An Innovative approach to developing Gulf of Mexico Oil Production
Authors: Clarke A.G. , Kaalstad J.P. 
Published: October 2008

Recent deepwater discoveries in the Gulf of Mexico, where the nearest pipeline infrastructure may be more than 100 miles away, pave the way for an innovative approach to development, particularly for "marginal" sized fields.

This paper takes a look at the activities, and explores some of the systems and sub systems, that could be used to support production operations. The paper describes some of the key concepts and drivers surrounding marginal field development and presents an innovative approach based on existing and proven technology. The development concept presented is for a water depth of 2000meters, and consists of a Dry Tree Unit (DTU) with a disconnectable turret-moored Floating, Production, Storage and Offloading vessel (FpSO) in close proximity to it.

The FpSO, and transportation of produced oil, are based on the use of Articulated Tug Barge (ATB) units. Midwater flowlines between the DTU and the FpSO are utilised, together with integrated moorings. "Proof of Concept" model basin testing has been performed to verify the integrated solution as well as behavior of the individual units in varying sea state conditions. Findings confirm that use of a DTU, close coupled to a disconnectable FpSO, is both a feasible and cost effective alternative for deepwater GOM production. In addition, the use of synthetic mooring lines, abreast offloading and ATB's are also possible.

Introduction

Approximately eighteen months ago, an expert team was formed within Texaco to study different development scenarios for deepwater production. This was in anticipation of bringing production on line as soon as practical should the need arise. The development parameters guiding the team's work were:Conventional, current technology would be used where possible.Innovative, emerging technology would be used where it presented a practical alternative.Development economics would be optimized where possible.Safety considerations would be paramount to any concept studied.Methods to reduce development costs would be investigated.

The purpose of this paper is to share Texaco's approach and findings regarding the cost-effective development of deepwater prospects in the Gulf of Mexico. It is presented in three sections, with the first outlining the preferred concept, the second describing the mooring arrangements together with the results from "proof of concept" model basin tests, and the third discussing marine transportation issues.

System Description

The proposed development system comprises the following:A purpose built, double hulled, deep notch, FpSO barge of 500,000 barrel capacity, fitted with a submerged turret loading system. The unit is capable of loading, treating, storing and discharging crude oil to transfer vessels via either side or stern fitted discharge equipment. The vessel has self-contained accommodation for a minimum of 20 persons, and is capable of site abandonment in the event of a hurricane.A purpose built double hulled, dynamically positioned (D/P), articulated tug/barge shuttle tanker of 500,000 barrel capacityAn integrated mooring system, comprising chain/synthetic/wire ropes, connecting the FpSO to the DTU through both independent and common lines.Flexible mid-water risers.?Close proximity mooring of the FpSO to the DTU, at a distance of 700 meters.