Piezomagnetic fields generated by the gas injection process in Hutubi ultralarge underground gas storage system (China)

Abstract

SUMMARY The fundamental behaviours of rock magnetism (piezomagnetic characteristics) at the field scale have not been confirmed because conventional experiments can be performed only in the laboratory. Here, the periodic extraction and injection of gas in the Hutubi ultralarge underground gas storage (UGS) system are used to simulate the stress loading and unloading processes at the field scale. We treat 26 gas wells in the UGS system as a multipoint-source Mogi model and calculate models of the piezomagnetic field generated during the operation of the UGS system. These models show that the local magnetic field (LMF) in the southern and central areas of the UGS system showed positive changes. In contrast, the northern area showed negative changes, and the amplitude of the negative changes was smaller than that of the positive changes. Changes in the Curie point depth and gas volume do not significantly alter the spatial characteristics of the LMF.