Optimizing Hydraulic Fracturing: The Importance of Reservoir Rock Characterization under True-Triaxial Loading

报告题目：Optimizing Hydraulic Fracturing: The Importance of Reservoir Rock Characterization under True-Triaxial Loading

报告人：Giovanni Grasselli

报告时间：2024年10月30日（周三）9:00-11:00

报告地点：全国重点实验室A403学术报告厅

报告人单位：加拿大多伦多大学

报告人简介：

Giovanni Grasselli is a Professor and the NSERC/Energi Simulation Industrial Research Chair in Fundamental Petroleum Rock Physics and Rock Mechanics at the University of Toronto. Dr. Grasselli holds an undergraduate degree in Civil Engineering (1995) from the University of Parma, Italy, and a PhD in Rock Mechanics (2001) from the Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland. Before joining the University of Toronto as a faculty in 2006, he has been research fellow at the Imperial College London (UK), Sandia National Laboratories (USA) and has served as associate director at Laurentian University’s Mirarco (Canada). He received the prestigious 2004 ISRM Rocha Medal, the 2019 CGS’ John A. Franklin Award in Rock Mechanics, and supervised two Rocha Medal winners (2015 and 2017). His research focuses on hybrid finite-discrete element (FDEM) numerical technology, experimental visualization techniques, and geomechanics principles applied to the study of tunnelling and hydraulic fracturing.

Giovanni Grasselli, 多伦多大学教授。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。

报告内容：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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