ABSTRACT

The Deep Penetrating Anchor (DPA) is a new concept in anchoring and has undergone the scrutiny from a broad range of disciplines through a feasibility study conducted in the winter of 1998/1999(Lieng et ai. 1999). The study comprised fluid dynamic analysis of the anchor and chain during the free fail phase, geotechnicai anchor penetration analysis and FEM-anaiyses for estimation of anchor capacity, soil consolidation and deformation during loading, evaluation of fabrication, transportation and installation techniques and cost estimates. In addition to reporting on some of the results from the feasibility study in this paper, an effort has been made to compare results from vertical pullout capacity calculation found from simple pile analytical methods with the more arduous but thorough FEM analytical approach.

INTRODUCTION

As the development of oil and gas field exploitation moves into deeper waters, anchoring has become an increasingly important part of the development scenarios involving floating installations. Marine operational costs increase exponentially as water depths increase and the seabed sediments get softer as does the soil shear strength. Effort has therefore been focused towards developing an anchoring solution where simplicity relates to effective installation and reduced time and complexity of marine operations. This paper presents some results from a feasibility study on a low cost anchoring concept, which simplifies installation and is less sensitive to increasing water depth than conventional concepts.

CONCEPT DESCRIPTION Criteria

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. The following criteria are demanded in order to make the concept viable. (a) Anchor installation must be simple. (b) The anchor must not be complicated or too expensive to fabricate.

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