Processing Techinc Of CO₂ Invading Drilling Fluid In Daqing Deep Well

Organosilicon drilling fluid is what Daqing Xujiaweizi area used in deep zone exploration drilling, the system presents good high-temperature resistence and is applied in many deep wells around 4500m. However, it is found out in the drilling process that after the Organosilicon drilling fluid is invaded by CO₂ from the formation, the colour gets darken, viscosity and shearing force sharp increases, rheological property behaves bad, both the concentration of HCO₃^- and CO₃^2- increases, the concentration of OH? decreases and the pH gets lower. All these changes can be proved by a simulation experiment of CO₂ invading the drilling fluid. If it is heavily polluted and can't be put into operation, the invasion must be removed to meet the regular drilling requirement. After the pollution caused by the two-kind ions, it is hard to adjust the drilling fluid properties by the method of adding treatment agents, as a result, chemical method is the only way to remove. Providing appropriate amount of Ca²⁺ to the drilling fluid, it will react with the two-kind ions to form CaCO3 precipitate and achieve the objective of cleaning away the pollution. Through the laboratory experiments, gelling fluid formula system with CaO, KOH and FCLS is optimized, it behaves good properties of preventing and processing the CO2 pollution. At the same time, I make an intensive research on HTHP rheology about drilling fluid both before and after the pollution and handled drilling fluid.