Using Synthetic Seismic Models of Channelized Deepwater Slope Deposits to Inform Stratigraphic Interpretation and Reservoir Modeling

Abstract

Reservoir scale interpretation from seismic-reflection profiles of deep-water channels is inherently challenging due the sub-seismic scale nature of key stratigraphic surfaces and facies transitions. Valuable insight can be gained from synthetic forward seismic modeling of outcrop models characterized by multi-scale (bed to channel complex set) stratigraphic architecture. Synthetic modeling studies are ideal for: 1) understanding uncertainties inherent to seismic interpretation, 2) assessing the information content of seismic reflectivity profiles at different resolutions, and 3) using seismic data in a more effective way to inform reservoir models. A bed-scale model of a single channel element was created based on Cretaceous slope channel fill deposits that crop out adjacent to Laguna Figueroa in the Magallanes Basin of southern Chile. This model was used to generate forward seismic models with two different sets of rock properties (deep Gulf of Mexico and shallow offshore West Africa). The results were analyzed to quantify the error in predicting channel width and thickness at different model resolutions. The goal was to assess the threshold at which prediction error increases and how the error scales with the frequency of the seismic image. Two channel elements were then stacked to elucidate the predictability of stacking patterns between two channel elements. The analysis was then expanded to a series of channel elements that collectively comprise a channel system up to 100 m thick. The results of this simple modeling effort can be applied directly to understand interpretation error in subsurface seismic reflection profiles, and to quantify the volumetric and connectivity uncertainty to mitigate production risk. Results show that stratigraphic interpretation error scales linearly with the seismic resolution. Furthermore, the degree of ambiguity in interpreting the number of channels is a function of the seismic resolution as well as stacking patterns of the channels. Vertically stacked channels and laterally offset channels are difficult to differentiate, while the combination of aggradation and offset offers more clues to channel numbers. Finally, sub-seismic scale internal channel architecture can only be interpreted from unrealistically high frequency data.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016