Flow Assurance, Operability Challenges, And Artificial Lift For The Azurite Field Development
Authors: Brezger Kelly , Rodriguez Wilson , Cai Jianlin , Reaux Muriel , Korneliussen Leif-Arne 
Published: July 2010

Azurite field is located in the Mer Profonde Sud (MPS) block offshore Republic of Congo in 1400 meters water depth. The field development employs the world's first Floating, Drilling, Production, Storage and Offloading (FDPSO) vessel to produce the Azurite reserves. Six subsea production wells and three water injection wells will deliver a peak production of 40,000 barrels of oil per day (bopd).

Azurite production will ramp up over a period of one year. During this time, issues of low temperature caused by low flow, and commingling of well completion and production fluids will present flow assurance challenges. Operationally, among all of the Azurite flow assurance and operability issues, those of artificial lift, wax precipitation and deposition, hydrate formation and unbalanced reservoir pressures are the most critical.

This paper highlights the beneficial effects on flow assurance by selecting the FDPSO concept, and presents the flow assurance and system operability challenges and solutions for the Azurite field during startup and development, normal production, and transient periods. Included in the paper is a discussion of artificial lift techniques considered, and the evaluation process that led to selection of seabed multiphase pumps. While Azurite has a relatively short operating history to date, a comparison of predicted versus actual behavior is also presented in this paper.

Introduction

Azurite field is located in the Mer Profonde Sud (MPS) block offshore Republic of Congo in 1400m water depth. The field development employs the world's first FDPSO to drill and produce the Azurite reserves. Six subsea production wells and three water injection wells will deliver a peak production of 40,000 bopd.

The Azurite reservoir contains black oil with a gravity of 25o API, a gas to oil ratio (GOR) of 460 standard cubic feet per barrel (SCF/bbl) and a high wax appearance temperature (WAT) of 129oF. The predicted water cut (WC) ranges from 0% at initial production to 91% as production declines.

Production from Azurite will ramp up over a period of one year. During this time, issues of low temperature caused by low flow, and commingling of well completion and production fluids present flow assurance challenges. Among all of the flow assurance and operability issues for Azurite, artificial lift, wax precipitation and deposition, hydrate formation and unbalanced reservoir pressures are the most critical ones.

To ensure system operating flexibility and the ability to displace live fluids, a looped flowline/riser system was selected. To maximize recovery and provide a means of artificial lift, a multiphase pump (MPP) was designed for the subsea production system (SPS).

The SPS employs passive thermal insulation and looped flowlines with hot dead oil circulation as the primary means to prevent hydrate formation. To mitigate the risk of wax deposition, an operational strategy of regular pigging and the use of inhibitors were selected.

This paper presents the advantages afforded to flow assurance by the FDPSO concept, flow assurance and system operability challenges faced, and solutions developed during the course of design development for field startup, normal production and transient periods for the Azurite field development.