Improved Synthetic Seismic Ties after LogAnalysis - Case Study in North America

摘要

Main inputs for synthetic gather generation include: the wavelet, density, compressional-DT and shear-DTlogs. The synthetic trace generated for the well location is then correlated with real seismic data. At thisstage various problems arise that are usually attributed to defects in the seismic information: incorrectsurface corrections, errors in time-depth conversion, sparse data, and various processing artifacts. Often,the problems with seismic ties are reverted back to the log information itself. This paper shows that logdata can be a significant source of error when improperly managed. Most problems belong to: i) bad logsii) insufficient data usually supplemented by linear interpolations. In both cases, density and Pwaveirregularities, as well as the artificial contrast between the linear segment and the 'real' data, can give riseto fabricated seismic reflections. Conversely, sharp contrasts in real formation properties can be blurred inlogs due to adverse hole conditions. In both cases, log substitution of data objectively identified as badimproves the well-seismic similarities. Both editions and substitutions should be based in sound loginterpretations and rock physics, rather than statistical estimations per se. An example and practicalsolutions in a well from North America are shown.