受原油黏度影响的鄂尔多斯盆地油湿和水湿砂岩导电响应规律

为了明确原油黏度对油湿和水湿砂岩储层的电性影响规律和机理，选用鄂尔多斯盆地长庆油田原油(黏度约为90 mPa·s)和煤油配置原油(黏度约为1 mPa·s),针对油湿和水湿的中—低渗透延长组砂岩开展了岩电、核磁共振、扫描电镜等对比实验，从岩石物理角度探索了不同黏度原油对油湿和水湿砂岩导电响应规律的影响机理。研究结果表明：(1)不论原油黏度高低，相同饱和度下油湿岩心电阻率都明显高于水湿岩心；(2)原油黏度对水湿岩心的岩电响应特征影响较小，但对油湿岩心影响很大，即油湿岩心的电性曲线呈明显的分段特征，且原油黏度越大，分段性越明显；(3)造成油湿岩心电性差异的主要原因在于高黏度原油对孔隙结构的叠加影响。研究成果对于油湿储层的油层识别和饱和度模型建立具有一定指导意义。在实际的岩石物理实验中，要注意原油黏度对油湿岩心岩电响应规律的影响，选取与地下原油黏度相近的油品进行实验才能得到具有代表性的结果。

Conductive response law of oil-wet and water-wet sandstone in Ordos Basin under the influence of oil viscosity

To clarify the influence law and mechanism of crude oil viscosity on the electrical properties of oil-wet and water-wet sandstone reservoirs, the crude oil of Changqing oilfield in Ordos Basin (the viscosity is about 90 mPa ·s) and crude oil with kerosene (the viscosity is about 1 mPa ·s) were selected to carry out the contrast experiments of rock electricity, nuclear magnetic resonance, and scanning electron microscope on oil-wet and water-wet medium-to-low permeability Yanchang Formation sandstone, and the influence mechanism of the crude oil with different viscosity on the conductivity response law of oil-wet and water-wet sandstone was explored from the perspective of petrophysics. The results show as follows. (1) Regardless of the viscosity of crude oil, the resistivity of oil-wet core is significantly higher than that of water-wet core under the same saturation. (2) Crude oil viscosity has less influence on the rock electrical response characteristic of water-wet core, but has a great influence on that of oil-wet core:the electrical property curve of oil-wet core is characterized with obvious segmentation, and the greater the viscosity of crude oil, the more obvious the segmentation. (3) The main reason for the difference in electrical properties of oil-wet core is the cumulated influence of high viscosity crude oil on the pore structure. The research results are of certain guidance significance for identifying the oil-wet reservoirs and building the saturation model of oil-wet reservoirs. In the actual petrophysics experiment, attention should be paid to the influence of crude oil viscosity on the rock electrical response law of oil-wet core. The representative results can be only obtained by selecting the oil for experiment with the viscosity similar to that of the underground crude oil.