Equatorial Guinea Zafiro Field Development - An Overview
Authors: Alexander C.H. C.H. , Richardson Emmett M. 
Published: October 2008

The Equatorial Guinea Z h o project was brought onto production 18 months after the initial discovery. The Zafiuo development consists of 8 wells tied back to an FPSO, in a remote region, offshore West &ca. This paper gives an overview of the Zafiro Field development, with particular emphasis on the field design strategies necessary to take account of a developing information base while progressing engineering, procurement and construction to meet the ambitious time frame. A description of the resulting subsea and floating production facilities is given.

Introduction

This is an overview paper on the Zafiuo Field development in Equatorial Guinea. Supporting papers which describe different aspects of thls development in more detail are:Blundell, L.C., Kaminski, H.P., Famakinwa, S.B, Stephens, A.R.: "Evaluation and Integration of Data in a Fast-Track Development Strategy: Zafiro Field, Offshore Equatorial Guinea," paper SPE 8426Humphreys, N.V.: "Using lnterfefence Tests during Field Startup to Solve Critical Reservoir Management Issues at the Zafiro Field, Offshore Equatorial Guinea'', paper SPE 8430Hewlett, C.W., Bhattacha jee, S., Liles, E. Huddleston, C. McCabe Design: " Conversion and Installation of an FPSO Vessel for Zafiro Field", paper SPE 8427Cook, T.B.: "Subsea Production Equipment for the Zafiro Field", paper SPE 842Nooteboom, U.G., Menier, P.: " Zafiro Field Subsea Flowlines and Umbilicals Designed, Manufactured, and Installed in Record Time", paper SPE 8429.

In 1994, Mobil and United Meridian Corporation (UMC) became partners for the development of the B-Block, qffshore Equatorial Guinea. B-Block contains 500,000 acres, with water depths ranging from 300 ft. to 3,500 ft. The first exploration well, Delta- 1, was drilled in April 1994, based on 2-D seismic reservoir appraisal. Delta-1 was a dry hole. A second exploration well, Zafiro- 1, was drilled in February 1995. The result was a discovery, in March of 1995, which tested at 10,400 barrels per day. Over the next 3 months three more wells were drilled in the vicinity of Zafiro- 1. In all, 3 wells were tested.

The reservoir was relatively shallow, around 5,000 ft, and low pressure, with a bottom hole shut in pressure of 2,800 psig. Viscosities from the three well tests ranged from 26 to 44 degrees API, and GOR's ranged from 300 to 800. Continuity between the wells could not be determined from the well test data.

While the DST data were encouraging, it was not sufficient to just@, or even plan, a fill field development. There was uncertainty as to the size, distribution and connectivity of the reservoir(s). There was uncertainty that the fluid and reservoir properhes found in the three drill stem tests were representative of the fill field. Faced with such uncertainty and the inherent risk, further drilling, 3-D seismic and extended well tests would normally be undertaken prior to development.

In this case, rather than take the time to reduce the risk, the decision was made to proceed directly to an early production system and to manage the risks. A full 3-D seismic evaluation was initiated, and plans for an early production system were put in motion; this strategy was to generate income while gathering actual reservoir performance information.