ALLEN, JAMES L. and CAROLYN P. PEDDY, Houston Advanced Research Center, Houston, TX

ABSTRACT: Some Case Histories of AVO Failures in the Texas Gulf Coast

Five case histories illustrate some of the pitfalls in using amplitude-versus-offset (AVO) analysis to evaluate bright spots in the Texas Gulf Coast. The extension of an AVO anomaly downdip of a gas/water contact was probably caused by Fresnal zone effects. A clean thick wet sand and a lignite caused the bright spots and AVO anomalies in two examples. A shallow bright spot might have been rejected by a geophysicist who saw a decrease in AVO, but modeling of the well logs indicate that array effects can explain the observed AVO response. A fifth case history has no easy explanation.