液氮压裂中液氮对岩石破坏的影响试验

为了研究液氮对岩石破坏的影响,在理论分析的基础上,借助核磁共振测试技术,通过测试所选取的砂岩岩样孔隙体积及孔隙结构的变化,研究液氮对干燥状态和饱和水状态岩样的破坏形式。结果表明:液氮的热力冲击作用可使干燥岩石在较短时间内产生收缩变形和孔隙体积减小,试验后红色砂岩和白色砂岩岩样的孔隙体积分别降低了8.63%和4.78%;冻结作用对饱和岩样的矿物颗粒之间胶结较弱处具有损伤破坏作用,当损伤达到一定程度后,会贯通成缝,使岩体出现断裂现象。

Experimental study on effect of liquid nitrogen on rock failure during cryogenic nitrogen fracturing

For the purpose of investigating the effect of cryogenic nitrogen on rock breaking, two kinds of sandstone samples were selected to test in laboratory. Through analyzing the change in pore volume and pore structure by nuclear magnetic resonance technique, the failure types of anhydrous and water saturated rock samples were studied. The results show that shrinkage deformation occurs and pore volume decreases in anhydrous rock samples under liquid nitrogen thermal shock. And the pore volume of red sandstone and white sandstone decrease by 8.63% and 4.78 respectively. The water-saturated samples are broken by liquid nitrogen freezing, during which obvious cracks appear. While the freezing effect will damage the weak cement between rock minerals. When the damaged zone connects with each other, obvious cracks will be formed in the rock matrix.