Research On The Rheology Behavior And Hydraulic Calculation Of High Density Drilling Fluids

At present, it is significant to understand the rheology of the drilling fluid and predict bottom hole circulation pressure. In this thesis, a HT rheometer is used to measure the rheology of drilling fluid at high temperature and high pressure condition. There are five high- dense drilling fluid to be studied, three among of them are deployed in laboratory, another two are provided by field. HTHP rheology of these five drilling fluid was analyzed in this paper, it found that apparent viscosity, plastic viscosity and yield value changed obviously with temperature and pressure increasing; meantime, the law of variation of rheological parameters affected by temperature and pressure was analyzed.Based on a mount of experiments and regression analysis of experimental data, powerlaw model, binham model and casson model were used to fit the rheology of drilling fluid, and correlation parameters were obtained. The results showed that the related parameter R value that was obtained from powerlaw model changed little and approached one with temperature increasing. Therefore, it is accurate to describe the actual rheology of drilling fluid using powerlaw model at HTHP condition. This conclusion provided theoretical foundation for calculating bottom hole circulating and annual pressure lost.Through studying the affect of temperature and pressure to the rheological parameters, referring rheology of drilling fluid and hydraulics arithmetic, based on basic equation of hydromechanics, the whole cycle process of drilling fluid as the research object, the multiphase flow during drilling and extra-heavy drill rob was considered as affect factors, integrating the mathematical model studying the density of drilling fluid with well depth, the method for calculating bottom hole circulating and annual pressure lost. Meantime, according to the developed theory and method, a software is developed to calculate the down hole pressure at HTHP condition. This software can calculate bottom hole circulating pressure, hydrostatic fluid column pressure, down-hole drilling fluid density in deep well at HTHP condition, circulating density, cutting carrying velocity, critical returning velocity and so on. In addition, it can memory down hole circulating pressure at different depth, and draw relevant curves. According to the caparison of theoretical date and practical date, the difference was allowable, so this software can service for the field.