Facies Driven Extended Elastic Inversion - Application to the Niobrara
Y. Kiche, L. OUHIB, D. Balogh and A. Ouenes
Event name: 78th EAGE Conference and Exhibition 2016
Session: AVO Inversion and Rock Physics
Publication date: 31 May 2016
Info: Extended abstract, PDF ( 1.82Mb )
Price: € 20
As industry experience with the technique grew, the elastic inversion, or angle stack AVA inversion is highly used to recover the fundamental rock properties of an earth model (VP, VS, and density) and recently, the ability of the elastic inversion to predict the variation of the local stress (Goodway et al., 2010) and to calculate geomechanical properties (Gray et al, 2012) has caused elastic inversion to become a critical component in modern unconventional reservoir characterization (Ouenes, 2012). To improve the accuracy of the elastic result, a 3-term formula of normalized elastic impedance is used instead the 2-term Aki-Richards approximation to the Zoeppritz equations but the major challenge to elastic inversion lies in its’ sensitivity to noise. In the absence of noise, the elastic inversion will correctly fit the elastic impedances to the real rock properties in the subsurface. However, the addition of a very small amount of noise to the data can dramatically change the resultant rock properties. This means that an unconstrained inversion, (land surveys where the S/N ratio is lower), will generally produce inconsistent and erroneous values. These issues point to the need to constrain the inversion consistent results by using a facies model as geologic driver.