Memory-Efficient 3-D LWD Solver With the Flipped Total Field/Scattered Field-Based DGFD Method

This letter presents a fast and memory-efficient 3-D electromagnetic solver for logging-while-drilling (LWD) tools based on the flipped total field/scattered field-based discontinuous Galerkin frequency-domain (TF/SF DGFD) method. The new method inherits the Riemann transmission condition (RTC) with surface current sources from the mixed TF/SF DGFD method to couple nonconformal meshes as well as TF/SF solvers; it then extends to the moving-tool scenarios for the LWD application with a solver flipping technology and delivers a single global matrix of dramatically reduced dimension for all source positions, which can be solved directly on a normal-memory computer. By incorporating the tetrahedral/hexahedral mixed mesh and the curved domain decomposition method, the new solver is applied to two LWD cases and about 70% of unknowns can be saved for the flipped TF/SF DGFD remeshed regions.