Integration of image and dipole sonic logs for identification of natural fractures and stress-induced anisotropy in Asmari reservoir(A case study,SW Iran)OA

Borehole sonic dispersion analysis is a technique that provides valuable insights into the realm of borehole sonic interpretation.This research involves an analysis of shear-wave anisotropy and ultrasonic image logs to differentiate between types of fractures and their orientations.Evaluating fractures relies on core samples and image logs are limited.This highlights the need for a more affordable and efficient way to analyse fractures.A challenge in the wellbore is distinguishing natural fractures from those caused by drilling.Using oil-based mud often makes it hard to find signs indicating the direction of in-situ stress.A new method has been created to reliably identify natural fractures when image logs are insufficient for mapping fracture networks.The cross-dipole data reveals five main zones exhibiting shear-wave splitting.Higher anisotropy is observed at shallower depths,while the deeper interval shows low porosity accompanied by considerable inhomogeneity,highlighting potential areas of concern.The dominant directions of anisotropy are aligned with NW-SE,WNW-ESE,and N-S orientations.Slowness frequency analysis of rotated flexural waves identifies fracture types.Dispersion profiles show natural and induced fractures,with cross-over patterns indicating stress-induced anisotropy.Significant inhomogeneity is observed in the bottom interval,where the differences between maximum and minimum energy level are pronounced.Wider dispersion curves suggest breakouts are slowing high-frequency flexural waves,indicating mechanical damage.The maximum stress direction is determined by the fast-shear azimuth.In conclusion,this study demonstrates that by integrating acoustic shear dispersion,shear anisotropy,Stoneley analysis,and image log data,fractures within the borehole wall can be effectively investigated.