Description: The combined passive and active seismic TRANSALP experiment produced an unprecedented high-resolution crustal image of the Eastern Alps between Munich and Venice. The European and Adriatic Mohos (EM and AM, respectively) are clearly imaged with different seismic techniques: near-vertical incidence reflections and receiver functions (RFs). The European Moho dips gently southward from 35 km beneath the northern foreland to a maximum depth of 55 km beneath the central part of the Eastern Alps, whereas the Adriatic Moho is imaged primarily by receiver functions at a constant depth of about 40 km. In both data sets, we have also detected first-order Alpine shear zones, such as the Helvetic detachment, Inntal fault and Sub-Tauern ramp in the north. apart from the Valsugana thrust, receiver functions in the southern part of the Eastern Alps have also observed a north dipping interface, which may penetrate the entire Adriatic crust [Adriatic Crust Interface (ACI)]. Deep crustal seismicity may be related to the ACI. We interpret the ACI as the currently active retroshear zone in the doubly vergent Alpine collisional belt.

Description: Oil-producing sills are commonly considered atypical reservoirs, although they can hold significant exploration potential. The need for a better understanding of fracture properties and petroleum system characteristics for this and similar igneous rock plays is the main motivation of our study. We explore the evolution of this play type by an analysis of the Los Cavaos oil field, located in the Malargue fold belt of the Neuquen Basin, Argentina, integrating multiscale fracture data from outcrops and subsurface. The field was created by a combination of intrusions and mild Miocene-Pliocene inversion. Production stems from thick cavity zones in naturally fractured andesitic sills emplaced in Upper Jurassic shale source rocks. Orientation patterns, fracture spacing, and length of fracture sets in the sill are consistent over several orders of magnitude. Large multiply connected and weakly cemented fractures are responsible for excellent interconnectedness in the reservoir. Fracture density is correlated with fault proximity, indicating a cogenetic evolution during active deformation. Abundant fractures in core with strike-slip to oblique striations support transpressional overprint during and after fracture formation. Although it is challenging to separate cooling from tectonic fractures, we propose two phases of fracturing, marked by a coexistence of subvertical and oblique fractures together with transpressional striae. Petrographic evidence suggests initial local oil expulsion and migration through microfractures, with opening displacements of 0.01 to 1 mm, followed by subsequent charging of the evolving intrasill cavity system as well as the bulk fracture system during cooling and mild deformation. We suggest that the observed patterns may be extrapolated to sills in similar geotectonic settings.

Description: This 1D/2D petroleum system modelling study intended to reconstruct the temperature, maturation, migration and accumulation history within the „Tight Gas Area“ on the southern edge of the Pompeckj Block in northern Germany. To better understand hydrocarbon migration and to generate a more reliable predictive model of reservoir characteristics, we integrated detailed information from (i) sedimentological analysis of core and log data, and (ii) a structural reconstruction of the Rotliegend reservoir horizons. One cross section and 12 wells were examined using the 1D/2D simulation software PetroMod® 7.1 of IES GmbH, Jülich; subsequently the results of the 1D modelling were incorporated in the 2D model. The W-E section connects well-known gas fields of the Nordhannover concession and runs perpendicular to the prevalent N-S striking horst-and-graben structures within the Paleozoic rocks. The depth to the major source rocks within the area, the coal-bearing Westphalian strata, varies between 5800 m and around 4700 m in some areas (e.g. Top Westphalian B). Along the section, a pre-Permian erosion of between 400 to 1200 m of Upper Carboniferous sediments was assumed, the actual amount depending on the position relative to horst and grabens. During the Upper Carboniferous and the Rotliegend the temperatures within Westphalian B and Lower Westphalian C sediments remained below 100°C and 75°C, respectively. The temperatures within these sediments increased by about 50°C, before they decreased again to 125°C and 100°C, respectively, due to the Late Jurassic inversion. During on-going burial in the Upper Cretaceous, temperatures rose until they reached their present-day values of about 175°C in Lower Westfalian C, 210°C in Westfalian B, and more than 250°C in Namurian C sediments. According to the temperature history, the maturation of organic matter within these rocks occurred in two important stages. During the Triassic, vitrinite reflectance reached values of 1.5% and 1.0% in Westphalian B and Lower Westphalian C sediments, respectively. The second period of intense maturation was coeval with enhanced subsidence during the Upper Cretaceous, when vitrinite reflectance within Westfalian B and C sediments increased from to 3.0% and about 2.2%, respectively. Maturity within the horst block sediments remained lower by about 1.0%. Within Westphalian B sediments gas generation started during the Middle Triassic and lasted until the Late Tertiary. These rocks became overmature whilst Lower Westfalian C rocks generated gas until the present time and transformed 60-90% of their convertible kerogen into hydrocarbons, the actual amount depending on the structural position. During the Jurassic and the Triassic, when the regional stress field allowed N-S striking faults to be dilatant and to act as migration pathways, high gas columns along the fault zones led to a breakthrough and loss of gas, where thinned Zechstein salt exists.