Integrated Seismic Geomorphology as a Tool to Unravel Fluid Expulsion Episodes Expressed in the Sedimentary Record in a Mature Petroleum Basin (Danish Central Graben, North Sea)

Seismic geomorphology is a tool to reconstruct sedimentary processes that have shaped landscapes or seascapes that are now buried in the sedimentary record. Revealing the spatial distribution of these processes can provide a welcome geological framework to subsequent data integration, such as well derived data or basin modeling data. We demonstrate the usage of such integrated seismic geomorphological methodology in a mature petroleum basin, and reveal the interlinkage of source rock maturity, fluid migration pathways, and the expression of expulsion in the sedimentary record. Large amounts of giant pockmarks occur within Cretaceous strata, which predate thermal maturity of the main prolific source rock (in Late Miocene). Integration with basin modeling data suggests, for the first time, that deeper source rocks and/or biogenic degradation of the main source rock created the observed features. In addition, integration of seismic and well data shows that km-scale seep carbonates occur within the main seal, which suggests that partial leaking of methane sustained large colonies of sulfate-reducing bacteria. Summarizing, the methodology allows for subsurface data integration in a three-dimensional space, and is here applied to identify expulsion related sedimentary processes that shaped the seafloor, which provides important applications for exploration of hydrocarbons in a mature basin.