Title :
Constraints on the Permeability Structure of Alluvial Aquifers From the Poro-Elastic Inversion of Multifrequency P-Wave Sonic Velocity Logs
Author :
Baron, Ludovic ; Holliger, Klaus
Author_Institution :
Inst. of Geophys., Univ. of Lausanne, Lausanne, Switzerland
fDate :
6/1/2011 12:00:00 AM
Abstract :
We have explored the possibility of obtaining first-order permeability estimates for saturated alluvial sediments based on the poro-elastic interpretation of the P-wave velocity dispersion inferred from sonic logs. Modern sonic logging tools designed for environmental and engineering applications allow one for P-wave velocity measurements at multiple emitter frequencies over a bandwidth covering 5 to 10 octaves. Methodological considerations indicate that, for saturated unconsolidated sediments in the silt to sand range and typical emitter frequencies ranging from approximately 1 to 30 kHz, the observable velocity dispersion should be sufficiently pronounced to allow one for reliable first-order estimations of the permeability structure. The corresponding predictions have been tested on and verified for a borehole penetrating a typical surficial alluvial aquifer. In addition to multifrequency sonic logs, a comprehensive suite of nuclear and electrical logs, an S-wave log, a litholog, and a limited number laboratory measurements of the permeability from retrieved core material were also available. This complementary information was found to be essential for parameterizing the poro-elastic inversion procedure and for assessing the uncertainty and internal consistency of corresponding permeability estimates. Our results indicate that the thus obtained permeability estimates are largely consistent with those expected based on the corresponding granulometric characteristics, as well as with the available evidence form laboratory measurements. These findings are also consistent with evidence from ocean acoustics, which indicate that, over a frequency range of several orders-of-magnitude, the classical theory of poro-elasticity is generally capable of explaining the observed P-wave velocity dispersion in medium- to fine-grained seabed sediments.
Keywords :
elasticity; geophysical signal processing; groundwater; hydrological techniques; inverse problems; permeability; porosity; rocks; sediments; seismic waves; seismology; P-wave velocity dispersion; S-wave log; alluvial aquifer permeability structure constraints; borehole; core material permeability measurements; electrical logging; fine grained seabed sediments; first order permeability estimates; granulometric characteristics; litholog; medium grained seabed sediments; multifrequency P-wave sonic velocity logs; multifrequency sonic logging; nuclear logging; poroelastic inversion parameterisation; poroelastic sonic log inversion; sand; saturated alluvial sediments; saturated unconsolidated sediments; silt; Dispersion; Frequency measurement; Geophysical measurements; Permeability; Permeability measurement; Receivers; Sediments; Dispersion; geoacoustic inversion; permeability; seismic waves; well logging;
Journal_Title :
Geoscience and Remote Sensing, IEEE Transactions on
DOI :
10.1109/TGRS.2010.2095863