bottom waters during MREI resulted in a higher accumulation of marine-sourced organic matter, as indicated 13 by lower C/N ratios and higher δ C values compared with those of MREs II and III. Sediments deposited TOC during MREI have relatively low total REE contents, which may be related to reduced REE adsorption on Mn oxyhydroxides. However, the absence of Ce anomaly at MRE I is more likely due to the detrital input that obscures the original Ce anomaly. In the MREIII sediments, a weak negative Eu anomaly relative to that in the 3+ 2+ MREI and II may be attributed to the reduction of Eu to Eu under strongly reducing conditions that caused by intense methane seepage. These observations demonstrate that fluid flow may have an important effect on the distribution of both organic matter and REEs in methane-rich marine sediments.

Chen, L., Lu, Y., Li, J., Guo, X., Jiang, S., Luo, C., 2020. Comparative study on the Lower Silurian Longmaxi marine shale in the Jiaoshiba shale gas field and the Pengshui area in the southeast Sichuan Basin, China. Geosciences Journal 24, 61-71.

https://doi.org/10.1007/s12303-019-0014-y The Jiaoshiba shale gas field and Pengshui area are both located in the southeast Sichuan Basin with only 100 km apart. Although these two areas obtained shale gas flow from the Lower Silurian Longmaxi marine shale, there is a huge difference of production in these two areas where the Jiaoshiba shale gas field is more productive than the Pengshui area. In order to figure out the reason that caused this difference, this study analyzed the Longmaxi marine shale in these two areas by using drilling cores, and mineralogical and geochemical data. The results show that the Jiaoshiba shale gas field has a higher quality shale reservoir (higher content of quartz, higher porosity, higher permeability and higher TOC (Total Organic Carbon)) in the Lower Silurian Longmaxi Formation than that of the Pengshui area. The Lower Silurian Longmaxi marine shale in the 3 Jiaoshiba shale gas field contains a higher total gas content (3.65 m /ton in average) than that of the Pengshui 3 area (1.19 m /ton in average). Through structure analysis, this study found that the Jiaoshiba shale gas field and the Pengshui area located in the different tectonic units. The Jiaoshiba shale gas filed is located in the East Sichuan fold belt (wide spaced anticlines area) at the west side of the Qiyue mountain fault where less fractures are developed and the pressure coefficient is more than 1.5, resulting in much more free gas preserved in the shale reservoirs in the Lower Silurian Longmaxi Formation (the ratio of free gas content and absorbed gas content is 1.6), while the Pengshui area is located in the Hunan-Hubei-Guizhou thrust belt area at the east side of the Qiyue mountain fault where much more fractures are developed and the pressure coefficient is less than 1.0, leading to less free gas preserved in the Longmaxi marine shale (the ratio of free gas content and absorbed gas content is 0.6), that is why the shale reservoir in the Pengshui area has a lower total gas content than that in the Jiaoshiba shale gas field.

Chen, Chen, L., Yang, J., Wu, L., 2020. Modeling the dispersion of dissolved natural gas condensates from the incident. Journal of Geophysical Research: Oceans 124, 8439-8454.

https://doi.org/10.1029/2019JC015637 Abstract: An Iranian tanker with 136,000 tons of natural gas condensates collided with a freighter in the East China Sea in January 2018 and, after drifting ablaze for 8 days and over 200 km, capsized on the edge of the shelf near the Kuroshio Current. Different from the crude oil, the condensates consist of hydrocarbons that have relatively high solubility in seawater. We postulate that the leakage from the remaining condensate cargo at 110 mdepth may result in a bottom layer of condensate-enriched water in the vicinity of the resting tanker. A model is constructed in this study to simulate the dispersion of contaminated water through the processes of oceanic advection, diffusion, biodegradation, and volatilization. It is found that the scope and magnitude of the dispersion are most sensitive to the biodegradation. Even though the biodegradation time scale depends on several factors that are not well quantified in this region, using any value within the estimated range from a previous study results in significant contamination in the broad area. The dispersion is particularly effective in this incident because the tanker capsized near the Kuroshio Current -a fast-moving western boundary current. The Kuroshio acts as a fast conduit to spread the contaminant to the east coast of Japan and the interior Pacific Ocean. In addition, we identify that the Tsushima Warm Current, a perennial flow into the Japan Sea, is the second major conduit for spreading the polluted water. This study indicates that dissolved hydrocarbons are the main environmental risk for maritime spills of natural gas condensates.