Large Scale Experimental Investigation on Influences of Reservoir Temperature and Production Pressure on Gas Production from Methane Hydrate in Sandy Sediment

摘要

The Pilot-Scale Hydrate Simulator (PHS), a three-dimensional 117.8 L pressure vessel, was applied to study the methane hydrate dissociation with different reservoir temperatures and different production pressures in the sandy sediment. The volume of the vessel is big enough to simulate the field-scale gas production from hydrate reservoir. The depressurization method and the depressurization assisted with heat stimulation method were performed as the hydrate dissociation methods. Three different temperatures, which are 4.7 degrees C, 8.8 degrees C, and 13.0 degrees C, were selected as the reservoir temperatures. The range of temperature in this work is the most common temperatures of hydrate reservoir in the ocean sediment. The experimental results indicate that, for the depressurization method, the temperature drop in the reservoir during hydrate dissociation is the key factor for the amount of hydrate dissociation in the depressurization (DP) stage and the rates of hydrate dissociation in the constant pressure (CP) stage, which can be enhanced by the increase of the temperature drop. With the same production pressure, rate of hydrate dissociation in the experiment with higher reservoir temperature is quicker. With a same pressure drop below hydrate dissociation pressure, the rate of hydrate dissociation in the experiment with the lower reservoir temperature is quicker. For the depressurization assisted with heat stimulation method, the hydrate dissociation rate in the heat stimulation (HS) stage mainly depends on the temperature difference between the injection temperature and the hydrate dissociation temperature corresponding to the production pressure. The larger temperature difference causes the larger hydrate dissociation rate in the HS stage. In addition, the effect of reservoir temperature on the rate of hydrate dissociation is smaller than that of production pressure in the HS stage.