Estudo experimental e numérico do comportamento reológico de um fluido de perfuração

Abstract

The rheology of drilling fluids is important to ensure the hydraulic and structural effectiveness of well drilling. Maintenance of mud properties involves routine viscosimetric measurement by an engineer at the site using equipment that quantifies shear normally under the atmosphere mild conditions and therefore is not representative of the conditions facing the drilling fluid at the bottom of the well. Some researchers have focused on the use of hydraulic equations to measure the rheological behavior of fluids from pressure drop data with varying degrees of success and limitation. The recent introduction of sensors in the drill columns allowed the expansion of pressure data at different depths thus favoring the technique. Technology and mathematical fundamentals, however, still face several challenges that will require more time and dedication from researchers. In this context, computational fluid dynamics (CFD) can help with faster and less expensive tests and studies, acting as a fundamental ally of researchers. In this work a drilling fluid was designed in laboratory and rheological studies were carried out for viscosimetric characterization. With the parameters obtained in laboratory, a numerical model of finite volume was elaborated in Ansys® to study the fluid dynamics in five different depths (represented by different annular, pressures and temperatures) and to calculate the pressure drops for different flow rates allowing the creation of curves of the flow of non-Newtonian fluid, while simultaneously allow the study of fluid dynamics in annular region, finding good representation with the analytical equations of fluid mechanics. The adopted approach in this work focuses on numerically evaluate rheological parameters of a yield power law (YPL, Herschel-Bulkley) fluid through records of viscous pressure drops at diferente flow rates. This new approach represents a significant advance towards full automation of the monitoring of drilling fluid properties even within kilometers of depth, thereby eliminating the limitation of few rheological measurements carried out under mild surface conditions that do not represent actual conditions of the drilling well.