Liang Can, Jia Zijian, Xiao Lizhi, Wang Guwen, Mao Yan, Ma Xiaopeng
Changzhou Institute of Technology, Changzhou, 213032, China.
University of Shanghai for Science and Technology, Shanghai, 200093, China.
Magn Reson Lett. 2023 Apr 13;3(3):266-275. doi: 10.1016/j.mrl.2023.03.010. eCollection 2023 Aug.
The wettability of reservoir rocks saturated with oil and water is one of the most important factors influencing petrophysics and oil recovery. Minerals with different wettability constitute the overall heterogeneous wettability in rocks. Variations in sample composition can be detected by nuclear magnetic resonance (NMR) measurements. In this paper, the method of using the magnetic susceptibility contrast between rock skeleton and saturated fluid to estimate wettability is proposed. The theoretical feasibility was firstly analyzed, and then the internal gradients caused by magnetic susceptibility contrasts were employed to interpret wettability alteration before and after ageing process in rocks. It was discovered that water and oil in the same pores experienced different internal gradients after ageing, which were associated with the differences in magnetic susceptibility contrasts. After that, the free induction decay measurement was performed to acquire magnetic susceptibility contrasts of artificial sandstone samples with the intermediate-wet condition. A refined NMR wettability index was presented and correlated with the Amott wettability tests. The experimental results demonstrate that the new method for determining wettability is feasible.
被油和水饱和的储层岩石的润湿性是影响岩石物理学和石油采收率的最重要因素之一。具有不同润湿性的矿物构成了岩石整体的非均一润湿性。样品成分的变化可以通过核磁共振（NMR）测量来检测。本文提出了利用岩石骨架与饱和流体之间的磁化率对比度来估算润湿性的方法。首先分析了理论可行性，然后利用由磁化率对比度引起的内部梯度来解释岩石老化前后的润湿性变化。研究发现，老化后同一孔隙中的水和油经历了不同的内部梯度，这与磁化率对比度的差异有关。之后，进行了自由感应衰减测量，以获取中间润湿性条件下人工砂岩样品的磁化率对比度。提出了一种改进的核磁共振润湿性指数，并将其与阿莫特润湿性测试相关联。实验结果表明，这种测定润湿性的新方法是可行的。
