Snorre Project Strategies and Status

ABSTRACT The Snorre development is one of the most challenging projects carried out in the Norwegian North Sea since the pioneering days of the early and mid 1970s. This paper summarizes these challenges and provides insights into Saga Petroleum's highly leveraged strategies for applying recent technology to develop this deepwater field. The field installations are described with emphasis on technical innovation. This theme is followed up, in more detail, in the other Snorre papers. The status of project manning, progress and cost is summarized as onshore fabrication nears completion. CHALLENGES The Snorre field is located west of the Norwegian trench approximately 26 km northeast of the Statfjord field. It is operated by Saga Petroleum on behalf of the nine other partners shown in Fig. 1. The reservoir and deepwater challenges on Snorre coupled with the turbulent oil price fluctuation of the 1980s have caused the project to seek and find innovative development solutions. Reservoir and Reserve Challenges The nature of the Snorre reservoir and the vast areal extent have made it necessary to drill a relatively large number of wells to develop the reserves. Compared to other large fields in the shallower waters of the Norwegian sector (Fig. 2), Snorre has lower reserves which are spread over the same area as Statfjord and Oseberg, and over a much larger area than Gullfaks. On the other hand, the number of wells which must be drilled is comparable. Thus, the reserves that can be recovered per well on Snorre are, on average, significantly less. The reservoir is located about 2500 meters below sea level. It consists of two sandstone formations, the Statfjord (Jurassic) and the Lunde (Triassic). The recoverable reserves are:Oil - 122 million cubic meters (770 million barrels)Gas - 7 billion cubic meters (250 BCF)Liquids - 3 million tonnes. A total of 68 million cubic meters (430 million barrels) of oil will be produced during the first phase of development. This will be the first time that the Lunde formation has been produced. In Fig. 3 a cross-section of the Lunde formation is shown through one of the more prolific areas. Most of the oil is located in the D, E, and F units. In the same manner as for the Statfjord formation, major faults with large throws divide the reservoir into fault blocks. Minor faults further subdivide the reservoir. The transmissibility of the faults is uncertain. The reservoir contains over-pressured, highly under-saturated oil. It must be developed by water injection pressure maintenance since no significant aquifer support is expected. The complex fluvial reservoir, low dip, and anticipated poor vertical communication were judged to be unsuitable for successful gas injection pressure maintenance. In addition, for the Lunde, the lateral continuity of the fluvial sandstones is considered to be limited. In order to achieve a satisfactory level of recovery, water injection will take place from the start of production. The plan for developing the total reserves calls for 93 wells to be drilled.