Author ORCID Identifier

https://orcid.org/0009-0000-2956-6495

Semester

Spring

Date of Graduation

2023

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Timothy Carr

Committee Member

Vikas Agrawal

Committee Member

Dustin Crandall

Committee Member

Shikha Sharma

Committee Member

Amy Weislogel

Abstract

Optimizing recovery from unconventional shale reservoirs has generated considerable research into optimal recovery methods through hydraulic fracturing design and shale reservoir characterization in the development of long-term hydrocarbon producers. Permeability at multiple scales from nanometer-scale pore sizes and nano-darcy permeability to completion-induced fractures defining a 100’s of meter stimulated reservoir volume plays a significant role in hydrocarbon flow during production in shale reservoirs. Preexisting cemented fractures in unconventional shale reservoirs are abundant and preferentially reactivate during induced hydraulic fracturing treatment to create necessary large-scale permeability. While previous investigations have significantly improved our knowledge of shale reservoirs, it has also highlighted the need for increased understanding of the geologic evolution and effect on hydraulic stimulation of pre-existing cemented fractures.

This three-part dissertation examines natural fractures from four middle Devonian Marcellus Shale wells across the Appalachian basin through integration of visual core observation, thin section petrography, spectral gamma ray logs, borehole image logs, petrophysical logs, elemental data, and X-ray computed tomography cores. The research goals are: (1) to establish clues to assess natural fracture development in source rocks from kerogen maturation, relative timing, and hydrocarbon migration; (2) to investigate the relationship of natural fractures in wells of varying thermal maturity levels, and preferential fracture distribution in various clay types and redox environments; and (3) to characterize mineralized natural fractures in 3D using a medical CT-scan core to quantify volume and assess connectivity. This research indicates that overpressure from kerogen expulsion of hydrocarbon creates numerous cemented fractures filled with calcite and bitumen that achieve orientations related to the geologic burial stresses during their evolution, predominant in clay-rich units of certain redox conditions, cluster at geomechanical boundaries, and have inconsistent 3D volume changes within the core.

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