AAPG - R&D Projects: South Viking Graben
Academia-Industry Collaboration Provides an Improved Understanding of Rift Basin Development in the South Viking Graben, Offshore Norway
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Christopher Jackson, Karla Kane, Rachel Kieft and Gary Hampson, Department of Earth Sciences and Engineering, Imperial College, Prince Conosrt Road, London, SW7 2BP, England, UK
Eirik Larsen and Bruce Tocher, StatoilHydro ASA, Sandsliveien 90, Bergen, N5020, Norway
Rationale
Figure 1. Time-structure map of the Base Cretaceous Unconformity (BCU) illustrating the general structural style of the South Viking Graben and the location of major hydrocarbonfields/discoveries.The South Viking Graben (SVG) is a mature petroleum basin that still offers commercially significant exploration and field-development opportunities. In addition to existing producing fields, there are several discoveries ready for development and numerous exploration targets within several diverse plays; as such, the SVG is a core commercial area for StatoilHydro ASA (Fig. 1). Currently, in the Greater Sleipner area, the majority of production comes from Middle Jurassic and Palaeocene plays which are now reaching maturity. However, the Upper Jurassic syn-rift play, amongst others, can be considered grossly under-explored when compared to the UK side of the basin where several prolific fields are located (e.g. Brae, T-Blocks). This reflects, in part, the difficulty in predicting reservoir distribution and quality within the syn-rift interval in extensional basins such as the SVG. To meet this challenge, a multidisciplinary, geological study was initiated between Statoil ASA (now StatoilHydro ASA) and Imperial College in 2005.
Organization
Figure 2. Correlation of Middle Jurassic strata within the study area illustrating the control of salt-cored structural highs on the stratigraphic development of shallow marine reservoir sandstones.The funding of the project was unusual in that it was split 50:50 between the company’s exploration R&D programme and an exploration licence (PL303) which covers most of the area of interest. This method of funding ensured that the generic outcomes of the project could be appraised and disseminated by the research group, and that the applied aspects of the research could be rapidly utilised by the E&P group. The project was staffed at Imperial College by one Post-Doctoral Research Associate (PDRA) who focused on the tectono-stratigraphic development of the late syn-rift, and a PhD student who focused on the tectono-stratigraphic development of the early syn-rift succession. Key staff members in Statoil were charged with establishing and maintaining close links with researchers at Imperial College. In addition, these staff members provided rapid access to essential data hosted by Statoil and were critical in disseminating the results of the project to other staff members in confidential, licence-focused meetings. The collaborative project benefited from regular visits between the two groups, with the PDRA and PhD staff spending 4-6 week blocks ‘embedded’ in the offices of the production unit The project used a wide variety of data types including regional 2D and 3D seismic, and numerous exploration and production boreholes which contain detailed biostratigraphic and core data. Critically, researchers had virtually unlimited access to all these data.
Key Results & Future Developments
Figure 3. (A) Time-structure map of an intra-Jurassic reflection event illustrating the structural style of a Late Jurassic rift-related half-graben. Deep-water sediment input is inferred to be from the north. (B) Conceptual model for the deposition of deep-water turbidite (reservoir) sandstones adjacent to a salt-influenced fault-propagation fold. From a generic perspective, the research project indicated that the structural evolution of the South Viking Graben was complex and included the development of gravity-driven normal fault arrays above a regional salt detachment, and sub-salt basement-involved faulting which led to pronounced forced folding (or fault-propagation folding) in the cover stratigraphy. This structural development had a major impact on syn-rift depositional patterns both within early syn-rift shallow marine and late synrift deep marine strata. In particular, major thickness and facies changes occur in both shallow (Fig. 2) and deep marine (Fig. 3) sandstones adjacent to both active normal faults and large, salt-cored structural highs. From an applied perspective, research on the palaeogeographic evolution of the Middle Jurassic succession aided in reservoir prognosis prior to drilling of the Ermintrude prospect; this prospect was drilled and appraised during the middle part of 2007 and is estimated to contain ca. 75 MMBL. In addition, several exploration targets have been identified in the late syn-rift interval.
This study demonstrates that an integrated multidisciplinary study between academia and industry can generate new opportunities in a mature basin that has been explored for more than 30 years. In particular, geological predictions and risk evaluation have benefited greatly from this improved regional geological understanding. Key to the success of this project was the establishment of two clear aims at the study outset; (i) research results were to be business-focused and have an impact on business decisions; and (ii) the results would also need to assist in improving Statoil’s general understanding of the tectono-stratigraphic evolution of rift basins. Future projects utilising a similar funding model and with similar aims are currently being planned.