Dew point of the methane-ethanol system: Data via acoustic technique and modeling via CPA EoS

Abstract

The use of gas-lift systems for chemical injection presents a smart solution in numerous cases, particularly when production wells are already equipped with such systems. However, ensuring optimal operating conditions demands a thorough understanding of the phase equilibria curves of natural gas - inhibitor mixtures. The primary objective of this study is to experimentally determine the dew point curve of the methane - ethanol mixture, with methane being a significant constituent of natural gases, and ethanol being one of the most widely utilized gas hydrate inhibitors. The experiments covered temperatures within the range of 313.15–353.15 K and pressures ranging from 1.2 MPa to 8.5 MPa. Both visual and acoustic techniques were applied as synthetic methods to obtain accurate data. Additionally, a thermodynamic model employing the Cubic-Plus-Association (CPA) equation of state, fine-tuned with the experimental bubble and dew point data, was utilized to establish the dew point curve under optimized conditions. An average absolute relative deviation of 4.4% was obtained between the experimental dew points obtained in this work and the thermodynamic model. Moreover, this study fills a noticeable gap in the literature by providing reliable experimental data, which had been scarce. Furthermore, the acoustic experimental technique showcased in this work presents a feasible option for determining dew points. By gaining deeper insights into the behavior of the methane - ethanol mixture, this research contributes to the enhancement of gas-lift systems' efficiency and reliability in chemical injection applications. The findings are expected to have a positive impact on flow assurance strategies and ensure safer and more efficient operations in oil and gas production.