Hello everyone,

I am working on a 3D geomechanical model in Abaqus to simulate CO₂ sequestration, closely following the methodology described in the paper by Karimnezhad et al. (2014), "Investigation of caprock integrity for CO₂ sequestration...".

My primary goal is to correctly establish the initial in-situ conditions before starting the injection simulation. I would like to verify if my approach for setting up the Geostatic step is the correct and most robust method.

Here is a summary of my setup for the initial equilibrium:

1. Analysis Steps:

• Step-1: A Geostatic step to establish the initial equilibrium.
• Step-2: A Soils step to simulate the 10-year injection period.

2. Key Initial Conditions (Applied in the "Initial" Step):

• Initial Stress Field: I am using a Predefined Field with Type: Geostatic stress.
  • The vertical stress is defined as a linear gradient from -83.1 MPa at the top of the model (Vertical coordinate 1 = 0) to -96.25 MPa at the bottom (Vertical coordinate 2 = -532 m).
  • The anisotropic horizontal stresses are defined using Lateral coefficient 1: 1.08 and Lateral coefficient 2: 0.96, based on the paper's ratios (\\\$\\sigma_H/\\sigma_v\\\$ and \\\$\\sigma_h/\\sigma_v\\\$).
• Initial Pore Pressure Field: I am using a Predefined Field with Type: Pore pressure and a linear elevation distribution.
  • The pressure is defined as a linear gradient from 34.1 MPa at the top of the model (Vertical coordinate 1 = 0) to 39.69 MPa at the bottom (Vertical coordinate 2 = -532 m), reflecting the initial hydrostatic condition of the formation fluid (brine).

3. Loads and Boundary Conditions for the Geostatic Step:

• Load: A Gravity load with a magnitude of 9.81 m/s² is applied in the negative Z-direction during the Geostatic step.
• Boundary Conditions: Roller boundaries are applied to the sides of the model (U1=U2=0), and a pinned boundary is applied to the bottom (U3=0).

My Questions:

1. Is this the standard and most robust method to define an initial, anisotropic stress gradient that is in equilibrium with the body forces?
2. Specifically, is combining a Geostatic stress Predefined Field with a Gravity load in the Geostatic step the correct workflow to achieve the stress state described in the paper?
3. Are there any potential issues or conflicts I might have missed in this setup?

Any advice or confirmation from experienced users would be greatly appreciated.

Thank you for your time.

Best regards,