A new generation DP Drillships, the Gusto 10000 and Gusto P-10000
Authors: Schoonmade Willern , Janse Wirn , Lusthof Jeroen , Rietveldt Bob 
Published: October 2008

In the early seventies, IHC Gusto Engineering developed the dynamic positioned drillship "Pelican class" design, with assistance from drilling operators for the drilling package. The "Pelican" design became the most widely used design for DP drillships, with 10 units built. For the new challenge of ultra deep water, with water depths up to 10.000 ft, IHC Gusto Engineering developed a new generation DP drillships. Two different designs were made, a "pure" drillship, the Gusto 10000 and a drillship with extended well testing capabilities, the Gusto P- 10000. A description of the designs, the resulting motion characteristics and the DP and operational capability is given in this paper.

Introduction

Deepwater drilling requires specialised vessels, enabling economic exploration and further exploitation of deepwater prospects. In this paper the new generation drillship and extended well testing vessel are described, which have been developed by IHC Gusto Engineering (Gusto) in close cooperation with the world's major drilling contractors. Drillships are historically associated with Gusto as ten DP vessels were already built to the original Pelican class design during the seventies and the eighties. Today Gusto once again has a drillship concept, which will meet the challenges of the next decades. Two concepts have been developed, being the Gusto 10000 and Gusto P- 10000, which are respectively a fill blown drillship suitable for operations in waterdepths up to 10000 feet and a drillship / extended well testing unit also suitable for 10000 ft waterdepth. The Gusto 10000 has been chosen by Foramer / Pride for their operations at the Girasol field, and is presently under construction at Hyundai Shipyards in Korea. A derative of the Gusto P- 10000 was selected by Global Marine Drilling.

Design philosophy

What drillship for which drilling operations? Hereafter is the philosophy behind the Gusto 10000 designs. The main dimensions of the vessel are designed to provide a high payload capacity to optimise field logistics and to have superior motion behavior &d minimising downtime. Although the vessel can work worldwide, it has especially been designed to work offshore West of Africa, in the Gulf of Mexico, offshore Brazil and in South East Asia. The vessel is capable of drilling operations up to a 10-year return-period storm and can stay on location up to a 50-year return-period storm. The large deckspace and deadweight capacity will allow the unit to work long periods at remote locations. The equipment is sized to obtain the maximum performance out of the vessel, whilst reducing the costs of e.g. the DP equipment and power generating plant, being main contributors to the overall cost of the unit. The hull size provides low costs due to reduced steel construction and delivery time. Above given philosophy has led, with the input of one operator to a pure optimised drillship design. With another operator's requirements for drilling as well as extended well testing and production capabilities, an enhanced version, the P- 10000 was designed, illustrating the Gusto tradition for custommade design. When drilling in very deep water depths, the drilled depth is becoming short compared to the total depth: unproductive handling operations take a higher proportion than productive making hole operation.