First Break - Current Issue

Few localities are as important as the outcrops of the remnants of the Alpine Tethys margins exposed in European Alps in the development of new concepts on the temporospatial evolution of magma-poor rifted margins. The Tasna and Err detachment systems are among the best exposed and preserved structures related to extreme crustal thinning and mantle exhumation world-wide. These detachment systems shaped the most distal parts of the fossil Alpine Tethys magma-poor rifted margins and are key analogues of present-day deep-water examples that can only be imaged through geophysical methods. We present the first digitalisation and integration of the Err and Tasna detachment systems using structure-from-motion photogrammetry. The resulting high-resolution models offer details down to 7 cm and cover multi-kilometre cross-sections from various angles. Comparing these 3D digital outcrop models with high-resolution seismic images from the Galicia distal margin allows us to constrain interpretations of the structures and processes that control the formation of distal passive margins. All data are openly available under FAIR (Findable, Accessible, Interoperable, and Reusable) conditions to the geoscientific community, and we hope this contribution will be the first of many that contribute to the ongoing digitalisation of key outcrops of the fossil Alpine Tethys margins in the European Alps.

A key step toward reducing the risks and uncertainties associated with hydrocarbon exploration in carbonate rocks is to assess the prospects of using multiple methods. Accordingly, I introduced and developed a novel template for fluid type discrimination and detection in the extended elastic impedance (EEI) domain based on well data and seismic data. To this end, fluid substitution modelling was performed by formulating different fluid type scenarios (brine, oil, and gas) to utilise a rock physics model with unlimited pore types. These scenarios were subsequently converted to EEI trends and expressed as functions of intercept-gradient coordinate rotation angle (χ angle) to form EEI templates. The obtained templates were successfully verified against well-log data at a blind well and also by ultrasonic measurements on core samples using a triaxial cell. Next, fluid type detection was performed on prestack migrated seismic data that was originally acquired over a real carbonate reservoir with complex pore types. For this purpose, a low-frequency model was built and wavelet extraction was performed at corresponding χ to obtain an EEI cube through inversion. The obtained results were interpreted considering the proposed template, leading to the delineation of the hydrocarbon-bearing zone. The results were further verified based on water saturation log at a blind well drilled on the basis of interpretation of seismic data, simultaneous inversion and the available geological information. A big advantage of the EEI template over conventional EEI analysis and simultaneous inversion is that it considers more than one window, which can provide for improved accuracy and reliability in fluid detection in carbonate rocks.

The greater Latin American region has a complex and diverse history of hydrocarbon exploration like other oil-rich areas. South America has a series of prolific and proven basins where the opportunity for operators is ever evolving. Many times, the successes of these efforts correlate with the maturity of exploration within the basin. A comparison of basins can be made to illustrate the basin’s exploration status, i.e.- frontier or mature. Commercial field distribution in the Guyana-Suriname Basin and the Salt Basins of Brazil indicates that legacy, shallow-water prospecting has been left behind for larger, more prospective targets in deep water realms. From seismic observations, frontier areas, such as the Equatorial Margin of Brazil and South America’s Austal South Atlantic margin segments, have a wide play fairway ahead in the deeper regions. Deep-water deposits have been demonstrated to commonly hold commercial field sizes where quality source rock is present. Overcoming technical and commercial risks in frontier basins is the key to a successful transition off-the-shelf into deep ‘sweet spot’ basins.