海洋天然气水合物藏开采若干问题研究

文章阐述了在开采天然气水合物方面所取得的研究进展，包括天然气水合物开采模型及数值模拟，天然气水合物开采物理模拟相似准则，天然气水合物开采方法研究等。建立、完善了天然气水合物开采的数学模型，并以此为基础建立了降压开采水合物物理模拟相似准则。降压法开采单一水合物藏，在某些情况下开采能量不足会导致藏内结冰严重。对下伏气的天然气水合物藏而言，水合物能够提高产气量、延长稳产时间。结合降压和注热的优势提出了注温水-降压法联合开采方法，该方法具有稳产时间较长、稳产气速度高的特点。

Study on several problems of oceanic gas hydrate reservoir exploitation

Several fundament problems like the mathematical model and numerical simulation of gas production from natural gas hydrate reservoir, similarity principle of gas hydrate physical simulation and exploitation method of gas hydrate reservoir are researched. A mathematical model is developed to simulate the hydrate dissociation in hydrate-bearing porous medium. The model can be used to analyze the effects of the flow of multiphase fluids, the intrinsic kinetic process of hydrate dissociation, the endothermic process of hydrate dissociation, ice-water phase equilibrium, the variation of permeability, the convection and conduction on the hydrate dissociation and gas and water production. For a single gas hydrate reservoir exploited only by depressurization, the study shows that water freezing appears in the formation with the dissociation of gas hydrate under certain condition due to energy deficiency for hydrate dissociation, which can lead to blockage of flow path and stopping of gas production. For a hydrate reservoir underlain by a free gas zone exploited by depressurization, the results show that the overlying hydrate zone can supply an amount of gas to improve the output of production well and evidently prolong the lifespan of gas reservoir. The combination method of warn water flooding with depressurization is proposed, which can comprehensively utilize the advantage of thermal stimulation and depressurization. The method is characterized by a long stable gas production period with a high gas rate.