A well killing method for the wells with same pressure of tubing and casing in Bohai Oilfield

As Bohai Oilfield moves to the development of medium and deep layers, some oil and gas wells in the Bohai Sea area are faced with the difficulties of the same pressure of tubing and casing, pressurized casing and no circulation killing path, which bring the risks to the string lifting in the process of workover operation.The key to the optimization of well killing method is to analyze the reason for the same pressure of tubing and casing and search for the string leak location.11 methods were studied, including fluid resistivity method for leak detection, multi-arm caliper imaging logging, electromagnetic defect detection logging and well temperature noise logging, and the leak detection method suitable for the wells with the same pressure of tubing and casing was proposed.Then, the mechanisms of different killing methods were studied for different leak locations, and the well killing method of grading optimization was proposed.By virtue of the selected well killing method, the operations of dismantling Christmas tree, lifting string and installing wellhead BOP can be successfully performed.In conclusion, this paper is practically of guiding significance to the string lifting operation of the wells with the same pressure of tubing and casing or the pressurized casing.