Structural framework Incorporating the spatial positions of the major formation boundaries, including the effects of
faulting,
folding, and
erosion (
unconformities). The major stratigraphic divisions are further subdivided into layers of cells with differing geometries with relation to the bounding surfaces (parallel to top, parallel to base, proportional). Maximum cell dimensions are dictated by the minimum sizes of the features to be resolved (everyday example: On a digital map of a city, the location of a city park might be adequately resolved by one big green pixel, but to define the locations of the basketball court, the baseball field, and the pool, much smaller pixels – higher resolution – need to be used).
Rock type Each cell in the model is assigned a rock type. In a coastal
clastic environment, these might be beach sand, high water energy marine
upper shoreface sand, intermediate water energy marine
lower shoreface sand, and deeper low energy marine
silt and
shale. The distribution of these rock types within the model is controlled by several methods, including map boundary polygons, rock type probability maps, or statistically emplaced based on sufficiently closely spaced well data.
Reservoir quality Reservoir quality parameters almost always include
porosity and
permeability, but may include measures of clay content, cementation factors, and other factors that affect the storage and deliverability of fluids contained in the pores of those rocks.
Geostatistical techniques are most often used to populate the cells with porosity and permeability values that are appropriate for the rock type of each cell.
Fluid saturation grid used in
MODFLOW for simulating groundwater flow in an aquifer. Most rock is completely
saturated with
groundwater. Sometimes, under the right conditions, some of the pore space in the rock is occupied by other liquids or gases. In the energy industry,
oil and
natural gas are the fluids most commonly being modelled. The preferred methods for calculating hydrocarbon saturations in a geological model incorporate an estimate of pore throat size, the
densities of the fluids, and the height of the cell above the
water contact, since these factors exert the strongest influence on
capillary action, which ultimately controls fluid saturations.
Geostatistics An important part of geological modelling is related to
geostatistics. In order to represent the observed data, often not on regular grids, we have to use certain interpolation techniques. The most widely used technique is
kriging which uses the spatial correlation among data and intends to construct the interpolation via semi-variograms. To reproduce more realistic spatial variability and help assess spatial uncertainty between data, geostatistical simulation based on variograms, training images, or parametric geological objects is often used, e.g.
Mineral Deposits Geologists involved in
mining and
mineral exploration use geological modelling to determine the geometry and placement of
mineral deposits in the subsurface of the earth. Geological models help define the volume and concentration of minerals, to which
economic constraints are applied to determine the economic value of the
mineralization. Mineral deposits that are deemed to be economic may be developed into a
mine. == Technology ==