Seismic variation with offset: A case study of an Eocene gas field, mid-dip Yegua formation in Jackson County, Texas

This thesis presents a case history from a Texas Gulf Coast onshore discovery where analysis of reflection seismic amplitude variation with offset (AVO) was used to predict the presence of hydrocarbons in an Eocene age “mid-dip” Yegua formation sand. Both geologic and geophysical basis for the analysis is provided. Methodology for developing the discovery, including drilling results from a development well, are presented. The methods describe various cases of fluid modeling. The fluid models are used to generate synthetic seismic traces intended to simulate the observed surface seismic response across the proposed development drilling location. The mid-dip Yegua sand studied is characterized as a type III anomaly, indicated by a near offset negative reflection becoming increasingly negative as shot to receiver offset increases. The successful case of forward modeling and subsequent development is presented as an example of AVO analysis improving the success rate for mid-dip Yegua trend wells.