Fractal characteristics of pore structure of deep continental shale of Lower Wuerhe Formation in central Junggar Basin and its geological significance

2024

Youqi dizhi yu caishoulu, Vol 31, Iss 1, Pp 23-35 (2024)

In order to clarify the pore structure and fractal characteristics of the deep continental shale of the Lower Wuerhe Formation in the central Junggar Basin， the Lower Wuerhe Formation shale in the Dongdaohaizi Sag was taken as the research object. On the basis of an in-depth analysis of shale minerals and geochemical characteristics， the pore structure characteristics of the Lower Wuerhe Formation shale were quantitatively characterized by using field emission scanning electron microscopy and low-temperature N2 adsorption experiments. The fractal dimension of shale pores was calculated based on the FHH model， and the relationships among TOC content， mineral composition， pore structure parameters， fractal dimension， and its geological significance were revealed. The results show that the Lower Wuerhe Formation shale mainly develops inorganic pores and micro-fractures， and the pore size distribution is multi-peak type， mostly parallel plate or narrow slit pores. The pore development of shale is controlled by TOC and the content of quartz， feldspar， and clay minerals， which results in significant differences and strong heterogeneity among pore structures. Shale pores of the Lower Wuerhe Formation in the study area have double fractal characteristics， in which the surface fractal dimension D1 varies from 2.452 2 to 2.594 8， with an average value of 2.540 9. The fractal dimension D2 of the structure ranges from 2.604 5 to 2.774 8， with an average of 2.705 6. TOC is negatively correlated with fractal dimension， while pore structure parameters （specific surface area and pore volume） and mineral composition （quartz， feldspar， and clay mineral content） are positively correlated with fractal dimension. An increase in the content of brittle minerals such as quartz， feldspar and clay minerals contributes to the development of micro- and nano-scale pores and micro-fractures. This results in an increase in specific surface area， pore volume， and fractal dimension. As pore heterogeneity strengthens， the complexity of the pore structure also increases.

article

Chinese

Editorial Office of Petroleum Geology and Recovery Efficiency, 2024.

continental shale, microscopic pore structure, fractal characteristics, lower wuerhe formation, junggar basin, Chemical technology, TP1-1185, Petroleum refining. Petroleum products, TP690-692.5, Geology, QE1-996.5