Do the Seismic Velocities Depend from Time-Temperature Index?

Tanima Dutta¹, Tapan Mukerji¹, Gary Mavko¹, and Kenneth Peters^2
1Stanford University, Stanford, CA
²USGS, Menlo Park, CA

The objective of our study is to test whether seismic velocities of rock depend on time and temperature index (TTI). This study is motivated by the observations that overpressure and reservoir qualities depend on temperature and time in many sedimentary basins. TTI, an important thermal maturity indicator, is directly linked with oil and gas generation, and combines the effects of temperature and time. However, there is no existing model (theoretical, empirical, and numerical) to predict TTI from observed seismic velocities. Our study identifies an empirical-numerical relation between TTI and seismic velocities. In order to obtain this relation, we perform petroleum system modeling at a well location. The well is located in deep-water petroleum system at Rio Muni Basin, West Africa. The essential petroleum system elements and TOC are identified based on petrophysical and rock-physics analysis. The TTI obtained from finite-element modeling of petroleum system are then compared with velocities measured at the same well location. We find that both Vp and Vs increase exponentially with TTI. The results can be applied to predict TTI, and thereby thermal maturity, from observed seismic velocities.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas