The operator’s Xiangguosi (XGS) gasfield facility began underground gas storage (UGS) operations in a depleted gas field in southwest China in 2013. Following this initial period, the site was reassessed to increase deliverability safely during the winter months to meet future peak gas demand. The results of that analysis informed the resulting system design, in combination with fit-for-purpose reservoir-surveillance systems; caprock‑seal recording pressure, rock deformation, and seismicity data in real time; and regular wellbore inspection.
Introduction
The XGS UGS facility currently operates in a previously depleted gas reservoir in Sichuan province. Its construction took place during the second half of 2011; cushion gas injection started in June 2013. Located in a high-tectonic-stress region, the geological setting of the XGS field is structurally complex and highly faulted and the targeted carbonate formation is heterogeneous and naturally fractured.
When the studies described in the complete paper commenced in November 2019, the field hosted 22.80×108 m3 of working gas along with 19.80×108 m3 of cushion gas. As of May 2020, the reservoir had completed eight injection and six withdrawal cycles and delivered a maximum withdrawal rate of 21.96×106 m3/d.
The UGS conversion plans required a revisit to analyze the possibility of increasing the withdrawal rate to 28.55×106 m3/d, thereby positioning better for future peak gas demand.
