f Images of rock properties estimated from a crosswell seismic velocity tomogram

Methods for obtaining an accurate image of the upper crust in terms of seismic velocities have evolved rapidly during the last decade, especially with well-to-well tomography techniques: well-to- well tomography allows us to constrain velocities more than with classical reftection seismology methods. At the same time, laboratory experiments have increased our knowledge of the influence of rock properties, such as porosity, saturation or clay content, on acoustic measurements. Our goal is to use results obtained in the laboratory for the interpretation in terms of porosity of an actual cross-well survey. Three different approaches are used: applying (1) geostatistical techniques, (2) rock physics relations obtained in the laboratory, and (3) a combination of geostatistics and rock physics.