DHAHRAN: Saudi Aramco project teams from the Oil and Gas Upstream Pipelines Division and the Offshore Projects Division working at Berri Offshore Oil Field and Abu Ali Island recently accomplished two environmentally significant operations.
The first was the completion of Saudi Aramco's longest underground pipeline sections installed using horizontal directional drilling (HDD) methods. The 3,200-meter sections of 24-inch crude pipeline and 30-inch water-injection pipeline were installed as much as 32 meters beneath the seabed between Abu Ali Island and the end of Berri Causeway, using state-of-the-art drilling equipment.
The other major accomplishment was the first use by Saudi Aramco of HDD technology in the installation of a pipeline running from the shoreline into the sea. The 30-inch water-injection pipeline contained an underground section that stretched from the edge of Abu Ali Island to an exit point more than 1,500 meters into the Berri offshore oil field.
HDD has a significant advantage over conventional practices in that it avoids the environmental impact associated with dredging. That was an important factor at Berri and Abu Ali Island because of the sensitive nature of the local marine environment, where several endangered species of coral are found.
HDD also had the added cost advantage over dredging at Berri due to shallow local seabed conditions. Extensive access dredging would have been required just to reach the pipeline dredging zone. The use of HDD for this particular application saved Saudi Aramco approximately $54 million.
HDD is a sophisticated engineering technique that enables the laying of underground sections of pipeline without the need to trench or dredge the pipe route. The first stage of the process involves drilling a pilot hole between two ground entry points. Electronic positioning/steering instrumentation is used to guide the drill head along the specified path. Once the pilot hole is completed, a series of reaming passes are made using progressively larger tools to expand the hole to the required size. The final stage involves pulling the new pipeline through the newly formed tunnel.
The HDD work at Berri and Abu Ali was undertaken by Drilltec and Digital Connection Co. Ltd. through main contractors Global Al-Rushaid Offshore Co. Ltd. and Al-Robaya Est.
By Siraj Wahab
© Arab News 2009
