Abstract:

Because of the creep characteristics of salt rock, underground gas storage in salt rock will produce larger shrinkage deformation and affect its safe and stable operation. There is no unified national standard for analysis methods and evaluation criteria for gas storage cavity stability currently. The numerical simulation is mainly adopted to evaluate gas storage cavity stability in China. Based on numerical simulation on shrinkage deformation of underground gas storage in Jintan salt mine and using foreign evaluation criteria for underground gas storage stability in salt for reference, volume convergence failure risk evaluation matrix of underground gas storage in salt rock has been established. And the analysis and displaying performance function of volume convergence failure probability of gas storage has been established with first-order second-moment method. The results indicated that failure probability of volume convergence decreases with increasing of internal pressure under long-term constant internal pressure, while it increases with decrease of internal pressure under peak shaving short-term lower internal pressure and the minimum internal pressure should be kept at more than 4.2 MPa. By large scale three-dimensional geomechanical model test on underground gas storage in bedded salt rock under condition of alternating gas pressure, volume convergence deformation of gas storage decreases with increasing of internal pressure and the minimum internal pressure during short-term operation should be greater than 4.0 MPa. The results of model test and failure probability analysis are more similar. So, the minimum internal pressure in peak shaving shortterm should be over 4.0 MPa in order to avoid volume convergence failure for underground gas storage in salt rock.

Key words: underground gas storage in salt rock, failure of volume convergence, analysis of probability, model test, Jintan of Jiangsu