The consistency of the normalized hydrate dissociation rate in the hydrate simulator with different scales

Recently, in order to perform the gas production test from methane hydrate reservoir in laboratory, the size of the experimental simulator is developing towards a larger scale. The characteristics of the heat transfer and the mass transport in the hydrate-bearing sediments with different scales are varied, thereby resulting in the different hydrate dissociation behaviors. In this study, the SCHS (Small Cubic Hydrate Simulator, 0.729 L), the CHS (Cubic Hydrate Simulator, 5.832 L), and the PHS (Pilot-scale Hydrate Simulator, 117.8 L) in our laboratory were applied to study the hydrate dissociation by depressurization. The experimental results showed that, in the depressurization stage, the volume of the hydrate dissociation was determined by the sensible heat of the sediments and the heat transferred from the surroundings. During the constant pressure stage, the normalized hydrate dissociation rates (v(norm)) was first proposed to define the average rate of the hydrate dissociation per temperature and per shape factor. The v(norm) excluded the influence of the driving force of the heat transfer and the scale of the hydrate simulator on the hydrate dissociation. Therefore, for the hydrate simulator with different scales, the value of the v(norm) for different production pressures were similar. The calculated value of the v(norm) for different runs were not completely be same due to the experimental error. However, the average value of the v(norm) for different runs could be used to predicate the average hydrate dissociation rate in the hydrate simulator with other scales. For example, during the gas production from a hydrate reservoir with the same shape and double length/radius of the PHS, the average hydrate dissociation rate can be calculated as 12.44 ml/min, and the total duration time of the hydrate dissociation can be calculated as 8.58 days.

Automated summary

The study revealed that hydrate dissociation rates were similar in hydrate simulators of different scales. Normalized dissociation rates can be used to predict hydrate dissociation rates in different simulators.