Drilling an S-curve below water for a new gas pipeline to the Isle of Sheppey

For the past 70 years, gas has been transported to the Isle of Sheppey by a gas pipeline built into the construction of the Kingsferry Bridge. This pipeline was constructed in the 1950s and is now at the end of its operational life.

Plans were made for the construction of a replacement pipeline that would cross the River Swale between the Isle of Sheppey and the mainland. This new pipeline would be installed with a horizontal directional drill, located south of the bridge.

A 577 m / 1893 ft HDD crossing below the river Swale was carried out by LMR Drilling UK Ltd. to install the new gas pipeline. The trajectory included an S-curve below the river, curving 9 degrees right and then 32 degrees left.

The pilot bore crossed the river at a depth of 17 m / 56 ft below the riverbed. Half the trajectory was located below the river. A reliable steering system was needed to accurately navigate along the curved trajectory through the stiff London Clay.

The Drillguide Gyro Steering Tool was the solution to the steering challenges of this pilot bore. The Drillguide GST does not require surface access, which makes it ideal for surveying challenging drill trajectories below inaccessible surfaces, as was the case here.

Brownline’s GPS track was used for additional surface tracking on opposite banks of the river and once more close to the exit point. The compact surface equipment allowed quick verifications of the measured drill head position. This combination of measurement techniques reduced the chance of errors, thereby increasing the safety for the HDD project.

Pressure-While-Drilling was also used on this river crossing project. Real-time pressure measurements made it possible to mitigate the risk of drilling fluid loss below the river and adjacent wetlands.

The innovative tools and expert guidance provided by Brownline helped make this HDD project a success.