Rheology
1. With reference to ‘shear stress’ of drilling fluid, when the material deformation occurs by relative deformation of ‘n’ number of fictious layers - upon applying a horizontal force to the upper plate, while the bottom plate remains fixed; would it remain feasible to validate experimentally that the velocity remains to be ‘the maximum’ at the topmost layer, while the velocity remains to be ‘zero’ at the bottommost layer, when the total deformation occurs in a constant time interval?
If the drilling fluid does not entertain a relatively simple shear and laminar flow, then, how come the force on the upper plate would enforce a constant speed; and in turn, how would it cause the different drilling mud layers to transfer a ‘definite’ part of the induced frictional force?
2. Unlike solid materials, as the stress response of drilling mud tend to keep flowing beyond the time interval of shear application, it necessitates the consideration of a few consecutive time intervals. If so, would it remain feasible to dissect the ‘shear strain rate’ into its components through ‘horizontal velocity’ (v) and the ‘width’ (y) (in which the drilling remains contained between the plates) @ laboratory-scale?
3. Whether the ‘flow curve’ of drilling fluids does not constitute the “microscopic” measurement of both shear stress and shear rate?
4. Whether the ‘workability loss’ (the permanent changes in rheological properties with time) and ‘pure thixotropy’ (fully reversible changes) associated with a drilling mud would remain influenced as a function of reservoir temperature and pressure?
5. How easy would it remain to measure ‘time-dependent flocculation’ or ‘network structuring’ associated with the investigation of micromechanical mechanisms at drilling fluid particle level @ laboratory-scale towards the measurement of yield stress and viscosity?
Or
Do we require to load a new sample into the rheometer for every time step of interest in order to describe a time evolution?
6. Under what circumstances, a strain oscillation with a definite frequency and amplitude needs to be applied to a drilling fluid while measuring the stress response towards distinguishing viscous from elastic effects?
7. At the laboratory-scale, does the elastic modulus (or storage modulus) really indicate all the micro-structural effects of drilling fluids that are in phase with the strain (i.e., elastic effects); while, the viscous modulus (or loss modulus) really represent all the effects of drilling fluids that occur in phase with the strain rate (i.e., viscous effects)?
8. How exactly to get rid off the effect of time-dependent rigidification or solidification of drilling fluids while quantifying the structural build-up of drilling fluids under all kinds of reservoir pressure and temperature?
Whether the details on the evolution of elastic modulus would remain sufficient?
9. Whether the drilling fluids are really designed to change the properties of the suspending medium, the interaction forces between particles; and also, to change the rate at which the chemical reactions need to take place?
10. In the context of drilling fluids, when do we require the necessity of the distinction between ‘dynamic yield stress’ (self-supporting stress when a dynamic system comes to rest) and ‘static yield stress’ (a system at rest is put into motion, which eventually result in stresses deviating from linear behavior, while reaching a peak stress)?
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