Cementing Technology of Salt Layer in Wen23 Gas Storage

Abstract

The construction of Zhongyuan gas storage group takes the salt layer as the caprock. Therefore, the cementing quality of the sealed salt interval is a key factor in the construction of gas storage. The cement slurry was eroded by the salt gypsum layer during the migration of the salt layer, which affects the basic performance of cement slurry, resulting in the poor cementation quality between cement sheath and salt layer. In addition, the irregular borehole in the salt layer and the expansion of well diameter make the displacement efficiency poor in the cementing process, which restricts the cementing quality of this kind of wells. At present, due to the unsatisfactory cementing quality and low excellent rate of cementing quality in the salt layer during the construction of Wen 23 gas storage, the construction of gas storage cannot be completed as planned. Therefore, in order to ensure the successful construction and service life of gas storage, the cementing technology research of big-thickness salt layer in Zhongyuan Gas Storage Group is carried out. The salt resistant fluid loss reducer and retarder are selected through the project test, and the expansion early strength agent and toughening agent are selected. Through the compatibility research and the evaluation of the performance of cement slurry and the cementation strength of cement stone by the erosion of different salt content, a fresh-water-salt-resistant and ductile cement slurry system suitable for salt rock cementing is formed; In terms of cementing technology, we have developed well hole optimization technology, optimized leakage prevention technology in salt section and supporting high-quality sealing technology in salt layer, formed cementing technology and recommended practices for Wen 23 gas storage, and effectively ensured the primary success rate of cementing in Wen 23 gas storage. The research results of this subject have been successfully applied in 12 wells of Wen 23 gas storage and Wei 11 gas storage. The qualified rate of cementing quality has been increased from 96% to 100% and the excellent rate has been increased from 12% to 83.33%, which meets the requirements of gas storage for salt layer sealing quality and ensures the safe and efficient operation of Zhongyuan Gas Storage Group.