The smaller 24 inch pipe was to be used as an oil trunk line and the larger 30 inch, with a total steel pipe weight of more than 1,500 tonnes, to serve as a water injection line. The project was reported to be the world’s longest undersea HDD crossing.

In November 2008, Middle East specialist HDD contractor Digital Connection Co Ltd of Al-Khobar, Kingdom of Saudi Arabia sought technical advice and assistance in the recovery of a 42 inch hole-opener that had become stuck along with the 3 km drill string beneath the seabed during a pre-ream pass on the second of two subsea pipeline crossings.

The Berri Causeway pipeline project in the Middle East was always seen as a big challenge. Both the length of the crossings and the dimensions of the pipeline, which would weigh more than 1,525 tonnes, were testing the boundaries.

While the first 24 inch oil pipeline had previously been successfully installed, unforeseen delays between the drilling process over a twelve week, non-working period had caused the drill string and the 42 inch hole-opener to become stuck on the second, 30 inch pipeline crossing and installation.

They had little time to provide a solution to releasing the 3 km stuck drill string and 42 inch hole-opener.

However, emergency discussions between TT-UK, the main contractor, and the local drilling contractor quickly led to a response. The company recommended using the Grundoram Taurus impacting hammer combined with steel pipe adaptations. The adaptations were designed and formulated to transfer dynamic impact performance energies through special steel fabrications adapted to the drill string via the Grundoram dynamic impacting hammer.

Sharing the project information with other TT Group offices in the USA and Germany, TT-UK drew up a strategic plan together with a technical proposal on how they believed the drill string could be freed up using dynamic impact vibration energy.

While similar successful undertakings had previously been carried out worldwide, few have been attempted for releasing stuck drill rods over such an exceptionally long distance, with each drill rod weighing 480 kg. Dynamic impact vibration energies have normally been placed on the end of product pipes for assistance in completing HDD (ram assist), or using HDD techniques for product pipe retrieval where the product pipe has become stuck. Few undertakings had previously attempted with stuck drill rods due to the enormous impact power that has to be contained onto a relatively small size drill rod (6/58th) from a large impacting hammer in a usable and controllable process.

The Project owner is Saudi Aramco. The main pipeline contractor is Al Robaya and the HDD subcontractors are DCL and TATCO. The combined efforts from all companies and the personal attendance on site of Roger Atherton of TT-UK proved invaluable to the success and final retrieval of this problematic drill bore taking TT’s Grundoram and pipe ramming technologies to a new level of HDD ram assist, pipe/drill stem rescue method. Following bore-hole salvage the 3 km, 30 inch water injection pipe-line was finally and successfully installed on 13 January 2009.

This rescue prevented significant financial implications such as the total cost of a lost drilled bore, any contractual penalties and ongoing cost delays in commissioning the final pipelines. Associated costs involved in planning a new bore and the actual costs of duplicating all the undertakings of a new bore/installation.