基于核磁共振的脆硬性泥页岩水化损伤演化研究

为研究脆硬性泥页岩水化后细观结构的损伤演化特征,利用核磁共振技术对不同浸泡时间的脆硬性泥页岩试样进行测量,得到不同浸泡时间的试样质量变化、横向弛豫时间T2谱分布以及核磁共振成像。结果表明:水化作用会对岩石内部产生损伤,岩样吸水率在最初的8 h内变化相对较大,1 d后相对接近稳定,之后变化不明显。随着浸泡时间的延长,微裂缝在水化的作用下快速扩展、贯通使岩样表面产生明显裂纹。核磁共振T2谱图和成像结果表明,水化作用使岩样微观结构重新分布,T2曲线信号幅度发生明显的变化,并随着浸泡时间的延长而增加。整个水化损伤分为3个阶段:大尺寸孔隙裂纹发展阶段;小孔隙产生、大尺寸孔隙裂纹加剧扩展;小孔隙加剧产生扩展、大尺寸孔隙裂纹归并贯通至水化破坏阶段。核磁共振图像显示同一块岩样在不同浸泡时间的内部微观结构分布,动态地显示岩石的水化损伤过程。

NMR technology based hydration damage evolution of hard brittle shale

This paper studies the meso-damage evolution of the structure of the brittle shale after hydration. Hard brittle shale samples at different soaking times are measured with the nuclear magnetic resonance (NMR) technique. The quality of the sample, transverse relaxation time T2 spectrum distribution and nuclear magnetic resonance imaging of the hard brittle shale samples at different soaking times are obtained. The results show that hydration can produce damage inside the rock. The water absorption of the samples changes a lot in the first eight hours and shows no obvious change after one day. The microcrack propagates rapidly and the surface cracks are formed as the soaking time increases. NMR image shows that the internal microstructure of the sample redistributes under hydration effect. T2 signal amplitude curve changes significantly as the soaking time increases. The hydration damage process is divided into three stages: the development stage of the large size pore cracks, the formation of the small pores and the propagation of the large size pore cracks, the propagation of the small size pores and the formation of the large size pore through cracks. NMR image shows the internal microstructure of the same sample at different soaking times. The hydration damage process of rocks is shown dynamically.