A Methodological Approach to Clastic Injectites: From Field Analysis to Seismic Modeling—Examples of the Vocontian Aptian and Albian Injectites (Southeast France)
Published:January 01, 2007
Olivier Parize, Bernard Beaudoin, Jean-Michel Champanhet, Gérard Friès, Patrice Imbert, Richard Labourdette, Benoît Paternoster, Jean-Loup Rubino, Frédéric Schneider, 2007. "A Methodological Approach to Clastic Injectites: From Field Analysis to Seismic Modeling—Examples of the Vocontian Aptian and Albian Injectites (Southeast France)", Sand Injectites: Implications for Hydrocarbon Exploration and Production, Andrew Hurst, Joseph Cartwright
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Hardly detected with logs and recognized with difficulty on cores, clastic injectites (sills and dikes) can be troublemakers in oil-field development. Moreover, they provide a precious record of early fracturation.
To predict their geometry, extension, and relationship to their feeders, field analysis of selected analog outcrops is conducted to propose some simple rules. In southeast France, the Aptian–Albian formation provides exceptional outcrops (Bevons, Rosans, and Nyons) where it is possible to characterize large sets of injectites: dikes and sills are associated in the same metric-to-kilometric network. The injection occurred per ascensum (more frequently) or per descensum, during or after the sand deposition. Specific geometric-based field methods have been developed to analyze the geometry based on the best conditions.
A three-dimensional (3-D) model of the Rosans area injectite network has been built through gOcad™ tool using outcrop analysis and an original, very high-resolution twodimensional seismic acquisition (0.6 km2; 0.23 mi2). This field analysis, the seismic survey, and the 3-D modeling provide some keys to consider possible occurrences of injectites and associated facies related to a turbiditic channel fill.
We dedicate this article to the memory of our colleagues and friends G. P. Allen and D. Claude.
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Sand Injectites: Implications for Hydrocarbon Exploration and Production
Sand injectites are described in scientific literature as an increasingly common occurrence in hydrocarbon reservoirs, in particular in deep-water clastic systems, where they are known to influence reserves distribution and recovery. Seismically-detectable injected sand bodies constitute targets for exploration and development wells and, subseismic sand bodies provide excellent intra-reservoir flow units that create field-wide vertical communication through depositionally extensive, low-permeability units. As sand injectites form permeable conduits in otherwise low-permeability units they facilitate the expulsion of basinal fluids; hence they act both as a seal risk and mitigate timing and rate of hydrocarbon migration. Injected sand bodies form intrusive traps, which are distinct from structural or stratigraphic traps. Included in this publication are 10 chapters on subsurface examination of sand injectites, 1 chapter on theoretical considerations, and 13 outcrop analogs in reservoirs across the world. Captured in this volume is at least a taste of the global and stratigraphic distribution of sand injectites, and an attempt to introduce readers to sand injectites and their significance in the context of hydrocarbon exploration and production. The book is not intended as a complete review of the field-based literature, but emphasizes high quality case studies from the surface and subsurface. The geographic scope of the book is large, and illustrates the diversity of geological settings in which these fascinating and economically significant features are found.