A new subseabed concept for anchoring of floaters denoted Deep Penetrating Anchor (DPA) is under development. The anchor comprises an arrow shaped steel construction with a trailing chain or steel rope, which is dropped from typically 20–40m above the seabed and penetrates to target depth by its kinetic energy. No external energy source, mechanical operations or intervention is required on the anchor itself during installation. The anchor design allows for standardized fabrication and utilizes standard procured elements with a minimum of pre-fabrication work. An anchor handling type vessel as well as any offshore type of construction vessel can perform installation.
Following the move of oil and gas field exploitation into deeper waters, the issue of seabed foundations and anchoring has become an increasingly important part of the development scenarios involving floating installations. In increasing water depth, it is believed that mooring costs will escalate mainly due to increasing marine operation costs. Effort has therefore been focused towards developing a simplified anchoring solution, where simplicity relates to effective installation and reduced time and complexity of marine operations. This paper presents a proposal for a low cost subseabed anchoring concept, which simplifies installation operation and makes it less sensitive to increasing water depth. Furthermore, it takes advantage of the dominant deep-water seabed soil being soft to very soft normally consolidated clay, often to great depths.
Research and development work is ongoing whose main goal is to further develop an anchoring solution that is ideal for deep-water mooring in soft seabed sediments.
Fig. 1 shows an idealized representation of what is termed a Deep Penetrating Anchor (DPA), (SINTEF, 1997), and is meant to be released freely from a predetermined height over the seabed.
