Abstract Drilling an oil well involves using drilling fluids that perform cleaning and cooling functions, but that most importantly maintain the fluids of the geological formation contained by hydraulic pressure. A fundamental role in predicting the hydraulic pressure of the well consists of monitoring the fluid’s rheological behavior. This paper summarizes an ongoing effort to measure, by evaluating the performance of two online viscometers, drilling fluids’ rheological behavior in real time. One online method proposes a modified Couette system. The other consists of a standard pipe viscometer with default modeling. The performances of the online devices were compared with an offline method - a Couette device commonly used in oilfields as a benchmark. For Newtonian fluids, agreement between the rheological behaviors was found for all instruments, validating the methodology proposed. For non-Newtonian fluids, there were divergences, which were investigated and their probable causes determined to be the following: homogeneity, slippage effects, and interaction in the fluid/gap interfaces. A case study demonstrated that these divergences were not significant during the prediction of hydraulic pressure, meaning that the methodology proposed has the potential to improve overall drilling performance.

The procedure usually employed for specifying a set of hydrocyclones used in Newtonian fluid-solid separation processes can be extended to the case of non-Newtonian fluids. The apparent viscosity, µapp, is the link between the two cases, and can be evaluated from the knowledge of the shear stress function, S, and the characteristic rate of shear, λ*. In order to verify the validity of this, experiments using suspensions of different solids in an aqueous solution of carboxymethylcellulose (CMC), with pseudoplastic behavior, in an AKW commercial hydrocyclone have been performed. The results obtained in this work indicated that the separation process and the pressure drop in the hydrocyclone cannot be characterized by a single apparent viscosity associated parameter.