Abstract: From 2016 to 2022,the recovery rate of oil well productivity in Bohai A Oilfield continued to decline after the workover operation. Since 2018,due to high temperature and corrosion issues,scaling has occurred in the central pipes of multiple wells,resulting in extended downtime for maintenance,reduced annual production per well,and increased operating costs. To solve the problems of low capacity recovery rate and well pipe scaling,through the analysis of reservoir properties,subsurface fluid properties,and rock surface physicochemical characteristics,the article finds that the wells with low productivity recovery rate are mainly concentrated in the Shahejie formation reservoir which has low-to-moderate permeability and high wax content. The reason is that the inherent potential damage factors of the formation are induced by various external conditions,such as water lock damage and inorganic scale deposition accompanied by the whole development and production process of the oilfield,as well as wax deposition in the low-to-moderate water cut stage. The combined action of the three factors ultimately leads to a significant reduction in the absolute or relative permeability of the oil reservoir and a decline in the oil well output.

Key words: Bohai Oilfield, workover, Shahejie formation reservoir, productivity recovery rate, reservoir damage, water lock, wax deposition, inorganic scale