Calculating maximum horizontal stress from the equilibrium ratio method

The Shmax/Equilibrium method (1D MODEL > Horizontal Stress > Shmax/Equilibrium Ratio) allows you to set the SHmax parameter based on one of the three stress states defined by frictional faulting theory. The three stress states are as follows.

  • Normal faulting  A normal faulting stress regime requires that SHmax is the intermediate principal stress magnitude, Shmin is the least principal stress, and Sv is the maximum principal stress.
  • Strike-slip faulting  Strike-slip faulting and reverse faulting regimes require that SHmax is the maximum principal stress magnitude. For strike-slip, Shmin is the least principal stress and Sv is the intermediate principal stress.
  • Reverse faulting  Sv is the least principal stress and Shmin is the intermediate principal stress.

To define the SHmax magnitude as a fixed stress ratio, click the button in Step 2 to choose the appropriate stress state. The availability of the stress state options is dependent on the relative magnitudes of the overburden and the least horizontal stress as defined previously. If Sv is greater than Shmin, all the three stress regimes are available. However, if you try to use the reverse fault regime, a warning message appears showing that this selection is not available with this scenario.

  1. Select the input logs for the overburden stress, minimum horizontal stress, and pore pressure parameters.

  2. Select the appropriate faulting regimes. For each regime you can also manually specify a ratio to use in the calculation.

    Normal Faulting  Select to apply a normal faulting regime to the calculation. A text field is also available to specify the ratio.

    Strike-Slip Faulting  Select to apply a strike-slip faulting regime to the calculation. The Frictional stress limit checkbox enables the ratio input fields.

    Reverse Faulting  Select to apply a reverse faulting regime to the calculation. The Frictional stress limit checkbox enables the ratio input fields.

  3. Click Re(Calculate) to calculate the SHmax / Equilibrium Ratio.

The resulting maximum horizontal stress log populates the SHmax from equilibrium ratio text field. After the log is generated, click Show to open the SHMax / Equilibrium Ratio View and observe the results in both normal and EMW references.

To change the default name of the created log, double click in the log field. The background turns blue, indicating you can edit the text. When done, click the green check mark to apply the changes.