New Developments in Gravity Applications and Instruments

Gravity meters are commonly used to map spatial changes in the earth's gravity. The application of gravity surveys to monitor change and recent improvements in gravity instrumentation will be summarized. The use of gravity to track the progress of a waterflood in Prudhoe Bay, Alaska, provides a 4D Gravity case history. Monitoring injected products using surface gravity measurements provides an effective "early warning system" for injection and sequestration projects. A borehole gravity survey in Hanford, Washington, demonstrates the ability to measure bulk densities using a borehole gravimeter. The applications include geotechnical studies, locating and monitoring thief zones in reservoirs, mineral exploration and grade control in mines. Long period movements of the earth can be recorded by gravity meters. The ground shaking in Luxembourg before and after an earthquake in Japan was recorded on a seismometer, a superconducting gravity meter and a gPhone gravity meter. The portable gPhone gravity meter provides the means to record earth movements along active faults using small earthquakes for signal sources. Airborne gravity systems have improved with better platform control, timing and GPS. Airborne gravity data acquired in the transition zones provide information for geoid mapping.