Effect of drill pipe orbital motion on non-Newtonian fluid flow in an eccentric wellbore: a study with computational fluid dynamics

To ensure an effective drilling operation of an explored well, the associated hydraulics program should be established carefully based on the correct prediction of a drilling fluid’s pressure drop and velocity field. For that, the impact of the drill string orbital motion should be considered by drilling engineers since it has an important influence on the flow of drilling fluid and cuttings transport process. In the present investigation, the finite volume method coupled with the sliding mesh approach is used to analyze the influence of the inner cylinder orbital motion on the flow of a power-law fluid (Ostwald-de Waele) in an annular geometry. The findings indicate that the orbital motion positively affects the homogeneity of the power-law axial velocity through the entire eccentric annulus; however, this impact diminishes as the diameter ratio increases. In addition, higher torque is induced when the orbital motion occurs, especially for high values of eccentricity and diameter ratio; nonetheless, a slight decrease in torque is recorded when the fluid velocity increases.

Improved Energy Efficiency of Mixed Convection Heating Process in Eccentric Annulus

This paper deals with a numerical study of mixed convection heat transfer in horizontal eccentric annulus. The inner cylinder is supposed hot and rotating, however the outer one is kept cold and motionless. The numerical problem was solved using COMSOL Multiphysics® which is based on finite element method. The resolution of the partial differential equations was conducted through an implicit scheme with the use of the damped Newton’s method. The present numerical analysis concerns the effect of eccentricity, rotation speed and Rayleigh number on the flow patterns, heat transfer rate, and energy efficiency of the process. It was found that the heat transfer rate increases with the increase of Rayleigh number. In addition, the heat transfer rate drops with the increase of rotation speed. Finally, we have demonstrated that maximum energy efficiency is achieved not only with higher Rayleigh number but also it is maximum with small eccentricity.

Application of Deep Learning Technique to Predict Downhole Pressure Differential in Eccentric Annulus of Ultra-Deep Well

Accurate prediction of downhole pressure differential (surge/swab pressure gradient) in the eccentric annulus of ultra-deep wells during tripping operation is a necessity to optimize well geometry, reduction of drilling anomalies, and prevention of hazardous drilling accidents. Therefore, a new predictive model is developed to forecast surge/swab pressure gradient by using feed-forward and backpropagation deep neural networks (FFBP-DNN). A theoretical-based model is developed that follows the physical and mechanical aspects of surge/swab pressure generation in eccentric annulus during tripping operation. The data generated from this model, field data, and experimental data are used to train and test the FFBP-DNN networks. The network is developed used Keras’s deep learning framework. After testing the models, the most optimal arrangement of FFBP-DNN is the ReLU algorithm as an activation function, 4-hidden layers, the learning rate of 0.003, and 2300 of training numbers. The optimum FFBP-DNN model is validated by comparing it with field data (Wells K 470 and K 480, North Sea). It shows an excellent argument between predicted data and field data with an error range of ±7.68 %.

A Comparative Study of Laminar-Turbulent Displacement in an Eccentric Annulus under Imposed Flow Rate and Imposed Pressure Drop Conditions

This paper presents a series of experiments focused on the displacement of viscoplastic fluids by various Newtonian and non-Newtonian fluids from a long horizontal, eccentric annulus. The flow regimes range from high Reynolds number laminar regimes through to fully turbulent. These experiments represent the primary cementing operation in a horizontal well. The main objective of our experiments is to gain insight into the role of the flow regime in the fluid-fluid displacement flows of relevance to primary cementing. We study strongly eccentric annuli and displaced fluids with a significant yield stress, i.e., those scenarios where a mud channel is most likely to persist. For fully eccentric annuli, the displacements are uniformly poor, regardless of regime. This improves for an eccentricity of 0.7. However, at these large eccentricities that are typical of horizontal well cementing, the displacement is generally poor and involves a rapid “breakthrough” advance along the wide upper side of the annulus followed only by a much slower removal of the residual fluids. This dynamic renders contact time estimates meaningless. We conclude that some of the simple statements/preferences widely employed in industry do not necessarily apply for all design scenarios. Instead, a detailed study of the fluids involved and the specification of the operational constraints is needed to yield improved displacement quality.

CFD Analysis of Turbulent Flow of Power-Law Fluid in a Partially Blocked Eccentric Annulus

This study focuses on analyzing the turbulent flow of drilling fluid in inclined wells using the Computational Fluid Dynamics (CFD) technique. The analysis is performed considering an annulus with a fixed eccentricity of 90% and varying fluid properties, diameter ratio, and bed thickness to examine velocity profile, pressure loss, and overall wall and average bed shear stresses. CFD simulation results are compared with existing data for validation. The pressure loss predicted with CFD agrees with the data. After verification, predictions are used to establish a correlation that can be applied to compute bed shear stress. The established correlation mostly displays a discrepancy of up to 10% when compared with simulation data. The correlation can be used to optimize hole cleaning and manage downhole pressure.