Converting logs to net rock logs

A net rock log is a log defining 'net' and 'non-net' intervals along a wellbore, where 'net' refers to reservoir and 'non-net' to non-reservoir rock. In the fluid model workflow, the net rock log acts as a filter on the fluid logs, effectively ignoring the non-net sections. With the Convert to Net Rock Log form (model > Fluids > Conversion Tools > Convert to Net Rock Log) you 'translate' a discrete log (for example a facies log) into a log defined by 'net' and 'non-net' intervals. When you have created a net rock log, you can use it (together with fluid logs) to determine the fluid levels in the compartment-based fluid model calculations of the Fluid Levels step in the Fluid Modeling workflow. When a net rock log, together with a fluid log, is assigned to a fluid model, the fluid levels are calculated for a compartment, based on the aggregated fluids information of the wells intersecting that compartment, taking into consideration the fluid logs only for intervals identified as 'net' in the net rock log.

Net rock logs that you create with the Net Rock Log form are not to be confused with net-to-gross logs, which are typically based on Vshale cut-off criteria applied to Gamma Ray logs, and which eliminate non-productive intervals from the reservoir as part of net pay determination. In this respect, the net rock log has no connection with volumetric calculations.

To indicate the 'net', a name and (integer) number is used; Net (1) for the reservoir intervals, and Non-Net (0) for the non-reservoir intervals. The Convert to Net Rock Log form provides the functionality for creating a net rock log using the application naming convention. The input log can be any discrete property type and the log type of the resulting log is Net Rock.

The Map Net Rock table (with an example of a facies log):

Input Value	Net rock
Sand (0)	Net (1)
Silt (1)	Net (1)
Shale (2)	Non-Net (0)

Net rock log conversion

1. Select the discrete log that contains the information on the basis of which you can define the 'net' and 'non-net' intervals.

2. Choose between creating a new log and updating the existing log. The adjacent Name text field remains active if a new log is created; the name of the new log can be provided in this field. Updated logs will retain their name and, as such, the Name text box is disabled.

   Important   When choosing to update a log that is of another property type than Net Rock (see the Inspector for the Property type of your log), the log will be converted from it's original log type (for example Facies) to Net Rock. You must be extremely careful when using the Update log option, as the original log is overwritten.
3. Each of the classes belonging to the selected input log will appear in the 'Map Net Rock' table under the Input Value column. For each class you can specify the 'net' and 'non-net' by clicking into the net rock column and selecting the relevant value in the drop-down list. Select the 'net' and 'non-net' for each of the log classes as needed.
4. Click Apply to create or update the log and keep the form open for additional work. Otherwise, click OK to create or update the log and close the form. The created log is available in the JewelExplorer under the All Logs item.