Research On Formulation Of High-density Oil-based Drilling Fluid With High-temperature

In the process of oil and gas exploration and development, more and more complex deep wells have been drilled. In the process of drilling practice, the big challenge thatthe bottom hole temperature is too high and the formation pressure coefficient is large with well depth increasing. High temperature in downhole is an important factor that affects the performance of drilling fluid, especially makes the filtration loss and rheological properties and the stability of the settlement difficult to control.The traditional water-based drilling fluid can’t meet fully the requirements of drilling at present. Therefore, research on oil-based drilling fluid technology which can satisfy the high temperature(> 180 ℃),high density(>2.0g/cm3) and forming oil-based drilling fluid system for high temperature and high density is must. The oil-based drilling fluid system has guiding significance for improving oil-based drilling fluid, so that it can meet the technical demands of our country on safety, fast,high-quality, efficient drilling of deep wells in the complex formation.Based on drilling fluid technology problem in complicated deep well, constituent of oil base drilling fluid are determined through lab experiment by means of single factor experiment and orthogonal experiment. They are oil base fluid, organic soil, fluid loss agent, wetting agent and emulsifier etc.The formula of high-temperature and high-density oil-based and water-in-oil drilling fluid which can be used at temperatures as high 220 ℃ and adjusted to 2.2 g/cm3 are developed. Several key properties which is difficult to control such as settlement stability, rheology,anti-pollution performance are evaluated under the condition of high temperature and by means of high temperature aging test in laboratory. The results showed that the two kinds of oil base drilling fluid formulation developed perform well.At last, during the preliminary field trial process in N94 well, oil-based drilling fluid formula performs well on rheology, inhibition, cuttings carrying capacity, borehole stability, high mechanical drilling speed, less bit wear and high efficiency in waste oil-based drilling cuttings processing. Related research results not only provides practical basis for oil based drilling fluid applying in the complicated wells but also has practical significance and application value in solving the popularization and application of oil-based drilling fluid in drilling engineering.