Major obstacles to deploying carbon capture and storage (CCS) are demonstration of safe geological CO2 storage and determining the risk of leakage. Neil M. Burnside and colleagues present a unique field site where three types of leakage, diffuse and fault focused natural flow and abandoned wells, can be compared in a single geological setting. Coupling U-Th dating and volume measurement of travertine we have determined a 400,000 year CO2 leakage history for the site. The two faults that penetrate the natural CO2 accumulation produce two different types of natural leakage. Where low permeability layers are present, leakage is focused along faults; where these layers are absent a diffuse pattern dominates and leakage extends 500 m from the fault. Comparison of total CO2 emission shows that fault focused leakage is twice as severe as diffuse leakage. An actively leaking abandoned exploration well allows for comparison of man-made and natural leakage. Calculating total CO2 emissions from this well shows that, in this instance, man-made leakage is 13 times greater than natural fault focused leakage. This study demonstrates that style and volume of leakage is dependent on the underlying geology and that man-made leakage poses a far greater risk than natural leakage to the success of safe geological storage of CO2.
Morphodynamic diversity of the world's largest rivers
Andrew Nicholas, Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK. Posted online 20 Feb. 2013; http://dx.doi.org/10.1130/G34016.1.
Large alluvial rivers transport globally significant quantities of water, sediment and nutrients to the oceans, temporarily storing and cycling this mater
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Geological Society of America