Date of Award:

12-2011

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geology

Advisor/Chair:

Dr. James P. Evans

Abstract

Sequestration of carbon dioxide (CO2) into subsurface porous sandstone is proposed as a method for reducing accumulation of anthropogenic emissions of CO2 into the atmosphere. Natural exposures of reservoir and top-seal pairs in central and southeastern Utah are identified as analogs to proposed CO2 injection targets. Reservoir and top-seal pairs in natural analog exposures are analyzed in tandem to evaluate evidence for paleo-migration of fluids and/or hydrocarbons from the reservoir through the top seal. The San Rafael Swell and Monument Uplift exhibit similar structure and exposures of Jurassic units yet differ in amount and type of host rock alteration due to variable amounts and types of fluids and/or hydrocarbons that migrated along faults and fractures.

Macroscopic scale analysis of each monocline included processing of satellite imagery, and creation of depth contour maps. At the mesoscopic scale, fracture spacing acquired from scanline station measurements identified increased fracture frequency in proximity to major fault zones. At the microscopic scale, percentage of degradation and type of mineralization in pore space were used to verify increased fluid flow in proximity to major fault zones.

Faults with possible intersections with multiple antithetic faults at depth have an increased probability of allowing for upward migration of fluids and/or hydrocarbons along the fault plane and damage zone, effectively bypassing the top sealing formations. Fault leakage potential maps identified areas where seal bypass along major faults would likely occur during sequestration of CO2. The method was validated by identifying potential migration pathways for oil seeps on the Little Grand Wash fault in central Utah. The San Rafael Swell was geometrically modeled through restoration of eroded formation tops along the fold axis to quantify the interaction between an outward migrating CO2 plume and varying degrees of faulting and fracturing. Analysis of the migration of a CO2 plume front through time exhibits an increasing probability of the outward migrating plume intersecting a leaking feature, with the highest probability of the advancing plume intersecting a potentially leaking feature achieved when faults with 1+ km trace length and mean fracture spacing of 17 cm are taken into consideration. (177 pages)

Comments

Publication made available electronically January 24, 2012.

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