Numaligarh Refinery Limited (NRL) has executed one of the longest Horizontal Directional Drilling (HDD) in Subansiri River, connecting Lakhimpur and Majuli in Assam, for its crude oil pipeline project. NRL is executing the mega project of laying 1,635km pipeline from Paradip Port in Odisha to Numaligarh in Assam along with expansion of its refinery from 3.0 MMTPA to 9.0 MMTPA, as part of ‘Numaligarh Refinery Expansion Project (NREP)’, an official release said here on Friday.
HDD is a construction technique whereby a tunnel is drilled under a waterway or other designated area, and a pipeline is pulled through it.
The NREP project is the single largest investment in Northeast India as part of the Centre’s ‘Hydrocarbon Vision 2030 for North East India’.
The pipeline passes through five states and crosses major rivers in East India, including the Ganga, Jia Bharali, Subansiri, and Brahmaputra through the HDD technique with intersections.
The Subansiri river, which connects Lakhimpur in the north and Majuli in the south, presented one of the most challenging HDD sites due to its complex 3,510-metre-long profile for a 26-inch diameter pipe.
The remote site made it more challenging due to non-accessibility of the area which remains flooded most of the year leaving a working window of 4-5 months during November to March.
To overcome these challenges, the executing agency constructed a temporary bridge over the Lohit River to facilitate the movement of heavy equipment and project accessories. Two giant rigs with a capacity of 500 MT were positioned on both sides of the river for drillings, reaming, and pulling activities.
The pulling of the 26-inch diameter pipe began on February 12 and continued non-stop for approximately 60 hours until the entire 3.51km-long pipe string was successfully pulled through. This marked the completion of one of the largest HDD projects globally for a 26-inch diameter pipe.
With the completion of this HDD, NRL is now focused on completing two more significant HDDs in the Ganga and Brahmaputra rivers within the next 2-3 months, the release said.
