Hydrocarbons in rock salt of the Gorleben salt dome—amount, distribution, origin, and influence on geomechanical properties

2015 ◽  
pp. 81-88
Geophysics ◽  
1976 ◽  
Vol 41 (1) ◽  
pp. 123-132 ◽  
Author(s):  
Robert D. Stewart ◽  
Robert R. Unterberger

A VHF radar has been used in a salt mine in the Cote Blanche Salt Dome to probe horizontally for the dome flank and vertically for the top of the salt. Discontinuities in the salt's complex electric permitivity caused by anhydrite stringers, shale, sandstone, water, or fractures will caused radar reflections, A narrow beam, ±9 degrees in salt, helps to determine the direction to the discontinuity. The time of the radar reflection determines the range to the discontinuity. The maximum,one‐way penetration was 2040 ft. The radar speed in Cote Blanche salt was measured by timing radar reflections through known distances of salt. The measured radar speed was 188ft/μsec slightly less than the radar speed in pure salt (203 ft/μsec. ). A shear zone in the salt was found to have many discontinuities or radar targets. A discontinuity was detected in a discontinuity about 400 ft above the mine level, but still inside the salt, was also found. The top of the salt dome was detected from several locations in the mine.


2017 ◽  
Vol 62 (3) ◽  
pp. 565-577
Author(s):  
Marek Cała ◽  
Antoni Tajduś ◽  
Wacław Andrusikiewicz ◽  
Michał Kowalski ◽  
Malwina Kolano ◽  
...  

AbstractLocated in central Poland, the Kłodawa salt dome is 26 km long and about 2 km wide. Exploitation of the dome started in 1956, currently rock salt extraction is carried out in 7 mining fields and the 12 mining levels at the depth from 322 to 625 meters below sea level (m.b.s.l.). It is planned to maintain the mining activity till 2052 and extend rock salt extraction to deeper levels. The dome is characterised by complex geological structure resulted from halokinetic and tectonic processes.Projection of the 3D numerical analysis took into account the following factors: mine working distribution within the Kłodawa mine (about 1000 rooms, 350 km of galleries), complex geological structure of the salt dome, complicated structure and geometry of mine workings and distinction in rocks mechanical properties e.g. rock salt and anhydrite. Analysis of past mine workings deformation and prediction of future rock mass behaviour was divided into four stages: building of the 3D model (state of mine workings in year 2014), model extension of the future mine workings planned for extraction in years 2015-2052, the 3D model calibration and stability analysis of all mine workings.The 3D numerical model of Kłodawa salt mine included extracted and planned mine workings in 7 mining fields and 14 mining levels (about 2000 mine workings). The dimensions of the model were 4200 m × 4700 m × 1200 m what was simulated by 33 million elements. The 3D model was calibrated on the grounds of convergence measurements and laboratory tests. Stability assessment of mine workings was based on analysis of the strength/stress ratio and vertical stress. The strength/stress ratio analysis enabled to indicate endangered area in mine workings and can be defined as the factor of safety. Mine workings in state close to collapse are indicated by the strength/stress ratio equals 1. Analysis of the vertical stress in mine workings produced the estimation of current state of stress in comparison to initial (pre-mining) conditions.The long-term deformation analysis of the Kłodawa salt mine for year 2014 revealed that stability conditions were fulfilled. Local disturbances indicated in the numerical analysis were connected with high chambers included in the mining field no 1 and complex geological structure in the vicinity of mine workings located in the mining fields no 2 and 3. Moreover, numerical simulations that projected the future extraction progress (till year 2052) showed positive performance. Local weakness zones in the mining field no 7 are associated with occurrence of carnallite layers and intensive mining which are planned in the mining field no 6 at the end of rock salt extraction.


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