Numerical modeling of electromagnetic wave logging while drilling in deviated well

Abstract

Electromagnetic wave logging-while-drilling (LWD) tools are used in geosteering for hydrocarbon exploration. Comparing with vertical wells, the response of logging has widely changed because the electrical parameters surrounding the borehole are non axisymmetrical distribution in deviated well. In this paper, with the method of alternating-direction-implicit finite difference time-domain (ADI-FDTD), we discuss the logging response of electromagnetic wave LWD in deviated well, three-dimensional Yee’s non-uniform staggered grid is used in cylindrical coordinates, transfer coordinate system is built between strata space and instrument space, which the conductivity tensor of the an isotropic and dipping formation can be expressed in coordinates of instrument, the method of area weighted average is used to compute the effective conductivity of partially-filled grid cells at interfaces, and uni axial perfectly matched layer (UPML) absorbing boundary conditions is used to truncate the computational domain. Result shows that horn of logging response curve is appeared on both upper and lower boundaries, when electromagnetic wave LWD tool penetrating through the boundary with large dipping angle, and this horn is used to indicate the presence of formation boundaries. What’s more, with the eccentric distance increases, horns effect of the boundary is more obvious.