hp-Adaptive Multiphysics Finite Element Simulation of LWD Borehole Sonic Waveforms

SUMMARY We develop a new multi-physics, finite-element method to simulate LWD borehole acoustic waveforms in the presence of the tool. The method works in the frequency domain, is fully adaptive, and enables accurate simulations in the presence of large contrasts of elastic properties, including those existing along the tool body. Coupling of acoustic and elastic wave propagation in the borehole and the formation, respectively, is achieved with a new, stable multi-physics formulation. In addition, the method includes a PML layer for effective truncation of the spatial domain. Examples of application are shown for the simulation of LWD sonic waveforms acquired with monopole, dipole, and quadrupole sources. Results indicate accurate and reliable reproduction of tool, borehole, and formation propagation modes in the presence of hard and soft formations, including cases of transversely isotropic formations.