Snorre Olaussen

Basin Evolution in Southern East Greenland: An Outcrop Analog for Cretaceous-Paleogene Basins on the North Atlantic Volcanic Margins

The Cretaceous-Paleogene Kangerlussuaq basin in southern East Greenland represents a unique outcrop analog for the frontier petroleum provinces along the deep-water volcanic margins of the northern North Atlantic. The 1-km-thick sedimentary succession comprises six facies associations: (1) alluvial plain and shallow marine (late Aptian?), (2) fluvio-estuarine (late Aptian-early Albian), (3) offshore marine (Late Cretaceous-early Paleocene), (4) submarine fan and channel-levee (early Paleocene), (5) fluvial (mid-Paleocene), and (6) volcanic (late Paleocene). Sedimentation was terminated in the late Paleocene by extrusion of flood basalts related to continental breakup. The basin fill is divided into two depositional megasequences related to regional tectonic events and sea level changes. The oldest megasequence (SQ1) spans the late Aptian to the earliest Paleocene with sea level rise in the late Aptian and maximum flooding in the late Albian-Cenomanian, followed by sea level highstand in the Late Cretaceous-early Paleocene. SQ1 is truncated by a basin-wide unconformity related to regional uplift and basin reorganization in the mid-Paleocene. The upper megasequence (SQ2) spans the mid- to late Paleocene and comprises sediments deposited during early sea level rise. Extensive volcanic deposits and continental flood basalts overlie it. Deep burial (> 6 km) and middle Eocene-early Oligocene(?) uplift excludes the Kangerlussuaq basin as a petroleum basin in itself; however, to evaluate the petroleum potential of similar volcanic influenced offshore basins, such as the West Shetland, Faeroe, More, and Voring basins, we discuss three conceptual play models based on the Kangerlussuaq basin: (1) early Albian stratigraphic trap, (2) early Paleocene structural trap, and (3) Paleocene stratigraphic trap.

The importance of natural fractures in a tight reservoir for potential CO2 storage: a case study of the upper Triassic–middle Jurassic Kapp Toscana Group (Spitsbergen, Arctic Norway)

Abstract In the Longyearbyen CO2 laboratory project, it is planned to inject carbon dioxide into a Triassic–Jurassic fractured sandstone–shale succession (Kapp Toscana Group) at a depth of 700–1000 m below the local settlement. The targeted storage sandstones offer moderate secondary porosity and low permeability (unconventional reservoir), whereas water injection tests evidence good lateral fluid flow facilitated by extensive fracturing. Therefore, a detailed investigation of fracture sets/discontinuities and their characteristics have been undertaken, concentrating on the upper reservoir interval (670–706 m). Datasets include drill cores and well logs, and observations of outcrops, that mainly show fracturing but also some disaggregation deformation bands in the sandstones. The fracture distribution has a lithostratigraphical relationship, and can be subdivided into: (A) massive to laminated shaly intervals, offering abundant lower-angle shear fractures; (B) massive to thin-bedded, heterogeneous, mixed silty–shaly intervals, with a predominance of non-systematic, pervasive bed-confined fractures; and (C) massive to laminated, medium- to thick-bedded, fine- to coarse-grained sandstones with a lower frequency of mostly steep fractures. These domains represent pseudo-geomechanical units characterized by specific fracture sets and fracture intensity, with indicated relationships between the bed thickness and fracture intensity, and with domains separated along bedding interfaces. We discuss the impact of these lithostructural domains on the fluid flow pathways in the heterolithic storage unit.

Sedimentology of the Lower Cretaceous at Kikutodden and Keilhaufjellet, southern Spitsbergen: implications for an onshore–offshore link

ABSTRACT Detailed sedimentological investigations of the Lower Cretaceous succession of southernmost Spitsbergen indicate deposition during a long-term fall and rise in relative sea level. The Rurikfjellet Formation shows an overall regressive development and consists of offshore deposits grading upwards into progradationally stacked shoreface parasequences. The overlying Helvetiafjellet Formation shows a two-fold division reflecting an overall transgressive development. The lower Festningen Member represents a lateral extensive sandstone sheet that was deposited in a braid plain setting with sediment dispersal to the south-east. The unit also includes a lower Barremian subaerial unconformity at its base, demonstrating that uplift and shelf erosion also took place in southern Spitsbergen. Clinoforms observed in seismic data from, amongst others, the Lower Cretaceous in the western Bjarmeland Platform suggest a potential link between the onshore unconformity and the offshore clinoforms. The Festningen Member is capped by a coaly shale unit that represents an expansion surface which marks a change into a high-accommodation distributary fluvial system of the overlying and heterolithic Glitrefjellet Member. The overall transgressive development recorded in the Helvetiafjellet Formation eventually resulted in a marine flooding that eroded and drowned the delta plain depositing an offshore mudstone unit, 5–10 m in thickness, that marks the re-establishment of open marine shelf conditions in the basal part of the Carolinefjellet Formation. The succeeding sand-rich part of the Carolinefjellet Formation contain abundant hummocky cross-stratified sandstones deposited in an inner shelf setting, and therefore represents renewed shoreline progradation onto the shallow subaqueous shelf.

Provenance shifts in an evolving Eurekan foreland basin: the Tertiary Central Basin, Spitsbergen

Detrital zircon U–Pb laser ablation inductively coupled plasma mass spectrometry age data for Paleocene and Eocene sandstones from the Central Tertiary Basin on Spitsbergen, Arctic Norway are used to investigate provenance and to test the filling history of the basin in response to the evolving Eurekan orogeny. The zircon age data from 16 analysed samples allow us to distinguish five sources. The zircon age populations of the Paleocene Firkanten and Basilika formations have a distinct Uralide signature (c. 275 Ma) and are interpreted to represent four mixtures of reworked Late Triassic, Jurassic and older sandstones affected by Early Cretaceous volcanism. The zircon age population of the Eocene Battfjellet Formation lacks Uralide- and Early Cretaceous-aged zircons and is dominated by Proterozoic and Archaean zircons indicating sourcing from Middle Triassic and older rocks. The data support models implying a marked shift from easterly to westerly source areas during the evolution of the basin in response to the evolving Eurekan orogeny. The population of Cretaceous-aged zircons indicates that volcanism in the High Arctic Large Igneous Province took place during two separate events at 80–100 and 118–150 Ma, thus supporting previous models for Cretaceous volcanic activity in the High Arctic. Supplementary materials: Operating conditions, data acquisition parameters and zircon discordances are available at https://doi.org/10.6084/m9.figshare.c.2187247.

Late Ordovician Trace Fossils from Offshore to Shallow Water Mixed Siliciclastic and Carbonate Facies in the Ringerike Area, Oslo Region, Norway

ABSTRACT Upper Ordovician (Rawtheyan–Hirnantian) deposits in the Ringerike area contain 21 ichnogenera of burrows and two ichnogenera of borings. These deposits consist of a lower siliciclastic part and an upper part dominated by carbonates and mixed clastic-carbonate deposits. Sedimentological and geochemical investigations combined with an ichnological analysis in the lower siliciclastic part point to a shallowing from a transitional–offshore partly dysoxic zone to an oxic delta front/upper shoreface facies. The trace fossils belong to the proximal, archetypal, and distal Cruziana ichnofacies. The upper part of the sequence comprises a complex pattern involving patch reefs interfingering with shallow marine deposits of sandstones and crinoidal limestones in the southern area and carbonate mud banks to the north. The carbonate mud banks were subaerially exposed with the development of local coastlines. The overlying transgressive sediments, consisting of sandstones and carbonates, contain an offshore to transitional trace fossil assemblage.

Depositional history of a condensed shallow marine reservoir succession: stratigraphy and detrital zircon geochronology of the Jurassic Stø Formation, Barents Sea

The Early to Middle Jurassic Stø Formation (Toarcian to Bajocian) was deposited in a relatively shallow (10 s of meter deep) epicontinental sea in northern Pangea and represents one of the most prolific reservoir intervals in the Barents Sea basin. It comprises a condensed, predominantly shallow marine succession characterized by long hiatuses and erosional reworking with several horizons of extraformational pebble grade conglomerate. Six distinct facies associations describe sedimentological environments ranging from transgressive, tidal, fluvial and regressive shoreface. Deposits are interpreted and correlated within three sequence stratigraphic units (SI to SIII) which reflect variations in relative sea-level during an overall transgression of the basin. Interpreted depositional systems show subtle variations in petrographic character, but provenance analyses reveal different sedimentary sources. Thirteen core samples distributed geographically and stratigraphically were analysed for detrital zircon U-Pb geochronology. Data show that the Southwestern Barents Sea Basin (SWBSB) was dominated by mixing of reworked material and coarse grained sediment supply from extrabasinal source areas including a Caledonian provenance in the southwest and a Fennoscandian provenance to the southeast. Intra-basinal erosion of underlying strata with Triassic zircon grains dominate in northern parts of the basin. Supplementary material: Supporting information relating to the analysis of different dataset and the interpretations presented in the paper are available at https://doi.org/10.6084/m9.figshare.c.3841282.

Thermal maturity, hydrocarbon potential and kerogen type of some Triassic–Lower Cretaceous sediments from the SW Barents Sea and Svalbard

Rock-Eval and total organic carbon (TOC) analyses of 144 samples representing Triassic–Lower Cretaceous intervals from the SW Barents Sea (the Svalis Dome, the Nordkapp and Hammerfest basins, and the Bjarmeland Platform) and Svalbard demonstrate lateral variations in source rock properties. Good to excellent source rocks are present in the Lower–Middle Triassic Botneheia and Steinkobbe, and Upper Jurassic Hekkingen formations, 1 – 7 wt% and 6 – 19 wt% TOC, respectively. Hydrogen indices of 298 – 609 mg HC/g TOC in the Botneheia Formation from Svalbard, and 197 – 540 mg HC/g TOC in the Steinkobbe Formation of Svalis Dome suggest Type II (oil-prone) and Type II/III (oil/gas-prone) kerogens, respectively. The Kobbe Formation (Botneheia/Steinkobbe-equivalent) is organic-lean and generally gas-prone (Type III kerogen) on the Bjarmeland Platform and in the Nordkapp Basin, and is a good source rock with Type III/II kerogen in the Hammerfest Basin. In the investigated wells, the Hekkingen Formation is more oil-prone on the Bjarmeland Platform than in the Nordkapp Basin, while Lower Cretaceous samples have poor potential for oil. Upper Triassic samples show potential mainly for gas; however, coal/coaly-shale samples in well 7430/07-U-01 (Bjarmeland Platform) are oil/gas-prone. Most samples analysed are immature to early mature; thus, the variation in petroleum potential and kerogen type is a function of organic facies rather than maturity levels.

The theropod that wasn't: an ornithopod tracksite from the Helvetiafjellet Formation (Lower Cretaceous) of Boltodden, Svalbard

Abstract We re-examine a Lower Cretaceous dinosaur tracksite at Boltodden in the Kvalvågen area, on the east coast of Spitsbergen, Svalbard. The tracks are preserved in the Helvetiafjellet Formation (Barremian). A sedimentological characterization of the site indicates that the tracks formed on a beach/margin of a lake or interdistributary bay, and were preserved by flooding. In addition to the two imprints already known from the site, we describe at least 34 additional, previously unrecognized pes and manus prints, including one trackway. Two pes morphotypes and one manus morphotype are recognized. Given the range of morphological variation and the presence of manus tracks, we reinterpret all the prints as being from an ornithopod rather than a theropod, as previously described. We assign the smaller (morphotype A, pes; morphotype B, manus) to Caririchnium billsarjeanti. The larger (morphotype C, pes) track is assigned to Caririchnium sp., differing in size and interdigital angle from the two described ichnospecies C. burreyi and C. billsarjeanti. The occurrence of a quadrupedal, small to medium-sized ornithopod in Svalbard is puzzling, considering the current palaeogeographical reconstructions and that such dinosaur tracks have mainly been described from Europe but not North America.

Integrated Characterization of an Organic-rich Caprock Shale, Svalbard, Arctic Norway

Both thermogenic and biogenic gas were encountered during scientific drilling on Svalbard, Arctic Norway. The thermogenic gas has been encountered in an interval at 650-703 m depth, spanning both the lower part of the caprock, an organic-rich shale unit with subordinate siltstone intervals, and the upper part of the siliciclastic reservoir targeted for CO2 storage. Both water injection tests and gas flow tests were conducted to establish the formation injectivity and production capability of this interval. In this contribution, we investigate the organic rich shale interval in detail, integrating well data with direct observations on outcrop analogues, to present a conceptual model of the reservoir-cap rock interface.

Basement–cover reservoir analogue in rift-margin fault blocks; Gulf of Suez Rift, Sinai, Egypt

Faults, fracture systems, weathering profiles and cover sediments of granitic basement in the rift shoulder of the Gulf of Suez Rift (Sinai, Egypt) are useful conceptual analogues for basement–cover reservoir fields. Outcrops demonstrate that fracture intensity peaks adjacent to major faults, and declines in damage zones that stretch to the background fracturing level over distances of 150 m. In the rift shoulder, smaller faults have damage zones that are 30 – 40 m wide with 1 – 5 m-wide fracture corridors. Faults show chemical alteration extending hundreds of metres into basement, with characteristics similar to saprolite in schists, mafic rocks and granitoids. Cover sandstones fill and drape top-basement relief, as recorded by metre-thick basal fluvial coarse sandstones, hosting kaolinite both as diagenetic pore fill and clastic grains. Overlying floodplain to marginal-marine deposits consist of mature quartz arenites. Strategies for production of hydrocarbons or groundwater from basement–cover reservoir couplets should consider a layered system with: (i) deep tight basement of minimal porosity (c. 1%) hosting producible fractures and faults in a plumbed system with potential thief zones; (ii) top-basement weathering profiles capping granitoids representing a volumetrically considerable reservoir; and (iii) draping cover sandstones showing good reservoir properties, and representing the most homogenous unit. Diagenetic modifications of saprolite, fault rocks and fractures potentially baffle recharge between layers.