原油的变温核磁共振弛豫特性实验研究

随埋藏深度的不同,地下原油温度有很大的变化,造成其核磁共振（NMR）弛豫特性差别较大。利用2 MHz核磁共振谱分析仪器,对选取的不同粘度的脱气原油样品,测量了5种不同温度下原油样品的NMR弛豫时间。结果表明,随温度升高,同一油样的弛豫速度变缓,弛豫时间增大,弛豫时间谱有规律地右移,但横向弛豫时间T2和纵向弛豫时间T1随温度的变化速度有所不同。随粘度降低,不同油样弛豫时间谱有规律地向右移动,说明原油中长弛豫组分增多,而短弛豫组分减少,弛豫时间逐渐增大。低粘度原油的纵向弛豫时间T1和横向弛豫时间T2近似相等,且在双对数坐标系下与粘度、粘度与温度比值呈反比关系;高粘度原油的T1和T2不同,其T1/T2值随粘度与温度比值的增加而增大。

Experimental study on nuclear magnetic resonance relaxation characteristic of crude oil at variable temperature

Nuclear magnetic resonance(NMR) relaxation characteristics of crude oil change with temperature varying at different formation depth.NMR relaxation time was measured using 2 MHz NMR spectrometer at five different temperatures for selected dead oil samples.The results show that with temperature elevating,the crude oil relaxation slows down,relaxation time(T1 or T2) becomes longer,and relaxation time distributions shift to right.But the rates of change for T1 and T2 are different with temperature changing.With the viscosity of crude oil decreasing,relaxation time distributions shift to right,long relaxation components increase and short relaxation components decrease,and relaxation time becomes longer gradually.When crude oil viscosity is low,T1 approaches T2,and the inverse relation of the relaxation time and viscosity,the ratio of viscosity to temperature in double logarithmic coordinate was obtained.However,the high viscosity crude oil has different T1 and T2,T1/T2 increases with the ratio of viscosity to temperature increasing.