Leakage Prevention Cementing Technology for Liner in Adjustment Wells of Chenghai Oilfield Bohai Bay

The target formation in the Chenghai offshore area of Bohai Bay is characterized by shallow burial depth and a low formation pressure bearing capacity. The leakage pressure coefficient of the principal oil-bearing stratum, the Guantao Formation, is generally less than 1.35 g/cm3. Owing to the extended period of block development, the formation pressure regime has become increasingly complex, resulting in frequent and severe losses during drilling operations. Conventional cementing practices have proven inadequate in addressing challenges such as insufficient cement column height and suboptimal cementing quality during liner cementing in adjustment wells, both of which are precipitated by formation losses. To overcome these issues, a suite of differentiated and targeted designs was developed, tailored to the actual formation pressure bearing capacity encountered during drilling. These designs encompassed modifications to the slurry column structure, enhancements to liner tool functionality, and the implementation of specific loss remediation strategies. The application of technologies such as solidified spacer fluid and the optimization of casing centralization culminated in the development of a novel leakage prevention cementing technology. This approach was successfully deployed in five consecutive wells, with no cementing losses observed. Field results indicate that, relative to wells drilled within the same block over the preceding two years, the qualification rates for cementing at the first and second interfaces increased by 13% and 25%, respectively. This leakage prevention cementing technology thus serves as a valuable reference for the redevelopment of mature wells, the augmentation of reserves and production in the Chenghai Oilfield, and for cementing operations in wells susceptible to formation losses.