Application of Microtunnelling in Oil & Gas Projects for the Installation of Multiple Pipelines

This paper presents the design and execution of a complex river crossing project involving the microtunnelling installation of three hydrocarbon pipelines—16" NB, 14" NB, and 8" NB—beneath the Raidak-II River in the geologically intricate Dooars region of Eastern India. These hydrocarbon transportation pipelines own and operated by two National Oil companies viz. Oil India Limited and Indian Oil Corporation limited are critical to energy transportation in the region, with two of them operational for over seven decades. The project was initiated by Oil India Limited as part of a phased conversion of overground pipelines—previously suspended from railway bridges—to underground installations for enhanced safety and reliability. The project involved 5 no. of Microtunnelling in total at different river locations. The Dooars region, located at the foothills of the Eastern Himalayas and characterized by rolling plains, dense forests, and dynamic river systems, posed significant engineering and environmental challenges. While Horizontal Directional Drilling (HDD) and open- cut methods were employed in most locations for pipeline crossing along the route, geotechnical investigations revealed that HDD was unsuitable at certain sites due to subsurface conditions dominated by boulders, cobbles, and pebbles. Consequently, microtunnelling was adopted as an alternative solution. The project demanded meticulous planning, advanced hydrological and geotechnical assessments, and the use of innovative engineering techniques. Structural modelling using STAAD.Pro and ANSYS played a pivotal role in optimizing the tunnel and support system design, ensuring structural integrity and minimizing risk. A unique aspect of the project was the simultaneous installation of three pipelines within a single RCC casing, offering a cost-effective and space-efficient solution for bunched pipeline crossings beneath major water bodies. This paper details the design methodology, execution strategy, and site-specific engineering solutions adopted to overcome challenges such as pipeline alignment, shaft sinking in boulder-rich soils, spatial constraints for welding, and environmental disruptions. The successful completion of this microtunnelling operation underscores the viability of bundled pipeline installations in complex terrains and contributes valuable insights for future infrastructure projects in similar geographies.