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J C Rivenæs, StatoilHydro (Norway)
C Pedersen, StatoilHydro (Norway)
E M Nysæter, StatoilHydro (Norway)
J Dexter, StatoilHydro (Norway)
H E Eliassen, StatoilHydro (Norway)
J A Gjengedal, StatoilHydro (Norway)
I Lorentzen, StatoilHydro (Norway)
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The Troll field is extensive and covers approximately 45x60 km. The reservoir comprises a complex sequence of Upper Jurassic shoreface and heterolithic sands and includes 40 geological zones in the Sognefjord and Fensfjord formations. Seismic interpretation of 16 intra-reservoir reflectors is a huge challenge, both in terms of extent and vast dataset. This complexity, together with the thin oil column and large volume of horizontal well information, present unique challenges to the geomodelling of the field. Only through good collaboration between geophysists and geologists in the asset team, and with the use of some highly innovative technical solutions, has it been possible to develop a workflow that can produce a model suitable for well planning and simulation purposes, and is quite easy to update.
The reservoir zonation is based on a sequence stratigraphic scheme using sed/strat information from cores, seismic interpretation data and 4D seismic responses. It is importent that the seismic interpretation is fit for modelling purposes. By integrating these data into a series of automated workflows with some creative scripting, it has been possible to construct a platform for making multiple iterations of the model within a reasonable timeframe.
The challenge of adjusting the surfaces to the huge number of well zonation points was not possible to solve in a satisfactory manner using vendor software due to the horizontal nature and close spacing of the wells. A robust adjustment of the surfaces to the wells was instead achieved using XTGeo, an in-house program library. XTGeo also includes functionality for batch plotting multiple well sections to immediately allow the effects of the well adjustments vs the input data to be seen.
The development of an integrated workflow for the Troll stratigraphic model has provided the asset team with a much-needed tool to quickly update the model with new well information. The capacity of the workflow to handle large volumes of horizontal well data has also provided an ongoing means to improve the understanding of reservoir architecture.
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