Parallel drilling method with source in separate borehole

摘要

A parallel drilling method comprises transmitting an azimuthally non-uniform electromagnetic signal from a source in an existing borehole 19 while a new borehole is drilled near the existing borehole. Azimuthally-sensitive measurements are collected by receive antennas in a drill string while drilling the new borehole and the drill string 8 steered along a path 18 at a substantially constant distance 48 from the existing borehole. The antenna may be a tilted antenna and the new borehole positioned vertically above the existing borehole. The technique may be used for the installation of a Steam-Assisted Gravity Drainage (SAGD) system.