Numerical Simulation of the Underground Storage Cavern Using FDEM

Abstract

ABSTRACT Underground storage cavern has been increasingly exploited as it has many advantages such as reducing investment, economizing land use and improving safety compared with storage above the ground surface. We employ the hydromechanical coupled FDEM to simulate the excavation and operation phases of the underground storage cavern with a water curtain system (WCS), taking into consideration the natural discrete fracture network (DFN). The simulation results captured the propagation and slipping of the pre-existing DFN during the excavation and operation process. We quantitatively evaluate the containment performance based on the water inflow and pore pressure distribution. This study provides new insights into evaluating the stability of cavern-surrounding rock masses and containment performance of underground storage caverns. INTRODUCTION Underground storage caverns have better performance on safety, security, economy, and greater environmental acceptance compared with traditional storage infrastructures such as storage tanks and pipelines. Several large underground storage caverns have been constructed, for example, Jurong rock caverns in Singapore (Zhou & Zhao, 2016) and Huangdao underground oil storage caverns in China (Wang et al., 2015). Underground storage caverns are constructed in fractured rock masses, confining the storage medium (such as oil and gas) by maintaining groundwater pressure around caverns which is also called hydraulic confinement (Aberg, 1978; Froise, 1987; Lindblom, 1997). The basic principle of underground containment the cavern is that no gas could leak as long as the water pressure increases along all possible gas leakage paths away from the cavern (Goodall et al., 1988). To enhance the sealing performance, water curtain systems (WCS) are constructed to manually control the pore pressure distribution by regulating the water curtain pressure. (Shi et al., 2018). Previous studies has evaluated the stability of excavated rock masses (Mohanty & Vandergrift, 2012; Ma et al., 2016; Zhuang et al., 2017) and containment performance (Xu et al., 2018; Liu et al., 2021) by using in-situ monitoring methods and numerical simulation. However, the fracture propagation and slip induced by the excavation and operation of the storage cavern, as well as the resultant fluid pressure variation, have not been illustrated.