Major Technical and Regulatory Issues for Monohull Floating Production Systems in the Gulf of Mexico.
Authors: D&apos;Souza Richard 
Published: October 2008

Monohull based production platforms are the most widelyused floating production systems worldwide. They are proven as a reliable workhorse and have provided the industry with a commercially attractive platform for producing large and small offshore oil developments in most major offshore producing regions. The ship-shaped monohull offers low cost "real estate" for production facilities, and its integrated storage and offloading feature eliminates the oil export pipeline. To date an FPSO * has not been employed in the US Gulf of Mexico because of the extensive infrastructure of existing host platforms and pipelines on the continental shelf. However, in recent OCS lease sales, operators have acquired vast, undeveloped acreage that is increasingly remote from this infrastructure. Beyond the shelf, the potential for a low capital cost platform and elimination of, what can be a cripplingly expensive oil export trunkline, has many operators considering FPSOs to develop these remote, deepwater prospects. This paper examines and discusses major technical and regulatory issues that the industry (regulators, operators, contractors) must collectively address prior to introducing the first FPSO into the US Gulf of Mexico.

* Abbreviations are explained at the end of the paper.

Introduction

The monohull FPSO was first used to produce the small Castellon field in the Mediterranean Sea in 1977. The system produced 20,000 bopd from a single subsea well tied-back to a turret moored converted tanker in 350 feet of water. This FPSO was the genesis of what has become the most widely employed floating production system worldwide. Over 60% of the worlds floating production platforms in use today are either converted from tankers or are purpose built monohulls. From 1977 to 1993, 24 FPSOs were installed, 17 of which were conversions. They were mostly used to develop small oil fields in areas remote from pipeline infrastructure. Large integrated oil storage capacity permited periodic shuttling of parcels of produced crude in shuttle tankers to a sales point, while enabling uninterrupted production and eliminating the need for an oil pipeline.

These FPSOs proved to be reliable workhorses, that gave operators a commercial option to exploit marginal, remote oil fields. As confidence in these systems grew, along with technological advances in subsea wells and flexible risers, operators began to expand their application to progressively larger developments in increasingly deeper waters and harsher environments. Since 1994, 36 FPSOs have been installed. Of these, 15 are in the demanding North Sea and Atlantic Frontier Provinces. Petrobras has converted several VLCCs for use as FPSOs in the Campos basin in water depths upto 6000 feet.

Table 1 captures the progression of FPSOs from its humble beginnings at Castellon, to the most technologically advanced FPSO recently installed in Statoils Asgard field in the Norwegian North Sea.

Despite its widespread and burgeoning use, only one FPSO has been employed to develop an offshore field in US waters. That was Exxon's Offshore Storage and Treating Unit (OS&T) that operated in the Santa Barbara Channel in 500 feet of water from 1981 to 1995. A monohull FPS has never been used in the US Gulf of Mexico, one of the most prolific offshore oil and gas producing regions in the world.