The Effect of high temperature and aging on water-base drilling fluids

Abstract

Driling fluid property changes due to elevated temperature andaging time frequently cause problems in drilling deep wells. A laboratory investigation of the effect of high temperature (490?F) and long aging time (30 days) on water-base drilling fluid properties is made with Fann Model 70 HTHP Viscometer and Baroid Roller Oven. The results show a decrese in viscosity, yield point and gel strength with the increase in temperature. Shear stress for a particular temperature increases with the increase in shear rate, but shear stress at a given shear rate decreases with the increase in temperature. Viscosity, yield point and gel strength at a given temperature increse with aging time and aging effects are diminishing with the increase in aging time. Shear stress at a given shear rate increases with aging time and aging effects decrease with the increase in aging time. Finally, the value of the exponent of power law index is calculated and found to be always less than unity.