CFD Analysis and Model Comparison of Annular Frictional Pressure Losses While Circulating Yield Power Law Fluids

Abstract

A computational fluid dynamics (CFD) analysis is conducted on the flow of Newtonian and non-Newtonian fluids in annuli including the effect of inner pipe rotation. A practical numerical model is proposed that accurately estimates the annular frictional pressure losses with and without the inner pipe rotation. Experiments are conducted at a 91 ft. long flow loop using various fluids that can be characterized as Yield Power Law (YPL). A commercial CFD software is used to validate the proposed numerical approach. A comprehensive comparison of the proposed model, CFD results, experimental results, the published experimental results and most widely used models from the literature is presented.The experimental setup simulates horizontal wellbore applications, which are increasingly prevalent due to recent shale plays. Today, since most drilling fluids show YPL behavior, YPL fluids with a wide range of rheological properties are used as test fluids in this study. The numerical model is coupled with a stability criterion that determines the onset and offset of the transitional flow between laminar and turbulent regions. The velocity profiles of a wide range of diameter ratios, Taylor and Reynolds numbers are presented. Various degrees of eccentricity are analyzed in terms of pressure profile and flow stability with the proposed method.The results from the experiments show significantly reduced pressure drops in fully eccentric annuli compared to concentric geometry. An increase in pressure loss is observed as the pipe is rotated while it is eccentric. The comparisons between the models indicate that the slot approximation can result in large errors especially when the diameter ratio is low. A 3D wellbore can be evaluated with grids using the proposed numerical method and the local stability criterion, which leads to accurate pressure loss estimations. Grid analysis can show the flow state profile and the pressure loss profile of a wellbore, which has potential to optimize operations in real-time or in the design phase.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.

Nonlinear dynamics of directional drilling with fluid and borehole interactions

“…By assumption, the elementary gyroscopic matrix is considered constant all along the drillstring. The fluid is pumped downward inside the pipe and upward in the annular space with the mean axial velocities U i and −U o respectively and is modelled with the Yield-Power-Law as in [30,29,34,35,36]. During the rotation, a constant force WOB=−10 5 N and a constant torque TOB=-5000 Nm are applied to the drill bit.…”

The Effects of Fluid Rheology and Drillstring Eccentricity on Drilling Hydraulics

“…If the hole is cased, then frictional pressure is not expected to be as high as when the well is open-hole. Open holes are noted with the presence of micro-doglegs and micro-tortuosities which increase the roughness of the hole and its frictional pressure [9]. The orientation of the pipe in the hole affects the flow pattern and hence its hydraulics in the well.…”

Pilot size process visualization: Gravity fluid displacement method to stop annular gas migration

“…Although, downscaling of any annulus into similar shapes seems realistic, concentric geometry lacks visualization. Non-circular hydraulic has been studied by researchers using equivalent diameter approach, which simply relates any flow geometry to flow pipe (Anifowoshe and Osisanya, 2012;Erge et al, 2014Erge et al, , 2015. However, the approach has not been used for buoyant settling studies.…”