We experimentally studied the viscous fingering instability considering a Newtonian oil displacing viscoelastic shear-thinning liquids and vice versa. The non-Newtonian liquids are aqueous solutions of polyacrylamide and xanthan gum, i.e., flexible and rigid polymers, respectively. A rectangular Hele-Shaw cell, connected by two plenum chambers, was developed to evaluate the displacement of a fixed volume. The experiment consists of analyzing the interface time evolution through a digital camera as a function of the geometric, dynamic, and rheological parameters. The displacement efficiency was determined through image processing in order to identify the formation of fingers or plugs. Unlike the Newtonian case, the transition does not occur when the viscosity ratio is roughly equal to one, but nevertheless, it was observed that the stability of the interface depends on the viscosity ratio. Specifically, more branches are observed at low viscosity ratios. Furthermore, a higher stability is observed when the Newtonian liquid displaces the shear thinning liquid, especially when the polymer is more rigid. When the Newtonian liquid is being displaced, elastic effects favor the displacing efficiency.

The cement plug placement operations are represented by buoyancy-driven exchange flows between two yield stress materials. It is an unstable situation since cement slurries are usually denser than drilling fluids and consequently their positions tend to invert. To better understand this phenomenon, experimental and numerical analysis were performed considering a denser liquid

Inorganic scale formation in oil wells is a major flow assurance challenge, causing production losses, increased intervention costs and reduced operational efficiency. In Brazil, recent discoveries in pre-salt reservoirs have increased the relevance of calcium carbonate (CaCO₃) scaling under high-pressure and high-temperature (HPHT) conditions. Experimental data representative of petroleum environments under such conditions, particularly regarding the influence of CO₂ and flow conditions, remain limited. In this study, a compact pressurized experimental unit was designed and constructed to investigate the dynamic formation, deposition and adhesion of CaCO₃ under conditions close to those encountered in oil production systems. A dedicated experimental methodology was developed to promote controlled mixing of aqueous sodium bicarbonate (NaHCO₃) and calcium chloride (CaCl₂) solutions and CO₂ injection, enabling precise control of pressure, temperature and flow regime. The effects of turbulent flow, expressed by different Reynolds numbers, on the deposited CaCO₃ mass and its adhesion to the substrate were systematically evaluated under controlled conditions of 40 °C and a pressure drop of 15 bar was imposed in the control valve in order to promote the flash of CO₂ and CaCO₃ precipitation. Complementary characterization analyses were performed to assess crystal morphology and adhesion detachment strength. The results provide new experimental insights into CaCO₃ scaling mechanisms under CO₂-rich flowing conditions, contributing to improved understanding of scale adhesion and the development of mitigation strategies for flow assurance in oil and gas operations.

The extraction of oil results in problems such as the scale formation in the various stages of the production process. The scale reduces all or part of the flow conduits, increasing the pressure drop and reducing oil production. In this work the three dimensional, transient, turbulent, biphasic problem is solved by combining the Dense Discrete Phase Model (DDPM) and Discrete Element Method (DEM), to analyze the influence of certain parameters on the particle deposition, which represents the calcium carbonate scale formation, inside the wall of a horizontal pipeline at well conditions. The obtained results show that particle deposition is higher at lower Reynolds numbers. The results also show that the use of DEM model is more representative, but due to the high computational effort required, it application in complex geometries must be carefully evaluated.