含裂隙天然气水合物储层注热开采数值仿真

Numerical Simulation of Heat Injection Extraction in Fractured Natural Gas Hydrate Reservoir

[目的]天然气水合物是一种极具开采价值的清洁能源,但水合物开采后期热量供给不足导致产气速率较低。储层改造能够显著增加水合物储层渗透率,提高热量传递效率。基于此,对压裂改造后含裂隙水合物储层注热开采方式下产气速率的影响机理进行分析。[方法]文章以压裂改造后的水合物储层为研究对象,建立了单裂隙水合物储层注热开采的温度-渗流-化学数值模型,仿真分析不同注热温度、裂隙开度、注热速度对水合物储层产气速率的影响,并进行注热参数正交设计分析。[结果]研究表明:裂隙注热开采水合物的过程中,注热温度、注热速度、裂隙开度对产气速率的影响规律均分为3个阶段,并且注热温度越高、注热速度越大、裂隙开度越大,水合物储层产气速率越大。对注热参数正交分析发现,注热温度对峰值产气速率有显著影响,注热速度次之,裂隙开度影响程度最小。[结论]文章明确了单裂隙水合物储层注热开采产气速率影响机理,定性评价水合物开采效率,为水合物现场开采提供一定思路。

[Introduction]Natural gas hydrate is a clean energy source with great exploitation value,but the insufficient heat supply in the late stage of hydrate extraction leads to a low gas production rate.Reservoir modification can significantly increase hydrate reservoir permeability and improve heat transfer efficiency.Based on this,the effect mechanism of the gas production rate of fractured hydrate reservoirs under heat injection extraction mode after fracturing is analyzed.[Method]Hydrate reservoir after fracturing modification was taken as the research object in this paper,and a numerical model of thermo-hydro-chemical was established to simulate and analyze the effects of heat injection temperature,fracture aperture,and heat injection velocity on the gas production rate of hydrate reservoir,and then the orthogonal design of heat injection parameters was carried out.[Result]The results show that the effect of heat injection temperature,heat injection velocity,and fracture aperture on gas production rate can be divided into three stages in the process of fractured hydrate heat injection extraction,and the higher the heat injection temperature,heat injection velocity,and fracture aperture,the higher the gas production rate of hydrate reservoir.The orthogonal analysis of heat injection parameters shows that the heat injection temperature has a significant effect on the peak gas production rate,followed by heat injection velocity,and the fracture aperture has the least effect.[Conclusion]In this paper,the effect mechanism of gas production rate in heat injection extraction of a hydrate reservoir with a single fracture is clarified,and the efficiency of hydrate extraction is qualitatively evaluated,which provides some ideas for hydrate extraction in situ.