Field Validation and Learning of the Parque das Conchas (BC-10) Subsea Processing System and Flow Assurance Design
Authors: Deuel Charles Lloyd , Chin Y. Doreen , Harris Jonathan , Germanese Vincent James , Seunsom Noy 
Published: May 2011

Parque das Conchas (BC-10) is a deepwater development offshore Brazil. A novel Caisson / Electrical Submersible Pump (ESP) subsea separator (gas/liquid) and pumping system to enhance production and maximize recovery has been utilized as part of the development of two of the fields (Ostra and Abalone). A third field, Argonauta B-West utilizes multiphase boosting with a modified Caisson/ESP (C-ESP) system to operate with a single, non-separated multiphase outlet. These novel designs have significantly impacted system and flow assurance engineering such as separator level control, hydrate mitigation, system operability, and chemical injection. The fields have been successfully started up with production through the subsea processing system since late 2009.

This paper outlines the performance of the subsea processing and production system from the perspective of flow assurance, and presents comparisons of the actual operating performance to design expectations. Learnings from key factors that strongly impact the production system operability and operational strategies are discussed, including the achieved separation efficiency of the caisson, the impact of defoamer performance on caisson operation and the importance of the hot oil circulation system.

Introduction

Parque das Conchas (BC-10) is a deepwater (~ 6000 ft) development located at Campos Basin, approximately 75miles southeast off the coast of the city of Vitoria in Brazil. Shell is the operator with a 50% interest, in a joint venture with Petrobras (35%) and ONGC (15%). Since its startup in July 2009, BC-10 has been in successful production.

The properties of the fluids in the BC-10 reservoirs vary considerably with depth from heavy, low GOR fluids to light, high GOR fluids. These properties, and the fact that BC-10 requires subsea artificial lift to achieve economic production rates posed severe challenges for the design and operation of the subsea system [1].

Figure 1 provides an overview of the development. The Ostra and Abalone fields are produced in a commingled mode. The Ostra field has 6 producers and 2 production manifolds (PM1 and PM2). An artificial lift manifold (ALM1) equipped with four separated C-ESP systems connects to PM1 via flowline jumpers. The produced fluids from the wells flow into three caissons while the fourth caisson stands by as a spare. The well streams entering the caissons (currently at over 1200 psig) are separated into gas and liquid phases. While the separated gas flows into the Ostra gas line, the liquid flows down the length of the caisson and is boosted by the ESP and enters the Ostra oil line.

The B-West field has a stand-alone subsea production system. The two producers are connected to two non-separated C-ESP systems located at artificial lift manifold 2 (ALM2). Each producer is designed to flow to its own caisson and flow to topsides via its own subsea flowline. In addition, the producers can be directed into one caisson and flow via one flowline to the FPSO while the other flowline works as the service flowline if needed.

Both Ostra and B-West require subsea artificial lift to achieve economic rates, due to their low reservoir energy. The novel subsea hardware and design provides robustness and flexibility to ensure sustainable production performance, and to safeguard the subsea production system after shut down.