Research on Stability Evaluation and Adjustment Method of Concentrated Casing Damage Area Based on Gradient Lifting Algorithm

Casing damage is a common problem faced in the development of old oilfields. Some areas with weak mechanical properties of rock layers and other unfavorable factors are prone to severe casing damage, such as time of occurrence and plane distribution of casing damage wells. The stable state of damaged rock formations is a prerequisite for the implementation of workover and remaining oil tapping. Traditional stability evaluation of damaged areas often relies on qualitative analysis through well condition investigation and engineering logging, with incomplete considerations and a high rate of judgment errors, often leading to secondary concentrated casing damage after treatment. Therefore, based on the research and understanding of centralized casing damage mechanism, taking into account the changes in casing damage situation and the control of inducing factors, 9 indicators are selected to establish an evaluation index system for stability of casing damage areas. Gradient lifting algorithm is applied to achieve quantitative grading evaluation of the stability, with a verification compliance rate of 83.3%; meanwhile, classified adjustment measures are implemented to overcome unstable aspects, shorten the adjustment cycle, determine the timing of overall governance as soon as possible, and ensure the oil recovery of casing damage areas. This method was applied in the X67 casing damage area, guiding the implementation of various stability control workloads for 49 wells, and effectively improving the stability of the casing damage area.