Stress induced anisotropy of sediments estimated from ultrasound measurements and cross-dipole sonic logging and crystallographic analysis of shales texture
The analysis of rock anisotropy in terms of seismic velocities and within the context of rock physics (Biot-Gassmann theory of poroelasticity) provides important information for the evaluation of the stress state (tensors) of rocks, detection of the directions of sediment formation weaknesses, helps in the estimation of overall permeability and failure prediction. Understanding the influence of stress, pore pressure and texture of rocks on seismic velocities is important for 4-D reflection seismic interpretation, AVO analysis and reservoir modeling. Laboratory measurements were carried out on spherical shale samples from the overburden under confining stress up to 400 MPa, by means of ultrasonic soundings in 132 independent directions. Such an approach enables the estimation of 3-D elastic anisotropy. Assuming VTI symmetry approximation, from the measured velocities the stiffness tensor was inverted. Since the sandstones were partly unconsolidated, it was not possible to take ultrasonic measurements. To overcome this problem, we developed a method for stress induced azimuthal anisotropy estimation using only cross-dipole logging data. These results give the possibility for anisotropic correction in AVO analysis. The main cause of acoustic anisotropy originates from the texture of rock i.e. preferred orientation of clay minerals. The texture of rock matrix was investigated by using X-ray diffraction analysis (XRD).
Miroslav Brajanovski Boris Gurevich Miodrag Mitric Tomas Lokajicek Dariush Nadri
Exploration Geophysics,Curtin University of Technology,Perth,Australia Institute of Nuclear Sciences Vinca,Belgrade,Serbia Institute of Geology,Academy of Sciences,Prague,Czech Republic CSIRO-Petroleum,Australia
国际会议
The 10th Western Pacific Acoustics Conference(第十届西太平洋声学会议WESPAC X)
北京
英文
1-8
2009-09-21（万方平台首次上网日期，不代表论文的发表时间）