Predicting the Distribution of Shallow Marine Facies Within Halokinetically Controlled Basins: Insights From the Upper Jurassic Fulmar Formation, UKCS

Abstract

Sedimentary successions influenced by halokinesis have been well documented in the continental and deep marine realms, however sedimentary successions deposited in shallow marine environments have received relatively little attention, despite their economic importance. Facies distribution for typical shallow marine siliciclastic successions have been well studied, but these models don't account for halokinetic driven changes in deposition, where salt withdrawal can enhance basin subsidence, or salt-wall uplift can create topographic barriers to sediment transport paths. Enhancing this understanding will provide the basis for the construction of depositional models which can aid the prediction of reservoir quality and facies juxtaposition, both within the salt basins and between them where applicable. The Upper Jurassic Fulmar Formation of the Central North Sea has been a major play fairway since the discovery of the Fulmar Field in 1975, resulting in 60 discoveries and 43 fields. The succession represents the deposition of shallow marine sediments into collapse basins formed above dissolving salt walls, that are scoured from adjacent Mesozoic mini-basin sediments. The distribution and facies of these sediments were controlled by the complex interplay of basin-scale tectonics, combined with active salt migration and dissolution. Here we present an integrated study that utilizes core and wireline logs to develop depositional models that can be used to predict facies distribution within these basins. Core based studies and facies analysis, focusing predominantly on ichnofabric analysis are used to develop facies associations that enable direct correlation between core and wireline data. This correlation between facies associations and wireline data has provided the basis for a basin-scale correlation and the identification of potential reservoir units. This multidisciplinary study provides a facies correlation tool that can be applied to the Fulmar Formation and other salt-influenced shallow marine successions, allowing for the development of exploration tools that enable the prediction of facies distribution both within and between halokinetically controlled basins.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017