FDTD Method And Its Application To Simulation Of Electromagnetic Well-Logging Tool Response

Forward simulation of electromagnetic well-logging tools in complex borehole environments is using of eccentric computational method to simulate the wave of electromagnetic traveling at known parameters of model stratum. At the same time, we can computate the responding of electromagnetic well-logging tools. In fact it is electromagnetic field estimation problems. The simulation of electromagnetic well-logging tools is a important foundation of the recover,the tools optimized designing are also based on the simulation resolutions. FDTD (Finite-difference Time-domain method) has been proven to be a highly efficient technique.Since the stratum model of electromagnetic well-logging is transverse, at the same time, the Electromagnetic LWD tool is also cylindrical,so we study FDTD in cylindrical coordinate. One of the greatest challenges of applying this technique is to open radiation problems, this has been the development of accurate and computationally efficient absorbing boundary conditions. Existing analytical absorbing boundary condition (ABC), such as Mur and Gedney's perfectly matched layer (PML). In this paper, numerical experiments are addressed for comparing two kinds of absorbing boundary conditions such as Mur and UPML, those comparisons show that the UPML technique works better than Mur ABC. An anisotropic-medium (unsplit) perfectly matched layer (UPML) formulation is presented for the truncation of FDTD lattices with general loosely and dispersive media. The numerical implementation of the PML is straightforward without any splitting of the fields, lowering computational costs. By a numerical example, it is showed that UPML performance is super than the general perfectly matched layer. Then, we infer out the expression of UPML-FDTD in cylindrical coordinates. In theory, we analyze the superiority of UPML-FDTD.Those studying works of FDTD in cylindrical coordinate are fully preparing for forward simulation of ELWD at the earlier period.