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Saturations of Migrating Buoyant Fluids From Invasion Percolation Flow Simulation Using Small-Scale, High-Resolution Geologic Models With Realistic Heterogeneity

Abstract

This study addresses the influence of lithologic heterogeneity at the sub-meter scale on the flow of buoyant fluids for different types of clastic sedimentary architectures from representative depositional environments. To adequately represent 3D heterogeneity, we present innovative techniques for generating digital models that combine a well-documented deterministic and descriptive bedform architecture component mimicking realistic crossbedding geometries with stochastic variability of petrophysical properties. One advantage of this approach is that it allows consideration of domain sizes larger than whole core and core plugs typically used for laboratory flow experiments, where small sizes may not fully capture depositional architecture. The main contribution of this study is the development of a predictive model for saturation estimation based on a comprehensive, yet simplified, set of geological models resembling a range of well-characterized and documented fluvial clastic facies. Basic geological features such as grain size distribution and sedimentary bedform architecture can be used to predict the fluid saturation during capillary/buoyancy-dominated flow conditions. These models are unique in regard to their geological realism and permit evaluation of the impact of sub-meter scale capillary heterogeneity on buoyant fluid flow scenarios that are relevant to petroleum migration, residual saturations (ROZ), and CO2 flow. The digital models themselves expand characterization opportunities using a number of methods, including upscaling, connectivity, and bulk property anisotropy. Saturation results from simulations of small-scale domains can be used to benchmark expected values in larger reservoir scale domains.