Rock Properties

Strength, friction and other rock data is specified on the Rock Properties form (advanced stress & failure > Setup > Rock Properties or wellbore stability > Setup > Rock Properties). As with the selection of stresses on the Sv Principal Stress form, the data used here can be calculated as part of the 1D model workflow or imported separately.

For each of the rock property inputs you can choose a log, or specify a constant value. If you are working with a case that has had the 1D model workflow performed, the calculated rock properties are automatically selected, though you can change these if necessary.

Instead of selecting logs as the input data for the rock properties, you can specify constant values using the Advanced Mode form.

To specify the rock properties:

For each of the properties, select a log or define a constant:

UCS Select a log or select the use constant box and enter a value. By default, the Unconfined Compressive Strength (Case) log created in the Rock Properties workflow form is initially selected, if available.

Internal Friction Select a log or select the use constant box and enter a value. By default, the Internal Friction Coefficient (Case) log created in the Rock Properties workflow form is initially selected, if available.

If you select constant, changing the unit from 1 to degrees allows you to see the internal friction coefficient converted into the friction angle.

Poisson's Ratio Select a log or select the use constant box and enter a value. By default, the Static Poisson’s Ratio (Case) log created in the Rock Properties workflow form is initially selected, if available.

Tensile Strength The default selection for Tensile Strength is to define a constant. You can select a log if available.

Biot Coefficient Parameter used in poroelasticity which describes for a porous and fluid-saturated rock how much of a change in confining pressure is transferred to the pore pressure under conditions when fluid cannot escape from the pores. The Biot coefficient is given by 1 – Cs/Cm, in which Cm is the compressibility of the rock and Cs is the compressibility of the solid material/crystals that make up the rock. Since Cs <= Cm, the value lies between 0 and 1. For highly porous media Cs is much smaller than Cm and the coefficient comes close to 1, which in most cases is taken as the standard value.

When not using the specified coefficient of the rock types in the case, you can use a default value by checking the use constant box, located below the Biot Coefficient drop down box, and specifying a value.

Currently, the Biot Coefficient is used to calculate effective stresses; otherwise, it is an elastic material model.

After making your selections, click OK to proceed to the Failure Criterion selection.