Characterization of compartmented reservoirs deposited in a fluvial environment

We conducted a study at Stratton Field, a large gas-producing property in Kleberg and Nueces Counties in south Texas, to determine how to best integrate geophysics, geology, and reservoir engineering technologies to detect thin-bed compartmented reservoirs in a fluvially deposited reservoir system. This study documents that narrow, meandering, channel-fill reservoirs less than 20 ft (6 m) thick and as narrow as 200 ft (61 m) can be detected with 3-D seismic imaging at depths exceeding 6000 ft (1800 m) if the 3-D seismic data are carefully calibrated to subsurface stratigraphy using vertical seismic profile (VSP) control. Even though the 3-D seismic images show considerable stratigraphic detail in the interwell spaces and indicate where numerous thin-bed compartment boundaries could exist, the seismic images cannot by themselves specify which stratigraphic features are the flow barriers that create the reservoir compartmentalization. However, when well production histories, reservoir pressure histories, and pressure interference tests are incorporated into the 3-D seismic interpretation, a compartmentalized model of the reservoir system can be constructed that allows improved development drilling and reservoir management to be implemented. This study illustrates how realistic, thin-bed, compartmented reservoir models result when geologists, engineers, and geophysicists work together to develop a unified model of a stratigraphically complex reservoir system.