Exploro AS

Trondheim, Norway

Exploro AS

Trondheim, Norway

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Hammer E.,Statoil | Hammer E.,Lundin Norway AS | Brandsegg K.B.,Exploro AS | Mork M.B.E.,Norwegian University of Science and Technology | Naess A.,Statoil
Petroleum Geoscience | Year: 2012

A new methodology for robust, high-resolution correlation of reservoir sandstones in highly compactable depositional sequences is proposed. Quantitative sequential re-burial modelling has been successfully applied on real data from seven wells covering the heterogeneous fluviodeltaic Åre Formation in the Heidrun Field, offshore mid-Norway. The methodology is based on ten interpreted lithofacies classes derived from core descriptions and wireline logs signatures, in addition to interpreted sequence stratigraphic surfaces, i.e. flooding surfaces. Analysis of decompacted sedimentary columns, with emphasis on studies of shallow compaction effects tied to uniquely calculated compaction curves, has revealed several new correlatable horizons within the Åre Formation. These include laterally extensive coals and several laterally correlatable fluvial sandstones enabling a reinterpretation of parts of the Åre stratigraphy. The results from the present study demonstrate the benefits of correcting for the effects of differential compaction in well-to-well correlation of heterogeneous reservoirs comprising highly compactable sediments. The methodology outlined here has widespread applicability to other stratigraphic successions and could potentially help in the correlation of highly compacted sediments in the subsurface. © 2012 EAGE/Geological Society of London.


Ottesen D.,Exploro AS | Dowdeswell J.A.,University of Cambridge | Bugge T.,Det norske oljeselskap ASA
Marine and Petroleum Geology | Year: 2014

The North Sea Basin has been subsiding during the Quaternary and contains hundreds of metres of fill. Seismic surveys (170000km2) provide new evidence on Early Quaternary sedimentation, from about 2.75 Ma to around the Brunhes-Matuyama boundary (0.78 Ma). We present an informal seismic stratigraphy for the Early Quaternary of the North Sea, and calculate sediment volumes for major units. Early Quaternary sediment thickness is>1000m in the northern basin and >700m in the central basin (total about 40000km3). Northern North Sea basin-fill comprises several clinoform units, prograding westward over 60000km2. Architecture of the central basin also comprises clinoforms, building from the southeast. To the west, an acoustically layered and mounded unit (Unit Z) was deposited. Remaining accommodation space was filled with fine-grained sediments of two Central Basin units. Above these units, an Upper Regional Unconformity-equivalent (URU) records a conformable surface with flat-lying units that indicate stronger direct glacial influence than on the sediments below. On the North Sea Plateau north of 59°N, the Upper Regional Unconformity (URU) is defined by a shift from westward to eastward dipping seismic reflectors, recording a major change in sedimentation, with the Shetland Platform becoming a significant source. A model of Early Quaternary sediment delivery to the North Sea shows sources from the Scandinavian ice sheet and major European rivers. Clinoforms prograding west in the northern North Sea Basin, representing glacigenic debris flows, indicate an ice sheet on the western Scandinavian margin. In the central basin, sediments are generally fine-grained, suggesting a distal fluvial or glacifluvial origin from European rivers. Ploughmarks also demonstrate that icebergs, derived from an ice sheet to the north, drifted into the central North Sea Basin. By contrast, sediments and glacial landforms above the URU provide evidence for the later presence of a grounded ice sheet. © 2014 The Authors.


Ottesen D.,Exploro AS | Dowdeswell J.A.,University of Cambridge | Rise L.,Geological Survey of Norway | Bugge T.,Det norske oljeselskap ASA
Geological Society Special Publication | Year: 2012

About 3 million years ago, major ice sheets developed over Scandinavia and began to deliver large volumes of sediment to the mid-Norwegian shelf. The shelf was built out in a prograding pattern towards the west, and more than 1000 m of sediments was deposited over large areas on the middle/outer shelf. The dominating large-scale depositional pattern is a series of prograding wedges and flat-lying, sheet-like units mainly of glacial origin. On top of these units are flatlying till units deposited during the last few glaciations, commonly separated from the underlying units by one or several erosional unconformities. The lithology of these layers is generally finegrained, mainly clay and silt, but with sporadic clasts up to boulder size. Based on regional and detailed bathymetry, the ice-flow pattern from the last glaciation has been reconstructed on the shelf. This involved a very dynamic ice sheet with fast-flowing ice streams in the transverse, cross-shelf troughs, separated by more passive ice domes on the intermediate shallow banks. The ice streams appear to follow the cross-shelf troughs from glaciation to glaciation, but occasionally they switched to new flow paths. The thick Quaternary sediments on the outer part of the mid- Norwegian shelf represent a challenge for hydrocarbon exploration. Several large slides have occurred from the shelf break and down the continental slope. During the last few years there has been an increased focus on investigating the Quaternary succession in order to search for hydrocarbon prospects. The potential for finding reservoirs in these sediments is discussed, and a few examples of gas discoveries are shown. The Peon gas field (c. 250 km2) is located in the glacially eroded Norwegian Channel above the Upper Regional Unconformity (URU) separating flatlying glaciogenic sediments from dipping sedimentary units. The reservoir is developed in glaciofluvial sands a few hundred thousand years old, and sealed by flat-lying glaciomarine sediments and till units. © The Geological Society of London 2012.


Hall A.M.,University of St. Andrews | Ebert K.,University of Stockholm | Kleman J.,University of Stockholm | Nesje A.,University of Bergen | Ottesen D.,Exploro AS
Geology | Year: 2013

Glaciated passive margins display dramatic fjord coasts, but also commonly retain plateau fragments inland. It has been proposed recently that such elevated, low-relief surfaces on the Norwegian margin are products of highly efficient and extensive glacial and periglacial erosion (the glacial buzzsaw) operating at equilibrium line altitudes (ELAs). We demonstrate here that glacial erosion has acted instead to dissect plateaus in western Norway. Low-relief surfaces are not generally spatially associated with cirques, and do not correlate regionally with modern and Last Glacial Maximum ELAs. Glacier dynamics require instead that glacial erosion is selective, with low-relief surfaces representing islands of limited Pleistocene erosion. Deep glacial erosion of the coast and inner shelf has provided huge volumes of sediment (70,000 km3), largely resolving apparent mismatches (65-100,000 km3) between fjord and valley volumes and Pliocene-Pleistocene sediment wedges offshore. Nonetheless, as Pleistocene glacial valleys and cirques are cut into preexisting mountain relief, tectonics rather than isostatic compensation for glacial erosion have been the main driver for late Cenozoic uplift on the Norwegian passive margin. © 2013 Geological Society of America.


Napoli G.,University of Palermo | Nigro F.,Italian National Institute of Geophysics and Volcanology | Favara R.,Italian National Institute of Geophysics and Volcanology | Renda P.,University of Palermo | And 2 more authors.
Journal of Geodynamics | Year: 2015

The Sicilian fold-and-thrust belt is located in the central Mediterranean area, and it represents the south-eastern arcuate segment of the Apennine-Maghrebide orogen. The tectonic evolution of the Sicilian belt is documented after outcrop analysis of small-scale structural features carried out throughout the region. Results are consistent with the following four main deformation stages having affected the study area, from the oldest to the youngest: (i) multilayer weakening; (ii) folding-and-thrusting, (iii) extension, and (iv) renewed thrusting. The first deformation stage included three different substages (layer-parallel shortening, bed-parallel simple shear and fold nucleation), the second one by both thrusting and fold amplification and tightening. The third deformation stage involved re-activation of the pre-existing mechanical discontinuities and formation of low-to-high angle normal faults. Out-of-sequence thrusting postdated the aforementioned extensional stage, and formed the latest orogenic deformation stage that affected the Sicilian belt. © 2015 Elsevier Ltd.


Brandsegg K.B.,Norwegian University of Science and Technology | Brandsegg K.B.,Exploro AS | Hammer E.,Norwegian University of Science and Technology | Sinding-Larsen R.,Norwegian University of Science and Technology
Natural Resources Research | Year: 2010

Multivariate analysis is employed to investigate the structure of variations within highly heterogeneous data. Traditionally, principal component analysis (PCA) is run by analyzing the entire wireline log and using PCA scores to characterize variability within and between lithologies. In this paper, we propose a technique using only specific subsets of all well records to quantify reservoir heterogeneity due to second order lithological variability. These subsets are chosen from uniform lithofacies parts of the wireline log in order to reduce the variability in the correlation matrix that otherwise would cause lithological changes. The purpose is to assess the efficiency of structured PCA in analyzing small-scale heterogeneity that is captured by wireline logs but often masked by traditional PCA approaches. This paper shows that a structured PCA procedure based upon special lithological units is superior to an unstructured PCA, when the focus is within lithology variations. This structured procedure is applied to data from the Heidrun field, offshore mid-Norway. The results demonstrate clear benefits from added insight into the variability of a complex fluviodeltaic heterolithic sequence that poses great challenges to hydrocarbon development. © 2010 International Association for Mathematical Geology.


Marello L.,Geological Survey of Norway | Marello L.,Norwegian University of Science and Technology | Marello L.,Exploro AS | Ebbing J.,Geological Survey of Norway | And 2 more authors.
Geophysical Journal International | Year: 2013

We present a new 3D geophysical model for the Barents Sea that highlights the basement properties and crustal setting. The model results from the modelling of gravity and magnetic field anomalies and is based on a large number of seismic and petrophysical data. The set up consists of a water layer, sedimentary units that incorporate density variations associated with depth and time of deposition (Cretaceous-Cenozoic, Triassic-Jurassic, Late Palaeozoic and deeply buried sediments), upper and lower basement and an upper mantle. The upper crust is considered as the major source of the magnetic anomalies and has been divided into a number of units characterized by constant densities and magnetization, which show a good correlation with the main structural elements of the Barents Sea. The Southwest Barents Sea crust is an aggregation of allochthonous Caledonian terranes and autochthonous Archaean and Palaeoproterozoic complexes. We interpret the different crustal blocks in terms of distinctive lower, middle, upper and uppermost allochthonous terranes that can be linked with the major nappes onshore. The largest part of the North Barents Sea is distinguished from the rest of the shelf by its low-magnetic properties and its large crustal thickness. These differences are compatible with a geodynamic scenario in which an independent crustal block (Barentsia, not corresponding entirely to the island of Svalbard) was located between Baltica and Laurentia and became attached to the shelf during the Caledonian orogeny. To the east, the basement underlying the large mega-sag East Barents Basin, is an assemblage of Precambrian rocks deformed during the Timanian and Uralian orogenies. The basement is characterized by an alternation of high-magnetic and low-magnetic units that mimic the arcuate shape of Novaya Zemlya. In the Southeast Barents Sea, the crustal units are linked to the onshore geology of the Timan-Pechora region and are mostly the result of Timanian orogenesis. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.


Buried linear to curvilinear depressions, interpreted as iceberg ploughmarks, were identified through most of the 2. Ma-long and about 700. m thick early Quaternary sedimentary record in two 3D seismic cubes from the central North Sea Basin (56-58°N, 2-3°E). The mean width of 402 features measured at 6 time slices in cube C08 was between 49 and 63. m and mean length was 2.5 to 3.7. km. Mapping the <. 2.75. Ma old base-Quaternary horizon enabled the approximate shape of the central North Sea Basin to be estimated. The basin provided accommodation space for sediments, delivered in part by glacial processes from Scandinavia and northern Britain and from European rivers during the Quaternary. Images of seismic time slices of the chaotic and irregular features found in these sediments are similar to multibeam swath-bathymetric images of iceberg ploughmarks from modern polar shelves. The buried features indicate drifting icebergs in the central North Sea Basin through most of the early Quaternary. Lack of iceberg ploughmarks in the last few hundred thousand years of the North Sea Basin record suggests that by the Middle/Late Quaternary the basin was largely sediment filled. The iceberg source was probably an early Quaternary Scandinavian ice sheet extending intermittently onto the westward prograding shelf of western Norway. N-S orientated ploughmarks indicate iceberg drift from the north and a W-E component suggests iceberg circulation within the basin. By analogy with maximum thickness of modern icebergs, water depths were <. 600. m at most when ploughing took place. © 2013 The Authors.

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