Research and application of KCL/silicate drilling fluid in block 6 of Sudan

In consideration of saving costs in block 6 of Sudan, the operating company changed the structure of some wells to ‘two-section’ instead of ‘three-section’. Thus formation with different pressure factors and characteristics is in the same bore hole which would cause complex problems in the hole such as lost circulation and borehole collapse and under which the original drilling fluid technology could not meet the demand for drilling. Thus, the original drilling fluid technology is improved according to the formation characteristics. The practical KCL/silicate drilling fluid system is developed based on a lot of experiments in lab and on site. The new drilling fluid can increase sustainable pressure of upper formation to 1.25 g/cm3 and can drill safely with a narrow safety density window. The effective control of solid concentration of drilling fluid can overcome the difficulties in control the rheological property and realize the stable conversion of drilling fluid system in drill process. The new KCL/Silicate drilling fluid solves the potential risk of caving and lost circulation problems in long bore hole with different formation properties, pressures after the wellbore structure changes, reducing, system conversation time and the drainage of waste drilling fluid significantly, propenties, shortentingthe drilling period and cuuting costs of drilling fluid materials.