Gas Production from Methane Hydrate in a Pilot-Scale Hydrate Simulator Using the Huff and Puff Method by Experimental and Numerical Studies

Abstract

A novel three-dimensional 117.8-L pressure vessel, which is called a Pilot-Scale Hydrate Simulator (PHS), is developed to investigate the gas production performance from hydrate-bearing porous media using the huff and puff method through both experimental and numerical simulations. The methane gas and deionized water are injected into the pressure vessel to synthesize methane hydrate. The grain sizes of the quartz sand in the vessel are between 300 and 450 μm. The huff and puff stages, including the injection, the soaking, and the production, are employed for hydrate dissociation. A single vertical well at the axis of the PHS is used as the injection and production well. The whole experiment consists of 15 huff and puff cycles. The numerical simulation results agree well with the experiment. Both the experimental and numerical simulation results indicate that the injected water is mainly restricted around the well during the injection stage. The system pressure fluctuates regularly in each cycle, and the secondary hydrate is formed under the pressurization effect caused by the hot water injection in the injection stage. The gas production rate maintains approximately stable in a relatively long period. The sensitivity analysis indicates that the gas production can be enhanced with high intrinsic permeability of the deposit or by raising the temperature of the injected hot water. The mass of the water produced in each cycle has little difference and is manageable when using the huff and puff method.

Measurements of Water Permeability in Unconsolidated Porous Media with Methane Hydrate Formation

“…The volume difference between the injected and the accumulated water was about 35.0 mL, which was considered as the effective pore volume of the packed sample. Based on the quartz sand density of about 2.65 g/mL, the calculated pore volume was 34.6 mL (= 81.8-125.2/2.65), which was very close to the direct measurement result, so the porosity of the sample was determined to be 42.8%, thus matching the value used in previous studies [7,11].…”

“…Recent experimental and numerical studies have introduced various kinds of production methods for hydrate dissociation in porous sediments, such as depressurization [4][5][6][7], thermal stimulation [8,9], inhibitor injection [10], and their combinations [11,12]. The idea of producing hydrocarbons from gas hydrates through CO 2 injection has also attracted much attention as it not only can realize the use of natural gas but also may sequestrate the CO 2 as gas hydrates in sediments [13,14].…”

“…As one of the key factors that determine the production potential of the hydrate reservoir, the effective permeability k eff of each phase in the hydrate-bearing sediments reflects the ability of fluids to migrate in the porous media and also affects the heat and mass transfer rates among different phases (gas, water, hydrate, and sediment grain). Numerical studies [11,15] have shown that coarse porous media characterized by high intrinsic permeability would facilitate the hydrate dissociation, and the exploitation potential will then be more desirable. However, the k eff of the hydrate deposits may be reduced to an extremely low level when the hydrate saturation S H is high.…”

Assessment of Gas Production Potential from Hydrate Reservoir in Qilian Mountain Permafrost Using Five-Spot Horizontal Well System

“…Thus, the sensible heat of the hydrate reservoir is very limited, and pure depressurization method is not appropriate in this permafrost area [20,21]. Previous studies [14,15] have demonstrated that the gas production under depressurization could be obviously enhanced when the additional heat is supplied from outside, while pure thermal stimulation will act inefficiently if it is used alone for hydrate decomposition. Therefore, the combination of depressurization and thermal stimulation is introduced as the production method in the five-spot and two-spot well systems in this study.…”

“…In order to realize the use of the methane gas trapped in gas hydrates as a kind of energy resource, people have proposed various kinds of production techniques for gas extraction from hydrate deposits, such as depressurization [9][10][11][12], thermal stimulation [13][14][15], inhibitor injection [16,17], and CO2 replacement [18,19]. In general, depressurization is considered to be the most practical and economic method for field-scale hydrate decomposition due to its technical effectiveness and the fast propagating rate of the pressure wave [12].…”