The Britannia Field Development
Authors: Tetlow Jeff , Wingate Peter 
Published: October 2008

The Britannia field has been developed ahead of schedule at a cost which is 20% lower than the approved budget. This paper provides an overview of the development project and, using a Performance Improvement Model, explains how the result was achieved. The same result would not have been achieved using traditional project management philosophies. The processes and techniques described are applicable for other capital investment projects.

Introduction

The Britannia field is located 130 miles North East of Aberdeen in Scotland and lies in some 450 feet of water at a depth of 13,000 feet. (Fig. 1). The reservoir has considerable areal extent, being some 20 miles in length, west to east, and as much as 5 miles across, north to south. Simplistically, the reservoir is inclined along its length with its highest elevation in the north and its lowest in the south. The field is located in UKCS Blocks 15/29a, 15/30, 16/26 and 16/27a and 16/27b.

The reservoir contains a retrograde gas-condensate fluid, the composition of the fluid varying from west to east. The hydrocarbon is richer in the west, with a condensate gas ratio of 100 BBLS/MMSCF and is leaner in the east with a corresponding condensate ratio of 70 BBLS/MMSCF. Along the southern edge of the reservoir is an oil rim. Although the oil is a good quality light, but waxy, sweet crude it is relatively immobile. Underneath the oil rim there is an aquifer. There are five distinct regions along the length of the reservoir, each region having an aquifer with different water chemistry.

The reservoir has recoverable reserves of 3.1TCF of gas and 145MMBBLS of liquids. The distribution of reserves, however, is such that the majority lies in the east. The latest reservoir model puts the split at 25:75 west:east.

The field has been developed to meet the needs of gas sales contracts. As such, any development plan involved a significant pre-drilled well programme.1

The concept eventually chosen to develop the reservoir (Fig.2) employed two drill centres.

At the western end of the field is a subsea centre.2 The centre produces approximately 25% of the reserves. It comprises a manifold adjacent to seven pre-drilled production wells. The manifold can handle gas and associated liquids from up to 14 wells and is designed to produce up to 380 MMSCFD.

The subsea manifold is linked to a minimum facilities production platform located 15km away at the eastern end of the field by a unique flowline bundle.3 The bundle contains a series of flowlines grouped together, surrounded by a 37" diameter carrier pipe. The carrier pipe provides a hot water jacket to prevent hydrates forming as the reservoir fluids travel from the subsea centre to the platform. There were also a number of production chemistry challenges facing the designers of the system.4, 5

Located in the east of the field is a minimum facilities platform. The topsides6 include production, drilling and accommodation facilities. A total of 36 well slots are provided, incorporated in a centre wellbay concept. The topsides are supported by an 8 legged steel substructure located over a 10 slot well template for the pre-drilled wells.

Reservoir fluids from both the subsea centre and the platform are processed on the topsides to produce a dry, dense phase, export gas at rates of 740 MMSCFD and a 125TVP ondensate suitable for export at rates of 76 MBPD.