ABSTRACT:

Modeling and analysis of underground structures remain an important topic in rock mechanics. The majority of underground structures have originally regular geometry. However, in case of application of solution mining, underground openings having irregular geometries are created. Solution of stress state and corresponding deformations of such openings is almost impossible, hence, it is viable to apply numerical methods. Unfortunately, no comprehensive numerical modeling of an underground cavern with irregular geometry has been found, to the authors knowledge, in the literature. This paper presents a part of ongoing research on numerical modeling of stages of solution mining during formation of a cavern, application of different levels of inner pressure depending on LNG amount in the cavern and creep behavior of the cavern during its lifetime by considering loading and unloading cycles. Numerical model of a hypothetical underground LNG storage cavern having an irregular geometry and application of inside pressure have been achieved by using FLAC3D.

1 INTRODUCTION

Natural gas has gained importance as an energy source in recent years. Storage of liquefied natural gas (LNG) in underground caverns opened in mainly salt domes has become a usual practice because of several reasons such as low environmental impact, high degree of flexibility and withstanding of a pressure of over 50 MPa. The other advantages of underground storage are the small amount of land required, and security against external influences. The obvious purpose of a storage is to balance the supply of natural gas with the variations in consumption within an area, like seasonal fluctuations, short term adjustment (weekly and daily), and peak winter demand. There are also other purposes that storage can fulfill like, e.g., strategic role with security of delivery and possibilities to buy and sell gas (Glamheden & Curtis, 2006).

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