Sonic has a dating problem
This equation represents the response of any single log curve to shale volume, porosity, water saturation, hydrocarbon type, and lithology.The best and easiest modern method for log reconstruction uses the Log Response Equation.The parameters required will vary depending on whether the reconstruction is for a water-filled case, an invaded-zone case, or an undisturbed reservoir, but the mathematical model is identical for all three cases.In intervals where there is no bad hole or light hydrocarbon, the reconstructed logs should match the original log curves.The magnitude of the error cannot be estimated without reconstructing the logs from an accurate petrophysical analysis.The light hydrocarbon effect problem alone would lead to erroneous elastic properties and erroneous Poisson' Ratio, Young's Modulus, and closure stress predictions.
The reconstructed logs are often called synthetic logs, to distinguish them from the original measured data set.
For example, in a conventional quantitative petrophysical analysis, we go to great lengths to avoid using bad data to obtain our results.
Gas effect in the invaded zone is handled by well established mathematical techniques or by calibration of results to core analysis data if the logs are inadequate for the purpose.
If light hydrocarbon effect exists in the invaded zone, this must be removed and then replaced by a set of log values representing the un-invaded reservoir condition.
This is the opposite of the stimulation design problem.
Track 2 has density correction (dotted curve), neutron (dashed), original density (red), synthetic density (black).