4.5.9 Manage Layer Properties

Layer Properties - Definition window is accessible:

• by clicking the icon in the Layer Properties - Selection window of the Layer Modeling module;
• via Survey > Manage > Layer Properties... menu.

• Available property types: a hard-coded list of available property types.

Please contact support if you would like to extend the list of Available property types.

• Defined usable properties: a list that contains layer properties available in the current OpendTect project. Some of the most commonly used properties are pre-defined for a user (for example, Acoustic impedance property of the Impedance type).

The type of an existing property can not be changed. A new property of the desired type has to be created instead.

• Store: a level at which layer properties are stored.
  • For this survey only: (default option) properties are saved at the root of the survey, applicable for all users only for this survey.
  • As default for all surveys: properties are saved in the parent Survey Data Root directory (where all OpendTect surveys are located), applicable for all users and all surveys.
  • As default for my user ID only: properties are saved to home/.od file, which has the priority over the two other sources.

The only way to restore the default OpendTect list of properties is to delete the Properties files at all levels.

Available actions include:

• Add usable property: select a property type in Available property types list and click on to pop up the Property definition window.
• Edit usable property: select a property in the list and click on icon (or double-click on a property name) to pop up the Property definition window.
• Remove usable property: select a property in the list and click on icon.

The minimum possible list of properties must include at least one log for each of the following types: Density, Velocity and Impedance.

Property definition window:

• Name: a unique layer property name.
• Aliases (optional): specify possible aliases (useful to associate the correct log to a property: logs with different names can thus be related to the same property).
• Default Display Color: a default color for a log display.
• Typical value range: a typical value range for a property with associated units.
• Default Value (optional, but recommended): type in a numeric value or click on Formula ... to set a mathematical formula in the Math property window (use RockPhysics library to retrieve standard ones). Default Value is used to auto-fill property values in layer definition windows (see Layer Modeling chapter), and the auto-filled value can be changed for individual layers.
• Fixed definition (optional, but recommended for some properties: see the tip below): type in a numeric value or click on Formula ... to set a mathematical formula in the Math property window (use RockPhysics library to retrieve standard ones). A property with Fixed definition doesn't appear in layer definition windows (see Layer Modeling chapter) as it is always auto-computed in the background.

A combination of well chosen Default Values and Fixed definitions can significantly ease and speed up the modeling process. Default Values should be preferably set for all properties and should be chosen such that they roughly represent most of the modeled media. For example, specify the default density corresponding to encasing shales and later in the modeling workflow modify the auto-filled values only for target sand layers. Fixed definition is recommended for the properties which are defined by specific formulas (i.e. never modeled directly, irrespective of a geological setting): Acoustic and Shear Impedances, Vp/Vs and Poisson’s Ratios, Lambda-Rho, Mu-Rho, etc.

The example below shows Density with a Fixed definition using Gardner's empirical relation from Sonic values.

Math formulas can be optionally saved for later use and restored via and icons respectively.