Stratigraphic Processing for AVO and AVZ Analysis
Roy Burnstad* and Timothy H. Keho
We present a stratigraphic processing flow which prepares wide-azimuth, long-offset, 3-D seismic data for amplitude-versus-offset (AVO) and amplitude-versus -azimuth (AVZ) analysis. Simultaneous analysis of the variation of amplitude with offset and azimuth is necessary for an integrated study of lithology, fluids and fractures. The processing flow extends the general concepts of AVO processing to include the azimuth domain. Our approach is target oriented. We use an interpreted seismic horizon to define the design window for pre-stack operators. We begin by applying all available time corrections from previous processing. This includes datum statics, residual statics, normal moveout corrections and structural time corrections. By using structural time corrections we are taking advantage of the gently dipping nature of the geology as typically found in the Eastern Province of Saudi Arabia. Next we apply 3-D linear noise removal simultaneously on all offsets and azimuths. We then run cascaded multi-channel, surface consistent, amplitude and frequency analysis. Each pass includes separate terms for source, receiver, offset and azimuth. We use azimuth- and offset-friendly algorithms. This means that unless the record is operated on as a whole, each process must accommodate offset and azimuth terms. At several stages during the processing flow we employ quantitative quality control checks by analyzing a variety of pre-stack attributes along key horizons. Finally, we define an important quality control guideline that states our AVZ decomposition must bear similarities to the anisotropy ellipse. We illustrate this approach using a wide-azimuth, long-offset, survey recently acquired over a Jurassic reservoir in Saudi Arabia.
AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain