Objective Gas storage using lined rock caverns (LRC) has emerged as an innovative method for underground gas storage. Naturally constructed within caverns manually excavated in underground rock formations, LRC gas storage exhibits several characteristics, including versatile applications, large storage capacities, and high safety levels. These unique advantages position LRC gas storage as an effective solution to challenges faced in modern energy security and storage.
Methods LRC gas storage is situated within complex underground rock formations at significantly varying burial depths, where the distribution of rock strata is heterogeneous. This study developed a numerical model for medium- to high-pressure gas storage in such heterogeneous rock formations, based on an existing underground gas storage facility. Special attention was paid to the geological conditions of this facility, and typical surrounding rock types (Classes I, II, III, and IV) were selected for modeling. The model accounts for scenarios with both soft upper and hard lower strata, as well as hard upper and soft lower strata, incorporating varying boundary levels between rock layers. Utilizing this model, analyses were conducted to investigate the stress and deformation characteristics of LRC gas storage under elevated internal pressure.
Results These analyses focused on the stress states affecting the steel lining, rebars, concrete lining, and surrounding rock of the gas storage under varying stratum conditions. The results indicated that, under typical stratum conditions, the stress on the steel lining remains below its failure strength, with tensile stress being the predominant factor. Additionally, the stress and deformation in gas storage situated within Class IV surrounding rock are significant, highlighting the need for special attention. In contrast, gas storage surrounded by Classes I, II, and III maintains healthy stress states, with rock deformation and plastic zones primarily developing in the weaker layers of the surrounding rock.
Conclusion In general, the steel lining and rebars used in gas storage within heterogeneous rock formations rarely approach their failure strength, contributing to overall stability. However, given that lining is susceptible to tensile failure, special attention is required to address potential cracking. Gas storage demonstrates greater stability when situated in formations with hard upper and soft lower strata. In cases where gas storage is located within Class IV surrounding rock, the steel lining may experience stress that approaches its yield strength and is subject to significant deformation in the surrounding rock. Conversely, gas storage in the surrounding rock of Classes II and III exhibits improved stability, with more attention required for the weaker layers. Deformation in gas storage is significant within these weak layers, with deformation amplitudes increasing as the surrounding rock deteriorates. Additionally, the surrounding rock exhibits a linear decrease in the maximum plastic strain as the boundary level between rock layers rises.
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