After an attribute grid is generated, it can be used to calculate volumetrics and other properties.
To calculate volumetrics, go to the Volumetrics panel from the Tools pull down menu. Enter the cutoff values for Cutlow and Cuthigh. For example, when the attribute is volume of clay, you may use Cutlow=0 and Cuthigh=0.4. To exclude the volume below water oil contact, enter a WOC value in subsea elevation. To exclude the volume above gas oil contact, enter a GOC value in subsea elevation. Then click the Update button to update the volumetrics numbers. To change the display unit, go to Vol.Unit list and select English or Metric.
Different attributes may be used to determine the pay volume. Besides the generic attribute grid, other grids (if available) such as lithology, geobody, porosity, or permeability may be selected as ActiveGrid. If porosity grid is available, it may be checked to be used in the pore volume calculation, otherwise the AV.Porosity value will be used. If (oil) saturation grid is available, it may be used in the HCPV (hydrocarbon Pore Volume) calculation, otherwise the AV.Oil Sat. value will be used.
To calculate the volume within part of the grid layers, enter the desired Top Grid Layer and Bottom Grid Layer numbers inclusive. If the active grid is loaded into memory (after graph) with horizons, the Top and Bottom selections may be used. The Top and Bottom lists consist of three parts separated by ":". The first number is the sequence number of the horizon. The second number is the grid layer sequence number. The third part is the name of the horizon, which is from the marker set. If there are more markers than horizons in the grid, the number of active markers should be the same as number of horizons in the grid for the marker names to show up. There is no depth checking, therefore it is up to the user to select the correct active marker for the correct marker names to show up.
To limit the volume calculation within a specific area, import a polygon boundary or pick a polygon boundary on basemap from the DataQC panel, then check the Within Boundary option.
To calculate geobodies, go to the Volumetrics panel from the Tools pull down menu and enter the cutoff values for Cutlow and Cuthigh. For example, when the attribute is volume of clay, you may use Cutlow=0 and Cuthigh=0.4 to identify sand bodies. The Connected-Limit is initially 0 which means any connected sand will be treated as the same geobody. By changing the Connected-Limit to 0.2, for example, geobodies are further divided up so that some of them may be connected partially. From the Map button on the lower right of the Volumetrics panel, select Geobodies. This calculation may take a while if the grid is large. A grid of Geobody ID is generated which may then be graphed or used in volumetrics calculations.
To map vertical average, net thickness etc., also use the Volumetrics panel and the Map button on the lower right. After closing the Volumetrics panel, the calculated map or Geobody ID can be selected from the grid list on the lower right of the GridOutput panel. It is necessary to have a porosity grid (file extension C6) for Phi*H and a permeability grid (file extension C7) for K*H map generation. See Multiple Data Types and Cross Plot on how to make gridding output porosity or permeability grid.
Gross Thickness map corresponds to gross volume and is the rock volume within boundaries. Boundaries include polygon boundary (if enabled), GOC, WOC, Top Grid Layer and Bottom Grid Layer. Net Thickness map corresponds to net volume and is the portion of gross thickness within pay Cutlow and Cuthigh. Phi*H map corresponds to pore volume and is porosity times net thickness. HC Thickness map corresponds to HCPV (HydroCarbon Pore Volume) and is saturation times porosity times net thickness. K*H is permeability times net thickness. Because the calculation is done in 3D, the porosity and saturation values in each cell will be used in the calculation.
For complex WOC or saturation distribution, a saturation grid should be considered.
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