A modeling study of borehole radar for oil-field applications

This paper examines the suitability of borehole radar for near-wellbore imaging. The maximum imaging range is primarily determined by the conductivity of the formation in which the borehole lies and the reflectivity of the targets. Under similar medium contrast, formation interfaces result in much stronger reflections than fractures. Complex horizontal borehole geometries are modeled with a 3-D finite-difference time-domain (FDTD) code. Borehole effects, which are often almost insurmountable for acoustic methods, are very small for radar. As a result, the reflections in general are visually identifiable on the synthetic radar waveforms even before any signal processing. Therefore, borehole radar is a promising approach to map structures in the immediate vicinity of the borehole for a penetration depth of at least a few meters in relatively less-conductive reservoirs (e.g., <0.03 S/m). As such, it complements borehole acoustic methods and has potential for geosteering applications.