Similarity Solution for Gas Production From Dissociating Hydrates in Geologic Media

By using the Boltzman transformation, the nonlinear partial differential equations governing multicomponent mass flow, energy transport and phase changes in a geologic system involving methane hydrate dissociation can be reduced to simpler ordinary differential equations, without resorting to simplifications or approximations that require removal of any of the nonlinearities. This capability indicates that the problem admits a similarity solution, which results in invariance of any of the parameters (e.g., pressure, temperature, phase saturations) with respect to the similarity variable r/t1/2. The similarity solution is confirmed in test problems involving gas production from hydrate deposits undergoing dissociation by depressurization and thermal stimulation. The existence of the similarity solution provides a robust estimator of the gas production potential of natural hydrate accumulations, in addition to a reliable tool for the evaluation of the validity of numerical simulators of gas hydrate behavior in porous media.