Interaction relationship analysis between heat transfer and hydrate decomposition for optimization exploitation

Abstract

Heat transfer influences hydrate decomposition. Hydrate dissociation produces water. Then, water remained in the hydrate sediment shows impact on heat transfer. Six runs of experiment with different exploitation methods and well arrangements were conducted to study the interaction relationship between heat transfer and hydrate decomposition. For water production, results show that by combination method, the wellbore heating can greatly improve the water produced outside the reactor in production stage (WPII) until the hydrate decomposition ceases. While in depressurization regime, the WPII is more easily influenced by hydrate distribution and the water produced outside the reactor in the free and mix gas stage (WPI). For heat transfer, the overall heat transfer trend is not affected by less WPII. So the decomposition was hardly impacted. On the other hand, the heat transfer promotes heat absorption by hydrates, which improves hydrate decomposition. Subsequently, the hydrate decomposition consumes heat, but it cannot prevent the rise of temperature even in depressurization. So the heat from the surrounding environment is enough for hydrate decomposition. Then, the heat absorption by hydrate decomposition (Qd) and the heat absorption rate (Rd) are quantitatively studied. Specially, the heat absorption ratio (λ) is firstly defined to show the ratio of Qd to the wellbore heating consumption (Ec). It provides a fresh attitude for optimizing exploitation according to the heat transfer. In order to save more heat and improve λ, we need to utilize the heat transfer from the ambient environment and make progress in reducing wellbore heating consumption.