Dual-pipe HDD systems for pilot bore drilling

摘要

Recent advances in directional downhole tooling for dual-pipe drilling systems extend their productivity into harder rock applications. Rotary downhole tooling can be changed out if productivity diminishes. Larger drill units have hollow inner drill strings that pass sufficient volumes of air to operate downhole hammers and clear cuttings from the borehole. Ability to rotate the bit while in the steering mode greatly improves air hammer productivity.