This study aimed to investigate the prediction method of permeability and its anisotropy of tight oil reservoir via precise pore-throat tortuosity characterization and “umbrella deconstruction” method combining the approaches of the field emission SEM imaging, high resolution image processing, fine and large-scale mathematical statistics, nonlinear regression and other technical means.

In this paper, the authors proposed the new calculation model of pore-throat tortuosity, the absolute permeability and the permeability anisotropy based on the improved deep understanding of reservoir. Results of the prediction on the tight oil reservoir of “YANCHANG” formation in Ordos Basin show that the errors of the new method in this paper are the smallest among the total five methods, respectively 0.023 × 10⁻³μm² and 0.090 × 10⁻³μm²; the average values of other four methods were 0.090 × 10⁻³μm² and 0.108 × 10⁻³μm², respectively. The predicted results have higher accordance with the measured results, which proved the practicality of the new method. The samples has the highest permeability at the angle of 0°(180°/360°) and the permeability values are equal to 0.25 × 10⁻³μm². Similarly, the sample has the lowest permeability at the angle of 22.5°(202.5°), 90°(270°), and 112.5°(292.5°), the permeability values are all equal to 0.06 × 10⁻³μm². At the same time, the calculation of permeability anisotropy results shows that the anisotropy of tight oil reservoirs is very significant, and the permeability value in one direction is obviously higher than which in other directions.

It is concluded that the precise description of pore throat geometry, especially the calculation of pore-throat tortuosity parameter, is one of the most important parameters affecting the prediction accuracy of permeability theoretically. Meanwhile, there are dominant seepage channels, which would play a very important guiding role in the prediction of hydrocarbon accumulation and seepage capacity.

The conclusion will provide a more rigorous theoretical basis for the rapid and accurate evaluation of the physical properties of unconventional reservoirs.