From the magazine, HDD

Coe achieves river crossing record

Horizontal directional drilling (HDD) specialists Coe Drilling and Mears Group recently completed six major river crossings for a 60 km, 760 mm gas transmission pipeline constructed in Bangladesh.

With a population of approximately 155 million, Bangladesh is a rapidly developing country with increasing energy consumption. Construction is underway on many gas fired power plants across the country, including the Siddhirganj 2×150 MW peaking plant, 2×120 MW peaking plant, 210 MW thermal plant, the Haripur 360 MW plant, and the Meghnaghat 450 MW phase 2, 3 and 4 plants.

To service these plants, a new 60 km, 760 mm gas transmission pipeline – the Siddhirganj Gas Transmission Pipeline Project – has been constructed in the Bakhrabad gas field, in the Comilla District of Bangladesh.

The pipeline will facilitate reliable gas supply to industrial, commercial and other consumers in the Narayanganj area. The pipeline will also be the initial source for extending gas services to the southern provinces of Bangladesh.

Fernas Insaat A.S. was contracted by the project owner, Gas Transmission Company Limited to complete the pipeline. Fernas subcontracted the HDD crossings to Mears.

HDD river crossings

The pipeline route featured six river crossings, including at the Gomti River (1,992 m), Kajla River (850 m), Meghna River (1,650 m), Asariar Char River (750 m), Old Brahmaputra River (550 m), and Shitalakhya River (550 m). At each river crossing location, the HDD installations encompassed a bundle of a 760 mm API 5Lx70 coated steel pipeline together with a 150 mm steel pipeline that will house fibre optic communication cables.

The work was completed in two seasons with up to three drilling spreads working simultaneously on the project, including Mears’ 400 tonne capacity AA-880 rig. The difficulties of working in remote areas combined with complex logistics and monsoon rains were managed proficiently by the international project team. HDD equipment and personnel were mobilised from Australia, the US and India to work on the project.

The crossings were in sedimentary soils. Pilot hole drilling was accomplished using a 310 mm bit and magnetic steering tool systems. The crossings were pre-reamed in stages to create a 1,220 mm diameter borehole. The pipeline pullback technique included using the 150 mm steel pipeline, which was connected to the 760 mm pipeline’s pulling head, as a fill line to transmit ballast water into the 760 mm pipeline as the installation progressed. This method of buoyancy control, which significantly reduced the pulling loads during the pipeline installation, was used at both of the longest crossings (at the Gomti River and the Meghna River). The Gomti crossing is currently the longest HDD crossing completed in Bangladesh.

The final crossing (the Meghna River) was successfully completed in February, allowing the critical pipeline connections to be completed so the pipeline will be able to be put in service to provide natural gas to the country’s ever expanding market.

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