Velocity-permeability relations within hydraulic units

Relationships between seismic velocity and permeability have been difficult to establish. I show that by grouping and sorting rocks into hydraulic units, we can establish relationships between velocity and permeability. The hydraulic units are calculated from measured porosity and permeability values. Correlation between velocity and permeability is significant within each hydraulic unit (the correlation coefficient, R-2, lies in the range 0.65-0.87). This correlation is an extension of the match between porosity and permeability within a hydraulic unit. I show how the compaction and cementation history of a sediment can have effects on its physical properties such as porosity and permeability and on its seismic properties. The measured velocity data are further approximated with the Biot model. The velocity-permeability relation and modeling results are demonstrated for a large data set of laboratory measurements. The good match between calculated and measured data demonstrates that this relation can be used to predict permeability from velocity in well logs by zoning the data from training wells into hydraulic units. One possible application is shown where, by using site-specific data, the velocity-permeability relation is vastly improved with a correlation coefficient R-2 of 0.9.