大庆原油加剂前后的蜡晶分形特性研究

针对蜡晶颗粒定性描述存在的不确定性问题，探讨了蜡晶形态的定量表征方法，提出基于蜡晶体积特征的粒度分布分形模型。以大庆南三联原油和林源原油为研究对象，采用流变学测试法与影像分析技术，测试它们加剂前后的析蜡过程及粘温特性；采用NcMiVnt图像分析软件，处理试样析蜡过程中的蜡晶形态图像，确定蜡晶粒度分布分形维数；进而分析温度与流动改进剂对原油蜡晶分形特性的影响。结果表明，基于蜡晶颗粒体积特征的分形模型可定量表征蜡晶形态；两种原油加剂前后的蜡晶分形维数随温度降低而增大，其析蜡量及蜡晶颗粒数量一般随之增加，宏观表现为原油低温流动性变差；两种原油加剂后的蜡晶分形维数明显增大，而蜡晶颗粒数量大幅减少，宏观上呈现出原油低温流动性提高。

Wax Crystal Fractal Characteristics of Daqing Crude Oil Before and After Adding Flow Improver

In view of the uncertainty of qualitatively describing wax crystal particles, their quantitative characterization method is discussed, and a distribution fractal model for wax crystals based on their volume characteristics is presented. Taking Nan Sanlian and Linyuan crude oil before and after adding flow improver in Daqing Oilfield as the case, their wax precipitation process and viscosity-temperature characteristics are tested by using rheological testing methods and image analysis techniques, and the microstructures of the wax crystals during their wax crystallizing are analyzed to determine the fractal dimension based on the wax crystal size distribution by using the NcMiVnt software, and then the influence of temperature and the flow improver on wax crystal fractal characteristics is discussed. The results indicate that the distribution fractal model can quantitatively characterize the wax crystal morphologies of the crude before and after adding the flow improver, the fractal dimension, volume and number of wax crystal particles deposited from the oil increase with temperature drops, so the low-temperature flowability of the oil becomes worse. While the crude treated by the flow improver, their wax crystal fractal dimensions increase significantly, but the wax crystal particle numbers reduce substantially. As a result, the low-temperature flow ability of the oil improves obviously.