注水开发对原油性质的影响规律研究

砂岩油藏长期注水开发，注入水对储层孔隙中的原油物性有较大影响，主要表现为：随着注水开发时间的延长，原油密度、黏度、含蜡量、凝固点逐渐增大;原油黏度的变化表现出一定的阶段性，含水率在20%以下，原油黏度上升幅度较大，含水率为20%~85%时，原油黏度上升幅度比较平稳，含水率90%以上时，原油黏度上升幅度又变大；不同地区、不同层位原油性质变化特征具有明显差异；水洗前后原油性质参数之间的关系也发生变化，水洗后相同密度原油所对应的黏度明显增加，相同密度、黏度的原油所对应的凝固点明显升高。原油性质变化机理研究表明：油藏温度变化、原油轻质组分分离、脱气和注水水质是引起原油性质变化的主要原因。

RESEARCH ON THE INFLUENCE OF WATER FLOODING DEVELOPMENT ON CRUDE OIL PROPERTIES

In water flooding sandstone reservoir，injected water has large impact on crude oil properties.The density，viscosity，wax content and freezing point of crude oil gradually increase along with the time of water flooding development.The change of crude oil viscosity shows the feature in stages that the viscosity increases sharply before the stage of 20% water cut，and increases smoothly in the stage of 20% to 85% water cut，then increases rapidly after the stage of 90% water cut.The change of crude oil properties is different in different areas or layers.The relationship among crude oil properties also changes before or after water breakthrough.After water breakthrough，the viscosity of oil with the same density is larger than before，and the freezing point of oil with the same density or viscosity becomes higher than before.This study on the change mechanism of crude oil properties shows that the change of reservoir temperature，separation of light component from crude oil，degassing and injected water quality are the primary causes of the change of crude oil properties.