Linear and non-linear rheological behaviour of cement and silica suspensions. Effect of polymer addition |
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Authors: | Alice Chougnet Annie Audibert Michel Moan |
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Institution: | (1) Schlumberger Oilfield Services, 49377 Vechta, Germany;(2) Total SA 3 Place de la Coupóle, 92078 La Défense, France;(3) Laboratoire de Rhéologie, Université de Bretagne Occidentale, Brest, France |
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Abstract: | Oil well cement pastes and model silica suspensions demonstrate similar rheology: in oscillatory shear, beyond a critical
stress, a sharp transition is ob- served between gel and liquid behaviour. In creep tests, an apparent yield stress and shear-thinning
are followed by the appearance of shear thickening. The minimum viscosity measured in steady shear is close in value to the
complex viscosity obtained from oscillatory measurements. The observations can be explained by the formation of liquid trapping
aggregates whose compactness may be estimated by fitting the Tsenoglou model, and whose cohesion is reflected in the rigidity
of the gel and in the critical strain (or stress) of gel dissolution. Substituting cement or silica particles by polymer redispersible
powder causes a decrease of the storage modulus in the gel state and a lower viscosity, while leaving the general features
of the flow curve unchanged. Decrease in material rigidity may be due to a weaker inter-particle attraction generated by the
polymer presence. The decrease in viscosity is explained by a lessening of water entrapped within the aggregates, which now
contain polymer particles which are less hydrophilic than either cement or silica. |
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Keywords: | Cement Polymer Rheology |
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