Multiscale Modeling of Electromagnetic Telemetry in Layered Transverse Isotropic Formation

Electromagnetic telemetry (EMT) systems are utilized for measurement while drilling to transmit data from borehole to the ground surface during drilling or vice versa. To help predict the successful deployment of the EMT system within complex formation and environmental noise, a reliable numerical algorithm is developed and applied to model the EMT system for directional drilling in layered transverse isotropic (TI) formation. In the telemetry system, the long and thin drill string having three-dimensional trajectory acts as an underground antenna that can be modeled as a thin wire excited by a delta gap voltage/current source near the drill bit. Using the thin wire assumption, the developed algorithm calculates the thin wire kernel in homogeneous uniaxial media with high accuracy to reduce the dimension and complexity of the problem. The mixed-potential form of layered media Green's function and electric field integral equation are used to model the electromagnetic interaction of the drill string and layered TI media. The effect of drilling fluid outside the pipe is modeled using the volumetric equivalence principle. The accuracy and efficiency of the new algorithm are demonstrated by several numerical examples.