Hierarchic Modeling and History Matching of Multiscale Flow Barriers in Channelized Reservoirs

Abstract

AbstractChannelized reservoirs often consist of multi-scale architectures containing large-scale channel belts, middle-scale single channels and small-scale channel infill components. These architectural elements are defined between bounding surfaces. Along these hierarchical bounding surfaces, thin shale drapes may be present as flow barriers that compartmentalize the reservoirs. Since the distribution of shale drapes is dominated by these bounding surfaces they themselves form a multi-scale reservoir heterogeneity. Characterizing the distribution of these multi-scale flow barriers calls for a hierarchical modeling and history matching approach to integrate all data available. In this hierarchic approach the large-scale reservoir architecture is modeled first, the shale drapes are then simulated within this architecture framework.The reservoir architecture modeling in this paper involves defining channel deposition fairways (valleys) based on seismic data, modeling long sinuous channels and placing them into defined fairways such that all data are matched. This paper adopts a stratigraphic-based modeling approach. In this stratigraphic-based approach, individual channels are simulated using the YACS method (Alapetite et al., 2005). This method is fast and conditions to well data under the assumption that channel sand can be identified in the well data. To stack multiple channels reproducing a desirable stacking pattern, the migration ratio and overlap ratio are used as input parameter of the simulation process. Once the large-scale reservoir architecture is modeled, the bounding surfaces are record, next, the shale drapes are simulated along these surfaces using multiple-point statistics techniques. To match the production data, channel location and the number of channels are perturbed using the gradual deformation method, the continuity of shale drapes is perturbed using the probability perturbation method.A 3D synthetic example is presented to demonstrate this modeling approach: the multi-scale shale drapes are modeled and perturbed while the reservoir geological concepts are preserved. This hierarchic modeling approach allows integrating different data at their relevant scale.