Frequency analysis to determine the pressure wave velocity in slug flow

Transient flow frequently occurs in petroleum operations, causing the propagation of flow properties as a wave throughout the pipe. The propagation of these waves can cause equipment failures such as separator flooding, high backpressure, and pipeline vibration that could lead to leakage. Knowing the pressure propagation features is essential to designing and managing these systems. The two-fluid model has been employed recently to predict the pressure wave velocity. However, this model needs the oscillation frequency as an input parameter, which analysis was previously neglected. This work presents three approaches to obtain the frequency parameter: frequency correlations, analysis of experimental pressure signals of Maria and Rosa (2016) in horizontal and of Toledo and Mazza (2023) in vertical orientation using the Discrete Fourier Transform (DFT) and slug tracking simulations. Using the two-fluid model, the proposed method to determine the oscillation frequency proved appropriate for capturing the pressure wave propagation velocity in slug flow. The predicted pressure wave velocity was compared to Maria and Rosa's (2016) with a maximum deviation of less than 30% for all tests of their database. The mean deviation was 17%.