Imaging of phase changes and fluid movement in and between reservoirs at Teal South

Abstract

We have reexamined the poststack seismic legacy and time-lapse data sets from the Teal South field in the Gulf of Mexico for insight into regional pressure changes from production at one reservoir and its effects on neighboring unproduced reservoirs. We support previous predictions of oil and gas leakage from neighboring reservoirs by providing direct evidence for leakage through 3D mapping of the hydrocarbons themselves. The use of the squared instantaneous amplitude as an attribute allowed visualization of the large amplitude changes while minimizing the appearance of noise. The use of translucency in the 3D time-lapse difference volumes assisted in identifying features of interest that had been unrecognized in earlier studies. For example, this investigation found that hydrocarbons appeared to have escaped from one small (unproduced) reservoir through its spill point, only to be trapped in a nearby structure, from which it ultimately escaped through that trap’s spill point. Such fluid migration can occur in a period of a few years due to production, not geologic time. Time-lapse studies such as the one presented here can be very helpful in identifying such fluid movement, particularly in highly porous and unconsolidated reservoirs that are highly sensitive to pore-fluid type and stress changes.