SURDAM, RONALD C., NICHOLAS G.K. BOYD III, and ZUN SHENG JIAO
Institute for Energy Research, University of Wyoming, Laramie, WY

Abstract: A New Exploration Strategy for Unconventional Basin Center Hydrocarbon Accumulations

Application of conventional exploration techniques in the search for basin-center hydrocarbon accumulations can be disappointing and costly. Integration of velocity data into the exploration paradigm significantly reduces uncertainty and increases profitability. A study to illustrate the importance of this integration was made in the western Wind River Basin.

The data base covers 500 square miles and includes 58 wells with sonic logs, 20 2-D seismic lines (160 line miles), and two 3-D seismic surveys (60 square miles). A velocity inversion, observed at consistent depths and traveltimes on both sonic logs and seismic velocity data, typically characterizes the onset of anomalous pressure and the presence of a free gas phase in the pore fluid. Velocities that deviate significantly below the regional velocity-depth gradient are considered anomalously slow.

To aid in the interpretation of the petroleum system of a basin, the stratigraphic section characterized by anomalously slow velocities (i.e., gas saturation) can be isolated. The relationship between the isolated velocity anomalies and hydrocarbon accumulations can be delineated neatly in both 2- and 3-dimensional visualizations. In the western Wind River Basin the five major hydrocarbon accumulations in the study area are associated with prominent velocity anomalies. Identification and integration of velocity anomalies with other geological/geophysical observations results in new leads in the search for basin-center hydrocarbons.

ACKNOWLEDGMENTS

This study was funded by the Gas Research Institute under Contract Number 5096-260-3833, the Department of Energy under Contract Number DE-PN2697FT34181, Tom Brown, Inc., and Snyder Oil Corporation.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas