ABSTRACT

The quantification of lithology, fluids, and structure are the definitive goals of seismic exploration. Exploitation of amplitude information only, although sufficient for many structural interpretations, fails in the ability to adequately define lithology. Conventional post-stack inversion technology, while quantifying rock property information in the form of acoustic impedance, velocity, or density, conveys little in the way of definitive mineral or fluid information. For example, a low velocity interval from an inversion may be interpreted as either a porous sand reservoir or a slow shale, with obviously different drilling results.

AVO technology exploits the loss or gain in reflected P-wave energy due to shear wave conversion at interfaces. Although AVO measurements from pre-stack seismic data contain fluid and lithology information, conventional AVO gradient products fail to provide quantification of lithology or fluids.

We present a technology for extracting detailed lithology, porosity and hydrocarbon content sections from conventional seismic data through a unique combination of AVO and seismic inversion technologies. The method has been in use for several years and successfully decomposes sand, shale, and carbonate lithologies including gas/oil fluid content and effective reservoir porosity. Current research is successfully extending the technique to quantify salts and coals.