Date of Award:

5-2011

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

James P. Evans

Committee

James P. Evans

Committee

Carol Dehler

Committee

Susanne Janecke

Abstract

The Mesaverde Group, within the Uinta Basin, Utah, is a source of current significant production and contains several trillion cubic feet of undiscovered natural gas resources. Due to the low permeability of the matrix rock, understanding the geometry and properties of natural fractures is critical to the development of effective ways of finding and producing natural gas. In order to evaluate and model the potential connectivity of hydraulically induced fractures to natural fractures at depth, we examine the nature of the natural fracture network using scanline sampling, imagery analyses, core analyses, and microstructural analyses. Regional fracture sets identified include: N-S (006° - 015°), NE (045° - 059°), NNW (326° - 342°) and a WNW (271° - 286°). Sedimentologic characteristics of seven sandstone lithofacies that control the fracture development and distribution include bed thickness, stratigraphic architecture/bedding geometry, the degree of cementation and cement type. Based on the sedimentologic controls on the character of natural fractures, lithofacies can be used to predict relative fracture densities within the Mesaverde Group based on environments of deposition. Sandstones deposited in braided river environments have lower fracture densities than sandstones deposited in meandering stream environments. WNW channel sand bodies with higher fracture densities perpendicular to N-S paleo-shoreline trends control the WNW productive "fairways" within the northeast Uinta Basin. For best connectivity between induced hydraulic fractures and the natural fracture network, we suggest targeting the more discontinuous, well-cemented sandstone lithofacies within the Mesaverde Group.

Checksum

329b8a270d932ccf54694150ee8d9588

Comments

This work made publicly available electronically on April 10, 2012.

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