致密砂岩储层启动压力与微观孔隙结构关系实验研究

Experimental Study on the Relationship between Start-Up Pressure Gradient and Microscopic Pore Structure in Tight Sandstone Reservoirs

致密砂岩储层是指储层致密(一般渗透率?3 μm2)、只能经过压裂等改造才能获得经济产量的砂岩储层,它是形成非常规油气藏的主要类型之一。与常规砂岩储层相比,其中流体的流动遵循低速非达西流动规律,即存在大小不一的启动压力梯度。本文通过实验室测得不同地区致密砂岩储层启动压力梯度,结果表明,致密砂岩储层启动压力梯度随渗透率减小而急剧增大,利用扫描电镜和压汞方法进行微观分析发现,致密砂岩孔喉急剧减小,以纳米级孔喉比例为主,说明致密砂岩储层渗流特征受复杂的微观孔隙结构所控制。

The tight sandstone reservoir refers to the reservoir density (generally permeability under 0.1 ×10?3 μm2), which can only get sandstone reservoir of economic output after fracturing modification. It is one of the main types of unconventional reservoir formed. Compared with the conventional sandstone reservoir, the flow of the fluid follows the law of non-Darcy flow at low speed. Based on the existence of different starting pressure gradients, a large number of experiments show that tight sandstone reservoir starting pressure gradient increases sharply with the decrease of the permeability. The microscopic analysis accordingly shows that tight sandstone pore throat reduces sharply. Giving priority to nanometer scale pore throat ratio, it shows that tight sandstone reservoir percolation characteristics are controlled by the complex microscopic pore structure.