11 Grids

A grid is a RESQML representation that provides a cellular discretization of space. A grid shares three important characteristics with all other RESQML representations:

• A description of the topology (indexing) and geometry of the grid representation.
• A grid, or a subrepresentation of a grid, may provide a representation of an interpretation of a RESQML geologic feature, most often an earth model or a structural organization.

• Properties may be attached to a grid representation, i.e., a grid supplies the topological support for properties.

For information on concepts shared across all RESQML representations, see 6 Representations (Shared Concepts) .

RESQML also provides a closely related “grid connection set” representation, which is based on “cell-face-pairs”, for the purpose of describing the connections between grid cells, and a “blocked wellbore” representation to describe wellbore trajectories discretized on a grid.

Although it may seem reasonable to organize grids by the geometry of their cells, industry applications more naturally segregate grids by their topology, i.e., the dimensionality of the indexing of the cells. RESQML follows this approach and supports six distinct grid classes:

• Three grid classes are fundamental and will be recognizable to most practitioners.

• Three grid classes are combinations of these fundamental classes, and provide support for advanced variations in unstructured grids.

All grids support various extensions, such as higher order cell geometry, although some extensions may only exist for particular classes. For example, only IJK grids support radial grid cell interpolation. The corner point grid supported by many applications is a specific example of an IJK grid, although without all of the extensions now supported in RESQML. This chapter provides:

• A "quick start" to grids, which provides advice on the use of those features that are most basic for export/write and import/read of RESQML grids.
• Detailed sections that describe the objects that contribute to each of the grid classes and how they may be used.
• Examples of the various types of grids.

NOTE: In RESQML v2.0.1, capabilities for modeling streamlines have been added. For more information, see 17.3 Streamlines .