ABSTRACT: The Gulf of Mexico as global analogue: a Comparison of AVO and Energy Absorption with the South Caspian Basin

WARE, PAUL, MAI YANG, KEITH WROLSTAD, KE-SHAN ZOU, SYED ZAMAN, and RANDY COOPER

Frequently cited as a global analogue for young Tertiary basins, results derived from the GOM are often (mis-)applied in relatively unexplored areas, world-wide. However, unsophisticated application of conventional AVO reconnaissance techniques will not work, for example, in the similar geological conditions prevalent in the South Caspian Basin.

Results of full waveform modeling of several SCB wells reveal the inadequacies of traditional P-wave approximations (e.g. Impedance_sst is greater than Impedance_shale shallow; but Impedance_shale is greater than Impedance_sst
deeper.

Also, the Class II-III AVO response shows a local relationship with porosity that is the inverse of the GOM. Three-point log analysis techniques point to a mineralogical influence as a contributing factor. Geophysical modeling shows noise induced by converted waves which can be minimized by radon transform filtering. Perturbation models are presented that show a change in AVO character at the crossover point(s). As these are not consistent basin-wide, conventional AVO modeling without nearby well control will lead to false results. Preliminary results show some success in using energy absorption to detect hydrocarbons. Examples are shown from the GOM and SCB which show conflicting AVO responses but consistent energy absorption.

Conclusions derived from the SCB, and elsewhere, allow us to re-consider assumptions made about the application of the techniques closer to home and permit a greater understanding of the geological processes behind the geophysics.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana