Yield-power law model more accurately predicts mud rheology
ABSTRACT The yield-power law rheological model can calculate yield point much more accurately than that calculated by the Bingham plastic model. The yield-power law (Herschel-Bulkley) model offers many advantages over the Bingham plastic and power law models because it more accurately characterizes mud behavior across the entire shear rate range. The yield-power law model has not found widespread use in the oil field because of the lack of simple analytical solutions for viscometric and hydraulics calculations. These concerns are no longer pertinent, however, because of the rapid spread of personal computers in the field and recent developments in using this model. The paper describes yield stress, the Bingham plastic model, the power law model, the yield-power law model, calculation method, model comparison, mixed metal hydroxide drilling fluids, mud hydraulics, and results from applying the model to these drilling muds.
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ABSTRACT: An integrated approach is presented for the flow of Herschel–Bulkley fluids in a concentric annulus, modelled as a slot, covering the full range of flow types, laminar, transitional, and turbulent flows. Prior analytical solutions for laminar flow are utilized. Turbulent flow solutions are developed using the Metzner–Reed Reynolds number after determining the local power law parameters as functions of flow geometry and the Herschel–Bulkley rheological parameters. The friction factor is estimated by modifying the pipe flow equation. Transitional flow is solved introducing transitional Reynolds numbers which are functions of the local power law index. Thus, an integrated, complete and consistent set, combining analytical, semi-analytical and empirical equations, is provided which describe fully the flow of Herschel–Bulkley fluids in concentric annuli, modelled as a slot. The comparison with experimental and simulator data from various sources shows very good agreement over the entire range of flow types.On présente une méthode intégrée pour l'écoulement des fluides d'Herschel–Bulkley dans un espace annulaire concentrique représenté par une fente, couvrant la gamme complète des types d'écoulement, à savoir laminaire, en transition et turbulent. Des solutions analytiques antérieures sont utilisées pour l'écoulement laminaire. Des solutions d'écoulement turbulent sont élaborées à l'aide du nombre de Reynolds de Metzner–Reed après avoir déterminé les paramètres de loi de puissance locaux en fonction de la géométrie de l'écoulement et des paramètres rhéologiques d'Herschel–Bulkley. Le facteur de friction est estimé en modifiant l'équation d'écoulement dans un tube. L'écoulement en transition est résolu en introduisant les nombres de Reynolds exprimés en fonction de l'indice de loi de puissance local. Ainsi, un ensemble intégré, complet et consistant, combinant des équations analytiques, semi-analytiques et empiriques, est fourni, qui décrit entièrement l'écoulement des fluides d'Herschel–Bulkley dans des espaces annulaires concentriques représentés par des fentes. La comparaison avec les données expérimentales et les données de simulateurs de diverses sources montre un très bon accord pour la gamme complète des types d'écoulement.The Canadian Journal of Chemical Engineering 07/2008; 86(4):676 - 683. · 1.00 Impact Factor
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ABSTRACT: The rheological properties of a drilling fluid directly affect flow characteristics and hydraulic performance. Drilling fluids containing bentonite mixtures exhibit non-Newtonian rheological behavior which can be described with a high degree of accuracy by the three-parameter Herschel-Bulkley (HB) model. To determine the HB parameters, standard statistical techniques, such as the non-linear regression (NL) method are routinely used. However, sometimes they provide non physically acceptable solutions which could produce wrong values of the significant hydraulic parameters which affect drilling operations. To obtain more accurate results, the Golden Section (GS) method was subsequently developed by Kelessidis et al. (2006). In this work a different technique was developed using the Genetic Algorithms (GAs) to provide an easy-to-use tool in order to determine the three parameters of the Herschel-Bulkley model more accurately. To evaluate the accuracy of the GAs method, experimental viscometric data sets of drilling fluids were taken from the literature and the results were compared with the ones obtained by using the NL and GS techniques. The results show that the GAs and the GS methods provide similar results with very high correlation coefficients and small sum of square errors for most of the samples exhibiting negative yield stress values by the NL technique, while giving similar to the NL technique for the samples that were predicted with positive yield stress. However, in some cases, the GAs method gives better and more realistic results than the GS method.Korea-Australia rheology journal 09/2012; 24(3). · 1.02 Impact Factor
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ABSTRACT: A literature review is presented that identifies a number of areas where procedures for the engineering design of bored installations in soil using horizontal directional drilling HDD can be improved through a more realistic consideration of drilling fluid drag effects and skin friction coefficients. The current HDD practice of calculating annular frictional pressure loss caused by drilling fluid drag based on the assumption of concentric annular flow of a Bingham plastic fluid is demonstrated to be overly conservative. Conse-quently, critical design parameters, such as depth of cover, which affects crossing length, and drilling equipment size, which is selected based on anticipated pulling load, cannot be optimized. This can result in overly conservative design and unnecessary construction costs. Parameter values currently employed in HDD pulling load prediction are challenged suggesting that the viscous shear of drilling fluid is significantly less than typically quoted and that the friction coefficients often employed are not representative of all skin friction effects in HDD. A new real-time monitoring cell for large-scale HDD is described that can be used to optimize installations and to assess and update current prediction models.International Journal of Geomechanics. 01/2005; 5(4).