AVO classification of lithology and pore fluids constrained by rock physics depth trends

Elastic properties of rocks are strongly influenced by local geological trends and can change markedly even within a sedimentary basin. Critical geologic factors that control elastic properties are either related to depositional environment or burial history. Knowledge about the expected change in seismic response, as a function of depositional or compactional trends, will increase the ability to predict hydrocarbons, especially in areas with little or no well log information. In other words, by understanding the geologic constraints in an area of exploration, one can reduce the range of expected variability in rock properties and hence reduce the uncertainties in seismic reservoir prediction. Figure 1 depicts this problem, where we assume there is well log control only in the shallow interval on the shelf edge. Before extending the exploration into more deeply buried zones, or to more distal deepwater environments, it is important to understand the rock physics trends in the area.