RESERVOIR MODELING OF DEEPWATER CLASTIC SEQUENCES: MESOSCALE ARCHITECTURAL ELEMENTS, ASPECT RATIOS AND PRODUCIBILITY

Abstract

ABSTRACT The geoscientist is usually the provider of semi-quantitative data on deepwater clastic architectural elements in the integrated reservoir modeling process. These data can take the form of aspect ratios, vertical and lateral frequencies, or orientations. The arrangement and internal variability of the elements determines the ratio of vertical to horizontal permeability (KV/KH), lateral continuity, and connectivity of the full reservoir model. These three factors ultimately determine the reservoir behavior or producibility. In high net/gross deepwater clastic systems, connectivity of the reservoir is not usually a problem. The size and distribution of architectural elements such as high permeability zones and permeability barriers affect the KV/KH and lateral continuity of reservoirs. Permeability barriers may take the form of shale, concretionary layers, and sandstone that is poorly-sorted. However, in low net/gross systems the lateral continuity of the reservoir “beds” and the presence, absence, and abundance of sedimentary injection features and bioturbation are critical to the connectivity and behavior of the reservoir. Stochastic models rely on the accuracy of the input variables, where knowledge of the aspect ratios of architectural elements is essential. Stochastic reservoir models of two fields are used as examples of how individual architectural elements might affect the reservoir performance.