Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting research articles in the latest issue of Geophysics. Here is a list of what piqued the editors’ interests.

Origin of shallow gas in the Dutch North Sea - Seismic versus geochemical evidence

In the Dutch offshore, we have observed numerous acoustic anomalies, usually bright spots, in seismic data of Cenozoic deltaic deposits. When associated with shallow gas, these bright spots are good indicators of resource potential, drilling hazard, or seabed methane emissions. We apply a combined seismic and petrophysical assessment to qualify the bright spots as direct hydrocarbon indicators (DHIs) for shallow gas and to exclude alternative sources of seismic anomalies. In some cases, we use other DHIs such as flat spots, velocity push-downs, transmission, and attenuation effects as estimators for gas saturation. A long-standing discussion concerns the sourcing and migration of shallow gas. Although vertical seismic noise trails (chimneys) tend to be seen as proof that shallow gas originates from the migration of deeper sourced thermogenic gas, the geochemical and isotope analyses almost exclusively indicate that the gas is of microbial origin and generated in situ in the Cenozoic strata. We conclude that the observed “chimneys” are most likely transmission effects, that is, artifacts that do not represent migration pathways of gas. Hence, we believe that for the Dutch offshore, the presence of shallow biogenic gas is not indicative of leakage of deeper thermogenic petroleum plays and cannot be used as an exploration tool for these deeper targets.

List of Analogues for Highly Productive Rocks Around Salt Domes

In the Dnipro-Donets depression, the Devonian salt during Carboniferous time became movable and created salt domes in the Permian, moving to the sea bottom and flowing therewith, forming bodies visible today as salt canopies and overhangs. These features are clear pieces of evidence of salt exposure on the surface, especially considering belts of reservoirs around salt domes. These reservoirs can be extremely prolific in some wells. Previous exploration targeting such deposits was driven mainly by drilling wells within the areas of known deep fields such as Medvedivske, Zakhidno-Khrestyschenske and others in the central part of the DDB. These reservoirs are composed of poorly sorted coarse material of wide variety of rocks including sandstones, carbonates, dolomites, igneous rocks of deep (granites), and shallow (diabases) formations. Currently, with the availability of 3D seismic surveys, these deposits become visible as bright spots and flat spots. Although it is not a 100% indicator due to fact that shallow salt canopies and lithology changes of rocks around salt domes may also interpret seismic reflections. It is good to mention that the Permian is an aridic environment with gradually losing water influx to the basin from base to top within the thickness of more than 1-2 kilometers. It could be utilized as boundary analogues to cover most of the possible intermediate scenarios in three areas. The first analogue is the outcropped salt dome in Solotvyno village in Carpathian mountains in western Ukraine close to the Romania border. This salt dome is an important example of showing the current deposition of transported coarse material from depth around salt domes. The second one is salt domes exposed as mountains of the Oman desert where it is possible to follow the material path approaching the salt uplift. And the third example is the Death Valley in Arizona, USA. The valley is an example of fans mostly deposited by gravity rather than permanent water flows. It good to mention that there are more examples that could be treated as direct analogues (the Zagros mountains in Iran) but they are not easily accessible for field trips if needed. For recognizing real targets vs artifacts, applying the knowledge of current deposition examples around the world would help dramatically (Western Ukraine, Oman, Death Valley in Arizona).

The State of Democracy in Africa and the Middle East 2021: Resilient Democratic Aspirations and Opportunities for Consolidation

Recent declines in democracy have undermined some of the remarkable progress made in Africa over the past three decades, although bright spots remain. The Covid-19 pandemic, though seemingly less damaging to public health than elsewhere in the world, has added pressure on governance, rights, and social inequality. The report also covers the Middle East and North Africa which is one of the least democratic regions in the world. The Covid-19 pandemic has reinforced the erosion in democratic principles and the deepening authoritarianism that has accompanied a decade of economic, social and political turmoil in the region. This Report provides lessons and recommendations that governments, political and civic actors, and international democracy assistance providers should consider in order to counter the concerning trends in the erosion of democracy, and to foster its resilience and deepening.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting research articles in the latest issue of Geophysics. Here is a list of what piqued the editors' interests.

Evaluation of MODIS-derived estimates of the albedo over the Atacama Desert using ground-based spectral measurements

Surface albedo is an important forcing parameter that drives the radiative energy budget as it determines the fraction of the downwelling solar irradiance that the surface reflects. Here we report on ground-based measurements of the spectral albedo (350–2200 nm) carried out at 20 sites across a North–South transect of approximately 1300 km in the Atacama Desert, from latitude 18° S to latitude 30° S. These spectral measurements were used to evaluate remote sensing estimates of the albedo derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). We found that the relative mean bias error (RMBE) of MODIS-derived estimates was within ± 5% of ground-based measurements in most of the Atacama Desert (18–27° S). Although the correlation between MODIS-derived estimates and ground-based measurements remained relatively high (R= 0.94), RMBE values were slightly larger in the southernmost part of the desert (27–30° S). Both MODIS-derived data and ground-based measurements show that the albedo at some bright spots in the Atacama Desert may be high enough (up to 0.25 in visible range) for considerably boosting the performance of bifacial photovoltaic technologies (6–12%).