AVO Analysis for Lithology Prediction in the Pennsylvanian Reservoir Rocks in the Anadarko Basin, Oklahoma

AVO has proven to be an effective hydrocarbon indicator technique for Miocene and Pliocene gas exploration, especially in the Gulf of Mexico. Careful processing and calibration of pre-stack seismic data with petrophysical properties along with detailed petrophysical modeling has made AVO an important tool for lowering drilling risks and increasing the drilling rate success. In spite of this value, little or no research has been published on the implementation of this technique for the well-consolidated Paleozoic rocks of the Anadarko Basin.

Many workers will state that “AVO doesn’t work for such rocks”. We show through forward modeling and λρ-μρ inversion that AVO effects do exist, and that AVO does “work” to discriminate lithology, with fluid prediction being much more difficult and dependent on the lithofacies encountered. We examine the AVO dependency on porosity and fluid saturation for the Skinner and Red Fork formations using both conventional ray trace (AVO gather generation) and more rigorous full wave equation models created from well logs and interpreted formation tops. These models (where all the input parameters such as V¬P, VS , density and thickness are known) allow us to generate gathers that can be used to quantify our ability to discriminate lithology and fluid saturation. The elastic models include all propagation effects including mode conversion, post-critical head wave effects, and variation of tuning with offset.

In addition to direct modeling of lithologic effects, fluid saturation and porosity can also be predicted statistically. Given 600 wells in this survey, we correlate amplitude-based (e.g. impedance inversion) and morphology-based (e.g. curvature, coherence, texture) attributes to fluid product measured in the well and production measured at the well head.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California