Abstract

Described herein are the subsea system design and project execution techniques used on the Typhoon project, which were new or little used concepts, but were noteworthy successes. Included in this list are retrievable stainless tube flying leads, sparing philosophy, Stab and Hinge-Over flowline connection system, and fast track procurement.

Introduction

Presented in this paper is the subsea production subsystem of the Typhoon development system located in Green Canyon Block 237. The project team was tasked to deliver and install a four-well system within the timeframe to design and build the TLP, approximately 16 months. First production was realized ahead of schedule in July, 2002. The subsea system and its components are outlined below including successful new concepts that may be of use to future system designers. Primary drivers in the subsea system design were high reliability, flexibility and maximization of value through prudent selection of components. Technical and cost trade-offs experienced on the project and lessons learned are qualitatively discussed along with unique issues that arose during the installation phase and intervention operations that were required.

Typhoon Development System

The Typhoon development system consists of a mini-TLP in 2100 ft of water fed by four subsea wells individually tied back to the platform and export pipelines. See Figure 1. Oil is exported through a 10" SCR and pipeline to the GC19 platform. Gas is exported through an 18" SCR and pipeline to the EI371 platform. Reuse of exploratory and appraisal wells as development wells enabled development value to be maximized by accelerating first production and minimizing development costs.

Each subsea well was connected to the host platform by a separate flowline and control umbilical. Comprising an umbilical are hydraulic control lines, chemical injection lines and electrical data acquisition conductors. Chemical injection was provided at the tree and downhole to prevent plugging by hydrates, asphaltene and paraffin. Two of the wells intersected multiple zones and utilized downhole zone selection valves to access the zones without requiring intervention by a workover rig.

Project Execution.

The Typhoon subsea system was executed by a small project team on an accelerated basis relative to other major systems within the project. This created the condition where not all the design data was available for input at the start, but required close supervision and prioritization of tasks to provide that data when needed. The procurement process was performed in seven weeks from initiation of specifications through bid award. Completion installation operations commenced ten months after bid award. Installation of flowlines was performed after the TLP was in place. Third party inspectors deployed in suppliers' shops proved to be valuable in supplementing the project team.

Subsea System
Christmas Tree.

The Typhoon Christmas trees are 4" × 2" 10,000-psi guidelineless horizontal tree systems. See Figures 2, 3 and 4. They allow for two tree chemical injection points, one downhole chemical injection point, and five downhole hydraulic lines for control of SCSSVs and zone selection valves

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