Estimating the distribution of salt cavern squeeze using subsidence measurements

摘要

We report a field study on solution mining of magnesium chloride from bischofite layers in the Netherlands at depths between 1500 and 1850 m. Subsidence that was observed in the area is due to part of the brine production being realized by cavern squeeze; some of which were connected. We used an earlier developed inversion scheme to quantify the distribution of the squeeze volumes from the subsidence measurements. We incorporated in it the creep behavior of the rock salt as a convolution between the time-dependent response of a squeeze event and the actual production history. With a Maxwell viscoelastic behavior in the salt with realistic time constant, we achieved a good result for the subsidence values and for the observed ratio between subsidence bowl volume and squeeze volume. With the new understanding we created physics-based forecasts for different production scenarios and provided an estimate for the remaining time and the producible volumes before the maximum allowed amount of subsidence is reached. After completely stopping production, our model predicted a rebound of the subsidence.