IGB pipeline successfully crosses Studen Kladenets dam

A great engineering feat, IGB's second horizontal directional drilling is now in the top five longest gas pipeline installations of this diameter executed to date in the EU, Report informs, citing the website of Interconnector Greece-Bulgaria(IGB).

The interconnector Greece-Bulgaria successfully crossed Studen Kladenets dam in Bulgaria, marking the most critical and challenging construction milestone so far.

With a total length of 1 440 m and a 32-inch diameter, this horizontal directional drilling (HDD) is now ranked among the top five longest gas pipeline installations of this diameter executed in the EU, where the ranking is headed by the crossing of Axios River for the TAP project in Greece.

The HDD under Studen Kladenets began shortly after successfully completing the first crossing under Maritsa River (422 m). The complex activity was expected to take 150 days, but thanks to the solid expertise of the field teams, the subcontractor HDI and the excellent organization on-site, the drilling was completed in less than two months.

The timeframe for this activity was of utmost importance not only for the timely completion of the IGB pipeline but also for the limited environmental window requirement, prohibiting construction activities during the nesting season of birds and other protected species in the region. This pushed the schedule up against a tight frame for completing it prior to the wet autumn and hostile, cold winter months.

After extensive preparation activities on site, the pilot drill started in the first week of August. It took the drill head a week of continuous work to reach the exit point at the south side of the dam and another four weeks to achieve the required diameter according to the detailed design.

The final pullback was completed in the afternoon of September 9th, 2021, during a 12h record operation involving a team of more than 30 people working around the clock to pull the pipe under Studen Kladenetz dam successfully.

Although technically more challenging, the HDD method was selected as the only feasible approach for the IGB pipeline.

The IGB is intended for export to Bulgaria of natural gas produced within the full-field development of Shah Deniz gas-condensate field or Shah Deniz Stage 2 (SD2) in the Azerbaijani sector of the Caspian Sea. The interconnector will be linked to the TAP. Through IGB, Bulgaria will receive 1 billion cubic meters of Azerbaijani gas per year.

State-owned Bulgargaz EAD signed a contract with the Shah Deniz consortium to purchase 1 billion cubic meters of gas from the Shah Deniz-2 field. Azerbaijani gas will cover 25-30% of Bulgaria's natural gas needs. The length of the interconnector is 182 km, of which 150 km runs through the Bulgarian territory. The annual capacity of the interconnector is about 3-5 billion cubic meters.