Abstract
Small-spacing twin-well (SSTW) salt caverns have an extensive application prospect in thin or bedded rock salt formations due to their good performance, while they are rarely used in ultra-deep formations. The target strata depth of Pingdingshan salt mine is over 1700 m, and it is planned to apply an SSTW cavern to construct the underground gas storage (UGS). A 3D geomechanical model considering the viscoelastic plasticity of the rock mass is introduced into Flac3D to numerically study the influence of internal gas pressure, cavern upper shape and well spacing on the stability of an SSTW salt cavern for Pingdingshan UGS. A set of assessment indices is summarized for the stability of gas storage. The results show that the minimum internal gas pressure is no less than 14 MPa, and the cavern should not be operated under constant low gas pressure for a long time. The cavern with an upper height of 70 m is recommended for Pingdingshan gas storage based on the safety evaluation and maximum volume. The well spacing has a limited influence on the stability of the salt cavern in view of the volume shrinkage and safety factor. Among the values of 10 m, 20 m and 30 m, the well spacing of 20 m is recommended for Pingdingshan gas storage. In addition, when the cavern groups are constructed, the pillar width on the short axis should be larger than that on the long axis due to its greater deformation in this direction. This study provides a design reference for the construction of salt cavern gas storage in ultra-deep formations with the technology of SSTW.
Highlights
Underground storage is more and more prevalent in energy storage with its many advantages such as large storage capacity, strong mobility, long service life and higher safety than ground facilities [1,2,3,4]
MPa is suitable for Pingdingshan salt cavern based on the volumeand shrinkage and suitable for Pingdingshan salt cavern on the volume shrinkage roof subsid‐
Based on the geomechanical features of Pingdingshan salt mine, a 3D visco-elastic-plastic model was established to investigate the influence of the minimum internal gas pressure, cavern upper shape and well spacing on the safety of Small-spacing twin-well (SSTW) salt cavern gas storage
Summary
Underground storage is more and more prevalent in energy storage with its many advantages such as large storage capacity, strong mobility, long service life and higher safety than ground facilities [1,2,3,4]. There are more than 630 underground storages in the world, distributed in 35 countries [8]. With the development of the economy and the promotion of environmental protection awareness, more and more attention is being paid to clean energy exploitation and utilization by many countries around the world [9]. As one of the cleanest energies, is taking an increasing proportion of energy usage after entering the 21st century. It can be used in daily activities for different purposes such as heating, cooking and producing electricity. In the last century, the Chinese government began to work on the construction of underground gas storage [12]
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