HDD in India

World Record Parallel HDD Intersects in India 

Numaligarh Refinery Limited (NRL) is in the process of laying a 1,047-mile crude oil pipeline in northeastern India.

The pipeline is proposed to run from Paradip port on the Eastern coast, weaving its way along the Himalaya between Nepal and Bhutan before terminating at the Numaligarh refinery in Assam in far-eastern India.  

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The 26-in. carbon steel pipeline will enable expansion of the refinery from 3.0 million tons per annum to 9.0 million tons per annum as part of ‘Numaligarh Refinery Expansion Project’ (NREP). A parallel 6-in. steel accessory line will be installed for fiber-optic cables. 

The pipeline route crosses all the major rivers in Eastern India including the Ganges, Jia Bharali, Subansiri, and Brahmaputra via horizontal directional drilling. The longest of those crossings under the Ganges River was awarded to M/S Trenchless Engineering Services Pvt Ltd.  

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The installation of two parallel pipelines, each more than 13,000 ft in length, within a narrow right of way was a technical achievement made more difficult by the location as well as a limited weather window in which the crossing could be completed.  

The pipeline route crosses all the major rivers in Eastern India including the Ganges, Jia Bharali, Subansiri, and Brahmaputra.

“Since the location was prone to floods, we had a very small window to enter and execute,” says Vipin Gupta, managing director, Trenchless Engineering Services Pvt Ltd. Further, the location was five miles off the blacktop into a remote village. The road distance between the rig side and the pipe side was nearly 125 miles and in poor condition, often taking up to 16 hours for a single trip.   

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As a result, the work was performed in the dry season from January to May. The first pilot was commenced on Jan. 25, 2024, using two American Augers DD1100 rigs. The DD1100 is one of the largest rigs in the American Augers lineup with over 1 million pounds of push/pull capacity.  

Despite the immense power on hand, the crossings were designed to use the Intersect method rather than as a single push from entry to exit. Intersecting at a specific point in HDD is a technique often used for long or complex bore paths, especially when dealing with installations exceeding 7,000 ft.  

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Benefits of HDD Intersects  

Increased Accuracy: Intersecting allows for greater control and accuracy in the drilling process. By planning to meet at a designated midpoint or specific location, the drill path can be managed more precisely from both ends, which is crucial in long bores to ensure the paths meet accurately. 

Reduced Risk: Drilling from both ends toward a midpoint can help mitigate risks associated with long horizontal drills such as excessive torque, drag, and pipe sticking. It also allows for better management of potential issues like fluid pressures and borehole stability, since adjustments can be made from either end if problems are detected. 

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Equipment Limitations: HDD rigs have limitations in terms of the length of the drill pipe they can push or pull due to friction and the power of the rig. By intersecting from two sides, each rig only needs to cover half the distance, making very long crossings feasible without exceeding the capabilities of the drilling equipment. 

Geotechnical Considerations: The presence of cobbles, boulders, and other difficult geologies may limit the feasibility of HDD. The Intersect method enables the driving of conductor casing near surface while traversing these zones, then Intersecting during a tangent section to complete the pilot bore. 

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Project Execution 

Trenchless Engineering Services was contracted to install two separate pipelines within the 59-ft right of way. A primary 26-in. crude oil pipeline would be installed followed by a 6-in. accessory line installed in parallel, both via the HDD Intersect method with 20 ft of separation between them. Total designed crossing length was 13,213 ft at a maximum depth of 164 ft. 

The crossing was scheduled during the dry season, when river levels were low, allowing Trenchless Engineering Services to lay a series of ParaTrack Guide coils on surface, providing them with the speed and industry-leading accuracy of P2 AC Magnetic Tracking for more than ¾ of the total crossing distance.

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P2 Magnetic Tracking generates a powerful AC signal that can be detected at depths of more than 1,000 ft. This enabled the intersections to be made without the need for specialized intersect equipment, and ensured the two lines would remain exactly parallel for their entire 2.5 miles of length. 

The intersects were planned to occur on the northern Numaligarh side, after the river had been successfully crossed, at 6,660 ft of measured distance and 160 ft depth. 

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P2 AC Magnetic Tracking on surface limited the positional uncertainty of the pilot bores at intersect depth to under 3 ft – three times better than what would be achievable on surveys alone. This high degree of accuracy allowed the intersection to occur on the first attempt at the planned depth, with nearly zero misalignment between the opposing pilot bores.  

After successful intersection, the 12 ½-in. pilot was reamed in three stages to 20-, 30- and 38- for the final pass. “The crucial thing was to maintain fluid returns over nearly 2 ½ miles, so that cutting flow was maintained,” says Gupta. “Our engineering team designed special reamers for dual-sided pumping, easing the mud purging process and handling the loads efficiently. Using two 600 GPM pumps in tandem for reaming, achieving a flow rate of nearly 800 GPM, was crucial in speeding up the drilling process and managing the cuttings. Torque was limited to under 60,000 ft/lbs and the 26-in. pipeline was successfully pulled in on April 12, 2024 – ahead of schedule, and a world record for the distance at just 76 days.”  

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Completion of the parallel 6-in. accessory line was completed using the same techniques in just 10 additional days including pilot drilling, welding and pullback. 

With the success of this HDD, NRL is now focused on completing the remaining HDDs over the next several months, thereby completing all major HDD crossings of its 1,047-mile long Paradip Numaligarh Crude Oil Pipeline (PNCPL). NRL plans to accomplish construction and commissioning of the PNCPL project by mid-2025. 

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Jed Sheckler is director of marketing at Vector Magnetics LLC. 

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