STOMP User Guide

Grid Card Options

The grid card is used to specify the grid structure used with the STOMP simulator’s integral finite difference formulation. All STOMP grids are structured and orthogonal to nearly orthogonal, with hexahedral grid cells. Grids can be specified with either relative or absolute coordinates. In other words, STOMP does not require the origin to be at 0,0,0. Grids may be specified as map projections (ie., UTM or State Plane) with their corresponding units (meters or feet). However, geographic coordinate systems (ie., latitude-longitude) are not accepted. Vertical coordinates can be specified as elevation or as relative coordinates. The origin of STOMP grids is in the lower, left hand, front, corner. A number of different ways of specifying grids are available in STOMP.

Cartesian

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. Negative dimensional values are not recognized, and axes are defined positive toward increasing node numbers.

Uniform Cartesian

A “right-handed” system with the longitudinal axis (z-direction) aligned with the negative gravitational vector and uniform grid spacing. In this case, the grid cell dimension in each direction is specified.

Non-uniform Cartesian

A “right-handed” system with the longitudinal axis (z-direction) aligned with the negative gravitational vector and non-uniform grid spacing. Either the locations of the cell edges are specified, or the number of cells of each cell size are specified. In each case, there must be one more value than the number of grid cells specified in each corresponding direction.

Grid spacing can be specified in one of 2 ways:

Cell Surface Location

In this case, the absolute locations of the cell edges are specified and there is one more value than the number of grid cells in the corresponding direction. Cell edge locations can be specified using either a local or global coordinate system. Therefore, the origin of the grid need not be 0,0,0.
Count and Cell Size

In this case, the first value must be the cell surface location at the origin, but after that, the number of cells and the cell size can be specified using the count@cell size syntax. The grid can be specified using either a local or global coordinate system. Therefore, the origin of the grid need not be 0,0,0.

Tilted Cartesian

The entire domain is tilted with respect to the gravitational vector by a specified angle in each of the x-z and y-z planes. The grid spacing is specified as for the non-uniform cartesian case.

Cylindrical

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 node numbers.

Uniform Cylindrical

The longitudinal axis (z-direction) is aligned with the negative gravitational vector and the radial (r–direction) and azimuthal (θ-direction) axes are constrained to a horizontal plane. In this case, the grid cell dimension in each direction is specified.

Non-uniform Cylindrical

The longitudinal axis (z-direction) is aligned with the negative gravitational vector and the radial (r–direction) and azimuthal (θ-direction) axes are constrained to a horizontal plane. Either the locations of the cell edges are specified, or the number of cells of each cell size are specified. In each case, there must be one more value than the number of grid cells specified in each corresponding direction.

Cell Surface Location

In this case, the absolute locations of the cell edges are specified and there is one more value than the number of grid cells in the corresponding direction. Cell edge locations can be specified using either a local or global coordinate system. Therefore, the origin of the grid need not be 0,0,0.
Count and Cell Size

In this case, the first value must be the cell surface location at the origin, but after that, the number of cells and the cell size can be specified using the count@cell size syntax. The grid can be specified using either a local or global coordinate system. Therefore, the origin of the grid need not be 0,0,0.

Boundary Fitted (or Curvilinear)

This format allows for curvilinear boundaries and requires the vertices of each grid cell to be specified via an external grid file. This option assumes that adjacent grid cells have co-located vertices, requiring only ((nx+1)*(ny+1)*(nz+1)) vertex inputs. The number of grid cells in x, y and z, the filename, and the units are specified in the Grid Card.

Generic Eclipse Keyword File

This option reads a Generic Eclipse Keyword (.grdecl) file, typically exported from Petrel™. This option allows for curvilinear boundaries. The number of grid cells in x, y and z, the filename, and the units are specified in the Grid Card. The number of grid cells specified in the Grid Card must match what is specified in the generic eclipse file. The user also must specify a minimum z-direction spacing to avoid overlapping layers and negative cell volumes.

Earthvision Sampled Input

This option reads a file generated from data exported from the EarthVision® geologic modeling software package. This option allows for curvilinear boundaries. The number of grid cells in x, y and z, the filename, and the units are specified in the Grid Card.

Element and Vertices File

This option requires the specification of eight vertices for every node, (i.e., (nx*ny*nz)*8) via an external grid file. The number of nodes in x, y and z, the filename and the units are specified in the Grid Card.