A cyclostratigraphic framework of the Upper Carboniferous Westoe and Cleaver formations in the southern North Sea Basin as a methodology for stratigraphic reservoir characterisation
T. F. Baars, Richard Huis in ‘t Veld, Linzhi Zhang, Maaike Koopmans, D. McLean, A. Martinius, H. Abels
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引用次数: 0
Abstract
Abstract Orbital driven climate control on sedimentation produces regional, stratigraphically repetitive characters and so cyclostratigraphic correlation can improve correlation and identify stratigraphic trends in borehole sections. This concept is commonly used to correlate marine and lacustrine strata. However, in the alluvial domain, its use is more challenging because internal, local dynamics controlling sedimentation may interfere with the expression of cyclic climate forcing. Intervals of low net-to-gross may be important for successful application in this domain as they tend to better document regional changes. This study applies climate-based stratigraphic correlation concepts to improve well correlations, characterise vertical sand distribution, and identify potential reservoir targets in a generally low net-to-gross interval. Coarsening upward sedimentary repetitions (cyclothems) are identified and correlated with high certainty in nineteen well sections in the upper Carboniferous Westoe and Cleaver formations of the Silverpit Basin. Local sedimentary dynamics provide variability in the character of the cyclothems and several types of cyclothem are classified. Correlation of sections using cyclothems recognised on wireline logs is done twice: once manually and once semi-automatically. The semi-automated correlation is based on calculation of deviation curves which depict stratigraphic changes that are less dependent on absolute wireline values and follow vertical trends more clearly. The correlations provide composite stratigraphies that are analysed using vertical proportions curves. Both approaches yield similar results in terms of stratigraphic trends. However, for detailed correlation of wells, the manual correlation is better at accounting for any local variability within the system. The same two zones of higher net-to-gross ratios are found using both correlation methods. These are linked to palaeoclimatic changes driven by long eccentricity and the proposed climate stratigraphic model has predictive value for identifying sandstone occurrence. The climate-based stratigraphic correlation improves the assessment reservoir distribution and properties on small (10–20 m thickness) and large (100–200 m thickness) stratigraphical scales.
期刊介绍:
Netherlands Journal of Geosciences - Geologie en Mijnbouw is a fully open access journal which publishes papers on all aspects of geoscience, providing they are of international interest and quality. As the official publication of the ''Netherlands Journal of Geosciences'' Foundation the journal publishes new and significant research in geosciences with a regional focus on the Netherlands, the North Sea region and relevant adjacent areas. A wide range of topics within the geosciences are covered in the journal, including "geology, physical geography, geophyics, (geo-)archeology, paleontology, hydro(geo)logy, hydrocarbon exploration, modelling and visualisation."
The journal is a continuation of Geologie and Mijnbouw (published by the Royal Geological and Mining Society of the Netherlands, KNGMG) and Mededelingen Nederlands Instituut voor Toegepaste Geowetenschappen (published by TNO Geological Survey of the Netherlands). The journal is published in full colour.