Research paper3D spatial variation in vertical stress in on- and offshore Netherlands; integration of density log measurements and basin modeling results

- Sv in Dutch subsurface varies with depth, locally & laterally.
- Local Sv mostly < standard Sv.
- Largest deviations Sv in areas with thick Cenozoic sediments & salt structures.
- 3D basin modeling proved to be good tool to correct & extend log derived Sv.
- 3D basin modeling proposed for evaluation current & paleo Sv, also in between wells.

The principal vertical stress at a certain depth is equivalent to the weight of the overburden (rocks and pore fluids) at that depth. Vertical stress trends will be similar across areas with a simple layer-cake lithostratigraphic sequence and similar burial history. These conditions are not fulfilled for the lithostratigraphy and burial history of the onshore and offshore Netherlands. Burial histories vary over short distances and resulted in highs, platforms and (inverted) basins with different lithostratigraphic sequences and porosity distributions.Density log measurements and basin modeling results were used to assess the spatial variation of vertical stress in the Dutch subsurface. This paper presents the approach and assessed spatial variation in vertical stress. The 3D basin modeling proved to be a good tool for correcting and extending density log derived vertical stress-depth relations. Results show that the vertical stress varies spatially and that the vertical stress gradient is less than the standard gradient in large part of the area. The largest local deviations from the standard gradient occur in areas with a thick package of low density Cenozoic sediments and large low density salt structures, i.e. in the northern offshore. Relatively old and more dense stratigraphic units occur at relatively shallow depth on the highs and in strongly inverted parts of the Mesozoic basins. In these areas the vertical stress reaches and follows the standard vertical stress gradient at shallower depths than in other areas.