砂岩样泡氘水法确定含油饱和度核磁共振实验研究

Experimental study on nuclear magnetic resonance of sandstone samples by the methods of soaking deuterium water

在岩心核磁共振测试中,目前常用于区分岩心中油水信号的实验方法,是将洗油后饱和了地层水的岩样浸泡在一定浓度的MnCl_2溶液中,一定时间后,Mn^(2+)充分扩散进入岩样孔隙内,流体中的水信号就会加速衰减直到消失,而油的信号保持不变,以此实现油、水信号的分离。然而,室内实验结果表明砂岩样浸泡低浓度氯化锰溶液实验获得的T2谱出现偏移现象,锰离子浓度过高又会在一定程度上对核磁共振测试仪磁场产生干扰,获取的油信号存在部分损失,导致砂岩岩心含油饱和度测定结果不准确。本文利用核磁共振和驱替相结合实验分析技术,研究砂岩样泡氘水法核磁共振实验效果,并建立其核磁含油饱和度实验结果分析方法,以此在降低Mn^(2+)浓度的同时,提高砂岩样含油饱和度测定的准确度。

In the core nuclear magnetic resonance test, the experimental method, which is commonly used to distinguish oil and water signals in the core,is to soak the formation water saturated rock samples in a certain concentration of MnCl2 solution at present.After a certain period of time,Mn2＋ fully diffuse into the pore of rock sample,the water signal in the fluid will accelerate the decay until it disappears, and the oil signal remains unchanged,in order to achieve oil and water signal separation.However,the experimental results show that the T2 spectra of the sandstone-like foam with low concentration of manganese chloride showed the migration phenomenon, excessive high manganese ion concentration will interfere with the magnetic field strength of the NMR tester to a certain extent, which lose oil water two phase nuclear magnetic resonance signal and result in inaccurate measurement of nuclear magnetic oil saturation.This paper adopts the combined experimental analysis techniques including nuclear magnetic and displacement phase to study the effect of sandstone-like deuterium water nuclear magnetic resonance experiment, and built experimental results analysis methods of nuclear magnetic oil saturation.This method can reduce the Mn2＋ concentration while improving the accuracy of sandstone-like magnetic oil saturation.