Avaliação dos efeitos de alta pressão e temperatura na reologia de fluidos de perfuração à base olefina

Abstract

Determining the rheological properties of a drilling fluid as a function of pressure and temperature is essential for drilling oil wells under HPHT conditions, as well as the successful prediction of the hydraulic system depends on the precise representation of the drilling fluid rheology. This study aimed to evaluate the effects of high temperatures (up to 125 ° C) and high pressures (up to 800 bar) on the rheological behavior of olefin-based drilling fluids based on olefin. Rheometric trials were performed on the Anton Paar MCR 702 TD rheometer attached with the pressure cell system, with a maximum pressure limit of 1000 bar. The experiments consisted of obtaining the flow curve, start-up from controlled shear rate and oscillatory stress sweeps tests. The thermal stability of the drilling fluid was investigated through thermal aging tests carried out in a rotating oven at 150 ° C. The results indicated that the drilling fluid tested is thermostable up to a temperature of 150 °C and that the thermal history experienced by the drilling fluid has caused reductions in the apparent viscosity and yield stress. While obtaining the flow curves at atmospheric pressure and different temperatures, it was observed that the increase in temperature provided some reduction in the apparent viscosity and fluid’s dynamic yield stress. The results of the oscillatory tests showed that both temperature and pressure affected structural behavior of the drilling fluid but in different ways. The increase in temperature tended to decrease the storage and dissipation modules, while the pressure tended to increase them. During the analysis of the flow curves in HPHT conditions, it was observed that the effects of pressure are dominant at room temperature, however, when the fluid subjected to high temperatures, the effects of pressure are only significant at pressures greater than 270 bar. With the help of statistical tools, it was possible to develop a representative polynomial model that related the apparent viscosity to pressure, temperature, and strain rate.