RAPID MULTIPLE-SCENARIO DEPTH STRUCTURE RISK ANALYSIS CASE STUDY IN CUULONG BASIN, VIETNAM

摘要

Depth conversion uncertainty is a critical factor for drilling granite fractured basement targets with highly deviated well trajectory in Cuulong Basin, Vietnam. This paper illustrates depth conversion using 3D velocity model that calibrates many sources including seismic velocities, time depth functions, well picks and surfaces. Various assumptions of velocity interpolation employing different data inputs were evaluated systematically in order to see their effects on the model. Four sensible assumptions were chosen to generate "what if scenario velocity models, subsequently different depth realizations to capture the uncertainty/risk. Case study done on this area using the method described above has produced the base case or "most likely" case, the high case and the low case of basement structure depth in a short time frame within the final period of drilling program. The result suggests that actual basement depth is deeper than previous prediction applying time-depth functions from a neighbor well that was recently drilled.