For offshore HPHT exploration wells in the South China Sea, an operator typically relies heavily on surface seismic data for structural depth information. Yet predrill subsurface models exhibit significant uncertainty in formation properties and depth accuracy, which is problematic where lithology and bed thickness are unpredictable. A previous exploration well suffered severe well control problems on penetrating a high-pressure formation. To continue field development, the operator needed to look ahead of the bit to stop above the high-pressure zone, which was characterized by the shale marker above it.