Abstract: An improved method for assessing the geologic risk for hydrocarbon presence and hydrocarbon accumulation size is disclosed. In one configuration, seismic attributes are assigned to a horizontal axis and data quality to a vertical axis to form a matrix crossplot. Direct Hydrocarbon Indicators (DHI) derived from seismic data are used to qualify the presence and accumulation size. A quantitative method for scaling and calibrating the DHI matrix is illustrated that can be applied to existing petroleum basins and by analog to frontier areas.

Abstract: An improved method for assessing the geologic risk for hydrocarbon presence and hydrocarbon accumulation size is disclosed. In one configuration, seismic attributes are assigned to a horizontal axis and data quality to a vertical axis to form a matrix cross-plot. Direct Hydrocarbon Indicators (DHI) derived from seismic data are used to qualify the presence and accumulation size. A quantitative method for scaling and calibrating the DHI matrix is illustrated that can be applied to existing petroleum basins and by analog to frontier areas.

Abstract: An improved method for modeling the velocity of seismic energy in subterranean rock layers is described. The velocity is assumed to vary such that the gradient of the velocity, that is, the direction of maximum change in the velocity, is at all times perpendicular to the interfaces between the rock layers. Improved methods of generating a representation of a subterranean structure of the earth are also disclosed.

Abstract: An improved method for modeling the subterranean structure of the earth is disclosed. Assumed velocities are used in initially modeling the path of seismic energy through the subterranean structure. Arrays of travel times corresponding to upward and downward going energy from various locations in the subterranean structure are calculated using ray tracing techniques. Actual reflection points are located when the sum of the upward and downward going travel times calculated with respect to a particular point in the structure equals the actual travel times recorded. The velocity assumptions are verified by selecting common reflection point records and adjusting the assumed velocities, such that reflection events on displayed traces from the common reflection point are horizontal. A least squares fit is used to correct the common reflection point event data until it is optimally flat.