Quantitative Seismic Interpretation

Every year finding new oil is harder, riskier, and more expensive - a natural consequence of its finiteness. As dictated by M. King Hubbert’s “peak,” declines in discoveries and production are inevitable. Yet demand continues, forcing us to deeper water, more complex reservoirs, and smaller, more subtle oil fields. A key to managing this complexity and risk has always been effective integration of the diverse petroleum technologies. Workstations, visualization software, and geostatistics have contributed to integrating the vast amounts of data that we sometimes drown in. Perhaps more important are the asset teams that exploit diverse data by integrating expertise. Our goal, in preparing Quantitative Seismic Interpretation, is to help illustrate the powerful role that rock physics can play in integrating both the data and expertise of geophysics and geology for reservoir characterization. Our objective for this book is to help make the links between seismic and reservoir properties more quantitative. Most of our examples use amplitude signatures and impedances, but we consider quantitative seismic interpretation to include the use of any seismic attributes for which there are specific models relating them to the rock properties. Our approach is to introduce fundamental rock physics relations, which help to quantify the geophysical signatures of rock and fluid properties. Since rock properties are a consequence of geologic processes, we begin to quantify the seismic signatures of various geologic trends. We also fully embrace probabilistic and geostatistical tools, as quantitative means for managing the inevitable uncertainty that accompanies all quantitative methods. Quantifying, managing, and understanding the uncertainties are critical for survival in a risky environment. For many years, rock physics focused on physics. We carefully measured wave propagation under a variety of laboratory conditions, and we developed marvelously clever acoustic analogs of rocks, finding ways to model grains and pores, and the fluids that sit inside them. We know how to parameterize seismic velocities in terms of mineralogy, porosity, aspect ratios, and grain contacts. We understand how pore pressure and stress affect velocity, attenuation, and their anisotropies. We have a sense for why (high-frequency) laboratory velocities differ from (low-frequency) field velocities. And we can make excellent predictions of how velocities change when pore fluids change.