：《石油地球物理勘探》2022年第1期111-117,I0005,共8页Oil Geophysical Prospecting

基　　金：中国地震科学台阵探测—华北地区东部专项“内蒙古巴林左旗—科尔沁左翼后旗区域野外观测”(DQJB17A0102);中部专项“呼和浩特附近地区野外观测”(DQJB16A0302)联合资助。

摘　　要：以推导出的单层倾斜TI介质反射波NMO(Normal Moveout)速度面解析解计算倾斜层状介质等效NMO速度为基础,利用常规排列(最大排列长度与反射深度比接近1)下CMP(Common Middle Point)时距关系实现了CMP及CSP(Common Shot Point)道集反射波旅行时的快速计算。该方法仅需通过法向入射原理追踪一条零炮检距射线,并运用Grechka给出的Dix平均算法由NMO速度面解析解获取等效NMO速度椭圆(涵盖了全方位的NMO速度),因此计算效率比通常多方位角、多炮检距的射线追踪方法高几个数量级,适用于TI介质旅行时反演。数值实验结果表明:等效NMO速度的计算结果与常规排列下最优拟合射线追踪计算旅行时得到的NMO速度相比,相对误差在10^(-3)数量级;而由等效NMO速度运用CMP时距关系计算的旅行时与射线追踪计算旅行时相比,相对误差在10^(-4)~10^(-3)数量级。说明该方法具有较高的计算精度,适用于不太复杂的介质结构和常规排列,可推广到具有光滑弯曲界面的层状各向异性模型。On the basis of calculating effective normal moveout(NMO)velocity of layered media with dipping interfaces using the derived analytic solution of NMO-velocity surface of the reflected wave in single-layer TI media with a dipping interface,rapidly calculating the travel time of reflected waves from common middle point(CMP)and common shot point(CSP)gathers is realized with the travel time-distance relation of CMP under conventional spread(the ratio of the maximum spread length to the reflection depth is close to 1).This method only needs to trace one zero-offset ray in line with the normal incidence theory and achieve an effective NMO velocity ellipse(encompassing all-around NMO velocities)with the Dix average algorithm proposed by Grechka and the analytic solution of NMO-velocity surface.Thus,it has a calculation efficiency of several orders of magnitude higher than multi-azimuth,multi-offset ray tracing,suitable for travel time inversion in TI media.Numerical tests show that the relative error between the effective NMO velocity and the NMO velocity when the travel time is calculated by ray tracing of optimal fitting under the conventional spread is in the magnitude of 10^(-3),while the relative error between the travel time calculated from the travel time-distance relation of CMP with effective NMO velocity and the travel time obtained by ray tracing is in the magnitude of 10^(-4)~10^(-3).In short,the method has high calculation accuracy and is suitable for the media without too complex structures and conventional spread.It can be extended to layered anisotropic models with smooth curved interfaces.

关 键 词：TI介质 常规排列 NMO(Normal Moveout)速度面 等效NMO速度 反射时距关系 

分 类 号：P631[天文地球—地质矿产勘探]