Cullen Bay Vibracore

In May 2016, Hagstrom Drilling travelled north to Darwin for an overwater geotechnical investigation. Hagstrom Drilling’s overwater experience and modern equipment were a key factor in being awarded the work.

We worked with the client to demonstrate the effectiveness of the Vibracore System in producing quality, undisturbed core sample without the need for use of conventional methods. A local marine contractor was engaged to supply a suitable vessel for the drilling operations.

We worked with the client to demonstrate the effectiveness of the Vibracore System in producing quality, undisturbed core sample without the need for use of conventional methods. A local marine contractor was engaged to supply a suitable vessel for the drilling operations.

SCOPE

19 vertical boreholes were required in the entrance to the Cullen Bay Marina Each borehole had to reach a depth of 4m below the seabed level and was to be surveyed to a high standard of accuracy. Hagstrom achieved accurate positioning using a HP DGPS system.

VIBRACORING SYSTEM

Vibracoring is suited to the rapid sampling of unconsolidated and semi-consolidated sediment sequences. Unlike conventional rotary drilling techniques, vibracoring uses a submersible, electrically powered, vibrating head attached to a rigid core barrel 3 or 6m in length (aluminium or stainless steel) that is driven into the seabed. Maximum depths of 6m can be achieved to recover continuous, undisturbed and in situ samples of the seabed.

The coring system consists of a core barrel attached to a relatively light (100 kg) vibrating head contained within a rigid frame complete with retractable legs. The hammer and core barrel rotate freely within the frame, which improves the capability of the core barrel to penetrate “difficult” substrate. The variable frequency (0 – 6000 Hz) capability of the vibrahammer enables optimum penetration of the substrate, whereby certain sediment types can be “matched” to certain frequencies. The vibrahammer is operated at the surface by a control panel, where the rotation direction and frequency can be adjusted.

OUTCOMES

The project requirements were met and completed within the anticipated timeframe, free from any lost time and injuries. It was a great opportunity for Hagstrom Drilling to demonstrate it’s diversity of services in drilling and marine investigations.