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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Civil Engineering

Year Degree Awarded

2018

Month Degree Awarded

September

First Advisor

Dr. Carlton L. Ho

Second Advisor

Dr. David A. Reckhow

Third Advisor

Dr. Guoping Zhang

Fourth Advisor

Dr. Baoshan Xing

Subject Categories

Geotechnical Engineering

Abstract

Mitigation and prevention of shale-formation damage caused by hydraulic-fracturing fluid/rock interactions play an important role in well-production stability and subsequent refracturing design. This study presents three experimental investigations on the interaction of water/shale, fluid/clay, and fluid/shale. A series of experiments were designed to investigate fluid/shale interactions: hydrophilic to hydrophobic alteration through chemical-vapor deposition, nanoindentation testing on shale sample, geotechnical laboratory experiments on contaminated clay, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscope (SEM) on shale sample. A clay-matrix-based data-screening criterion is proposed for nanoindentation. The continuous-stiffness-measurment (CSM) method is proved to have better definition and characterization of softening of shale based on the proposed criterion. This study furthered the numerical model of clay deformation by Hattab and Chang (2015) by considering different pore fluid concentration. The fracturing fluid contaminated clay produced changes of geotechnical properties. Based on the proposed criterion and designed experiments, fracturing fluid contaminated shale was observed to gain 4 to 6% of NaCl. However, all other minerals contents are found to decrease after the shale powder-fluid interaction. A characteristic depth was proposed to consider reduction of hardness and mineral content at the same time. Moreover, an empirical equation was proposed to describe fracture toughness of shale by using a selection of indentation depth, its corresponding hardness and Young’s modulus.

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