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

報告人：Giovanni Grasselli

報告時間：2024年10月30日（周三）9:00-11:00

報告地點：全國重點實驗室A403學術報告廳

報告人單位：加拿大多倫多大學

報告人簡介：

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, 多倫多大學教授。主要從事混合有限-離散元法（FDEM）數值模擬技術、實驗可視化技術以及應用于隧道施工和水力壓裂研究的地質力學機理等領域的研究。Grasselli教授在意大利帕爾馬大學取得土木工程本科學位，在瑞士洛桑聯邦理工學院取得巖石力學博士學位；在2006年加入多倫多大學任教之前，曾在倫敦帝國理工學院（英國）和桑迪亞國家實驗室（美國）擔任研究員，并曾擔任勞倫森大學Mirarco研究所的副主任（加拿大）；曾榮獲2004年ISRM Rocha獎章、2019年CGS的John A. Franklin巖石力學獎以及2024年PEO工程獎章。

報告內容：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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