关键词: 天然气水合物藏, 物性参数, 水合物分解, 应力敏感性, 数值模拟

Abstract:

On the basis of stress sensitivity experiments, the functional relationship between effective stress and physical parameters, including permeability, porosity and elastic modulus, was established. Meanwhile, combined with the existing models for the relationship between physical parameters of reservoirs and the hydrate saturation, a comprehensive model was established to describe dynamic variations of physical parameters of hydrate reservoirs. This model took into full account of the effect of hydrate dissociation and the influence of stress state variations in reservoirs on physical parameters. The case study on the natural gas hydrate production by decompression demonstrated that effects of hydrate dissociation and the reservoir stress sensitivity were two important influencing factors on physical parameters of hydrate reservoirs. Of which the effect of hydrate dissociation was the controlling factor that made the permeability and porosity of hydrate reservoirs in the dissociation area increase obviously and the elastic modulus decrease dramatically. The influence of the reservoir stress sensitivity occurred in the whole sweep area of pressure, and it played a certain inhibiting role on the impact of hydrate dissociation because its effect on physical parameters was contrary to that of hydrate dissociation, therefore, it should never be ignored.

Key words: gas hydrate reservoir, physical parameter, dissociation of gas hydrate, stress sensitivity, numerical simulation