Seismic Attributes and Reservoir Modeling for Athabasca Oil Sands in Canada

This paper describes effective use of seismic attributes in the geostatistical reservoir modeling of oil sands. The goal of the work was to provide models for the reservoir simulation to forecast bitumen production from oil sands by Steam Assisted Gravity Drainage method (SAGD). Simulation models were required to reconstruct geological heterogeneity with sub-seismic resolution which can affect the steam chamber growth. Stochastic modeling approach was employed to generate realizations with the required resolution for uncertainty assessment. Depositional environment of the target formation was considered as fluvial-to-estuarine, and reservoir properties were varied drastically in both vertical and horizontal directions. Seismic data were used to capture the vertical and areal trend components in the reservoir property variations to take them into account for the application of the geostatistical tools. Correlation between seismic attributes and reservoir properties was examined to find that density and velocity provide useful information for both facies discrimination and mudstone volume estimation. The procedure of our reservoir modeling for oil sands was as follows. Firstly, multi-attribute analysis was conducted to obtain local facies probabilities. Secondly, sequential indicator simulation with locally varying proportion was employed for facies modeling, where the local proportion was provided from the local facies probabilities. Then, sequential Gaussian simulation with collocated cokriging was carried out for each facies to estimate mudstone volume distribution. Finally, effective porosity and permeability were estimated as a function of the mudstone volume.