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The cost and complexity of deep-water subsalt development wells is so great that a very limited spatial sampling of the target reservoir is achievable with well data. Thus, the quantitative use of seismic data becomes of paramount importance. Poststack seismic amplitude inversion, and poststack seismic attribute analysis and modeling are frequently employed to perform quantitative prediction of reservoir properties from surface seismic data. Several authors have shown that both absolute and relative acoustic impedance (AAI and RAI, respectively) derived from poststack seismic amplitude inversion can be useful for quantitative estimates of summary reservoir properties such as average porosity, net-to-gross, and others. This includes suprasalt and minibasin clastic reservoirs typically encountered in the Middle and Lower Tertiary plays in the deep-water Gulf of Mexico (several of which are also encountered subsalt), where depth to target can exceed 9000 m and highest frequencies at target are often rather low (20–25 Hz) (Bogan et al., 2003, Vernik et al., 2002).

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The Middle Devonian Marcellus shale that extends from Ohio and West Virginia, northeast into Maryland, Pennsylvania and New York, is believed to hold in excess of a thousand trillion ft 3 of natural gas. High-quality surface seismic data and top-of-the-line processing are essential to characterize these reservoirs and the overburden formations for safe and cost-effective drilling. A workflow comprising data acquisition and processing to prestack seismic inversion and lithofacies classification for characterizing the shale reservoirs is presented. The key elements in this workflow are dense point-receiver data acquisition and processing in the point-receiver domain. A small data set acquired with a proprietary point-receiver system was available to demonstrate the benefits of this methodology. The data were in an area in New York, where the Marcellus formation is known to exist. In this paper, we present the acquisition, processing and prestack inversion workflow leading to lithofacies classification and reservoir characterization. Prestack inversion provides acoustic and shear impedances, and density that enabled us to calculate the Poisson's ratio and the Young's modulus-the two important elastic attributes for shale-gas reservoir characterization. Based on these results, we find that the Marcellus formation in the study area is elastically highly heterogeneous, as is experienced by drilling and production engineers. We, thus, demonstrate that high-resolution acquisition and processing provides relevant elastic attributes for reservoir characterization to high-grade shale-gas reservoirs in the Marcellus formation of the Appalachian basin.