Search Results (3)

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. Full article

The small-spacing dual-well (SSDW) technique plays a crucial role in the establishment of underground salt cavern gas storage reservoirs. However, during the cavity dissolution and brine discharge processes, insoluble sediment is prone to being carried into the discharge tubing with the brine, leading to tubing blockages or clogging, which disrupts injection and withdrawal operations and severely affects both project efficiency and the safety of the gas storage facility. This study systematically analyzes the influence of the gap between the injection and discharge tubing and the surface of the sediment-on-sediment movement, deposition, and tubing safety in SSDW salt caverns. Through numerical simulations, this study investigates the influence of tubing layout on the internal flow field distribution of the cavern and the suspension behavior of sediment, revealing the changing trend of the risk of sediment entering the tubing at different distances. The results show that a rational tubing distance can significantly lower the risk of sediment backflow and tubing entry, while maintaining high brine discharge efficiency. Based on the simulation results, an optimized tubing layout design suitable for SSDW salt caverns is proposed, offering technical direction to guarantee the safe and effective functioning of underground salt cavern gas storage sites. Full article

Geological conditions of salt cavern gas storage in China are characterized by dominantly layered salt layers with a high content of insoluble mudstone. After the water leaching of the salt layer, a large amount of sediment accumulates at the bottom of the gas storage cavity. During the gas injection process, only the clean brine above the sediment can be expelled, leaving a brine layer of 2–5 m and a large amount of brine in the pore space of the sediment. To increase storage capacity, it is urgent to explore the secondary gas injection and brine drainage technology to further expel residual brine in pores of the sediment at the cavern bottom. The sediment is relatively loosely packed and is composed of mudstone particles, which easily migrate and block the brine withdrawal pipe. In this paper, firstly, the mineral composition, particle size and distribution characteristics of the sediment at the bottom of the salt cavern are fully understood by XRD and sieve analysis methods. Then, a lab simulation device suitable for secondary gas injection and brine drainage of a high-salinity salt cavern with a diameter and height of 25 cm was designed and built. A screen sand control experiment, a gravel pack artificial wall sand control experiment and chemical cementing sand were simulated. The effects of gas injection, brine drainage pressure, brine layer height and insoluble particle size on sand production and liquid drainage were studied. The influence factors of brine withdrawal on the sand control in secondary brine drainage were intensively investigated, and finally, the gravel pack artificial wall sand control technology system was recommended. The optimal construction parameters for secondary brine discharge are recommended as follows: Under the condition of gravel packing with the same particle size, the trend of sand content with different artificial wall thicknesses is not obvious, and a 2 cm wall thickness is the best in the overall experiment, corresponding to 28 cm in the field. The larger the particle size of the gravel pack, the better the sand control, and the best gravel size is 10–20 mesh. The injection pressure should be as low as possible. Full article