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Abstract

Spud can/soil interaction is a critical parameter in determining the safety of jack-up operations under complex soil conditions. This paper presents a cost effective modification to a standard spud can design, based on the requirement for a 5 m long skirt and an increase of the spud can area from 250 m2 to 350 m2. This is achieved through addition of a dough-nut shaped extension which can be installed and removed with the rig afloat in sheltered water.

The primary reason for the modification is to increase the soil bearing capacity.

Since the extension increases the seabed fixity of the footing; moment loading and dynamic effects on the jack-up are also reduced, increasing the operating envelope of the jack-up.

Introduction

Smedvig's jack-up West Epsilon is from the 3rd quarter 1995 contracted to carry out production drilling in the Sleipner Vest field with the derrick and substructure in a skid-off mode as shown in figure 1.

The complex soil conditions in the field with variable soil strength, requires an unconvential spud can design in order to meet the 1.25 material factor required by the Norwegian Petroleum Directorate (NPD) /Reference 3/.

WEST EPSILON

West Epsilon is a Marine Structure Consultants bv (MS C) design, type CJ62-S120 (62 gives the distance between the leg centers and 120 is the design water depth rating, both in meters).

West Epsilon was built by Far East Levingston Shipyard Ltd (FELS) and was delivered to Smedvig in May 1993.

Principle dimensions and capacities of the West Epsilon are given in table 1.

SLEIPNER VEST FIELD

Sleipner Vest is located in the Norwegian Sector of the North Sea and spans blocks 15/6, 15/8 and 15/9 in 107 m water depth.

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