中文摘要：

为了深入认识页岩气形成过程及纳米油气资源，通过对页岩气藏成藏机理及水力压裂的理论研究，提出了无形圈闭的概念。页岩气最有利的聚集部位是无形圈闭，它的形成与构造应力、区域构造背景及岩石性质密切相关。在构造应力的作用下，页岩层及低渗透砂岩层未发生明显形变，仅在岩层内部产生破裂，形成构造裂缝，其中张开度在微米级以上且相互连通的裂缝和孔隙可作为储集空间形成油气藏。页岩气藏是浮力在微米级以上孔隙中作用的结果，纳米孔隙不连通，不能聚集成藏，并且无法压裂改造。非常规油气藏的聚集原理与常规油气藏相同，油气在储层孔隙中聚集的动力都是流体密度差产生的浮力。

英文摘要：

For an in-depth understanding of shale gas generating process and nano-hydrocarbon resources, the concept of the invisible trap is pointed out through the theoretical research on the gas accumulation mechanism and hy- draulic fracturing. The trap is the most favorable enriched position for the gas and results closely from the tectonic stress, regional structural background and petrological properties. By the action of the tectonic stress, the strata of the shale and low permeability sandstone have no significant deformation and only structural fractures are produced. The oil and gas reservoir is accumulated in the formed interconnected fractures and pores above the micro-size opening. The shale gas reservoir is generated from the action of the buoyancy on the above pores ; on the contrary, the nano pores is not connected and unable to accumulate into reservoir and is no need to fracture. There are no essential differences in the accumulating mechanism between the shale gas reservoir and conventional oil and gas reservoir. The power of the oil and gas enrichment in the reservoir pores is the buoyance generated from the density differential of the liquids.