Phase Equilibrium of Methane Hydrates in the Presence of MgBr₂, CaBr₂, and ZnBr₂ Aqueous Solutions

Abstract

Hydrate formation in natural gas transportation pipelines and during completion and workover operations is considered to be a serious issue. CaBr 2 and ZnBr 2 salts are widely used to design high-density completion fluids for completion of oil and gas wells; however, information on the hydrate phase equilibria in the presence of these salts is missing. In this study, a threephase liquid water−hydrate−vapor (L-H-V) equilibrium conditions for methane hydrate in aqueous solutions of MgBr 2 , CaBr 2 , and ZnBr 2 at 0.1, 0.25, 0.5, 0.75, 1, 3, 5, 10, and 15 wt % in the temperature and pressure range of 276.5−285.4 K and 3.65−9.56 MPa have been reported using the isochoric pressure search method. A total of 129 phase equilibrium experiments have been performed. At low concentrations of the salt, that is, 0.1−0.75 wt %, the thermodynamic inhibition was found to be low and close to the methane hydrate equilibrium conditions in pure water. The inhibition effect is found to increase beyond 1 wt %, becomes significant after 3 wt % salt concentration, and is found to increase with an increase in the salt concentration. In accordance with the hydrated radius and ionic weight, the inhibition effect of salts on the methane hydrate phase equilibria is in the order of MgBr 2 > CaBr 2 > ZnBr 2 . The heat of dissociation (evaluated using the Clausius−Clapeyron equation) for methane hydrates in aqueous salt systems is found to be in the order of ZnBr 2 > CaBr 2 > MgBr 2 . This study will be useful to design efficient completion fluids for completion and workover operations for onshore and offshore oil and gas production operations.

Kinetics of Methane Hydrate Inhibition in MgBr2, CaBr2, and ZnBr2 Solutions

“…After the induction period, the temperature continues to increase and the pressure continues to decrease, as shown in Figure a. This means the formation of hydrate can be justified by the enclathration of CH 4 molecules in the hydrate cages, and thereby, a decrease in pressure and an increase in temperature are observed after the induction point . The final temperature and pressure at which hydrate formation stops and the system attains equilibrium are at ∼3 °C and ∼65 bars.…”

“…This work explores the kinetics of CH 4 hydrate formation in the presence of MgBr 2 , CaBr 2, and ZnBr 2 salt solutions at different concentrations such as 1, 3, 5, 10, and 15 wt %, unlike our previous work, which focused on thermodynamic studies of the same system . The moles of CH 4 consumed during hydrate formation, rate of hydrate formation, water-to-hydrate conversion (W–H), gas-to-hydrate conversion (G–H), moles of CH 4 recovered during the hydrate dissociation process, and the rate of hydrate dissociation have been studied in detail to better understand the kinetics of CH 4 hydrate formation and dissociation in the presence of MgBr 2 , CaBr 2 , and ZnBr 2 salt solutions.…”

“…The effect of salts like MgCl 2 , NaCl, KCl, and CaCl 2 at various concentrations on the phase equilibrium of methane and carbon dioxide hydrates has been studied to help develop their use as inhibitors. − Researchers have also studied the effect of the combination of organic inhibitors like methanol, ethanol, and ethylene glycol with salts like NaCl, KCl, CaCl 2 , and MgCl 2 on the phase behavior of methane or carbon dioxide hydrates. ,− Metal bromides such as CaBr 2 and ZnBr 2 can be used with metal chlorides (like NaCl, KCl, and CaCl 2 ) to make high-density completion fluids that are needed for open perforation completion of oil wells while minimizing particulate contamination. , The formation of hydrates during completion and workover operations is also considered a major problem; therefore, understanding the role of bromide salts in mitigating the hydrate formation in these processes also becomes a necessity. Researchers have looked at the phase equilibrium of gas hydrates in the presence of salts like NaBr, KBr, and CaBr 2 at various concentrations and observed an inhibitory effect on hydrate formation. , In our recent work, we too have examined the phase equilibrium of methane hydrate in the presence of MgBr 2 , CaBr 2 , and ZnBr 2 solutions at various concentrations and observed that MgBr 2 is a strong hydrate inhibitor compared to CaBr 2 and ZnBr 2 …”

Effect of ions on Methane Hydrate Phase Equilibrium in Deep-Water Environment of “Haima” Cold Seep

“…The inhibition mechanism of ion categories on hydrate formation mainly stems from the dipole force on water molecules. The stronger interaction between water with salt ions interferes with the organization of the water lattice around the clathrate hydrate guest molecule and inhibits hydrate formation [8]. The strength of the salt ion-dipole bond between the cation and water molecules may correlate with the degree of inhibition of hydrate formation.…”

A Comprehensive Review on Well Completion Operations and Artificial Lift Techniques for Methane Gas Production from Natural Gas Hydrate Reservoirs

“…Therefore, continuous monitoring of trip tank, return mud and cuttings is obligatory to avoid any compelling grounds in the well. Prior to drilling the hydrate-bearing formation, inhibitors are added with the drilling fluid to make hydrate less stable and during hydrate-bearing formation penetration, mud coolers are used to maintain the hole stability by keeping the hydrate stable. , However, for enhanced production from a gas hydrate reservoir well design, placement and configuration plays a crucial role. Moreover, it also helps in maintaining the integrity of the well and helps in effective drainage of reservoir pressure .…”