Abstract
An experimental study of the dissociation of methane hydrate (MH) by hot-water injection and depressurization was carried out at the National Institute of Advanced Industrial Science and Technology (AIST). These experiments helped us understand some important aspects of MH behavior such as how temperature, pressure, and permeability change during dissociation and gas production. In order to understand the experimental results, a model of MH dissociation in a porous media was designed and implemented in a numerical simulator. In the model, we treated the MH phase as a two-component system by representing the pore space occupied by MH as a separate component. Absolute permeability and relative permeability were formulated as a function of MH saturation, porosity, and sand grain diameter and introduced into the numerical model. Using the developed numerical simulator, we attempted history matching of laboratory-scale experiments of the MH dissociation process. It was found that numerical simulator was able to reproduce temperature change, permeability characteristics, and gas production behavior associated with both MH formation and dissociation.
Highlights
Methane hydrate (MH) is an ice-like solid substance in which a water molecule structure contains embedded methane molecules under low-temperature and high-pressure conditions
MH will be a potential resource of natural gas, because vast amounts of MH reservoirs exist in marine sediments and in permafrost regions worldwide [1,2,3,4,5]
We conducted an experimental study of the MH dissociation process by hot-water injection and depressurization and studied the effect of temperature and permeability changes on gas production
Summary
Methane hydrate (MH) is an ice-like solid substance in which a water molecule structure contains embedded methane molecules under low-temperature and high-pressure conditions. We have performed laboratory-scale experiments on MH dissociation processes in porous media by hot-water injection and depressurization in order to understand several phenomena that occur during MH formation and dissociation. These include temperature and permeability changes, dissociation kinetics, and gas production behavior. Only a small permeability decrease with a gradual recovery was observed during the simultaneous injection process In this experiment, MH is formed in the pore space by injecting high-pressure methane gas into the sand column under the condition of irreducible water saturation. The numerical model consists of a three-phase fourcomponent system: gas, water, MH derived from irreducible water, and MH derived from free water
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