To constrain the model, frictionless boundary conditions are defined on the positive and negative X, Y, and bottom faces.

The following input creates node-set components for all boundary faces except the top face of the domain:

! CREATING THE NODE SETS FOR BOUNDARY CONDITIONS
NSEL,S,LOC,Z,-DEPTH
CM,BOTTOM,NODE
ALLSEL
NSEL,S,LOC,X,WIDTH/2
CM,POSX,NODE
ALLSEL
NSEL,S,LOC,X,-WIDTH/2
CM,NEGX,NODE
ALLSEL
NSEL,S,LOC,Y,WIDTH/2
CM,POSY,NODE
NSEL,S,LOC,Y,-WIDTH/2
CM,NEGY,NODE

The following input defines the frictionless boundary conditions:

! BOUNDARY CONDITIONS (ROLLER BOUNDARY CONDITIONS)
CMSEL,S,POSX
CMSEL,A,NEGX
D,ALL,UX,0
ALLSEL
CMSEL,S,POSY
CMSEL,A,NEGY
D,ALL,UY,0
ALLSEL
CMSEL,S,BOTTOM
D,ALL,UZ,0
ALLSEL

To model reservoir depletion, the following input decreases the pore pressure by DP (=10 MPa):

! DEPLETION
CMSEL,S,RESERVOIR
NSLE,S,CORNER
D,ALL,PRES,-DP

Pressure depletion is applied as a step boundary condition (KBC,1).