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Exploration & Production

Locating Geopressured Hydrocarbon Reservoirs

The overall goal of this research was to develop, test, and validate an integrated conceptual model for the formation of pressure seals and the associated accumulation of hydrocarbons near the seal. The conceptual model developed in previous years is a relative permeability/capillary pressure seal. This model accounts for the formation of pressure seals, and explains the occurrence of hydrocarbon accumulation within the seal. Studies currently underway include analyses of the geomechanics of the pressure seals and geophysical modeling of seismic velocity anomalies.

We have developed a method that identifies the onset of pressure transition zones (pressure seals) for either ahead of bit observation or surface seismic survey use. The method developed utilizes the combination of different frequency decay rules for sharp and gradational acoustic contacts to reconstruct the frequency envelope present within a seismic data set. Through our research on pressure seals, we have identified a specific relationship between sound frequency, sound wavelength, pressure transition zone thickness, and the differential weakening of seismic reflections across these acoustic gradients. The specific relationship allows the detection of the presence, thickness, and pressure differential across pressure seals from either surface or downhole seismic surveys. Synthetic seismic modeling indicates that geopressure transition zones will be especially apparent when viewed with Amplitude Variation with Frequency displays.

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Department of energy

DOE Office of Nuclear Energy
DOE-Idaho Office