Fast Tracking Subsea Production Equipment for the Zafiro Field
Authors: Cook T.B. , Wester R.J. 
Published: October 2008

Fast-track delivery and installation of subsea production equipment was achieved in the Mobil/UMC Zafiro field development in Equatorial Guinea, West Africa. Subsea trees, production control system, flowline jumper connection equipment, and all associated umbilicals were delivered by the subsea equipment supplier in less than 12 months from commencement of work. By the end of the same 12 month period, the first five subsea wells were on stream. This paper reviews plans and actions utilized by the project management and engineering team to achieve the fast-track goals for the subsea production equipment.

An integrated operator/supplier project team employed key strategies to reduce engineering and manufacturing lead times well below those previously required for subsea production equipment. Standard hardware was used exclusively for critical system components, thereby avoiding the design and testing efforts associated with developing specialized equipment. Engineering resources focused primarily on application specific packaging of the standard components, and resolving external interface issues concurrently with the operator and other project suppliers.

Another key to the fast track project success was the use of a versatile, subsea flowline jumper connection arrangement. Field proven components, including ROV operated hydraulic connectors and flexible pipe were packaged into an innovative system. This design enabled flowline connections between the subsea trees and in-line flowline skids to be performed from either the drilling rig or flowline installation vessel. The flowline jumper system enabled the suppliers of subsea production equipment and subsea flowlines to design their respective equipment simultaneously, with minimal interface requirements and risk.

Introduction

After the March 1995 discovery of the Zafiro field offshore Equatorial Guinea, the operator, Mobil, conducted field evaluations over the succeeding 6 months.' In August 1995, formal authorization to commence work was issued to the subsea production equipment supplier.

Mobil ordered nine subsea trees (one being a spare), production control system, flowline connection equipment, and umbilicals. A six month delivery was required for the initial items; including the first subsea tree and a set of diverless installation and service tools. Delivery of all equipment was completed within 12 months.

As recently as a few years ago, an 18 to 24 month lead time after receipt of order was typical for subsea equipment delivery. The shortest previous delivery by the supplier for this operator was 10 months, and comprised only a single subsea tree with diver assist flowline connections.

As the Zafiro project activity level increased, several key decisions and actions were instrumental in meeting the aggressive project schedule. Those decisions and actions are presented in the Project Management and Engineering sections below. The two topics are not entirely separable, so they appear in both sections. A brief overview of the subsea production equipment configuration precedes the discussion of Project Management and Engineering.

Overview of Subsea Production Equipment

The Zafiro field is a multi well subsea development project offshore Equatorial Guinea in West Africa. Initially, five wells, located in approximately 600 to 1000 feet of water, were to be completed using diverless installation methods. Phase I of the development eventually expanded to eight wells.