International Geologiical Congress - Oslo 2008

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GEP-20 Outcrop studies: Fundamental to petroleum reservoir characterization and modeling

 

Sedimentology and geomodelling of small scale fluvial architecture from the Lourinhã formation, Portugal

 

Anneli Ekeland, StatoilHydro ASA (Norway)
Nina Pedersen, Odin Petroleum (Norway)
John Howell, University of Bergen (Norway)
Wojtec Nemec, University of Bergen (Norway)
Kevin Keogh, StatoilHydro ASA (Norway)
 

 

The importance of fluvial rocks as reservoirs is widely recognized in the petroleum industry and StatoilHydro has a large portfolio in such reservoirs. Predicting the occurrence and distribution of barriers and baffles in fluvial sandbodies has proven to be a difficult task even with extensive well log and core databases available. Understanding the bed-scale architecture in three dimensions and the effect that they have on the reservoir behaviour is typically over-looked in fluvial systems that are modelled as simple channel shaped objects in overbank (non-reservoir) facies. The use of outcrop analogues for addressing subsurface problems is a well established method of tackling reservoir issues. This study investigated three well exposed, outcropping fluvial channels from the Lusitanian Basin in Portugal.

The results presented in this paper are based on data collected from embayments south of Peniche, Portugal extending down to Lourinhã. Large amounts of sedimentological and stratigraphical data have been collected and three datasets of photo-montages, logs and bed-to-bed correlation have been generated.

The study revealed that several types of fluvial systems have been active during the late Jurassic in the area. While many of the sandbodies display characteristics typical for meandering systems, some channel complexes included a predominance of lateral and side attached bars. Determining the architectures in the outcrop allowed key, intra-channel surfaces to be reconstructed. These were used as input for building three small-scale, detailed geomodels that illustrate the detailed macroform and facies architecture. Results achieved in this analogue study can be imported into the subsurface reservoir in order to improve the understanding of small-scale bed geometries and dimensions.

 

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