Drilling Fluid Development and Performance Evaluation of Deep and Ultra-deep High-density Saturated Brine

Due to the high temperature, great pressure and complex lithology of super-deep well bottom, there exist such problems such as high solid concentration, multiple but inaccurate treating chemicals, complex formulation with instability of drilling fluid system, resulting in a frequent occurrence of underground complex accident and a waste of a lot of manpower and material resources. Therefore, based on the analysis of performance factors of ultra-deep drilling fluid system, the approach of regulating water based drilling fluid properties of super-deep well has been found. Moreover, through screening and processing optimization of treating chemicals of ultra-deep well by single-factor method, three sets of anti-high-density and anti-high-temperature saturated brine drilling fluid systems with few kinds of treating chemicals, concise and simplified system, including: (1) saturated brine drilling fluid with anti-temperature 180 degrees C and density 2.40 g/cm(3); (2) saturated brine drilling fluid with anti-temperature 200 degrees C and density 2.40g/cm(3); (3) saturated brine drilling fluid with anti-temperature 220 degrees C and density 2.40g/cm(3). After the the evaluation of the overall performance of these three systems under respective experimental conditions, the results show that all of these systems have such advantages as good and strong rheology, water loss building capacity, inhibition, lubricity and blocking ability, etc, which could meet the requirements of ultra-deep drilling under different circumstances.