Methane emissions from gas hydrate deposits along continental margins may alter the biogeophysical properties of marine environments, both on local and regional scales. The saturation of a gas hydrate deposit is commonly calculated using the elastic or electrical properties measured remotely or in-situ at the site of interest. Here, we used a combination of controlled-source electromagnetic (CSEM), seismic and sediment core data obtained in the Nyegga region, offshore Norway, in a joint elastic-electrical approach to quantify marine gas hydrates found within the CNE03 pockmark. Multiscale analysis of two sediment cores reveals significant differences between the CNE03 pockmark and a reference site located approximately 150 mnorthwest of CNE03. Gas hydrates and chemosynthetic bivalves were observed in the CNE03 sediments collected. The seismic velocity and electrical V resistivity measured in the CNE03 sediment core are consistent with the P-wave velocity ( ) and resistivity P V values derived from seismic and CSEM remote sensing datasets, respectively. The gradually increases P (~1.75 - 1.9 km/s) with depth within the CNE03 pipe-like structure, whereas the resistivity anomaly remains ~3 Ωm. A joint interpretation of the collocated seismic and CSEM data using a joint elastic -electrical effective medium model suggests that for the porosity range 0.55 - 0.65, the gas hydrate saturation within the CNE03 hydrate stability zone varies with depth between ~20 and 48%. At 0.6 porosity, the hydrate saturation within CNE03 varies between ~23 and 37%, whereas the weighted mean saturation is ~30%. Our results demonstrate that a well-constrained gas hydrate quantification can be accomplished by coupling P-wave velocity and CSEM resistivity data through joint elastic-electrical effective medium modelling. The approach applied in this study can be used as a framework to quantify hydrate in various marine sediments.

Azevedo, V., Stríkis, N.M., Santos, R.A., de Souza, J.G., Ampuero, A., Cruz, F.W., de Oliveira, P., Iriarte, J., Stumpf, C.F., Vuille, M., Mendes, V.R., Cheng, H., Edwards, R.L., 2019. Medieval climate variability in the eastern Amazon-Cerrado regions and its archeological implications. Scientific Reports 9, 20306.

https://doi.org/10.1038/s41598-019-56852-7 The South American Monsoon System is responsible for the majority of precipitation in the continent, especially over the Amazon and the tropical savannah, known as 'Cerrado'. Compared to the extensively studied subtropical and temperate regions the effect of the Medieval Climate Anomaly (MCA) on the precipitation over the tropics is still poorly understood. Here, we present a multiproxy paleoprecipitation reconstruction showing a consistent change in the hydrologic regime during the MCAin the eastern Amazon and 'Cerrado', characterized by a substantial transition from humid to drier conditions during the Early (925 - 1150 C.E.) to Late-MCA (1150-1350 C.E.). We compare the timing of major changes in the monsoon precipitation with the expansion and abandonment of settlements reported in the archeological record. Our results show that important cultural successions in the pre-Columbian Central Amazon, the transition from Paredão to Guarita phase, are in agreement with major changes in the hydrologic regime. Phases of expansion and, subsequent abandonment, of large settlements from Paredão during the Early to Late-MCA are coherent with a reduction in water supply. In this context we argue that the sustained drier conditions during the latter period may have triggered territorial disputes with Guarita leading to the Paredão demise.

Babadagli, T., 2020. Philosophy of EOR. Journal of Petroleum Science and Engineering 188, 106930.

http://www.sciencedirect.com/science/article/pii/S0920410520300292 This paper seeks answers, through a 'philosophical' approach, to the questions of whether enhanced oil recovery projects are purely driven by economic restrictions (i.e. oil prices) or if there are still technical issues to be considered, making companies refrain from enhanced oil recovery (EOR) applications. Another way of approaching these questions is to ask why some EOR projects are successful and long-lasting regardless of substantial fluctuations in oil prices. To find solid answers to these two, by 'philosophical' reasoning, further questions were raised including : (1) has sufficient attention been given to the 'cheapest' EOR methods such as air and microbial injection, (2) why are we afraid of the most expensive miscible processes that yield high recoveries in the long run, or (3) why is the incubation period (research to field) of EOR projects so lengthy? After a detailed analysis using sustainable EOR example cases both answers to these questions and supportive data were sought.