Remote Assessment of Permeability/Thermal Diffusivity of Consolidated Clay Sediments.

摘要

The search for a suitable repository in which high-level waste may be safely contained over long periods of time has directed attention towards the geotechnical state of the deep ocean floor. Two geotechnical parameters of special importance are the permeability and thermal diffusivity of any proposed storage medium. In an attempt to evaluate the usefulness of geophysical techniques in predicting these parameters, a laboratory uniaxial consolidation cell has been modified to allow simultaneous geophysical measurements (P-wave, S-wave, electrical resistivity, thermal conductivity) during a standard consolidation test (permeability values being derived from the consolidation results). Results for nine surface sediment samples and four from depth in the sediment column suggest that permeability may be estimated to within an order of magnitude using compressional wave velocity measurements in a theoretical model based on Biot's equations. Similar success may be achieved empirically using electrical formation factor measurements. Thermal diffusivity may be assessed through the porosity of a sample, this in turn may be predicted from electrical formation factor measurements. The overall accuracies of the predictions are difficult to assess due to the possible effects of any sampling disturbance and laboratory constraints. The predictive methods identified require testing in an in situ environment where all the necessary measurements may be made simultaneously. This may be conducted initially on land using material similar to that evident in the samples already used, and at a fraction of the cost of marine operations. (Atomindex citation 16:054999)