Experimental and Numerical Observations of Hydrate Reformation during Depressurization in a Core-Scale Reactor

Gas hydrate has been predicted to reform around a wellbore during depressurization-based gas production from gas hydrate bearing reservoirs. This process has an adverse effect on gas production rates and it requires time and sometimes special measures to resume gas flow to producing wells. Due to lack of applicable field data, laboratory scale experiments remain a valuable source of information to study hydrate reformation. In this work, we report laboratory experiments and Complementary numerical simulations executed to investigate the hydrate reformation phenomenon. gas production from a pressure vessel filled with hydrate bearing sand was induced by depressurization with and without heat flux through the boundaries. Hydrate decomposition was monitored with a medical X-ray CT scanner and pressure and temperature measurements: CT images of the hydrate bearing sample were processed to provide 3-dimensional data of heterogeneous porosity and phase saturations suitable for numerical simulations. In the experiments, gas hydrate refoimation was observed only in the case of no-heat supply from surroundings, a finding consistent with numerical simulation. By allowing gas production on either side of the core, numerical simulations showed that initial hydrate distribution patterns affect gas distribution and flow inside the sample.This a direct consequence of the heterogeneous pore network resulting in varying hydraulic properties of the hydrate bearing sediment