Logging while drilling electromagnetic wave responses in inclined bedding formation

Abstract For real-time inversion and fast reconstruction of formation true resistivity, the forward modeling of electromagnetic wave logging while drilling is usually based on the transversely isotropic formation model with vertical symmetry axis (VTI medium), but it only considers the horizontal and vertical resistivity. It has certain limitation during practical application. This paper presents a forward calculation method of electromagnetic wave logging while drilling in transversely isotropic (TTI) strata with inclined symmetry axis based on the Dyadic Green's function. Anisotropic angle and azimuth are used to characterize TTI formation. The proposed algorithm is verified by numerical examples, the half-space electromagnetic wave reflection and transmission characteristics with different media are analyzed, and the necessity to use the new algorithm is pointed out. Numerical simulation also shows that there exist a critical borehole dip and critical anisotropic angle in TTI formation. Electromagnetic wave logging while drilling responses follows opposite rule before and after these two critical angles. Besides, the “horns” at the interface are not only related to well deviation, resistivity contrast, but also related to anisotropic angle and anisotropic azimuth.