Fracture energy evolution and fractal characteristics of shales with different quartz contents

Abstract

Quartz is an important mineral component of shale. In order to explore the influence of quartz content on the mechanical properties of shale, this article conducted numerical simulation of the Lower Cambrian Niutitang Formation shale in Fenggang Block 3, Guizhou using RFPA software. The results show that the effect of quartz content on compressive strength is more significant than that on elastic modulus. The damage modes of shale with different quartz content are presented as 5 types, namely, oblique tension damage (21%, 27%), inverted N-shaped damage (33%), V-shaped damage (39%), inverted V-shaped damage (45%), and λ-shaped damage (51%). When the content of quartz is higher than a certain value, the microscopic damage of shale tends to be more complicated. The destruction acoustic emission energy and fractal dimension show significant difference with quartz content. The research results of this article will play a certain role in promoting shale gas exploitation. Highlights The influence of quartz content on the mechanical properties of shale is numerically simulated. The energy evolution law of shale destruction in the presence of quartz is analyzed. The complexity of shale destruction caused by quartz content is analyzed. It is proven by a similarity test that shale changes with different mechanical properties of quartz content.