Gas hydrate and free gas petroleum system in 3D seismic data, offshore Angola.

摘要

Evidence of gas hydrate and free gas occurrences in a 3-D seismic volume from the West-Central Coastal Province of the Congo Fan, offshore Angola illustrates all the components of a complete petroleum system. The source is organic-rich muds associated with late Cretaceous to early Tertiary channels, the migration paths are along growth faults, and the traps are partly defined by the gas hydrate stability zone (for the gas hydrate), partly by the bottom-simulating reflector (for the sub-hydrate free gas), and partly by faults (for both). The spatial distribution of free gas is further supported by the associated seismic bright spots, and also by the attenuation of high frequencies of p-waves that traverse the gas saturated zone. Gas chimneys through the hydrate stability zone attest to non-equilibrium conditions produced by salt tectonics and faulting.