Equivalent circulating density modeling of Yield Power Law fluids validated with CFD approach

A numerical and experimental analysis is conducted on the flow of Newtonian and non-Newtonian fluids in annuli. A numerical model is presented that accurately estimates the annular frictional pressure losses with and without the inner pipe rotation. The numerical model is validated using a CFD software. Experiments are conducted at a 27m long flow loop using various fluids that can be characterized as Yield Power Law (YPL). The results of the experiments are compared with the results obtained with the numerical model. Today, the most drilling fluids show YPL behavior. The proposed numerical model can calculate the equivalent circulating density while circulating YPL fluids accurately. The model is validated with a CFD software and compared with experimental results, the published experimental results and with the slot approximation. The results obtained from the numerical model shows good agreement with the experiments and also with the experimental results from the literature. The comparisons between the models indicate that the slot approximation can result in large errors especially when the diameter ratio is low, meaning the diameter of the inner pipe is significantly smaller compared to outer pipe. The numerical model is coupled with a stability criterion that determines the onset and offset of the transitional flow between laminar and turbulent regions of YPL fluids. Various degrees of eccentricity are analyzed in terms of pressure profile and flow stability with the proposed method. This study contributes to a better understanding of flow in annuli. The results obtained from this study are useful to predict the transition and the annular frictional pressure loss profiles more accurately than existing methods. Potential applications include risk avoidance and optimized operations. •The pressure losses while circulating Yield Power Law fluids is analyzed.•We propose a numerical model that accurately predicts the annular pressure losses.•CFD analysis is conducted to validate the numerical model.•Numerical model is compared with the experiments and with models from literature.