abaqus geostatic step balance gravity

[xwang18]

Hello,

I am modeling oil production using ABAQUS. The geometry is an cuboid reservoir. I have a problem about balancing gravity.

Boundary conditions: The reservoir is fixed in the horizontal direction at each side. The bottom part of this reservoir is fixed. No lateral strain is allowed on horizontal displacements. Overburden pressure is 30 Mpa

Materials:
*Elastic
4e+10, 0.2
*DENSITY
2.5e3
*Permeability, specific=10000.
2e-7, 0.15

*initial conditions, type=field, variable=1
allelem, 0
*initial conditions, type=ratio
allelem, 0.333
*initial conditions, type=pore pressure
allelem, 30e6, 0, 30e6, 20
*initial conditions, type=stress, geostatic
allnode, 30e6, 0, 30e6, 20, 0.571428

*Step, name=balance
*Geostatic
*Dsload
top, P, 30e+06
bottom, P, 30.6e+06
*Dload
soil-1, GRAV, 10, 0., 0., 1.

The balance step(shown above) of the analysis is to ensure an equilibrium geostatic stress field (geostatic stress to balance gravity loading).
However, outputs are not correct.
Could anyone give me a advice? Thanks very much