Cementing technology for leaky formation in the Bohai Oilfield

Offshore oil and gas exploration and development is a high-risk operation with high operation cost.In the Bohai Sea, thief zones have a great impact on the cementing quality and operation efficiency.Once the leakage occurs during cementing, the operation risk will be increased.Furthermore, the treatment of downhole complication will decrease the operation efficiency and increase the operation cost, which runs counter to the guiding principle of cost reduction and efficiency increase.The lost circulation materials were studied, and the design of cement slurry was modified and innovated based on the situation of thief zones in the Bohai Sea.Then, the construction plan of the cementing operation of absorption wells was refined and optimized by conducting experimental studies.The double-acting spacer fluid and cement slurry system with good plugging performance was developed by adding the optimized lost circulation material into the spacer fluid.Afterwards, the specific construction parameters of each step were checked and adjusted through software calculation to control the bottom hole ECD in the process of cementing.Finally, these technologies were applied in the actual operation.Thanks to their application, downhole leakage is prevented in the whole process of cementing, the cementing of leakage sections is completed smoothly, the cementing quality is improved and the requirements of well control and oil reservoirs are satisfied.