Sonic Log

nullWell Log Interpretation Sonic LogWell Log Interpretation Sonic LogEarth & Environmental Science University of Texas at ArlingtonSonic LogSonic LogThe sonic log measures the time, Dt in microseconds, it takes a compressional wave to travel through 1’ of rock. The units are msec/ft, the inverse of velocity. The sonic velocity can be related to seismic velocity.Sonic LogSonic LogThe sonic transit time depends on the lithology, porosity and fluids in the pore spaces. It also assumes a homogeneous distribution of porosity. Vuggy and fracture porosity give spurious results.Sonic LogSonic LogTo compute porosity from a sonic log, the following information is needed: Dtma: transit time through the matrix alone Dtfl: transit time through the fluid alone Dtlog: the measured transit time from the log.Sonic LogSonic LogThere are two equations commonly used to compute sonic velocity: Wyllie time averaged:Raymer-Hunt-Gardner (RHG)Sonic LogSonic LogCp, a compaction factor, = 1 for consolidated sediments. For unconsolidated sediments:Sonic LogSonic LogIf hydrocarbons are present, fs must be reduced by a factor of 0.7 (gas) or 0.9 (oil)Sonic Log AssignmentSonic Log AssignmentUsing the sonic log on the left, make a spreadsheet that computes fs for lms, dol and ss at depths of 9300’ and 9369’ using both the Wyllie and RHG equations. Label each parameter.