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Deterioration of a fractured carbonate caprock submitted to CO2-brine flow: Implications for seal integrity at a pilot CO2-injection site

Speaker: Brian Ellis, Graduate Student
Series: EEWR Brown Bag Seminars
Location: Engineering Quad E219
Date/Time: Friday, December 3, 2010, 12:00 p.m. - 1:00 p.m.

Abstract:

In this presentation Brian will discuss some of the recent results from his experimental work completed at the Morgantown, WV, Department of Energy National Energy Technology Laboratory. Over this past summer he conducted a flow through experiment designed to investigate fracture evolution of a fractured carbonate caprock during simulated leakage of CO2-acidified brine. A combination of X-ray computed tomography and scanning electron microscopy was used to observe fracture evolution and investigate the mineralogical changes that occurred along the fracture wall. After one week of brine flow, the cross-sectional fracture area increased by an average of 2.7 times that of the initial fracture. The fracture surface was not eroded uniformly, with the largest areas of aperture growth corresponding to direct contact between the acidified brine and calcite. This preferential dissolution of calcite led to a large increase in fracture surface roughness and in some instances, the development of a silicate mineral-rich microporouscoating along the fracture wall. Results from this study highlight the importance of formation mineralogy and suggest that the clay content of low permeability carbonate formations may be an important factor in controlling their long term integrity while in contact with acidified brine.