Abstract The experiment: In this case history, the French gas supply company Gaz de France planned to store gas by injection into a water-bearing sandstone reservoir in a faulted anticlinal structure at a depth of about 900m in the Paris Basin. It consists of a combination of sandstone channels of excellent reservoir quality with an average thickness of 20m. An R2 reservoir exists below Rl and is made up of complex communicating channels. Two tops were identified, and wells CE12 and CE112 were drilled for the first gas injections. Such fluid substitution induces a significant change in Vp and density, which suggests that the gas bubble could be detected with seismic data.

Abstract When looking at the road ahead, it is interesting to take a moment to look at the road behind to provide some perspective. In particular, can we learn anything from the road ahead, as envisioned in the 1992 SEG publication Reservoir Geophysics, compared with the road we find ourselves on in 2010?

ABSTRACT This contribution attempts to recount our collective progress in understanding the Archean–Hadean Earth system over the past 50 yr. Many realms of the geological sciences (geochemistry, petrology, geophysics, structural geology, geobiology, planetary science, and more) have made substantive contributions to this effort. These contributions have changed our understanding of the Archean–Hadean Earth in five major areas: (1) the expanse of Archean–Hadean time; (2) tectonics and lithospheric evolution, particularly possible analogs for the sites of modern, primary crust production and mantle differentiation (e.g., magmatic arcs, ocean ridges, and large igneous provinces); (3) evolution of the atmosphere-hydrosphere system, and its impact on the evolution of Earth’s endogenic and exogenic systems; (4) the history of liquid water, particularly at the ocean scale; and (5) the origin and development of the biosphere and its impact on the geologic record. We also emphasize that much of the progress made in understanding the evolution of early Earth systems over the past 50 yr has been fueled by important technological advances in analytical geochemistry, such as the advent of ion probes for U-Pb zircon geochronology, inductively coupled plasma–mass spectrometry for trace-element and Hf isotopic analyses, Raman spectroscopy in organic geochemistry, and molecular reconstructions in biology. Within this context, we specifically review progress in our understanding of the Eoarchean history of southern West Greenland as an example of the value of continuous integration of careful geologic observation and mapping with evolving technology, which have combined to further open this window into Earth’s earliest systems.