Drilling fluids plastic viscosity

These humic acids are not dissolved because the pH of this slurry is in the range of 4 to 9. Small amounts of fulvic acids are formed, and these are soluble in the water of the slurry. The coal-derived humic acids find applications as drilling fluid dispersants and viscosity control agents, whereas the coal-derived fulvic acids may be used to produce plasticizers and petrochemicals. 

In addition to the plastic viscosity and yield point, the gel strength of the drilling fluid is measured after it has been at rest for a given period of time. The usual procedure (64) is to shear the sample and then allow the sample to be unsheared for 10 s or 10 min. After the prescribed... 

Figure 7. Determination of yield point and plastic viscosity of drilling fluid using the Bingham plastic fluid model.

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.)...

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