Changes

using-and-improving-surface-models-built-by-computer_fig19.png|{{figure number|19}}The cell's corners are defined by grid nodes. The top is defined by two or more planes passing through the node z values and lie inside the polygon. The prism of volume under each plane is calculated and added to volumes for all other prisms inside the polygon.

using-and-improving-surface-models-built-by-computer_fig19.png|{{figure number|19}}The cell's corners are defined by grid nodes. The top is defined by two or more planes passing through the node z values and lie inside the polygon. The prism of volume under each plane is calculated and added to volumes for all other prisms inside the polygon.

using-and-improving-surface-models-built-by-computer_fig20.png|{{figure number|20}}A mathematical surface is fit to the grid cell. Calculus is used to integrate the volume under the curve, inside the grid cell, and inside the polygon. All cell volumes inside the polygon are added together.

using-and-improving-surface-models-built-by-computer_fig20.png|{{figure number|20}}A mathematical surface is fit to the grid cell. Calculus is used to integrate the volume under the curve, inside the grid cell, and inside the polygon. All cell volumes inside the polygon are added together.

using-and-improving-surface-models-built-by-computer_fig21.png|{{figure number|21}}Thickness Is normally defined by grids representing the top and base of reservoir and the fluid contact(s).]]

using-and-improving-surface-models-built-by-computer_fig21.png|{{figure number|21}}Thickness Is normally defined by grids representing the top and base of reservoir and the fluid contact(s).

using-and-improving-surface-models-built-by-computer_fig22.png|{{figure number|22}}The gross hydrocarbon rock thickness is progressively reduced by net to gross ratio, average porosity, and oil saturation, until only the thickness of pores filled with hydrocarbon remains.

using-and-improving-surface-models-built-by-computer_fig22.png|{{figure number|22}}The gross hydrocarbon rock thickness is progressively reduced by net to gross ratio, average porosity, and oil saturation, until only the thickness of pores filled with hydrocarbon remains.

using-and-improving-surface-models-built-by-computer_fig23.png|{{figure number|23}}The envelope technique is used to define one grid for the top of reservoir and another for the base of the reservoir. These are subtracted to create the gross hydrocarbon rock thickness.

using-and-improving-surface-models-built-by-computer_fig23.png|{{figure number|23}}The envelope technique is used to define one grid for the top of reservoir and another for the base of the reservoir. These are subtracted to create the gross hydrocarbon rock thickness.

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Estimates of volumes are normally calculated between two structure surfaces, above a fluid contact, or sometimes below another fluid contact.

Estimates of volumes are normally calculated between two structure surfaces, above a [[Fluid contacts|fluid contact]], or sometimes below another fluid contact.

===The volumetrics algorithm===

===The volumetrics algorithm===