The Décollement Structures in Jiyang Depression, Bohai Bay Basin, China

AbstractThis paper uses seismic, drilling, and oil‐exploitation data to study the strata, structural deformation and the physical properties of rocks in the Jiyang Depression. The result shows the existence of décollement structures. The décollement structures occurred mainly along the unconformity surface between the Cambrian and Archean, and the disconformity surface between the Carboniferous and Ordovician. The décollement structure also developed within Paleozoic and Cenozoic. The décollement structure surface was a fault zone with cataclastic rocks and folds in the seismic profile. Near the décollement structure surface, at the bottom of the Cambrian and the top of the Archean, developed an interjacent fractured zone which shows high porosity and high permeability. The bottom of the Cambrian might be missing or overlapped, and the latter occurred in the seismic profile as double reflection time corresponding to décollement folds and stacking anticline. Because of the synchronisms of oil‐gas formation and décollement structure occurrence, the décollement structure afforded the effective storage space and channel to accumulation of oil‐gas, which were the key elements to the buried hill oil‐gas pool.