Study On High-temperature Function Mechanism And Rheology Of High Density Water-based Drilling Fluid

The rheology control of high temperature High density drilling fluid is the main technical problem of the drilling fluid technical.Based on the sum-up and analysis of main characteristic of high temperature high density drilling fluid by documentary search,the high temperature mechanisms of function mechanism were studied by investigating the effects of aging tempetature, pH value and bentonite content on the viscosity, yield value and API filtration of bentonite slurry.A new fluid loss additive called JZA-1 was selected as the main additive for high temperature high density drilling fluid system by a lot of experiments.JZA-1 was good at resisting high temperature, salt and calcium.The active mechanism of JZA-1 was studied. JZA-1 was absorted well at the clay particles, the adsorptive capacity of JZA-1 is much larger than SPC-220 and SMP-1. The absorbtion can highlight theζelectric potential, add the thickness of hydration shell in the surface of clay particles and firm the clay particles agglutination.A formulation of water-based drilling fluid of high temperature high density was developed using JZA-1 and SPC-220 as key additives. The main type of additive and optimized of amounts was studied to optimize the drilling fluid. This developed system has high temperature resistance(220℃),good aggravation capability to 2.2g/cm3,calcium and salt tolerance and the tolerance of poor clay reached 15%.By studying the rheological properties of drilling fluid system and found that the system of bentonite content,volumen of KCl and fluid loss addtives, the order of addtive,are the Influencing factors of rehology. It was found that an appropriate amount of KCl should be added fist, so that the clay particles together to form a coarse dispersion, and then add the other additive.The affect of high temperature to rheological parameters was studied by HTHP rheology experiments, with the temperature increases, the drilling fluid apparent viscosity and plastic viscosity decreased , after one temperature point, the viscosity increased. This is the result of stress and high temperature.Simulation results show that: at 50 ~ 220℃within the scope of the study, H-B model was the best. Bingham and Carson mode models are ineffective at a temperature of 220℃.Power-law model is not suitable for simulation of high-density drilling fluid rheology of high temperature and high pressure situations.