1,721,219 research outputs found
Discrete fracture network modelling reconstructs fracture array evolution and related petrophysical properties over geological time
Full text linkFractured rock petrophysical studies rarely use temporal constraints, thus hindering fracture-related
permeability and connectivity estimation during past geofluid migration. Here wepresent a conceptual
approach, using a stochastic method incorporating absolute ages to reconstruct fracture arrays back
in geological time. Generating ‘grown’ discrete fracture network models, we simulate the hydraulic
behaviour of fractured rock volumes from the late-Cretaceous/Palaeocene to the Devonian, via
progressive fracture back-stripping. We reveal that for the examined rock mass, maximum principal
permeability increased through time from 9.47e-14m2 to 4.44e-13m2 (~3 orders of magnitude) along
with the maximum horizontal permeability orientation shifting from NE-SW to NW-SE. Similarly, the
connectivity metric increased with fracture saturation, peaking in the mid-Cretaceous. For
comparison, dated offshore hydrocarbon secondary migration potentially coincides with our results.
Back-stripping of time-constrained fracture sets is therefore a powerful method to investigate and
quantify the dynamic evolution of petrophysical properties through geological time
Sand fraction, organic carbon and nitrogen data, and calculated marine and terrestrial organic carbon fractions of surface sediments in the western Barents Sea
No full textThere is generally a lack of knowledge on how marine organic carbon accumulation is linked to vertical export and primary productivity patterns. In this study, a multi-proxy geochemical and organic-sedimentological approach is coupled with organic facies modelling focusing on regional calculations of carbon cycling and carbon burial on the western Barents Shelf between northern Scandinavia and Svalbard. OF-Mod 3D, an organic facies modelling software tool, is used to reconstruct the marine and terrestrial organic carbon fractions and to make inferences about marine primary productivity in this region. The model is calibrated with an extensive sample dataset and reproduces the present-day regional distribution of the organic carbon fractions well. Based on this new organic facies model, we present regional carbon mass accumulation rate calculations for the western Barents Sea.
The calibration dataset includes location and water depth, sand fraction, organic carbon and nitrogen data and calculated marine and terrestrial organic carbon fractions
Past and present natural methane seepage on the northern Norwegian continental shelf
Full text linkThis thesis represents an integrated research effort to understand past and present methane cycling on the northern Norwegian margin. Active hydrocarbon seeps in the Hola trough on the Vesterålen continental shelf are found to be fed predominantly by thermogenic methane (and ethane, propane and butane). Most likely derived from Late Jurassic to Early Cretaceous source rocks, these gaseous hydrocarbons migrate along major unconformities between the basement and the overlying Mesozoic sedimentary rocks. Most of the ascending methane is consumed by anaerobic oxidation of methane (AOM) at the sulphate methane transition (SMT) within the subsurface sediments.
A comparison of the carbon cycling in the surface sediments of the Vesterålen shelf seep site and organic rich sediments of a northern Norwegian fjord revealed distinctly different organic carbon sources, accumulation rates and turnover processes. The seep site is mainly influenced by carbon input via the rise of thermogenic methane rich-fluids, whereas the fjord site is completely dominated by marine organic matter deposition originating from primary production in the water column resulting in higher rates of organoclastic sulphate reduction and methanogenesis.
The study of methane-derived authigenic carbonates (MDACs) from the Hola seep site provided insight into formation environment and source fluids. The most important information derived from the MDACs are the temporal constraints of methane escape inferred from U-Th dating. Based on our present knowledge, methane seepage in the Hola trough started at least 11 ka ago, probably even slightly before. It seems likely that strongest events of past methane seepage and carbonate formation occurred around 10, 4 and 2 ka BP. The events may be tentatively correlated to seismicity events related to isostatic rebound of the lithospheric crust after retreat and melting of the Scandinavian ice sheet and local/regional earthquakes
Stable isotope analysis on sediment core PS2129-1
No full textStable isotope analysis on sediment core PS2129-
Sedimentology and geochemistry of core PS2123-2
No full textSedimentology and geochemistry of core PS2123-
Organic geochemistry of sediment core PS2123-3
No full textOrganic geochemistry of sediment core PS2123-
Organic geochemistry of sediment core PS2122-1
No full textOrganic geochemistry of sediment core PS2122-
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