Rheological models drilling fluids

A number of rheological models have been used to describe the rheology of drilling fluids (and non-Newtonian fluids in general) (8, 9, 65-67). These models, it is stressed, have been obtained purely empirically by fitting rasa function of y. A Newtonian fluid is characterized by... 

The results of the latest research into helical flow of viscoplastic fluids (media characterized by ultimate stress or yield point ) have been systematized and reported most comprehensively in a recent preprint by Z. P. Schulman, V. N. Zad-vornyh, A. I. Litvinov 15). The authors have obtained a closed system of equations independent of a specific type of rheological model of the viscoplastic medium. The equations are represented in a criterion form and permit the calculation of the required characteristics of the helical flow of a specific fluid. For example, calculations have been performed with respect to generalized Schulman s model16) which represents adequately the behavior of various paint compoditions, drilling fluids, pulps, food masses, cement and clay suspensions and a number of other non-Newtonian media characterized by both pseudoplastic and dilatant properties. 

Ayeni, K. Osisanya, S.O. Evaluation of Commonly Used Fluid Rheological Models Using Developed Drilling Hydraulic Simulator in Proc. 5th Canadian International Petroleum Conference, The Petroleum Society Calgary,... 

Figure 10. Pressure dependence of parameters from various models of the rheology of invert emulsion oil-based drilling fluids at various temperatures. Casson high shear viscosity Bingham plastic viscosity consistency, power law exponent, and yield stress from Herschel-Bulkley model. (Reproduced with permission from reference 69. Copyright 1986 Society of Petroleum Engineers.)...

Figure 13. Pressure dependence of the rheological parameters from the Herschel-Bulkley model (n, K, r0, and a high shear rate viscosity tjhb) for a weighted water-based drilling fluid at 40 °C. (Reproduced with permission from reference 72. Copyright 1988 Society of Petroleum Engineers.)...

The objectives of a drilling hydraulics programme are to ensure good hole cleaning, to minimize frictional losses in the flow in the drill pipe and annulus and to minimize the erosion of open hole formations by the shear stress exerted on the borehole wall. Several texts have described drilling fluid (or non-Newtonian fluid) hydraulics in some detail (82-85). The bulk flow properties of the drilling fluid are calculated from the models r = f(y) used to fit the experimental rheological data. 

Figure 2 7. Comparison of fit of power law, Bingham plastic and Robertson-Stiff rheological models to experimental data from bentonite drilling fluid. (Data from reference 106.)...

Beirute, R.M. and Flumerfelt, R.W., An Evaluation of the Robertson - Stiff Model Describing Rheological Properties of Drilling Fluids and Cement Slurries,... 

To predict the transport properties and performance of fiber sweeps under downhole conditions, the rheological properties of the base fluid and suspension must be understood. The proposed formulations for such fiber sweeps will be most effective when the rheology has been accurately modeled and fine-tuned for specific wellbore conditions. To begin to grasp how the fluid behaves, the relationship between shear stress and shear rate must be known. This is denoted as the shear viscosity profile, which is an aspect of the rheology of a fluid that is thought to control the hydrodynamics of flow. The most common shear viscosity models used in the oil and gas industry to characterize non-Newtonian drilling fluids include ... 

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