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3D and 4D high resolution microgravity – case stories from mining and geoengineering
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 72nd EAGE Conference and Exhibition - Workshops and Fieldtrips, Jun 2010, cp-162-00020
- ISBN: 978-90-73781-87-0
Abstract
Gravimetry has a long tradition in various geological investigations. For regional exploration projects the accuracy of 0.2 – 0.5 mGal was sufficient for decades. Detailed surveys, on the other hand, and especially microgravity require not only high resolution of gravimeter’s readings, but also high accuracy/repeatibility in the range of 0.00X mGal (X μGal). Therefore, we also focused on the reduction of disturbing effects affecting microgravity measurements (wind, sun, rain, vibrations, etc.), but mainly on data processing. We developed special software for accurate determination of gravimeter system drift from field observations. This technique allows significant reduction of repeatibility error. As the presented case stories represent about three decades, the resolution of gravimeters in contrast to expected and observed signals will be discussed. Case histories will be presented on the detection of voids that often exist in mines as result of natural processes, or unknown historical mining. This will include the monitoring of surface collapse risk. Another example of microgravity monitoring of stress evolution in a deep coal mine will be shown. As well the monitoring of groundwater variations in an open pit mine waste dump body will demonstrate the efficiency of repeated microgravity in hazard control. Microgravity indicated critical increase of groundwater before a damaging slide of the waste dump body mass. Special case is represented by 4D gravity in oil EOR. The results suggest that applied high resolution microgravity may contribute, beside others, to mine monitoring systems aimed at risk mitigation.