Physics of Directional Electromagnetic Propagation Measurements‐While‐Drilling and Its Application to Forecasting Formation Boundaries

Abstract

The amplitude-attenuation and phase-shift of directional electromagnetic propagation measurementswhile-drilling are computed via the magnetic-current-source dyadic Green's functions for horizontally stratified anisotropic media. The detection range and the sensitivity to formation boundaries of directional electromagnetic measurements are analyzed. The influence of anisotropy, formation dip angle, and receiver antenna's tilting angle on directional measurements is studied. The results show that the directional detection range will increase with decreasing frequency, increasing coil spacing and increasing resistivity contrast between the target bed and shoulder bed. The change of directional amplitude-attenuation will become more obvious with increasing receiver antenna's tilting angle when the tool is approaching the formation boundary, and thus the sensitivity to formation boundaries will increase. The introduction of symmetrical antenna configuration can remove the dependence of directional signal on anisotropy and formation dip angle at locations far away from formation boundaries, and thus the formation boundaries can be accurately forecasted.

Coil optimization of ultra-deep azimuthal electromagnetic resistivity logging while drilling tool based on numerical simulation

“…Traditional EM resistivity LWD tools use axial coils and the measurement results are superposition of the resistivity of the formation around the borehole, without the ability of azimuthal resistivity detection (Wei et al 2010). To improve the tool's capability, the novel tool adds an inclined coil and a radial coil to the traditional axial coil, which is able to distinguish the direction.…”

Detection performance and inversion processing of logging-while-drilling extra-deep azimuthal resistivity measurements

“…Geosteering is one of the key techniques for the exploration and development of complex oil/gas reservoirs (Li et al 2005;Wei et al 2010;Bittar and Aki 2015). The kernel of this technique lies in the capability of detecting remote geological geometries which can be up to several meters away from the borehole (Wang et al 2016;Yang et al 2016;Wu et al 2017).…”