Case Study: Site Investigation

Mobilisation

On the 5th May 2004  Gardline Geosciences mobilised their Downhole CPT system on board M.V. Kingfisher at Falmouth docks in order to undertake a site investigation for Seacore at a proposed jack-up and storage facility in Dutch sector P10/P11 of the North Sea.
The mobilisation of the WISON APB system with heave-compensated drill spread was completed in 4 days and following dynamic positioning tests M.V. Kingfisher embarked for Rotterdam. 

Site Investigation

The site investigation started on 10th May with a scope of works comprising 18 boreholes to a maximum depth of 65m below sea-bed level (~95m below LAT).

Mudline CPTs were used to prove echo sounder readings and the first four continuous  piezocone (CPTU) tests were performed to 35m over a 48 hour period in calm weather conditions. Typically tip loads of 30-40 Mpa were encountered in the shallow holes with loads in excess of 65 Mpa below 40m depth.

Sampling

Composite sampling/CPT boreholes were completed using the WISON APB’s downhole 1m push sampler giving excellent recovery in all substrates (holocene sands and pleistocene alluvial sequences) up to a maximum push of 3 tonnes (the limit of the thin walled sample tubes). This high load is possible due to the use of a sample tube protection system used on the WISON APB.  Samples were processed using the on-board laboratory under the ever-wacthfull eye of NGI’s Tom Lunne.

The works were completed without incident on 22nd May and the ship sailed to Bømlo in Norway to de-mob.