Sensitivity of time-lapse changes in pressure and saturation to seismic AVO and time-shifts
conference paper
An inversion scheme that solves for reservoir pressure and fluid saturation changes from time-lapse pre-stack seismic attributes and post-stack seismic time-shifts is presented. It makes use of four equations expressing the changes in zero-offset and gradient reflectivities, compressional and shear waves time-shifts as functions of production induced changes in fluid properties. The method has been successfully tested on a realistic, synthetic reservoir, where seismic data have been modeled before and after 30 years production and water injection. Results show very accurate estimations if information about the vertically averaged reservoir porosity is available. The use of the gradient reflectivity equation causes biased estimations of real changes in saturation and strong leakage between the two different parameters. However, if the equation related to the S-wave time-shift can replace the gradient reflectivity equation, the inversion results may be very accurate. In cases where shear wave data might not be acquired, the approximation of the exact changes in this seismic attribute becomes more accurate if quadratic terms in relative changes of seismic properties are not neglected. The improved forward approximation in this attribute leads to inversion results characterized by weaker leakage and sharper discrimination between different fluid effects.
TNO Identifier
425120
ISBN
9781617386671
Source title
72nd European Association of Geoscientists and Engineers Conference and Exhibition 2010 - Incorporating SPE EUROPEC 2010, 14 June 2010 through 17 June 2010, Barcelona. Conference code: 81997
Pages
47-51
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