Norwegian Petroleum Consultants in conunction with Mentor Engineering Consultants were awarded the Detailed Engineering Contract - Subsea (DECS) for Snorre, the largest individual subsea development in the North Sea to date.
Specifically, this work was to provide for verification of conceptual engineering and development of the necessary documentation required to enable Saga to go out for competitive tendering for the Engineering, Procurement and Construction (EPC) contracts for all subsea equipment.
Equipment designs which have been evolved during this period represent state-of-the-art technology in subsea engineering and contribute significantly to the fact that the Snorre development marks a major milestone in the evolution of subsea production systems.
All EPC-contracts- have how been awarded and the project is in the construction phase with stringent requirements to overall system engineering and interface control.
Purpose of this paper is to present an overview of the Snorre Subsea Production System and to highlight some of the technological challenges and achievements which have been experienced during the project to date.
The Snorre Field is located within blocks 34/4 and 34/7 in the Norwegian sector of the North Sea. Saga Petroleum a.s., as operator, plan to develop the field utilising a Tension Leg Platform (TLP) and a Subsea Production System (SPS).
Phase I of the field development is planned to include one TLP and one remote subsea template connected to the TLP by means of flow lines and risers. The TLP provides partial processing and export facilities to deliver oil and gas through pipelines to Statfjord A for final processing and transport.
Two options are under consideration for Phase II of the field development. One option allows for repositioning of the TLP to another field location with reconnection of the subsea template to the TLP. The second option provides for two additional subsea templates tied into the TLP at the original location.
The configuration of the TLP and associated facilities will provide for adoption of either Phase II field development option. Final selection is anticipated to be made after Phase I field development has progressed sufficiently to enable an improved appraisal of the reservoir.
The SPS selected for Snorre is a third generation design and is suitable for both alternate Phase II development options. The SPS incorporates existing designs, hardware. and procedures with only minor modifications. Furthermore, with proper design and implementation of system operating procedures, simultaneous drilling and production operations can be safely conducted.
The principal elements of the SPS are presented in Figure 2.1. The combined template and manifold measures approximately 48m × 32m × 16m and weights about 2500 tonnes. The template and manifold system provides for production gathering from producing wells and distribution of water to injection wells. Wells will be directionally drilled from a floating rig through the template, completed, and connected to the manifold through the subsea trees. Well production is gathered into the two manifold production headers and subsequently to individual flow lines which deliver produced oil and gas to process facilities located on the TLP, some 6km away.