Experimental and modeling analyses of scaling criteria for methane hydrate dissociation in sediment by depressurization

Three high pressure reactors with different inner volumes, which are named as the Pilot-scale Hydrate Simulator (PHS), the Cubic Hydrate Simulator (CHS), and the Small Cubic Hydrate Simulator (SCHS), are applied for investigating hydrate dissociation by depressurization method. The volume of the PHS, the CHS, and the SCHS are 117.80L, 5.80L, and 0.73L, respectively. Meanwhile, the model of scaling criterion for hydrate dissociation by the depressurization method is developed as well. The scaling criteria are verified and modified by the hydrate dissociation experiments with different scales. Finally, the gas production from a field scale hydrate reservoir (FSHR) is predicted by scaling the experimental results using the modified scaling criteria. The results indicate that the ratios of gas production in the depressurizing (DP) stage are similar to the ratios of inner volume, which verify the scaling criteria in the DP stage. However, the scaling criteria for the experiments in the constant-pressure (CP) stages need to be modified by the experimental results. The correction factor is 0.89. By using the modified scaling criteria, the gas production behavior, the hydrate dissociation process, and the heat transfer process in a larger scale hydrate reservoir can be predicted. The maximum deviations between the calculated value and experimental result are less than 16%, which can be accepted. In the FSHR with the diameter of 50m and the length of 60m, the predicted results indicate that 3.74×106m3 of gas are produced in 120h (5days) during the DP stage, and 1.94×106m3 of gas are produced in 1.86×105h (7750days) during the CP stage.