Date of Award

2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Ehsan Ghazanfari

Abstract

Coupled Thermal-Hydrological-Mechanical-Chemical (THMC) processes that exist in the development of different geo-resources (e.g. deep geothermal and shale gas) affect the fracture response (i.e. aperture and permeability), which in turn influences the reservoir production. The main goal of this study was to experimentally evaluate the impact of THMC processes on the response of rock specimens relevant for deep geothermal and shale gas formations. The effects of THMC processes were investigated on: (i) success of the hydraulic fracturing/hydro-shearing mechanism during stimulation stage, and (ii) closure of the created network of fractures during production stage.

The elastic, cyclic, creep, and failure characteristics of different intact reservoir rocks in both short- and long-term were investigated to evaluate their response in stimulation stage. In addition, a series of flow tests on fractured reservoir cores were conducted to evaluate how THMC processes affect fracture response subjected to different stress levels, temperatures, composition of injected fluid, and injection rate. Moreover, the sensitivity of ultrasonic signatures (i.e. velocity, amplitude, attenuation, and time-frequency content) to (i) microstructural changes in the intact rocks, and (ii) flow-induced alterations of aperture/permeability in the fractured rocks were investigated. Analysis of hydraulic data, chemical composition of the effluent, ultrasonic signatures, and X-Ray micro-CT and SEM images, provided invaluable information that facilitated interpretation of the effects of coupled THMC processes on fracture response.

Language

en

Number of Pages

340 p.

Available for download on Monday, January 11, 2021

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