Astronomy and Astrophysics – Astronomy
Scientific paper
May 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000geoji.141..413r&link_type=abstract
Geophysical Journal International, Volume 141, Issue 2, pp. 413-424.
Astronomy and Astrophysics
Astronomy
12
Cracks, Fabric Analysis, Ktb Well, Seismic Anisotropy, Sonic Log
Scientific paper
We analyse the relation between rock fabric, expressed by the preferred orientation of rock-forming minerals and microcracks, and elastic anisotropy of crystalline rock from the KTB pilot well. Detailed analyses of mineralogical composition, textures and microcrack fabrics were performed. In addition, ultrasonic velocity measurements of spherical samples in several directions were carried out at various confining pressures, and inverted in terms of the complete set of 21 elastic constants. By comparing the elastic tensors of the rocks at the final confining pressure (at which most of the microcracks are closed) with those at a lower pressure level, it is possible to separate the anisotropy induced by microcracks from that caused by mineral alignment. In contrast to previous work, no a priori knowledge of the type of anisotropy (triclinic, monoclinic, orthotropic etc.), or of the spatial orientation of the symmetry elements (planes, axes) of the cracked rock or of the intact rock is assumed. Furthermore, no restrictive assumptions on the orientation distribution function and the shape of the cracks are needed. The results show that the elastic anisotropy characteristics, whether they are related to the microcracks or to the rock-forming minerals, are clearly correlated with the directly observed rock fabrics. We show that the symmetry directions of the mineral fabric and of microcrack fabric agree. A further result is that the microcrack-induced anisotropy dominates the other causes of anisotropy at confining pressures smaller than a few tens of megapascals, the situation being reversed at higher pressures. The laboratory data are quantitatively compared with sonic log data from the KTB well, showing the influence of pore fluids, effective pressure and crack density reduction on the anisotropy in situ.
Rabbel Wolfgang
Rasolofosaon N. J. P.
Siegesmund S.
Vollbrecht A.
No associations
LandOfFree
Characterization of crack distribution: fabric analysis versus ultrasonic inversion does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Characterization of crack distribution: fabric analysis versus ultrasonic inversion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Characterization of crack distribution: fabric analysis versus ultrasonic inversion will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1129319