Autochthonous Salt Deformation Integrated

with Basin Modeling

Example on a GulfSpan Dip Line

Present Day

Allochthonous Salt

Autochthonous Salt

Basement

159 MYBP

• The Sediment temperature history is calculated with an energy balance and a heat flux boundary condition at the base of the model and a surface temperature boundary condition

• Taking the initial autochthonous salt thickness as the present day thickness results in the top geometry.

• Assuming that the autochthonous salt deforms according the principle shown in Figure 3 of the text suggests an initial salt thickness shown in the bottom geometry.

• Advance the slide to view a time history of autochthonous salt deformation.

159 MYBP

144 MYBP

102 MYBP

93.5 MYBP

65 MYBP

33.7 MYBP

23.80 MYBP

20.47 MYBP

19.74 MYBP

16.40 MYBP

14.06 MYBP

13.05 MYBP

11.20 MYBP

8.55 MYBP

7.97 MYBP

5.32 MYBP

4.10 MYBP

3.83 MYBP

2.60 MYBP

1.65 MYBP

1.45 MYBP

0.50 MYBP

0.27 MYBP

0.23 MYBP

Present Day

Discussion• Lateral changes in vertical effective stress leads to deformation of

autochthonous salt– Sedimentation rate determines the loading history– The distribution of permeable sand has a significant effect on the vertical

effective stress

• Sediment temperature near the salt is significantly affected by the autochthonous salt history– Source rock maturation is decreased by millions of years when the source rock

is above the salt

• This development assumes that all the salt deformation occurs in autochthonous salt– The reality is that allochthonous salt plays a large role in basin development

• Including allochthonous salt deformation would require a full stress simulation at every time step– Gradients in lateral stress become important at shallow depths– Simulations would require regridding at each time step to account for the

mass and momentum transport of allochthonous salt across time lines