泥页岩核磁共振T2谱换算孔隙半径方法

核磁共振T_2谱和压汞法毛管力曲线都是储层孔隙发育特征的数据表现。理论上,核磁共振T_2谱能够依据压汞毛管力曲线准确地转换为储层孔径分布图;但对于泥页岩储层来说,二者所反映的孔隙信息有所不同。通过比对二者形态的异同,发现二者在表征微裂缝时有差别,提出一种考虑泥页岩裂缝的方法用以确定T_2弛豫时间和孔隙半径r之间的转换关系。应用此种方法对典型样品实验结果进行分析,结果表明,对泥页岩核磁共振T_2谱进行孔隙半径转换精度有很大提高。

Method for Calculating Pore Radius Distribution in Shale reservoirs from NMR T2 Spectra

Both nuclear magnetic resonance(NMR) T₂ distribution and mercury capillary pressure curve are determined by the pore structure of the reservoirs. So, NMR T₂ spectrum can be accurately converted to a pore distribution of reservoir according to mercury capillary pressure curve in theory. In fact, core space reflected by the existence of membrane bound-water T₂ distribution is different from that reflected by capillary pressure curves when it comes to shale reservoirs. The thesis finds the difference in the microfractures extended to the surface by the comparison between mercury distribution and NMR T₂ distribution. Therefore, a method considered the microfractures extended to the surface is put out to determine the conversion coefficient from relaxation time T₂ to pore radius r , and compared with the experiment data obtained from the laboratory, the results show that the new method greatly increases the precision of the pore distribution construction using NMR T₂ distribution.