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Geometric Modeling of a Turbidite System: Roadmap to Pore Pressure Distribution

Abstract

The three-dimensional distribution of sedimentary facies in a turbidite reservoir is an important facet of turbidite reservoir appraisal. An integral part is evaluating the distribution of different reservoir properties (porosity, permeability, etc.) and the associated pore pressure distribution, to evaluate reservoir connectivity. This study utilizes data collected from the literature (including system confinement, stacking patterns, sand / mud content, and depositional loading to the system) in order to construct conceptual geometrical models of turbidite systems. Training images are imported into Petrel to distribute stochastically the hierarchical elements (e.g. lobes), and vary the compensational stacking patterns and system progradation. Using different styles of training images, several different classes of models are created to vary the lobe size, property distribution, and net to gross. Facies distribution within individual lobes is controlled by placing pseudo facies logs within the modeled area. Two different types of training images were utilized in this study. The first are based on a higher sand / mud ratio corresponding to a width to thickness aspect ratio of approximately 1500:1. The second contains a lower sand / mud ratio and a larger aspect ratio closer to 2000:1. Results show that the sand to mud ratio and geometrical characteristics of individual elements significantly control property distribution in a turbidite system. In summary, the geometrical and facies distribution variations within models created from various training images and driven by pseudo facies logs can be subsequently used to study the onset of abnormal pore pressure when lithostatically loaded using finite element analysis.