Experimental Phase Equilibria of Carbon Dioxide and Methane Hydrates in the Presence of 2-Propanol and Sodium Chloride

Abstract

In oil exploration and production, 2-propanol is a chemical often used during stimulation and to improve workover operating conditions. It is investigated as a potential thermodynamic inhibitor of hydrate formation, and its use would be advantageous from an economic standpoint. However, some reports point out that 2-propanol can promote hydrate formation, especially in systems with either CH4 or CO2 acting as auxiliary gas. New experimental data for phase equilibrium of inhibited carbon dioxide and methane hydrates were obtained by the isochoric experimental method in a high-pressure cell, for pressures between 20 and 260 bar, at concentrations ranging from 5 to 25 wt % of 2-propanol. New experimental data on mixtures of 2-propanol and NaCl (at a fixed concentration of 5 wt %) were also obtained in order to evaluate the behavior of this alcohol in saline mixtures. 2-Propanol was included in an in-house software previously developed. The thermodynamic model is based upon the cubic plus association (CPA) equation of state for the fluid phases and a statistical approach based on van der Waals–Platteeuw theory for the hydrate phase. Based on the results obtained in this work, it was observed that 2-propanol has a hybrid behavior, highly dependent on the gas system composition. For CO2 systems, 2-propanol has been characterized as a CO2 hydrate inhibitor and a CH4 hydrate promoter, collaborating on the structural transition from the sI type to the sII type. The inhibiting effect of 2-propanol on carbon dioxide hydrate systems was not compromised. Software deviations did not exceed AAD = 17%, for both systems, bringing reliability of the model and optimized parameters. In salt mixtures, 2-propanol is a thermodynamic inhibitor for both gases, and at concentrations higher than 10 wt %, 2-propanol had a satisfactory inhibition effect.

Predicting Phase Equilibria of CO2 Hydrate in Complex Systems Containing Salts and Organic Inhibitors for CO2 Storage: A Machine Learning Approach

“…In this study, ML models were developed to accurately predict the phase equilibria of the CO 2 hydrate, particularly in systems containing thermodynamic inhibitors. To construct these models, a comprehensive data set comprising 1801 experimentally measured data points was compiled from 85 references − . This dataset covered not only pure CO 2 hydrate but also systems incorporating 14 different types of salts (NaCl, KCl, CaCl 2 , MgCl 2 , NaBr, KBr, CaBr 2 , NaF, Na 2 SO 4 , MgSO 4 , NaHCO 3 , SrCl 2 , HCOONa, and HCOOK) and 9 organic inhibitors: methanol (MeOH), ethanol (EtOH), ethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG), glycerol, 1-propanol, 2-propanol, and tetrabutyl alcohol (TBA).…”

Phase Equilibria of Zinc Oxide (ZnO) Nanoparticles and Tetrahydrofuran (THF) in CO2 Hydrate Systems: Individual and Combined Analyses

“…A method of measuring the phase equilibrium of gas hydrates of interest has been developed using the isochoric pressure search method, − following the steps introduced first by Ohmura et al These experiments involve increasing temperature step by step following the crystallization of the gas hydrate. In order to reach phase equilibrium at each stage, it is necessary to maintain the temperature for a sufficient period of time with adequate mixing.…”