Abstract

Horizontal Directional Drilling (HDD) is a trenchless construction technique used extensively in the installation of pipeline carrying hydrocarbons, water, sewage, cables etc., across obstructions where conventional trench and lay method or jacking-boring method cannot be suitably applied. HDD technique also minimises the impact of installation activities in densely populated and ecologically sensitive areas. HDD technique, however, has its inherent shortcomings which render it unsuitable in many real-world scenarios. The torque available at the mud-motor for driving and steering of the drill is fairly reduced for long length crossings. Also, maintaining the directional control of the drill bit becomes increasingly difficult for such long crossings. These shortcomings can be overcome using “Intersect Technique” by utilising electromagnetic steering technology for precise real-time tracking, wherein pilot holes are drilled from both ends using two separate drilling arrangements. On reaching the predefined intersection range, a virtual handshake between the drill bits is achieved. Thereafter, the primary rig continues the bore to the end of the design path to reach at the secondary rig side.

The present case study discusses at length the execution of HDD crossing of 18”- 2523 metre multi-product pipeline alongwith 6” CS conduit for OFC of M/s BPCL across the Thane-Vashi Creek in Mumbai, India. The length of the crossing combined with the presence of numerous pipelines of various operators made the execution of this pipeline crossing by “Intersection Technique” as the most suitable methodology. The pipeline was laid at an average depth of 15 m below the lowest creek bed level in geology which primarily included weathered basalt rock. The pilot hole for the crossing was completed utilising ParaTrack® drilling guidance and tracking system.

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