1887
Volume 16, Issue 9
  • ISSN: 0263-5046
  • E-ISSN: 1365-2397

Abstract

Three case studies demonstrate the benefits of using a layered impedance cube, instead of the conventional seismic volume, for performing 3D interpretation and reservoir characterization. To compute this cube, a 3D inversion program using a global optimization approach was implemented. From a sparsely parameterized initial model, this program updates both time and impedance values. The result is an automatic tracking of all strata in the seismic cube allowing the layer-bylayer display of consistent impedance values. Another advantage of the program is a strong enhancement of the vertical resolution of the seismic down to several metres, a scale which is closer to the reservoir layering. Moving from seismic amplitude to acoustic impedance Stratigraphic interpretation of 3D seismic data is usually performed on a migrated volume with limited resolution, which is due to the length of the seismic wavelet. When picking reflectors, geophysicists interpret interface geometry. The corresponding amplitude variations depend on impedance contrasts and thin layer interferences, and they are not suitable for interpolating reservoir properties on a layer-by-layer basis (Fig. 1). After appropriate preserved amplitude processing and zerophasing, the seismic volume should depict the true reflectivity of the subsurface, and it can be used to compute an impedance cube by means of poststack stratigraphic inversion. Due to the limited bandpass of the seismic, it is necessary to constrain this inversion by introducing the low-frequency variations. This a priori information allows impedance traces to be computed which tie with the absolute acoustic logs at the well locations. Different methodologies have been proposed by the industry to perform such stratigraphic inversion (Fig. 2). We present here a program, which uses a 3D multichannel algorithm, based on a global optimization technique, and which works iteratively to derive a layered impedance cube from a sparsely parameterized initial model (Gluck et al. 1996). This layering conforms to the stratification, and its vertical resolution is strongly improved with respect to the length of the seismic wavelet.

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/content/journals/10.1046/j.1365-2397.1998.00694.x
1998-09-01
2024-03-29
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  • Article Type: Research Article
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