Abstract
Based on currently available data from site measurements in the Shenhu Area of the South China Sea, methane hydrate dissociation behavior by depressurization is studied in a one-dimensional experimental apparatus. According to time variation of temperature, resistance and gas production, the hydrate dissociation process is divided into three stages: free gas release, rapid dissociation and gradual dissociation. The experimental results show that as the hydrate saturation increases the proportion of hydrate decomposed decreases in the rapid dissociation stage. The hydrate dissociation rate and the dissociation heat increase as the dissociation pressure decreases. Furthermore, the decrease of the dissociation pressure works against the secondary formation of the hydrate.
Highlights
Natural gas hydrates (NGH) are non-stoichiometric crystalline inclusion compounds, formed from the reaction between natural gas and water under a certain temperature and pressure [1]
Sea [30,31], in this work the hydrate formation and dissociation with free gas by depressurization using a one-dimensional experimental apparatus is studied to discuss the effect of initial saturation and dissociation pressure on gas production
After the temperature of the water bath is set to a predetermined temperature required for the gas hydrate synthesis, which is 9.0 °C in the current research, methane gas is injected slowly into the vessel until the pressure in the vessel reaches approximately 20 MPa, which is sufficiently higher than the equilibrium hydrate dissociation pressure in the sediment at the working temperature of 9.0 °C
Summary
Natural gas hydrates (NGH) are non-stoichiometric crystalline inclusion compounds, formed from the reaction between natural gas and water under a certain temperature and pressure [1]. The suggested methods being explored for hydrate production mainly include depressurization [5,6,7,8,9,10], thermal stimulation [11,12,13,14,15] and inhibitor injection [16,17,18,19]. Chuang et al [27] used a one-dimensional linear model suggested by Makogon to present a parametric study of natural gas production in a confined reservoir by a depressurization well. Sea [30,31], in this work the hydrate formation and dissociation with free gas by depressurization using a one-dimensional experimental apparatus is studied to discuss the effect of initial saturation and dissociation pressure on gas production
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