System for non-invasive controlling of underground storages and method for detecting leakages in underground storages

Abstract

A device and a method is disclosed for detecting an undesired escape of fluids, in that electric potentials are measured using a grid of non-polarizable measuring electrodes above an underground storage facility. Potential differences are determined in such a way that disturbances due to injection borehole or due to the exchange of fluids in the underground storage facility are eliminated. This is done either through the use of the symmetry of the potential distribution around the injection borehole in that the potential differences of pairs of measuring electrodes are observed whose mid-points coincide with the injection borehole or else through the computational simulation of the potentials that arise due to the fluid movement in the underground storage facility without a leak. These are then subtracted from the measured potentials. If the ascertained potential differences exceed a limit value, this is considered as an indication of a leak.

1 . A method for detecting underground fluid flows, whereby a fluid can be fed into an underground storage facility through an injection borehole, and potential values are picked up by non-polarizable measuring electrodes, whereby the method comprises at least one of the following steps:
 the symmetry of the potential distribution around the injection borehole is used in order to form potential differences between the measured values of non-polarizable measuring electrodes that are arranged symmetrically to the injection borehole, and/or   a potential difference is determined between a measured potential and an anticipated potential without a leak or disturbance, at each measuring point of the non-polarizable measuring electrodes.   
     
     
         2 . The method according to  claim 1 ,
 characterized in that   in the case of an isotropic structure of the underground storage facility, the potential difference between the measuring electrodes is determined, their mid-point coincides with the injection borehole, whereby the potential values are preferably picked up at the two measuring electrodes at the same time.   
     
     
         3 . The method according to  claim 2 ,
 characterized in that   if a prescribed potential difference limit value is exceeded, an interference is recognized that is present at the measuring point of the first measuring electrode or at the measuring point of the second measuring electrode, as a function of the sign of the measured potential difference.   
     
     
         4 . The method according to  claim 1 ,
 characterized in that   if the underground storage facility has a heterogeneous permeability or geometry, a potential reference value for the difference formation is based on a computational simulation of the fluid flow in the underground storage facility without disturbances, especially without a leak.   
     
     
         5 . The method according to  claim 4 ,
 characterized in that   if a predetermined potential difference limit value is exceeded, an interference pertaining to the measuring point of the measuring electrode is recognized.   
     
     
         6 . The method according to one of the preceding claims  claim 1 ,
 characterized in that   a plurality of measuring electrodes that can be used as first and second measuring electrodes is arranged on the earth's surface and/or in exploratory boreholes so as to cover the area of the underground storage facility.   
     
     
         7 . The method according to  claim 6 ,
 characterized in that   the measuring electrodes are arranged at a distance of not more than 100 m from each other.   
     
     
         8 . A device for carrying out a method according to  claim 1 , involving an underground storage facility and an injection borehole leading to the underground storage facility, whereby measuring electrodes are arranged symmetrically around the injection borehole leading to the underground storage facility. 
     
     
         9 . The device according to  claim 8 ,
 characterized in that   measuring electrodes are arranged so as to cover the area of the underground storage facility, whereby the device comprises a module for determining the potential differences at the individual measuring points of the measuring electrodes.   
     
     
         10 . The device according to  claim 9 ,
 characterized in that   the device has a simulation module for computing a potential reference value for purposes of the difference formation, taking into account the momentary inflow of fluid, the geometry and the physical properties of the underground storage facility, especially the permeability, the porosity, the specific electric conductivity and the coupling coefficient.   
     
     
         11 . The device according to  claim 8 ,
 characterized in that   a plurality of measuring electrodes is arranged on the earth's surface and/or in exploratory boreholes so as to cover the area of the underground storage facility.   
     
     
         12 . The device according to  claim 11 ,
 characterized in that   the measuring electrodes are arranged at a distance of no more than 100 m from each other.