Grid Card (EOR-BO)

The STOMP simulator’s integral finite difference formulation is based on orthogonal grid systems. Currently, three orthogonal grid systems are recognized: Cartesian, cylindrical, and boundary fitted (or curvilinear). The Cartesian coordinate system is a “right-handed” system with the longitudinal axis (z–direction) aligned with the negative gravitational vector. Cartesian coordinate systems may be defined to be tilted with respect to the gravitational vector. The cylindrical coordinate system has the longitudinal axis (z-direction) aligned with the negative gravitational vector. The radial (r–direction) and azimuthal (θ-direction) axes are constrained to a horizontal plane. The boundary fitted coordinate system allows for curvilinear boundaries. This coordinate system requires the number of grid points in each direction as input variables, and the coordinates are read in via an external grid file.  Four different types of external grid files are recognized: 1) boundary fitted, 2) Generic Eclipse, 3) EarthVision Sampled Input and 4) Element and Vertices.  The boundary fitted file requires the specification of the locations of the x-direction vertices followed by the y-direction vertices, followed by the z-direction vertices. It is assumed that adjacent grid cells have co-located vertices. The Element and Vertices specification requires specification of 8 vertices for each grid cell, and an element file identifying which vertices define each grid cell. This grid option allows for displaced adjacent grid cells.

For the Cartesian coordinate system, the terms west, south, and bottom refer to the negative x-, y-, and z-directions, respectively, and the terms east, north, and top refer to the positive x-, y-, and z-directions, respectively. For the cylindrical coordinate system, the terms west, south, and bottom refer to the negative r-, θ-, and z-directions, respectively, and the terms east, north, and top refer to the positive r-, θ-, and z-directions, respectively. Negative dimensional values are not recognized, and axes are defined positive toward increasing grid cell numbers. The grid dimensions that are specified on the Grid Card refer to cell surfaces; therefore, for grids with non-uniform spacing, for each grid direction the number of entries required is one plus the number of grid cells.  Grid cell volumes are defined by their bounding surfaces. Cylindrical coordinate systems are restricted to azimuthal axes which are less than or equal to 360 degrees. 

• Descriptions of the various grid card options (i.e.,cartesian, cylindrical, and boundary fitted) are provided on the Card Options page.

• Formatting instructions for specifying the grid are provided on the Card Syntax page.

• Examples of Grid Cards for STOMP-EOR-BO are provided on the Card Examples page.