Advanced use of Flexible Risers for the Åsgard Project
Authors: Fjell K.H. 
Published: October 2008

The Åsgard development project comprises three field installations, a ship shaped vessel (sgard A) for the liquied Åproduction, a semisubmersible platform for the gas production (Åsgard B), and a ship shaped vessel (Asgard C) for the condensate stotrage.

The development of the Åsgard field represents the largest technical challenge yet in the use of flexible riser technology.

The project will put various aspects and design requierments such as large diameter, high pressure and high temperatures of felxible riser technology to the test.

The flexible risers shall service more than 60 subsea wells, which are planned for the field, transfer lines between the different field installations, and a 42 inch diameter pipeline which will be installed to transport the gas from the field to Southwest Norway.

Introduction

The Midgard, Smørbukk, and Smørbukk Sør fields which together constitute the Åsgard field are located on Haltenbanken in the Blocks 6507/11 and 6407/2, 6506/11 and 12, and 6506/12 respectively, see Figure I.

Reserve basis for Åsgard application for gas allocation is shown in Table I.

Total technical recoverable reserves in the Åsgard field amounts to a most likely (P50) figure of 232 GSm3 gas and 123 MSm3 condensate and oil.

The Midgard field was discovered by Operator Saga in 1981, while the Smørbukk fields were discovered in 1984 and 1985 by Operator Statoil.

Midgard and Smørbukk Sør were declared commercial by the respective licenses in 1992.

In the fall of 1993, the Operators Saga and Statoil initiated a value creation study, with the main objective to assess the possibility of maximising the overall value for all owners of the fields by developing the fields coordinated.

Throughout the spring of 1994, Statoil and Saga in cooperation documented significant added value and synergy effects by coordinating the fields developments of Midgard, Smørbukk, and Smørbukk Sør.

A closer co-operation between the four licenses PL 062, 074, 094, and 134 was implemented by the signing of a Smørbukkl Midgard Unitization Agreement 27 February 1995. The agreement was approved by the Ministry of Industry and Energy 10 April 1995. Contingent upon this unit being established, the authorities have implemented sliding scale for the four licenses with effect from I January 1995.

The participating interests of the licensees in the Åsgard Unit, are shown in Table 2.

Field Layout

The development concept for Åsgard field is based on production from two separate field installations. A floating production, storage and offloading vessel (Åsgard A) for liquid production, located in the area between Sm0rbukk andSmørbukk Sør, and a semi-submersible floating production platform (Asgard B) located centrally to the East of the Smørbukk field.

All production and injection wells will be developed by subsea installations. The principles of the Åsgard field layout are shown in Figure 2 and 3.

The main principles with the field layout are that Midgard, which is a gas field will be tied to Asgard B, while Smørbukk Sør which is mostly an oil field, will be tied to Åsgard A.