Yield-power law model more accurately predicts mud rheology. Oil Gas J

Oil and Gas Journal; (United States) 08/1993; 91:34(34).


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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    • "In conventional drilling, drilling fluids are modelled with classical rheological models like Bingham plastic or power law model and fluid behaviour is defined with only two points of the rheological relation (R600 and R300). With increased use of polymer-based fluids as drilling fluids, the power law rheological model receives great attentions because it describes the behaviour of these fluids better than the Bingham plastic model[17]. The power law model can be expressed by: "

    Full-text · Article · Jan 2016
    • "Most drilling fluids used today show highly nonNewtonian fluid behavior, which can be characterized using the yield power law (YPL). YPL fluid model better describes the fluid at low and high shear rates than the Bingham plastic or power law models [1]. In the literature, an increased focus on YPL fluids can be observed, but there is limited research conducted on the flow of YPL fluids through annuli with buckled and rotating drillstrings. "
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    ABSTRACT: An analysis of laminar to turbulent transition of yield power law (YPL) fluids in concentric and eccentric annuli is presented. Both theoretical and experimental approaches are followed to better understand the onset of transitional flow.The objective of this study is to investigate the stability of the flow in concentric and eccentric annuli. Theoretical analysis of the inner and outer shear regions, to clarify the earlier transition observed with experimental studies, are within the scope of this study.A stability criterion based on the ratio of turbulent energy production and rate of work done by viscous stresses is used to determine the end of laminar flow. Experiments are conducted for laminar, transition and turbulent regions of flow in a fully eccentric annulus. Eight distinct YPL fluids are tested and the results are compared with a proposed model and models available in the literature.The proposed stability parameter shows an earlier transition near the outer wall for a wide range of non-Newtonian fluids, which is in agreement with measurements in the literature. The proposed modification is extended to eccentric annuli and showed good agreement with experiments. To the authors' knowledge, this is the first theoretical study to locally predict the onset of transition in eccentric annuli of YPL fluids.Transition from laminar to turbulent significantly depends on eccentricity, diameter ratio and fluid properties, especially to the shear thinning ability of a fluid. The proposed modification allows a fair prediction of the transition from laminar to turbulent regions in eccentric annuli. With the proposed approach, the percentage of laminar and non-laminar regions for a cross section of an eccentric annulus can be predicted.
    No preview · Article · Feb 2015 · Journal of Petroleum Science and Engineering
    • "These fluids can be characterized as YPL. YPL fluid model better describes the fluid at low and high shear rates than the Bingham Plastic or Power Law models (Bern et al. 2007; Friedheim and Conn 1996; Hemphill et al, 1993). Yield stress of the drilling fluid suspends the cuttings and shear thinning ability enables lower pressure losses at the high flow rates. "
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    ABSTRACT: An experimental study followed by comprehensive flow modeling is presented. The experiments were conducted on a horizontal well setup with drillstring under compression, considering the influence of rotation on frictional pressure losses of Yield Power Law (YPL) fluids. Flow through various buckling configurations with and without drillstring rotation was investigated. A new correlation is presented for the transition from laminar to turbulent regions in concentric and eccentric annuli. A broad model of flow of YPL fluids is proposed for concentric, eccentric and buckled configurations. The model includes the effects of rotation in laminar, transitional and turbulent flow. A 91 ft. inner pipe was rotated while applying axial compression during flow. At the no-compression case, eccentricity of the inner pipe is varied as the drillstring rotated. The aim for such a design was to simulate actual drilling operations. The test matrix involves flow through sinusoidal, transitional and helically-buckled drillstring. The effect of pitch length is investigated. Helical modes with two different pitch lengths were tested. Eight distinct YPL fluids were used to examine the dependence of pressure losses on fluid parameters. In the theoretical part, a stability criterion is modified to determine the onset of transitional flow of YPL fluids and a correlation is proposed for practical purposes. In addition, pressure loss prediction models are presented for the flow of YPL fluids through concentric, eccentric, free and buckled configurations of the drillstring, with and without rotation. The proposed models are compared with data from the literature and the experiments. It has been observed that increasing eccentricity and rotation causes an earlier transition from laminar to turbulent flow. Increasing eccentricity decreases pressure losses. In addition, the buckled configurations show a further decrease in frictional pressure losses as the compression increases. In the helical mode, decreasing the pitch length results in a decrease in pressure losses. Rotation tests with free drillstring show an increase in pressure losses as the rotary speed of the drillstring increases. Also, rotating the drillstring while it is compressed suggests an elevated increase in pressure losses due to amplified vigorous motion of the drillstring. Distinct differences in the effects of buckling and rotation are observed in laminar, transitional and turbulent flow. The greatest differences are found in the transition region. Flow of YPL fluids is one of the greatest challenges in the modern drilling industry. Studies that correspond to actual drilling conditions are substantially important in reducing these challenges. The information obtained from this study can be used to improve the control of bottomhole pressure during extended reach (ERD), horizontal, managed pressure (MPD), offshore and slim hole drilling applications. Consequently, this theoretical and experimental research has the potential to lead to safer, deeper and more precisely controlled oil/gas well drilling operations.
    No preview · Article · Mar 2014 · SPE Drilling & Completion
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