A Strategy for Modeling Lithology within Faulted & Subsiding Basins Using RockWorks16

This case study involves a faulted and subsiding basin in which the faults do not extend above younger sediments. To model this geology, five data sets were used:

  1. downhole lithology logs (Figure 1),
  2. a surface topography model (not shown),
  3. two fault “ribbons” (not shown),
  4. a reference surface based on a gravity survey – for “warping” the interpolations into the basin (Figure 4), and
  5. an unconformity surface (Figure 7) that defines the contact between the younger, unfaulted sediments and the older, faulted units.

The younger and older sediments were independently modeled, using the unconformity surface as the common boundary and then combined into a final model (Figure 12). The sediments above the unconformity were modeled without faulting or warping (Figure 8). The sediments below the unconformity were modeled with faulting and warping (Figure 10). Finally, the upper and lower models were combined (Figure 12) to create a model in which the upper units are relatively flat-lying and unfaulted while the lower units effectively subside into the basin.

Index to Diagrams

  1. Boreholes from which models were generated.
  2. Lithologic model without faulting or warping.
  3. Lithologic model with faulting but without warping.
  4. Reference surface used for model warping.
  5. Lithologic model using warping but without faulting.
  6. Lithologic model using warping and faulting.
  7. Unconformity surface representing contact between lower, faulted geology and younger, unfaulted geology.
  8. Lithologic model above unconformity. Neither warping nor faulting were used.
  9. Lithologic model below unconformity using both warping but not faulting.
  10. Lithologic model below unconformity using both warping and faulting.
  11. Combined lithologic models below (with warping but without faulting) and above (no warping or faulting) unconformity.
  12. Combined lithologic models below (with warping and faulting) and above (no warping or faulting) unconformity.

All modeling was performed with the lateral extrusion algorithm.

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