Aasgard: Simultaneous Development of an Oil and Gas Cluster in the Norwegian Sea
Authors: Haaland S. , Fortmuller C.G. , Pollen T. , Roosmalen J.J.v. 
Published: December 2007

The Aasgard Unit, located in the Norwegian Sea, is comprised of the Midgard, Smorbukk and Smorbukk Sor Fields. The fields are developed as a unit to increase both economic potential and recoverable resources. Aasgard will be developed with two production units. A floating production, storage and off loading unit (FPSO) will provide early liquid production capacity. A semi-submersible gas center (SEMI) will provide facilities required for the gas export phase. Both production units will be located on or near the Smorbukk Field.

The volumes of recoverable hydrocarbons on Aasgard are estimated to be 232 × 106 Sm3 of sales gas and 123 × 106 Sm3 of hydrocarbon liquids (oil, condensate, naphtha).

The reservoir quality and fluid content of the three fields vary widely. Midgard contains a relatively lean gas condensate in high quality sandstone. Smorbukk contains volatile oil and rich gas condensate in fairly low quality sandstone. The GOR ranges from 300 – 400 Sm3/Sm3 in the richest fluid systems on Smorbukk and Smorbukk Sor. to 5000 Sm3/Sm3 on Midgard. In addition, a certain amount of CO2 and H2S is expected in the well stream.

The production strategy reflects the variability in the reservoir quality and fluid content. Initially the gas contract is covered by Midgard, containing a lean gas condensate, and some smaller reservoirs in Smorbukk, containing richer gas condensates. The main liquid reservoirs in Smorbukk and Smorbukk Sor are gas flooded. Aasgard's gas export level was chosen to insure that these reservoirs are completely flooded before the gas is required to maintain the gas export rate.

The Aasgard development plan assumes a total of 60 sub sea wells (41 producers and 19 injectors). The wells are connected either to the production ship or to the gas center via sub sea templates and flow lines. For Smorbukk Sor, horizontal and branched wells are planned. Midgard and Smorbukk are planned developed using conventional wells. Due to the low permeability and in order to mitigate the effect of liquid drop out in the reservoir, wells on the Smorbukk Field will be stimulated by massive hydraulic fracturing.

Introduction

This paper gives an overview of the status of planning and development of the Aasgard Field as described in the Plan for Development and Operation (PDO).

The Aasgard Field is located in the Norwegian Sea at ca 650 northern latitude, about 200 km off the coast and 50 km south of the Heidrun field (Fig. 1). The water depth in the three field parts varies between 240 and 310 meters.

License History

The three parts of the Aasgard Field (Fig. 2) have different license history. Saga is the original operator in blocks 6507/11 and 6407/2. Saga discovered Midgard in 1981. Statoil is the operator in blocks 6506/12 and 6506/11. Smorbukk was discovered in 1984 and Smorbukk Sor in 1985.

Late 1993 early 1994 a large potential was identified for a unitized development of the three fields. Autumn 1994 Statoil and Saga signed a co-operation agreement that also included transfer of Saga's operatorship of Midgard to Statoil and transfer by Statoil of a 7% equity share in Smorbukk and Smorbukk Sor to Saga. Thus, Statoil became the only operator for the Aasgard Field.

The Unitization Agreement was approved by the Ministry of Industry and Energy (MIE) in 1995 and 'Aasgard' was approved by the Norwegian Petroleum Directorate as the collective term for the three fields forming part of the co-operation agreement. The license holders in Aasgard are:

Den norske stats oljeselskap a.s. (operator): 60.50% Norsk Agip A/S: 7.90% TOTAL Norge A.S.: 7.65% Mobil Exploration Norway Inc. : 7.35% Neste Petroleum AS: 7.00% Saga Petroleum a.s.: 7.00% Norsk Hydro Produksjon a.s.: 2.60%

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