Abstract
In Bohai bay, heavy oil reserves account for 70% of the total proved oil reserves. Most extensive enhanced oil recovery technique is cyclic steam stimulation, which would poses significant challenges to cementing operation. Cement integrity under multi-cyclic steam stimulation limits conventional cement slurry systems, especially when the steam injection temperature is as high as 350 °C. Besides, leakage formation, shallow gas and acid corrosion also increased the complexity of the cementing jobs. A novel lightweight, high-temperature-resistant cement system had been developed in order to ensure long-term effective isolation of the layer when exposed to ultra-high temperature(350 °C) due to cyclic steam stimulation. This paper will describe the design and evaluation of cement slurry in details. With the novel cement system, cementing operation in steam recovery wells had been successfully carried out over 20 wells. CBL logging tests showed excellent bonding result. Advanced long-term zonal isolation for 3 years under constant steam injection had been achieved. This successful cement operation has great reference in the cementing industry.