科研之友
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摘要
In this paper, a three-dimensional forward algorithm and simulation for the crosswell electromagnetic responses of the triaxial coils system in the transversely isotropic (TI) formation are presented. The transmit coils are simplified to the triaxial perpendicular magnetic dipole source firstly. To solve the problem of low convergence caused by low electromagnetic frequency, low induction number (LIN) preconditioner is applied to transform Maxwell equations to the Helmholtz equations. Conductivity volume weighted average, non-uniform Yee's grid and integral finite difference scheme are used to discrete the governing equations. Incomplete LU factorization preconditioning technique and bi-conjugate gradient stabilized method are applied to obtain the numerical solution of cross-well electromagnetic responses, and the numerical results given by the finite element software Comsol verify the validity of the proposed model and algorithm. The numerical results show that the lateral components xx and yy can reflect the formation anisotropy information in the vertical well model of TI formation, but its lateral detection ability is poor. Although the axial component zz only reflects the horizontal resistivity information, it has a good ability of lateral detection and is very sensitive to the anomalies in the formation. The cross components xz, zx have a strong ability to identify the boundary layer.
