Sonar surveying of caverns and 3D modelling of entire cavern fields

Abstract

The echometric surveillance of caverns is especially important with regards to their safe and effective operation. As opposed to brine production caverns, storage caverns are generally subject only to convergence and they do not undergo large and irregular changes of shape under normal conditions. Echometric surveillance is therefore primarily employed to obtain proof of the cavern stability and convergence. Applying the state-of-the-art sonar technology it is possible during an echometric survey to measure and process the geometry of relevant parameters such as speed of sound, pressure and temperature with a single tool run. Today, specialized software allows us to present all the cavern field data in a common computer model, starting from the sonar survey results over the surface situation, and the well courses until the geology. In the first instance of the presentation the techniques used for surveying caverns as well as the survey procedure are described in general. Subsequently some interesting results of individual sonar surveys are presented. In the paper it is shown by means of a practical example what benefits cavern operators can derive from 3D-models of cavern field sites. Besides being useful for presentation purposes, such models can among other things help in the correlation of the survey results with the geology and support planning. Modeling is done with the CavWalk Professional software, which has been specially developed for the presentation of cavern fields. The software allows the user to undertake virtual excursions through the 3D-model at the surface as well as underground. In the spatial representation of one or several caverns the observer can move around outside and inside the caverns.