Spatial variability of Hurst statistics in the Castagnola Formation, Tertiary Piedmont Basin, NW Italy: discrimination of sub-environments in a confined turbidite system
Fabrizio Felletti, 2004. "Spatial variability of Hurst statistics in the Castagnola Formation, Tertiary Piedmont Basin, NW Italy: discrimination of sub-environments in a confined turbidite system", Confined Turbidite Systems, S. A. Lomas, P. Joseph
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The purpose of this paper is to investigate the potential of the use of the Hurst test as a statistical tool for quantifying the degree of clustering of high and low values of field measurements in vertical turbiditic sections within a small and confined tectonically mobile basin. The paper (1) documents the fact that significant clustering occurs in almost all sections, (2) shows that there are systematic spatial variations in the degree of clustering such that different parts of the basin have different Hurst statistics, (3) discusses the origin of those spatial trends, and (4) compares Hurst H with Chen and Hiscott's Hurst K. The case study focuses on one well-exposed reservoir-scale turbiditic unit cropping out in the eastern part of the Tertiary Piedmont Basin (NW, Italy) and representing the lower portion of an Upper Oligocene-Lower Miocene turbidite system (Castagnola Formation). The sedimentological model that has been adopted is based on the description of 41 sedimentological logs (approximately 25–35 m apart) physically correlated bed by bed. Three variables were studied: thickness of sandstones and siltstones, grain size score, and sand and silt thickness percentage (i.e. the ratio of coarse division to overlying mudstones, in percent). The Hurst test has revealed the existence of common clustering for the three studied variables (only 2 of 41 logs failed to pass the test at the 10% significance level for all the studied variables). This clustering is associated with lateral and vertical facies variations in response to changes in depositional sub-environments within the Castagnola Basin. A geostatistical analysis has been performed in order to estimate the spatial distribution of the Hurst statistics within the studied area. The analysis makes possible predictions at unsampled locations.
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This publication reflects a growing appreciation of the extent to which turbidite depositional system development is fundamentally affected by basin-floor topography. In the many turbidite and turbidite hydrocarbon reservoirs, depositional patterns have been moderately to strongly confined by pre-existing slopes; thus ‘submarine fans’ may be far from fan-shaped where constrained by significant bathymetric features. This volume examines aspects of sediment dispersal and accumulation in deep-water systems where sea-floor topography has exerted a decisive control on deposition, and explores the associated controls on hydrocarbon reservoir architecture and heterogeneity.
The papers presented here offer a global perspective, which is wide-ranging in terms of approach as well as location, including contrasting reviews and case studies of outcrop, subsurface, modern and experimental systems. This book will be of use both to academic geologists and to geoscience professionals in industry dealing with characterization and modelling of deep-water clastic reservoirs.