Geological analysis reveals spatially distinct overpressure mechanisms across structural units in the Xihu Sag, highlighting critical targets for safer deep hydrocarbon drilling design.
Key Points
To systematically investigate the genetic mechanisms, vertical pressure zoning, and spatial heterogeneity of abnormal formation pore pressure across multiple structural units in the Xihu Sag.
Integrated wireline logging data with direct pore pressure measurements from nine exploration wells across three structural units: the Western Slope Belt, Western Sub-sag, and Central Inversion Belt.
Applied Bowers' effective stress diagnostic analysis combined with sonic velocity-density cross-plots to differentiate loading mechanisms from unloading mechanisms.
Identified distinct vertical pore pressure zoning comprising normal-pressure, overpressure, and pressure reversal zones with marked lateral structural heterogeneity.
Determined that Western Slope Belt overpressures arise from initial undercompaction combined with hydrocarbon generation fluid expansion, whereas Central Inversion Belt and Western Sub-sag overpressures are driven by fault-assisted hydrocarbon charging and tectonic compression.