报告题目：The Interplay Between Stress and Material Heterogeneity during Hydraulic Fracturing

报  告 人：Giovanni Grasselli  教授

邀  请 人： 严  鹏    教授

时      间： 2024年10月25日（星期五）上午9:30

地      点： 八教8213会议室

报告人简介：

Grasselli教授现任职于多伦多大学土木与采矿工程学院，主要从事混合有限-离散元法（FDEM）数值模拟技术、实验可视化技术以及应用于隧道施工和水力压裂研究的地质力学机理等领域的研究。Grasselli教授在意大利帕尔马大学取得土木工程本科学位，在瑞士洛桑联邦理工学院取得岩石力学博士学位；在2006年加入多伦多大学任教之前，曾在伦敦帝国理工学院（英国）和桑迪亚国家实验室（美国）担任研究员，并曾担任劳伦森大学Mirarco研究所的副主任（加拿大）；曾荣获2004年ISRM Rocha奖章、2019年CGS的John A. Franklin岩石力学奖以及2024年PEO工程奖章。

报告简介：

A series of true-triaxial hydraulic fracturing tests were conducted on shale specimens from the Montney formation, both from outcrop and at-depth samples. These tests were designed to simulate in-situ conditions, replicating open-hole fluid injection at depth. The goal was to evaluate the effects of flaws, anisotropy, intermediate stress, and fluid viscosity on fracture behavior.

Interestingly, the experiments revealed that fractures formed against σ2 (the intermediate principal stress) rather than σ3 (the minimum principal stress), challenging the conventional belief that fractures always propagate in the direction of the minimum stress. This suggests that tensile strength anisotropy plays a role as significant as in-situ stresses in determining fracture initiation and propagation. The outcome of this research is a new conceptual model that considers both the magnitude of in-situ stresses and the anisotropy in the rock's tensile strength, identifying the path of least mechanical resistance. Another key finding highlights the impact of fluid viscosity on the complexity of the resulting fracture network.

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