摘要
基于三维时域有限差分算法,引入电导率张量构建控制方程,采用空间上后向差分、时间上中心差分进行离散,以电流密度的形式加入安培环路定理实现电流源的加载,通过轴向各向异性三维瞬变电磁正演研究地层电导率轴向各向异性对地-井瞬变电磁(BHTEM)三分量响应的影响规律。同时,与各向异性半空间模型一维解析解对比验证算法的准确性,然后建立各向异性三维模型并计算其回线源地-井瞬变电磁三分量响应特征。结果表明:在地表激发条件下,水平轴电导率各向异性对地-井瞬变电磁三分量响应的影响大于垂直轴电导率各向异性;x轴各向异性对?B_y/?t分量响应影响大于y轴各向异性,y轴各向异性对?B_x/?t分量响应影响大于x轴各向异性。研究成果为地-井瞬变电磁各向异性数据解释提供指导,也为地-井瞬变电磁各向异性反演奠定基础。
Based on the three-dimensional finite difference time domain algorithm,the conductivity tensor to construct the governing equation was introduced,the backward difference in space and the central difference in time for discretization were used,and the ampere loop theorem in the form of current density was added to realize the loading of current source.Finally,the influence of axial anisotropy of formation conductivity on borehole transient electromagnetic(BHTEM)three-component response was studied by axial anisotropic three-dimensional transient electromagnetic forward modeling.Meanwhile,compared with one-dimensional analytical solution of anisotropic half-space model,the accuracy of algorithm was verified.Then,an anisotropic three-dimensional model was established,and characteristics of borehole transient electromagnetic three-component response of the loop source were calculated.The results show that under the ground surface excitation condition,the horizontal axis conductivity anisotropy has greater influence on borehole transient electromagnetic three-component response than the vertical axis conductivity anisotropy;the x axis anisotropy has more influence on the∂B y/∂t response than the y axis anisotropy,the y axis anisotropy has more influence on∂B x/∂t response than x axis anisotropy.The results provide guidance for the interpretation of borehole transient electromagnetic anisotropy data and lay the foundation for borehole transient electromagnetic anisotropy inversion.
作者
郭建磊
姜涛
郭恒
宁辉
刘航
GUO Jian-lei;JIANG Tao;GUO Heng;NING Hui;LIU Hang(CCTEG Xi an Research Institute,Xi an 710077,Shaanxi,China;Integrated Geophysical Simulation Lab(Key Laboratory of Chinese Geophysical Society),Chang an University,Xi an 710054,Shaanxi,China)
出处
《地球科学与环境学报》
CAS
北大核心
2020年第6期737-748,共12页
Journal of Earth Sciences and Environment
基金
陕西省自然科学基础研究计划项目(2020JQ-994)
国家自然科学基金项目(41974162)
中煤科工集团西安研究院有限公司科技创新项目(2019XAYMS30)。
关键词
地-井瞬变电磁法
时域有限差分
三维
正演模拟
电导率
轴向
各向异性
三分量
borehole transient electromagnetic method
finite difference time domain
three-dimension
forward modeling
conductivity
axial
anisotropy
three-component
