Pore Structure Evolution in Sandstone of Underground Gas Storage during Cyclic Injection and Production Based on Nuclear Magnetic Resonance Technology

The underground gas storage (UGS) in depleted sandstone reservoirs forms the largest proportion of UGS market China. Multiple cycles natural injection and production cause rapid increase drawdown pore pressure, which may induce damage to rock skeleton structure, complex fluid flow paths reservoir. In this paper, transverse relaxation time (T2), nuclear magnetism resonance imaging, high-pressure mercury intrusion analysis are combined evaluate variation structure medium-grained sandstone. results show that cyclic leads a slight total volume, indicating weak rocks occurs. T2 spectrum at low pressure (10 MPa) high (25 both shrinkage medium-size pores occurs after multiple production. volume large-size was not highly correlated with number cycles. With ratio under increased cycles, while it fluctuated strongly pressure.