Estudo da estabilidade de fluido de perfuração de base olefínica em diferentes condições de temperatura e tempo de envelhecimento

Abstract

A crucial aspect of the drilling process is the use of drilling fluid, which performs essential functions for the effective execution of this process. Under certain circumstances, the fluid may remain static under various conditions of temperature, pressure, and time, such as during maintenance, storage, and confinement conditions. However, these conditions can compromise its fundamental properties. Evaluating the impact of these different conditions on the fluid's properties is crucial to ensuring the safety and efficiency of drilling operations. This study aimed to conduct accelerated aging tests on an olefin-based fluid, formulated as an inverse emulsion, to evaluate its changes at high temperatures (up to 150 °C) and prolonged aging periods (up to 168 hours). For this purpose, specific equipment was developed to carry out these tests, including a low-speed mixer and an image acquisition device, which contributed to the study. The analyses covered rheology, density, stability, and filtrate volume of the fluid after aging. The results indicated that the developed equipment allowed for satisfactory aging tests. It was observed that the increase in temperature and aging time significantly impacted the rheological properties, reducing the yield stress and the power law index, while the consistency index and apparent viscosity increased considerably, with temperature being the most influential factor in all cases. Additionally, conditions such as 150 °C for 96 hours and 142.7 °C for 45 and 147 hours were sufficient to cause emulsion breakdown. The emulsion breakdown may be associated with the thermal degradation of the emulsifiers. The image acquisition device was able, in a satisfactory manner, to indicate that accelerated aging contributes to the separation of olefin from the emulsion more quickly than when not aged. Temperature and time also influenced the filtrate volume, with temperature reducing and time increasing this volume. It was also concluded that post-aging mixing significantly impacts the analyses, highlighting the importance of homogenization at low rotations and low shear for characterizing the emulsion's stability. Finally, the results demonstrated that certain conditions might lead to the need for replacement or adjustment of this fluid in real drilling cases.