Rock physics and seismic methods for characterizing the heterogeneity of oil sands reservoirs in the western Canadian sedimentary basin

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2012
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Abstract
This thesis develops seismic prediction of the heavy oil reservoir heterogeneities in the Western Canadian Sedimentary Basin (WCSB). The thesis starts with studies on rock physics of the oil sands reservoirs in Athabasca to find the qualitative and quantitative relationships between the lithology and seismically derivable elastic parameters, which determines the feasibility of seismic applications. With an understanding of rock physics, the thesis makes seismic method developments to derive lithology sensitive elastic parameters for the qualitative and quantitative prediction of reservoir heterogeneity. The amplitude variation with offset (A VO) inversion is a well-established method to derive elastic parameters from the seismic data. But the A VO inversion is ill-posed if it derives three elastic parameters. To overcome the ill-posedness, a Bayesian constraint is naturally chosen by the industry. The thesis shows that the Bayesian estimator contains two tenns - the data term and prior term. While the data term is the solution used in most industrial practices of the A VO inversion, the complete estimate makes more sense with the help of the prior term. The practical implementation of the Bayesian A VO inversion improves the effectiveness of reliably deriving lithology-sensitive density, demonstrated in two case studies in the Athabasca oil sands. The A VO inversion provides attributes for the statistical and qualitative interpretation. It is the requirement of the quantitative reservoir characterization to convert seismic data into log-like elastic properties. An inversion scheme is designed and tested by a realistic oil sands point bar model. Three band-limited parameters from the AVO inversion are jointly inverted into absolute values by incorporating many constraints including the lateral local geology and rock physics. Seismic geometrical attributes are used to build reliable models for inversion and reservoir geometry mapping. For reliable reservoir characterizations, the seismic amplitudes should be recovered and preserved properly in data processing. The data fidelity for the extraction of elastic parameters is improved by the post-processing conditioning. Data examples show the amplitude recovery and A VO friendly processing. Developments are made on the offset­dependent tuning and NMO stretching correction and the reduction of impact on A VO by the irregularity of 3D surveys.
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Bibliography: p. 339-356
Many pages are in colour.
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Xu, Y. (2012). Rock physics and seismic methods for characterizing the heterogeneity of oil sands reservoirs in the western Canadian sedimentary basin (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/4554
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