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Mineralogical and Textural Controls on Shear Strength, Slip Stability and Permeability of Faults
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | Mineralogical and Textural Controls on Shear Strength, Slip Stability and Permeability of Faults. |
| 개인저자 | Wang, Chaoyi. |
| 단체저자명 | The Pennsylvania State University. Energy and Mineral Engineering. |
| 발행사항 | [S.l.]: The Pennsylvania State University., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 177 p. |
| 기본자료 저록 | Dissertations Abstracts International 80-12B. Dissertation Abstract International |
| ISBN | 9781392319000 |
| 학위논문주기 | Thesis (Ph.D.)--The Pennsylvania State University, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 80-12, Section: B.
Publisher info.: Dissertation/Thesis. Advisor: Elsworth, Derek. |
| 요약 | Induced seismicity resulting from fluid injection into the subsurface related to water and CO2 disposal, hydraulic fracturing and the stimulation of geothermal reservoirs present an important societal concern. These human activities involve the injection of large volumes of pressurized fluid into the subsurface, potentially at high rates, raising local pore pressures and disturbing the pristine local stress regime by lowering effective normal stress on pre-existing faults and fractures. The reduction of effective normal stress may trigger fault/fracture reactivation and in some cases result in hazardous seismic ruptures. Effective management and engineering of anthropogenic seismic events requires substantial understanding in the mechanisms, especially for the controlling factors on coupled rheological and transport response, including fault shear strength, slip stability, and permeability evolution during such events. In this study, we explore the coupled rheological and transport response of faults and fractures during reactivation as controlled by two fundamental controlling properties, viz., mineralogy and textural features. We approach this problem through shear experiments on analog faults and fractures via laboratory and numerical experiments. Specifically, we investigate: (1) the influence of frictionally weak minerals (talc) in mixtures of mineral analogs featuring contrasting frictional properties, (2) the influence of iron oxide grain coatings on quartz aggregates, and (3) the influence of fracture roughness in mated fractures on the ensemble shear strength, slip stability, and permeability evolution during reactivation events. We address the following questions in this study: (1) how much and what distribution of frictionally weak minerals is required to induce significant weakening in faults consisting of a matrix of frictionally strong minerals, (2) how does a pre-imposed weak mineral layer influence the rheological and transport behavior of faults, (3) what is the influence of a trace amount of grain coating materials introduce on the coupled behavior of faults, and finally (4) how do asperity height and wave length control the ensemble behavior of faults. These questions are explicitly answered in the following.Chapter 1 explores the impact of phyllosilicate (weak but velocity-strengthening) in a majority tectosilicate (strong but velocity-weakening) matrix in bulk shear strength and slip stability of faults. Numerical simple-shear experiments using a Distinct Element Model (DEM) are conducted on both uniform mixtures of quartz and talc analogs and on textured mixtures consisting of a talc layer embedded in a quartz matrix. The mechanical response of particles is represented by a linear-elastic contact model with a slip weakening constitutive relation representing the essence of rate-state friction. The weight percentage of the talc in the uniform mixtures and the relative thickness of the talc layer in the textured mixtures are varied to investigate the transitional behavior of shear strength and slip stability. Specifically, for uniform mixtures, ~50% reduction on bulk shear strength is observed with 25% talc present, and a dominant influence of talc occurs at 50% |
| 요약 | Subsurface fluid injections can disturb the effective stress regime by elevating pore pressure and potentially reactivate faults and fractures. Laboratory studies indicate that fracture rheology and permeability s in such reactivation events are linked to the roughness of the fracture surfaces. We construct discrete element method (DEM) models to explore the influence of fracture surface roughness on the shear strength, slip stability, and permeability evolution during such slip events. For each simulation, a pair of analog rock coupons (3D bonded quartz-particle analogs) representing a mated fracture are sheared under a velocity-stepping scheme. The roughness of the fracture is defined in terms of asperity height and asperity wavelength. Results show that (1) samples with larger asperity heights (rougher), when sheared, exhibit a higher peak strength which quickly devolves to a residual strength after a threshold shear displacement |
| 일반주제명 | Geophysics. Geophysical engineering. Petroleum engineering. |
| 언어 | 영어 |
| 바로가기 | 
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