Early Subsea Production Systems Advance The State-Of-The Art

Abstract

ABSTRACT Hydrocarbons have been found offshore in considerable quantity and quality. Whether this increasingly scarce commodity can be exploited to extend the age of fossil fuels depends on the development of offshore production systems. During the summer of 1977, a modular template for a five-well early subsea production system was built in Aberdeen, Scotland. Shell Oil has purchased this system for installation in the North Sea. The system was designed eventually to be tied back and produced to a fixed platform. A different type early subsea production (ESP) system, one using a unitized template, was employed by Petrobras as part of the Garoupa field development in the early part of 1978. Of particular interest is the unique 20-in. pile leveling system, which allows placement of the template onto the ocean floor in a horizontal position. As was the case for the Shell ESP system, these template wells also will be individually tied back to a fixed platform structure. Various ESP systems have been employed and successfully operated in some of the most hostile offshore environments. One, therefore, can argue that the technological and economic viability of ESP systems has been proved, although general acceptance by a conventionally conservative industry cannot be claimed yet. The ESP systems, subject of this paper, are specifically designed to render currently marginal fields economically viable and to extend hydrocarbon production into deeper waters. Another application for these systems is to provide cash flow during the early stages of a major field development when permanent production systems are being constructed. INTRODUCTION It will be known to most readers that the price per barrel of crude oil continues to rise to ever record levels. It may be less known that the cost of drilling and completion also is rising at astronomical rates. Several reasons can be considered contributory to the rise in drilling and production costs such as inflation, politics, and, not least, field accessibility. The offshore industry is moving ever further offshore into deeper waters in their quest for finding economically viable hydrocarbon deposits. The extreme high drilling and production costs for these deep-water offshore fields have prompted the oil industry to investigate alternative production systems that can provide substantial savings in over-all investment and development time required. One such method has been called the early subsea production (ESP) system. Several variations of this approach are available, having in common the fact that the drilling stage of the field development can commence and continue while the production facility such as a bottom supported platform or a floating production vessel is under construction. Two distinctly separate groups can be identified within these various systems:the ESP systems utilizing a floating production platform, andthe ESP systems tied back to a fixed or bottom supported production facility.