Print Email Facebook Twitter Estimation of changes in saturation and pressure from 4D seismic AVO and time-shift analysis Title Estimation of changes in saturation and pressure from 4D seismic AVO and time-shift analysis Author Trani, M. Arts, R. Leeuwenburgh, O. Brouwer, J. Faculty Civil Engineering and Geosciences Department Geoscience & Engineering Date 2011-03-14 Abstract A reliable estimate of reservoir pressure and fluid saturation changes from time-lapse seismic data is difficult to obtain. Existing methods generally suffer from leakage between the estimated parameters. We propose a new method using different combinations of time-lapse seismic attributes based on four equations: two expressing changes in prestack AVO attributes (zero-offset and gradient reflectivities), and two expressing poststack time-shifts of compressional and shear waves as functions of production-induced changes in fluid properties. The effect of using different approximations of these equations was tested on a realistic, synthetic reservoir, where seismic data have been simulated during the 30-year lifetime of a water-flooded oil reservoir. Results found the importance of the porosity in the inversion with a clear attenuation of the porosity imprint on the final estimates in case the porosity field or the vertically averaged porosity field is known a priori. The use of a first-order approximation of the gradient reflectivity equation leads to severely biased estimates of changes in saturation and leakage between the two different parameters. Both the bias and the leakage can be reduced, if not eliminated, by including higher-order terms in the description of the gradient, or by replacing the gradient equation with P- and/or S-wave time-shift data. The final estimates are relatively robust to random noise, as they present fairly high accuracy in the presence of white noise with a standard deviation of 15%. The introduction of systematic noise decreases the inversion accuracy more severely. Subject geophysical techniqueshydrocarbon reservoirsseismic wavesseismologywhite noise To reference this document use: http://resolver.tudelft.nl/uuid:85366722-1d95-4c9e-9ff5-de071270e49f DOI https://doi.org/10.1190/1.3549756 Publisher Society of Exploration Geophysicists ISSN 0016-8033 Source Geophysics, 76 (2), 2011 Part of collection Institutional Repository Document type journal article Rights (c) 2011 Society of Exploration Geophysicists Files PDF Trani_2011.pdf 19.47 MB Close viewer /islandora/object/uuid:85366722-1d95-4c9e-9ff5-de071270e49f/datastream/OBJ/view