Feasibility Analysis of the Utilization of Directional Butted-Well Salt Caverns with Large Height Difference for Underground Energy Storage

The reconstruction and utilization of old salt caverns with butted wells are of great significance for accelerating the construction of large-scale underground energy storage facilities, realizing energy transformation, and achieving the “dual carbon” goals. However, the renovation work of old butted-well caverns is still in its infancy, facing technical bottlenecks in transformation methods and operational safety. This paper takes the butted-well salt cavern with a large height difference in Pingdingshan, Henan province, as the research object. Through theoretical analysis and numerical simulation, the feasibility of its reconstruction and utilization is systematically studied from the aspects of gas injection and brine discharge methods, technology parameters, and operation stability. The results show that the gas injection and brine drainage method of butted-well salt caverns is closely related to residue utilization. The “one-injection-one-discharge” method is suitable for the old butted-well salt cavern with a large height difference, considering residue utilization and economy. During gas storage, there are significant deformation differences on both sides of the cavity. The deeper cavern suffers more damage and has weaker stability compared with the shallower one, and the conventional method for determining the operating pressure based on the casing shoe has limitations. The internal pressures of this salt-cavern gas storage structure are basically equal. A new mode for determining the operating pressure of these large-height-difference butted-well salt caverns is proposed: taking the lower limit for the deeper cavern and the upper limit for the shallower one. Based on theoretical analysis, numerical simulation, and on-site pilot test insights, the renovation and utilization of old large-height-difference butted-well caverns are feasible. This study provides guidance for converting butted-well salt caverns into underground energy storage structures and accelerating the development of new-type energy storage facilities.