A new method for evaluating the oil mobility based on the relationship between pore structure and state of oil.

[Display omitted] • New method established to evaluate oil movability based on shale pore structure and oil states. • The method overcomes the limitation of pyrolysis that cannot provide pore space information. • The method provided novel way to determine the T 2-cutoff for adsorbed and free shale oil. • Two parameters measuring the shale oil movability proposed. An accurate evaluation of the shale oil mobility is crucial to its cost-effective exploitation. This study presents a method to assess shale oil mobility by integrating the pore structure and oil states distributions. First, a set of three discrete organic extracts (EOM-A, B and C) were obtained by sequential extraction. The relationships among the EOMs and the oil states were inferred from the group compositions and fluorescence properties of the produced shale oil (free state). The results showed that EOMs A and B represent free oil in the open and closed pores, respectively, while the EOM-C represents adsorbed oil. Then, NMR T 1 -T 2 map is used to determine the T 2-cutoff values that indicate the pore size ranges of different oil states. Free oil resides mainly in larger pore space (T 2 > 0.5 ms), while the adsorbed oil in smaller pore space (0.2 ms < T 2 < 0.5 ms). Finally, the ratio of free to adsorbed oil (F/A) > 0.5 and T 2-cutoff > 1.0 ms suggest that the free oil in connected pores has the highest mobility. This work can provide a reference for evaluating the shale oil potential and prospectivity in other regions. [ABSTRACT FROM AUTHOR]