AQUIFER HETEROGENEITY IN CHANNEL-BELT DEPOSITS, PART 2. COMPUTATIONAL CHALLENGES IN SIMULATING STRATAL ARCHITECTURE, FLOW, AND TRANSPORT

We have developed a highly scalable code that simulates the hierarchical stratal architecture formed by braided rivers. The code first creates a geometric model of the stratal architecture. The stratal units are created at each hierarchical level, and a level N unit is the bounding surface for an assemblage of level N-1 unit types. For a given level, creating an occurrence of a unit type starts with an archetypal geometry. The archetypal geometry is a polyhedron defined by piecewise planar elements. Archetypal shapes of the depositional units at each level of this hierarchy were created based on published observations and measurements.The code then creates a digital model as a 3-D cubic lattice by sampling the geometric model. At each level, the voxel is assigned to one polyhedron in the final model, based on rules consistent with knowledge of depositional processes and whether boundaries represent erosional or conforming surfaces. In this manner, the algorithm assigns only one unit type for each hierarchical level to a voxel. The digital model is then populated with permeability values defined by the mean and variance of permeability for unit types at only the lowest level (centimeter scale) of the hierarchy.

The stratal model and the corresponding permeability distribution are being used in multi-scale flow and transport simulations. We discuss preliminary results and challenges.