- 1School of Geosciences in China University of Petroleum (East China), Qingdao 266580, China
- 2State Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao 266580, P. R. China
- 3Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals, Shandong University of Science and Technology, Qingdao 266590, P.R. China
Abstract: The micro- and nano-pores in organic-rich shale reservoirs significantly impact the exploration potential of unconventional oil and gas. To clarify the heterogeneity of pore size distribution and its influencing factors in organic-rich shales, this study was conducted on shale cores with significant gas logging anomalies from 1600-1680m, collected from a scientific drilling well in the South Yellow Sea Basin that penetrated the Permian strata. Nitrogen adsorption-desorption experiments, total organic carbon (TOC), X-ray diffraction, and scanning electron microscopy tests were carried out. Additionally, fractal theory was employed to characterize the heterogeneity and connectivity features of the pore structure. The results indicate that the average TOC of the selected samples is 5.99%, and the shale lithofacies are predominantly Siliceous shale, Clay shale, and Clay shale-Clay Mixed shale. The clay shale has the highest average specific surface area and pore volume, with averages of 5.54 m2/g and 9.37×10-3 cm3/g, respectively. The fractal dimensions D1 and D2 calculated using the single Frenkel-Halsey-Hill method are relatively independent. The multifractal box-counting method suggests that low-probability measure areas play a key role in the heterogeneity of the full-size pore size distribution. The generalized fractal dimension D(q) decreases with increasing q, and the singularity fractal spectrum exhibits a non-symmetric parabolic shape, indicating that the pores in organic-rich shales possess multifractal characteristics. An increase in TOC and clay mineral content enhances the overall heterogeneity of the pore structure, while an increase in calcareous mineral content improves pore connectivity. The multifractal model demonstrates a significant advantage in quantitatively characterizing the heterogeneity of pore structures in organic-rich shales, providing an important theoretical basis for shale gas exploration and development.
Key words: Organic-rich shale; Pore structure; Heterogeneity; Monofractal analysis; Multifractal analysis
How to cite: Wei, Z., Liu, H., Pang, Y., and Zhang, J.: The study on fractal theory to characterize the pore structure of organic-rich shale reservoirs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5873, https://doi.org/10.5194/egusphere-egu25-5873, 2025.
