FTEM modeling of 3D random fracture based on FDTD

Homogeneous abnormal body model could not accurately describe irregular change of conductivity underground. The replacement of abnormal body model by random medium makes the conductivity closer to the actual conductivity distribution. Considering the characteristics of fracture in the real geological structure, we used Von Karman function to establish 3D random fracture model, and improved it through parameter optimization in the discussion of Hurst number and autocorrelation length. We modeled streak fracture by using 1D Fourier transform and background rock by 3D Fourier in order to describe the fracture characteristics of hydrocarbon reservoir. FTEM modeling with loop sources of 3D random fracture was realized based on FDTD. The numerical integration method was used for a homogeneous half-space to verify the validity of our algorithm on Fixed-wing Time-Domain Electromagnetic. We analyzed the electromagnetic response characteristics of random fracture and homogeneous fracture. The results showed that fracture model could precisely describe the distribution features of underground medium. Trend, inclination and position of fracture could be more clearly described by perpendicular electromagnetic response to fracture, which provided theoretical guidance for structure detection of random fracture. This method can be applied to other numerical simulation methods similarly.