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ON THE SCALE-UP AND POWER CONSUMPTION REQUIREMENTS IN THE MIXING OF CEMENTITIOUS FLUIDS – A THEORETICAL CONSIDERATION

IP.com Disclosure Number: IPCOM000234015D
Publication Date: 2014-Jan-07
Document File: 12 page(s) / 82K

Publishing Venue

The IP.com Prior Art Database

Abstract

As the complexity of fluids used during well cementing operations increases, one challenge is correlating and/or scaling from laboratory mixing of cement slurries to field mixing using large-scale field mixers. In some cases, cement slurries mix with ease in the laboratory but pose challenges when mixed using field equipment. Some of the reasons for the discrepancy between the laboratory and the field mixing are due to, but not limited to, an inadequate comprehension of power requirements for mixing of cement slurries in the laboratory, a lack of cognizance of scale-up criteria for cement blending from laboratory to field blenders, and a lack of general rheological understanding of cement slurries. The work described here is a first attempt at a theoretical consideration of the deviation in scale-effects between laboratory and field mixing. This work highlights an extension of classical chemical stirred reactor theory to the Generalized Herschel-Bulkley non-Newtonian fluid, to aid in a predictive tool for evaluation of the power consumption requirements for mixing cement slurries at multiple scales of operation. Such a method would be expected to allow for quick order-of-magnitude analysis of power consumption requirements for efficient mixing of cementitious fluids both in the laboratory and with field mixing equipment. This will also help alleviate cement mixing issues that are highly cost-prohibitive.

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ON THE SCALE-UP AND POWER CONSUMPTION REQUIREMENTS IN THE MIXING OF CEMENTITIOUS FLUIDS - A THEORETICAL CONSIDERATION

Keywords: Cement Mixability, Power Consumption, Scale-Up, Power Number

Abstract

As the complexity of fluids used during well cementing operations increases, one challenge is correlating and/or scaling from laboratory mixing of cement slurries to field mixing using large- scale field mixers. In some cases, cement slurries mix with ease in the laboratory but pose challenges when mixed using field equipment. Some of the reasons for the discrepancy between the laboratory and the field mixing are due to, but not limited to, an inadequate comprehension of power requirements for mixing of cement slurries in the laboratory, a lack of cognizance of scale-up criteria for cement blending from laboratory to field blenders, and a lack of general rheological understanding of cement slurries.

The work described here is a first attempt at a theoretical consideration of the deviation in scale- effects between laboratory and field mixing. This work highlights an extension of classical chemical stirred reactor theory to the Generalized Herschel-Bulkley non-Newtonian fluid, to aid in a predictive tool for evaluation of the power consumption requirements for mixing cement slurries at multiple scales of operation. Such a method would be expected to allow for quick order-of-magnitude analysis of power consumption requirements for efficient mixing of cementitious fluids both in the laboratory and with field mixing equipment. This will also help alleviate cement mixing issues that are highly cost-prohibitive.


1.INTRODUCTION

In an oft-cited publication (Metznerand Otto, 1950), it was highlighted that a consideration of the viscous energy dissipation in the flow of fluid around a mixing impeller must necessarily entail a quantitative description of the magnitudes of the shearing stresses and shearing strain rates. This is relevant since viscous energy dissipation can be considered to be the dominant mechanism of producing a homogenous (well-mixed) suspension, just as in the case of producing a homogenous cement slurry. In the region of the impeller blades the flow is complex, but the viscous energy dissipation is the result of the drag forces on the impeller blades. These drag forces arise due to (a) surface shearing forces and (b) pressure differences in front of and behind the blade (Metzner and Otto, 1950). Since the impeller blade of the Waring® blender used for laboratory mixing of cement slurries has an associated pitch and thickness to the blade, the surface shearing forces can be considered to also contribute to the total drag force. Further, the viscous energy dissipation is important from the stand-point of dictating the torque that the impeller experiences, and hence the power consumption requirements for mixing. Hence consideration of the viscous energy dissipation, and hence the power consumption requirements for mixing, wo...