Phased array compaction cell for measurement of the transversely isotropic elastic properties of compacting sediments

Abstract

Sediments undergoing compaction exhibit transversely isotropic (TI) elastic properties that are described by five elastic constants. Continuous determination of all five constants in the laboratory during compaction is a difficult task. In this paper, we present a new experimental apparatus, the phased array compaction cell, for measuring the TI elastic properties of clay-rich sediments under uniaxial strain consolidation conditions. This apparatus uses matched sets of P-and S-wave ultrasonic transducers located along the sides of the sample and an ultrasonic P-wave phased array source together with a miniature P-wave receiver on the top and bottom ends of the sample. The phased array provides plane P-waves that are used to measure phase velocities over a range of angles. From these measurements, the five TI elastic constants can be recovered as the sediment is compacted, without the need for sample unloading, re-coring, or reorienting. Descriptions of the apparatus, data processing and an application demonstrating recovery of the evolving TI properties of a compacting marine sediment sample are provided in this paper.

Joint microseismic location and anisotropic tomography using differential arrival times and differential backazimuths

“…When the event locations and origin times are known, anisotropic tomography can be greatly simplified. In ideal cases such as experiments, if compressional and shear waves that propagate horizontally and vertically in a homogeneous space are recorded with waves propagating in other directions, then the parameters of a VTI medium can be determined separately and the tomography for a homogeneous space can be greatly simplified (Nihei et al 2011). In real cases, however, it is very uncommon to have such an ideal source-receiver geometry.…”