Robust Coarse Scale Modeling of Flow and Transport in Subsurface Formations
Abstract
Subsurface flows are affected by permeability heterogeneity over a range of length scales. It is difficult to fully resolve all of the scales that impact flow and transport through such systems, so models for subgrid effects are often required. In this work, new methods for the coarse scale modeling of flow (i.e., total flow rate for specified wellbore pressures) and transport (movement of injected fluid) in highly heterogeneous deterministic systems are described and applied. The technique for the improved upscaling of flow, referred to as adaptive local-global upscaling, efficiently provides coarse scale transmissibilities (transmissibility is the numerical analog of permeability) that are adapted to a specific flow scenario. Global coarse scale simulations are used to determine the boundary conditions for the local calculation of upscaled properties and a thresholding procedure is introduced for efficiency and to minimize the appearance of spurious transmissibility values. A specialized near-well upscaling is included naturally in the procedure and transmissibilities can be efficiently recomputed when new wells are introduced. The method is applied to both 2D and 3D systems and its improved accuracy over existing procedures is demonstrated. The adaptive local-global transmissibility upscaling is then combined with models for transport. Two approaches are considered for the transport problem. First, a multiscale (dual-grid) technique is presented, in which the fine scale velocity, reconstructed from the coarse scale pressure solution, is used for the solution of advective contaminant transport on the fine scale. This approach provides excellent accuracy but it requires that two grids be used for the simulation. A new generalized convection-diffusion model for transport (so named because of the form of the subgrid terms), in which both flow and transport (single-phase or two-phase) are solved on the coarse grid, is described next. The method is shown to provide significantly improved results compared to those attainable with standard procedures. It is also shown to be well-suited to difficult problems in which well rates or locations change in time.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFM.H14B..02D
- Keywords:
-
- 1829 Groundwater hydrology;
- 1832 Groundwater transport