Hydrate decomposition is an endothermic reaction. The exploitation effect is closely related to the heat transfer properties in hydrate deposits. Based on the results of experiment and simulation with depressurization (PD), depressurization combined with wellbore heating (DH) and huff and puff method (HP), this paper mainly studies the heat transfer from the boundaries (QB), the heat consumption by hydrate decomposition (QH), the heat absorption by the porous sand (QS), and the heat loss (QL) to optimize the production methods. The results show that a limited amount of QL is caused by the heat transferred to the water bath in HP. In addition, the heat transferred from the water bath can offset the QS, which is the main component of QL in HP. Thus, the best heat utilization is seen in this method. PD shows its obvious weakness in hydrate recovery duration, although it only uses the QB for hydrate decomposition. For DH, the amount of the lost heat is the largest among the three methods, and the majority of QL is caused by the heat from wellbore heating transferred to the ambient environment. Thus, the heat utilization in this method is the worst. For the optimization of the exploitation method, it is of great importance to decrease the heat transferred to the surrounding environment.
Keywords methane hydrate, huff and puff, wellbore heating, depressurization, heat transfer, heat utilization