Insights into Pore Structure and Fractal Characteristics of the Lower Cambrian Niutitang Formation Shale on the Yangtze Platform, South China

Abstract

Shales from the Lower Cambrian Niutitang Formation of Yangtze Platform have been widely investigated due to its shale gas potential. To better illustrate the pore structure and fractal characteristics of shale, a series of experiments were conducted on outcrop samples from the Lower Cambrian Niutitang Formation on Yangtze Platform, including X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and low-temperature nitrogen adsorption. Frenkel-Halsey-Hill (FHH) model was adopted to calculate the fractal dimensions. Furthermore, the relationships between fractal dimensions and pore structure parameters and mineral composition are discussed. FE-SEM observation results show that interparticle pores are most developed in shale, followed by intraparticle pores. This study identified the fractal dimensions D1 (ranging from 2.558 0 to 2.710 2) and D2 (ranging from 2.541 5 to 2.765 2). The pore structure of the Niutitang Formation shale is primarily controlled by quartz and clay content. Fractal dimensions are able to characterize the pore structure complexity of Niutitang Formation shale because D1 and D2 correlate well with average pore diameter and quartz content.

Keywords

Niutitang Formation / Yangtze area / shale / pore structure / fractal features

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