Seismic Data Can Improve Stochastic Facies Modeling

Summary Heterogeneous reservoir units comprised of fluvial channel sandstones that alternate vertically and laterally with finer grained, nonreservoir lithologies pose a serious problem to production drilling and field development planning. The interwell position of each reservoir sandstone body can be assessed, in most cases, only indirectly through conventional geological well-correlation and mapping, and the potential of drilling unsuccessful production wells is usually present. The scope of this paper is to present a new technique that ensures that information obtained from 3D seismic surveys is fully utilized in the discrete facies modeling of fluvial sandstone bodies in a heterogeneous reservoir unit. In our study area, we show that there is a useful, empirical relationship between seismic impedance and the facies (channel sandstones/nonreservoir). Notably, there is a high probability of obtaining channels in low impedance regions, whereas high impedance areas have a lower probability of channels. An opposite impedance behavior may occur in other reservoir environments. This relationship is utilized to guide the discrete modeling of channels. An example from a fluvial North Sea reservoir is presented. The use of seismic data as an additional source of conditioning data reduces the uncertainty in the stochastic reservoir model, because the uncertainty in the reservoir description in the interwell areas is reduced significantly.