Numaligarh Refinery Limited (NRL) has achieved a significant milestone by completing one of the longest Horizontal Directional Drillings (HDD) in the Subansiri River, linking Lakhimpur and Majuli in Assam, for its crude oil pipeline project.
According to an official release, NRL is undertaking the ambitious project of laying a 1,635km pipeline from Paradip Port in Odisha to Numaligarh in Assam, alongside expanding its refinery from 3.0 MMTPA to 9.0 MMTPA, under the ‘Numaligarh Refinery Expansion Project (NREP)’.
HDD involves drilling a tunnel under a waterway or designated area, through which a pipeline is then pulled. This technique was employed for crossing the Subansiri river, a crucial link between Lakhimpur and Majuli.
The NREP project, part of the Centre’s ‘Hydrocarbon Vision 2030 for North East India’, is the largest investment in Northeast India. The pipeline traverses five states and crosses major rivers, including the Ganga, Jia Bharali, Subansiri, and Brahmaputra, utilizing the HDD technique at intersections.
The Subansiri river posed significant challenges due to its complex 3,510-meter-long profile for a 26-inch diameter pipe. Moreover, the remote and flood-prone site limited the working window to 4-5 months annually, from November to March.
To overcome these hurdles, a temporary bridge was constructed over the Lohit River to facilitate the movement of heavy equipment. Two 500 MT capacity rigs were positioned on both riverbanks for drilling, reaming, and pulling activities.
The pulling of the 26-inch diameter pipe commenced on February 12 and continued uninterrupted for approximately 60 hours until the entire 3.51km-long pipe string was successfully pulled through. This achievement marks one of the largest HDD projects globally for a 26-inch diameter pipe.
With this milestone reached, NRL is now focusing on completing two more significant HDDs in the Ganga and Brahmaputra rivers within the next 2-3 months, as per the release.
