Study On High Temperature Seawater Drilling Fluid Formula

With the development of deep-sea exploration and deep-sea resource exploration in China,higher requirements are placed on seawater drilling fluids.Combined with the formation conditions and the status of drilling fluid systems at home and abroad,the formula of a seawater-based drilling fluid system resistant to high temperatures of230°C is designed.Through literature research and laboratory experiments,the influence of high temperature and various electrolytes in seawater on the performance of drilling fluid is analyzed.Through theoretical analysis and experiment of the influence of temperature and dosage on clay,it is concluded that the effects of high temperature on clay seawater base fluid include high temperature dispersion,high temperature coalescence and high temperature passivation.At different temperatures,different functions will dominate,resulting in high-temperature thickening,thickening and other phenomena.At the same time,it was also found that the addition of a certain amount of clay has a positive effect on the rheological properties and filtration performance of the drilling fluid,but the addition is limited.The high salinity of seawater will compress the double layer of clay diffusion,thereby causing the coal to coalesce and weaken the hydration and dispersion of the clay.The cations with higher valence are more likely to cause the clay to coalesce and not disperse.The coalescence stability of drilling fluid directly affects the dynamic stability,and the clay colloid with poor coalescence stability is prone to delamination.Through the experimental study on the effect of pH adjuster on the seawater base fluid,It is concluded that appropriate amounts of soda ash and caustic soda can improve the rheology and fluid loss properties of sodium bentonite by removing calcium and magnesium ions,but excess soda ash will affect the performance of the base fluid.Increasing the amount of caustic soda will improve the performance of seawater base fluid,and the pH should be controlled within a reasonable range.Through experiments,the optimal dosage of the pH adjusting agent in the seawater-based fluid is optimized.On the basis of this theoretical basis,the best performance pulping material is selected;the drilling fluid is formulated with simulated seawater,the effect of the amount of pulping material on the performance of the seawater base fluid is studied,and the optimal dosage is determined;The seawater base fluid is added with different treatment agents to explore the effect of high temperature on the performance of different treatment agents.The single factor method is used to optimize the treatment agent for the 230?high temperature seawater drilling fluid system.Based on the single factor optimization of the components of the system,the orthogonal test method was used to carry out the optimization study of the formulation of the anti-230?high temperature seawater drilling fluid system.Perform a range analysis on the main factors in the orthogonal test results,find out the optimal level combination of each factor,and finally select a formula that resists high temperature seawater drilling fluid at 230?,and each performance meets the technical requirements of the project.The weighting material and amount are preferably optimized.The density of the drilling fluid system(1.13 g/cm~3)is adjusted to 1.5g/cm~3.The performance evaluation results show that the performance meets the technical requirements of the project.The 230?high temperature seawater drilling fluid system not only has good rheology and fluid loss performance that meets the technical requirements of the project,but also has good suppression and lubrication properties,reflecting the good high temperature resistance of drilling fluid stability.