Parque das Conchas (BC-10) Subsea-Hardware Systems: Selection, Challenges, and Lessons Learned
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper OTC 20649, ’Parque das Conchas (BC-10) Subsea-Hardware Systems: Selection, Challenges, and Lessons Learned,’ by L.A. Olijnik and D.A. La Caze, Shell, prepared for the 2010 Offshore Technology Conference, Houston, 3-6 May. The paper has not been peer reviewed.

The ultradeepwater Parque das Conchas Project, offshore Brazil, includes the Ostra, Abalone, and Argonauta-BW fields in separate clusters tied back to the floating production, storage, and offloading (FPSO) vessel Espirito Santo. At 2,000-m water depth, several significant challenges had to be overcome and significant new technology had to be developed to make this project a reality, including the following.

Ultradeepwater completions deployed through a surface blowout preventer (BOP)

A combination of boosting-module systems in an artificial-lift manifold

First use of a heave-compensated landing system (HCLS) in Brazil

Introduction

Parque das Conchas is in water depths of approximately 2000 m. Phase 1 of the project comprises the subsea development of three fields tied back to a central FPSO. In Phase 2, a fourth field (Argonauta ON) is planned to be tied back.

Tree System

The BC-10 subsea-tree system, shown in Fig. 1, uses a vertical-tree design based on the field-proven 10,000- and 15,000-psi high-pressure/high-temperature vertical-tree systems. The system also uses a tubinghead spool (THS) for landing and orienting the tubing hanger, providing flexibility for offshore installation vessels and sequencing of events. The subsea tree contains the chemical-injection capabilities, and, therefore, no chemical is delivered at the production manifolds or to the pipeline terminations.

Slimbore-Completion System. It was decided to extend the surface-BOP (SBOP) technology to include completion techniques for these ultradeep-water wells. The SBOP enables use of smaller and less-expensive drilling rigs to drill and complete the ultradeepwater wells. The tubing-hanger system is small enough to pass through a 135/8-in. SBOP stack and is backward compatible with subsea BOPs.

HCLS. The drilling rig on the Parque das Conchas project is a moored vessel requiring anchor-handling vessels (AHVs). These AHVs were also deployed for installation of subsea trees and THSs. The HCLS technology enables subsea trees and THSs to be landed softly and accurately on the seabed from an AHV in almost any water depth. The installation method uses an automatic motion-compensation system that eliminates any tuning or adjustments needed because of changes in weather conditions.

Spacer Spool. Typically, the use of THSs imposes additional riser-handling operations to space out the riser when moving from a drilling mode to a completion mode. The main challenge is to reduce risk to personnel by eliminating riser-handling operations. Therefore, a spacer spool was designed to have the same height as the THS and to run connected on the bottom of the subsea-isolation device (SID) during the drilling mode. After the drilling operations, the SID was disconnected and the spacer spool swapped out for the THS. Then the rig initiated completion operations with the SID connected to the THS, without respacing the riser.