Research and Application of High-Density Cementing Slurry Technology under the Condition of Oil-based Drilling Fluid in Salt Formation

In view of the geological characteristics of high pressure in salt-gypsum formation of deep wells in Tarim Piedmont structure, high-density oil-based drilling fluids are widely used, which makes it difficult for subsequent cementing work. In order to solve the technical difficulties of cementing high-density oil-based drilling fluid and salt-gypsum formation in KS well, which is a key exploration well in this area, through analysis of cementing technical problems, combined with salt-gypsum formation cementing and deep well ultra-deep well cementing technology, targeted measures before casing running, optimization of flushing aggravated isolating fluid and aggravating agent are carried out. In addition, relevant technical measures are put forward based on the optimization of cement slurry additives, the design of slurry formulation pipe string structure and the optimization of cementing technology. A set of flushing aggravating isolating fluid was prepared by introducing small particle size, concentrated superfine aggravating agent and hematite powder with relatively large particle size, and a set of high-density cement slurry with good comprehensive performance was obtained by optimizing cement slurry additives and introducing super high-density aggravating agent GM-1. In order to ensure the safety of cementing, the adaptability test of cement slurry formula was carried out, focusing on the adaptability test of cement slurry temperature and density: when the temperature changes + 5 °C the density increases + 0.03 g/cm3, the thickening time of the system changes less than 44 min, the system has good stability, and the anti-channeling performance of cement slurry SPN is less than 3, which has good anti-channeling function and meets the construction requirements, At the same time, the compatibility experiments of different proportions and different media and the simulated intermittent cementing experiments are added to meet the requirements. Field application of KS well shows that the technology can meet the cementing requirement of oil-based drilling fluid in Piedmont area.