摘要
地下地层普遍存在各向异性,忽略介质各向异性会导致速度估计不准确,成像精度下降.基于二阶声波方程的最小二乘逆时偏移忽略了介质各向异性及密度变化的影响,致使模拟地震数据与实际观测数据不匹配,影响收敛速度和反演成像质量.VTI介质一阶速度-应力方程能较好适应各向异性变密度情况,为此,本文首先从VTI介质一阶速度-应力方程出发,进行波动方程线性化;其次推导了相应的扰动方程和伴随方程,并通过伴随状态法得到梯度更新公式;最终形成基于一阶方程的LSRTM算法理论及实现流程.在实现算法的基础上,通过数值试算及成像结果对比,验证了本文算法在处理变密度和VTI介质时的有效性和优越性.偏移速度以及各向异性Thomsen参数误差的敏感性测试及误差收敛曲线对比结果进一步表明:速度及Thomsen参数对成像结果存在明显影响,其中速度敏感性最强,参数epsilon次之,参数delta的敏感性最弱.
Subsurface formation is generally anisotropic,which can affect the kinematic characteristics of seismic waves.Ignoring this feature will result in inaccurate velocity estimation,thus lowering the imaging resolution of target regions.The conventional least-squares reverse time migration (LSRTM) algorithm based on the second-order equation ignores the influence of anisotropy and density,thus resulting in mismatch of the simulated and observed seismic data,affecting convergent speed and imaging quality.To make improvement on this issue,this work proposes a new LSRTM algorithm based on the first-order velocity-stress equation in VTI media.First we linearize the wave equations from velocity-stress equation.Then we derive the corresponding perturbation equations and adjoint equations and obtain the updated gradient formula using the adjoint-state method.Finally,the framework and implementation process of the LSRTM method based on first-order velocity-stress equations are formed.We demonstrate the validity this new algorithm by numerical tests.Amount of the sensitivity tests indicate that velocity and Thomsen parameters have obvious influence on the imaging results,in which the velocity sensitivity is highest,next the parameter epsilon,and delta sensitivity is the least.
作者
郭旭
黄建平
李振春
黄金强
李庆洋
朱峰
刘梦丽
GUO Xu;HUANG JianPing;LI ZhenChun;HUANG JinQiang;LI QingYang;ZHU Feng;LIU MengLi(School of Geosciences,China University of Petroleum (East China),Qingdao Shandong 266580,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao Shandong 266071,China;Guizhou University Resource and Environmental Engineering College,Guiyang Guizhou 550025,China;Sinopec Geophysical Prospecting Institute of Zhongyuan,Puyang Henan 457001,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第6期2188-2202,共15页
Chinese Journal of Geophysics
基金
中国科学院战略性先导科技专项(A)(XDA14010303)
国家自然基金重点项目(41720104006)
国家油气重大专项(2016ZX05002-005-07HZ,2016ZX05014-001-008HZ)
山东省创新工程(2017CXGC1602)
山东省青岛市科技计划项目(16-5-1-40-jch)
自主创新科研计划项目(理工科)(17CX05011)联合资助
