analytical tools based on separation techniques coupled with mass spectrometry are contributing to both approaches. The first step in every analytical process is developing a clear and complete definition of the objective of the analysis, which will define the type of sample, the number of samples, the groups to be compared, and many other factors. As this step is quite case dependent, we will focus on the following steps: (i) recent developments in sample collection and preparation, (ii) recent developments in analytical tools, and (iii) new trends in data mining strategies and in the identification of compounds. Data interpretation, which is also a key part of both metabolomics and analytical processes, will not be included due to limitations on the length of the manuscript.

Goodman, A., Sanguinito, S., Kutchko, B., Natesakhawat, S., Cvetic, P., Allen, A.J., 2020. Shale pore alteration: Potential implications for hydrocarbon extraction and CO storage. Fuel 265, 116930. 2

http://www.sciencedirect.com/science/article/pii/S0016236119323233 Shale unconventional reservoirs are currently and expected to remain substantial fossil fuel resources in the future. As CO is being considered to enhance oil recovery and for storage purposes in unconventional 2 reservoirs, it is unclear how the shale matrix and fractures will react with CO and water during these efforts. 2 Here, we examined the Utica Shale and its reactivity with CO and water using scanning electron microscopy, 2 N and CO sorption isotherms, mercury intrusion porosimetry, and X-ray scattering methods. During CO 2 2 2 exposure, the presence of water can inhibit CO migration into the shale matrix, promote carbonate dissolution, 2 and dramatically change the pore scale variability by opening and closing pore networks over the macro- to nano-scale range. These alterations in the shale matrix could impact flow pathways and ultimately, oil recovery factors and carbon storage potential.

Goral, J., Panja, P., Deo, M., Andrew, M., Linden, S., Schwarz, J.-O., Wiegmann, A., 2020. Confinement effect on porosity and permeability of shales. Scientific Reports 10, 49.

https://doi.org/10.1038/s41598-019-56885-y Porosity and permeability are the key factors in assessing the hydrocarbon productivity of unconventional (shale) reservoirs, which are complex in nature due to their heterogeneous mineralogy and poorly connected nano- and micro-pore systems. Experimental efforts to measure these petrophysical properties posse many limitations, because they often take weeks to complete and are difficult to reproduce. Alternatively, numerical simulations can be conducted in digital rock 3D models reconstructed from image datasets acquired via e.g., nanoscale-resolution focused ion beam - scanning electron microscopy (FIB-SEM) nano-tomography. In this study, impact of reservoir confinement (stress) on porosity and permeability of shales was investigated using two digital rock 3D models, which represented nanoporous organic/mineral microstructure of the Marcellus Shale. Five stress scenarios were simulated for different depths (2,000 - 6,000 feet) within the production interval of a typical oil/gas reservoir within the Marcellus Shale play. Porosity and permeability of the pre- and post-compression digital rock 3D models were calculated and compared. A minimal effect of stress on porosity and permeability was observed in both 3D models. These results have direct implications in determining the oil- /gas-in-place and assessing the production potential of a shale reservoir under various stress conditions.

Gordin, Y., Hatzor, Y.H., Vinegar, H.J., 2020. Anisotropy evolution during early maturation of organic-rich carbonates. Journal of Petroleum Science and Engineering 188, 106946.

http://www.sciencedirect.com/science/article/pii/S0920410520300449 The organic-rich Late Cretaceous carbonates of the Ghareb and Mishash formations are potentially both self- sourced unconventional reservoirs and high quality source rocks for conventional petroleum systems in the eastern Mediterranean region. In this study we use cores from depths ranging from 340 to 1290 min the Shefela and Golan Heights basins in Israel, which records the diagenesis and transformation phases of organic-rich chalk into limestone. Understanding such source rocks is complicated by the fact that each formation is unique