SPE Journal
Volume 15, Number 1, March 2010, pp. 7-17

Summary

Full-field flow simulators use a variety of cell geometries, ranging from simple rectangles to complex corner-point systems. One of the benefits of corner-point cells is the ease with which we may represent faulted reservoirs. Each face of a cell may be juxtaposed to two or more cells, depending on the fault throw and the lateral displacements of adjacent cells. Conventional finite-difference approaches routinely include the flux between these cells as "non-neighbor" connections. Other examples of non-neighbor or nonstandard connections occur at the boundary of local grid refinement (LGR) or local grid coarsening (LGC) regions where two computational grids come into juxtaposition. In each of these instances, the velocity across the nonstandard faces of a cell will be unevenly distributed according to the non-neighbor fluxes. In contrast, the standard streamline velocity interpolation model (Pollock's scheme) used within a cell assumes that the flux is evenly distributed on each cell face, inconsistent with the non-neighbor connection fluxes. Streamlines traced with such an approach do not have sufficient degrees of freedom to be consistent with the finite-difference fluxes and, consequently, will not follow a physical flow path.

We propose a strategy that provides a consistent representation for streamlines and velocities near faults and non-neighbor connections. Our approach is based on a simple local (boundary layer) refinement construction that can be used to honor the fluxes at each face, without affecting the representation of flow within the cell or on any other cell face. The local refinement construction is the simplest extension to three dimensions for faulted reservoir cells that provides consistency with the finite difference flux calculation. Several examples will be presented for a single pair of cells juxtaposed across a fault and at LGR boundaries to illustrate the difficulties in conventional tracing algorithms and the benefits of our approach. The practical utility of our algorithm is demonstrated in a structurally complex and heavily faulted full-field model. The reservoir geometry includes multiple cells with complex fault juxtaposition and several non-neighbor configurations in different faces. This treatment is contrasted with the usual approach, and the implications for reservoir scale fluid flow tracing by streamlines is examined

© 2009. Society of Petroleum Engineers

View full textPDF ( 1,100 KB )

History

• Original manuscript received: 12 February 2008
• Meeting paper published: 20 April 2008
• Revised manuscript received: 13 February 2009
• Manuscript approved: 13 March 2009
• Published online: 17 November 2009
• Version of record: 12 March 2010