An acid fracturing technology suitable for high-temperature ultradeep gas wells in the Qixia Formation in the north of Western Sichuan

The Qixia Formation in the north of Western Sichuan is characterized by great burial depth, high temperature and small and medium pores with different development degrees, and its acid fracturing is faced with a series of difficulties, e.g. high friction resistance, fast acid-rock reaction and difficult maintenance of flow conductivity of etched fractures. In order to improve the pertinence of acid fracturing design to the reservoir of Qixia Formation, the acid-rock reaction heat model was established and the morphologies of the fractures induced by multi-field coupling acid fracturing were simulated. It is indicated that the acid-rock reaction heat can increase the acid-rock reaction rate and reduce the length of etched fracture. When there is 200 m³ acid, the maximum effect on the length of etched fracture is 9 m. When the construction displacement is constant, the length of etched fracture increases with the increase of acid volume, but its increasing amplitude declines gradually. Field tests were carried out 4 well times and the average gas production per well was 67.03×10⁴ m³/d. It is revealed that the effect of acid-rock reaction heat on the morphologies of etched fractures in high-temperature ultradeep gas wells shall not be neglected and multi-field coupling acid fracturing design method is better adaptable to the Qixia Formation in the north of western Sichuan Basin.