Traditionally offshore geotechnical drilling has been carried out using drilling systems that are mounted on either floating or fixed platforms on or above the water surface. However, as site investigations have moved into deeper water there is a move toward drilling systems located on the seafloor to provide greater efficiency and improved accuracy. This paper describes a new seafloor drilling system, which is capable of working in water depths of up to 4000m and is rated to drill to a depth of ~150m below the seafloor. The remotely operated system integrates established drilling technology with proven telemetry and controls. The flexible nature of the wire-line drilling technology enables efficient use of standard sampling systems, as well as downhole testing systems (including cone penetration tests (CPT), downhole sensors and borehole geophysical tools). The paper focuses on the new developments and shows results from recent sea trials and projects.
As energy and mineral exploration move into deeper water, there is a growing need for highquality drilling, sampling and in situ testing of near-surface seafloor sediments. Hence, a detailed evaluation of the seafloor sediments has become increasingly important. Traditionally, offshore geotechnical drilling has been carried out using drilling systems mounted on either floating or fixed platforms at or above the water surface (i.e. surface drilling). However, as site investigations have advanced into deeper water, there has been a move toward drilling systems located on the seafloor to provide greater efficiency and improved accuracy (i.e. seafloor drilling). Osborne et al. (2011) provided a summary of existing remotely operated seafloor drilling systems and summarised the advantages and limitations of various systems. Yetginer and Tjelta (2011) evaluated the effectiveness of seafloor drilling technology in terms of productivity, safety and other commercial considerations when compared to conventional techniques.