页岩气藏分段压裂水平井产能分析

页岩气是主要以游离态和吸附态赋存于泥页岩系统中的非常规天然气资源,游离气和吸附气含量是影响页岩气藏水平井产能的关键因素。为了研究游离气和吸附气含量对水平井产能的影响,对含气量确定方法和影响因素进行了综述。在此基础上,利用Eclipse双孔介质和对数间距网格加密方法建立了页岩气藏水平井地质模型。设计5套不同游离气和吸附气含量方案进行模拟计算,将水平井日产气量、累积产气量、游离气和吸附气日产气量、游离气和吸附气采出程度、地层压力分布进行对比分析,明确了页岩气藏游离气和吸附气含量对水平井产能的影响。研究结果表明:随游离气含量增加和吸附气含量降低,水平井日产气量和累积产气量逐渐增加;水平井初期产气量主要由游离气贡献,吸附气主要在气井投产的中后期产出;游离气采出程度远高于吸附气的采出程度,高游离气含量是页岩气藏获得高产的重要前提。

Multi-Stage Fracturing Horizontal Well Productivity Analysis in Shale Gas Reservoir

Shale gas is a kind of unconventional gas resource stored in free and adsorbed states in the organic-rich shale system. The horizontal well productivity is mainly controlled by the free gas and adsorbed gas ratios. The measurements and influencing factors were detailedly reviewed and the dual-porosity of Eclipse and logarithmically-spaced grid refinement method was used to establish a shale gas horizontal well geologic model. Five cases with different free gas and adsorbed gas ratios were designed and simulated to analyze the horizontal well productivity. The horizontal well gas production, cumulative gas production, free gas and adsorbed gas production, free gas and adsorbed gas recovery factors, formation pressure distributions were provided. The research shows that with the increase of free gas ration and the decrease of adsorbed gas ration, the horizontal well daily gas production and cumulative gas production increase. Almost all the gas produced in initial stage is free gas and adsorbed gas is mainly produced in the middle and late stages. The free gas recovery factor is relative higher than that of adsorbed gas. High daily production and cumulative production can be gained with a large free gas ration in the development of shale gas reservoir.