Subsurface sediment remobilization and fluid flow in sedimentary basins: an overview Mads Huuse, n Christopher A.-L. Jackson, w Pieter Van Rensbergen, z Richard J. Davies, ‰ Peter B. Flemings, z and Richard J. Dixonk n Basin Studies Group, School of Earth, Environmental and Atmospheric Sciences,The University of Manchester, Manchester, UK wDepartment of Earth Science & Engineering, Imperial College, London, UK zShell International E&P, Rijswijk, the Netherlands ‰Centre for Research into Earth Energy Systems (CeREES), Department of Earth Sciences, Durham University, Durham, UK zJackson School of Geosciences,The University of Texas at Austin, Austin,TX, USA k BP Exploration, Sunbury ^ Upon ^ Thames, Middlesex, UK ABSTRACT Subsurface sediment remobilization and £uid £ow processes and their products are increasingly being recognized as signi¢cant dynamic components of sedimentary basins.The geological structures formed by these processes have traditionally been grouped into mudvolcano systems, £uid £ow pipes and sandstone intrusion complexes. But the boundaries between these groups are not always distinct because there can be similarities in their geometries and the causal geological processes. For instance, the process model for both mud and sand remobilization and injection involves a source of £uid that can be separate from the source of sediment, and diapirism is now largely discarded as a deformation mechanism for both lithologies. Both mud and sand form dykes and sills in the subsurface and extrusive edi¢ces when intersecting the sediment surface, although the relative proportions of intrusive and extrusive components are very di¡erent, with mud volcano systems being largely extrusive and sand injectite systems being mainly intrusive. Focused £uid £ow pipes may transfer £uids over hundreds of metres of vertical section for millions of years and may develop into mud volcano feeder systems under conditions of su⁄ciently voluminous and rapid £uid ascent associated with deeper focus points and overpressured aquifers. Both mud and sand remobilization is facilitated by overpressure and generally will be activated by an external trigger such as an earthquake, although some mud volcano systems may be driven by the re-charge dynamics of their £uid source. Future research should aim to provide spatio-temporal ‘injectite’stratigraphies to help constrain sediment remobilization processes in their basinal context and identify and study outcrop analogues of mud volcano feeders and pipes, which are virtually unknown at present. Further data-driven research would be signi¢cantly boosted by numerical and analogue process modelling to constrain the mechanics of deep subsurface sediment remobilization as these processes can not be readily observed, unlike many conventional sediment transport phenomena. INTRODUCTION The subsurface remobilization and injection of mud and sand has been documented from every kind of basin on every continentworldwide (Fig.1). Sediment remobilization events are associated with signi¢cant £uid movement and the resultant sand and mud intrusions in the subsurface exert a strong control on £uid £ow in the sedimentary sequences they inhabit for millions of years following the injection event (see Milkov, 2000: Fig. 1; Van Rensbergen et al . (eds), 2003; Cartwright et al ., 2007; Hurst & Cartwright (eds), 2007). Understanding £uid £ow and storage is key to e⁄cient and safe hydrocarbon exploration and to the under- standing of the dynamics of sedimentary basin evolution (Harrison & Summa, 1991). By impacting the distribution and architecture of porous and permeable lithologies, remo- bilization and injection of clastic materials has implications for hydrocarbon exploration and production by impacting distribution and e⁄ciency of migration, reservoir, trap and seal, and may pose signi¢cant drilling hazards and imaging problems (see Heggland, 1997, 1998, 2004; papers in Van Rensbergen et al . (eds), 2003 and this volume). EAGE Correspondence: Mads Huuse, Basin Studies Group, School of Earth, Environmental and Atmospheric Sciences,The University of Manchester, Manchester M139PL, UK. E-mail: mads.huuse@ manchester.ac.uk Basin Research (2010) 22, 342–360, doi: 10.1111/j.1365-2117.2010.00488.x r 2010 The Authors Journal Compilation r Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists 342