摘要
地—井瞬变电磁法由于抗干扰能力强、响应信号明显等优势而应用广泛。在深部矿产资源调查和地质构造勘查等任务中,多个油气储存在层理发育的沉积岩地区大多数情况下表现为电各向异性,但是目前地—井瞬变电磁反演算法均基于各向同性模型,传统反演成像技术不再适用。为了分析地层电导率各向异性对地—井瞬变电磁勘探结果的影响,对各向异性介质模型研究其电磁响应特性。基于各向异性介质的电导率张量,提出了一种基于有限元方法的三维分析模型,采用PARDISO求解器进行求解。针对多个各向异性角度的情况模拟了各向异性介质的瞬变电磁响应,分析介质各向异性对电磁波传播规律的影响,探讨了各向异性瞬变电磁响应特征。研究结果表明:在垂直各向异性介质中,电磁波传播方向垂直于电导率最大的方向时,电磁响应变化最明显;电磁波传播方向平行于电导率最大的方向时,电磁响应变化最弱。在水平各向异性介质中,电磁波垂直于电导率最小的方向时,电磁响应变化最明显;电磁波平行于电导率最小的方向时,响应变化较弱。最后,针对地—井瞬变电磁方位测井,分析了发射源沿不同方向条件下各向异性地层和异常体模型的电磁响应,结果表明其瞬变电磁响应特征与发射源的方向有关,且对于主轴各向异性异常体,发射源方向的选择直接影响对异常体各向异性方向的判断。该研究结论对油气开发地球物理勘探方法的研究具有一定的参考价值。
The surface-borehole transient electromagnetic method(TEM)has been widely used because of its advantages such as high resistance to interference and strong response signals.In deep ore-prospecting and geological structure exploration,most oil and gas resources are stored in sedimentary rocks with obvious laminations,and the subsurface media exhibit anisotropic electrical conductivity.However,conventional inversion imaging techniques based on isotropic models are no longer applicable to the processing and interpretation of anisotropic data.To analyze the impact of conductivity anisotropy on the surface-borehole TEM,this paper studies electromagnetic responses in anisotropic media.According to the conductivity tensor of anisotropic media,this paper proposes a three-dimensional(3D)analysis model based on the finite element method(FEM),using the PARDISO solver to solve problems.The transient electromagnetic responses in anisotropic media with different angles are simulated to analyze the influence of anisotropic media on the propagation and reception of electromagnetic waves.The characteristics of the transient electromagnetic responses in anisotropic media are also discussed.The results show that in vertical anisotropic media when the propagation direction of the electromagnetic wave is perpendicular to the direction of maximum conductivity,the electromagnetic response is the strongest;when the propagation direction of the electromagnetic wave is parallel to the direction of maximum conductivity,the electromagnetic response is the weakest.In horizontal anisotropic media,the response of electromagnetic wave is the strongest when the electromagnetic wave is perpendicular to the direction of the minimum conductivity,and the weakest when the electromagnetic wave is parallel to the direction of the minimum conductivity.In addition,this paper analyzes the electromagnetic responses of anisotropic strata and anomalies with different emission source directions during transient electromagnetic logging.The results show that the transient electromagnetic responses of anisotropic strata and anomalies are related to the direction of the emission sources.Specifically,for the principal axis anisotropic anomalies,the choice of emission source directions directly affects the determination of the anisotropic direction of anomalies.The conclusions of this paper provide valuable insights for the research on geophysical methods in oil and gas development.
作者
李昊锦
毛玉蓉
王新宇
严良俊
周磊
LI Haojin;MAO Yurong;WANG Xinyu;YAN Liangjun;ZHOU Lei(College of Geophysics and Petroleum Resources,Yangtze University,Wuhan,Hubei 430100,China;Key Laboratory of Exploration Technologies for Oil and Gas Resources,Ministry of Education,Yangtze University,Wuhan,Hubei 430100,China;School of Geophysics and Geomatics,China University of Geosciences(Wuhan),Wuhan,Hubei 430074,China)
出处
《石油地球物理勘探》
EI
CSCD
北大核心
2024年第5期1184-1196,共13页
Oil Geophysical Prospecting
基金
国家自然科学基金项目“地/井时移电磁法在剩余油监测中的应用基础研究”(42374091)、“基于井地激电电磁法的储层流体识别方法研究”(42274103)和“水力压裂时域电磁监测方法研究与综合应用”(42030805)联合资助
关键词
电导率各向异性
有限元
电磁场三维正演
二阶后退欧拉差分法
conductivity anisotropy
finite element
forward modeling of 3D electromagnetic fields
second-order backward Eulerian difference method
