Significance of large-scale sand injectites as long-term fluid conduits: evidence from seismic data

Authors


Corresponding author: Andrew Hurst, Department of Geology amd Petroleum Geology, Kings College, University of Aberdeen, Aberdeen AB24 9UE, UK.
E-mail: a.hurst@abdn.ac.uk

Abstract

Sand injectites and related features that are interpreted to have formed by large-scale, often sudden, fluid escape in the shallow (typically <500 m) crust are readily imaged on modern seismic data. Many of the features have geometrical similarity to igneous dykes and sills and cross-cut the depositional stratigraphy. Sand injectites may be multiphase and form connected, high-permeability networks that transect kilometre-scale intervals of otherwise fine-grained, low-permeability strata. North Sea examples often form significant hydrocarbon reservoirs and typically contain degraded, low-gravity crude oil. Fluid inclusion and stable isotope data from cements in sand injectites record a mixing of aqueous fluids of deep and shallow origin.

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