Abstract

Dripping Rock Field is located in T14N, R94W, Sweetwater County, Wyoming on the eastern flank of the Washakie Basin. Production is from stratigraphically trapped marine bar sandstones of the Cretaceous upper Almond Formation. Similar productive intervals are found on the Rock Springs Uplift and the Wamsutter Arch to the north and northwest.

Amplitude versus offset seismic techniques have proved useful in the detection of numerous Wyoming reservoirs previously held to be seismically invisible. This technology relies on reflectivity variations for different source and receiver offsets which result from Poisson's ratio contrasts between differing lithologies.

Based on encouragement of amplitude versus offset forward models, two long offset seismic lines were acquired across Dripping Rock Field in T14N, R94W, Sweetwater Co., Wyoming during the late summer of 1988. The seismic offset signature of the data was found to be in good agreement with the amplitude versus offset models in both reservoir and non-reservoir cases. Distinct amplitude versus offset signatures were confirmed for the upper Almond marine bar facies, laterally adjacent trap facies, and the non-productive delta margin / marginal marine facies. This allows differentiation of the facies and delineation of much thinner productive marine bar sandstones than is possible with normal seismic techniques.

The seismic data has also provided evidence of a striking paleo-structural feature which may have played a role in the localization of the productive sandstones.