(75i) Phase Equilibrium Conditions of Methane Hydrate in Presence Aqueous Solutions of CaBr2, MgBr2 and ZnBr2

Phase equilibrium conditions of methane hydrate in
presence aqueous solutions of CaBr₂,
MgBr₂
and ZnBr₂

Dnyaneshwar R. Bhawangirkar^1,2, Jitendra S. Sangwai^2*

¹Department of Chemical Engineering, Indian Institute of
Technology Bombay, Powai, Mumbai 400076, India

²Gas Hydrate and Flow Assurance Laboratory, Petroleum
Engineering Program, Department of Ocean Engineering, Indian
Institute of Technology Madras, Chennai 600036, India

Keywords: Gas hydrates; Inhibition; Flow Assurance; High pressure
phase equilibria

ABSTRACT

Gas
hydrates form when water molecules and suitably sized gas molecules,
like methane, ethane etc. come in contact at low temperatures and
high pressures. In oil and gas industry, the formation of gas
hydrates usually occur in drilling operations, production wells and
transportation pipelines; and can cause plugging, pipeline blockages
and other operational problems. To address this issue, from a more
practical point of view, inhibitors are used so as to prevent or
delay the formation of hydrates.

Chemical
inhibitors can also help in releasing methane gas molecules trapped
in the form of hydrates deep in the ocean and in permafrost regions
by shifting the pressure temperature conditions. It is necessary to
establish a reliable experimental phase equilibrium (dissociation)
data for gas hydrates in the presence of aqueous solutions of various
inhibitors. Although experimental data has been reported in the open
literature for methane hydrate phase equilibria in the presence of
inhibitors like NaCl, KCl, CaCl₂,
MgCl₂,
ZnCl₂,
NaBr, KBr; however information on some inhibitors is still limited.
Therefore, the dissociation conditions of methane hydrate in presence
of aqueous solutions of CaBr₂,
MgBr₂,
and ZnBr₂
are measured in this study. We have used four different weight
percentages of CaBr₂,
MgBr₂,
and ZnBr₂
i.e., 1, 5, 10 and 15% such that their effect on the formation of
methane hydrates can be studied. We have used an iso-chor pressure
search method to generate the equilibrium data in the temperature and
pressure ranges of (273.6-285.6) K, and (1.5-9.5) MPa, respectively.
Results reveal that the satisfactory inhibition effect has been
observed on the methane hydrate formation, causing the change in P-T
conditions by shifting the equilibrium point to higher ranges. We
also observed that the inhibition effect is more dominant at higher
weight percentage of salts. This information will certainly help in
oil and gas industry with new hydrate dissociation data on chemical
inhibitors at various pressures, temperatures and at different
concentrations. This signifies the effectiveness and usefulness of
these salts used here in inhibiting methane hydrate formation for a
smooth operation in transportation pipelines, production wells and in
drilling operations.