Experimental measurement and thermodynamic modeling of methane hydrate phase equilibria in the presence of chloride salts

Abstract

The phase equilibria of hydrate are necessary to study the gas control/production from marine sediments. Considering the abundance of chloride salts in the ocean, the phase equilibrium conditions of CH4 hydrate in 3.5 wt% NaCl, KCl, CaCl2 and MgCl2 solutions were experimentally investigated at the temperature and pressure ranges of 281.9 K~287.1 K and 7.33 MPa~14.02 MPa, respectively. Then the reliability of the obtained data was validated by three thermodynamic consistency criteria. In addition, a new calculation model was proposed based on the Chen-Guo model and the Hu-Lee-Sum (HLS) correlation for hydrate prediction. And the prediction accuracy of the proposed model was described by the absolute average deviation of temperature (AADT). Results show that the inhibition effect of MgCl2 is stronger than that of other salts. Also, the experimental data obtained in this study can meet all the requirements of the criteria. Furthermore, the prediction results from the proposed model well agree with the experimental data. And the proposed model shows a good performance in predicting the phase equilibria of CH4 hydrate in the systems containing single chloride salt and mixed chloride salts with AADT of 0.54 K and 0.82 K, respectively.