川南龙马溪组页岩核磁渗透率新模型研究

为了更加快速有效地进行页岩渗透率的测试,以四川盆地南部下志留统龙马溪组页岩为研究对象,进行页岩低场核磁共振和高速离心实验。以脉冲渗透率为标准,对比分析目前常用的4种岩石核磁渗透率模型的相对误差,这4种模型中只有扩展后的SDR模型相对误差较小,其他3种模型误差很大,不适用于页岩核磁渗透率的计算。为了进一步减小页岩核磁渗透率的计算误差,在SDR模型的基础上建立一种新的页岩核磁渗透率的单参数模型。结果表明,新模型相关系数可达到0.967,与脉冲渗透率的相对误差平均为18.31%,证明新模型能更准确地计算页岩的核磁渗透率,为页岩渗透率的测试提供了一种新的快速、无损、有效的实验方法。

A new nuclear magnetic resonance permeability model of shale of Longmaxi Formation in southern Sichuan Basin

In order to measure the shale permeability more effectively and quickly, 22 shale samples from Lower Silurian Longmaxi Formation in southern Sichuan Basin were collected and used in the low field nuclear magnetic resonance (NMR) and high-speed centrifugal experiments. The results show that the relative error of the four rocks NMR permeability model currently used are very large, and is small only in the extended SDR model. Therefore the four conventional NMR models are not suitable for the NMR permeability calculation of shale. In order to reduce the calculation error, a single parameter model of shale NMR permeability is set up based on the SDR model. The correlation coefficient of this new model reaches 0.967, and the average relative error of pulse decay permeability is about 18.31%. It is concluded that the new model can calculate the permeability of gas shale more accurately, which provides a fast, nondestructive and effective experimental methodology for shale permeability test.