True Power Law Drilling Fluid Model: Effect of Its Rheological Parameters on Static Particle Settling Velocity (original) (raw)
Adequate cuttings removal from the bottom hole of an oil well to the surface during a rotary drilling is critical for cost-effective drilling. The major factors that describe cuttings transport particularly in vertical sections are fluid effective viscosity and velocity which influence particle settling velocity. Rheological modelling of drilling fluids in oil fields is usually described by Bingham plastic and power law models. These models gain popularity because their specific descriptive parameters are fairly easy to estimate. Standard methods use Fann V-G Meter dial reading at 600 and 300 rpm to determine these rheological parameters. Unfortunately, these points correspond to higher shear rates which seldom prevail during particle settling. This work aims to investigate different shear rates to derive power law rheological parameters and show their influence on the magnitude of effective viscosity and hence settling velocity. The results show that data pair of R600/R3 was the best to predict the full spectrum of the fluid rheogram. Using Chien (1994) correlation, data pair of R200/R100 give the best results for predicting observed settling velocity of a nonspherical particle settling in a static fluid. Data pair of R200/R100 out performs commonly used data pairs (R600/R300, R100/R3 and R6/R3). Furthermore, Using modified Moore correlation with effective viscosity as suggested by Chien obtained excellent predictions with error less than 1% particularly with R600/R100.
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