Perdido Startup: Flow Assurance and Subsea Artificial Lift Performance
Authors: Littell Howard Steven , Jessup James Webster , Schoppa W.W. , Seay M.R. , Coulon T.D. 
Published: May 2011

The Perdido Regional Host is in the ultra-deepwater Gulf of Mexico, and produces from two Lower Tertiary horizons in multiple drill centers; some directly under the host SPAR, and others offset up to 7 miles and in water depths between 7800 and 9600 ft. All of the production is from relatively low-energy reservoirs, and posed considerable productivity challenges. The approaches to managing flow assurance risk and maximizing recoverable volumes were driven by the economically challenged environment in which the system was conceived and designed, and resulted in a unique host configuration relying on subsea wells and five high-powered ESP artificial lift systems with slug catching and two-phase separation accomplished on the seafloor. The final commissioning and early production characteristics of the system as related to the design intent and operational expectations will be described.

The commissioning and early production phases of the development provided opportunities to validate Perdido subsea hydraulic models and operational methods that were considerably different from the typical approach employed by major oil companies in deepwater. Novel monitoring and surveillance tools generated by the project were benchmarked using early production data, and learnings were recycled into improvements to these models.

This project is a considerable extension to previous systems, and due to the cost constraints of the risked recoverable volumes and high cost of operating in the ultra deep environment, it was imperative to advance the state of the art of flow assurance and operability.

Introduction

The Perdido project encompasses the Great White, Tobago, and Silver Tip fields and is located some 250 miles south of Galveston, Texas, in Alaminos Canyon 857, only 2 blocks, or 6 miles from the Mexico maritime border. The fields are all being developed with subsea wells tied back to the host, which has full processing capabilities and exports gas and oil via pipeline. In Figure 1, the Spar is shown as a hub with three flowlines from offset drill centers back to the manifold system underneath the host. The Southwest Cluster taps the same Great White field as the wells directly under the host and is about 2.5 miles from the host. The Frio drill centers are also in the Great White field, and are 1.8 and 2.7 miles from the host, respectively. Tobago is 6.2 miles to the east, and Silvertip is 1.7 miles to the north of Tobago and flows through the same flowline, referred to as the Regional System. All of the production flowlines lie completely on the seafloor; there are no flowline risers to the Spar. The manifolds under the host connect the offset wells and the local producing wells to subsea separation and artificial lift systems utilizing Electric Submersible Pumps (ESPs). There is also a waterflood installed to aid production from the anchor reservoir in the Great White field. The host nameplate capacity is 100 mbopd, 40 mbwpd, and 200 mmscfd, with seawater injection capability of 80 mbwpd. Refer to Ju, et.al. (2010) for a more complete high-level overview of the subsea system.