An effective medium model for the stress-dependence of anisotropic seismic velocities in fractured rock
Richard L. Gibson, Jr, Kai Gao, 2015. "An effective medium model for the stress-dependence of anisotropic seismic velocities in fractured rock", Fundamental Controls on Fluid Flow in Carbonates: Current Workflows to Emerging Technologies, S. M. Agar, S. Geiger
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Reliable analysis of time-lapse seismic data to detect movements of pore fluids requires consideration of variations in subsurface stress as well as fluid saturations. Achieving this goal requires reliable rock physics models that relate these stress changes to seismic velocity. Although there are many theories for the effective elastic properties of fractured media, only a small number directly include stress-dependence. Therefore, we have developed a new model that provides expressions that are comparatively easy to work with and requires estimation of only a small number of parameters. In this paper, we apply this model for the first time to the inversion of published laboratory measurements of pressure-dependent anisotropic seismic velocities. Specifically, we utilize measured velocities in two orthogonal directions to estimate the model parameters for a transversely isotropic medium. The model is then used to predict directional velocity variation in other directions at ambient pressure, and the errors in all cases are small. Synthetic shear wave seismograms computed for a hypothetical carbonate reservoir model show the changes in shear wave splitting and travel times that are predicted when seismic properties are computed using the theoretical model and help to illustrate the potential applications of the theoretical model to reservoir characterization.
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Fundamental Controls on Fluid Flow in Carbonates: Current Workflows to Emerging Technologies
This volume highlights key challenges for fluid-flow prediction in carbonate reservoirs, the approaches currently employed to address these challenges and developments in fundamental science and technology. The papers span methods and case studies that highlight workflows and emerging technologies in the fields of geology, geophysics, petrophysics, reservoir modelling and computer science. Topics include: detailed pore-scale studies that explore fundamental processes and applications of imaging and flow modelling at the pore scale; case studies of diagenetic processes with complementary perspectives from reactive transport modelling; novel methods for rock typing; petrophysical studies that investigate the impact of diagenesis and fault-rock properties on acoustic signatures; mechanical modelling and seismic imaging of faults in carbonate rocks; modelling geological influences on seismic anisotropy; novel approaches to geological modelling; methods to represent key geological details in reservoir simulations and advances in computer visualization, analytics and interactions for geoscience and engineering.