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Abstract

Detection of fractures using geophysical methods has proven elusive. A significant amount of theory has been developed, however, convincing applications of the theory to observed data have been lacking. In this paper we show a clear example of seismic amplitude changes due to controlled fracturing from injection at the Alpine field in Alaska. We use the ability of time-lapse seismic data to remove the background medium so that seismic amplitude changes due to the creation of open fluid (gas or liquid) filled fracture systems are clearly exposed around injectors. Additionally we utilized rock-model-based seismic forward modelling to test against three different models of fractured media. We conclude that the Kuster-Toksoz randomly distributed fracture model is the most appropriate for Alpine. Using this model we are able to calibrate the fracture parameters (fracture pressure, fracture aspect ratio, and fracture porosity) to match observed data. Our results show that fracturing can introduce 4D velocity changes significantly larger than what would be expected from using velocity-pressure trends from core measurements alone. Finally, using time-lapse AVO modelling we show that at Alpine it may be possible to discriminate between gas- and oil/water-filled fractures.

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/content/papers/10.3997/2214-4609.20130177
2013-06-10
2024-03-29
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http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609.20130177
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