Rapid Multiple-Scenario Depth Structure Risk Analysis Case Study In Cuulong Basin, Vietnam.

Depth conversion uncertainty is a critical factor for drilling fractured granite basement targets with<br>highly deviated well trajectory in Cuu Long Basin, Vietnam. This paper illustrates depth conversion using 3D<br>velocity model that calibrates many sources including seismic velocities, time depth functions, well picks and<br>surfaces. Various assumptions of velocity interpolation employing different data inputs were evaluated<br>systematically in order to see their effects on the model. Four sensible assumptions were chosen to generate<br>“what if” scenario velocity models to capture the uncertainty. Case study done on this area using the method<br>described above has produced the base case or “most likely” case, the high case and the low case. The result<br>suggests that actual basement depth is deeper than previously predicted. The previous velocity model used<br>was created based on single time-depth function from a nearby well.