泥质低渗水合物降压开采特性与模型研究

Production characteristics and model of muddy hydrates with low permeability by depressurization

天然气水合物(又名可燃冰)是海底储层常见的一种非常规浅层气藏,具备泥质、低渗等特点,实现其安全高效开发具有重要现实意义。在水合物开采过程中,气体渗流及水合物分解行为都会发生动态变化,两者的复杂耦合作用决定了水合物储层的产气效率,但目前缺乏对其动态耦合预测模型的研究。因此,需要进一步分析天然气水合物储层降压开采过程中气体渗流与水合物分解行为。使用南海土在岩心夹持器内重塑了泥质低渗的水合物储层,探明了降压开采特性以及储层压力的影响,并创新性提出包含储层压力、水合物分解以及产气流量等关键指标的水合物降压开采预测模型,实现了泥质低渗水合物储层渗流与分解时空关联与高精度预测,相关系数(R2)均为99%以上。本结果可为实地优化调控降压开采水合物提供理论指导。

Natural gas hydrate(also known as flammable ice)is a common unconventional shallow gas reservoir in seabed reservoirs.It has the characteristics of mud and low permeability.Its safe and efficient development is of great practical significance.During the hydrate exploitation process,both gas seepage and hydrate dissociation behavior change dynamically,and the complex coupling of the two determines the gas production efficiency of hydrate reservoirs,but there is a lack of research on their dynamic coupling prediction models.Therefore,it is necessary to further analyze the gas seepage and hydrate dissociation behaviors during the depressurization production process of gas hydrate reservoirs.The muddy,low-permeability hydrate reservoir using South China Sea soil was remolded within a core holder.The exploitation characteristics during depressurization and the influence of reservoir pressure on gas production were explored.In addition,a prediction model for depressurization extraction that included key indexes of reservoir pressure,hydrate decomposition,and gas production flow rate was innovatively proposed.The spatial and temporal correlation between seepage and dissociation of a muddy,low-permeability hydrate reservoir was predicted with high precision.Correlation coefficients(R2)between measured and predicted values were all distributed above 99%.The results can provide theoretical guidance for the optimization and control of hydrate exploitation in the field.