The 42 in. diameter BTC pipeline, expected to become operational in 2005 will be the main transportation route for Azeri crude oil to the world market. Following completion of construction of the BTC pipeline, crews will move onto the parallel 42 in. diameter SCP gas mainline works. The high standards of health, safety and environmental performance expected by the client and the finance company for the world-class project resulted in a commitment to achieve a major or “step change” improvement in health and safety performance by comparison with recent large onshore pipeline projects.
Stockton Pipelines, a fully owned subsidiary of McConnell Dowell Constructors (Aust) Pty Ltd was selected by CCCIC Dutco McConnell Dowell JV to perform seven directional drill crossings on the Azerbaijan section of the BTC and SCP. The crossings are between 500 and 1,000 metres for installation of the 42 in. API-5L Grade X70 tri-laminate coated pipe as well as the associated separate installations of DN150 steel pipe to house a fibre-optic cable. The drilling operation was performed with Stockton’s 250 tonne capacity HDD rig and included the drilling of a pilot hole using 5 1/2 in. diameter drill pipe with a jetting assembly. The crew used a magnetic guidance system (Paratrack 2) to steer the pilot hole under rivers and villages, through vertical curves of 1,200 to 1,500 metre radius and to a depth of up to 30 metres before using the back reaming process to progressively increase the hole size to 54 in. diameter, ready for pipe pull back.
Buoyancy control of the 42 in. pipe was required to reduce both frictional forces and the required pullback force during pipe installation. This was performed by the insertion of a 20 in. diameter HDPE pipe into the barrel of the 42 in. product pipe and filling the remaining annulus with water using a 6 in. diameter HDPE fill pipe which was gradually withdrawn during the pull back operation. For the 1,002 metre crossing beneath Qarabyork Village in Azerbaijan, this resulted in a maximum pull load of only 70 tonnes being required to install the BTC pipe. Drilling and pipe pulling operations in the generally silty clay and sand formations went exceptionally well, finishing in June 2004 and adding successful crossings of significant length and diameter to the Stockton Pipelines HDD job list.
Stockton Pipelines are currently relocating all their plant and equipment from the UK to Batam, Indonesia to increase their HDD support for the Australian and Southeast Asian operations of McConnell Dowell Constructors.