Quality Assessment and Treatment Method of Wellbore with Casing Damage and Deformation

Abstract In the process of oilfield development, the casing is damaged inevitably to varying degrees as the increased service life of casing and the adjusted development plans constantly, which has become a common problem in major oilfields in China. Data shows that in 2022, China National Petroleum Corporation (CNPC) alone had over 15000 wells with damaged and deformed casing, with nearly 2000 new wells added, affecting the safety production and economic benefits of oil and gas wells seriously. This article focuses on more than 100 newly added wells with damaged casing in a oilfield from 2022 to 2024. Key factors such as overall angle change rate, hole enlargement rate, and fill-up of cement are used to determine the quality of well and cementing, and to evaluate the quality of wellbore. According to the evaluation criteria for wellbore quality during completion, 102 wells were evaluated and 16 wells were found to have poor wellbore quality, with a pass rate of 84.3%; According to the evaluation criteria for cementing quality during well completion, 104 wells were evaluated and 12 wells were found to have poor cementing quality, with a pass rate of 88.5%. Based on the evaluation results, the causes of damaged and deformed casing are analyzed from geological factors, engineering technology selection, material durability, and other aspects. Combined with existing repair technologies and preventive measures for damaged and deformed casing, targeted measures are proposed to provide support for the effective management of wells with damaged and deformed casing in oil fields.