Methane hydrate phase equilibrium in the presence of NaBr, KBr, CaBr 2 , K 2 CO 3 , and MgCl 2 aqueous solutions: Experimental measurements and predictions of dissociation conditions Amir H. Mohammadi a , Ilyas Kraouti b , Dominique Richon a, * a Mines ParisTech, CEP/TEP – Centre énergétique et procédés, CNRS FRE 2861, 35 Rue Saint Honoré, 77305 Fontainebleau, France b Département Mesures Physiques, Institut Universitaire de Technologie, Université de Paris-Sud (XI), Plateau de Moulon, 91400 Orsay, France article info Article history: Received 3 July 2008 Received in revised form 12 January 2009 Accepted 16 January 2009 Available online 27 January 2009 Keywords: Gas hydrate Methane NaBr, KBr, CaBr 2 ,K 2 CO 3 , and MgCl 2 Experimental data Prediction abstract In this communication, experimental data for dissociation conditions of methane hydrates in the pres- ence of 0.05 and 0.1 mass fractions NaBr, KBr, K 2 CO 3 , and MgCl 2 aqueous solutions and in the presence of 0.05 and 0.15 mass fractions CaBr 2 aqueous solutions are reported. The experimental data were gen- erated using an isochoric pressure-search method. The new experimental dissociation data for methane hydrates in the presence of 0.1 mass fraction MgCl 2 aqueous solution are compared with some selected experimental data from the literature and the agreements are generally found acceptable. Some of new data are finally compared with the predictions of a correlation, which is generally used in the absence of experimental data, and acceptable agreements between the experimental and predicted data are observed. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Gas hydrates are solid ice-like compounds formed through a combination of water and suitably sized guest molecules under low temperatures and elevated pressures commonly occur in petroleum industry [1–3]. The formation of gas hydrates can cause equipment blockage, operational problems, and safety concerns in hydrocarbon production, transportation, and processing [1–3]. For pipelines carrying a cocktail of multiphase fluids including petro- leum fluids and formation water with various concentrations of salts, saline water may provide the required gas hydrate formation inhibition [1]. On the other hand, addition of some specific salts in drilling muds can inhibit formation of gas hydrates in drilling oper- ations [1]. Reliable experimental data for gas hydrate phase equi- librium in the presence/absence of salt aqueous solutions are therefore necessary to avoid formation of gas hydrates. Although many experimental data have been reported for phase equilibria of gas hydrates in the presence of NaCl, KCl, and CaCl 2 aqueous solutions [1,3], information for gas hydrates phase equilibria in the presence of other salts aqueous solutions is limited [1]. In this work, we report experimental dissociation data for methane hydrates in the presence of NaBr, KBr, CaBr 2 ,K 2 CO 3 , and MgCl 2 aqueous solutions, which have been measured based on our previous experimental work [2,3] that takes advantage of an isochoric pressure-search method [4]. Table 1 summarizes the experiments carried out in terms of type of salt, salt concentration in the aqueous solution, and dissociation temperature ranges. The experimental data on dissociation conditions of methane hydrates in the presence of 0.1 mass fraction MgCl 2 aqueous solution are successfully compared with some selected experimental data from the literature [5], which demonstrates the reliability of the exper- imental technique and the new experimental data reported in this work. Some of experimental dissociation data are finally compared with the predictions of a general correlation [6] and acceptable agreements between the experimental and the predicted data are generally found. 2. Experimental section Purities and suppliers of materials are provided in table 2.A description of the experimental setup used in this study is given elsewhere [2,3]. Briefly, the main part of the apparatus is a cylin- drical vessel, which can withstand pressures higher than 40 MPa. The vessel has a volume of 57.5 cm 3 with two sapphire windows. A magnetic stirrer ensures sufficient agitation to facilitate reaching equilibrium. The vessel was immersed inside a temperature con- trolled bath to maintain the temperatures of study. Two platinum resistance thermometers (Pt100) inserted into the vessel were used to measure temperature and check for equality of 0021-9614/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2009.01.004 * Corresponding author. Tel.: +33 1 64 69 49 65; fax: +33 1 64 69 49 68. E-mail address: dominique.richon@ensmp.fr (D. Richon). J. Chem. Thermodynamics 41 (2009) 779–782 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct