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Sankt Stefan ob Leoben, Austria

Reitner J.M.,Geologische Bundesanstalt | Gruber W.,HOT Engineering | Romer A.,Geologische Bundesanstalt | Morawetz R.,Joanneum Research
Swiss Journal of Geosciences | Year: 2010

We present a study of the inneralpine basin of Hopfgarten focused on the analysis of basin fill in order to reveal its formation in relation to paleo-ice flow and tectonics. The study is based on geological mapping as well as seismic (reflection and refraction) and geoelectrical surveys. The oldest sequence in the basin, identified by seismic stratigraphy at 400 m below surface, consists of coarse grained sediments of supposedly Oligocene to Miocene age, which subsided along faults linked to the Inn fault. Three superimposed sequences, each displaying baselaps in contact with a subglacially formed unconformity and sigmoid foresets, show pleniglacial conditions followed by a glaciolacustrine environment. The uppermost of these three sequences lies on top of last glacial maximum till (LGM; Würmian Pleniglacial; MIS 2) and represents Termination I. The middle sequence is classified as Termination II following the Rissian Pleniglacial (MIS 6). The oldest glacial sequence cannot be constrained chronostratigraphically but might correlate with Termination V following the major glaciation of MIS 12. Limited glacial erosion during the LGM occurred only during the ice build-up phase. Further overdeepening was impeded due to topographic barrier and mutual blockades of glaciers within this highly dissected landscape. The occurrence and relative timing of the impediment was controlled by the onset of transfluences and thus by the altitude of coles. The higher amount of overdeepening during older glacial periods is explained by longer phases of free ice advance in the ice build up phase due to higher transfluences routes at that time. Thus, the preservation of older Pleistocene sequences within the basin may be the result of the lowering of watersheds from one glaciation to the next. Our model of an inverse relationship between glacial shaping of the surface and the subsurface may apply to similar Alpine landscapes as well. © 2010 Swiss Geological Society.

Cubitt C.J.,HOT Engineering | Gruber W.,HOT Engineering | Stummer B.C.,HOT Engineering | Allottai O.,Akakus Oil Operations
73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 | Year: 2011

The depositional settings of the late Ordovician Mamuniyat Formation in the central part of the Murzuq basin, Libya were investigated using a combination of core (>2300′), wireline and image logs. The resulting interpretation was transformed for modelling purposes into a simplified semi-automated facies log and was then spatially rendered as gross depositional environment maps; both inputs for the resulting 3D facies model. Previous outcrop studies focussed on the Ghat and Gargaf areas (north and west of study area) differ in the interpretation of the Lower Mamuniyat. This study interprets the Lower Mamuniyat sandstones as sub-marine, deposited in a shallow marine shelf (lack of bioturbation and sharp juxtaposition of black marine shales with massive sandstones) in contrast to a deltaic deposition as interpreted in previous outcrop studies to the north. Facies on image logs and distinctive log responses enabled palaeogeographic reconstruction. Further up section, the Middle Mamuniyat was deposited in a deltaic setting emerging from the south, grading into a turbiditic setting towards the north, agreeing with the Ghat and Gargaf outcrop studies. The Upper Mamuniyat sediments are regarded as having formed on a braid delta with the ubiquitous truncated sediment packages reflecting the erosional nature of such a depositional system.

Gruber W.,HOT Engineering | Cubitt C.J.,HOT Engineering | Stummer B.C.,HOT Engineering | Allottai O.,Akakus Oil Operations
73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 | Year: 2011

The Mamuniyat Formation holds a number of producing hydrocarbon fields in SW-Libya. Its deposition is related to the Ordovician glaciation and thus inherits complicated stratigraphic and facies relationships. The study outlines a seamless workflow on the integration of core based facies analysis into a 3D reservoir model in this complex glacial environment. The workflow established in this study enabled the comingling of a high number of fluvial/deltaic to glacio-marine litho-facies into a susinct number of depositional environments which were then further refined into eight electro-facies categories which were able to be then effectively modelled. In essence the simplistic reservoir models produced captured all of the geological complexity as observed in core. A 3D facies model was developed from facies logs and constrained by seismic attributes and conceptual depositional environment maps. Fully fluvial environments (Upper Mamuniyat) and entirely marine environments (Lower Mamuniyat) were realized as classical object models. The interpreted transition from a coastal setting via shoreface into a marine setting in the Middle Mamuniyat was captured in a two step approach jointing Truncated Gaussian Simulation and object modeling. The resulting facies model is the base for property modeling, volume estimations and field development planning of the studied reservoir.

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