Operation of Two Newbuild DP Drillships on the Girassol Field
Authors: Duhen Thomas , Studer Regis , Richard Claude 
Published: October 2008

Pride Foramer was awarded two long-term contracts for the operation of two deepwater dynamically-positioned drillships on the Girassol project, offshore Angola. This paper will summarize the experience gained to date in the start-up and operation of these new drilling units. It will also review the management approach used to enhance the health, safety and environmental performance of the drillships.

Introduction

Girassol is a ‘fast track’ deepwater development which combines a high degree of technological innovation and an aggressive schedule. There was a requirement to drill and complete approximately 10 wells before first oil to meet the project objective of swift production ramp-up. Development drilling had to begin towards the end of 1999 in order to reach this objective.

A market survey conducted in early 1997 by TotalFinaElf concluded that there were a limited number of rigs - approximately 20 - technically suitable to work in the deepwater environment at Girassol and that many of these units were under long term contracts. TotalFinaElf decided to issue a call for tender early in the project to provide sufficient time to allow for the possible building of new units.

Two contracts for newbuild rigs which would carry out exploration and development drilling in Block 17, offshore Angola, were awarded to Pride Foramer between September 1997 and March 1998. The construction schedules for these units - from 18 to 23 months - were ambitious with expected deliveries between August and November 1999.

These drilling units were to be built in Korea and delivered on site in October 1999 and May 2000, respectively. An incident with the first unit, Pride Africa, led to the loss of the subsea BOP - subsequently recovered - and operations were resumed in June 2000.

The both drillships have been operating in Angola since mid 2000 and have drilled and complete 12 wells before first oil. This paper presents the experience gained during the construction and the operational phases.

Rig design and construction phase

Overall design of the unit.

With the expected deepwater development program planned for the newbuild rigs, the main requirements which governed the design were:10,000ft (3,050m) water depth capability which can handle large variable load and storage capacities;Shipshape unit with dynamic positioning of a size that could be built at most shipyards at a reasonable cost;No crude oil storage on board;Optimum motion characteristics on the drillfloor in order to enhance safety and limits of operations;Stationkeeping capability sized for the environmental conditions corresponding to maximum motions and accelerations compatible with drilling operations; andSpecific Girassol requirements.

Main design features.

A basic design was developped with IHC Gusto Engineering taking into account the following technological options and specific arrangements: General arrangements in line with the design philosophy of the company's previous drillships with specific adaptations; Double cellar deck for simultaneous BOP and xmas tree storage and handling.