| dc.description.abstract | Drilling fluids are visco-elastic materials. This means that they behave as a viscous fluid when subject to sufficient shear stress and like an elastic solid when they are in near static conditions. Both properties are time-dependent.
While drilling a well, there could be many instances when a change in the velocity of drilling fluid is required. For instance, we may have to adjust the pump flow rate depending upon the formation drilled. In a similar manner, there could be variations in the flow rate due to the movement of the drill string as it can move axially, rotationally, and side-wise. Another example is the change of flow rate owing to the difference in the flow geometry while passing from the annulus. In all these cases, the drilling fluid required a definite time to attain new equilibrium conditions.
Nevertheless, the time-dependence rheological properties of drilling fluids are usually not measured during drilling operations. Additionally, in the lab measurements, seldom are experiments performed beyond 30 minutes of resting time. Consequently, it is difficult to estimate how thixotropy impacts pressure losses in drilling operations. Against this backdrop, our research is focused on the analysis of the gelling properties of time-dependent non-Newtonian fluids.
We have systematically measured the time-dependence of the rheological properties of different samples of water-based and oil-based fluids with a scientific rheometer in order to capture how the gel strength of the drilling fluids responds to variations of other relevant parameters involved. Furthermore, we have analyzed the behaviours of those fluids for the longer resting times until no further gel strength is developed in them. | |
