Combined Effect of Rheological Model and Equivalent Diameter Definitions on Pressure Losses/Equivalent Circulating Density Estimation

Abstract

Without accurate estimation of annular pressure losses it is possible to face serious problems that would yield to interruption in drilling operation and sometimes lead to the abandonment of the well. Therefore, exact estimation of annular pressure losses is vital in drilling and well completion operations to control formation pressure and optimize drilling and completion fluids hydraulic program.

Many investigators have proposed different equivalent diameter concept to provide a similarity between pipe and annular flow. The study provides analysis on how severely the annular pressure losses/ ECD varies once rheological model and equivalent diameter definitions are changed for different operating conditions, the pressure loss gradients / ECD calculated using annular frictional pressure equations were used as the basis of the relating the results obtained using the rheological model- equivalent diameter definition combinations.

The variation in rheological parameter and fluid properties due to the changing bottom hole condition were also analyzed. Bingham Plastic Model and Crettendon criteria (equivalent diameter) couple was found to fit closely to results obtained using annular pressure loss equations.