The nature and significance of sand intrusions in a hydrocarbon-rich fold and thrust belt; Eastern Carpathians Bend Zone, Romania

Sand intrusions are commonly associated with hydrocarbon-bearing clastic reservoirs and they can host a significant part of the reserves. They modify the depositional sandbody architecture, and can have an impact on the petroleum system elements. Their significance and complex architecture is diffic...

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Bibliographic Details
Published in:	Journal of the Geological Society Vol. 177; no. 2; pp. 343 - 356
Main Authors:	Tamas, Alexandra, Tamas, Dan Mircea, Krezsek, Csaba, Schleder, Zsolt, Palladino, Giuseppe, Bercea, Razvan
Format:	Journal Article
Language:	English
Published:	Oxford Geological Society of London 01-03-2020 The Geological Society of London Geological Society Publishing House
Subjects:	Architecture Carpathians Cenozoic clastic dikes clastic rocks Compression connectivity contraction Deep water Eastern Carpathians Eastern Carpathians Bend Zone Europe faults folds fractures geometry Hydrocarbons Intrusion intrusions Kliwa Sandstone lower Miocene Miocene Moldavia Mountains Neogene Oligocene Outcrops overpressure Paleogene Petroleum planar bedding structures Poiana Copaceni Romania reservoir rocks Reservoirs Rocks Romania Sand sand bodies sand intrusions Sandstone sed rocks, sediments Sedimentary petrology Sedimentary rocks sedimentary structures Shale siliciclastics Sills soft sediment deformation Southern Europe Structural geology Tarcau Nappe Tectonics Teleajen Valley Tertiary Valea Rea
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Summary:	Sand intrusions are commonly associated with hydrocarbon-bearing clastic reservoirs and they can host a significant part of the reserves. They modify the depositional sandbody architecture, and can have an impact on the petroleum system elements. Their significance and complex architecture is difficult to assess in the subsurface due to limited resolution of seismic or core data. Outcrop analogues are key to better understand these complex reservoirs. In the Eastern Carpathians Bend Zone, the Oligocene and Lower Miocene succession offer spectacular exposures of deep-water siliciclastic rocks modified by remobilisation and sand intrusion processes. These rocks are also present in producing fields in this area. Sills can be as thick as the depositional sandstones (∼4 m), and sill-dominated outcrops can provide a net-to-gross (net sandstone to shale ratio) of about 35-50%. We quantified their architecture, in a study of the timing and mechanism of emplacement, their relationship to regional tectonics and their impact on reservoir connectivity. The intrusions are interpreted to be syn-tectonic, related to the major mid-Miocene compression in this part of the Carpathian Mountain Belt. The intrusions lead to a large increase in vertical and horizontal connectivity. Our results will help to improve reservoir characterisation and production in these reservoirs.
ISSN:	0016-7649 2041-479X
DOI:	10.1144/jgs2019-107