Abstract

The conventional practice for developing shallow water oil and gas fields is to install a bottom-founded structure over a drill center, then mobilize a jack-up drilling rig for drilling and completion operations. While this is a time-tested and proven method of producing hydrocarbons, it often does not provide the owner with the best investment economics. This is especially true for brownfield projects where the production capacity of existing infrastructure can readily accommodate new production. These economics are affected by multiple factors including the cost of drilling deviated wells compared to vertical or near vertical wells, time to production, and salvage costs.

Shallow water subsea production systems (SWSPS) are also a time-tested, reliable production technology. Installed on wells equipped with mud-line suspension systems, SWSPS provide advantages in many ways. Because they enable the use of a vertical wellbore positioned directly over the reservoir objective, SWSPS shorten drilling times by eliminating the need for highly deviated or directional wells. As compared to a conventional platform, a shallow water system can greatly improve field economics as measured by net present value (NPV) through many cost-savings features that shorten time to first oil, lower installation costs, and reduce abandonment and salvage costs.

This paper examines three modeled Gulf of Mexico oil developments located in less than 100 meters of water to demonstrate the importance that candidate selection has in maximizing NPV, and how subsea technology specifically designed for a shallow water environment is able to turn a marginal or uneconomic field into an economical development.

Introduction

Compared to deep water subsea production systems, relatively little has been published on shallow water subsea production systems (SWSPS) even though they were the foundation used to develop deep water subsea production systems. The large number of SWSPS in place world-wide, and their many years of successful operation, demonstrates the reliability that can be obtained with this equipment. SWSPS are being seriously considered by many operators to improve asset economics by enabling individual wells to be tied back to the existing platform infrastructure.

The key components of a shallow water system consist of a subsea tree fitted with a net guard (where required), the flowline and umbilical, risers, a production manifold (not shown) and a control system, Figure 1.

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