BUBBLE POINT DETERMINATION OF SQUALANE AND OIL SAMPLES WITH CO₂: TEMPERATURE AS A PHASE TRANSITION INDICATOR

The combination of extreme pressure and temperature conditions with elevated carbon dioxide (CO₂) levels in pre-salt reservoirs presents substantial challenges for effective resource exploitation. This study aims to evaluate temperature variation as an indicator of phase transition. To achieve this goal, high-pressure bubble point equilibrium experiments were conducted using two non-visual synthetic methods. Experiments were performed on three CO₂-containing systems: squalane, light crude oil, and condensate gas. Five CO₂ concentrations were analyzed over a temperature range of 30 to 120 °C. A temperature drop of up to 1.2 °C was observed at the onset of the first vapor bubble, indicating an endothermic phase transition. Experiments with translucent synthetic samples, where the bubble point was determined visually through a sapphire window, confirmed that the non-visual method based on temperature variation is accurate. Furthermore, the proposed temperature-based method demonstrated performance comparable to the well-established volumetric method. Therefore, temperature variation can serve as a reliable monitoring parameter for bubble point equilibrium experiments, particularly in non-translucent samples such as petroleum.