Technical and economic value of seismic inversion in field development

Modern three-dimensional seismic methods provide high-resolution imaging of the subsurface. Although mapping of reservoir structure can be done directly, reflection amplitudes indirectly contain information about reservoir properties in the form of acoustic impedance. Transformation of seismic amplitudes into acoustic impedance, commonly called seismic inversion, allows estimation of reservoir properties away from well control. First, the authors explore the benefits of quantitatively using impedance to predict the spatial variations of reservoir parameters such as lithology, porosity, and fluid saturation. Relationships between petrophysical properties from well control and seismic impedance can provide information that would not be available from seismic amplitudes or well data alone. Second, they examine the trade-off between the cost and technological payoff of seismic inversion. The inversion cost is a small fraction of the overall seismic acquisition/processing cost. However, it can provide a spatially continuous description of the reservoir. The trade-off between economics and technology is controlled by three factors: (1) the objectives of the study, (2) the petrophysical relationships of the reservoir, and (3) the data quality. The issue of technological benefit vs. economics is illustrated through several field examples with varying data conditions, such as reservoir size, different petrophysical relationships, and different levels of well control,more » to identify the critical factors for predicting reservoir properties away from well control. These examples show that seismic inversion can be cost effective through improved reservoir description resulting in optimal siting of wells and reduced development costs.« less