A moving fluid pulse in a fault zone

摘要

In the Gulf of Mexico, fault zones are linked with a complex and dynamic system of plumbing in the Earth's subsurface. Here we use time-lapse seismic-reflection imaging to reveal a pulse of fluid ascending rapidly inside one of these fault zones. Such intermittent fault 'burping' is likely to be an important factor in the migration of subsurface hydrocarbons. Faults have a dual function in that they can act as both an impediment to and, at times, a preferential pathway for fluid flow. Both types of behaviour are invoked in the petroleum industry to explain how hydrocarbons move from the location at which they are generated (for example, by flowing along faults) into fault-bounded reservoirs where they become trapped (for example, by a lack of flow across faults). Several lines of evidence from the South Eugene Island Block 330 field, offshore Louisiana, USA, indicate that faults cutting through sequences of Pliocene and Quaternary sands and shales have hosted significant vertical fluid flow over the past 250,000 years, continuing to the present day.